title: The third intracellular loop of D1 and D5 dopaminergic receptors dictates their subtype-specific PKC-induced sensitization and desensitization in a receptor conformation-dependent manner.
abstract: We previously showed that phorbol-12-myristate-13-acetate (PMA) mediates a robust PKC-dependent sensitization and desensitization of the highly homologous human Gs protein and adenylyl cyclase (AC)-linked D1 (hD1R) and D5 (hD5R) dopaminergic receptors, respectively. Here, we demonstrate using forskolin-mediated AC stimulation that PMA-mediated hD1R sensitization and hD5R desensitization is not associated with changes in AC activity. We next employed a series of chimeric hD1R and hD5R to delineate the underlying structural determinants dictating the subtype-specific regulation of human D1-like receptors by PMA. We first used chimeric receptors in which the whole terminal region (TR) spanning from the extracellular face of transmembrane domain 6 to the end of cytoplasmic tail (CT) or CT alone were exchanged between hD1R and hD5R. CT and TR swaps lead to chimeric hD1R and hD5R retaining PMA-induced sensitization and desensitization of wild type parent receptors. In striking contrast, hD1R sensitization and hD5R desensitization mediated by PMA are correspondingly switched to PMA-induced receptor desensitization and sensitization following the IL3 swap between hD1R and hD5R. Cell treatment with the PKC blocker, Gö6983, inhibits PMA-induced regulation of these chimeric receptors in a similar fashion to wild type receptors. Further studies with chimeras constructed by exchanging IL3 and TR show that PMA-induced regulation of these chimeras remains fully switched relative to their respective wild type parent receptor. Interestingly, results obtained with the exchange of IL3 and TR also reveal that the D1-like subtype-specific regulation by PMA, while fully dictated by IL3, can be modulated in a receptor conformation-dependent manner. Overall, our results strongly suggest that IL3 is the critical determinant underlying the subtype-specific regulation of human D1-like receptor responsiveness by PKC.
authors: Ottawa Hospital Research Institute, Department of Medicine, University of Ottawa, Ottawa, ON, Canada.
authors: Bianca
authors: B
authors: Plouffe
authors: Xiaodi
authors: X
authors: Yang
authors: Mario
authors: M
authors: Tiberi
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D020816:Amino Acid Motifs; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D004298:Dopamine / Q000494:pharmacology / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D020536:Enzyme Activators / Q000494:pharmacology; D057809:HEK293 Cells; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D007527:Isoenzymes / Q000378:metabolism; D008301:Maleimides / Q000494:pharmacology; D010766:Phosphorylation; D011487:Protein Conformation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D017447:Receptors, Dopamine D1 / Q000819:agonists / Q000737:chemistry / Q000378:metabolism*; D050641:Receptors, Dopamine D5 / Q000819:agonists / Q000737:chemistry / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000819:agonists / Q000737:chemistry / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: C465664:2-(1-(3-dimethylaminopropyl)-5-methoxyindol-3-yl)-3-(1H-indol-3-yl)maleimide; D020536:Enzyme Activators; D007211:Indoles; D007527:Isoenzymes; D008301:Maleimides; D017447:Receptors, Dopamine D1; D011993:Recombinant Fusion Proteins; D050641:Receptors, Dopamine D5; D005576:Colforsin; D000242:Cyclic AMP; D011493:Protein Kinase C; D000262:Adenylyl Cyclases; D013755:Tetradecanoylphorbol Acetate; D004298:Dopamine