Regulation of Early Events in Integrin Signaling by Protein Tyrosine Phosphatase SHP-2

Abstract

The nontransmembrane protein tyrosine phosphatase SHP-2 plays a critical role in growth factor and cytokine signaling pathways. Previous studies revealed that a fraction of SHP-2 moves to focal contacts upon integrin engagement and that SHP-2 binds to SHP substrate 1 (SHPS-1)/SIRP-1α, a transmembrane glycoprotein with adhesion molecule characteristics (Y. Fujioka et al., Mol. Cell. Biol. 16:6887–6899, 1996; M. Tsuda et al., J. Biol. Chem. 273:13223–13229). Therefore, we asked whether SHP2–SHPS-1 complexes participate in integrin signaling. SHPS-1 tyrosyl phosphorylation increased upon plating of murine fibroblasts onto specific extracellular matrices. Both in vitro and in vivo studies indicate that SHPS-1 tyrosyl phosphorylation is catalyzed by Src family protein tyrosine kinases (PTKs). Overexpression of SHPS-1 in 293 cells potentiated integrin-induced mitogen-activated protein kinase (MAPK) activation, and potentiation required functional SHP-2. To further explore the role of SHP-2 in integrin signaling, we analyzed the responses of SHP-2 exon 3^−/− and wild-type cell lines to being plated on fibronectin. Integrin-induced activation of Src family PTKs, tyrosyl phosphorylation of several focal adhesion proteins, MAPK activation, and the ability to spread on fibronectin were defective in SHP-2 mutant fibroblasts but were restored upon SHP-2 expression. Our data suggest a positive-feedback model in which, upon integrin engagement, basal levels of c-Src activity catalyze the tyrosyl phosphorylation of SHPS-1, thereby recruiting SHP-2 to the plasma membrane, where, perhaps by further activating Src PTKs, SHP-2 transduces positive signals for downstream events such as MAPK activation and cell shape changes.

ACKNOWLEDGMENTS

E.-S.O., H.G., T.M.S., and J.F.T. contributed equally to this work.

This work was supported by NIH grants R01 CA49152 (to B.G.N.), R01 CA75621 (to S.M.T.), and R01 DK43051 (to B.B.K.) and by grants from the Medical Research Council of Canada and the National Cancer Institute of Canada (to T.P.). T.P. is an International Scholar of the Howard Hughes Medical Institute. H.G. was supported by NIH NRSA CA72144, J.F.T. was supported by a postdoctoral fellowship from the Leukemia Society, and S.H. was the recipient of a postdoctoral fellowship from The Medical Foundation. E.U.F. was supported by a Physician Scientist Award (NIA no. AG 00294).

We are grateful to C. Newgard for providing adenovirus plasmids, Mike Eck for the kind gift of recombinant c-Src, Karen Zoller and Cindy Miranti for helpful discussions, and Joan S. Brugge and Alana M. O’Reilly for insightful comments and critical reading of the manuscript.