title: Activation of the lutropin/choriogonadotropin receptor in MA-10 cells stimulates tyrosine kinase cascades that activate ras and the extracellular signal regulated kinases (ERK1/2).
abstract: We show that activation of the recombinant lutropin/choriogonadotropin receptor (LHR) in mouse Leydig tumor cells (MA-10 cells) leads to the tyrosine phosphorylation of Shc (Src homology and collagen homology) and the formation of complexes containing Shc and Sos (Son of sevenless), a guanine nucleotide exchange factor for Ras. Because a dominant-negative mutant of Shc inhibits the LHR-mediated activation of Ras and the phosphorylation of ERK1/2, we conclude that the LHR-mediated phosphorylation of ERK1/2 is mediated, at least partially, by the classical pathway used by growth factor receptors. We also show that the endogenous epidermal growth factor receptor (EGFR) present in MA-10 cells is phosphorylated upon activation of the LHR. The LHR-mediated phosphorylation of the EGFR and Shc, the activation of Ras, and the phosphorylation of ERK1/2 are inhibited by expression of a dominant-negative mutant of Fyn, a member of the Src family kinases (SFKs) expressed in MA-10 cells and by PP2, a pharmacological inhibitor of the SFKs. These are also inhibited, but to a lesser extent, by AG1478, an inhibitor of the EGFR kinase. We conclude that the SFKs are responsible for the LHR-mediated phosphorylation of the EGFR and Shc, the formation of complexes containing Shc and Sos, the activation of Ras, and the phosphorylation of ERK1/2.
authors.affiliation: Department of Pharmacology, 2-319B BSB, 51 Newton Road, The University of Iowa, Iowa City, 52242-1109, USA.
authors.forename: Koji
authors.initials: K
authors.lastname: Shiraishi
authors.forename: Mario
authors.initials: M
authors.lastname: Ascoli
mesh_terms: D000818:Animals; D002460:Cell Line; D006063:Chorionic Gonadotropin / Q000378:metabolism; D004789:Enzyme Activation; D005799:Genes, Dominant; D006801:Humans; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011799:Quinazolines; D011974:Receptors, LH / Q000378:metabolism*; D020032:Tyrphostins / Q000494:pharmacology; D020703:ras GTPase-Activating Proteins / Q000378:metabolism*; D018631:ras Proteins / Q000378:metabolism*
chemical_list: D006063:Chorionic Gonadotropin; D011799:Quinazolines; D011974:Receptors, LH; D020032:Tyrphostins; D020703:ras GTPase-Activating Proteins; C101044:RTKI cpd; D011505:Protein-Tyrosine Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D018631:ras Proteins