Erythropoietin Induces the Tyrosine Phosphorylation of GAB1 and Its Association With SHC, SHP2, SHIP, and Phosphatidylinositol 3-Kinase

Abstract

Five tyrosine-phosphorylated proteins with molecular masses of 180, 145, 116, 100, and 70 kD are associated with phosphatidylinositol 3-kinase (PI 3-kinase) in erythropoietin (Epo)-stimulated UT-7 cells. The 180- and 70-kD proteins have been previously shown to be IRS2 and the Epo receptor. In this report, we show that the 116-kD protein is the IRS2-related molecular adapter, GAB1. Indeed, Epo induced the transient tyrosine phosphorylation of GAB1 in UT-7 cells. Both kinetics and Epo dose-response experiments showed that GAB1 tyrosine phosphorylation was a direct consequence of Epo receptor activation. After tyrosine phosphorylation, GAB1 associated with the PI 3-kinase, the phosphotyrosine phosphatase SHP2, the phosphatidylinositol 3,4,5 trisphosphate 5-phosphatase SHIP, and the molecular adapter SHC. GAB1 was also associated with the molecular adapter GRB2 in unstimulated cells, and this association dramatically increased after Epo stimulation. Thus, GAB1 could be a scaffold protein able to couple the Epo receptor activation with the stimulation of several intracellular signaling pathways. Epo-induced tyrosine phosphorylation of GAB1 was also observed in normal human erythroid progenitors isolated from cord blood. Granulocyte-macrophage colony-stimulating factor (GM-CSF) and thrombopoietin (TPO) also induced the tyrosine phosphorylation of GAB1 in UT-7 cells, indicating that this molecule participates in the signal transduction of several cytokine receptors.

The role of Gab family scaffolding adapter proteins in the signal transduction of cytokine and growth factor receptors

“…Gab1 is tyrosine-phosphorylated in response to insulin, EGF, HGF, NGF, PDGF, Kitl, Flt3l, lysophosphatidic acid (LPA), thrombopoietin (TPO), IL-3, IFNα/β, and stimulation of gp130, the common subunit of receptors for the IL-6-family cytokines, and T and B antigen receptors. 12,14,17,[23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] Gab2 is tyrosine-phosphorylated in response to IL-2, IL-3, IL-15, TPO, EPO, Kitl, M-CSF, Flt3l, and the stimulation of gp130, FcεRI, FcγR, and T and B antigen receptors. 13-15, 18, 38-50) Gab3 is tyrosine-phosphorylated in response to M-CSF.…”

Coupling of Gab1 to C-Met, Grb2, and Shp2 Mediates Biological Responses

“…Gab1 overexpression enhances the transforming and growth promoting activities of activated EGF and insulin receptors and promotes NGF-stimulated survival of neuronal cells (Holgado-Madruga et al 1996, Holgado-Madruga et al 1997). Many extracellular stimuli like EGF, insulin, IL3, IL6, erythropoietin (Epo), as well as B cell receptor activation induce Gab1 phosphorylation and association with Shc, PI(3)K, PLC-γ, Ship, and Shp2 (Holgado-Madruga et al 1996; Takahashi-Tezuka et al 1998; Lecoq-Lafon et al 1999; Ingham et al 1998; Rodrigues et al 2000). Association of Gab1 with PI(3)K has been shown to be important for prevention of apoptosis in response to NGF stimulation (Holgado-Madruga et al 1997).…”

Essential Role of Gab1 for Signaling by the C-Met Receptor in Vivo

“…Gab1 is not only phosphorylated by c-Met, but is also indirectly activated by other tyrosine kinases. Extracellular stimuli like EGF, insulin, IL3, IL6, Epo1, or the activation of the B cell receptor result in phosphorylation of Gab1 (Holgado-Madruga et al 1996; Ingham et al 1998; Takahashi-Tezuka et al 1998; Lecoq-Lafon et al 1999; Rodrigues et al 2000). PI(3) kinase, Shc, Shp2, and CRKL are direct interaction partners of Gab1 (Holgado-Madruga et al 1996; Bardelli et al 1997; Maroun et al 1999; Schaeper et al 2000).…”