During conditions of moderate sodium excess, the dopaminergic system regulates blood pressure and water and electrolyte balance by engendering natriuresis. Dopamine exerts its effects on dopamine receptors, including the dopamine D(3) receptor. G protein-coupled receptor kinase 4 (GRK4), whose gene locus (4p16.3) is linked to essential hypertension, desensitizes the D(1) receptor, another dopamine receptor. This study evaluated the role of GRK4 on D(3) receptor function in human proximal tubule cells. D(3) receptor co-segregated in lipid rafts and co-immunoprecipitated and co-localized in human proximal tubule cells and in proximal and distal tubules and glomeruli of kidneys of Wistar Kyoto rats. Bimolecular fluorescence complementation and confocal microscopy revealed that agonist activation of the receptor initiated the interaction between D(3) receptor and GRK4 at the cell membrane and promoted it intracellularly, presumably en route to endosomal trafficking. Of the four GRK4 splice variants, GRK4-gamma and GRK4-alpha mediated a 3- and 2-fold increase in the phosphorylation of agonist-activated D(3) receptor, respectively. Inhibition of GRK activity with heparin or knockdown of GRK4 expression via RNA interference completely abolished p44/42 phosphorylation and mitogenesis induced by D(3) receptor stimulation. These data demonstrate that GRK4, specifically the GRK4-gamma and GRK4-alpha isoforms, phosphorylates the D(3) receptor and is crucial for its signaling in human proximal tubule cells.
Interacting selectively and non-covalently with dopamine, a catecholamine neurotransmitter formed by aromatic-L-amino-acid decarboxylase from 3,4-dihydroxy-L-phenylalanine.
J. Pharmacol. Exp. Ther. 268, 417-426 (1994)[PubMed:8301582]
Binding of dopamine receptor ligands to human D2 and D3 receptors was characterized in Chinese hamster ovary (CHO) cells using the dopamine D2 receptor antagonist [125I] iodosulpiride. Only limited binding selectivity was observed for known dopamine D2 receptor antagonists from a variety of chemical classes, which included haloperidol, chlorpromazine, sulpiride, pimozide and cis flupenthixol. The most selective compound from this group were (+)butaclamol and domperidone which showed 5-fold D3 selectivity. A number of high affinity dopamine receptor agonists, including apomorphine and bromocriptine, also failed to demonstrate selectivity. In contrast, the natural ligand dopamine and the efficacious synthetic agonists quinpirole, (+)4-propyl-9-hydroxynapthoxazine (PHNO), 2-amino-6,7-dihydroxy-1,2,3,4-tetrahydronaphthalene (6,7-ADTN), 7-OH DPAT and N-0434 showed marked apparent human dopamine D3 (hD3) receptor selectivity. In the aminotetralin series, this selectivity was observed preferentially with analogs of the 6,7-rotamer compared with compounds from the 5,6-rotamer series. Functional coupling of the hD3 receptor was investigated in a number of cell lines in which the hD3 receptor was stably expressed, including CHO cells, the neuroblastoma-glioma hybrid cell line NG108-15 and a rat 1 fibroblast cell line. There was no evidence of functional coupling of the hD3 receptor to adenylate cyclase, arachidonic acid release, phospholipase C activation, K+ currents or calcium mobilization in any of the cell lines examined. Furthermore, guanine nucleotides failed to inhibit the binding of [3H] N-0437 to hD3 receptors in any of the three cell lines. There may be a number of explanations for these results. These cell lines may not have the appropriate G-protein or secondary messenger systems that are coupled to the hD3 receptor in situ. Alternatively, this receptor may couple by a mechanism that is as yet undefined. The finding that a wide range of structurally diverse human dopamine D2 (hD2) receptor agonists have an apparent hD3 selectivity may imply that the hD3 receptor exists predominantly in a high affinity state.
Interacting selectively and non-covalently with a drug, any naturally occurring or synthetic substance, other than a nutrient, that, when administered or applied to an organism, affects the structure or functioning of the organism; in particular, any such substance used in the diagnosis, prevention, or treatment of disease.
Although the biological basis of schizophrenia is not known, possible causes include genetic defects, viruses, amines, brain structure and metabolism, neuroreceptors, and G proteins. The hypothesis of dopamine overactivity in schizophrenia is based on the fact that neuroleptics block dopamine D2 receptors in direct relation to their clinical antipsychotic potencies. Moreover, dopamine D2 or D2-like receptors are elevated in postmortem schizophrenia brain tissue. This elevation, however, is only found in vivo using [11C]methylspiperone but not [11C]raclopride. The dopamine D4 receptor gene has not yet been excluded in schizophrenia because the 21 gene variants of D4 have not yet been tested. Because the link between D1 and D2 receptors is reduced in schizophrenia tissue, we tested whether one component of this link was sensitive to guanine nucleotide. We report here that the binding of [3H]raclopride to D2 receptors in schizophrenia was not sensitive to guanine nucleotide. This finding permitted analysis of data on the binding of [3H]emonapride to the D2, D3 and D4 receptors. We conclude that the combined density of D2 and D3 receptors (labelled by [3H]raclopride) is increased by only 10% in schizophrenia brain, as found by Farde et al., but that it is the density of dopamine D4 receptors which is sixfold elevated in schizophrenia. These findings resolve the apparent discrepancy, mentioned above, wherein the density of [11C]methylspiperone-labelled sites (D2, D3 and D4), but not that of [11C]raclopride-labelled sites (D2 and D3), was found elevated in the schizophrenia striatum.
