Protein kinase C-mediated phosphorylation and desensitization of human alpha(1b)-adrenoceptors.
Human alpha(1b)-adrenoceptors stably expressed (B(max) approximately 800 fmol/mg membrane protein) in mouse fibroblasts were able to increase intracellular Ca(2+) and inositol phosphate production in response to noradrenaline. Activation of protein kinase C desensitized the alpha(1b)-adrenergic-mediated actions but did not block the ability of the cells to respond to lysophosphatidic acid. Inhibition or downregulation of protein kinase C also blocked the action of the tumor promoter on the adrenergic effects. Photolabeling experiments indicated that the receptor has an apparent molecular weight of approximately 80 kDa. The receptors were phosphorylated in the basal state and such phosphorylation was increased when the cells were incubated with phorbol myristate acetate or noradrenaline. Incubation of the cells with phorbol myristate acetate or noradrenaline blocked noradrenaline-promoted [35S]GTP-gamma-S binding to membranes, suggesting receptor-G protein uncoupling. The results indicate that activation of protein kinase C blocked/desensitized human alpha(1b)-adrenoceptors and that such effect was associated to receptor phosphorylation.
García-Sáinz
J A
JA
Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Apartado Postal 70-248, Mexico, Mexico. agarcia@ifisiol.unam.mx
Gottfried-Blackmore
A
A
Vázquez-Prado
J
J
Romero-Avila
M T
MT
D000818:Animals; D001667:Binding, Competitive; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D007295:Inositol Phosphates / Q000378:metabolism; D008566:Membranes / Q000187:drug effects / Q000378:metabolism; D009638:Norepinephrine / Q000494:pharmacology; D010646:Phentolamine / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D010879:Piperazines / Q000378:metabolism; D011224:Prazosin / Q000378:metabolism; D011233:Precipitin Tests; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011869:Radioligand Assay; D018340:Receptors, Adrenergic, alpha-1 / Q000235:genetics / Q000378:metabolism*; D013462:Sulfur Radioisotopes; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014316:Tritium
C547716:ADRA1B protein, human; C547717:Adra1b protein, mouse; D007211:Indoles; D007295:Inositol Phosphates; D010879:Piperazines; D012333:RNA, Messenger; D018340:Receptors, Adrenergic, alpha-1; D013462:Sulfur Radioisotopes; D014316:Tritium; C057446:5-methylurapidil; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D011493:Protein Kinase C; C053428:BMY 7378; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium; C064758:Ro 31-8220; D009638:Norepinephrine; D011224:Prazosin; D010646:Phentolamine