May be involved in the regulation of dopamine release and transport. Induces fibrillization of microtubule-associated protein tau. Reduces neuronal responsiveness to various apoptotic stimuli, leading to a decreased caspase-3 activation.
CuratedUniProtKB
According to TCDB this is a transporter from family:
Increasing evidence suggests that alpha-synuclein is a common pathogenic molecule in several neurodegenerative diseases, particularly in Parkinson's disease. To understand alpha-synuclein pathology, we investigated molecules that interact with alpha-synuclein in human and rat brains and identified tubulin as an alpha-synuclein binding/associated protein. Tubulin co-localized with alpha-synuclein in Lewy bodies and other alpha-synuclein-positive pathological structures. Tubulin initiated and promoted alpha-synuclein fibril formation under physiological conditions in vitro. These findings suggest that an interaction between tubulin and alpha-synuclein might accelerate alpha-synuclein aggregation in diseased brains, leading to the formation of Lewy bodies.
Multiple studies implicate metals in the pathophysiology of neurodegenerative diseases. Disturbances in brain iron metabolism are linked with synucleinopathies. For example, in Parkinson's disease, iron levels are increased and magnesium levels are reduced in the brains of patients. To understand how changes in iron and magnesium might affect the pathophysiology of Parkinson's disease, we investigated binding of iron to alpha-synuclein, which accumulates in Lewy bodies. Using fluorescence of the four tyrosines in alpha-synuclein as indicators of metal-related conformational changes in alpha-synuclein, we show that iron and magnesium both interact with alpha-synuclein. alpha-Synuclein exhibits fluorescence peaks at 310 and 375 nm. Iron lowers both fluorescence peaks, while magnesium increases the fluorescence peak only at 375 nm, which suggests that magnesium affects the conformation of alpha-synuclein differently than iron. Consistent with this hypothesis, we also observe that magnesium inhibits alpha-synuclein aggregation, measured by immunoblot, cellulose acetate filtration, or thioflavine-T fluorescence. In each of these studies, iron increases alpha-synuclein aggregation, while magnesium at concentrations >0.75 mm inhibits the aggregation of alpha-synuclein induced either spontaneously or by incubation with iron. These data suggest that the conformation of alpha-synuclein can be modulated by metals, with iron promoting aggregation and magnesium inhibiting aggregation.
alpha-Synuclein is a protein normally involved in presynaptic vesicle homeostasis. It participates in the development of Parkinson's disease, in which the nerve cell lesions, Lewy bodies, accumulate alpha-synuclein filaments. The synaptic neurotransmitter release is primarily dependent on Ca(2+)-regulated processes. A microdialysis technique was applied showing that alpha-synuclein binds Ca(2+) with an IC(50) of about 2-300 microm and in a reaction uninhibited by a 50-fold excess of Mg(2+). The Ca(2+)-binding site consists of a novel C-terminally localized acidic 32-amino acid domain also present in the homologue beta-synuclein, as shown by Ca(2+) binding to truncated recombinant and synthetic alpha-synuclein peptides. Ca(2+) binding affects the functional properties of alpha-synuclein. First, the ligand binding of (125)I-labeled bovine microtubule-associated protein 1A is stimulated by Ca(2+) ions in the 1-500 microm range and is dependent on an intact Ca(2+) binding site in alpha-synuclein. Second, the Ca(2+) binding stimulates the proportion of (125)I-alpha-synuclein-containing oligomers. This suggests that Ca(2+) ions may both participate in normal alpha-synuclein functions in the nerve terminal and exercise pathological effects involved in the formation of Lewy bodies.
Parkinson's disease (PD) is the second most prevalent age-related, neurodegenerative disorder, affecting >1% of the population over the age of 60. PD pathology is marked by intracellular inclusions composed primarily of the protein α-synuclein (α-syn). These inclusions also contain copper, and the interaction of Cu(2+) with α-syn may play an important role in PD fibrillogenesis. Here we report the stoichiometry, affinity, and coordination structure of the Cu(2+)-α-syn complex. Electron paramagnetic resonance (EPR) titrations show that monomeric α-syn binds 1.0 equiv of Cu(2+) at the protein N-terminus. Next, an EPR competition technique demonstrates that α-syn binds Cu(2+) with a K(d) of ≈0.10 nM. Finally, EPR and electron spin echo modulation (ESEEM) applied to a suite of mutant and truncated α-syn constructs reveal a coordination sphere arising from the N-terminal amine, the Asp2 amide backbone and side chain carboxyl group, and the His50 imidazole. The high binding affinity identified here, in accord with previous measurements, suggests that copper uptake and sequestration may be a part of α-syn's natural function, perhaps modulating copper's redox properties. The findings further suggest that the long-range interaction between the N-terminus and His50 may have a weakening effect on the interaction of α-syn with lipid membranes, thereby mobilizing monomeric α-syn and hastening fibrillogenesis.
The aggregation of α-synuclein (α-Syn), the major component of intracellular Lewy body inclusions in dopaminergic neurons of the substantia nigra, plays a critical role in the etiology of Parkinson disease (PD). Long-term effects of redox-active transition metals (Cu, Fe) and oxidative chemical imbalance underlie the disease progression and neuronal death. In this work, we provide evidence that a brain metalloprotein, Zn₇-metallothionein-3 (Zn₇MT-3), possesses a dynamic role in controlling aberrant protein-copper interactions in PD. We examined the properties of the α-Syn-Cu(II) complex with regard to molecular oxygen, the biological reducing agent ascorbate, and the neurotransmitter dopamine. The results revealed that under aerobic conditions α-Syn-Cu(II) possesses catalytic oxidase activity. The observed metal-centered redox chemistry significantly promotes the production of hydroxyl radicals and α-Syn oxidation and oligomerization, processes considered critical for cellular toxicity. Moreover, we show that Zn₇MT-3, through Cu(II) removal from the α-Syn-Cu(II) complex, efficiently prevents its deleterious redox activity. We demonstrate that the Cu(II) reduction by thiolate ligands of Zn₇MT-3 and the formation of Cu(I)₄Zn₄MT-3, in which an unusual oxygen-stable Cu(I)₄-thiolate cluster is present, comprise the underlying molecular mechanism by which α-Syn and dopamine oxidation, α-Syn oligomerization, and ROS production are abolished. These studies provide new insights into the bioinorganic chemistry of PD.
Recent works suggest that alpha-synuclein could play a central role in Parkinson's disease (PD). Thus, two mutations were reported to be associated with rare autosomal dominant forms of the disease. We examined whether alpha-synuclein could modulate the caspase-mediated response and vulnerability of murine neurons in response to various apoptotic stimuli. We established TSM1 neuronal cell lines overexpressing wild-type (wt) alpha-synuclein or the PD-related Ala-53 --> Thr mutant alpha-synuclein. Under basal conditions, acetyl-Asp-Glu-Val-Asp-aldehyde-sensitive caspase activity appears significantly lower in wt alpha-synuclein-expressing cells than in neurons expressing the mutant. Interestingly, wt alpha-synuclein drastically reduces the caspase activation of TSM1 neurons upon three distinct apoptotic stimuli including staurosporine, etoposide, and ceramide C(2) when compared with mock-transfected cells. This inhibitory control of the caspase response triggered by apoptotic agents was abolished by the PD-related pathogenic mutation. Comparison of wild-type and mutated alpha-synuclein-expressing cells also indicates that the former exhibits much less vulnerability in response to staurosporine and etoposide as measured by the sodium 3'-[1-(phenylaminocarbonyl)-3, 4-tetrazolium]-bis(4-methoxy-6-nitro)benzenesulfonic acid assay. Altogether, our study indicates that wild-type alpha-synuclein exerts an antiapoptotic effect in neurons that appears to be abolished by the Parkinson's disease-related mutation, thereby suggesting a possible mechanism underlying both sporadic and familial forms of this neurodegenerative disease.
Tau and alpha-synuclein are both proteins implicated in the pathology of neurodegenerative disease. Here we have investigated the mechanisms of axonal transport of tau and alpha-synuclein, because failure of axonal transport has been implicated in the development of several neurodegenerative disorders. We found that the transport of both of these proteins depend on an intact microtubule- but not actin-cytoskeleton, and that tau and alpha-synuclein both move at overall slow rates of transport. We used time-lapse video microscopy to obtain images of live neurons that had been transfected with plasmids expressing proteins tagged with enhanced green fluorescent protein. We found that particulate structures containing tau or alpha-synuclein travel rapidly when moving along axons but spend the majority of the time paused, and these structures have similar characteristics to those previously observed for neurofilaments. The motile particles containing tau or alpha-synuclein colocalise with the fast-transporting molecular motor kinesin-1 in neurons. Co-immunoprecipitation experiments demonstrate that tau and alpha-synuclein are each associated with complexes containing kinesin-1, whereas only alpha-synuclein appears to interact with dynein-containing complexes. In vitro glutathione S-transferase-binding assays using rat brain homogenate or recombinant protein as bait reveals a direct interaction of kinesin-1 light chains 1 and 2 with tau, but not with alpha-synuclein. Our findings suggest that the axonal transport of tau occurs via a mechanism utilising fast transport motors, including the kinesin family of proteins, and that alpha-synuclein transport in neurons may involve both kinesin and dynein motor proteins.
Interacting selectively and non-covalently with fatty acids, aliphatic monocarboxylic acids liberated from naturally occurring fats and oils by hydrolysis.
Negative evidence
1:
Inferred from Direct AssayUniProtKB
alpha-Synuclein (alphaS) is an amyloidogenic neuronal protein associated with several neurodegenerative disorders. Although unstructured in solution, alphaS forms alpha-helices in the presence of negatively charged lipid surfaces. Moreover, alphaS was shown to interact with FAs in a manner that promotes protein aggregation. Here, we investigate whether alphaS has specific FA binding site(s) similar to fatty acid binding proteins (FABPs), such as the intracellular FABPs. Our NMR experiments reveal that FA addition results in i) the simultaneous loss of alphaS signal in both (1)H and (13)C spectra and ii) the appearance of a very broad FA (13)C-carboxyl signal. These data exclude high-affinity binding of FA molecules to specific alphaS sites, as in FABPs. One possible mode of binding was revealed by electron microscopy studies of oleic acid bilayers at pH 7.8; these high-molecular-weight FA aggregates possess a net negative surface charge because they contain FA anions, and they were easily disrupted to form smaller particles in the presence of alphaS, indicating a direct protein-lipid interaction. We conclude that alphaS is not likely to act as an intracellular FA carrier. Binding to negatively charged membranes, however, appears to be an intrinsic property of alphaS that is most likely related to its physiological role(s) in the cell.
Multiple studies implicate metals in the pathophysiology of neurodegenerative diseases. Disturbances in brain iron metabolism are linked with synucleinopathies. For example, in Parkinson's disease, iron levels are increased and magnesium levels are reduced in the brains of patients. To understand how changes in iron and magnesium might affect the pathophysiology of Parkinson's disease, we investigated binding of iron to alpha-synuclein, which accumulates in Lewy bodies. Using fluorescence of the four tyrosines in alpha-synuclein as indicators of metal-related conformational changes in alpha-synuclein, we show that iron and magnesium both interact with alpha-synuclein. alpha-Synuclein exhibits fluorescence peaks at 310 and 375 nm. Iron lowers both fluorescence peaks, while magnesium increases the fluorescence peak only at 375 nm, which suggests that magnesium affects the conformation of alpha-synuclein differently than iron. Consistent with this hypothesis, we also observe that magnesium inhibits alpha-synuclein aggregation, measured by immunoblot, cellulose acetate filtration, or thioflavine-T fluorescence. In each of these studies, iron increases alpha-synuclein aggregation, while magnesium at concentrations >0.75 mm inhibits the aggregation of alpha-synuclein induced either spontaneously or by incubation with iron. These data suggest that the conformation of alpha-synuclein can be modulated by metals, with iron promoting aggregation and magnesium inhibiting aggregation.
Interacting selectively and non-covalently with a histone, any of a group of water-soluble proteins found in association with the DNA of plant and animal chromosomes. They are involved in the condensation and coiling of chromosomes during cell division and have also been implicated in nonspecific suppression of gene activity.
