Fibronectin/integrin interaction induces tyrosine phosphorylation of a 120-kDa protein.
We describe a 120-kDa protein (pp120) that is phosphorylated on tyrosine in cells attached to fibronectin-coated surfaces. The protein appears to be located in focal contacts where it codistributes with beta 1 integrins. pp120 is distinct from the beta 1 subunit of integrins and from vinculin and alpha-actinin. pp120 is rapidly dephosphorylated in cells suspended by trypsinization but becomes rapidly phosphorylated in cells attaching and spreading on fibronectin. Attachment of cells to RGD-containing peptides, polylysine, or concanavalin A is not sufficient to induce phosphorylation of pp120. The 120-kDa cell-binding domain of fibronectin can induce some phosphorylation of pp120, but further phosphorylation occurs in the presence also of the heparin-binding domain of fibronectin. Phosphorylation of pp120 precedes, but is correlated with, subsequent cell spreading. Phosphorylation of pp120 can also be triggered by attachment of cells to anti-integrin antibodies, and this requires the cytoplasmic domain of the integrin beta 1 subunit. Thus interaction of beta 1 integrins with extracellular ligands (fibronectin or antibodies) triggers phosphorylation of an intracellular 120-kDa protein, pp120, that may be involved in the responses of cells to attachment.
Guan
J L
JL
Department of Biology, Massachusetts Institute of Technology, Cambridge 02139.
Trevithick
J E
JE
Hynes
R O
RO
D016475:3T3 Cells; D000818:Animals; D002448:Cell Adhesion; D005353:Fibronectins / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D016023:Integrins / Q000378:metabolism*; D051379:Mice; D008970:Molecular Weight; D010446:Peptide Fragments / Q000378:metabolism; D010750:Phosphoproteins / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation; D019000:Phosphotyrosine; D011485:Protein Binding; D015398:Signal Transduction; D013997:Time Factors; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000378:metabolism
D005353:Fibronectins; D016023:Integrins; D010446:Peptide Fragments; D010750:Phosphoproteins; D019000:Phosphotyrosine; D014443:Tyrosine