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 InteractionBHF-UCL
Proteins that bind to G protein-coupled receptors have recently been identified as regulators of receptor anchoring and signaling. In this study, actin-binding protein 280 (ABP-280), a widely expressed cytoskeleton-associated protein that plays an important role in regulating cell morphology and motility, was found to associate with the third cytoplasmic loop of dopamine D(2) receptors. The specificity of this interaction was originally identified in a yeast two-hybrid screen and confirmed by protein binding. The functional significance of the D(2) receptor-ABP-280 association was evaluated in human melanoma cells lacking ABP-280. D(2) receptor agonists were less potent in inhibiting forskolin-stimulated cAMP production in these cells. Maximal inhibitory responses of D(2) receptor activation were also reduced. Further yeast two-hybrid experiments showed that ABP-280 association is critically dependent on the carboxyl domain of the D(2) receptor third cytoplasmic loop, where there is a potential serine phosphorylation site (S358). Serine 358 was replaced with aspartic acid to mimic the effects of receptor phosphorylation. This mutant (D(2)S358D) displayed compromised binding to ABP-280 and coupling to adenylate cyclase. PKC activation also generated D(2) receptor signaling attenuation, but only in ABP-containing cells, suggesting a PKC regulatory role in D(2)-ABP association. A mechanism for these results may be derived from a role of ABP-280 in the clustering of D(2) receptors, as determined by immunocytochemical analysis in ABP-deficient and replete cells. Our results suggest a new molecular mechanism of modulating D(2) receptor signaling by cytoskeletal protein interaction.
Evidence
2:
Inferred from Physical InteractionUniProtKB
Paralemmin is a novel lipid-anchored protein, which is highly expressed in neuronal plasma membranes. In this study, we demonstrate that paralemmin specifically interacts with the third intracellular loop of the D3 dopamine receptor. Utilizing co-immunoprecipitation and glutathione-S-transferase (GST) pulldown strategies, we demonstrate that paralemmin interacts exclusively with D3, but not D2 or D4 dopamine receptors or beta-adrenergic receptors. Immunocytochemistry demonstrated co-localization of paralemmin and D3 receptor in vivo in hippocampus and cerebellum and in vitro in glial and neuronal cultures. Deletion mutational analysis indicates that amino acids 154-230 of paralemmin strongly interacted with amino acids 211-227 and 281-330 of the third intracellular loop of D3 receptor. The consequences of these interactions were investigated by co-expression in HEK293 cells. Cell surface biotinylation experiments demonstrate that paralemmin decreased D3 receptor concentration at the plasma membrane. Consistent with this observation, paralemmin expression decreased dopamine-stimulated adenylate cyclase activity. However, paralemmin also decreased basal, isoproterenol and forskolin-stimulated adenylate cyclase activity, suggesting a more general cellular function for paralemmin. Taken together, paralemmin has been implicated as a potent modulator of cellular cAMP signaling within the brain.
Evidence
3:
Inferred from Physical InteractionBHF-UCL
Colocalization of dopamine D1 (D1R) and D3 receptors (D3R) in specific neuronal populations suggests that their functional cross-talk might involve direct interactions. Here we report that the D1R coimmunoprecipitates with the D3R from striatal protein preparations, suggesting that they are clustered together in this region. Using bioluminescence resonance energy transfer (BRET(2)), we further suggest the existence of a physical interaction between D1R and D3R. Tagged D1R and D3R cotransfected in human embryonic kidney (HEK) 293 cells generated a significant BRET(2) signal that was insensitive to agonist stimulation, suggesting that they form a constitutive heterodimer. D1R and D3R regulate adenylyl cyclase (AC) in opposite ways. In HEK 293 cells coexpressing D1R and D3R, dopamine stimulated AC with higher potency and displaced [3H]R-(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine (SCH23390) binding with higher affinity than in cells expressing the D1R. In HEK 293 cells individually expressing D1R or D3R, agonist stimulation induces internalization of D1R but not of D3R. Heterodimerization with D3R abolishes agonist-induced D1R cytoplasmic sequestration induced by selective D1R agonists and enables internalization of the D1R/D3R complex in response to the paired stimulation of both D1R and D3R. This mechanism involves beta-arrestin binding because it was blocked by mutant beta-arrestinV53D. These data suggest that as a result of dimerization, the D3R is switched to the desensitization mechanisms typical of the D1R. These data give a novel insight into how D1R and D3R may function in an integrated way, providing a molecular mechanism by which to converge D1R- and D3R-related dysfunctions.
The series of molecular signals generated as a consequence of a dopamine receptor binding to its physiological ligand, where the pathway proceeds with activation of adenylyl cyclase and a subsequent increase in the concentration of cyclic AMP (cAMP).
