title: Direct association of Grb2 with the p85 subunit of phosphatidylinositol 3-kinase.
abstract: Phosphatidylinositol 3-kinase (PI 3-kinase) has been shown to play a key role in growth factor signaling pathways, although its signaling mechanism has not been fully elucidated. Using the yeast interaction trap system, we have identified Grb2 as a PI 3-kinase interacting protein. Our experiments demonstrate that p85, the regulatory subunit of PI 3-kinase, interacts with Grb2 in vivo, and this interaction is independent of growth factor stimulation. The direct association between Grb2 and p85 was reconstituted in vitro with glutathione S-transferase fusion proteins. Domain analyses and peptide competition indicate that the association is mediated by the SH3 domains of Grb2 and the proline-rich motifs of p85 and that only one SH3 domain is required for minimal binding. The interaction does not displace the catalytic subunit of PI 3-kinase but is exclusive of Sos. Signaling through PI 3-kinase, therefore, may involve the ubiquitous adapter Grb2, which serves as a convergence point for multiple pathways.
authors.affiliation: Division of Cell and Molecular Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, USA.
authors.forename: J
authors.initials: J
authors.lastname: Wang
authors.forename: K R
authors.initials: KR
authors.lastname: Auger
authors.forename: L
authors.initials: L
authors.lastname: Jarvis
authors.forename: Y
authors.initials: Y
authors.lastname: Shi
authors.forename: T M
authors.initials: TM
authors.lastname: Roberts
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002417:Cattle; D002478:Cells, Cultured; D018076:DNA, Complementary / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D051380:GRB2 Adaptor Protein; D015723:Gene Library; D006801:Humans; D008969:Molecular Sequence Data; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D011233:Precipitin Tests; D011485:Protein Binding; D011487:Protein Conformation; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012641:Selection, Genetic; D017422:Sequence Analysis, DNA; D015398:Signal Transduction / Q000502:physiology*; D015003:Yeasts / Q000235:genetics
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D018076:DNA, Complementary; D051380:GRB2 Adaptor Protein; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D010982:Platelet-Derived Growth Factor; D011506:Proteins; D011993:Recombinant Fusion Proteins; C495948:GRB2 protein, human; C495950:Grb2 protein, rat