title: Role of c-Src tyrosine kinase in G protein-coupled receptor- and Gbetagamma subunit-mediated activation of mitogen-activated protein kinases.
abstract: Several G protein-coupled receptors that interact with pertussis toxin-sensitive heterotrimeric G proteins mediate Ras-dependent activation of mitogen-activated protein (MAP) kinases. The mechanism involves Gbetagamma subunit-mediated increases in tyrosine phosphorylation of the Shc adapter protein, Shc*Grb2 complex formation, and recruitment of Ras guanine nucleotide exchange factor activity. We have investigated the role of the ubiquitous nonreceptor tyrosine kinase c-Src in activation of the MAP kinase pathway via endogenous G protein-coupled lysophosphatidic acid (LPA) receptors or by transient expression of Gbetagamma subunits in COS-7 cells. In vitro kinase assays of Shc immunoprecipitates following LPA stimulation demonstrated rapid, transient recruitment of tyrosine kinase activity into Shc immune complexes. Recruitment of tyrosine kinase activity was pertussis toxin-sensitive and mimicked by cellular expression of Gbetagamma subunits. Immunoblots for coprecipitated proteins in Shc immunoprecipitates revealed a transient association of Shc and c-Src following LPA stimulation, which coincided with increases in Shc-associated tyrosine kinase activity and Shc tyrosine phosphorylation. LPA stimulation or expression of Gbetagamma subunits resulted in c-Src activation, as assessed by increased c-Src autophosphorylation. Overexpression of wild-type or constitutively active mutant c-Src, but not kinase inactive mutant c-Src, lead to increased tyrosine kinase activity in Shc immunoprecipitates, increased Shc tyrosine phosphorylation, and Shc.Grb2 complex formation. MAP kinase activation resulting from LPA receptor stimulation, expression of Gbetagamma subunits, or expression of c-Src was sensitive to dominant negatives of mSos, Ras, and Raf. Coexpression of Csk, which inactivates Src family kinases by phosphorylating the regulatory C-terminal tyrosine residue, inhibited LPA stimulation of Shc tyrosine phosphorylation, Shc.Grb2 complex formation, and MAP kinase activation. These data suggest that Gbetagamma subunit-mediated formation of Shc.c-Src complexes and c-Src kinase activation are early events in Ras-dependent activation of MAP kinase via pertussis toxin-sensitive G protein-coupled receptors.
authors.affiliation: Howard Hughes Medical Institute, Duke University Medical Center, Durham, North Carolina 27710, USA.
authors.forename: L M
authors.initials: LM
authors.lastname: Luttrell
authors.forename: B E
authors.initials: BE
authors.lastname: Hawes
authors.forename: T
authors.initials: T
authors.lastname: van Biesen
authors.forename: D K
authors.initials: DK
authors.lastname: Luttrell
authors.forename: T J
authors.initials: TJ
authors.lastname: Lansing
authors.forename: R J
authors.initials: RJ
authors.lastname: Lefkowitz
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D000081247:CSK Tyrosine-Protein Kinase; D002352:Carrier Proteins / Q000378:metabolism; D002460:Cell Line; D004789:Enzyme Activation; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000037:antagonists & inhibitors / Q000378:metabolism*; D043562:Receptors, G-Protein-Coupled; D049368:Receptors, Lysophosphatidic Acid; D015398:Signal Transduction; D018631:ras Proteins / Q000378:metabolism; D019061:src-Family Kinases
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; C409587:GRAP2 protein, human; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D049368:Receptors, Lysophosphatidic Acid; D011494:Protein Kinases; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; D019061:src-Family Kinases; C000631346:CSK protein, human; D019204:GTP-Binding Proteins; D018631:ras Proteins