Scaffolding Protein Grb2-associated Binder 1 Sustains Epidermal Growth Factor-induced Mitogenic and Survival Signaling by Multiple Positive Feedback Loops

doi:10.1074/jbc.M600482200

Scaffolding Protein Grb2-associated Binder 1 Sustains Epidermal Growth Factor-induced Mitogenic and Survival Signaling by Multiple Positive Feedback Loops*

Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107

2 To whom correspondence should be addressed: Dept. of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, 1020 Locust St., Philadelphia, PA 19107. Tel.: 215-503-1614; Fax: 215-923-2218; E-mail: Boris.Kholodenko{at}jefferson.edu.

Abstract

Grb2-associated binder 1 (GAB1) is a scaffold protein involved in numerous interactions that propagate signaling by growth factor and cytokine receptors. Here we explore in silico and validate in vivo the role of GAB1 in the control of mitogenic (Ras/MAPK) and survival (phosphatidylinositol 3-kinase (PI3K)/Akt) signaling stimulated by epidermal growth factor (EGF). We built a comprehensive mechanistic model that allows for reliable predictions of temporal patterns of cellular responses to EGF under diverse perturbations, including different EGF doses, GAB1 suppression, expression of mutant proteins, and pharmacological inhibitors. We show that the temporal dynamics of GAB1 tyrosine phosphorylation is significantly controlled by positive GAB1-PI3K feedback and negative MAPK-GAB1 feedback. Our experimental and computational results demonstrate that the essential function of GAB1 is to enhance PI3K/Akt activation and extend the duration of Ras/MAPK signaling. By amplifying positive interactions between survival and mitogenic pathways, GAB1 plays the critical role in cell proliferation and tumorigenesis.

Footnotes

↵3 The abbreviations used are: EGF, epidermal growth factor; EGFR, epidermal growth factor receptor; ERK, extracellular signal-regulated kinase; ERK-PP, Thr-202/Tyr-204-phosphorylated ERK; GAB1, Grb2-associated binder 1; GEF, guanine nucleotide exchange factor; Grb2, growth factor receptor binding protein 2; MAPK, mitogen-activated protein kinase; MEK, dual specificity MAPK kinase; MKP, MAPK phosphatase; PH, pleckstrin homology domain; PI3K, phosphatidylinositol 3-kinase; PIP₃, phosphatidylinositol (3,4,5)-trisphosphate; RasGAP/p120-GAP, GTPase-activating protein; SH2/3, Src homology 2/3 domain; Shc, Src homology 2 and α-collagen domain-containing protein; SHP2, Src homology 2 containing phosphotyrosine phosphatase; siRNA, small interfering RNA; SOS, son of sevenless; Src, src avian sarcoma viral oncogene homolog; Bis-Tris, 2-[bis(2-hydroxyethyl)amino]-2-(hydroxymethyl)propane-1,3-diol.
↵* This work was supported by National Institutes of Health Grants GM59570 and AA015311. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵ The on-line version of this article (available at http://www.jbc.org) contains additional text, supplemental Tables S1–S3, and references.
↵1 These authors contributed equally to this work.
- Received January 17, 2006.
- Revision received April 13, 2006.
The American Society for Biochemistry and Molecular Biology, Inc.