title: A G-protein beta gamma-subunit-responsive phosphoinositide 3-kinase activity in human platelet cytosol.
abstract: Thrombin activates phosphoinositide 3-kinase (PI 3-kinase) in platelets via a mechanism involving G-proteins, possibly of both the heterotrimeric and the low molecular weight families. We have investigated the regulation of PI 3-kinase present in platelet cytosol, and we show that this activity can be stimulated by a mixed preparation of G-protein beta gamma-subunits. This stimulation is reversed by preincubation of the beta gamma-subunits with GDP-liganded alpha-subunits. The beta gamma-stimulated activity is inhibited by wortmannin, a recently identified inhibitor of PI 3-kinase in other systems. In addition, the activity associates with PDGF receptor phosphotyrosyl peptide and monoclonal antibody designed to interact with the p85 subunit of PI 3-kinase. We suggest that this beta gamma-sensitive activity is related to previously identified forms of PI 3-kinase.
authors.affiliation: Biochemistry Department, University of Dundee, Scotland, United Kingdom.
authors.forename: P A
authors.initials: PA
authors.lastname: Thomason
authors.forename: S R
authors.initials: SR
authors.lastname: James
authors.forename: P J
authors.initials: PJ
authors.lastname: Casey
authors.forename: C P
authors.initials: CP
authors.lastname: Downes
mesh_terms: D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D001792:Blood Platelets / Q000201:enzymology*; D001921:Brain / Q000378:metabolism; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism; D003600:Cytosol / Q000201:enzymology; D019204:GTP-Binding Proteins / Q000302:isolation & purification / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D046911:Macromolecular Substances; D010446:Peptide Fragments / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases; D010748:Phosphopeptides / Q000494:pharmacology; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors / Q000097:blood*; D017479:Receptors, Platelet-Derived Growth Factor / Q000378:metabolism; D000077191:Wortmannin
chemical_list: D000730:Androstadienes; D000911:Antibodies, Monoclonal; D046911:Macromolecular Substances; D010446:Peptide Fragments; D010748:Phosphopeptides; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D017479:Receptors, Platelet-Derived Growth Factor; D019204:GTP-Binding Proteins; D000077191:Wortmannin