Responsible for the deacetylation of lysine residues on the N-terminal part of the core histones (H2A, H2B, H3 and H4). Histone deacetylation gives a tag for epigenetic repression and plays an important role in transcriptional regulation, cell cycle progression and developmental events. Histone deacetylases act via the formation of large multiprotein complexes (By similarity). Plays a central role in microtubule-dependent cell motility via deacetylation of tubulin.
Reversible acetylation of alpha-tubulin has been implicated in regulating microtubule stability and function. The distribution of acetylated alpha-tubulin is tightly controlled and stereotypic. Acetylated alpha-tubulin is most abundant in stable microtubules but is absent from dynamic cellular structures such as neuronal growth cones and the leading edges of fibroblasts. However, the enzymes responsible for regulating tubulin acetylation and deacetylation are not known. Here we report that a member of the histone deacetylase family, HDAC6, functions as a tubulin deacetylase. HDAC6 is localized exclusively in the cytoplasm, where it associates with microtubules and localizes with the microtubule motor complex containing p150(glued) (ref. 3). In vivo, the overexpression of HDAC6 leads to a global deacetylation of alpha-tubulin, whereas a decrease in HDAC6 increases alpha-tubulin acetylation. In vitro, purified HDAC6 potently deacetylates alpha-tubulin in assembled microtubules. Furthermore, overexpression of HDAC6 promotes chemotactic cell movement, supporting the idea that HDAC6-mediated deacetylation regulates microtubule-dependent cell motility. Our results show that HDAC6 is the tubulin deacetylase, and provide evidence that reversible acetylation regulates important biological processes beyond histone metabolism and gene transcription.
Sequestration of misfolded proteins into pericentriolar inclusions called aggresomes is a means that cells use to minimize misfolded protein-induced cytotoxicity. However, the molecular mechanism by which misfolded proteins are recruited to aggresomes remains unclear. Mutations in the E3 ligase parkin cause autosomal recessive Parkinson's disease that is devoid of Lewy bodies, which are similar to aggresomes. Here, we report that parkin cooperates with heterodimeric E2 enzyme UbcH13/Uev1a to mediate K63-linked polyubiquitination of misfolded DJ-1. K63-linked polyubiquitination of misfolded DJ-1 serves as a signal for interaction with histone deacetylase 6, an adaptor protein that binds the dynein-dynactin complex. Through this interaction, misfolded DJ-1 is linked to the dynein motor and transported to aggresomes. Furthermore, fibroblasts lacking parkin display deficits in targeting misfolded DJ-1 to aggresomes. Our findings reveal a signaling role for K63-linked polyubiquitination in dynein-mediated transport, identify parkin as a key regulator in the recruitment of misfolded DJ-1 to aggresomes, and have important implications regarding the biogenesis of Lewy bodies.
In addition to its protein deacetylase activity, plays a key role in the degradation of misfolded proteins: when misfolded proteins are too abundant to be degraded by the chaperone refolding system and the ubiquitin-proteasome, mediates the transport of misfolded proteins to a cytoplasmic juxtanuclear structure called aggresome. Probably acts as an adapter that recognizes polyubiquitinated misfolded proteins and target them to the aggresome, facilitating their clearance by autophagy.
Sequestration of misfolded proteins into pericentriolar inclusions called aggresomes is a means that cells use to minimize misfolded protein-induced cytotoxicity. However, the molecular mechanism by which misfolded proteins are recruited to aggresomes remains unclear. Mutations in the E3 ligase parkin cause autosomal recessive Parkinson's disease that is devoid of Lewy bodies, which are similar to aggresomes. Here, we report that parkin cooperates with heterodimeric E2 enzyme UbcH13/Uev1a to mediate K63-linked polyubiquitination of misfolded DJ-1. K63-linked polyubiquitination of misfolded DJ-1 serves as a signal for interaction with histone deacetylase 6, an adaptor protein that binds the dynein-dynactin complex. Through this interaction, misfolded DJ-1 is linked to the dynein motor and transported to aggresomes. Furthermore, fibroblasts lacking parkin display deficits in targeting misfolded DJ-1 to aggresomes. Our findings reveal a signaling role for K63-linked polyubiquitination in dynein-mediated transport, identify parkin as a key regulator in the recruitment of misfolded DJ-1 to aggresomes, and have important implications regarding the biogenesis of Lewy bodies.
Reversible acetylation of alpha-tubulin has been implicated in regulating microtubule stability and function. The distribution of acetylated alpha-tubulin is tightly controlled and stereotypic. Acetylated alpha-tubulin is most abundant in stable microtubules but is absent from dynamic cellular structures such as neuronal growth cones and the leading edges of fibroblasts. However, the enzymes responsible for regulating tubulin acetylation and deacetylation are not known. Here we report that a member of the histone deacetylase family, HDAC6, functions as a tubulin deacetylase. HDAC6 is localized exclusively in the cytoplasm, where it associates with microtubules and localizes with the microtubule motor complex containing p150(glued) (ref. 3). In vivo, the overexpression of HDAC6 leads to a global deacetylation of alpha-tubulin, whereas a decrease in HDAC6 increases alpha-tubulin acetylation. In vitro, purified HDAC6 potently deacetylates alpha-tubulin in assembled microtubules. Furthermore, overexpression of HDAC6 promotes chemotactic cell movement, supporting the idea that HDAC6-mediated deacetylation regulates microtubule-dependent cell motility. Our results show that HDAC6 is the tubulin deacetylase, and provide evidence that reversible acetylation regulates important biological processes beyond histone metabolism and gene transcription.
The cytoplasmic deacetylase HDAC6 is an important regulator of cellular pathways that include response to stress, protein folding, microtubule stability, and cell migration, thus representing an attractive target for cancer chemotherapy. However, little is known about its upstream regulation. Our previous work has implicated HDAC6 as a new protein target for the farnesyltransferase inhibitors (FTIs), although HDAC6 lacks a farnesylation motif. Here we show that the protein farnesyltransferase (FTase) and HDAC6 are present in a protein complex together with microtubules in vivo and in vitro. FTase binds microtubules directly via its alpha subunit, and this association requires the C terminus of tubulin. Treatment with an FTI removed FTase, but not HDAC6, from the protein complex, suggesting that the active form of FTase is bound to microtubules. Importantly, the removal of FTase from microtubules abrogated HDAC6 activity, as did a stable knockdown of the alpha subunit of FTase (FTalphaKD). Interestingly, the FTalphaKD cells showed increased sensitivity to the antiproliferative effects of Taxol and the FTI lonafarnib when used either as single agents or in combination as compared with parental cells. Altogether, these data suggest that FTase, via its tubulin-association, is a critical upstream regulator of HDAC6 activity and that FTase expression could help stratify cancer patients that would most benefit from this treatment.
Nuclear translocation of beta-catenin is a hallmark of Wnt signaling and is associated with various cancers. In addition to the canonical Wnt pathway activated by Wnt ligands, growth factors such as epidermal growth factor (EGF) also induce beta-catenin dissociation from the adherens junction complex, translocation into the nucleus, and activation of target genes such as c-myc. Here we report that EGF-induced beta-catenin nuclear localization and activation of c-myc are dependent on the deacetylase HDAC6. We show that EGF induces HDAC6 translocation to the caveolae membrane and association with beta-catenin. HDAC6 deacetylates beta-catenin at lysine 49, a site frequently mutated in anaplastic thyroid cancer, and inhibits beta-catenin phosphorylation at serine 45. HDAC6 inactivation blocks EGF-induced beta-catenin nuclear localization and decreases c-Myc expression, leading to inhibition of tumor cell proliferation. These results suggest that EGF-induced nuclear localization of beta-catenin is regulated by HDAC6-dependent deacetylation and provide a new mechanism by which HDAC inhibitors prevent tumor growth.
Interacting selectively and non-covalently with a dynein complex, a protein complex that contains two or three dynein heavy chains and several light chains, and has microtubule motor activity.
The efficient clearance of cytotoxic misfolded protein aggregates is critical for cell survival. Misfolded protein aggregates are transported and removed from the cytoplasm by dynein motors via the microtubule network to a novel organelle termed the aggresome where they are processed. However, the means by which dynein motors recognize misfolded protein cargo, and the cellular factors that regulate aggresome formation, remain unknown. We have discovered that HDAC6, a microtubule-associated deacetylase, is a component of the aggresome. We demonstrate that HDAC6 has the capacity to bind both polyubiquitinated misfolded proteins and dynein motors, thereby acting to recruit misfolded protein cargo to dynein motors for transport to aggresomes. Indeed, cells deficient in HDAC6 fail to clear misfolded protein aggregates from the cytoplasm, cannot form aggresomes properly, and are hypersensitive to the accumulation of misfolded proteins. These findings identify HDAC6 as a crucial player in the cellular management of misfolded protein-induced stress.
Histone acetylation is important for regulating chromatin structure and gene expression. Three classes of mammalian histone deacetylases have been identified. Among class II, there are five known members, namely HDAC4, HDAC5, HDAC6, HDAC7 and HDAC9. Here we describe the identification and characterization of a novel class II member termed HDAC10. It is a 669 residue polypeptide with a bipartite modular structure consisting of an N-terminal Hda1p-related putative deacetylase domain and a C-terminal leucine-rich domain. HDAC10 is widely expressed in adult human tissues and cultured mammalian cells. It is enriched in the cytoplasm and this enrichment is not sensitive to leptomycin B, a specific inhibitor known to block the nuclear export of other class II members. The leucine-rich domain of HDAC10 is responsible for its cytoplasmic enrichment. Recombinant HDAC10 protein possesses histone deacetylase activity, which is sensitive to trichostatin A, a specific inhibitor for known class I and class II histone deacetylases. When tethered to a promoter, HDAC10 is able to repress transcription. Furthermore, HDAC10 interacts with HDAC3 but not with HDAC4 or HDAC6. These results indicate that HDAC10 is a novel class II histone deacetylase possessing a unique leucine-rich domain.
Catalysis of the reaction: histone N6-acetyl-L-lysine + H2O = histone L-lysine + acetate. This reaction represents the removal of an acetyl group from a histone, a class of proteins complexed to DNA in chromatin and chromosomes.
Proc. Natl. Acad. Sci. U.S.A. 96, 4868-4873 (1999)[PubMed:10220385]
Gene expression is in part controlled by chromatin remodeling factors and the acetylation state of nucleosomal histones. The latter process is regulated by histone acetyltransferases and histone deacetylases (HDACs). Previously, three human and five yeast HDAC enzymes had been identified. These can be categorized into two classes: the first class represented by yeast Rpd3-like proteins and the second by yeast Hda1-like proteins. Human HDAC1, HDAC2, and HDAC3 proteins are members of the first class, whereas no class II human HDAC proteins had been identified. The amino acid sequence of Hda1p was used to search the GenBank/expressed sequence tag databases to identify partial sequences from three putative class II human HDAC proteins. The corresponding full-length cDNAs were cloned and defined as HDAC4, HDAC5, and HDAC6. These proteins possess certain features present in the conserved catalytic domains of class I human HDACs, but also contain additional sequence domains. Interestingly, HDAC6 contains an internal duplication of two catalytic domains, which appear to function independently of each other. These class II HDAC proteins have differential mRNA expression in human tissues and possess in vitro HDAC activity that is inhibited by trichostatin A. Coimmunoprecipitation experiments indicate that these HDAC proteins are not components of the previously identified HDAC1 and HDAC2 NRD and mSin3A complexes. However, HDAC4 and HDAC5 associate with HDAC3 in vivo. This finding suggests that the human class II HDAC enzymes may function in cellular processes distinct from those of HDAC1 and HDAC2.
The silent information regulator 2 protein (Sir2p) of Saccharomyces cerevisiae is an NAD-dependent histone deacetylase that plays a critical role in transcriptional silencing. Here, we report that a human ortholog of Sir2p, sirtuin type 2 (SIRT2), is a predominantly cytoplasmic protein that colocalizes with microtubules. SIRT2 deacetylates lysine-40 of alpha-tubulin both in vitro and in vivo. Knockdown of SIRT2 via siRNA results in tubulin hyperacetylation. SIRT2 colocalizes and interacts in vivo with HDAC6, another tubulin deacetylase. Enzymatic analysis of recombinant SIRT2 in comparison to a yeast homolog of Sir2 protein (Hst2p) shows a striking preference of SIRT2 for acetylated tubulin peptide as a substrate relative to acetylated histone H3 peptide. These observations establish SIRT2 as a bona fide tubulin deacetylase.
The molecular chaperone heat shock protein 90 (Hsp90) and its accessory cochaperones function by facilitating the structural maturation and complex assembly of client proteins, including steroid hormone receptors and selected kinases. By promoting the activity and stability of these signaling proteins, Hsp90 has emerged as a critical modulator in cell signaling. Here, we present evidence that Hsp90 chaperone activity is regulated by reversible acetylation and controlled by the deacetylase HDAC6. We show that HDAC6 functions as an Hsp90 deacetylase. Inactivation of HDAC6 leads to Hsp90 hyperacetylation, its dissociation from an essential cochaperone, p23, and a loss of chaperone activity. In HDAC6-deficient cells, Hsp90-dependent maturation of the glucocorticoid receptor (GR) is compromised, resulting in GR defective in ligand binding, nuclear translocation, and transcriptional activation. Our results identify Hsp90 as a target of HDAC6 and suggest reversible acetylation as a unique mechanism that regulates Hsp90 chaperone complex activity.
The cytoplasmic deacetylase HDAC6 is an important regulator of cellular pathways that include response to stress, protein folding, microtubule stability, and cell migration, thus representing an attractive target for cancer chemotherapy. However, little is known about its upstream regulation. Our previous work has implicated HDAC6 as a new protein target for the farnesyltransferase inhibitors (FTIs), although HDAC6 lacks a farnesylation motif. Here we show that the protein farnesyltransferase (FTase) and HDAC6 are present in a protein complex together with microtubules in vivo and in vitro. FTase binds microtubules directly via its alpha subunit, and this association requires the C terminus of tubulin. Treatment with an FTI removed FTase, but not HDAC6, from the protein complex, suggesting that the active form of FTase is bound to microtubules. Importantly, the removal of FTase from microtubules abrogated HDAC6 activity, as did a stable knockdown of the alpha subunit of FTase (FTalphaKD). Interestingly, the FTalphaKD cells showed increased sensitivity to the antiproliferative effects of Taxol and the FTI lonafarnib when used either as single agents or in combination as compared with parental cells. Altogether, these data suggest that FTase, via its tubulin-association, is a critical upstream regulator of HDAC6 activity and that FTase expression could help stratify cancer patients that would most benefit from this treatment.
Catalysis of the reaction: histone H3 N6-acetyl-L-lysine (position 14) + H2O = histone H3 L-lysine (position 14) + acetate. This reaction requires the presence of NAD, and represents the removal of an acetyl group from lysine at position 14 of the histone H3 protein.
Catalysis of the reaction: histone H3 N6-acetyl-L-lysine (position 18) + H2O = histone H3 L-lysine (position 18) + acetate. This reaction requires the presence of NAD, and represents the removal of an acetyl group from lysine at position 18 of the histone H3 protein.
Catalysis of the reaction: histone H3 N6-acetyl-L-lysine (position 9) + H2O = histone H3 L-lysine (position 9) + acetate. This reaction requires the presence of NAD, and represents the removal of an acetyl group from lysine at position 9 of the histone H3 protein.
Catalysis of the reaction: histone H4 N6-acetyl-L-lysine (position 16) + H2O = histone H4 L-lysine (position 16) + acetate. This reaction requires the presence of NAD, and represents the removal of an acetyl group from lysine at position 16 of the histone H4 protein.
The efficient clearance of cytotoxic misfolded protein aggregates is critical for cell survival. Misfolded protein aggregates are transported and removed from the cytoplasm by dynein motors via the microtubule network to a novel organelle termed the aggresome where they are processed. However, the means by which dynein motors recognize misfolded protein cargo, and the cellular factors that regulate aggresome formation, remain unknown. We have discovered that HDAC6, a microtubule-associated deacetylase, is a component of the aggresome. We demonstrate that HDAC6 has the capacity to bind both polyubiquitinated misfolded proteins and dynein motors, thereby acting to recruit misfolded protein cargo to dynein motors for transport to aggresomes. Indeed, cells deficient in HDAC6 fail to clear misfolded protein aggregates from the cytoplasm, cannot form aggresomes properly, and are hypersensitive to the accumulation of misfolded proteins. These findings identify HDAC6 as a crucial player in the cellular management of misfolded protein-induced stress.
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 InteractionIntAct
The ubiquitin ligase anaphase-promoting complex (APC) recruits the coactivator Cdc20 to drive mitosis in cycling cells. However, the nonmitotic functions of Cdc20-APC have remained unexplored. We report that Cdc20-APC plays an essential role in dendrite morphogenesis in postmitotic neurons. Knockdown of Cdc20 in cerebellar slices and in postnatal rats in vivo profoundly impairs the formation of granule neuron dendrite arbors in the cerebellar cortex. Remarkably, Cdc20 is enriched at the centrosome in neurons, and the centrosomal localization is critical for Cdc20-dependent dendrite development. We also find that the centrosome-associated protein histone deacetylase 6 (HDAC6) promotes the polyubiquitination of Cdc20, stimulates the activity of centrosomal Cdc20-APC, and drives the differentiation of dendrites. These findings define a postmitotic function for Cdc20-APC in the morphogenesis of dendrites in the mammalian brain. The identification of a centrosomal Cdc20-APC ubiquitin signaling pathway holds important implications for diverse biological processes, including neuronal connectivity and plasticity.
