|
|
|
|
A more recent version of this article appeared on September 1, 2004
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Submitted on March 29, 2004
Accepted on June 18, 2004
,
*Department of Surgery and the Cancer Institute of New Jersey, RWJMS-University of Medicine and Dentistry of New Jersey, New Brunswick, NJ 08903;
Biosource International, Hopkinton, MA 01748
Monitoring Editor: Mark Ginsberg
Vinculin is a conserved actin binding protein localized in focal adhesions and cell-cell junctions. Here we report that vinculin is tyrosine phosphorylated in platelets spread on fibrinogen and that the phosphorylation is Src kinases dependent. The phosphorylation of vinculin on tyrosine was reconstituted in vanadate treated COS-7 cells coexpressing c-Src. The tyrosine phosphorylation sites in vinculin were mapped to residues 100 and 1065. A phosphorylation specific antibody directed against tyrosine residue 1065 reacted with phosphorylated platelet vinculin but failed to react with vinculin from unstimulated platelet lysates. Tyrosine residue 1065 located in the vinculin tail domain was phosphorylated by c-Src in vitro. When phosphorylated, the vinculin tail exhibited significantly less binding to the vinculin head domain than the unphosphorylated tail. In contrast, the phosphorylation did not enhance the binding of vinculin to actin in vitro. A double vinculin mutant protein Y100F/Y1065F localized to focal adhesion plaques. Wild-type vinculin and single tyrosine phosphorylation mutants proteins, Y100F and Y1065F, were significantly more effective at rescuing the spreading defect of vinculin null cells than the double mutant Y100F/Y1065F. The phosphorylation of vinculin by Src kinases may be one mechanism by which these kinases regulate actin filament assembly and cell spreading.
Corresponding author. E-mail: haimovic{at}umdnj.edu