Colocalization of dopamine D1 (D1R) and D3 receptors (D3R) in specific neuronal populations suggests that their functional cross-talk might involve direct interactions. Here we report that the D1R coimmunoprecipitates with the D3R from striatal protein preparations, suggesting that they are clustered together in this region. Using bioluminescence resonance energy transfer (BRET(2)), we further suggest the existence of a physical interaction between D1R and D3R. Tagged D1R and D3R cotransfected in human embryonic kidney (HEK) 293 cells generated a significant BRET(2) signal that was insensitive to agonist stimulation, suggesting that they form a constitutive heterodimer. D1R and D3R regulate adenylyl cyclase (AC) in opposite ways. In HEK 293 cells coexpressing D1R and D3R, dopamine stimulated AC with higher potency and displaced [3H]R-(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine (SCH23390) binding with higher affinity than in cells expressing the D1R. In HEK 293 cells individually expressing D1R or D3R, agonist stimulation induces internalization of D1R but not of D3R. Heterodimerization with D3R abolishes agonist-induced D1R cytoplasmic sequestration induced by selective D1R agonists and enables internalization of the D1R/D3R complex in response to the paired stimulation of both D1R and D3R. This mechanism involves beta-arrestin binding because it was blocked by mutant beta-arrestinV53D. These data suggest that as a result of dimerization, the D3R is switched to the desensitization mechanisms typical of the D1R. These data give a novel insight into how D1R and D3R may function in an integrated way, providing a molecular mechanism by which to converge D1R- and D3R-related dysfunctions.
The series of molecular signals generated as a consequence of a dopamine receptor binding to its physiological ligand, where the pathway proceeds with inhibition of adenylyl cyclase and a subsequent decrease in the concentration of cyclic AMP (cAMP).
Colocalization of dopamine D1 (D1R) and D3 receptors (D3R) in specific neuronal populations suggests that their functional cross-talk might involve direct interactions. Here we report that the D1R coimmunoprecipitates with the D3R from striatal protein preparations, suggesting that they are clustered together in this region. Using bioluminescence resonance energy transfer (BRET(2)), we further suggest the existence of a physical interaction between D1R and D3R. Tagged D1R and D3R cotransfected in human embryonic kidney (HEK) 293 cells generated a significant BRET(2) signal that was insensitive to agonist stimulation, suggesting that they form a constitutive heterodimer. D1R and D3R regulate adenylyl cyclase (AC) in opposite ways. In HEK 293 cells coexpressing D1R and D3R, dopamine stimulated AC with higher potency and displaced [3H]R-(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine (SCH23390) binding with higher affinity than in cells expressing the D1R. In HEK 293 cells individually expressing D1R or D3R, agonist stimulation induces internalization of D1R but not of D3R. Heterodimerization with D3R abolishes agonist-induced D1R cytoplasmic sequestration induced by selective D1R agonists and enables internalization of the D1R/D3R complex in response to the paired stimulation of both D1R and D3R. This mechanism involves beta-arrestin binding because it was blocked by mutant beta-arrestinV53D. These data suggest that as a result of dimerization, the D3R is switched to the desensitization mechanisms typical of the D1R. These data give a novel insight into how D1R and D3R may function in an integrated way, providing a molecular mechanism by which to converge D1R- and D3R-related dysfunctions.
Functional characteristics of human D2 and D3 receptors (DRs) were examined using a new bioassay suited for the study of Gi-protein-coupled receptors (GiRs). The bioassay utilizes pigment granule aggregation within cultured Xenopus laevis melanophores for the quantitative evaluation of ligands as agonists or antagonists upon particular GiRs. Initial feasibility studies were performed by analyzing a melanocyte receptor endogenous to the melanophores. In dose-dependent manners, melatonin inhibited melatonin-stimulating hormone-induced cAMP accumulation and caused pigment aggregation that could be monitored over time. Next, melanophores were transiently transfected with cDNAs coding for the human D2BR (short form) and D3R. Expression of either receptor conferred upon the cells the ability to aggregate their melanosomes in response to selective dopaminergic agonists. The same ligands also inhibited cAMP accumulation within the transfected melanophores, and the agonist-induced pigment aggregation was shown to be sensitive to pertussis toxin. EC50 and IC50 value determinations revealed that agonists activated the D2R and D3R at similar concentrations, while each of the antagonists displaying an effect was more potent upon the D2R. The results reveal functional similarities and differences between the D2R and D3R.