Evidence
2:
Inferred from Physical InteractionIntAct
Lysosomes are responsible for degradation and recycling of bulky cell material, including accumulated misfolded proteins and dysfunctional organelles. Increasing evidence implicates lysosomal dysfunction in several neurodegenerative disorders, including Parkinson's disease and related synucleinopathies, which are characterized by the accumulation of α-synuclein (α-syn) in Lewy bodies. Studies of lysosomal proteins linked to neurodegenerative disorders present an opportunity to uncover specific molecular mechanisms and pathways that contribute to neurodegeneration. Loss-of-function mutations in a lysosomal protein, ATP13A2 (PARK9), cause Kufor-Rakeb syndrome that is characterized by early-onset parkinsonism, pyramidal degeneration and dementia. While loss of ATP13A2 function plays a role in α-syn misfolding and toxicity, the normal function of ATP13A2 in the brain remains largely unknown. Here, we performed a screen to identify ATP13A2 interacting partners, as a first step toward elucidating its function. Utilizing a split-ubiquitin membrane yeast two-hybrid system that was developed to identify interacting partners of full-length integral membrane proteins, we identified 43 novel interactors that primarily implicate ATP13A2 in cellular processes such as endoplasmic reticulum (ER) translocation, ER-to-Golgi trafficking and vesicular transport and fusion. We showed that a subset of these interactors modified α-syn aggregation and α-syn-mediated degeneration of dopaminergic neurons in Caenorhabditis elegans, further suggesting that ATP13A2 and α-syn are functionally linked in neurodegeneration. These results implicate ATP13A2 in vesicular trafficking and provide a platform for further studies of ATP13A2 in neurodegeneration.
Evidence
3:
Inferred from Physical InteractionUniProtKB
During misfolded-protein stress, the cytoplasmic protein histone deacetylase 6 (HDAC6) functions as a linker between the dynein motor and polyubiquitin to mediate the transport of polyubiquitylated cargo to the aggresome. Here, we identify a new binding partner of HDAC6, the ubiquitin-like modifier FAT10 (also known as UBD), which is cytokine-inducible and - similar to ubiquitin - serves as a signal for proteasomal degradation. In vivo, the two proteins only interacted under conditions of proteasome impairment. The binding of HDAC6 to FAT10 was mediated by two separate domains: the C-terminal ubiquitin-binding zinc-finger (BUZ domain) of HDAC6 and its first catalytic domain, even though catalytic activity of HDAC6 was not required for this interaction. Both endogenous and ectopically expressed FAT10 as well as the model conjugate FAT10-GFP localized to the aggresome in a microtubule-dependent manner. Furthermore, FAT10-containing as well as ubiquitin-containing aggresomes were reduced in both size and number in HDAC6-deficient fibroblasts. We conclude that, if FAT10 fails to subject its target proteins to proteasomal degradation, an alternative route is taken to ensure their sequestration and possibly also their subsequent removal by transporting them to the aggresome via the association with HDAC6.
Evidence
4:
Inferred from Physical InteractionUniProtKB
Primary cilium dysfunction affects the development and homeostasis of many organs in Bardet-Biedl syndrome (BBS). We recently showed that seven highly conserved BBS proteins form a stable complex, the BBSome, that functions in membrane trafficking to and inside the primary cilium. We have now discovered a BBSome subunit that we named BBIP10. Similar to other BBSome subunits, BBIP10 localizes to the primary cilium, BBIP10 is present exclusively in ciliated organisms, and depletion of BBIP10 yields characteristic BBS phenotypes in zebrafish. Unexpectedly, BBIP10 is required for cytoplasmic microtubule polymerization and acetylation, two functions not shared with any other BBSome subunits. Strikingly, inhibition of the tubulin deacetylase HDAC6 restores microtubule acetylation in BBIP10-depleted cells, and BBIP10 physically interacts with HDAC6. BBSome-bound BBIP10 may therefore function to couple acetylation of axonemal microtubules and ciliary membrane growth.
Evidence
5:
Inferred from Physical InteractionUniProtKB
C/EBP homologous protein (CHOP) is an endoplasmic reticulum stress-inducible protein that plays a critical role in the regulation of programmed cell death; however, the regulation of its function has not been well characterized. We have previously demonstrated that CHOP is regulated by the ubiquitin-proteasome system. In this study, during the process of clarifying the mechanism of the degradation of CHOP, we identified a novel regulation domain of CHOP in its N-terminal portion that is involved in various regulations and functions. The CHOP N-terminal domain is necessary not only for protein degradation but also for its transactivity and interaction with p300. In addition, trichostatin A, a histone deacetylase inhibitor, repressed the degradation of CHOP protein via the N-terminal domain. TRB3, a mammalian tribbles homolog that functions as a repressor of CHOP, also interacted with CHOP via the N-terminal portion and significantly blocked the association of p300 with CHOP. These results suggest that the N-terminal portion of CHOP plays a crucial role in its functional regulation and enable us to identify a novel function of TRB3 as an intracellular antagonist of the p300-binding domain of CHOP.
Evidence
6:
Inferred from Physical InteractionIntAct
Breast cancer metastasis suppressor 1 (BRMS1) is a member of the mSin3-HDAC transcription co-repressor complex. However, the proteins associated with BRMS1 have not been fully identified. Yeast two-hybrid screen, immuno-affinity chromatography, and co-immunoprecipitation experiments were performed to identify BRMS1 interacting proteins (BIPs). In addition to known core mSin3 transcriptional complex components RBBP1 and mSDS3, BRMS1 interacted with other proteins including three chaperones: DNAJB6 (MRJ), Hsp90, and Hsp70. Hsp90 is a known target of HDAC6 and reversible acetylation is one of the mechanisms that is implicated in regulation of Hsp90 chaperone complex activity. BRMS1 interacted with class II HDACs, HDAC 4, 5, and 6. We further found that BRMS1 is stabilized by Hsp90, and its turnover is proteasome dependent. The stability of BRMS1 protein may be important in maintaining the functional role of BRMS1 in metastasis suppression.
Evidence
7:
Inferred from Physical InteractionIntAct
Human T cell leukemia virus type-1 (HTLV-1) is the causative agent of a fatal adult T-cell leukemia. Through deregulation of multiple cellular signaling pathways the viral Tax protein has a pivotal role in T-cell transformation. In response to stressful stimuli, cells mount a cellular stress response to limit the damage that environmental forces inflict on DNA or proteins. During stress response, cells postpone the translation of most cellular mRNAs, which are gathered into cytoplasmic mRNA-silencing foci called stress granules (SGs) and allocate their available resources towards the production of dedicated stress-management proteins. Here we demonstrate that Tax controls the formation of SGs and interferes with the cellular stress response pathway. In agreement with previous reports, we observed that Tax relocates from the nucleus to the cytoplasm in response to environmental stress. We found that the presence of Tax in the cytoplasm of stressed cells prevents the formation of SGs and counteracts the shutoff of specific host proteins. Unexpectedly, nuclear localization of Tax promotes spontaneous aggregation of SGs, even in the absence of stress. Mutant analysis revealed that the SG inhibitory capacity of Tax is independent of its transcriptional abilities but relies on its interaction with histone deacetylase 6, a critical component of SGs. Importantly, the stress-protective effect of Tax was also observed in the context of HTLV-1 infected cells, which were shown to be less prone to form SGs and undergo apoptosis under arsenite exposure. These observations identify Tax as the first virally encoded inhibitory component of SGs and unravel a new strategy developed by HTLV-1 to deregulate normal cell processes. We postulate that inhibition of the stress response pathway by Tax would favor cell survival under stressful conditions and may have an important role in HTLV-1-induced cellular transformation.
Evidence
8:
Inferred from Physical InteractionIntAct
Binding of epidermal growth factor (EGF) to its receptor leads to receptor dimerization, assembly of protein complexes, and activation of signaling networks that control key cellular responses. Despite their fundamental role in cell biology, little is known about protein complexes associated with the EGF receptor (EGFR) before growth factor stimulation. We used a modified membrane yeast two-hybrid system together with bioinformatics to identify 87 candidate proteins interacting with the ligand-unoccupied EGFR. Among them was histone deacetylase 6 (HDAC6), a cytoplasmic lysine deacetylase, which we found negatively regulated EGFR endocytosis and degradation by controlling the acetylation status of alpha-tubulin and, subsequently, receptor trafficking along microtubules. A negative feedback loop consisting of EGFR-mediated phosphorylation of HDAC6 Tyr(570) resulted in reduced deacetylase activity and increased acetylation of alpha-tubulin. This study illustrates the complexity of the EGFR-associated interactome and identifies protein acetylation as a previously unknown regulator of receptor endocytosis and degradation.
Interacting selectively and non-covalently with tau protein. tau is a microtubule-associated protein, implicated in Alzheimer's disease, Down Syndrome and ALS.
Histone deacetylase 6 (HDAC6), a unique cytoplasmic deacetylase, likely plays a role in neurodegeneration by coordinating cell responses to abnormal protein aggregation. Here, we provide in vitro and in vivo evidence that HDAC6 interacts with tau, a microtubule-associated protein that forms neurofibrillary tangles in Alzheimer's disease. This interaction is mediated by the microtubule-binding domain on tau and the Ser/Glu tetradecapeptide domain on HDAC6. Treatment with tubacin, a selective inhibitor of tubulin deacetylation activity of HDAC6, did not disrupt HDAC6-tau interaction. Nonetheless tubacin treatment attenuated site-specific tau phosphorylation, as did shRNA-mediated knockdown of HDAC6. Proteasome inhibition potentiated HDAC6-tau interactions and facilitated the concentration and co-localization of HDAC6 and tau in a perinuclear aggresome-like compartment, independent of HDAC6 tubulin deacetylase activity. Furthermore, we observed that in Alzheimer's disease brains the protein level of HDAC6 was significantly increased. These findings establish HDAC6 as a tau-interacting protein and as a potential modulator of tau phosphorylation and accumulation.
