title: Unique phosphorylation mechanism of Gab1 using PI 3-kinase as an adaptor protein.
abstract: Grb2-associated binder-1 (Gab1) undergoes tyrosine phosphorylation in response to stimulation by growth factors and hormones including insulin, epidermal growth factor (EGF), nerve growth factor (NGF), and hepatocyte growth factor (HGF). However, the HGF receptor is the only one known to associate directly with Gab1. Herein, we explore the mechanism of Gab1 phosphorylation by other receptor protein-tyrosine kinases unable to bind to Gab1 directly. The Src homology 2 (SH2) domain of the phosphatidylinositol 3-kinase (PI3K) regulatory subunit binds Gab1 in a phosphorylation-independent manner. Moreover, the regulatory subunit of PI3K can mediate the association of Gab1 and receptor protein-tyrosine kinases including the insulin, EGF, and NGF receptors, all of which phosphorylate Gab1. Thus, it appears that the PI3K regulatory subunit acts as an adaptor protein via a phosphotyrosyl-independent SH2 interaction, allowing Gab1 to serve as a substrate for several tyrosine kinases. This is a new role for the PI3K regulatory subunit.
authors.affiliation: Department of Internal Medicine, Faculty of Medicine, University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8655, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Onishi-Haraikawa
authors.forename: M
authors.initials: M
authors.lastname: Funaki
authors.forename: N
authors.initials: N
authors.lastname: Gotoh
authors.forename: M
authors.initials: M
authors.lastname: Shibuya
authors.forename: K
authors.initials: K
authors.lastname: Inukai
authors.forename: H
authors.initials: H
authors.lastname: Katagiri
authors.forename: Y
authors.initials: Y
authors.lastname: Fukushima
authors.forename: M
authors.initials: M
authors.lastname: Anai
authors.forename: T
authors.initials: T
authors.lastname: Ogihara
authors.forename: H
authors.initials: H
authors.lastname: Sakoda
authors.forename: H
authors.initials: H
authors.lastname: Ono
authors.forename: M
authors.initials: M
authors.lastname: Kikuchi
authors.forename: Y
authors.initials: Y
authors.lastname: Oka
authors.forename: T
authors.initials: T
authors.lastname: Asano
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D016466:CHO Cells; D002478:Cells, Cultured; D006224:Cricetinae; D006801:Humans; D007313:Insecta; D055504:Insulin Receptor Substrate Proteins; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010750:Phosphoproteins / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation; D017434:Protein Structure, Tertiary; D011505:Protein-Tyrosine Kinases / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C098587:GAB1 protein, human; C526292:IRS1 protein, human; D055504:Insulin Receptor Substrate Proteins; D010750:Phosphoproteins; D019869:Phosphatidylinositol 3-Kinases; D011505:Protein-Tyrosine Kinases