Fibronectin/integrin interaction induces tyrosine phosphorylation of a 120-kDa protein

Cell Regul. 1991 Nov;2(11):951-64. doi: 10.1091/mbc.2.11.951.


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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 3T3 Cells
  • Animals
  • Cell Adhesion*
  • Fibronectins / metabolism*
  • Fluorescent Antibody Technique
  • Integrins / metabolism*
  • Mice
  • Molecular Weight
  • Peptide Fragments / metabolism
  • Phosphoproteins / chemistry
  • Phosphoproteins / metabolism*
  • Phosphorylation
  • Phosphotyrosine
  • Protein Binding
  • Signal Transduction
  • Time Factors
  • Tyrosine / analogs & derivatives*
  • Tyrosine / metabolism


  • Fibronectins
  • Integrins
  • Peptide Fragments
  • Phosphoproteins
  • Phosphotyrosine
  • Tyrosine