title: Src tyrosine kinase is a novel direct effector of G proteins.
abstract: Heterotrimeric G proteins transduce signals from cell surface receptors to modulate the activity of cellular effectors. Src, the product of the first characterized proto-oncogene and the first identified protein tyrosine kinase, plays a critical role in the signal transduction of G protein-coupled receptors. However, the mechanism of biochemical regulation of Src by G proteins is not known. Here we demonstrate that Galphas and Galphai, but neither Galphaq, Galpha12 nor Gbetay, directly stimulate the kinase activity of downregulated c-Src. Galphas and Galphai similarly modulate Hck, another member of Src-family tyrosine kinases. Galphas and Galphai bind to the catalytic domain and change the conformation of Src, leading to increased accessibility of the active site to substrates. These data demonstrate that the Src family tyrosine kinases are direct effectors of G proteins.
authors.affiliation: Department of Physiology, Cornell University Medical College, New York, New York 10021, USA.
authors.forename: Y C
authors.initials: YC
authors.lastname: Ma
authors.forename: J
authors.initials: J
authors.lastname: Huang
authors.forename: S
authors.initials: S
authors.lastname: Ali
authors.forename: W
authors.initials: W
authors.lastname: Lowry
authors.forename: X Y
authors.initials: XY
authors.lastname: Huang
mesh_terms: D000818:Animals; D001665:Binding Sites; D015153:Blotting, Western; D020134:Catalytic Domain; D002460:Cell Line; D015536:Down-Regulation; D004789:Enzyme Activation; D005347:Fibroblasts; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000235:genetics / Q000378:metabolism; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D020962:Heterotrimeric GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D051379:Mice; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D011487:Protein Conformation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051572:Proto-Oncogene Proteins c-hck; D015398:Signal Transduction; D019061:src-Family Kinases / Q000737:chemistry / Q000378:metabolism*
chemical_list: C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D019000:Phosphotyrosine; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D011505:Protein-Tyrosine Kinases; C496631:HCK protein, human; C496632:Hck protein, mouse; D051572:Proto-Oncogene Proteins c-hck; D019061:src-Family Kinases; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D019205:GTP-Binding Protein alpha Subunits, Gs; D020962:Heterotrimeric GTP-Binding Proteins