The silent information regulator 2 protein (Sir2p) of Saccharomyces cerevisiae is an NAD-dependent histone deacetylase that plays a critical role in transcriptional silencing. Here, we report that a human ortholog of Sir2p, sirtuin type 2 (SIRT2), is a predominantly cytoplasmic protein that colocalizes with microtubules. SIRT2 deacetylates lysine-40 of alpha-tubulin both in vitro and in vivo. Knockdown of SIRT2 via siRNA results in tubulin hyperacetylation. SIRT2 colocalizes and interacts in vivo with HDAC6, another tubulin deacetylase. Enzymatic analysis of recombinant SIRT2 in comparison to a yeast homolog of Sir2 protein (Hst2p) shows a striking preference of SIRT2 for acetylated tubulin peptide as a substrate relative to acetylated histone H3 peptide. These observations establish SIRT2 as a bona fide tubulin deacetylase.
The cytoplasmic deacetylase HDAC6 is an important regulator of cellular pathways that include response to stress, protein folding, microtubule stability, and cell migration, thus representing an attractive target for cancer chemotherapy. However, little is known about its upstream regulation. Our previous work has implicated HDAC6 as a new protein target for the farnesyltransferase inhibitors (FTIs), although HDAC6 lacks a farnesylation motif. Here we show that the protein farnesyltransferase (FTase) and HDAC6 are present in a protein complex together with microtubules in vivo and in vitro. FTase binds microtubules directly via its alpha subunit, and this association requires the C terminus of tubulin. Treatment with an FTI removed FTase, but not HDAC6, from the protein complex, suggesting that the active form of FTase is bound to microtubules. Importantly, the removal of FTase from microtubules abrogated HDAC6 activity, as did a stable knockdown of the alpha subunit of FTase (FTalphaKD). Interestingly, the FTalphaKD cells showed increased sensitivity to the antiproliferative effects of Taxol and the FTI lonafarnib when used either as single agents or in combination as compared with parental cells. Altogether, these data suggest that FTase, via its tubulin-association, is a critical upstream regulator of HDAC6 activity and that FTase expression could help stratify cancer patients that would most benefit from this treatment.
The efficient clearance of cytotoxic misfolded protein aggregates is critical for cell survival. Misfolded protein aggregates are transported and removed from the cytoplasm by dynein motors via the microtubule network to a novel organelle termed the aggresome where they are processed. However, the means by which dynein motors recognize misfolded protein cargo, and the cellular factors that regulate aggresome formation, remain unknown. We have discovered that HDAC6, a microtubule-associated deacetylase, is a component of the aggresome. We demonstrate that HDAC6 has the capacity to bind both polyubiquitinated misfolded proteins and dynein motors, thereby acting to recruit misfolded protein cargo to dynein motors for transport to aggresomes. Indeed, cells deficient in HDAC6 fail to clear misfolded protein aggregates from the cytoplasm, cannot form aggresomes properly, and are hypersensitive to the accumulation of misfolded proteins. These findings identify HDAC6 as a crucial player in the cellular management of misfolded protein-induced stress.
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 hydrogen peroxide (H2O2) stimulus.
Eighteen histone deacetylases (HDACs) are present in humans, categorized into two groups: zinc-dependent enzymes (HDAC1-11) and NAD(+)-dependent enzymes (sirtuins 1-7). Among zinc-dependent HDACs, HDAC6 is unique. It has a cytoplasmic localization, two catalytic sites, a ubiquitin-binding site, and it selectively deacetylases alpha-tubulin and Hsp90. Here, we report the discovery that the redox regulatory proteins, peroxiredoxin (Prx) I and Prx II are specific targets of HDAC6. Prx are antioxidants enzymes whose main function is H(2)O(2) reduction. Prx are elevated in many cancers and neurodegenerative diseases. The acetylated form of Prx accumulates in the absence of an active HDAC6. Acetylation of Prx increases its reducing activity, its resistance to superoxidation, and its resistance to transition to high-molecular-mass complexes. Thus, HDAC6 and Prx are targets for modulating intracellular redox status in therapeutic strategies for disorders as disparate as cancers and neurodegenerative diseases.
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 misfolded protein 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 a protein that is not folded in its correct three-dimensional structure.
CNS neurons are endowed with the ability to recover from cytotoxic insults associated with the accumulation of proteinaceous polyglutamine aggregates via a process that appears to involve capture and degradation of aggregates by autophagy. The ubiquitin-proteasome system protects cells against proteotoxicity by degrading soluble monomeric misfolded aggregation-prone proteins but is ineffective against, and impaired by, non-native protein oligomers. Here we show that autophagy is induced in response to impaired ubiquitin proteasome system activity. We show that ATG proteins, molecular determinants of autophagic vacuole formation, and lysosomes are recruited to pericentriolar cytoplasmic inclusion bodies by a process requiring an intact microtubule cytoskeleton and the cytoplasmic deacetylase HDAC6. These data suggest that HDAC6-dependent retrograde transport on microtubules is used by cells to increase the efficiency and selectivity of autophagic degradation.
Proc. Natl. Acad. Sci. U.S.A. 96, 4868-4873 (1999)[PubMed:10220385]
Gene expression is in part controlled by chromatin remodeling factors and the acetylation state of nucleosomal histones. The latter process is regulated by histone acetyltransferases and histone deacetylases (HDACs). Previously, three human and five yeast HDAC enzymes had been identified. These can be categorized into two classes: the first class represented by yeast Rpd3-like proteins and the second by yeast Hda1-like proteins. Human HDAC1, HDAC2, and HDAC3 proteins are members of the first class, whereas no class II human HDAC proteins had been identified. The amino acid sequence of Hda1p was used to search the GenBank/expressed sequence tag databases to identify partial sequences from three putative class II human HDAC proteins. The corresponding full-length cDNAs were cloned and defined as HDAC4, HDAC5, and HDAC6. These proteins possess certain features present in the conserved catalytic domains of class I human HDACs, but also contain additional sequence domains. Interestingly, HDAC6 contains an internal duplication of two catalytic domains, which appear to function independently of each other. These class II HDAC proteins have differential mRNA expression in human tissues and possess in vitro HDAC activity that is inhibited by trichostatin A. Coimmunoprecipitation experiments indicate that these HDAC proteins are not components of the previously identified HDAC1 and HDAC2 NRD and mSin3A complexes. However, HDAC4 and HDAC5 associate with HDAC3 in vivo. This finding suggests that the human class II HDAC enzymes may function in cellular processes distinct from those of HDAC1 and HDAC2.
Evidence
2:
Inferred from Sequence or Structural SimilarityUniProtKB
Histone acetylation is important for regulating chromatin structure and gene expression. Three classes of mammalian histone deacetylases have been identified. Among class II, there are five known members, namely HDAC4, HDAC5, HDAC6, HDAC7 and HDAC9. Here we describe the identification and characterization of a novel class II member termed HDAC10. It is a 669 residue polypeptide with a bipartite modular structure consisting of an N-terminal Hda1p-related putative deacetylase domain and a C-terminal leucine-rich domain. HDAC10 is widely expressed in adult human tissues and cultured mammalian cells. It is enriched in the cytoplasm and this enrichment is not sensitive to leptomycin B, a specific inhibitor known to block the nuclear export of other class II members. The leucine-rich domain of HDAC10 is responsible for its cytoplasmic enrichment. Recombinant HDAC10 protein possesses histone deacetylase activity, which is sensitive to trichostatin A, a specific inhibitor for known class I and class II histone deacetylases. When tethered to a promoter, HDAC10 is able to repress transcription. Furthermore, HDAC10 interacts with HDAC3 but not with HDAC4 or HDAC6. These results indicate that HDAC10 is a novel class II histone deacetylase possessing a unique leucine-rich domain.
The aryl hydrocarbon receptor (AhR), a ligand-activated member of the basic helix-loop-helix family of transcription factors, binds with high affinity to polycyclic aromatic hydrocarbons (PAH) and the environmental toxin 2,3,7,8-tetrachlorodibenzo-p-dioxin (dioxin). Most of the biochemical, biological, and toxicological responses caused by exposure to PAHs and polychlorinated dioxins are mediated, at least in part, by the AhR. The AhR is a client protein of Hsp90, a molecular chaperone that can be reversibly acetylated with functional consequences. The main objective of this study was to determine whether modulating Hsp90 acetylation would affect ligand-mediated activation of AhR signaling. Trichostatin A and suberoylanilide hydroxamic acid, two broad spectrum HDAC inhibitors, blocked PAH and dioxin-mediated induction of CYP1A1 and CYP1B1 in cell lines derived from the human aerodigestive tract. Silencing HDAC6 or treatment with tubacin, a pharmacological inhibitor of HDAC6, also suppressed the induction of CYP1A1 and CYP1B1. Inhibiting HDAC6 led to hyperacetylation of Hsp90 and loss of complex formation with AhR, cochaperone p23, and XAP-2. Inactivation or silencing of HDAC6 also led to reduced binding of ligand to the AhR and decreased translocation of the AhR from cytosol to nucleus in response to ligand. Ligand-induced recruitment of the AhR to the CYP1A1 and CYP1B1 promoters was inhibited when HDAC6 was inactivated. Mutation analysis of Hsp90 Lys(294) shows that its acetylation status is a strong determinant of interactions with AhR and p23 in addition to ligand-mediated activation of AhR signaling. Collectively, these results show that HDAC6 activity regulates the acetylation of Hsp90, the ability of Hsp90 to chaperone the AhR, and the expression of AhR-dependent genes. Given the established link between activation of AhR signaling and xenobiotic metabolism, inhibitors of HDAC6 may alter drug or carcinogen metabolism.
