Protein kinase C induces phosphorylation and desensitization of the human 5-HT1A receptor.
The effects of short-term phorbol ester treatment of CHO cells that stably express 900 fmol of recombinant human serotonin 5-HT1A receptor/mg of protein on coupling to the inhibition of adenylyl cyclase and on phosphorylation of the receptor were studied. Pretreatment of cell monolayers with phorbol 12-myristate 13-acetate (PMA) caused a dose- and time-dependent shift of the half-maximal dose of serotonin (5-HT) required to inhibit membrane adenylyl cyclase (from IC50 approximately 100 nM to approximately 400 nM). This desensitization (shift in IC50) was rapid, occurring with 5 min of pretreatment and being maximal by 10-15 min; it was also dose-dependent, being half-maximal at approximately 300 nM PMA. Desensitization was also induced by sn-dioctanoylglycerol (DiC8) and blocked by the protein kinase C (PKC) inhibitors sphingosine and 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7). In detached permeabilized cells, PMA pretreatment caused a rapid phosphorylation of immunoprecipitated 5-HT1A receptors, with an approximately 3-4-fold increase that was maximal after 15 min and persisted for 90 min. The phosphorylation occurred at a similar dose of PMA as that which induced desensitization (half-maximal at approximately 300 nM, maximal at 500 nM to 1 microM), could be reproduced by pretreatment with the PKC activators DiC8 or phorbol 12,13-dibutyrate (PDBu), and could be blocked by the PKC inhibitors sphingosine or H-7. The stoichiometry of the phosphorylation was approximately 2 mol of [32P]ATP/mol of receptor, suggesting the involvement at least two of three putative PKC sites within the 5-HT1A receptor. The close concordance between the PKC-induced desensitization and phosphorylation suggests a potential causative link between these two effects of PKC on the human 5-HT1A receptor.
Raymond
J R
JR
Department of Medicine (Nephrology), Duke University Medical Center, Durham, North Carolina 27710.
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000067956:Adenylyl Cyclase Inhibitors; D000345:Affinity Labels; D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000201:enzymology; D003001:Cloning, Molecular; D006224:Cricetinae; D003412:Cricetulus; D006801:Humans; D007546:Isoquinolines / Q000494:pharmacology; D010766:Phosphorylation; D010777:Photochemistry; D010879:Piperazines / Q000494:pharmacology; D011233:Precipitin Tests; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011985:Receptors, Serotonin / Q000235:genetics / Q000378:metabolism*; D013110:Sphingosine / Q000037:antagonists & inhibitors; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D000067956:Adenylyl Cyclase Inhibitors; D000345:Affinity Labels; D007546:Isoquinolines; D010879:Piperazines; D011985:Receptors, Serotonin; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D011493:Protein Kinase C; D013110:Sphingosine; D013755:Tetradecanoylphorbol Acetate