title: The lutropin/choriogonadotropin receptor-induced phosphorylation of the extracellular signal-regulated kinases in leydig cells is mediated by a protein kinase a-dependent activation of ras.
abstract: The pathways involved in activation of the ERK1/2 cascade in Leydig cells were examined in MA-10 cells expressing the recombinant human LH receptor (hLHR) and in primary cultures of rat Leydig cell precursors. In MA-10 cells expressing the recombinant hLHR, human choriogonadotropin-induced activation of ERK1/2 is effectively inhibited by overexpression of a cAMP phosphodiesterase (a manipulation that blunts the human choriogonadotropin-induced cAMP response), by addition of H89 (a selective inhibitor of protein kinase A), or by overexpression of the heat-stable protein kinase A inhibitor, but not by overexpression of an inactive mutant of this inhibitor. Stimulation of hLHR did not activate Rap1, but activated Ras in an H89-sensitive fashion. Addition of H89 to MA-10 cells that had been cotransfected with a guanosine triphosphatase-deficient mutant of Ras almost completely inhibited the hLHR-mediated activation of ERK1/2. We also show that 8-bromo-cAMP activates Ras and ERK1/2 in MA-10 cells and in primary cultures of rat Leydig cells precursors in an H89-sensitive fashion, whereas a cAMP analog 8-(4-chloro-phenylthio)-2'-O-methyl-cAMP (8CPT-2Me-cAMP) that is selective for cAMP-dependent guanine nucleotide exchange factor has no effect. Collectively, our results show that the hLHR-induced phosphorylation of ERK1/2 in Leydig cells is mediated by a protein kinase A-dependent activation of Ras.
authors.affiliation: Department of Pharmacology, University of Iowa, Iowa City, Iowa 52242-1109, USA.
authors.forename: Takashi
authors.initials: T
authors.lastname: Hirakawa
authors.forename: Mario
authors.initials: M
authors.lastname: Ascoli
mesh_terms: D000818:Animals; D001127:Arginine Vasopressin / Q000494:pharmacology; D002478:Cells, Cultured; D006063:Chorionic Gonadotropin / Q000378:metabolism / Q000494:pharmacology; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004789:Enzyme Activation; D006801:Humans; D007295:Inositol Phosphates / Q000378:metabolism; D007985:Leydig Cells / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D008297:Male; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010766:Phosphorylation; D051381:Rats; D011974:Receptors, LH / Q000378:metabolism*; D015290:Second Messenger Systems / Q000187:drug effects; D015398:Signal Transduction; D020668:rap GTP-Binding Proteins / Q000378:metabolism; D018631:ras Proteins / Q000378:metabolism*
chemical_list: D006063:Chorionic Gonadotropin; D007295:Inositol Phosphates; D011974:Receptors, LH; D001127:Arginine Vasopressin; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D020668:rap GTP-Binding Proteins; D018631:ras Proteins