J. Pharmacol. Exp. Ther. 268, 417-426 (1994)[PubMed:8301582]
Binding of dopamine receptor ligands to human D2 and D3 receptors was characterized in Chinese hamster ovary (CHO) cells using the dopamine D2 receptor antagonist [125I] iodosulpiride. Only limited binding selectivity was observed for known dopamine D2 receptor antagonists from a variety of chemical classes, which included haloperidol, chlorpromazine, sulpiride, pimozide and cis flupenthixol. The most selective compound from this group were (+)butaclamol and domperidone which showed 5-fold D3 selectivity. A number of high affinity dopamine receptor agonists, including apomorphine and bromocriptine, also failed to demonstrate selectivity. In contrast, the natural ligand dopamine and the efficacious synthetic agonists quinpirole, (+)4-propyl-9-hydroxynapthoxazine (PHNO), 2-amino-6,7-dihydroxy-1,2,3,4-tetrahydronaphthalene (6,7-ADTN), 7-OH DPAT and N-0434 showed marked apparent human dopamine D3 (hD3) receptor selectivity. In the aminotetralin series, this selectivity was observed preferentially with analogs of the 6,7-rotamer compared with compounds from the 5,6-rotamer series. Functional coupling of the hD3 receptor was investigated in a number of cell lines in which the hD3 receptor was stably expressed, including CHO cells, the neuroblastoma-glioma hybrid cell line NG108-15 and a rat 1 fibroblast cell line. There was no evidence of functional coupling of the hD3 receptor to adenylate cyclase, arachidonic acid release, phospholipase C activation, K+ currents or calcium mobilization in any of the cell lines examined. Furthermore, guanine nucleotides failed to inhibit the binding of [3H] N-0437 to hD3 receptors in any of the three cell lines. There may be a number of explanations for these results. These cell lines may not have the appropriate G-protein or secondary messenger systems that are coupled to the hD3 receptor in situ. Alternatively, this receptor may couple by a mechanism that is as yet undefined. The finding that a wide range of structurally diverse human dopamine D2 (hD2) receptor agonists have an apparent hD3 selectivity may imply that the hD3 receptor exists predominantly in a high affinity state.
The mesolimbic dopaminergic system plays a primary role in mediating the euphoric and rewarding effects of most abused drugs. Chronic cocaine use is associated with an increase in dopamine neurotransmission resulting from the blockade of dopamine uptake and is mediated by the activation of dopamine receptors. Recent studies have suggested that the D3 receptor subtype plays a pivotal role in the reinforcing effects of cocaine. The D3 receptor-preferring agonist 7-hydroxy-N,N-di-n-propyl-2-aminotetralin (7-OH-DPAT) is a reinforcer in rhesus monkeys trained to self-administer cocaine, but not in cocainenaive monkeys. In vitro autoradiographic localization of [3H]-(+)-7-OH-DPAT binding in the human brain demonstrated that D3 receptors were prevalent and highly localized over the ventromedial sectors of the striatum. Pharmacological characterization of [3H]-(+)-7-OH-DPAT binding to the human nucleus accumbens demonstrated a rank order of potency similar to that observed for binding to the cloned D3 receptor expressed in transfected cell lines. Region-of-interest analysis of [3H]-(+)-7-OH-DPAT binding to the D3 receptor demonstrated a one- to threefold elevation in the number of binding sites over particular sectors of the striatum and substantia nigra in cocaine overdose victims as compared with age-matched and drug-free control subjects. The elevated number of [3H]-(+)-7-OH-DPAT binding sites demonstrates that adaptive changes in the D3 receptor in the reward circuitry of the brain are associated with chronic cocaine abuse. These results suggest that the D3 receptor may be a useful target for drug development of anticocaine medications.
Br. J. Pharmacol. 111, 391-393 (1994)[PubMed:7911712]
This study describes the depression of calcium currents caused by activation of human D3 dopamine receptors which have been stably expressed in the neuroblastoma x glioma NG108-15 cell line. Transfected cells, which had been differentiated with prostaglandin E1 and isobutylmethylxanthine, exclusively expressed D3 receptor mRNA, which was demonstrated by reverse transcription polymerase chain reaction techniques. Transfected cells had high affinity binding sites for iodosulpiride, with a Kd of 0.8 nM and receptor density of 240 fmol mg-1 protein. Calcium currents were recorded using nystatin-perforated patch clamp techniques. In contrast to untransfected cells that had been differentiated, high-threshold calcium currents in differentiated hD3-NG108-15 cells were depressed by application of dopamine and quinpirole. These responses were abolished by the dopamine receptor antagonist S-(-)-sulpiride (1 microM), demonstrating that they were caused by the activation of the transfected dopamine receptors. Coupling of human D3 receptors to calcium currents was sensitive to the action of pertussis toxin, suggesting the involvement of G-proteins of the Gi and/or G(o) subtype. These results demonstrate that human D3 receptors represent a functional class of dopamine receptor.
Any process that modulates the frequency, rate or extent of gene expression such that an expression pattern recurs with a regularity of approximately 24 hours.
