Integrin-mediated activation of focal adhesion kinase is independent of focal adhesion formation or integrin activation. Studies with activated and inhibitory beta3 cytoplasmic domain mutants. J Biol Chem 1997 Sep 05;272(36):22538-47
Date
09/05/1997Pubmed ID
9278407DOI
10.1074/jbc.272.36.22538Scopus ID
2-s2.0-0030953445 (requires institutional sign-in at Scopus site) 71 CitationsAbstract
Integrin alphaIIbbeta3 functions as the fibrinogen receptor on platelets and mediates platelet aggregation and clot retraction. Among the events that occur during either "inside-out" or "outside-in" signaling through alphaIIbbeta3 is the phosphorylation of focal adhesion kinase (pp125(FAK)) and the association of pp125(FAK) with cytoskeletal components. To examine the role of pp125(FAK) in these integrin-mediated events, pp125(FAK) phosphorylation and association with the cytoskeleton was determined in cells expressing two mutant forms of alphaIIbbeta3: alphaIIbbeta3(D723A/E726A), a constitutively active integrin in which the putative binding site for pp125(FAK) is altered, and alphaIIbbeta3(F727A/K729E/F730A), in which the putative binding site for alpha-actinin is altered. Both mutants were expressed on the cell surface and were able to bind ligand, either spontaneously or upon activation. Whereas cells expressing alphaIIbbeta3(D723A/E726A) were able to form focal adhesions and stress fibers upon adherence to fibrinogen, cells expressing alphaIIbbeta3(F727A/K729E/F730A) adhere to fibrinogen, but had reduced focal adhesions and stress fibers. pp125(FAK) is recruited to focal adhesions in adherent cells expressing alphaIIbbeta3(D723A/E726A) and is phosphorylated in adherent cells or in cells in suspension in the presence of fibrinogen. In adherent cells expressing alphaIIbbeta3(F727A/K729E/F730A), pp125(FAK) was phosphorylated despite reduced formation of focal adhesions and stress fibers. We conclude that activation of pp125(FAK) can be dissociated from two important events in integrin signaling, the assembly of focal adhesions in adherent cells and integrin activation following ligand occupation.
Author List
Lyman S, Gilmore A, Burridge K, Gidwitz S, White GC 2ndAuthor
Gilbert C. White MD Professor in the Medicine department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
Amino Acid SequenceAnimals
Base Sequence
CHO Cells
Cell Adhesion
Cell Adhesion Molecules
Cricetinae
Cytoplasm
DNA, Complementary
Enzyme Activation
Focal Adhesion Protein-Tyrosine Kinases
Molecular Sequence Data
Mutagenesis
Phosphorylation
Platelet Glycoprotein GPIIb-IIIa Complex
Protein-Tyrosine Kinases
Recombinant Proteins