title: Evidence for the involvement of two pathways in activation of extracellular signal-regulated kinase (Erk) and cell proliferation by Gi and Gq protein-coupled receptors in osteoblast-like cells.
abstract: The mechanisms by which Gi and Gq protein- coupled receptors mediate mitogenic signaling in osteoblast-like cells are unknown and were investigated in MC3T3-E1 cells using specific receptor agonists such as lysophosphatidic acid (LPA) and prostaglandin F2alpha (PGF2alpha). In contrast to their implication in epidermal growth factor (EGF) receptor tyrosine kinase signaling, the adaptor protein Shc, the Grb2/Sos complex, and the small G protein Ras were not involved in the activation of Erk induced by either LPA or PGF2alpha in MC3T3-E1 cells, suggesting that activation of Erk by Gi and Gq protein-coupled receptors is Ras independent in these cells. Using specific kinase inhibitors and kinetic analyses, we provide evidence for two distinct components in the activation of Erk by Gi and Gq protein-coupled receptors in MC3T3-E1 cells including an Src-like kinase-dependent pathway and a protein kinase C (PKC)-dependent mechanism. Functional analyses suggested that these two components are required for optimal DNA synthesis in response to LPA and PGF2alpha. These results suggest the implication of two pathways in the stimulation of Erk and cell replication by growth factors acting through Gi and Gq protein-coupled receptors in bone-forming cells.
authors.affiliation: Department of Internal Medicine, University Hospital of Geneva, Switzerland.
authors.forename: J
authors.initials: J
authors.lastname: Caverzasio
authors.forename: G
authors.initials: G
authors.lastname: Palmer
authors.forename: A
authors.initials: A
authors.lastname: Suzuki
authors.forename: J P
authors.initials: JP
authors.lastname: Bonjour
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D000818:Animals; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D004247:DNA / Q000096:biosynthesis; D015237:Dinoprost / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D004815:Epidermal Growth Factor / Q000494:pharmacology; D051380:GRB2 Adaptor Protein; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000819:agonists / Q000378:metabolism; D020962:Heterotrimeric GTP-Binding Proteins / Q000819:agonists / Q000378:metabolism*; D008246:Lysophospholipids / Q000494:pharmacology; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010006:Osteoblasts / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D019000:Phosphotyrosine / Q000378:metabolism; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D016283:Proto-Oncogene Proteins p21(ras) / Q000037:antagonists & inhibitors / Q000378:metabolism; D011720:Pyrazoles / Q000494:pharmacology; D011743:Pyrimidines / Q000494:pharmacology; D011956:Receptors, Cell Surface / Q000819:agonists / Q000378:metabolism*; D055765:Shc Signaling Adaptor Proteins; D015398:Signal Transduction / Q000187:drug effects; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
chemical_list: C108123:4-amino-5-(4-methylphenyl)-7-(tert-butyl)pyrazolo(3,4-d)pyrimidine; D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D051380:GRB2 Adaptor Protein; C495949:Grb2 protein, mouse; D008246:Lysophospholipids; D011506:Proteins; D011720:Pyrazoles; D011743:Pyrimidines; D011956:Receptors, Cell Surface; D055765:Shc Signaling Adaptor Proteins; C528034:Shc1 protein, mouse; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D010566:Virulence Factors, Bordetella; D019000:Phosphotyrosine; D004815:Epidermal Growth Factor; D004247:DNA; D015237:Dinoprost; D011505:Protein-Tyrosine Kinases; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D020962:Heterotrimeric GTP-Binding Proteins; D016283:Proto-Oncogene Proteins p21(ras)