J. Pharmacol. Exp. Ther. 268, 417-426 (1994)[PubMed:8301582]
Binding of dopamine receptor ligands to human D2 and D3 receptors was characterized in Chinese hamster ovary (CHO) cells using the dopamine D2 receptor antagonist [125I] iodosulpiride. Only limited binding selectivity was observed for known dopamine D2 receptor antagonists from a variety of chemical classes, which included haloperidol, chlorpromazine, sulpiride, pimozide and cis flupenthixol. The most selective compound from this group were (+)butaclamol and domperidone which showed 5-fold D3 selectivity. A number of high affinity dopamine receptor agonists, including apomorphine and bromocriptine, also failed to demonstrate selectivity. In contrast, the natural ligand dopamine and the efficacious synthetic agonists quinpirole, (+)4-propyl-9-hydroxynapthoxazine (PHNO), 2-amino-6,7-dihydroxy-1,2,3,4-tetrahydronaphthalene (6,7-ADTN), 7-OH DPAT and N-0434 showed marked apparent human dopamine D3 (hD3) receptor selectivity. In the aminotetralin series, this selectivity was observed preferentially with analogs of the 6,7-rotamer compared with compounds from the 5,6-rotamer series. Functional coupling of the hD3 receptor was investigated in a number of cell lines in which the hD3 receptor was stably expressed, including CHO cells, the neuroblastoma-glioma hybrid cell line NG108-15 and a rat 1 fibroblast cell line. There was no evidence of functional coupling of the hD3 receptor to adenylate cyclase, arachidonic acid release, phospholipase C activation, K+ currents or calcium mobilization in any of the cell lines examined. Furthermore, guanine nucleotides failed to inhibit the binding of [3H] N-0437 to hD3 receptors in any of the three cell lines. There may be a number of explanations for these results. These cell lines may not have the appropriate G-protein or secondary messenger systems that are coupled to the hD3 receptor in situ. Alternatively, this receptor may couple by a mechanism that is as yet undefined. The finding that a wide range of structurally diverse human dopamine D2 (hD2) receptor agonists have an apparent hD3 selectivity may imply that the hD3 receptor exists predominantly in a high affinity state.
Colocalization of dopamine D1 (D1R) and D3 receptors (D3R) in specific neuronal populations suggests that their functional cross-talk might involve direct interactions. Here we report that the D1R coimmunoprecipitates with the D3R from striatal protein preparations, suggesting that they are clustered together in this region. Using bioluminescence resonance energy transfer (BRET(2)), we further suggest the existence of a physical interaction between D1R and D3R. Tagged D1R and D3R cotransfected in human embryonic kidney (HEK) 293 cells generated a significant BRET(2) signal that was insensitive to agonist stimulation, suggesting that they form a constitutive heterodimer. D1R and D3R regulate adenylyl cyclase (AC) in opposite ways. In HEK 293 cells coexpressing D1R and D3R, dopamine stimulated AC with higher potency and displaced [3H]R-(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine (SCH23390) binding with higher affinity than in cells expressing the D1R. In HEK 293 cells individually expressing D1R or D3R, agonist stimulation induces internalization of D1R but not of D3R. Heterodimerization with D3R abolishes agonist-induced D1R cytoplasmic sequestration induced by selective D1R agonists and enables internalization of the D1R/D3R complex in response to the paired stimulation of both D1R and D3R. This mechanism involves beta-arrestin binding because it was blocked by mutant beta-arrestinV53D. These data suggest that as a result of dimerization, the D3R is switched to the desensitization mechanisms typical of the D1R. These data give a novel insight into how D1R and D3R may function in an integrated way, providing a molecular mechanism by which to converge D1R- and D3R-related dysfunctions.
A series of molecular signals that proceeds with an activated receptor promoting the exchange of GDP for GTP on the alpha-subunit of an associated heterotrimeric G-protein complex. The GTP-bound activated alpha-G-protein then dissociates from the beta- and gamma-subunits to further transmit the signal within the cell. The pathway begins with receptor-ligand interaction, or for basal GPCR signaling the pathway begins with the receptor activating its G protein in the absence of an agonist, and ends with regulation of a downstream cellular process, e.g. transcription.
Br. J. Pharmacol. 111, 391-393 (1994)[PubMed:7911712]
This study describes the depression of calcium currents caused by activation of human D3 dopamine receptors which have been stably expressed in the neuroblastoma x glioma NG108-15 cell line. Transfected cells, which had been differentiated with prostaglandin E1 and isobutylmethylxanthine, exclusively expressed D3 receptor mRNA, which was demonstrated by reverse transcription polymerase chain reaction techniques. Transfected cells had high affinity binding sites for iodosulpiride, with a Kd of 0.8 nM and receptor density of 240 fmol mg-1 protein. Calcium currents were recorded using nystatin-perforated patch clamp techniques. In contrast to untransfected cells that had been differentiated, high-threshold calcium currents in differentiated hD3-NG108-15 cells were depressed by application of dopamine and quinpirole. These responses were abolished by the dopamine receptor antagonist S-(-)-sulpiride (1 microM), demonstrating that they were caused by the activation of the transfected dopamine receptors. Coupling of human D3 receptors to calcium currents was sensitive to the action of pertussis toxin, suggesting the involvement of G-proteins of the Gi and/or G(o) subtype. These results demonstrate that human D3 receptors represent a functional class of dopamine receptor.
In this study, the authors investigated the relationship between the Ser9Gly (SG) polymorphism of the dopamine D3 receptor (DRD3) and striatal habit learning in healthy controls and patients with schizophrenia. Participants were given the weather prediction task, during which probabilistic cue-response associations were learned for tarot cards and weather outcomes (rain or sunshine). In both healthy controls and patients with schizophrenia, participants with Ser9Ser (SS) genotype did not learn during the early phase of the task (1-50 trials), whereas participants with SG genotype did so. During the late phase of the task (51-100 trials), both participants with SS and SG genotype exhibited significant learning. Learning rate was normal in patients with schizophrenia. These results suggest that the DRD3 variant containing glycine is associated with more efficient striatal habit learning in healthy controls and patients with schizophrenia.