Alpha-synuclein is a neuronal protein implicated genetically in Parkinson's disease. alpha-synuclein localizes to the nucleus and presynaptic nerve terminals. Here we show that alpha-synuclein mediates neurotoxicity in the nucleus. Targeting of alpha-synuclein to the nucleus promotes toxicity, whereas cytoplasmic sequestration is protective in both cell culture and transgenic Drosophila. Toxicity of alpha-synuclein can be rescued by administration of histone deacetylase inhibitors in both cell culture and transgenic flies. Alpha-synuclein binds directly to histones, reduces the level of acetylated histone H3 in cultured cells and inhibits acetylation in histone acetyltransferase assays. Alpha-synuclein mutations that cause familial Parkinson's disease, A30P and A53T, exhibit increased nuclear targeting in cell culture. These findings implicate nuclear alpha-synuclein in promoting nigrostriatal degeneration in Parkinson's disease and encourage exploration of histone deacetylase inhibitors as potential therapies for the disorder.
Molecular chaperones of the heat shock protein 70 (Hsp70) family counteract protein misfolding in a variety of neurodegenerative disease models. To determine whether human Hsp70 exerts similar effects on the aggregation of alpha-synuclein (alpha-Syn), the key component of insoluble fibrils present in Parkinson's disease, we investigated alpha-Syn fibril assembly in the presence of Hsp70. We found in vitro assembly was efficiently inhibited by substoichiometric concentrations of purified Hsp70 in the absence of cofactors. Experiments using alpha-Syn deletion mutants indicated that interactions between the Hsp70 substrate binding domain and the alpha-Syn core hydrophobic region underlie assembly inhibition. This assembly process was inhibited prior to the elongation stage as we failed to detect any fibrils by electron microscopy. In addition, fluorescence polarization and binding assays suggest that Hsp70 recognizes soluble alpha-Syn species in a highly dynamic and reversible manner. Together, these results provide novel insights into how Hsp70 suppresses alpha-Syn aggregation. Furthermore, our findings suggest that this critical step in Parkinson's disease pathogenesis may be subject to modulation by a common molecular chaperone.
Mutations and copy number variation in the SNCA gene encoding the neuronal protein alpha-synuclein have been linked to familial Parkinson disease (Thomas, B., and Beal, M. F. (2007) Parkinson's disease. Hum. Mol. Genet. 16, R183-R194). The carboxyl terminus of alpha-synuclein can be phosphorylated at tyrosine 125 and serine 129, although only a small fraction of the protein is phosphorylated under normal conditions (Okochi, M., Walter, J., Koyama, A., Nakajo, S., Baba, M., Iwatsubo, T., Meijer, L., Kahle, P. J., and Haass, C. (2000) Constitutive phosphorylation of the Parkinson's disease associated alpha-synuclein. J. Biol. Chem. 275, 390-397). Under pathological conditions, such as in Parkinson disease, alpha-synuclein is a major component of Lewy bodies, a pathological hallmark of Parkinson disease, and is mostly phosphorylated at Ser-129 (Anderson, J. P., Walker, D. E., Goldstein, J. M., de Laat, R., Banducci, K., Caccavello, R. J., Barbour, R., Huang, J. P., Kling, K., Lee, M., Diep, L., Keim, P. S., Shen, X. F., Chataway, T., Schlossmacher, M. G., Seubert, P., Schenk, D., Sinha, S., Gai, W. P., and Chilcote, T. J. (2006) Phosphorylation of Ser-129 is the dominant pathological modification of alpha-synuclein in familial and sporadic Lewy body disease. J. Biol. Chem. 281, 29739-29752). Controversy exists over the extent to which phosphorylation of alpha-synuclein and/or the visible protein aggregation in Lewy bodies are steps in disease pathogenesis, are protective, or are neutral markers for the disease process. Here we used the combination of peptide pulldown assays and mass spectrometry to identify and compare protein-protein interactions of phosphorylated and non-phosphorylated alpha-synuclein. We showed that non-phosphorylated alpha-synuclein carboxyl terminus pulled down protein complexes that were highly enriched for mitochondrial electron transport proteins, whereas alpha-synuclein carboxyl terminus phosphorylated on either Ser-129 or Tyr-125 did not. Instead the set of proteins pulled down by phosphorylated alpha-synuclein was highly enriched in certain cytoskeletal proteins, in vesicular trafficking proteins, and in a small number of enzymes involved in protein serine phosphorylation. This targeted comparative proteomics approach for unbiased identification of protein-protein interactions suggests that there are functional consequences when alpha-synuclein is phosphorylated.
Evidence
2:
Inferred from Physical InteractionIntAct
alpha-Synuclein is the major constituent of Lewy bodies, a pathological signature of Parkinson disease, found in the degenerating dopaminergic neurons of the substantia nigra pars compacta. Amyloidosis generating the insoluble fibrillar protein deposition has been considered to be responsible for the cell death observed in the neurodegenerative disorder. In order to develop a controlling strategy toward the amyloid formation, 1,1'-(1,10-decanediyl)-bis-[4-a-mino-2-methylquinolinium] (dequalinium), was selected and examined in terms of its specific molecular interaction with alpha-synuclein. The protein was self-oligomerized by dequalinium, which gave rise to the ladder formation on N-[2-hydroxy-1,1-bis(hydroxymethyl)ethyl]glycine/SDS-PAGE in the presence of a coupling reagent of N-(ethoxycarbonyl)-2-ethoxy-1,2-dihydroquinoline. The double-headed structure of dequalinium with the two cationic 4-aminoquinaldinium rings was demonstrated to be critical for the protein self-oligomerization. The dequalinium-binding site was located on the acidic C-terminal region of the protein with an approximate dissociation constant of 5.5 mum. The protein self-oligomerization induced by the compound has resulted in the protofibril formation of alpha-synuclein before it has developed into amyloids. The protofibrils were demonstrated to affect the membrane intactness of liposomes, and they have also been shown to influence cell viability of human neuroblastoma cells. In addition, dequalinium treatment of the alpha-synuclein-overexpressing cells exerted a significant cell death. Therefore, it is pertinent to consider that dequalinium could be used as a molecular probe to assess toxic mechanisms related to the amyloid formation of alpha-synuclein. Ultimately, the compound could be employed to develop therapeutic and preventive strategies toward alpha-synucleinopathies including Parkinson disease.
Interacting selectively and non-covalently and stoichiometrically with kinesin, a member of a superfamily of microtubule-based motor proteins that perform force-generating tasks such as organelle transport and chromosome segregation.
Evidence
1:
Inferred from Physical InteractionUniProtKB
Tau and alpha-synuclein are both proteins implicated in the pathology of neurodegenerative disease. Here we have investigated the mechanisms of axonal transport of tau and alpha-synuclein, because failure of axonal transport has been implicated in the development of several neurodegenerative disorders. We found that the transport of both of these proteins depend on an intact microtubule- but not actin-cytoskeleton, and that tau and alpha-synuclein both move at overall slow rates of transport. We used time-lapse video microscopy to obtain images of live neurons that had been transfected with plasmids expressing proteins tagged with enhanced green fluorescent protein. We found that particulate structures containing tau or alpha-synuclein travel rapidly when moving along axons but spend the majority of the time paused, and these structures have similar characteristics to those previously observed for neurofilaments. The motile particles containing tau or alpha-synuclein colocalise with the fast-transporting molecular motor kinesin-1 in neurons. Co-immunoprecipitation experiments demonstrate that tau and alpha-synuclein are each associated with complexes containing kinesin-1, whereas only alpha-synuclein appears to interact with dynein-containing complexes. In vitro glutathione S-transferase-binding assays using rat brain homogenate or recombinant protein as bait reveals a direct interaction of kinesin-1 light chains 1 and 2 with tau, but not with alpha-synuclein. Our findings suggest that the axonal transport of tau occurs via a mechanism utilising fast transport motors, including the kinesin family of proteins, and that alpha-synuclein transport in neurons may involve both kinesin and dynein motor proteins.
Multiple studies implicate metals in the pathophysiology of neurodegenerative diseases. Disturbances in brain iron metabolism are linked with synucleinopathies. For example, in Parkinson's disease, iron levels are increased and magnesium levels are reduced in the brains of patients. To understand how changes in iron and magnesium might affect the pathophysiology of Parkinson's disease, we investigated binding of iron to alpha-synuclein, which accumulates in Lewy bodies. Using fluorescence of the four tyrosines in alpha-synuclein as indicators of metal-related conformational changes in alpha-synuclein, we show that iron and magnesium both interact with alpha-synuclein. alpha-Synuclein exhibits fluorescence peaks at 310 and 375 nm. Iron lowers both fluorescence peaks, while magnesium increases the fluorescence peak only at 375 nm, which suggests that magnesium affects the conformation of alpha-synuclein differently than iron. Consistent with this hypothesis, we also observe that magnesium inhibits alpha-synuclein aggregation, measured by immunoblot, cellulose acetate filtration, or thioflavine-T fluorescence. In each of these studies, iron increases alpha-synuclein aggregation, while magnesium at concentrations >0.75 mm inhibits the aggregation of alpha-synuclein induced either spontaneously or by incubation with iron. These data suggest that the conformation of alpha-synuclein can be modulated by metals, with iron promoting aggregation and magnesium inhibiting aggregation.
Catalysis of an oxidation-reduction (redox) reaction, a reversible chemical reaction in which the oxidation state of an atom or atoms within a molecule is altered. One substrate acts as a hydrogen or electron donor and becomes oxidized, while the other acts as hydrogen or electron acceptor and becomes reduced.
The aggregation of α-synuclein (α-Syn), the major component of intracellular Lewy body inclusions in dopaminergic neurons of the substantia nigra, plays a critical role in the etiology of Parkinson disease (PD). Long-term effects of redox-active transition metals (Cu, Fe) and oxidative chemical imbalance underlie the disease progression and neuronal death. In this work, we provide evidence that a brain metalloprotein, Zn₇-metallothionein-3 (Zn₇MT-3), possesses a dynamic role in controlling aberrant protein-copper interactions in PD. We examined the properties of the α-Syn-Cu(II) complex with regard to molecular oxygen, the biological reducing agent ascorbate, and the neurotransmitter dopamine. The results revealed that under aerobic conditions α-Syn-Cu(II) possesses catalytic oxidase activity. The observed metal-centered redox chemistry significantly promotes the production of hydroxyl radicals and α-Syn oxidation and oligomerization, processes considered critical for cellular toxicity. Moreover, we show that Zn₇MT-3, through Cu(II) removal from the α-Syn-Cu(II) complex, efficiently prevents its deleterious redox activity. We demonstrate that the Cu(II) reduction by thiolate ligands of Zn₇MT-3 and the formation of Cu(I)₄Zn₄MT-3, in which an unusual oxygen-stable Cu(I)₄-thiolate cluster is present, comprise the underlying molecular mechanism by which α-Syn and dopamine oxidation, α-Syn oligomerization, and ROS production are abolished. These studies provide new insights into the bioinorganic chemistry of PD.
Stops, prevents or reduces the activity of a phospholipase D, an enzyme that catalyzes the reaction: a phosphatidylcholine + H2O = choline + a phosphatidate.
Negative evidence
1:
Inferred from Direct AssayUniProtKB
Alpha-synuclein (alphaSyn) is a small cytosolic protein of unknown function, which is highly enriched in the brain. It is genetically linked to Parkinson's disease (PD) in that missense mutations or multiplication of the gene encoding alphaSyn causes early onset familial PD. Furthermore, the neuropathological hallmarks of both sporadic and familial PD, Lewy bodies and Lewy neurites, contain insoluble aggregates of alphaSyn. Several studies have reported evidence that alphaSyn can inhibit phospholipase D (PLD), which hydrolyzes phosphatidylcholine to form phosphatidic acid and choline. Although various hypotheses exist regarding the roles of alphaSyn in health and disease, no other specific biochemical function for this protein has been reported to date. Because PLD inhibition could represent an important function of alphaSyn, we sought to extend existing reports on this interaction. Using purified proteins, we tested the ability of alphaSyn to inhibit PLD activity in cell-free assays. We also examined several cell lines and transfection conditions to assess whether alphaSyn inhibits endogenous or overexpressed PLD in cultured mammalian cells. In yeast, we extended our previous report of an interaction between alphaSyn and PLD-dependent phenotypes, for which PLD activity is absolutely necessary. Despite testing a range of experimental conditions, including those previously published, we observed no significant inhibition of PLD by alphaSyn in any of these systems. We propose that the previously reported effects of alphaSyn on PLD activity could be due to increased endoplasmic reticulum-related stress associated with alphaSyn overexpression in cells, but are not likely due to a specific and direct interaction between alphaSyn and PLD.
