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The N‐terminal region of GAP regulates cytoskeletal structure and cell adhesion.
Author(s) -
McGlade J.,
Brunkhorst B.,
Anderson D.,
Mbamalu G.,
Settleman J.,
Dedhar S.,
RozakisAdcock M.,
Chen L.B.,
Pawson T.
Publication year - 1993
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1993.tb05976.x
Subject(s) - biology , gtpase activating protein , guanine nucleotide exchange factor , sh2 domain , microbiology and biotechnology , tyrosine phosphorylation , sh3 domain , cytoskeleton , phosphorylation , platelet derived growth factor receptor , focal adhesion , gtpase , receptor tyrosine kinase , receptor , signal transduction , biochemistry , growth factor , g protein , cell
Ras GTPase activating protein (GAP) possesses a C‐terminal domain that interacts with GTP‐bound Ras, and an N‐terminal region containing two SH2 domains and an SH3 domain. In addition to its association with Ras, GAP binds stably to autophosphorylated beta PDGF receptors, and to two cytoplasmic phosphoproteins: p62, an RNA binding protein, and p190, which possesses GAP activity towards small guanine nucleotide binding proteins in the Rho/Rac family. To define the region of GAP that mediates these interactions with cellular phosphoproteins, and to investigate the biological significance of these complexes, a truncated GAP polypeptide (GAP‐N) containing residues 1–445 was stably expressed in Rat‐2 fibroblasts. GAP‐N contains the SH2 and SH3 domains, but lacks the Ras GTPase activating domain. Stimulation of cells expressing GAP‐N with PDGF induced association of GAP‐N with the beta PDGF receptor, and phosphorylation of GAP‐N on tyrosine, consistent with the notion that GAP SH2 domains direct binding to the autophosphorylated beta PDGF receptor in vivo. GAP‐N bound constitutively to p190 in both serum‐deprived and growth factor‐stimulated cells. This GAP‐N‐p190 complex had Rho GAP activity in vitro. The expression of GAP‐N in Rat‐2 cells correlated with changes in the cytoskeleton and in cell adhesion, typified by the disruption of action stress fibres, a reduction in focal contacts, and an impaired ability to adhere to fibronectin. These results suggest that the N‐terminal domain of GAP can direct interactions with cellular phosphoproteins in vivo, and thereby exert an effector function which modulates the cytoskeleton and cell adhesion.(ABSTRACT TRUNCATED AT 250 WORDS)