Kb. Kaplan et al., ASSOCIATION OF THE AMINO-TERMINAL HALF OF C-SRC WITH FOCAL ADHESIONS ALTERS THEIR PROPERTIES AND IS REGULATED BY PHOSPHORYLATION OF TYROSINE-527, EMBO journal, 13(20), 1994, pp. 4745-4756
We have characterized the mechanism by which the subcellular distribut
ion of c-Src is controlled by the phosphorylation of tyrosine 527. Mut
ation of this tyrosine dramatically redistributes c-Src from endosomal
membranes to focal adhesions. Redistribution to focal adhesions occur
s independently of kinase activity and cellular transformation. In cel
ls lacking the regulatory kinase (CSK) that phosphorylates tyrosine 52
7, c-Src is also found predominantly in focal adhesions, confirming th
at phosphorylation of tyrosine 527 affects the location of c-Src insid
e the cell. The first 251 amino acids of c-Src are sufficient to allow
association with focal adhesions, indicating that at least one signal
for positioning c-Src in focal adhesions resides in the amino-termina
l half. Point mutations and deletions in the first 251 amino acids of
c-Src reveal that association with focal adhesions requires the myrist
ylation site needed for membrane attachment, as well as the SH3 domain
. Expression of the aminoterminal region alters both the structural an
d biochemical properties of focal adhesions. Focal adhesions containin
g this non-catalytic portion of c-Src are larger and exhibit increased
levels of phosphotyrosine staining. Our results suggest that c-Src ma
y regulate focal adhesions and cellular adhesion by a kinase-independe
nt mechanism.