Association of the amino-terminal half of c-Src with focal adhesions alters their properties and is regulated by phosphorylation of tyrosine 527.
We have characterized the mechanism by which the subcellular distribution of c-Src is controlled by the phosphorylation of tyrosine 527. Mutation of this tyrosine dramatically redistributes c-Src from endosomal membranes to focal adhesions. Redistribution to focal adhesions occurs independently of kinase activity and cellular transformation. In cells lacking the regulatory kinase (CSK) that phosphorylates tyrosine 527, c-Src is also found predominantly in focal adhesions, confirming that phosphorylation of tyrosine 527 affects the location of c-Src inside 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-terminal half. Point mutations and deletions in the first 251 amino acids of c-Src reveal that association with focal adhesions requires the myristylation site needed for membrane attachment, as well as the SH3 domain. Expression of the amino-terminal region alters both the structural and biochemical properties of focal adhesions. Focal adhesions containing this non-catalytic portion of c-Src are larger and exhibit increased levels of phosphotyrosine staining. Our results suggest that c-Src may regulate focal adhesions and cellular adhesion by a kinase-independent mechanism.
Kaplan
K B
KB
Department of Microbiology and Immunology, University of California, San Francisco 94143.
Bibbins
K B
KB
Swedlow
J R
JR
Arnaud
M
M
Morgan
D O
DO
Varmus
H E
HE
D000595:Amino Acid Sequence; D000818:Animals; D001692:Biological Transport; D015815:Cell Adhesion Molecules / Q000737:chemistry / Q000378:metabolism*; D002460:Cell Line; D051379:Mice; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011485:Protein Binding; D021382:Protein Sorting Signals / Q000502:physiology*; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000737:chemistry / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013347:Subcellular Fractions / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism*
D015815:Cell Adhesion Molecules; D021382:Protein Sorting Signals; D014443:Tyrosine; D016392:Proto-Oncogene Proteins pp60(c-src)