Molecular components of the dopaminergic system may play an important role in the pathophysiology of schizophrenia. In this study, we investigated the relationship of the Ser9Gly (S/G) polymorphism of the dopamine D3 receptor (DRD3) and the variable number of tandem repeats (VNTR) polymorphism of the dopamine transporter (DAT) with therapeutic response to atypical antipsychotics (clozapine, olanzapine, quetiapine, risperidone) and cognitive functions. No associations were found between the DRD3 and DAT polymorphisms and schizophrenia. The S/S genotype and the S allele were more frequent in the non-responder patients (n = 28) than in the group of responders (n = 47) (cut-off: >20-point improvement in Global Assessment of Functioning (GAF) scale). The patients with S/S genotype completed fewer categories and had more perseverative errors in the Wisconsin Card Sorting Test (WCST) compared with the S/G patients. The S/S and S/G patients did not differ in positive and negative symptoms, GAF scores, WCST failure to maintain set, and verbal learning. No differences in symptoms or WCST measures were observed in the patients with different DAT genotypes. These results suggest that the S/S genotype of the DRD3 is associated with worse therapeutic response and more severe executive dysfunctions in patients with schizophrenia.
The specific movement from place to place of an organism in response to external or internal stimuli. Locomotion of a whole organism in a manner dependent upon some combination of that organism's internal state and external conditions.
Involuntary movement caused by the application of a stimulus to an organism and a subsequent movement. The signal processing of this movement takes place in the spinal cord.
Functional characteristics of human D2 and D3 receptors (DRs) were examined using a new bioassay suited for the study of Gi-protein-coupled receptors (GiRs). The bioassay utilizes pigment granule aggregation within cultured Xenopus laevis melanophores for the quantitative evaluation of ligands as agonists or antagonists upon particular GiRs. Initial feasibility studies were performed by analyzing a melanocyte receptor endogenous to the melanophores. In dose-dependent manners, melatonin inhibited melatonin-stimulating hormone-induced cAMP accumulation and caused pigment aggregation that could be monitored over time. Next, melanophores were transiently transfected with cDNAs coding for the human D2BR (short form) and D3R. Expression of either receptor conferred upon the cells the ability to aggregate their melanosomes in response to selective dopaminergic agonists. The same ligands also inhibited cAMP accumulation within the transfected melanophores, and the agonist-induced pigment aggregation was shown to be sensitive to pertussis toxin. EC50 and IC50 value determinations revealed that agonists activated the D2R and D3R at similar concentrations, while each of the antagonists displaying an effect was more potent upon the D2R. The results reveal functional similarities and differences between the D2R and D3R.
Any process that stops, prevents, or reduces the frequency, rate or extent of dopamine receptor protein signaling pathway activity. A dopamine receptor signaling pathway is the series of molecular signals generated as a consequence of a dopamine receptor binding to one of its physiological ligands.
Any process that stops, prevents, or reduces the frequency, rate or extent of the protein kinase B signaling cascade, a series of reactions mediated by the intracellular serine/threonine kinase protein kinase B.
OBJECTIVE: von Willebrand factor (VWF) is acutely released from endothelial cells in response to numerous calcium-raising agents (e.g. thrombin, histamine) and cAMP-raising agents (e.g. epinephrine, adenosine, vasopressin). In contrast, very few inhibitors of endothelial VWF secretion have been described. The neurotransmitter dopamine is a modulator of exocytosis in several endocrine cells, and is possibly involved in the regulation of several endothelial cell functions. We therefore investigated the effect of dopamine on endothelial VWF secretion. RESULTS: Dopamine, D2/D3- and D4-specific agonists inhibited histamine- but not thrombin-induced VWF secretion. Expression of dopamine D2, D3 and D4 receptors was demonstrated by reverse transcription polymerase chain reaction (RT-PCR) in both human aortic (HAEC) and umbilical vein (HUVEC) endothelial cells. D2-D4 agonists did not inhibit histamine-induced rise in [Ca(2+)](i): they inhibited histamine-induced secretion even in the absence of extracellular calcium. Thus, the dopamine effects are not mediated by [Ca(2+)](i)-dependent signalling. D2/D3- and D4-specific agonists inhibited neither the rise in cAMP nor VWF secretion in response to epinephrine and adenosine, arguing against an effect on cAMP-mediated signalling. D1 and D5 receptors were not detected in HAEC or HUVEC by RT-PCR, and the D1/D5-specific agonist SKF 38 393 failed to modulate VWF secretion, arguing against a role for these receptors in endothelial exocytosis. CONCLUSIONS: Dopamine inhibits histamine-induced endothelial exocytosis by activating D2-D4 receptor, via a mechanism distinct from [Ca(2+)](i)-or cAMP-mediated signaling. In contrast, D1 and D5 receptors are not functionally expressed in cultured endothelial cells. Dopamine agonists may be useful as inhibitors of endothelial activation in inflammation and cardiovascular disease.