The directed movement of proteins in a cell, including the movement of proteins between specific compartments or structures within a cell, such as organelles of a eukaryotic cell.
CNS neurons are endowed with the ability to recover from cytotoxic insults associated with the accumulation of proteinaceous polyglutamine aggregates via a process that appears to involve capture and degradation of aggregates by autophagy. The ubiquitin-proteasome system protects cells against proteotoxicity by degrading soluble monomeric misfolded aggregation-prone proteins but is ineffective against, and impaired by, non-native protein oligomers. Here we show that autophagy is induced in response to impaired ubiquitin proteasome system activity. We show that ATG proteins, molecular determinants of autophagic vacuole formation, and lysosomes are recruited to pericentriolar cytoplasmic inclusion bodies by a process requiring an intact microtubule cytoskeleton and the cytoplasmic deacetylase HDAC6. These data suggest that HDAC6-dependent retrograde transport on microtubules is used by cells to increase the efficiency and selectivity of autophagic degradation.
CNS neurons are endowed with the ability to recover from cytotoxic insults associated with the accumulation of proteinaceous polyglutamine aggregates via a process that appears to involve capture and degradation of aggregates by autophagy. The ubiquitin-proteasome system protects cells against proteotoxicity by degrading soluble monomeric misfolded aggregation-prone proteins but is ineffective against, and impaired by, non-native protein oligomers. Here we show that autophagy is induced in response to impaired ubiquitin proteasome system activity. We show that ATG proteins, molecular determinants of autophagic vacuole formation, and lysosomes are recruited to pericentriolar cytoplasmic inclusion bodies by a process requiring an intact microtubule cytoskeleton and the cytoplasmic deacetylase HDAC6. These data suggest that HDAC6-dependent retrograde transport on microtubules is used by cells to increase the efficiency and selectivity of autophagic degradation.
The major inducible pathway for the general turnover of cytoplasmic constituents in eukaryotic cells, it is also responsible for the degradation of active cytoplasmic enzymes and organelles during nutrient starvation. Macroautophagy involves the formation of double-membrane-bounded autophagosomes which enclose the cytoplasmic constituent targeted for degradation in a membrane-bounded structure, which then fuse with the lysosome (or vacuole) releasing a single-membrane-bounded autophagic bodies which are then degraded within the lysosome (or vacuole). Though once thought to be a purely non-selective process, it appears that some types of macroautophagy, e.g. macropexophagy, macromitophagy, may involve selective targeting of the targets to be degraded.
CNS neurons are endowed with the ability to recover from cytotoxic insults associated with the accumulation of proteinaceous polyglutamine aggregates via a process that appears to involve capture and degradation of aggregates by autophagy. The ubiquitin-proteasome system protects cells against proteotoxicity by degrading soluble monomeric misfolded aggregation-prone proteins but is ineffective against, and impaired by, non-native protein oligomers. Here we show that autophagy is induced in response to impaired ubiquitin proteasome system activity. We show that ATG proteins, molecular determinants of autophagic vacuole formation, and lysosomes are recruited to pericentriolar cytoplasmic inclusion bodies by a process requiring an intact microtubule cytoskeleton and the cytoplasmic deacetylase HDAC6. These data suggest that HDAC6-dependent retrograde transport on microtubules is used by cells to increase the efficiency and selectivity of autophagic degradation.
The efficient clearance of cytotoxic misfolded protein aggregates is critical for cell survival. Misfolded protein aggregates are transported and removed from the cytoplasm by dynein motors via the microtubule network to a novel organelle termed the aggresome where they are processed. However, the means by which dynein motors recognize misfolded protein cargo, and the cellular factors that regulate aggresome formation, remain unknown. We have discovered that HDAC6, a microtubule-associated deacetylase, is a component of the aggresome. We demonstrate that HDAC6 has the capacity to bind both polyubiquitinated misfolded proteins and dynein motors, thereby acting to recruit misfolded protein cargo to dynein motors for transport to aggresomes. Indeed, cells deficient in HDAC6 fail to clear misfolded protein aggregates from the cytoplasm, cannot form aggresomes properly, and are hypersensitive to the accumulation of misfolded proteins. These findings identify HDAC6 as a crucial player in the cellular management of misfolded protein-induced stress.
Eighteen histone deacetylases (HDACs) are present in humans, categorized into two groups: zinc-dependent enzymes (HDAC1-11) and NAD(+)-dependent enzymes (sirtuins 1-7). Among zinc-dependent HDACs, HDAC6 is unique. It has a cytoplasmic localization, two catalytic sites, a ubiquitin-binding site, and it selectively deacetylases alpha-tubulin and Hsp90. Here, we report the discovery that the redox regulatory proteins, peroxiredoxin (Prx) I and Prx II are specific targets of HDAC6. Prx are antioxidants enzymes whose main function is H(2)O(2) reduction. Prx are elevated in many cancers and neurodegenerative diseases. The acetylated form of Prx accumulates in the absence of an active HDAC6. Acetylation of Prx increases its reducing activity, its resistance to superoxidation, and its resistance to transition to high-molecular-mass complexes. Thus, HDAC6 and Prx are targets for modulating intracellular redox status in therapeutic strategies for disorders as disparate as cancers and neurodegenerative diseases.
Any process that stops, prevents, or reduces the frequency, rate or extent of microtubule depolymerization; prevention of depolymerization of a microtubule can result from binding by 'capping' at the plus end (e.g. by interaction with another cellular protein of structure) or by exposing microtubules to a stabilizing drug such as taxol.
Any process that stops or reduces the rate of oxidoreductase activity, the 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.
Eighteen histone deacetylases (HDACs) are present in humans, categorized into two groups: zinc-dependent enzymes (HDAC1-11) and NAD(+)-dependent enzymes (sirtuins 1-7). Among zinc-dependent HDACs, HDAC6 is unique. It has a cytoplasmic localization, two catalytic sites, a ubiquitin-binding site, and it selectively deacetylases alpha-tubulin and Hsp90. Here, we report the discovery that the redox regulatory proteins, peroxiredoxin (Prx) I and Prx II are specific targets of HDAC6. Prx are antioxidants enzymes whose main function is H(2)O(2) reduction. Prx are elevated in many cancers and neurodegenerative diseases. The acetylated form of Prx accumulates in the absence of an active HDAC6. Acetylation of Prx increases its reducing activity, its resistance to superoxidation, and its resistance to transition to high-molecular-mass complexes. Thus, HDAC6 and Prx are targets for modulating intracellular redox status in therapeutic strategies for disorders as disparate as cancers and neurodegenerative diseases.
Any process that stops, prevents, or reduces the frequency, rate or extent of protein complex disassembly, the disaggregation of a protein complex into its constituent components.
The molecular chaperone heat shock protein 90 (Hsp90) and its accessory cochaperones function by facilitating the structural maturation and complex assembly of client proteins, including steroid hormone receptors and selected kinases. By promoting the activity and stability of these signaling proteins, Hsp90 has emerged as a critical modulator in cell signaling. Here, we present evidence that Hsp90 chaperone activity is regulated by reversible acetylation and controlled by the deacetylase HDAC6. We show that HDAC6 functions as an Hsp90 deacetylase. Inactivation of HDAC6 leads to Hsp90 hyperacetylation, its dissociation from an essential cochaperone, p23, and a loss of chaperone activity. In HDAC6-deficient cells, Hsp90-dependent maturation of the glucocorticoid receptor (GR) is compromised, resulting in GR defective in ligand binding, nuclear translocation, and transcriptional activation. Our results identify Hsp90 as a target of HDAC6 and suggest reversible acetylation as a unique mechanism that regulates Hsp90 chaperone complex activity.
Nuclear translocation of beta-catenin is a hallmark of Wnt signaling and is associated with various cancers. In addition to the canonical Wnt pathway activated by Wnt ligands, growth factors such as epidermal growth factor (EGF) also induce beta-catenin dissociation from the adherens junction complex, translocation into the nucleus, and activation of target genes such as c-myc. Here we report that EGF-induced beta-catenin nuclear localization and activation of c-myc are dependent on the deacetylase HDAC6. We show that EGF induces HDAC6 translocation to the caveolae membrane and association with beta-catenin. HDAC6 deacetylates beta-catenin at lysine 49, a site frequently mutated in anaplastic thyroid cancer, and inhibits beta-catenin phosphorylation at serine 45. HDAC6 inactivation blocks EGF-induced beta-catenin nuclear localization and decreases c-Myc expression, leading to inhibition of tumor cell proliferation. These results suggest that EGF-induced nuclear localization of beta-catenin is regulated by HDAC6-dependent deacetylation and provide a new mechanism by which HDAC inhibitors prevent tumor growth.