In Parkinson disease (PD) brain, a progressive loss of dopaminergic neurons leads to dopamine depletion in the striatum and reduced motor function. Lewy bodies, the characteristic neuropathological lesions found in the brain of PD patients, are composed mainly of α-synuclein protein. Three point mutations in the α-synuclein gene are associated with familial PD. In addition, genome-wide association studies indicate that α-synuclein and Tau protein synergistically increase disease susceptibility in the human population. To determine the mechanism by which α-synuclein and Tau act together, we have used PD-causing neurotoxin MPTP and pathogenic α-synuclein mutants A30P, E46K, and A53T as models. We found that exposure of human neuroblastoma M17 cells to MPTP enhances the intracellular α-synuclein protein level, stimulates Tau protein phosphorylation at Ser(262), and induces apoptosis. In mouse brain, ablation of α-synuclein function significantly suppresses Tau phosphorylation at Ser(262). In vitro, α-synuclein binds to phosphorylated Ser(214) of Tau and stimulates PKA-catalyzed Tau phosphorylation at Ser(262). PD-associated α-synuclein mutations increase α-synuclein binding to Tau and stimulate Tau phosphorylation at Ser(262). In HEK-293 cells, α-synuclein and its all PD-associated mutants destabilize the microtubule cytoskeleton in a similar extent. In contrast, when co-expressed with Tau, these PD-associated mutants destabilize microtubules with significantly higher potency than WT. Our results demonstrate that α-synuclein is an in vivo regulator of Tau protein phosphorylation at Ser(262) and suggest that PD-associated risk factors such as environmental toxins and α-synuclein mutations promote Tau phosphorylation at Ser(262), causing microtubule instability, which leads to loss of dopaminergic neurons in PD brain.
Interacting selectively and non-covalently with any protein or protein complex (a complex of two or more proteins that may include other nonprotein molecules).
Evidence
1:
Inferred from Physical InteractionUniProtKB
Alpha-synuclein is the major component of Lewy bodies in patients with Parkinson's disease, and mutations in the alpha-synuclein gene are responsible for some familial forms of the disease. alpha-Synuclein is enriched in the presynapse, but its synaptic targets are unknown. Synphilin-1 associates in vivo with alpha-synuclein promoting the formation of intracellular inclusions. Additionally synphilin-1 has been found to be an intrinsic component of Lewy bodies in patients with Parkinson's disease. To understand the role of synphilin-1 in Parkinson's disease, we sought to define its localization and function in the brain. We now report that, like alpha-synuclein, synphilin-1 was enriched in neurons. In young rats, synphilin-1 was prominent in neuronal cell bodies but gradually migrated to neuropil during development. Immunoelectron microscopy of adult rat cerebral cortex demonstrated that synphilin-1 was highly enriched in presynaptic nerve terminals. Synphilin-1 co-immunoprecipitated with synaptic vesicles, indicating a strong association with these structures. In vitro binding experiments demonstrated that the N terminus of synphilin-1 robustly associated with synaptic vesicles and that this association was resistant to high salt washing but was abolished by inclusion of alpha-synuclein in the incubation medium. Our data indicated that synphilin-1 is a synaptic partner of alpha-synuclein, and it may mediate synaptic roles attributed to alpha-synuclein.
Erratum in:
J Biol Chem 277(37), 34651-4 (2002 Sep 13)
Evidence
2:
Inferred from Physical InteractionBHF-UCL
J. Neurosci. 22, 3090-3099 (2002)[Full text:20026307][PubMed:11943812]
The alpha-synuclein gene is implicated in the pathogenesis of Parkinson's disease. Although alpha-synuclein function is uncertain, the protein has homology to the chaperone molecule 14-3-3. In addition, alpha-synuclein can bind to 14-3-3, and both alpha-synuclein and 14-3-3 bind to many of the same proteins. Because 14-3-3 binds to and activates tyrosine hydroxylase, the rate-limiting enzyme in dopamine (DA) biosynthesis, we explored whether alpha-synuclein also bound to tyrosine hydroxylase and influenced its activity. Immunoprecipitation revealed an interaction between alpha-synuclein and tyrosine hydroxylase in brain homogenates and MN9D dopaminergic cells. Colocalization of alpha-synuclein with tyrosine hydroxylase was confirmed by immunoelectron microscopy. To explore the consequences of the interaction, we measured the effect of recombinant alpha-synuclein on tyrosine hydroxylase activity in a cell-free system and observed a dose-dependent inhibition of tyrosine hydroxylase by alpha-synuclein. To measure the impact of alpha-synuclein on tyrosine hydroxylase in dopaminergic cells, we stably transfected MN9D cells with wild-type or A53T mutant alpha-synuclein. Overexpression of wild-type or A53T mutant alpha-synuclein did not significantly alter tyrosine hydroxylase protein levels in our stably transfected cells. However, overexpressing cell lines had significantly reduced tyrosine hydroxylase activity and a corresponding reduction in dopamine synthesis. The reduction in cellular dopamine levels was not caused by increased dopamine catabolism or dopamine efflux. These data suggest that alpha-synuclein plays a role in the regulation of dopamine biosynthesis, acting to reduce the activity of tyrosine hydroxylase. If so, a loss of soluble alpha-synuclein, by reduced expression or aggregation, could increase dopamine synthesis with an accompanying increase in reactive dopamine metabolites.
Erratum in:
J Neurosci 22(20), 9142 (2002 Oct 15)
Evidence
3:
Inferred from Physical InteractionUniProtKB
Alpha-synuclein (SNCA) is an abundant neuronal protein involved in synaptic neurotransmission. SNCA expression levels have been strongly implicated in Parkinson's disease pathogenesis. We have previously demonstrated that in the PC12 cell line elements in intron 1 may mediate SNCA transcriptional regulation in response to neurotrophins. We have now identified transcription factor (TF) binding sites in intron 1 and the 5'-promoter of SNCA. A binding site for the TF zinc finger and SCAN domain containing (ZSCAN)21 in the 5'-region of intron 1 is required for intron 1 transcriptional activity. Small interfering RNA against ZSCAN21 inhibits activation in the luciferase assay and diminishes SNCA protein levels in naïve and neurotrophin-treated PC12 cells and in primary cultured cortical neurons, demonstrating that ZSCAN21 is a novel transcriptional regulator of SNCA in neuronal cells. The 5'-promoter of SNCA has a complex architecture, including multiple binding sites for the TF zinc finger protein (ZNF)219, which functions as both an activator and a repressor. Targeting ZSCAN21 or other TFs controlling SNCA transcriptional activity may provide novel therapeutic avenues not only for Parkinson's disease but also for other synucleopathies.
Evidence
4:
Inferred from Physical InteractionUniProtKB
The aggregation of α-synuclein (α-Syn), the major component of intracellular Lewy body inclusions in dopaminergic neurons of the substantia nigra, plays a critical role in the etiology of Parkinson disease (PD). Long-term effects of redox-active transition metals (Cu, Fe) and oxidative chemical imbalance underlie the disease progression and neuronal death. In this work, we provide evidence that a brain metalloprotein, Zn₇-metallothionein-3 (Zn₇MT-3), possesses a dynamic role in controlling aberrant protein-copper interactions in PD. We examined the properties of the α-Syn-Cu(II) complex with regard to molecular oxygen, the biological reducing agent ascorbate, and the neurotransmitter dopamine. The results revealed that under aerobic conditions α-Syn-Cu(II) possesses catalytic oxidase activity. The observed metal-centered redox chemistry significantly promotes the production of hydroxyl radicals and α-Syn oxidation and oligomerization, processes considered critical for cellular toxicity. Moreover, we show that Zn₇MT-3, through Cu(II) removal from the α-Syn-Cu(II) complex, efficiently prevents its deleterious redox activity. We demonstrate that the Cu(II) reduction by thiolate ligands of Zn₇MT-3 and the formation of Cu(I)₄Zn₄MT-3, in which an unusual oxygen-stable Cu(I)₄-thiolate cluster is present, comprise the underlying molecular mechanism by which α-Syn and dopamine oxidation, α-Syn oligomerization, and ROS production are abolished. These studies provide new insights into the bioinorganic chemistry of PD.
Evidence
5:
Inferred from Physical InteractionUniProtKB
Alpha-synuclein (alpha-Syn) has been studied in the context of Parkinson's disease, but its normative role remains elusive. We have shown that alpha-Syn regulates the homeostasis of dopaminergic and serotonergic synapses, through trafficking of the dopamine and serotonin transporter, respectively. In the present study we sought to determine if alpha-Syn could also modulate noradrenergic signaling, by studying its interactions with the norepinephrine transporter (NET). We co-transfected Ltk- cells with increasing amounts of alpha-Syn DNA and a constant amount of NET DNA, and observed a progressive decrease (68%) in [3H]-NE uptake in cells co-transfected with a ratio of 3:1 alpha-Syn:NET DNA. The Kd of transport did not change, but increasing alpha-Syn caused a decrease in the Vmax of the transporter, from 2.27+/-0.14 to 0.89+/-0.15 pmol/min/10(5) cells, with NET expression alone or 4:1 ratio of alpha-Syn:NET transfection, respectively. Decreases in surface biotinylation and [3H]-nisoxetine binding kinetics in intact cells revealed that NET cell surface expression was attenuated in correlation to the amount of alpha-Syn co-transfected into cells. The interaction between NET and alpha-Syn occurred via the NAC domain of alpha-Syn, the region directly responsible for self-aggregation. These findings are the first to show that alpha-Syn has a central role in the homeostasis of noradrenergic neurons. Together with our previous studies on dopamine and serotonin transporters, we propose that a primary physiological role of alpha-Syn may be to regulate the homeostasis of monoamines in synapses, through modulatory interactions of the protein with monoaminergic transporters.
Evidence
6:
Inferred from Physical InteractionUniProtKB
Human alpha-synuclein accumulates in dopaminergic neurons as intraneuronal inclusions, Lewy bodies, which are characteristic of idiopathic Parkinson's disease (PD). Here, we suggest that modulation of the functional activity of the dopamine transporter (DAT) by alpha-synuclein may be a key factor in the preferential degeneration of mesencephalic dopamine (DA)-synthesizing neurons in PD. In cotransfected Ltk-, HEK 293, and SK-N-MC cells, alpha-synuclein induced a 35% decrease in [3H]DA uptake. Biotinylated DAT levels were decreased by 40% in cotransfected cells relative to cells expressing only DAT. DAT was colocalized with alpha-synuclein in mesencephalic neurons and cotransfected Ltk- cells. Coimmunoprecipitation studies showed the existence of a complex between alpha-synuclein and DAT, in specific rat brain regions and cotransfected cells, through specific amino acid motifs of both proteins. The attenuation of DAT function by alpha-synuclein was cytoprotective, because DA-mediated oxidative stress and cell death were reduced in cotransfected cells. The neurotoxin MPP+ (1-methyl-4-phenylpyridinium), oxidative stress, or impairment of cell adhesion ablated the alpha-synuclein-mediated inhibition of DAT activity, which caused increased uptake of DA and increased biotinylated DAT levels, in both mesencephalic neurons and cotransfected cells. These studies suggest a novel normative role for alpha-synuclein in regulating DA synaptic availability and homeostasis, which is relevant to the pathophysiology of PD.