Any process that activates or increases the frequency, rate or extent of the dopamine receptor protein signaling pathway. A dopamine receptor signaling pathway is the series of molecular signals generated as a consequence of a dopamine receptor binding to one of its physiological ligands.
BACKGROUND: The dopamine D(3) receptor (DRD(3)) is suspected to modulate prepulse inhibition (PPI) in animals and humans, but definite conclusions cannot be drawn due to lack of selective DRD(3) ligands. The Ser9Gly polymorphism is a common variant of the DRD(3) gene and determines the gain of function of the D(3) receptor. This is the first study to examine the influence of the DRD(3) Ser9Gly polymorphism on human PPI. METHODS: Prepulse inhibition was measured in 101 healthy male subjects presented with 75-dB and 85-dB prepulses at 30-, 60-, and 120-msec prepulse-pulse intervals. Subjects were grouped according to their DRD(3) status into a Gly/Gly, a Ser/Gly, and a Ser/Ser group. RESULTS: Analyses of variance showed that at all prepulse and interval conditions, Gly/Gly individuals had the lowest PPI and the greatest onset latency facilitation and Ser/Ser individuals had the highest PPI and the lowest onset latency facilitation, while Ser/Gly individuals were intermediate. CONCLUSIONS: These results suggest that PPI is modulated by the D(3) receptor and its levels depend on the Ser9Gly polymorphism.
Any process that modulates the frequency, rate or extent of the chemical reactions and pathways involving the nucleotide cAMP (cyclic AMP, adenosine 3',5'-cyclophosphate).
Despite a high degree of sequence homology, the dopamine D2 and D3 receptors have substantially different second messenger coupling properties. We have used chimeric D2/D3 receptors to investigate the contribution of the intracellular loops to the signaling properties of these receptors. In HEK 293 cells, D2 receptors inhibit prostaglandin E1-stimulated cyclic AMP levels by >90%, whereas D3 receptors inhibit cyclic AMP accumulation by only 20%. In chimeras that have the second or third intracellular loop, or both loops simultaneously, switched between the D2 and D3 receptors, the maximal inhibition of adenylyl cyclase is 60-90%. In addition, the potency of quinpirole to inhibit adenylyl cyclase activity at some of the chimeras is altered compared with the wild-type receptors. It appears that the intracellular loops of the D3 receptor are capable of interacting with G proteins, as when these loops are expressed in the D2 receptor, the chimeras inhibit adenylyl cyclase similarly to the wild-type D2 receptor. Our data suggest that the overall conformation of the D3 receptor may be such that it interacts with G proteins only weakly, but when the intracellular loops are expressed in another context or the D3 receptor structure is altered by the introduction of D2 receptor sequence, this constraint may be lifted.
Any process that modulates the frequency, rate or extent of sleep; a readily reversible state of reduced awareness and metabolic activity that occurs periodically in many animals.
J. Pharmacol. Exp. Ther. 268, 417-426 (1994)[PubMed:8301582]
Binding of dopamine receptor ligands to human D2 and D3 receptors was characterized in Chinese hamster ovary (CHO) cells using the dopamine D2 receptor antagonist [125I] iodosulpiride. Only limited binding selectivity was observed for known dopamine D2 receptor antagonists from a variety of chemical classes, which included haloperidol, chlorpromazine, sulpiride, pimozide and cis flupenthixol. The most selective compound from this group were (+)butaclamol and domperidone which showed 5-fold D3 selectivity. A number of high affinity dopamine receptor agonists, including apomorphine and bromocriptine, also failed to demonstrate selectivity. In contrast, the natural ligand dopamine and the efficacious synthetic agonists quinpirole, (+)4-propyl-9-hydroxynapthoxazine (PHNO), 2-amino-6,7-dihydroxy-1,2,3,4-tetrahydronaphthalene (6,7-ADTN), 7-OH DPAT and N-0434 showed marked apparent human dopamine D3 (hD3) receptor selectivity. In the aminotetralin series, this selectivity was observed preferentially with analogs of the 6,7-rotamer compared with compounds from the 5,6-rotamer series. Functional coupling of the hD3 receptor was investigated in a number of cell lines in which the hD3 receptor was stably expressed, including CHO cells, the neuroblastoma-glioma hybrid cell line NG108-15 and a rat 1 fibroblast cell line. There was no evidence of functional coupling of the hD3 receptor to adenylate cyclase, arachidonic acid release, phospholipase C activation, K+ currents or calcium mobilization in any of the cell lines examined. Furthermore, guanine nucleotides failed to inhibit the binding of [3H] N-0437 to hD3 receptors in any of the three cell lines. There may be a number of explanations for these results. These cell lines may not have the appropriate G-protein or secondary messenger systems that are coupled to the hD3 receptor in situ. Alternatively, this receptor may couple by a mechanism that is as yet undefined. The finding that a wide range of structurally diverse human dopamine D2 (hD2) receptor agonists have an apparent hD3 selectivity may imply that the hD3 receptor exists predominantly in a high affinity state.
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 amphetamine stimulus. Amphetamines consist of a group of compounds related to alpha-methylphenethylamine.