Histone acetylation is important for regulating chromatin structure and gene expression. Three classes of mammalian histone deacetylases have been identified. Among class II, there are five known members, namely HDAC4, HDAC5, HDAC6, HDAC7 and HDAC9. Here we describe the identification and characterization of a novel class II member termed HDAC10. It is a 669 residue polypeptide with a bipartite modular structure consisting of an N-terminal Hda1p-related putative deacetylase domain and a C-terminal leucine-rich domain. HDAC10 is widely expressed in adult human tissues and cultured mammalian cells. It is enriched in the cytoplasm and this enrichment is not sensitive to leptomycin B, a specific inhibitor known to block the nuclear export of other class II members. The leucine-rich domain of HDAC10 is responsible for its cytoplasmic enrichment. Recombinant HDAC10 protein possesses histone deacetylase activity, which is sensitive to trichostatin A, a specific inhibitor for known class I and class II histone deacetylases. When tethered to a promoter, HDAC10 is able to repress transcription. Furthermore, HDAC10 interacts with HDAC3 but not with HDAC4 or HDAC6. These results indicate that HDAC10 is a novel class II histone deacetylase possessing a unique leucine-rich domain.
Nuclear translocation of beta-catenin is a hallmark of Wnt signaling and is associated with various cancers. In addition to the canonical Wnt pathway activated by Wnt ligands, growth factors such as epidermal growth factor (EGF) also induce beta-catenin dissociation from the adherens junction complex, translocation into the nucleus, and activation of target genes such as c-myc. Here we report that EGF-induced beta-catenin nuclear localization and activation of c-myc are dependent on the deacetylase HDAC6. We show that EGF induces HDAC6 translocation to the caveolae membrane and association with beta-catenin. HDAC6 deacetylates beta-catenin at lysine 49, a site frequently mutated in anaplastic thyroid cancer, and inhibits beta-catenin phosphorylation at serine 45. HDAC6 inactivation blocks EGF-induced beta-catenin nuclear localization and decreases c-Myc expression, leading to inhibition of tumor cell proliferation. These results suggest that EGF-induced nuclear localization of beta-catenin is regulated by HDAC6-dependent deacetylation and provide a new mechanism by which HDAC inhibitors prevent tumor growth.
Eighteen histone deacetylases (HDACs) are present in humans, categorized into two groups: zinc-dependent enzymes (HDAC1-11) and NAD(+)-dependent enzymes (sirtuins 1-7). Among zinc-dependent HDACs, HDAC6 is unique. It has a cytoplasmic localization, two catalytic sites, a ubiquitin-binding site, and it selectively deacetylases alpha-tubulin and Hsp90. Here, we report the discovery that the redox regulatory proteins, peroxiredoxin (Prx) I and Prx II are specific targets of HDAC6. Prx are antioxidants enzymes whose main function is H(2)O(2) reduction. Prx are elevated in many cancers and neurodegenerative diseases. The acetylated form of Prx accumulates in the absence of an active HDAC6. Acetylation of Prx increases its reducing activity, its resistance to superoxidation, and its resistance to transition to high-molecular-mass complexes. Thus, HDAC6 and Prx are targets for modulating intracellular redox status in therapeutic strategies for disorders as disparate as cancers and neurodegenerative diseases.
The directed movement of misfolded polyubiquitinated proteins in a cell, including the movement of proteins between specific compartments or structures within a cell.
The efficient clearance of cytotoxic misfolded protein aggregates is critical for cell survival. Misfolded protein aggregates are transported and removed from the cytoplasm by dynein motors via the microtubule network to a novel organelle termed the aggresome where they are processed. However, the means by which dynein motors recognize misfolded protein cargo, and the cellular factors that regulate aggresome formation, remain unknown. We have discovered that HDAC6, a microtubule-associated deacetylase, is a component of the aggresome. We demonstrate that HDAC6 has the capacity to bind both polyubiquitinated misfolded proteins and dynein motors, thereby acting to recruit misfolded protein cargo to dynein motors for transport to aggresomes. Indeed, cells deficient in HDAC6 fail to clear misfolded protein aggregates from the cytoplasm, cannot form aggresomes properly, and are hypersensitive to the accumulation of misfolded proteins. These findings identify HDAC6 as a crucial player in the cellular management of misfolded protein-induced stress.
Eighteen histone deacetylases (HDACs) are present in humans, categorized into two groups: zinc-dependent enzymes (HDAC1-11) and NAD(+)-dependent enzymes (sirtuins 1-7). Among zinc-dependent HDACs, HDAC6 is unique. It has a cytoplasmic localization, two catalytic sites, a ubiquitin-binding site, and it selectively deacetylases alpha-tubulin and Hsp90. Here, we report the discovery that the redox regulatory proteins, peroxiredoxin (Prx) I and Prx II are specific targets of HDAC6. Prx are antioxidants enzymes whose main function is H(2)O(2) reduction. Prx are elevated in many cancers and neurodegenerative diseases. The acetylated form of Prx accumulates in the absence of an active HDAC6. Acetylation of Prx increases its reducing activity, its resistance to superoxidation, and its resistance to transition to high-molecular-mass complexes. Thus, HDAC6 and Prx are targets for modulating intracellular redox status in therapeutic strategies for disorders as disparate as cancers and neurodegenerative diseases.
Positive regulation of chaperone-mediated protein complex assemblydefinition[GO:0090035]
Any process that increases the frequency, rate, or extent of chaperone-mediated protein complex assembly. Chaperone-mediated protein complex assembly is the aggregation, arrangement and bonding together of a set of components to form a protein complex, mediated by chaperone molecules that do not form part of the finished complex.
The aryl hydrocarbon receptor (AhR), a ligand-activated member of the basic helix-loop-helix family of transcription factors, binds with high affinity to polycyclic aromatic hydrocarbons (PAH) and the environmental toxin 2,3,7,8-tetrachlorodibenzo-p-dioxin (dioxin). Most of the biochemical, biological, and toxicological responses caused by exposure to PAHs and polychlorinated dioxins are mediated, at least in part, by the AhR. The AhR is a client protein of Hsp90, a molecular chaperone that can be reversibly acetylated with functional consequences. The main objective of this study was to determine whether modulating Hsp90 acetylation would affect ligand-mediated activation of AhR signaling. Trichostatin A and suberoylanilide hydroxamic acid, two broad spectrum HDAC inhibitors, blocked PAH and dioxin-mediated induction of CYP1A1 and CYP1B1 in cell lines derived from the human aerodigestive tract. Silencing HDAC6 or treatment with tubacin, a pharmacological inhibitor of HDAC6, also suppressed the induction of CYP1A1 and CYP1B1. Inhibiting HDAC6 led to hyperacetylation of Hsp90 and loss of complex formation with AhR, cochaperone p23, and XAP-2. Inactivation or silencing of HDAC6 also led to reduced binding of ligand to the AhR and decreased translocation of the AhR from cytosol to nucleus in response to ligand. Ligand-induced recruitment of the AhR to the CYP1A1 and CYP1B1 promoters was inhibited when HDAC6 was inactivated. Mutation analysis of Hsp90 Lys(294) shows that its acetylation status is a strong determinant of interactions with AhR and p23 in addition to ligand-mediated activation of AhR signaling. Collectively, these results show that HDAC6 activity regulates the acetylation of Hsp90, the ability of Hsp90 to chaperone the AhR, and the expression of AhR-dependent genes. Given the established link between activation of AhR signaling and xenobiotic metabolism, inhibitors of HDAC6 may alter drug or carcinogen metabolism.
Reversible acetylation of alpha-tubulin has been implicated in regulating microtubule stability and function. The distribution of acetylated alpha-tubulin is tightly controlled and stereotypic. Acetylated alpha-tubulin is most abundant in stable microtubules but is absent from dynamic cellular structures such as neuronal growth cones and the leading edges of fibroblasts. However, the enzymes responsible for regulating tubulin acetylation and deacetylation are not known. Here we report that a member of the histone deacetylase family, HDAC6, functions as a tubulin deacetylase. HDAC6 is localized exclusively in the cytoplasm, where it associates with microtubules and localizes with the microtubule motor complex containing p150(glued) (ref. 3). In vivo, the overexpression of HDAC6 leads to a global deacetylation of alpha-tubulin, whereas a decrease in HDAC6 increases alpha-tubulin acetylation. In vitro, purified HDAC6 potently deacetylates alpha-tubulin in assembled microtubules. Furthermore, overexpression of HDAC6 promotes chemotactic cell movement, supporting the idea that HDAC6-mediated deacetylation regulates microtubule-dependent cell motility. Our results show that HDAC6 is the tubulin deacetylase, and provide evidence that reversible acetylation regulates important biological processes beyond histone metabolism and gene transcription.
Any process that increases the frequency or rate of receptor biosynthesis. Receptor biosynthesis is the collection of chemical reactions and pathways resulting in the formation of a receptor molecule, a macromolecule that undergoes combination with a hormone, neurotransmitter, drug or intracellular messenger to initiate a change in cell function.