Evidence
7:
Inferred from Physical InteractionHGNC
Aggregation of the nerve cell protein alpha-synuclein is a characteristic of the common neurodegenerative alpha-synucleinopathies like Parkinson's disease and Lewy body dementia, and it plays a direct pathogenic role as demonstrated by early onset diseases caused by mis-sense mutations and multiplication of the alpha-synuclein gene. We investigated the existence of alpha-synuclein pro-aggregatory brain proteins whose dysregulation may contribute to disease progression, and we identified the brain-specific p25alpha as a candidate that preferentially binds to alpha-synuclein in its aggregated state. Functionally, purified recombinant human p25alpha strongly stimulates the aggregation of alpha-synuclein in vitro as demonstrated by thioflavin-T fluorescence and quantitative electron microscopy. p25alpha is normally only expressed in oligodendrocytes in contrast to alpha-synuclein, which is normally only expressed in neurons. This expression pattern is changed in alpha-synucleinopathies. In multiple systems atrophy, degenerating oligodendrocytes displayed accumulation of p25alpha and dystopically expressed alpha-synuclein in the glial cytoplasmic inclusions. In Parkinson's disease and Lewy body dementia, p25alpha was detectable in the neuronal Lewy body inclusions along with alpha-synuclein. The localization in alpha-synuclein-containing inclusions was verified biochemically by immunological detection in Lewy body inclusions purified from Lewy body dementia tissue and glial cytoplasmic inclusions purified from tissue from multiple systems atrophy. We suggest that p25alpha plays a pro-aggregatory role in the common neurodegenerative disorders hall-marked by alpha-synuclein aggregates.
Evidence
8:
Inferred from Physical InteractionUniProtKB
alpha-Synuclein (alpha-Syn), a protein primarily localized in the presynaptic compartment of neurons, is known to regulate dopaminergic neurotransmission by negatively modulating dopamine transporter activity and regulating its trafficking to or away from the cell surface. Given the considerable homology between dopamine transporters and the serotonin (5-HT) transporter (SERT), we examined whether alpha-Syn could similarly regulate SERT function. Increasing expression levels of human alpha-Syn gradually decreased [(3)H]5-HT uptake by human SERT in cotransfected Ltk(-) cells, by diminishing its V(max) without changing its K(m), as compared to cells expressing only SERT. Biotinylation studies to label cell-surface proteins showed that alpha-Syn decreased the levels of SERT present at the plasma membrane. alpha-Syn and SERT were able to coimmunoprecipitate (co-IP), suggesting heteromeric complexes between these two proteins through direct protein-protein interactions. The negative modulation of SERT activity by alpha-Syn occurred through the non-Abeta-amyloid component (NAC) domain of alpha-Syn (aa58-107); DNA constructs encoding this region mimicked the full-length alpha-Syn protein by decreasing [(3)H]5-HT uptake by the transporter. Furthermore, only the constructs encoding the NAC domain of alpha-Syn prevented the co-IPs between full-length alpha-Syn and SERT, in both transfected cells and in rat solubilized lysates isolated from the prefrontal cortex. These studies suggest a novel physiological role for alpha-Syn in regulating SERT activity and may be of relevance in certain mental illnesses and in depression, in which SERT function is believed to be dysregulated.
Evidence
9:
Inferred from Physical InteractionIntAct
α-Synuclein has been implicated in the pathogenesis of Parkinson's disease. Although it is highly conserved, its physiological function has not yet been elucidated in detail. In an effort to define the function of α-synuclein, interacting proteins were screened in phage display assays. Prenylated Rab acceptor protein 1 (PRA1) was identified as an interacting partner. A selective interaction between α-synuclein and PRA1 was confirmed by coimmunoprecipitation and GST pull-down assays. PRA1 and α-synuclein were colocalized in N2a neuronal cells. Cotransfection of α-synuclein and PRA1 caused vesicles to accumulate in the periphery of the cytosol in neuronal cells, suggesting that overexpression of α-synuclein hinders proper vesicle trafficking and recycling as a result of the interaction between α-synuclein and PRA1.
Evidence
10:
Inferred from Physical InteractionUniProtKB
Parkinson's disease (PD) is a neurodegenerative disorder affecting an estimated 4 million people worldwide. Intracellular proteinaceous inclusions called Lewy bodies are the histological hallmarks of PD and are primarily composed of aggregated alpha-synuclein (alphaSyn). Although the detailed mechanisms remain unclear, mounting evidence suggests that the misfolding of alphaSyn into prefibrillar and fibrillar species is the driving force responsible for cellular toxicity. We show here that the molecular chaperone heat shock protein (Hsp) 70 strongly inhibits alphaSyn fibril formation via preferential binding to prefibrillar species. Moreover, our studies reveal that Hsp70 alters the characteristics of toxic alphaSyn aggregates and indicate that cellular toxicity arises from the prefibrillar forms of alphaSyn. This work therefore elucidates a specific role of Hsp70 in the pathogenesis of PD and supports the general concept that chaperone action is a crucial aspect in protecting against the otherwise damaging consequences of protein misfolding.
Interacting selectively and non-covalently with a protein N-terminus, the end of any peptide chain at which the 2-amino (or 2-imino) function of a constituent amino acid is not attached in peptide linkage to another amino-acid residue.
Interacting selectively and non-covalently with tau protein. tau is a microtubule-associated protein, implicated in Alzheimer's disease, Down Syndrome and ALS.
alpha-Synuclein is a primarily neuronal protein that is enriched at the pre-synapse. alpha-Synuclein and the microtubule binding protein tau have been implicated in neurodegenerative diseases. alpha-Synuclein is known to associate with phospholipid vesicles, regulates dopamine metabolism and exhibits chaperone activity, but its main role remains largely unknown. Furthermore, knowledge on its interactions and post-translational modifications is essential for a molecular understanding of alpha-synucleinopathies. We investigated alpha-synuclein mutations, causative for autosomal dominant forms of Parkinson's disease (A30P, A53T and E46K), and phosphorylation mutants at serine 129 (S129A and S129D) using fluorescently labelled alpha-synuclein, actin and tau. The investigation of colocalization, and protein-protein interactions by Förster resonance energy transfer and fluorescence lifetime imaging showed that alpha-synuclein associates with the actin cytoskeleton and interacts with tau. The A30P mutation and cytoskeletal destabilization decreased this interaction. Given the concurrent loss of membrane binding by this mutation, we propose a membrane-bound functional complex with tau that might involve the actin cytoskeleton.
In Parkinson disease (PD) brain, a progressive loss of dopaminergic neurons leads to dopamine depletion in the striatum and reduced motor function. Lewy bodies, the characteristic neuropathological lesions found in the brain of PD patients, are composed mainly of α-synuclein protein. Three point mutations in the α-synuclein gene are associated with familial PD. In addition, genome-wide association studies indicate that α-synuclein and Tau protein synergistically increase disease susceptibility in the human population. To determine the mechanism by which α-synuclein and Tau act together, we have used PD-causing neurotoxin MPTP and pathogenic α-synuclein mutants A30P, E46K, and A53T as models. We found that exposure of human neuroblastoma M17 cells to MPTP enhances the intracellular α-synuclein protein level, stimulates Tau protein phosphorylation at Ser(262), and induces apoptosis. In mouse brain, ablation of α-synuclein function significantly suppresses Tau phosphorylation at Ser(262). In vitro, α-synuclein binds to phosphorylated Ser(214) of Tau and stimulates PKA-catalyzed Tau phosphorylation at Ser(262). PD-associated α-synuclein mutations increase α-synuclein binding to Tau and stimulate Tau phosphorylation at Ser(262). In HEK-293 cells, α-synuclein and its all PD-associated mutants destabilize the microtubule cytoskeleton in a similar extent. In contrast, when co-expressed with Tau, these PD-associated mutants destabilize microtubules with significantly higher potency than WT. Our results demonstrate that α-synuclein is an in vivo regulator of Tau protein phosphorylation at Ser(262) and suggest that PD-associated risk factors such as environmental toxins and α-synuclein mutations promote Tau phosphorylation at Ser(262), causing microtubule instability, which leads to loss of dopaminergic neurons in PD brain.
Multiple studies implicate metals in the pathophysiology of neurodegenerative diseases. Disturbances in brain iron metabolism are linked with synucleinopathies. For example, in Parkinson's disease, iron levels are increased and magnesium levels are reduced in the brains of patients. To understand how changes in iron and magnesium might affect the pathophysiology of Parkinson's disease, we investigated binding of iron to alpha-synuclein, which accumulates in Lewy bodies. Using fluorescence of the four tyrosines in alpha-synuclein as indicators of metal-related conformational changes in alpha-synuclein, we show that iron and magnesium both interact with alpha-synuclein. alpha-Synuclein exhibits fluorescence peaks at 310 and 375 nm. Iron lowers both fluorescence peaks, while magnesium increases the fluorescence peak only at 375 nm, which suggests that magnesium affects the conformation of alpha-synuclein differently than iron. Consistent with this hypothesis, we also observe that magnesium inhibits alpha-synuclein aggregation, measured by immunoblot, cellulose acetate filtration, or thioflavine-T fluorescence. In each of these studies, iron increases alpha-synuclein aggregation, while magnesium at concentrations >0.75 mm inhibits the aggregation of alpha-synuclein induced either spontaneously or by incubation with iron. These data suggest that the conformation of alpha-synuclein can be modulated by metals, with iron promoting aggregation and magnesium inhibiting aggregation.
A developmental process that is a deterioration and loss of function over time. Aging includes loss of functions such as resistance to disease, homeostasis, and fertility, as well as wear and tear. Aging includes cellular senescence, but is more inclusive. May precede death (GO:0016265) and may succeed developmental maturation (GO:0021700).
alpha-Synuclein has been implicated in the pathogenesis of Parkinson disease (PD) and related neurodegenerative disorders. More recently, it has been suggested to be an important regulatory component of vesicle transport in neuronal cells. alpha-Synuclein is also highly expressed in platelets and is loosely associated with the membrane of the secretory alpha-granules. However, the functional significance of these observations is unknown. In this study, the possible function of alpha-synuclein in vesicle transport, with particular regard to alpha-granule release from the platelets, was investigated. The results showed that ionomycin- or thrombin-induced alpha-granule secretion was inhibited by exogenous alpha-synuclein addition in a dose-dependent manner. However, [(3)H]5-HT release from the dense granules and hexosaminidase release from the lysosomal granules were not affected. Two point mutants (A30P and A53T) found in some familial types of PD, in addition to beta-synuclein and alpha-synuclein112, effectively inhibited PF4 release from the alpha-granules. However, the deletion mutants, which completely lacked either the N-terminal region or the C-terminal tail, did not affect alpha-granule release. Interestingly, exogenously added alpha-synuclein appeared to enter the platelets but did not change the Ca(++) level in the platelets at the resting state and the increase in the Ca(++) level on stimulation. Electron microscopy also supported that alpha-synuclein inhibits alpha-granule release. These results suggest that alpha-synuclein may function as a specific negative regulator of alpha-granule release in platelets.
Any process that results in a change in state or activity of a cell (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of a copper ion stimulus.
The aggregation of α-synuclein (α-Syn), the major component of intracellular Lewy body inclusions in dopaminergic neurons of the substantia nigra, plays a critical role in the etiology of Parkinson disease (PD). Long-term effects of redox-active transition metals (Cu, Fe) and oxidative chemical imbalance underlie the disease progression and neuronal death. In this work, we provide evidence that a brain metalloprotein, Zn₇-metallothionein-3 (Zn₇MT-3), possesses a dynamic role in controlling aberrant protein-copper interactions in PD. We examined the properties of the α-Syn-Cu(II) complex with regard to molecular oxygen, the biological reducing agent ascorbate, and the neurotransmitter dopamine. The results revealed that under aerobic conditions α-Syn-Cu(II) possesses catalytic oxidase activity. The observed metal-centered redox chemistry significantly promotes the production of hydroxyl radicals and α-Syn oxidation and oligomerization, processes considered critical for cellular toxicity. Moreover, we show that Zn₇MT-3, through Cu(II) removal from the α-Syn-Cu(II) complex, efficiently prevents its deleterious redox activity. We demonstrate that the Cu(II) reduction by thiolate ligands of Zn₇MT-3 and the formation of Cu(I)₄Zn₄MT-3, in which an unusual oxygen-stable Cu(I)₄-thiolate cluster is present, comprise the underlying molecular mechanism by which α-Syn and dopamine oxidation, α-Syn oligomerization, and ROS production are abolished. These studies provide new insights into the bioinorganic chemistry of PD.
Any process that results in a change in state or activity of a cell (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of an epinephrine stimulus. Epinephrine is a catecholamine that has the formula C9H13NO3; it is secreted by the adrenal medulla to act as a hormone, and released by certain neurons to act as a neurotransmitter active in the central nervous system.