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 cocaine stimulus. Cocaine is a crystalline alkaloid obtained from the leaves of the coca plant.
Evidence
1:
Inferred from Expression PatternBHF-UCL
Ann. N. Y. Acad. Sci. 877, 507-522 (1999)[PubMed:10415668]
Cocaine is thought to be addictive because chronic use leads to molecular adaptations within the mesolimbic dopamine (DA) circuitry, which affects motivated behavior and emotion. Although the reinforcing effects of cocaine are mediated primarily by blockade of DA uptake, reciprocal signaling between DA and endogenous opioids has important implications for understanding cocaine dependence. We have used in vitro autoradiography and ligand binding to map D3 DA and kappa opioid receptors in the human brains of cocaine-overdose victims. The number of D3 binding sites was increased one-to threefold over the nucleus accumbens and ventromedial sectors of the caudate and putamen from cocaine-overdose victims, as compared to age-matched and drug-free control subjects. D3 receptor/cyclophilin mRNA ratios in the nucleus accumbens were increased sixfold in cocaine-overdose victims over control values, suggesting that cocaine exposure also affects the expression of D3 receptor mRNA. The number of kappa opioid receptors in the nucleus accumbens and other corticolimbic areas from cocaine fatalities was increased twofold as compared to control values. Cocaine-overdose victims exhibiting preterminal excited delirium had a selective upregulation of kappa receptors measured also in the amygdala. Understanding the complex regulatory profiles of DA and opioid synaptic markers that occur with chronic misuse of cocaine may suggest multitarget strategies for treating cocaine dependence.
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 ethanol stimulus.
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 histamine stimulus. Histamine, the biogenic amine 2-(1H-imidazol-4-yl)ethanamine, is involved in local immune responses as well as regulating physiological function in the gut and acting as a neurotransmitter.
OBJECTIVE: von Willebrand factor (VWF) is acutely released from endothelial cells in response to numerous calcium-raising agents (e.g. thrombin, histamine) and cAMP-raising agents (e.g. epinephrine, adenosine, vasopressin). In contrast, very few inhibitors of endothelial VWF secretion have been described. The neurotransmitter dopamine is a modulator of exocytosis in several endocrine cells, and is possibly involved in the regulation of several endothelial cell functions. We therefore investigated the effect of dopamine on endothelial VWF secretion. RESULTS: Dopamine, D2/D3- and D4-specific agonists inhibited histamine- but not thrombin-induced VWF secretion. Expression of dopamine D2, D3 and D4 receptors was demonstrated by reverse transcription polymerase chain reaction (RT-PCR) in both human aortic (HAEC) and umbilical vein (HUVEC) endothelial cells. D2-D4 agonists did not inhibit histamine-induced rise in [Ca(2+)](i): they inhibited histamine-induced secretion even in the absence of extracellular calcium. Thus, the dopamine effects are not mediated by [Ca(2+)](i)-dependent signalling. D2/D3- and D4-specific agonists inhibited neither the rise in cAMP nor VWF secretion in response to epinephrine and adenosine, arguing against an effect on cAMP-mediated signalling. D1 and D5 receptors were not detected in HAEC or HUVEC by RT-PCR, and the D1/D5-specific agonist SKF 38 393 failed to modulate VWF secretion, arguing against a role for these receptors in endothelial exocytosis. CONCLUSIONS: Dopamine inhibits histamine-induced endothelial exocytosis by activating D2-D4 receptor, via a mechanism distinct from [Ca(2+)](i)-or cAMP-mediated signaling. In contrast, D1 and D5 receptors are not functionally expressed in cultured endothelial cells. Dopamine agonists may be useful as inhibitors of endothelial activation in inflammation and cardiovascular 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 a morphine stimulus. Morphine is an opioid alkaloid, isolated from opium, with a complex ring structure.
We investigated whether polymorphisms of the dopamine D4 receptor (DRD4) and polymorphisms of the dopamine D3 receptor (DRD3) were associated with personality disorder symptomatology rather than with personality traits such as novelty seeking. DNA was obtained from 145 depressed patients in a clinical trial. These patients were assessed for the presence of personality disorder symptoms and disorders. The 2-repeat allele of the DRD4 exon III polymorphism was associated with increased rates of avoidant and obsessive personality disorder symptomatology. The T,T genotype of the DRD4 -521 C>T polymorphism was also associated with increased rates of avoidant and obsessive personality disorder symptomatology. The Gly9,Gly9 genotype of the DRD3 Ser9Gly polymorphism was associated with increased rates of obsessive personality disorder symptomatology. None of these three polymorphisms were associated with novelty seeking or other temperament traits on the Temperament and Character Inventory. Our results suggest that genetic polymorphisms of DRD4 and DRD3 may well be associated with personality traits, and that conflicting findings to date may arise from the problem of phenotype definition.
Receptors which transduce extracellular signals across the cell membrane. At the external side they receive a ligand (a photon in case of opsins), and at the cytosolic side they activate a guanine nucleotide-binding (G) protein. These receptors are hydrophobic proteins that cross the membrane seven times.
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.
My favorites 
My labels 
Login