Several histone deacetylases (HDAC) are involved in estrogen receptor (ER)-mediated gene transactivation, and HDAC inhibitors have been reported to restore sensitivity to antihormonal therapy. The modulation of ER is the most promising approach to ER-expressing breast cancers. Recent studies further suggest a critical role of the progesterone receptor (PR) on ER signaling. Although HDAC inhibitors modulate ER, little is known about their effects on PR. We evaluated the roles of specific HDAC isoenzymes and their inhibition on both ER and PR signaling and their importance in response to endocrine therapy. The roles of individual HDAC isoenzymes on ER and PR expression and their functions were evaluated by depletion of select HDAC enzymes using siRNA or pharmacologic inhibition. Cotreatment of breast cancer cell lines with HDAC inhibitors and the antiestrogen, tamoxifen, resulted in synergistic antitumor activity with simultaneous depletion of both ER and PR. Selective inhibition of HDAC2, but not HDAC1 or HDAC6, was sufficient to potentiate tamoxifen-induced apoptosis in ER/PR-positive cells. Depletion of HDAC1 and HDAC6 was associated with down-regulation of ER but not PR. Only the selective depletion of HDAC2 siRNA down-regulated both ER and PR expression, and was sufficient to potentiate tamoxifen. Selective depletion of HDAC2 resulted in simultaneous depletion of ER and PR, and potentiated the effects of antihormonal therapy in ER-positive cells. A more effective pharmacologic inhibition of HDAC2 and evaluation of HDAC2 and PR as therapeutic targets or as predictive markers in hormonal therapy may be considered when combining HDAC inhibitors and hormonal therapy.
The molecular chaperone heat shock protein 90 (Hsp90) and its accessory cochaperones function by facilitating the structural maturation and complex assembly of client proteins, including steroid hormone receptors and selected kinases. By promoting the activity and stability of these signaling proteins, Hsp90 has emerged as a critical modulator in cell signaling. Here, we present evidence that Hsp90 chaperone activity is regulated by reversible acetylation and controlled by the deacetylase HDAC6. We show that HDAC6 functions as an Hsp90 deacetylase. Inactivation of HDAC6 leads to Hsp90 hyperacetylation, its dissociation from an essential cochaperone, p23, and a loss of chaperone activity. In HDAC6-deficient cells, Hsp90-dependent maturation of the glucocorticoid receptor (GR) is compromised, resulting in GR defective in ligand binding, nuclear translocation, and transcriptional activation. Our results identify Hsp90 as a target of HDAC6 and suggest reversible acetylation as a unique mechanism that regulates Hsp90 chaperone complex activity.
The aryl hydrocarbon receptor (AhR), a ligand-activated member of the basic helix-loop-helix family of transcription factors, binds with high affinity to polycyclic aromatic hydrocarbons (PAH) and the environmental toxin 2,3,7,8-tetrachlorodibenzo-p-dioxin (dioxin). Most of the biochemical, biological, and toxicological responses caused by exposure to PAHs and polychlorinated dioxins are mediated, at least in part, by the AhR. The AhR is a client protein of Hsp90, a molecular chaperone that can be reversibly acetylated with functional consequences. The main objective of this study was to determine whether modulating Hsp90 acetylation would affect ligand-mediated activation of AhR signaling. Trichostatin A and suberoylanilide hydroxamic acid, two broad spectrum HDAC inhibitors, blocked PAH and dioxin-mediated induction of CYP1A1 and CYP1B1 in cell lines derived from the human aerodigestive tract. Silencing HDAC6 or treatment with tubacin, a pharmacological inhibitor of HDAC6, also suppressed the induction of CYP1A1 and CYP1B1. Inhibiting HDAC6 led to hyperacetylation of Hsp90 and loss of complex formation with AhR, cochaperone p23, and XAP-2. Inactivation or silencing of HDAC6 also led to reduced binding of ligand to the AhR and decreased translocation of the AhR from cytosol to nucleus in response to ligand. Ligand-induced recruitment of the AhR to the CYP1A1 and CYP1B1 promoters was inhibited when HDAC6 was inactivated. Mutation analysis of Hsp90 Lys(294) shows that its acetylation status is a strong determinant of interactions with AhR and p23 in addition to ligand-mediated activation of AhR signaling. Collectively, these results show that HDAC6 activity regulates the acetylation of Hsp90, the ability of Hsp90 to chaperone the AhR, and the expression of AhR-dependent genes. Given the established link between activation of AhR signaling and xenobiotic metabolism, inhibitors of HDAC6 may alter drug or carcinogen metabolism.
The disaggregation of a protein complex into its constituent components. Protein complexes may have other associated non-protein prosthetic groups, such as nucleic acids, metal ions or carbohydrate groups.
The molecular chaperone heat shock protein 90 (Hsp90) and its accessory cochaperones function by facilitating the structural maturation and complex assembly of client proteins, including steroid hormone receptors and selected kinases. By promoting the activity and stability of these signaling proteins, Hsp90 has emerged as a critical modulator in cell signaling. Here, we present evidence that Hsp90 chaperone activity is regulated by reversible acetylation and controlled by the deacetylase HDAC6. We show that HDAC6 functions as an Hsp90 deacetylase. Inactivation of HDAC6 leads to Hsp90 hyperacetylation, its dissociation from an essential cochaperone, p23, and a loss of chaperone activity. In HDAC6-deficient cells, Hsp90-dependent maturation of the glucocorticoid receptor (GR) is compromised, resulting in GR defective in ligand binding, nuclear translocation, and transcriptional activation. Our results identify Hsp90 as a target of HDAC6 and suggest reversible acetylation as a unique mechanism that regulates Hsp90 chaperone complex activity.
Androgen receptor (AR) is a ligand-activated transcription factor belonging to the steroid hormone receptor family and is very important for the development and progression of prostate cancer. The soy isoflavone genistein has been shown previously to down-regulate AR in androgen-dependent prostate cancer cell lines such as LNCaP. However, the mechanism(s) by which AR is down-regulated by genistein is still not known fully. We show a new mechanism by which genistein inhibits AR protein levels. We show that genistein-treated LNCaP cells exhibit increased ubiquitination of AR, suggesting that AR protein is down-regulated via a proteasome-mediated pathway. AR is normally stabilized by the chaperone activity of the heat shock protein Hsp90. The increased ubiquitination of AR after genistein treatment is attributed to decreased Hsp90 chaperone activity as assessed by its increased functionally inactive acetylated form. Consistent with this result, we find that HDAC6, which is a Hsp90 deacetylase, is inhibited by the antiestrogenic activity of genistein. Hence, in this study, we elucidate a novel mechanism of AR down-regulation by genistein through inhibition of HDAC6-Hsp90 cochaperone function required to stabilize AR protein. Our results suggest that genistein could be used as a potential chemopreventive agent for prostate cancers along with known inhibitors of HDAC6 and Hsp90.
Any process that modulates the rate, frequency, or extent of microtubule-based movement, the movement of organelles, other microtubules and other particles along microtubules, mediated by motor proteins.
The cytoplasmic deacetylase HDAC6 is an important regulator of cellular pathways that include response to stress, protein folding, microtubule stability, and cell migration, thus representing an attractive target for cancer chemotherapy. However, little is known about its upstream regulation. Our previous work has implicated HDAC6 as a new protein target for the farnesyltransferase inhibitors (FTIs), although HDAC6 lacks a farnesylation motif. Here we show that the protein farnesyltransferase (FTase) and HDAC6 are present in a protein complex together with microtubules in vivo and in vitro. FTase binds microtubules directly via its alpha subunit, and this association requires the C terminus of tubulin. Treatment with an FTI removed FTase, but not HDAC6, from the protein complex, suggesting that the active form of FTase is bound to microtubules. Importantly, the removal of FTase from microtubules abrogated HDAC6 activity, as did a stable knockdown of the alpha subunit of FTase (FTalphaKD). Interestingly, the FTalphaKD cells showed increased sensitivity to the antiproliferative effects of Taxol and the FTI lonafarnib when used either as single agents or in combination as compared with parental cells. Altogether, these data suggest that FTase, via its tubulin-association, is a critical upstream regulator of HDAC6 activity and that FTase expression could help stratify cancer patients that would most benefit from this treatment.
Any process that modulates the frequency, rate or extent of receptor activity. Receptor activity is when a molecule combines with an extracellular or intracellular messenger to initiate a change in cell activity.
The aryl hydrocarbon receptor (AhR), a ligand-activated member of the basic helix-loop-helix family of transcription factors, binds with high affinity to polycyclic aromatic hydrocarbons (PAH) and the environmental toxin 2,3,7,8-tetrachlorodibenzo-p-dioxin (dioxin). Most of the biochemical, biological, and toxicological responses caused by exposure to PAHs and polychlorinated dioxins are mediated, at least in part, by the AhR. The AhR is a client protein of Hsp90, a molecular chaperone that can be reversibly acetylated with functional consequences. The main objective of this study was to determine whether modulating Hsp90 acetylation would affect ligand-mediated activation of AhR signaling. Trichostatin A and suberoylanilide hydroxamic acid, two broad spectrum HDAC inhibitors, blocked PAH and dioxin-mediated induction of CYP1A1 and CYP1B1 in cell lines derived from the human aerodigestive tract. Silencing HDAC6 or treatment with tubacin, a pharmacological inhibitor of HDAC6, also suppressed the induction of CYP1A1 and CYP1B1. Inhibiting HDAC6 led to hyperacetylation of Hsp90 and loss of complex formation with AhR, cochaperone p23, and XAP-2. Inactivation or silencing of HDAC6 also led to reduced binding of ligand to the AhR and decreased translocation of the AhR from cytosol to nucleus in response to ligand. Ligand-induced recruitment of the AhR to the CYP1A1 and CYP1B1 promoters was inhibited when HDAC6 was inactivated. Mutation analysis of Hsp90 Lys(294) shows that its acetylation status is a strong determinant of interactions with AhR and p23 in addition to ligand-mediated activation of AhR signaling. Collectively, these results show that HDAC6 activity regulates the acetylation of Hsp90, the ability of Hsp90 to chaperone the AhR, and the expression of AhR-dependent genes. Given the established link between activation of AhR signaling and xenobiotic metabolism, inhibitors of HDAC6 may alter drug or carcinogen metabolism.