The aggregation of α-synuclein (α-Syn), the major component of intracellular Lewy body inclusions in dopaminergic neurons of the substantia nigra, plays a critical role in the etiology of Parkinson disease (PD). Long-term effects of redox-active transition metals (Cu, Fe) and oxidative chemical imbalance underlie the disease progression and neuronal death. In this work, we provide evidence that a brain metalloprotein, Zn₇-metallothionein-3 (Zn₇MT-3), possesses a dynamic role in controlling aberrant protein-copper interactions in PD. We examined the properties of the α-Syn-Cu(II) complex with regard to molecular oxygen, the biological reducing agent ascorbate, and the neurotransmitter dopamine. The results revealed that under aerobic conditions α-Syn-Cu(II) possesses catalytic oxidase activity. The observed metal-centered redox chemistry significantly promotes the production of hydroxyl radicals and α-Syn oxidation and oligomerization, processes considered critical for cellular toxicity. Moreover, we show that Zn₇MT-3, through Cu(II) removal from the α-Syn-Cu(II) complex, efficiently prevents its deleterious redox activity. We demonstrate that the Cu(II) reduction by thiolate ligands of Zn₇MT-3 and the formation of Cu(I)₄Zn₄MT-3, in which an unusual oxygen-stable Cu(I)₄-thiolate cluster is present, comprise the underlying molecular mechanism by which α-Syn and dopamine oxidation, α-Syn oligomerization, and ROS production are abolished. These studies provide new insights into the bioinorganic chemistry of PD.
Any process that results in a change in state or activity of a cell (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of an fibroblast growth factor stimulus.
Any process that results in a change in state or activity of a cell (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of oxidative stress, a state often resulting from exposure to high levels of reactive oxygen species, e.g. superoxide anions, hydrogen peroxide (H2O2), and hydroxyl radicals.
The chemical reactions and pathways resulting in the formation of dopamine, a catecholamine neurotransmitter and a metabolic precursor of noradrenaline and adrenaline.
The aggregation of α-synuclein (α-Syn), the major component of intracellular Lewy body inclusions in dopaminergic neurons of the substantia nigra, plays a critical role in the etiology of Parkinson disease (PD). Long-term effects of redox-active transition metals (Cu, Fe) and oxidative chemical imbalance underlie the disease progression and neuronal death. In this work, we provide evidence that a brain metalloprotein, Zn₇-metallothionein-3 (Zn₇MT-3), possesses a dynamic role in controlling aberrant protein-copper interactions in PD. We examined the properties of the α-Syn-Cu(II) complex with regard to molecular oxygen, the biological reducing agent ascorbate, and the neurotransmitter dopamine. The results revealed that under aerobic conditions α-Syn-Cu(II) possesses catalytic oxidase activity. The observed metal-centered redox chemistry significantly promotes the production of hydroxyl radicals and α-Syn oxidation and oligomerization, processes considered critical for cellular toxicity. Moreover, we show that Zn₇MT-3, through Cu(II) removal from the α-Syn-Cu(II) complex, efficiently prevents its deleterious redox activity. We demonstrate that the Cu(II) reduction by thiolate ligands of Zn₇MT-3 and the formation of Cu(I)₄Zn₄MT-3, in which an unusual oxygen-stable Cu(I)₄-thiolate cluster is present, comprise the underlying molecular mechanism by which α-Syn and dopamine oxidation, α-Syn oligomerization, and ROS production are abolished. These studies provide new insights into the bioinorganic chemistry of PD.
The directed movement of dopamine into a presynaptic neuron or glial cell. In this context, dopamine is a catecholamine neurotransmitter and a metabolic precursor of noradrenaline and adrenaline.
The aggregation of α-synuclein (α-Syn), the major component of intracellular Lewy body inclusions in dopaminergic neurons of the substantia nigra, plays a critical role in the etiology of Parkinson disease (PD). Long-term effects of redox-active transition metals (Cu, Fe) and oxidative chemical imbalance underlie the disease progression and neuronal death. In this work, we provide evidence that a brain metalloprotein, Zn₇-metallothionein-3 (Zn₇MT-3), possesses a dynamic role in controlling aberrant protein-copper interactions in PD. We examined the properties of the α-Syn-Cu(II) complex with regard to molecular oxygen, the biological reducing agent ascorbate, and the neurotransmitter dopamine. The results revealed that under aerobic conditions α-Syn-Cu(II) possesses catalytic oxidase activity. The observed metal-centered redox chemistry significantly promotes the production of hydroxyl radicals and α-Syn oxidation and oligomerization, processes considered critical for cellular toxicity. Moreover, we show that Zn₇MT-3, through Cu(II) removal from the α-Syn-Cu(II) complex, efficiently prevents its deleterious redox activity. We demonstrate that the Cu(II) reduction by thiolate ligands of Zn₇MT-3 and the formation of Cu(I)₄Zn₄MT-3, in which an unusual oxygen-stable Cu(I)₄-thiolate cluster is present, comprise the underlying molecular mechanism by which α-Syn and dopamine oxidation, α-Syn oligomerization, and ROS production are abolished. These studies provide new insights into the bioinorganic chemistry of PD.
A process that is carried out at the cellular level which results in the assembly, arrangement of constituent parts, or disassembly of extracellular fibrils, extracellular matrix material consisting of polysaccharides and/or proteins.
The aggregation of α-synuclein (α-Syn), the major component of intracellular Lewy body inclusions in dopaminergic neurons of the substantia nigra, plays a critical role in the etiology of Parkinson disease (PD). Long-term effects of redox-active transition metals (Cu, Fe) and oxidative chemical imbalance underlie the disease progression and neuronal death. In this work, we provide evidence that a brain metalloprotein, Zn₇-metallothionein-3 (Zn₇MT-3), possesses a dynamic role in controlling aberrant protein-copper interactions in PD. We examined the properties of the α-Syn-Cu(II) complex with regard to molecular oxygen, the biological reducing agent ascorbate, and the neurotransmitter dopamine. The results revealed that under aerobic conditions α-Syn-Cu(II) possesses catalytic oxidase activity. The observed metal-centered redox chemistry significantly promotes the production of hydroxyl radicals and α-Syn oxidation and oligomerization, processes considered critical for cellular toxicity. Moreover, we show that Zn₇MT-3, through Cu(II) removal from the α-Syn-Cu(II) complex, efficiently prevents its deleterious redox activity. We demonstrate that the Cu(II) reduction by thiolate ligands of Zn₇MT-3 and the formation of Cu(I)₄Zn₄MT-3, in which an unusual oxygen-stable Cu(I)₄-thiolate cluster is present, comprise the underlying molecular mechanism by which α-Syn and dopamine oxidation, α-Syn oligomerization, and ROS production are abolished. These studies provide new insights into the bioinorganic chemistry of PD.
The chemical reactions and pathways involving fatty acids, aliphatic monocarboxylic acids liberated from naturally occurring fats and oils by hydrolysis.
A process that modulates synaptic plasticity such that synapses are changed resulting in the increase in the rate, or frequency of synaptic transmission at the synapse.
The transfer of electrons through a series of electron donors and acceptors, generating energy that is ultimately used for synthesis of ATP, as it occurs in the mitochondrial inner membrane or chloroplast thylakoid membrane.
A process that is carried out at the cellular level which results in the assembly, arrangement of constituent parts, or disassembly of a mitochondrial membrane, either of the lipid bilayer surrounding a mitochondrion.
Recent works suggest that alpha-synuclein could play a central role in Parkinson's disease (PD). Thus, two mutations were reported to be associated with rare autosomal dominant forms of the disease. We examined whether alpha-synuclein could modulate the caspase-mediated response and vulnerability of murine neurons in response to various apoptotic stimuli. We established TSM1 neuronal cell lines overexpressing wild-type (wt) alpha-synuclein or the PD-related Ala-53 --> Thr mutant alpha-synuclein. Under basal conditions, acetyl-Asp-Glu-Val-Asp-aldehyde-sensitive caspase activity appears significantly lower in wt alpha-synuclein-expressing cells than in neurons expressing the mutant. Interestingly, wt alpha-synuclein drastically reduces the caspase activation of TSM1 neurons upon three distinct apoptotic stimuli including staurosporine, etoposide, and ceramide C(2) when compared with mock-transfected cells. This inhibitory control of the caspase response triggered by apoptotic agents was abolished by the PD-related pathogenic mutation. Comparison of wild-type and mutated alpha-synuclein-expressing cells also indicates that the former exhibits much less vulnerability in response to staurosporine and etoposide as measured by the sodium 3'-[1-(phenylaminocarbonyl)-3, 4-tetrazolium]-bis(4-methoxy-6-nitro)benzenesulfonic acid assay. Altogether, our study indicates that wild-type alpha-synuclein exerts an antiapoptotic effect in neurons that appears to be abolished by the Parkinson's disease-related mutation, thereby suggesting a possible mechanism underlying both sporadic and familial forms of this neurodegenerative disease.
Negative regulation of cysteine-type endopeptidase activity involved in apoptotic processdefinition[GO:0043154]
Any process that stops, prevents, or reduces the frequency, rate or extent of a cysteine-type endopeptidase activity involved in the apoptotic process.
Evidence
1:
Inferred from Mutant PhenotypeUniProtKB
Recent works suggest that alpha-synuclein could play a central role in Parkinson's disease (PD). Thus, two mutations were reported to be associated with rare autosomal dominant forms of the disease. We examined whether alpha-synuclein could modulate the caspase-mediated response and vulnerability of murine neurons in response to various apoptotic stimuli. We established TSM1 neuronal cell lines overexpressing wild-type (wt) alpha-synuclein or the PD-related Ala-53 --> Thr mutant alpha-synuclein. Under basal conditions, acetyl-Asp-Glu-Val-Asp-aldehyde-sensitive caspase activity appears significantly lower in wt alpha-synuclein-expressing cells than in neurons expressing the mutant. Interestingly, wt alpha-synuclein drastically reduces the caspase activation of TSM1 neurons upon three distinct apoptotic stimuli including staurosporine, etoposide, and ceramide C(2) when compared with mock-transfected cells. This inhibitory control of the caspase response triggered by apoptotic agents was abolished by the PD-related pathogenic mutation. Comparison of wild-type and mutated alpha-synuclein-expressing cells also indicates that the former exhibits much less vulnerability in response to staurosporine and etoposide as measured by the sodium 3'-[1-(phenylaminocarbonyl)-3, 4-tetrazolium]-bis(4-methoxy-6-nitro)benzenesulfonic acid assay. Altogether, our study indicates that wild-type alpha-synuclein exerts an antiapoptotic effect in neurons that appears to be abolished by the Parkinson's disease-related mutation, thereby suggesting a possible mechanism underlying both sporadic and familial forms of this neurodegenerative disease.
Any process that stops, prevents, or reduces the frequency, rate or extent of the chemical reactions and pathways involving dopamine.
IEAOrtholog Compara
Negative regulation of dopamine uptake involved in synaptic transmissiondefinition[GO:0051585]
Any process that stops, prevents, or reduces the frequency, rate or extent of the directed movement of dopamine into a presynaptic neuron or glial cell.
