Grb2-associated binder-1 mediates phosphatidylinositol 3-kinase activation and the promotion of cell survival by nerve growth factor

Grb2-associated binder-1 mediates phosphatidylinositol 3-kinase activation and the promotion of cell survival by nerve growth factor

Departments of ^*Microbiology and Immunology, and ^†Biochemistry and Molecular Pharmacology, Kimmel Cancer Institute, Thomas Jefferson University, 233 South 10th Street, Bluemle Life Science Building 1002, Philadelphia, PA 19107

Edited by George F. Van de Woude, National Cancer Institute, Frederick, MD, and approved September 15, 1997 (received for review May 27, 1997)

Abstract

Nerve growth factor (NGF) prevents apoptosis through stimulation of the TrkA receptor protein tyrosine kinase. The downstream activation of phosphatidylinositol 3-kinase (PI 3-kinase) is essential for the inhibition of apoptosis, although this enzyme does not bind to and is not directly activated by TrkA. We have found that the addition of NGF to PC-12 cells resulted in the phosphorylation of the Grb2-associated binder-1 (Gab1) docking protein and induced the association of several SH2 domain-containing proteins, including PI 3-kinase. A substantial fraction of the total cellular PI 3-kinase activity was associated with Gab1. PC-12 cells that overexpressed Gab1 show a decreased requirement for the amount of NGF necessary to inhibit apoptosis. The expression of a Gab1 mutant that lacked the binding sites for PI 3-kinase enhanced apoptosis and diminished the protective effect of NGF. Hence, Gab1 has a major role in connecting TrkA with PI 3-kinase activation and for the promotion of cell survival by NGF.

Footnotes

↵ ‡ To whom reprint requests should be addressed. e-mail: a_wong{at}lac.jci.tju.edu.
This paper was submitted directly (Track II) to the Proceedings Office.
Abbreviations: Gab1, Grb2-associated binder-1; HA, hemagglutinin; NGF, nerve growth factor; PI 3-kinase, phosphatidylinositol 3-kinase; PDGF, platelet-derived growth factor; RPTK, receptor protein tyrosine kinase; MAPK, mitogen-activating protein kinase; SH2 and -3, src homology 2 and 3; EGF, epidermal growth factor.