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 growth factor stimulus.
Nuclear translocation of beta-catenin is a hallmark of Wnt signaling and is associated with various cancers. In addition to the canonical Wnt pathway activated by Wnt ligands, growth factors such as epidermal growth factor (EGF) also induce beta-catenin dissociation from the adherens junction complex, translocation into the nucleus, and activation of target genes such as c-myc. Here we report that EGF-induced beta-catenin nuclear localization and activation of c-myc are dependent on the deacetylase HDAC6. We show that EGF induces HDAC6 translocation to the caveolae membrane and association with beta-catenin. HDAC6 deacetylates beta-catenin at lysine 49, a site frequently mutated in anaplastic thyroid cancer, and inhibits beta-catenin phosphorylation at serine 45. HDAC6 inactivation blocks EGF-induced beta-catenin nuclear localization and decreases c-Myc expression, leading to inhibition of tumor cell proliferation. These results suggest that EGF-induced nuclear localization of beta-catenin is regulated by HDAC6-dependent deacetylation and provide a new mechanism by which HDAC inhibitors prevent tumor growth.
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 misfolded protein stimulus.
The efficient clearance of cytotoxic misfolded protein aggregates is critical for cell survival. Misfolded protein aggregates are transported and removed from the cytoplasm by dynein motors via the microtubule network to a novel organelle termed the aggresome where they are processed. However, the means by which dynein motors recognize misfolded protein cargo, and the cellular factors that regulate aggresome formation, remain unknown. We have discovered that HDAC6, a microtubule-associated deacetylase, is a component of the aggresome. We demonstrate that HDAC6 has the capacity to bind both polyubiquitinated misfolded proteins and dynein motors, thereby acting to recruit misfolded protein cargo to dynein motors for transport to aggresomes. Indeed, cells deficient in HDAC6 fail to clear misfolded protein aggregates from the cytoplasm, cannot form aggresomes properly, and are hypersensitive to the accumulation of misfolded proteins. These findings identify HDAC6 as a crucial player in the cellular management of misfolded protein-induced stress.
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 organic substance stimulus.
The aryl hydrocarbon receptor (AhR), a ligand-activated member of the basic helix-loop-helix family of transcription factors, binds with high affinity to polycyclic aromatic hydrocarbons (PAH) and the environmental toxin 2,3,7,8-tetrachlorodibenzo-p-dioxin (dioxin). Most of the biochemical, biological, and toxicological responses caused by exposure to PAHs and polychlorinated dioxins are mediated, at least in part, by the AhR. The AhR is a client protein of Hsp90, a molecular chaperone that can be reversibly acetylated with functional consequences. The main objective of this study was to determine whether modulating Hsp90 acetylation would affect ligand-mediated activation of AhR signaling. Trichostatin A and suberoylanilide hydroxamic acid, two broad spectrum HDAC inhibitors, blocked PAH and dioxin-mediated induction of CYP1A1 and CYP1B1 in cell lines derived from the human aerodigestive tract. Silencing HDAC6 or treatment with tubacin, a pharmacological inhibitor of HDAC6, also suppressed the induction of CYP1A1 and CYP1B1. Inhibiting HDAC6 led to hyperacetylation of Hsp90 and loss of complex formation with AhR, cochaperone p23, and XAP-2. Inactivation or silencing of HDAC6 also led to reduced binding of ligand to the AhR and decreased translocation of the AhR from cytosol to nucleus in response to ligand. Ligand-induced recruitment of the AhR to the CYP1A1 and CYP1B1 promoters was inhibited when HDAC6 was inactivated. Mutation analysis of Hsp90 Lys(294) shows that its acetylation status is a strong determinant of interactions with AhR and p23 in addition to ligand-mediated activation of AhR signaling. Collectively, these results show that HDAC6 activity regulates the acetylation of Hsp90, the ability of Hsp90 to chaperone the AhR, and the expression of AhR-dependent genes. Given the established link between activation of AhR signaling and xenobiotic metabolism, inhibitors of HDAC6 may alter drug or carcinogen metabolism.
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 toxin stimulus.
The aryl hydrocarbon receptor (AhR), a ligand-activated member of the basic helix-loop-helix family of transcription factors, binds with high affinity to polycyclic aromatic hydrocarbons (PAH) and the environmental toxin 2,3,7,8-tetrachlorodibenzo-p-dioxin (dioxin). Most of the biochemical, biological, and toxicological responses caused by exposure to PAHs and polychlorinated dioxins are mediated, at least in part, by the AhR. The AhR is a client protein of Hsp90, a molecular chaperone that can be reversibly acetylated with functional consequences. The main objective of this study was to determine whether modulating Hsp90 acetylation would affect ligand-mediated activation of AhR signaling. Trichostatin A and suberoylanilide hydroxamic acid, two broad spectrum HDAC inhibitors, blocked PAH and dioxin-mediated induction of CYP1A1 and CYP1B1 in cell lines derived from the human aerodigestive tract. Silencing HDAC6 or treatment with tubacin, a pharmacological inhibitor of HDAC6, also suppressed the induction of CYP1A1 and CYP1B1. Inhibiting HDAC6 led to hyperacetylation of Hsp90 and loss of complex formation with AhR, cochaperone p23, and XAP-2. Inactivation or silencing of HDAC6 also led to reduced binding of ligand to the AhR and decreased translocation of the AhR from cytosol to nucleus in response to ligand. Ligand-induced recruitment of the AhR to the CYP1A1 and CYP1B1 promoters was inhibited when HDAC6 was inactivated. Mutation analysis of Hsp90 Lys(294) shows that its acetylation status is a strong determinant of interactions with AhR and p23 in addition to ligand-mediated activation of AhR signaling. Collectively, these results show that HDAC6 activity regulates the acetylation of Hsp90, the ability of Hsp90 to chaperone the AhR, and the expression of AhR-dependent genes. Given the established link between activation of AhR signaling and xenobiotic metabolism, inhibitors of HDAC6 may alter drug or carcinogen metabolism.
The cytoplasmic deacetylase HDAC6 is an important regulator of cellular pathways that include response to stress, protein folding, microtubule stability, and cell migration, thus representing an attractive target for cancer chemotherapy. However, little is known about its upstream regulation. Our previous work has implicated HDAC6 as a new protein target for the farnesyltransferase inhibitors (FTIs), although HDAC6 lacks a farnesylation motif. Here we show that the protein farnesyltransferase (FTase) and HDAC6 are present in a protein complex together with microtubules in vivo and in vitro. FTase binds microtubules directly via its alpha subunit, and this association requires the C terminus of tubulin. Treatment with an FTI removed FTase, but not HDAC6, from the protein complex, suggesting that the active form of FTase is bound to microtubules. Importantly, the removal of FTase from microtubules abrogated HDAC6 activity, as did a stable knockdown of the alpha subunit of FTase (FTalphaKD). Interestingly, the FTalphaKD cells showed increased sensitivity to the antiproliferative effects of Taxol and the FTI lonafarnib when used either as single agents or in combination as compared with parental cells. Altogether, these data suggest that FTase, via its tubulin-association, is a critical upstream regulator of HDAC6 activity and that FTase expression could help stratify cancer patients that would most benefit from this treatment.
Ubiquitin-dependent protein catabolic process via the multivesicular body sorting pathwaydefinition[GO:0043162]‹silver
The chemical reactions and pathways resulting in the breakdown of a protein or peptide covalently tagged with ubiquitin, via the multivesicular body (MVB) sorting pathway; ubiquitin-tagged proteins are sorted into MVBs, and delivered to a lysosome/vacuole for degradation.
IEAOrtholog Compara
Enzymatic activity
This protein acts as an enzyme. It is known to catalyze the following reaction
EC 3.5.1.98: Hydrolysis of an N(6)-acetyl-lysine residue of a histone to yield a deacetylated histone.
Protein participating in autophagy, a process of intracellular bulk degradation in which cytoplasmic components including organelles are sequestered within double-membrane vesicles that deliver the contents to the lysosome/vacuole for degradation. There are three primary forms of autophagy: chaperone-mediated autophagy, microautophagy and macroautophagy. During macroautophagy, the sequestering vesicles, termed autophagosomes, fuse with the lysosome or vacuole resulting in the delivery of an inner vesicle (autophagic body) into the lumen of the degradative compartment.
Protein involved in the transfer of genetic information from DNA to messenger RNA (mRNA) by DNA-directed RNA polymerase. In the case of some RNA viruses, protein involved in the transfer of genetic information from RNA to messenger RNA (mRNA) by RNA-directed RNA polymerase.
Enzyme which catalyzes hydrolysis reaction, i.e. the addition of the hydrogen and hydroxyl ions of water to a molecule with its consequent splitting into two or more simpler molecules.
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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