Enhancement of 5-hydroxytryptamine3A receptor function by phorbol 12-myristate, 13-acetate is mediated by protein kinase C and tyrosine kinase activity.
The effects of phorbol 12-myristate, 13-acetate (PMA) on 5-hydroxytryptamine (5-HT)-evoked ion currents in the mouse 5-HT3A receptor were examined. Perfusion with PMA caused a concentration dependent potentiation of 5-HT mediated currents and increased both potency and efficacy of 5-HT at the 5-HT3A receptor expressed in Xenopus oocytes. Enhancement of receptor function was partially blocked by injection of oocytes with PKCI, the peptide inhibitor of protein kinase C (PKC). Mutation of all 12 intracellular serine and threonine residues to alanine was without effect on PMA-induced potentiation of 5-HT elicited currents. Mutation of tyrosine 458 in the 5-HT3A receptor lacking intracellular serines and threonines reduced the PMA-induced potentiation of 5-HT evoked currents by approximately 55%. In contrast, mutation of tyrosine 458 in the wild-type receptor did not alter PMA-induced enhancement. The tyrosine kinase inhibitor, lavendustin A, reduced the enhancement of 5-HT3A receptor mediated currents by PMA in the mutant 5-HTA3A receptor containing no intracellular serine or threonine residues, but not in the wild-type receptor. Thus, the role of intracellular serines and threonines is redundant with that of tyrosine, suggesting that these two components act through a similar pathway in response to PMA treatment.
Coultrap
Steven J
SJ
Department of Pharmacology, Texas Tech University Health Sciences Center, 3601 Fourth St., Lubbock, TX 79430, USA.
Machu
Tina K
TK
D019943:Amino Acid Substitution; D000818:Animals; D001483:Base Sequence; D018076:DNA, Complementary / Q000235:genetics; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D066298:In Vitro Techniques; D051379:Mice; D016297:Mutagenesis, Site-Directed; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D018075:RNA, Complementary / Q000235:genetics; D011985:Receptors, Serotonin / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism*; D044406:Receptors, Serotonin, 5-HT3; D011994:Recombinant Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014982:Xenopus laevis
D018076:DNA, Complementary; D004791:Enzyme Inhibitors; D018075:RNA, Complementary; D011985:Receptors, Serotonin; D044406:Receptors, Serotonin, 5-HT3; D011994:Recombinant Proteins; D011505:Protein-Tyrosine Kinases; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate