Previous Article | Next Article ![]()
Mol. Cell. Biol., Oct 1996, 5623-5633, Vol 16, No. 10
DD Schlaepfer and T Hunter
Focal adhesion kinase (FAK) is a nonreceptor protein-tyrosine kinase (PTK)
that associates with integrin receptors and participates in extracellular
matrix-mediated signal transduction events. We showed previously that the
c-Src nonreceptor PTK and the Grb2 SH2/SH3 adaptor protein bound directly
to FAK after fibronectin stimulation (D. D. Schlaepfer, S.K. Hanks, T.
Hunter, and P. van der Geer, Nature [London] 372:786-791, 1994). Here, we
present evidence that c-Src association with FAK is required for Grb2
binding to FAK. Using a tryptic phosphopeptide mapping approach, the in
vivo phosphorylation of the Grb2 binding site on FAK (Tyr-925) was detected
after fibronectin stimulation of NIH 3T3 cells and was constitutively
phosphorylated in v- Src-transformed NIH 3T3 cells. In vitro, c-Src
phosphorylated FAK Tyr- 925 in a glutathione S-transferase-FAK C-terminal
domain fusion protein, whereas FAK did not. Using epitope-tagged FAK
constructs, transiently expressed in human 293 cells, we determined the
effect of site-directed mutations on c-Src and Grb2 binding to FAK.
Mutation of FAK Tyr-925 disrupted Grb2 binding, whereas mutation of the
c-Src binding site on FAK (Tyr-397) disrupted both c-Src and Grb2 binding
to FAK in vivo. These results support a model whereby Src-family PTKs are
recruited to FAK and focal adhesions following integrin-induced
autophosphorylation and exposure of FAK Tyr-397. Src-family binding and
phosphorylation of FAK at Tyr-925 creates a Grb2 SH2-domain binding site
and provides a link to the activation of the Ras signal transduction
pathway. In Src-transformed cells, this pathway may be constitutively
activated as a result of FAK Tyr-925 phosphorylation in the absence of
integrin stimulation.
Copyright © 1996, American Society for Microbiology
Evidence for in vivo phosphorylation of the Grb2 SH2-domain binding site on focal adhesion kinase by Src-family protein-tyrosine kinases [published erratum appears in Mol Cell Biol 1996 Dec;16(12):7182-4]
Molecular Biology and Virology Laboratory, Salk Institute for Biological Studies, La Jolla, California 92037, USA.
This article has been cited by other articles:
Copyright © 2009 by the American Society for Microbiology. For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»