Human alpha-synuclein accumulates in dopaminergic neurons as intraneuronal inclusions, Lewy bodies, which are characteristic of idiopathic Parkinson's disease (PD). Here, we suggest that modulation of the functional activity of the dopamine transporter (DAT) by alpha-synuclein may be a key factor in the preferential degeneration of mesencephalic dopamine (DA)-synthesizing neurons in PD. In cotransfected Ltk-, HEK 293, and SK-N-MC cells, alpha-synuclein induced a 35% decrease in [3H]DA uptake. Biotinylated DAT levels were decreased by 40% in cotransfected cells relative to cells expressing only DAT. DAT was colocalized with alpha-synuclein in mesencephalic neurons and cotransfected Ltk- cells. Coimmunoprecipitation studies showed the existence of a complex between alpha-synuclein and DAT, in specific rat brain regions and cotransfected cells, through specific amino acid motifs of both proteins. The attenuation of DAT function by alpha-synuclein was cytoprotective, because DA-mediated oxidative stress and cell death were reduced in cotransfected cells. The neurotoxin MPP+ (1-methyl-4-phenylpyridinium), oxidative stress, or impairment of cell adhesion ablated the alpha-synuclein-mediated inhibition of DAT activity, which caused increased uptake of DA and increased biotinylated DAT levels, in both mesencephalic neurons and cotransfected cells. These studies suggest a novel normative role for alpha-synuclein in regulating DA synaptic availability and homeostasis, which is relevant to the pathophysiology of PD.
alpha-Synuclein has been implicated in the pathogenesis of Parkinson disease (PD) and related neurodegenerative disorders. More recently, it has been suggested to be an important regulatory component of vesicle transport in neuronal cells. alpha-Synuclein is also highly expressed in platelets and is loosely associated with the membrane of the secretory alpha-granules. However, the functional significance of these observations is unknown. In this study, the possible function of alpha-synuclein in vesicle transport, with particular regard to alpha-granule release from the platelets, was investigated. The results showed that ionomycin- or thrombin-induced alpha-granule secretion was inhibited by exogenous alpha-synuclein addition in a dose-dependent manner. However, [(3)H]5-HT release from the dense granules and hexosaminidase release from the lysosomal granules were not affected. Two point mutants (A30P and A53T) found in some familial types of PD, in addition to beta-synuclein and alpha-synuclein112, effectively inhibited PF4 release from the alpha-granules. However, the deletion mutants, which completely lacked either the N-terminal region or the C-terminal tail, did not affect alpha-granule release. Interestingly, exogenously added alpha-synuclein appeared to enter the platelets but did not change the Ca(++) level in the platelets at the resting state and the increase in the Ca(++) level on stimulation. Electron microscopy also supported that alpha-synuclein inhibits alpha-granule release. These results suggest that alpha-synuclein may function as a specific negative regulator of alpha-granule release in platelets.
Alpha-synuclein is a neuronal protein implicated genetically in Parkinson's disease. alpha-synuclein localizes to the nucleus and presynaptic nerve terminals. Here we show that alpha-synuclein mediates neurotoxicity in the nucleus. Targeting of alpha-synuclein to the nucleus promotes toxicity, whereas cytoplasmic sequestration is protective in both cell culture and transgenic Drosophila. Toxicity of alpha-synuclein can be rescued by administration of histone deacetylase inhibitors in both cell culture and transgenic flies. Alpha-synuclein binds directly to histones, reduces the level of acetylated histone H3 in cultured cells and inhibits acetylation in histone acetyltransferase assays. Alpha-synuclein mutations that cause familial Parkinson's disease, A30P and A53T, exhibit increased nuclear targeting in cell culture. These findings implicate nuclear alpha-synuclein in promoting nigrostriatal degeneration in Parkinson's disease and encourage exploration of histone deacetylase inhibitors as potential therapies for the disorder.
In Parkinson disease (PD) brain, a progressive loss of dopaminergic neurons leads to dopamine depletion in the striatum and reduced motor function. Lewy bodies, the characteristic neuropathological lesions found in the brain of PD patients, are composed mainly of α-synuclein protein. Three point mutations in the α-synuclein gene are associated with familial PD. In addition, genome-wide association studies indicate that α-synuclein and Tau protein synergistically increase disease susceptibility in the human population. To determine the mechanism by which α-synuclein and Tau act together, we have used PD-causing neurotoxin MPTP and pathogenic α-synuclein mutants A30P, E46K, and A53T as models. We found that exposure of human neuroblastoma M17 cells to MPTP enhances the intracellular α-synuclein protein level, stimulates Tau protein phosphorylation at Ser(262), and induces apoptosis. In mouse brain, ablation of α-synuclein function significantly suppresses Tau phosphorylation at Ser(262). In vitro, α-synuclein binds to phosphorylated Ser(214) of Tau and stimulates PKA-catalyzed Tau phosphorylation at Ser(262). PD-associated α-synuclein mutations increase α-synuclein binding to Tau and stimulate Tau phosphorylation at Ser(262). In HEK-293 cells, α-synuclein and its all PD-associated mutants destabilize the microtubule cytoskeleton in a similar extent. In contrast, when co-expressed with Tau, these PD-associated mutants destabilize microtubules with significantly higher potency than WT. Our results demonstrate that α-synuclein is an in vivo regulator of Tau protein phosphorylation at Ser(262) and suggest that PD-associated risk factors such as environmental toxins and α-synuclein mutations promote Tau phosphorylation at Ser(262), causing microtubule instability, which leads to loss of dopaminergic neurons in PD brain.
J. Neurosci. 22, 3090-3099 (2002)[Full text:20026307][PubMed:11943812]
The alpha-synuclein gene is implicated in the pathogenesis of Parkinson's disease. Although alpha-synuclein function is uncertain, the protein has homology to the chaperone molecule 14-3-3. In addition, alpha-synuclein can bind to 14-3-3, and both alpha-synuclein and 14-3-3 bind to many of the same proteins. Because 14-3-3 binds to and activates tyrosine hydroxylase, the rate-limiting enzyme in dopamine (DA) biosynthesis, we explored whether alpha-synuclein also bound to tyrosine hydroxylase and influenced its activity. Immunoprecipitation revealed an interaction between alpha-synuclein and tyrosine hydroxylase in brain homogenates and MN9D dopaminergic cells. Colocalization of alpha-synuclein with tyrosine hydroxylase was confirmed by immunoelectron microscopy. To explore the consequences of the interaction, we measured the effect of recombinant alpha-synuclein on tyrosine hydroxylase activity in a cell-free system and observed a dose-dependent inhibition of tyrosine hydroxylase by alpha-synuclein. To measure the impact of alpha-synuclein on tyrosine hydroxylase in dopaminergic cells, we stably transfected MN9D cells with wild-type or A53T mutant alpha-synuclein. Overexpression of wild-type or A53T mutant alpha-synuclein did not significantly alter tyrosine hydroxylase protein levels in our stably transfected cells. However, overexpressing cell lines had significantly reduced tyrosine hydroxylase activity and a corresponding reduction in dopamine synthesis. The reduction in cellular dopamine levels was not caused by increased dopamine catabolism or dopamine efflux. These data suggest that alpha-synuclein plays a role in the regulation of dopamine biosynthesis, acting to reduce the activity of tyrosine hydroxylase. If so, a loss of soluble alpha-synuclein, by reduced expression or aggregation, could increase dopamine synthesis with an accompanying increase in reactive dopamine metabolites.
Alpha-synuclein (alpha-Syn) has been studied in the context of Parkinson's disease, but its normative role remains elusive. We have shown that alpha-Syn regulates the homeostasis of dopaminergic and serotonergic synapses, through trafficking of the dopamine and serotonin transporter, respectively. In the present study we sought to determine if alpha-Syn could also modulate noradrenergic signaling, by studying its interactions with the norepinephrine transporter (NET). We co-transfected Ltk- cells with increasing amounts of alpha-Syn DNA and a constant amount of NET DNA, and observed a progressive decrease (68%) in [3H]-NE uptake in cells co-transfected with a ratio of 3:1 alpha-Syn:NET DNA. The Kd of transport did not change, but increasing alpha-Syn caused a decrease in the Vmax of the transporter, from 2.27+/-0.14 to 0.89+/-0.15 pmol/min/10(5) cells, with NET expression alone or 4:1 ratio of alpha-Syn:NET transfection, respectively. Decreases in surface biotinylation and [3H]-nisoxetine binding kinetics in intact cells revealed that NET cell surface expression was attenuated in correlation to the amount of alpha-Syn co-transfected into cells. The interaction between NET and alpha-Syn occurred via the NAC domain of alpha-Syn, the region directly responsible for self-aggregation. These findings are the first to show that alpha-Syn has a central role in the homeostasis of noradrenergic neurons. Together with our previous studies on dopamine and serotonin transporters, we propose that a primary physiological role of alpha-Syn may be to regulate the homeostasis of monoamines in synapses, through modulatory interactions of the protein with monoaminergic transporters.
alpha-Synuclein has been implicated in the pathogenesis of Parkinson disease (PD) and related neurodegenerative disorders. More recently, it has been suggested to be an important regulatory component of vesicle transport in neuronal cells. alpha-Synuclein is also highly expressed in platelets and is loosely associated with the membrane of the secretory alpha-granules. However, the functional significance of these observations is unknown. In this study, the possible function of alpha-synuclein in vesicle transport, with particular regard to alpha-granule release from the platelets, was investigated. The results showed that ionomycin- or thrombin-induced alpha-granule secretion was inhibited by exogenous alpha-synuclein addition in a dose-dependent manner. However, [(3)H]5-HT release from the dense granules and hexosaminidase release from the lysosomal granules were not affected. Two point mutants (A30P and A53T) found in some familial types of PD, in addition to beta-synuclein and alpha-synuclein112, effectively inhibited PF4 release from the alpha-granules. However, the deletion mutants, which completely lacked either the N-terminal region or the C-terminal tail, did not affect alpha-granule release. Interestingly, exogenously added alpha-synuclein appeared to enter the platelets but did not change the Ca(++) level in the platelets at the resting state and the increase in the Ca(++) level on stimulation. Electron microscopy also supported that alpha-synuclein inhibits alpha-granule release. These results suggest that alpha-synuclein may function as a specific negative regulator of alpha-granule release in platelets.
alpha-Synuclein (alpha-Syn), a protein primarily localized in the presynaptic compartment of neurons, is known to regulate dopaminergic neurotransmission by negatively modulating dopamine transporter activity and regulating its trafficking to or away from the cell surface. Given the considerable homology between dopamine transporters and the serotonin (5-HT) transporter (SERT), we examined whether alpha-Syn could similarly regulate SERT function. Increasing expression levels of human alpha-Syn gradually decreased [(3)H]5-HT uptake by human SERT in cotransfected Ltk(-) cells, by diminishing its V(max) without changing its K(m), as compared to cells expressing only SERT. Biotinylation studies to label cell-surface proteins showed that alpha-Syn decreased the levels of SERT present at the plasma membrane. alpha-Syn and SERT were able to coimmunoprecipitate (co-IP), suggesting heteromeric complexes between these two proteins through direct protein-protein interactions. The negative modulation of SERT activity by alpha-Syn occurred through the non-Abeta-amyloid component (NAC) domain of alpha-Syn (aa58-107); DNA constructs encoding this region mimicked the full-length alpha-Syn protein by decreasing [(3)H]5-HT uptake by the transporter. Furthermore, only the constructs encoding the NAC domain of alpha-Syn prevented the co-IPs between full-length alpha-Syn and SERT, in both transfected cells and in rat solubilized lysates isolated from the prefrontal cortex. These studies suggest a novel physiological role for alpha-Syn in regulating SERT activity and may be of relevance in certain mental illnesses and in depression, in which SERT function is believed to be dysregulated.
