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Dispensable role of focal adhesion kinase in integrin alpha9beta1 mediated cell migration
Author(s) -
Gupta Shiv Kumar,
Vlahakis Nicholas E
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.1029.2
Subject(s) - proto oncogene tyrosine protein kinase src , focal adhesion , tyrosine protein kinase csk , microbiology and biotechnology , ptk2 , tyrosine phosphorylation , integrin , tyrosine kinase , receptor tyrosine kinase , sh3 domain , sh2 domain , phosphorylation , chemistry , biology , cancer research , signal transduction , mitogen activated protein kinase kinase , protein kinase a , biochemistry , cell
Focal adhesion kinase (FAK) is a key signaling protein for integrin mediated cell migration. Auto phosphorylation of FAK at tyrosine‐397 is induced upon integrin activation, which then serves as a high affinity binding site for src tyrosine kinase forming a FAK‐src complex. Fak‐Src complex is a potent regulator of subsequent downstream signaling for enhanced cell migration. Using stable lines of SW480 colon carcinoma cells expressing integrin subunit α9, we explored the importance of the FAK‐Src complex in α9β1‐dependent cell migration. We found that ligand binding of α9β1 rapidly activated src tyrosine kinase; with concomitant tyrosine phosphorylation of FAK, p130Cas and Erk MAP kinase; inhibition of src tyrosine kinase or ErkMAP kinase activity decreased α9β1‐dependent cell migration. Surprisingly, activated α9β1 induced phosphorylation of iNOS resulting in NO production and associated NO‐mediated cell migration. Src tyrosine kinase appeared to signal upstream of iNOS, Erk, FAK and p130Cas as its inhibition blocked α9β1‐dependent tyrosine phosphorylation of these molecules. FAK binding to src was however not required for integrin α9β1 induced cell migration; and FAK inhibition (by siRNA) did not alter integrin α9β1 induced src activation and phosphorylation of Erk, p130Cas, iNOS. Analysis of Chinese Hamester Overian cells that expressed intact or mutant forms of integrin α9‐subunit showed that the α9‐cytoplasmic domain was critical for α9β1 induced src tyrosine kinase activation, downstream signaling events and ultimately cell migration. Taken together these results suggest that src, in a FAK independent manner, serves as a key early signaling protein for α9β1‐dependent cell migration; it is activated at the α9 ‐cytoplasmic domain and subsequently initiates multiple signaling intermediates, including NO, to induce cell migration.