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

• Published in: Molecular endocrinology (Baltimore, Md.) Md.), 2003-11, Vol.17 (11), p.2189-2200
• Main Authors: Hirakawa, Takashi, Ascoli, Mario
• Format: Article
• Language: English
• Subjects: Animals; Arginine Vasopressin - pharmacology; Cells, Cultured; Chorionic Gonadotropin - metabolism; Chorionic Gonadotropin - pharmacology; Cyclic AMP - analogs & derivatives; Cyclic AMP - metabolism; Cyclic AMP-Dependent Protein Kinases - metabolism; Enzyme Activation; Humans; Inositol Phosphates - metabolism; Leydig Cells - cytology; Leydig Cells - enzymology; Leydig Cells - metabolism; Male; Mice; Mitogen-Activated Protein Kinases - metabolism; Phosphorylation; rap GTP-Binding Proteins - metabolism; ras Proteins - metabolism; Rats; Receptors, LH - metabolism; Second Messenger Systems - drug effects; Signal Transduction
• ISSN: 0888-8809; 1944-9917
• DOI: 10.1210/me.2003-0205

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.