Any process that stops, prevents, or reduces the frequency, rate or extent of thrombin receptor protein signaling pathway activity. A thrombin receptor signaling pathway is the series of molecular signals generated as a consequence of a thrombin receptor binding to one of its physiological ligands.
alpha-Synuclein has been implicated in the pathogenesis of Parkinson disease (PD) and related neurodegenerative disorders. More recently, it has been suggested to be an important regulatory component of vesicle transport in neuronal cells. alpha-Synuclein is also highly expressed in platelets and is loosely associated with the membrane of the secretory alpha-granules. However, the functional significance of these observations is unknown. In this study, the possible function of alpha-synuclein in vesicle transport, with particular regard to alpha-granule release from the platelets, was investigated. The results showed that ionomycin- or thrombin-induced alpha-granule secretion was inhibited by exogenous alpha-synuclein addition in a dose-dependent manner. However, [(3)H]5-HT release from the dense granules and hexosaminidase release from the lysosomal granules were not affected. Two point mutants (A30P and A53T) found in some familial types of PD, in addition to beta-synuclein and alpha-synuclein112, effectively inhibited PF4 release from the alpha-granules. However, the deletion mutants, which completely lacked either the N-terminal region or the C-terminal tail, did not affect alpha-granule release. Interestingly, exogenously added alpha-synuclein appeared to enter the platelets but did not change the Ca(++) level in the platelets at the resting state and the increase in the Ca(++) level on stimulation. Electron microscopy also supported that alpha-synuclein inhibits alpha-granule release. These results suggest that alpha-synuclein may function as a specific negative regulator of alpha-granule release in platelets.
alpha-Synuclein (alpha-Syn), a protein primarily localized in the presynaptic compartment of neurons, is known to regulate dopaminergic neurotransmission by negatively modulating dopamine transporter activity and regulating its trafficking to or away from the cell surface. Given the considerable homology between dopamine transporters and the serotonin (5-HT) transporter (SERT), we examined whether alpha-Syn could similarly regulate SERT function. Increasing expression levels of human alpha-Syn gradually decreased [(3)H]5-HT uptake by human SERT in cotransfected Ltk(-) cells, by diminishing its V(max) without changing its K(m), as compared to cells expressing only SERT. Biotinylation studies to label cell-surface proteins showed that alpha-Syn decreased the levels of SERT present at the plasma membrane. alpha-Syn and SERT were able to coimmunoprecipitate (co-IP), suggesting heteromeric complexes between these two proteins through direct protein-protein interactions. The negative modulation of SERT activity by alpha-Syn occurred through the non-Abeta-amyloid component (NAC) domain of alpha-Syn (aa58-107); DNA constructs encoding this region mimicked the full-length alpha-Syn protein by decreasing [(3)H]5-HT uptake by the transporter. Furthermore, only the constructs encoding the NAC domain of alpha-Syn prevented the co-IPs between full-length alpha-Syn and SERT, in both transfected cells and in rat solubilized lysates isolated from the prefrontal cortex. These studies suggest a novel physiological role for alpha-Syn in regulating SERT activity and may be of relevance in certain mental illnesses and in depression, in which SERT function is believed to be dysregulated.
A metabolic process that results in the removal or addition of one or more electrons to or from a substance, with or without the concomitant removal or addition of a proton or protons.
The aggregation of α-synuclein (α-Syn), the major component of intracellular Lewy body inclusions in dopaminergic neurons of the substantia nigra, plays a critical role in the etiology of Parkinson disease (PD). Long-term effects of redox-active transition metals (Cu, Fe) and oxidative chemical imbalance underlie the disease progression and neuronal death. In this work, we provide evidence that a brain metalloprotein, Zn₇-metallothionein-3 (Zn₇MT-3), possesses a dynamic role in controlling aberrant protein-copper interactions in PD. We examined the properties of the α-Syn-Cu(II) complex with regard to molecular oxygen, the biological reducing agent ascorbate, and the neurotransmitter dopamine. The results revealed that under aerobic conditions α-Syn-Cu(II) possesses catalytic oxidase activity. The observed metal-centered redox chemistry significantly promotes the production of hydroxyl radicals and α-Syn oxidation and oligomerization, processes considered critical for cellular toxicity. Moreover, we show that Zn₇MT-3, through Cu(II) removal from the α-Syn-Cu(II) complex, efficiently prevents its deleterious redox activity. We demonstrate that the Cu(II) reduction by thiolate ligands of Zn₇MT-3 and the formation of Cu(I)₄Zn₄MT-3, in which an unusual oxygen-stable Cu(I)₄-thiolate cluster is present, comprise the underlying molecular mechanism by which α-Syn and dopamine oxidation, α-Syn oligomerization, and ROS production are abolished. These studies provide new insights into the bioinorganic chemistry of PD.
Alpha-synuclein (alphaS) is an abundant neuronal cytoplasmic protein implicated in Parkinson's disease (PD), but its physiological function remains unknown. Consistent with its having structural motifs shared with class A1 apolipoproteins, alphaS can reversibly associate with membranes and help regulate membrane fatty acid composition. We previously observed that variations in alphaS expression level in dopaminergic cultured cells or brains are associated with changes in polyunsaturated fatty acid (PUFA) levels and altered membrane fluidity. We now report that alphaS acts with PUFAs to enhance the internalization of the membrane-binding dye, FM 1-43. Specifically, alphaS expression coupled with exposure to physiological levels of certain PUFAs enhanced clathrin-mediated endocytosis in neuronal and non-neuronal cultured cells. Moreover, alphaS expression and PUFA-enhanced basal and -evoked synaptic vesicle (SV) endocytosis in primary hippocampal cultures of wild type (wt) and genetically depleted alphaS mouse brains. We suggest that alphaS and PUFAs normally function in endocytic mechanisms and are specifically involved in SV recycling upon neuronal stimulation.
Any process that increases the rate, frequency or extent of inositol phosphate biosynthesis. Inositol phosphate biosynthetic processes are the chemical reactions and pathways resulting in the formation of an inositol phosphate, 1,2,3,4,5,6-cyclohexanehexol, with one or more phosphate groups attached.
Alpha-synuclein plays a key role in the pathogenesis of many neurodegenerative diseases. To date, its cellular role has yet to be determined, although it has been proposed to be connected to calcium and G protein-mediated dopamine signaling. Alpha-synuclein is known to bind strongly to model membrane surfaces where it may interact with other membrane-associated proteins. Here, we find that the membrane association of alpha-synuclein is enhanced by the presence of phosphatidylinositol 4,5-bisphosphate [PI(4,5)P(2)] and Ca(2+). We also find that alpha-synuclein interacts with high affinity with the G protein-regulated enzyme phospholipase Cbeta(2) (PLCbeta(2)), which catalyzes the hydrolysis of PI(4,5)P(2). Binding of alpha-synuclein to PLCbeta(2) reduces its catalytic activity by 50%, but causes its level of activation by Gbetagamma subunits to increase from 4- to 24-fold. This effect is greatly reduced for A53T alpha-synuclein, which is a mutant associated with familial Parkinson's disease. PI(4,5)P(2) hydrolysis by PLCbeta(2) results in an increase in the intracellular Ca(2+) concentration, and we find that in cultured cells the presence of alpha-synuclein results in a 6-fold enhancement in the release of Ca(2+) from intracellular stores in response to agents that release Gbetagamma subunits relative to controls. Alpha-synuclein also enhances the increase in the level of inositol phosphates seen upon G protein stimulation, suggesting that it also may interact with PLCbeta(2) in cells. Given that Ca(2+) and dopamine regulation are mediated through PLCbeta and G protein signals, our results suggest that alpha-synuclein may play a role in inositol phospholipid signaling.
In Parkinson disease (PD) brain, a progressive loss of dopaminergic neurons leads to dopamine depletion in the striatum and reduced motor function. Lewy bodies, the characteristic neuropathological lesions found in the brain of PD patients, are composed mainly of α-synuclein protein. Three point mutations in the α-synuclein gene are associated with familial PD. In addition, genome-wide association studies indicate that α-synuclein and Tau protein synergistically increase disease susceptibility in the human population. To determine the mechanism by which α-synuclein and Tau act together, we have used PD-causing neurotoxin MPTP and pathogenic α-synuclein mutants A30P, E46K, and A53T as models. We found that exposure of human neuroblastoma M17 cells to MPTP enhances the intracellular α-synuclein protein level, stimulates Tau protein phosphorylation at Ser(262), and induces apoptosis. In mouse brain, ablation of α-synuclein function significantly suppresses Tau phosphorylation at Ser(262). In vitro, α-synuclein binds to phosphorylated Ser(214) of Tau and stimulates PKA-catalyzed Tau phosphorylation at Ser(262). PD-associated α-synuclein mutations increase α-synuclein binding to Tau and stimulate Tau phosphorylation at Ser(262). In HEK-293 cells, α-synuclein and its all PD-associated mutants destabilize the microtubule cytoskeleton in a similar extent. In contrast, when co-expressed with Tau, these PD-associated mutants destabilize microtubules with significantly higher potency than WT. Our results demonstrate that α-synuclein is an in vivo regulator of Tau protein phosphorylation at Ser(262) and suggest that PD-associated risk factors such as environmental toxins and α-synuclein mutations promote Tau phosphorylation at Ser(262), causing microtubule instability, which leads to loss of dopaminergic neurons in PD brain.
Alpha-synuclein (alphaS) is an abundant neuronal cytoplasmic protein implicated in Parkinson's disease (PD), but its physiological function remains unknown. Consistent with its having structural motifs shared with class A1 apolipoproteins, alphaS can reversibly associate with membranes and help regulate membrane fatty acid composition. We previously observed that variations in alphaS expression level in dopaminergic cultured cells or brains are associated with changes in polyunsaturated fatty acid (PUFA) levels and altered membrane fluidity. We now report that alphaS acts with PUFAs to enhance the internalization of the membrane-binding dye, FM 1-43. Specifically, alphaS expression coupled with exposure to physiological levels of certain PUFAs enhanced clathrin-mediated endocytosis in neuronal and non-neuronal cultured cells. Moreover, alphaS expression and PUFA-enhanced basal and -evoked synaptic vesicle (SV) endocytosis in primary hippocampal cultures of wild type (wt) and genetically depleted alphaS mouse brains. We suggest that alphaS and PUFAs normally function in endocytic mechanisms and are specifically involved in SV recycling upon neuronal stimulation.
Positive regulation of release of sequestered calcium ion into cytosoldefinition[GO:0051281]
Any process that activates or increases the frequency, rate or extent of the release into the cytosolic compartment of calcium ions sequestered in the endoplasmic reticulum or mitochondria.
Alpha-synuclein plays a key role in the pathogenesis of many neurodegenerative diseases. To date, its cellular role has yet to be determined, although it has been proposed to be connected to calcium and G protein-mediated dopamine signaling. Alpha-synuclein is known to bind strongly to model membrane surfaces where it may interact with other membrane-associated proteins. Here, we find that the membrane association of alpha-synuclein is enhanced by the presence of phosphatidylinositol 4,5-bisphosphate [PI(4,5)P(2)] and Ca(2+). We also find that alpha-synuclein interacts with high affinity with the G protein-regulated enzyme phospholipase Cbeta(2) (PLCbeta(2)), which catalyzes the hydrolysis of PI(4,5)P(2). Binding of alpha-synuclein to PLCbeta(2) reduces its catalytic activity by 50%, but causes its level of activation by Gbetagamma subunits to increase from 4- to 24-fold. This effect is greatly reduced for A53T alpha-synuclein, which is a mutant associated with familial Parkinson's disease. PI(4,5)P(2) hydrolysis by PLCbeta(2) results in an increase in the intracellular Ca(2+) concentration, and we find that in cultured cells the presence of alpha-synuclein results in a 6-fold enhancement in the release of Ca(2+) from intracellular stores in response to agents that release Gbetagamma subunits relative to controls. Alpha-synuclein also enhances the increase in the level of inositol phosphates seen upon G protein stimulation, suggesting that it also may interact with PLCbeta(2) in cells. Given that Ca(2+) and dopamine regulation are mediated through PLCbeta and G protein signals, our results suggest that alpha-synuclein may play a role in inositol phospholipid signaling.
The aggregation of α-synuclein (α-Syn), the major component of intracellular Lewy body inclusions in dopaminergic neurons of the substantia nigra, plays a critical role in the etiology of Parkinson disease (PD). Long-term effects of redox-active transition metals (Cu, Fe) and oxidative chemical imbalance underlie the disease progression and neuronal death. In this work, we provide evidence that a brain metalloprotein, Zn₇-metallothionein-3 (Zn₇MT-3), possesses a dynamic role in controlling aberrant protein-copper interactions in PD. We examined the properties of the α-Syn-Cu(II) complex with regard to molecular oxygen, the biological reducing agent ascorbate, and the neurotransmitter dopamine. The results revealed that under aerobic conditions α-Syn-Cu(II) possesses catalytic oxidase activity. The observed metal-centered redox chemistry significantly promotes the production of hydroxyl radicals and α-Syn oxidation and oligomerization, processes considered critical for cellular toxicity. Moreover, we show that Zn₇MT-3, through Cu(II) removal from the α-Syn-Cu(II) complex, efficiently prevents its deleterious redox activity. We demonstrate that the Cu(II) reduction by thiolate ligands of Zn₇MT-3 and the formation of Cu(I)₄Zn₄MT-3, in which an unusual oxygen-stable Cu(I)₄-thiolate cluster is present, comprise the underlying molecular mechanism by which α-Syn and dopamine oxidation, α-Syn oligomerization, and ROS production are abolished. These studies provide new insights into the bioinorganic chemistry of PD.
A receptor-mediated endocytosis process that results in the movement of receptors from the plasma membrane to the inside of the cell. The process begins when cell surface receptors are monoubiquitinated following ligand-induced activation. Receptors are subsequently taken up into endocytic vesicles from where they are either targeted to the lysosome or vacuole for degradation or recycled back to the plasma membrane.
Alpha-synuclein (alphaS) is an abundant neuronal cytoplasmic protein implicated in Parkinson's disease (PD), but its physiological function remains unknown. Consistent with its having structural motifs shared with class A1 apolipoproteins, alphaS can reversibly associate with membranes and help regulate membrane fatty acid composition. We previously observed that variations in alphaS expression level in dopaminergic cultured cells or brains are associated with changes in polyunsaturated fatty acid (PUFA) levels and altered membrane fluidity. We now report that alphaS acts with PUFAs to enhance the internalization of the membrane-binding dye, FM 1-43. Specifically, alphaS expression coupled with exposure to physiological levels of certain PUFAs enhanced clathrin-mediated endocytosis in neuronal and non-neuronal cultured cells. Moreover, alphaS expression and PUFA-enhanced basal and -evoked synaptic vesicle (SV) endocytosis in primary hippocampal cultures of wild type (wt) and genetically depleted alphaS mouse brains. We suggest that alphaS and PUFAs normally function in endocytic mechanisms and are specifically involved in SV recycling upon neuronal stimulation.
The aggregation of α-synuclein (α-Syn), the major component of intracellular Lewy body inclusions in dopaminergic neurons of the substantia nigra, plays a critical role in the etiology of Parkinson disease (PD). Long-term effects of redox-active transition metals (Cu, Fe) and oxidative chemical imbalance underlie the disease progression and neuronal death. In this work, we provide evidence that a brain metalloprotein, Zn₇-metallothionein-3 (Zn₇MT-3), possesses a dynamic role in controlling aberrant protein-copper interactions in PD. We examined the properties of the α-Syn-Cu(II) complex with regard to molecular oxygen, the biological reducing agent ascorbate, and the neurotransmitter dopamine. The results revealed that under aerobic conditions α-Syn-Cu(II) possesses catalytic oxidase activity. The observed metal-centered redox chemistry significantly promotes the production of hydroxyl radicals and α-Syn oxidation and oligomerization, processes considered critical for cellular toxicity. Moreover, we show that Zn₇MT-3, through Cu(II) removal from the α-Syn-Cu(II) complex, efficiently prevents its deleterious redox activity. We demonstrate that the Cu(II) reduction by thiolate ligands of Zn₇MT-3 and the formation of Cu(I)₄Zn₄MT-3, in which an unusual oxygen-stable Cu(I)₄-thiolate cluster is present, comprise the underlying molecular mechanism by which α-Syn and dopamine oxidation, α-Syn oligomerization, and ROS production are abolished. These studies provide new insights into the bioinorganic chemistry of PD.
Any process that modulates the establishment or extent of the excitatory postsynaptic potential (EPSP) which is a temporary increase in postsynaptic potential due to the flow of positively charged ions into the postsynaptic cell. The flow of ions that causes an EPSP is an excitatory postsynaptic current (EPSC) and makes it easier for the neuron to fire an action potential.
A process that modulates long-term neuronal synaptic plasticity, the ability of neuronal synapses to change long-term as circumstances require. Long-term neuronal synaptic plasticity generally involves increase or decrease in actual synapse numbers.
Alpha-synuclein plays a key role in the pathogenesis of many neurodegenerative diseases. To date, its cellular role has yet to be determined, although it has been proposed to be connected to calcium and G protein-mediated dopamine signaling. Alpha-synuclein is known to bind strongly to model membrane surfaces where it may interact with other membrane-associated proteins. Here, we find that the membrane association of alpha-synuclein is enhanced by the presence of phosphatidylinositol 4,5-bisphosphate [PI(4,5)P(2)] and Ca(2+). We also find that alpha-synuclein interacts with high affinity with the G protein-regulated enzyme phospholipase Cbeta(2) (PLCbeta(2)), which catalyzes the hydrolysis of PI(4,5)P(2). Binding of alpha-synuclein to PLCbeta(2) reduces its catalytic activity by 50%, but causes its level of activation by Gbetagamma subunits to increase from 4- to 24-fold. This effect is greatly reduced for A53T alpha-synuclein, which is a mutant associated with familial Parkinson's disease. PI(4,5)P(2) hydrolysis by PLCbeta(2) results in an increase in the intracellular Ca(2+) concentration, and we find that in cultured cells the presence of alpha-synuclein results in a 6-fold enhancement in the release of Ca(2+) from intracellular stores in response to agents that release Gbetagamma subunits relative to controls. Alpha-synuclein also enhances the increase in the level of inositol phosphates seen upon G protein stimulation, suggesting that it also may interact with PLCbeta(2) in cells. Given that Ca(2+) and dopamine regulation are mediated through PLCbeta and G protein signals, our results suggest that alpha-synuclein may play a role in inositol phospholipid signaling.
Any process that results in a change in state or activity of a cell or an organism (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of a drug stimulus. A drug is a substance used in the diagnosis, treatment or prevention of a disease.
Any process that results in a change in state or activity of a cell or an organism (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of an interferon-gamma stimulus. Interferon-gamma is also known as type II interferon.
Human derived glioblastoma cells were cultured and treated with cytokines interleukin-6 (IL6), tumor necrosis factor alpha (TNF) and interferon-gamma (IFN) and imaged by fluorescence deconvolution microscopy to localize alpha-synuclein, tau and ubiquitin. Exposures were for short (2 h) and prolonged times (up to 96 h), with doses at both low (10 ng/ml), and high (100 ng/ml) concentrations. Further experiments used additive doses up to 200 ng/ml (2 x 100 ng), mimicking a super-infection state. Single, low doses of the cytokines initiated changes in levels of intracellular proteins, but these changes, be they increases or decreases, were not sustained, so we added higher doses of cytokine to the culture medium or fresh aliquots of cytokines over time. Finally, we treated cells with high, single doses of cytokine (200 ng/ml), to try to sustain perturbations of the proteins with cytokines. IFN caused a disruption and reduction of peripheral synuclein, TNF treatment resulted in increased levels of ubiquitin and IL6 disrupted and appeared to fragment tau. Of note, each of the proteins was found in a specific locale, tau being perinuclear, ubiquitin residing in the cytoplasm, and alpha-synuclein occupying the tips of cellular processes, exhibiting the characteristics of an adhesion protein/molecule [Word count=198].
Any process that results in a change in state or activity of a cell or an organism (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of an interleukin-1 stimulus.
Alpha-synuclein was originally identified as the presynaptic nerve terminal protein. Recently, we reported that alpha-synuclein is also expressed in cultured human astrocytes and that its levels are increased by stimulation with interleukin-1beta, suggesting that it may be involved in inflammatory processes. We therefore investigated the effect of inflammatory stimuli on alpha-synuclein expression in human macrophages. Alpha-synuclein mRNA and protein were detected in cultured human macrophages and levels of alpha-synuclein protein were increased by stimulation with lipopolysaccharide and interleukin-1beta in a time- and concentration-dependent manner. Immunofluorescent staining showed that alpha-synuclein protein was expressed within the cytoplasm and nucleus. Furthermore, alpha-synuclein immunoreactivity was present in alveolar macrophages from human lung tissues. These findings suggest that the function of alpha-synuclein is not exclusive to the nervous system and that alpha-synuclein may play a role in inflammatory processes and immune responses.
Any process that results in a change in state or activity of a cell or an organism (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of an iron(II) ion stimulus.
Multiple studies implicate metals in the pathophysiology of neurodegenerative diseases. Disturbances in brain iron metabolism are linked with synucleinopathies. For example, in Parkinson's disease, iron levels are increased and magnesium levels are reduced in the brains of patients. To understand how changes in iron and magnesium might affect the pathophysiology of Parkinson's disease, we investigated binding of iron to alpha-synuclein, which accumulates in Lewy bodies. Using fluorescence of the four tyrosines in alpha-synuclein as indicators of metal-related conformational changes in alpha-synuclein, we show that iron and magnesium both interact with alpha-synuclein. alpha-Synuclein exhibits fluorescence peaks at 310 and 375 nm. Iron lowers both fluorescence peaks, while magnesium increases the fluorescence peak only at 375 nm, which suggests that magnesium affects the conformation of alpha-synuclein differently than iron. Consistent with this hypothesis, we also observe that magnesium inhibits alpha-synuclein aggregation, measured by immunoblot, cellulose acetate filtration, or thioflavine-T fluorescence. In each of these studies, iron increases alpha-synuclein aggregation, while magnesium at concentrations >0.75 mm inhibits the aggregation of alpha-synuclein induced either spontaneously or by incubation with iron. These data suggest that the conformation of alpha-synuclein can be modulated by metals, with iron promoting aggregation and magnesium inhibiting aggregation.
Any process that results in a change in state or activity of an organism (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of a lipopolysaccharide stimulus; lipopolysaccharide is a major component of the cell wall of gram-negative bacteria.
Alpha-synuclein was originally identified as the presynaptic nerve terminal protein. Recently, we reported that alpha-synuclein is also expressed in cultured human astrocytes and that its levels are increased by stimulation with interleukin-1beta, suggesting that it may be involved in inflammatory processes. We therefore investigated the effect of inflammatory stimuli on alpha-synuclein expression in human macrophages. Alpha-synuclein mRNA and protein were detected in cultured human macrophages and levels of alpha-synuclein protein were increased by stimulation with lipopolysaccharide and interleukin-1beta in a time- and concentration-dependent manner. Immunofluorescent staining showed that alpha-synuclein protein was expressed within the cytoplasm and nucleus. Furthermore, alpha-synuclein immunoreactivity was present in alveolar macrophages from human lung tissues. These findings suggest that the function of alpha-synuclein is not exclusive to the nervous system and that alpha-synuclein may play a role in inflammatory processes and immune responses.
Any process that results in a change in state or activity of a cell or an organism (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of a magnesium ion stimulus.
Multiple studies implicate metals in the pathophysiology of neurodegenerative diseases. Disturbances in brain iron metabolism are linked with synucleinopathies. For example, in Parkinson's disease, iron levels are increased and magnesium levels are reduced in the brains of patients. To understand how changes in iron and magnesium might affect the pathophysiology of Parkinson's disease, we investigated binding of iron to alpha-synuclein, which accumulates in Lewy bodies. Using fluorescence of the four tyrosines in alpha-synuclein as indicators of metal-related conformational changes in alpha-synuclein, we show that iron and magnesium both interact with alpha-synuclein. alpha-Synuclein exhibits fluorescence peaks at 310 and 375 nm. Iron lowers both fluorescence peaks, while magnesium increases the fluorescence peak only at 375 nm, which suggests that magnesium affects the conformation of alpha-synuclein differently than iron. Consistent with this hypothesis, we also observe that magnesium inhibits alpha-synuclein aggregation, measured by immunoblot, cellulose acetate filtration, or thioflavine-T fluorescence. In each of these studies, iron increases alpha-synuclein aggregation, while magnesium at concentrations >0.75 mm inhibits the aggregation of alpha-synuclein induced either spontaneously or by incubation with iron. These data suggest that the conformation of alpha-synuclein can be modulated by metals, with iron promoting aggregation and magnesium inhibiting aggregation.
A process that is carried out at the cellular level which results in the assembly, arrangement of constituent parts, or disassembly of a synapse, the junction between a neuron and a target (neuron, muscle, or secretory cell).
An endocytosis process that results in the invagination of the axonal plasma membrane to create a membrane-bounded vesicle. This process takes up excess membrane that would otherwise accumulate at the presynaptic terminal due to fusion of vesicle membranes during neurotransmitter release. The vesicles created may subsequently be used for neurotransmitter storage and release.
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Pathways
According to KEGG, this protein belongs to the following pathways:
A reference proteome is a set of protein sequences derived from a complete proteome which constitutes a defined standard for a particular user community. Reference proteomes are manually defined according to a number of criteria. They cover the proteomes of well- studied model organisms and other proteomes of interest for biomedical and biotechnological research. Reference proteomes have been selected to provide broad coverage of the tree of life, and constitute a representative cross-section of the taxonomic diversity to be found within UniProtKB.
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