Restructuring of focal adhesion plaques by PI 3-kinase. Regulation by PtdIns (3,4,5)-p(3) binding to alpha-actinin.
Focal adhesions are an elaborate network of interconnecting proteins linking actin stress fibers to the extracellular matrix substrate. Modulation of the focal adhesion plaque provides a mechanism for the regulation of cellular adhesive strength. Using interference reflection microscopy, we found that activation of phosphoinositide 3-kinase (PI 3-kinase) by PDGF induces the dissipation of focal adhesions. Loss of this close apposition between the cell membrane and the extracellular matrix coincided with a redistribution of alpha-actinin and vinculin from the focal adhesion complex to the Triton X-100-soluble fraction. In contrast, talin and paxillin remained localized to focal adhesions, suggesting that activation of PI 3-kinase induced a restructuring of the plaque rather than complete dispersion. Furthermore, phosphatidylinositol (3,4, 5)-trisphosphate (PtdIns (3,4,5)-P(3)), a lipid product of PI 3-kinase, was sufficient to induce restructuring of the focal adhesion plaque. We also found that PtdIns (3,4,5)-P(3) binds to alpha-actinin in PDGF-treated cells. Further evidence demonstrated that activation of PI 3-kinase by PDGF induced a decrease in the association of alpha-actinin with the integrin beta subunit, and that PtdIns (3,4,5)-P(3) could disrupt this interaction in vitro. Modification of focal adhesion structure by PI 3-kinase and its lipid product, PtdIns (3,4,5)-P(3), has important implications for the regulation of cellular adhesive strength and motility.
Department of Pathology, Division of Molecular and Cellular Pathology, University of Alabama at Birmingham, Alabama 35294, USA. jeffrey.greenwood@orst.edu
J A
JA
Greenwood
A B
AB
Theibert
G D
GD
Prestwich
J E
JE
Murphy-Ullrich
D000185:Actinin / Q000378:metabolism*; D000818:Animals; D015703:Antigens, CD / Q000378:metabolism; D001692:Biological Transport; D002448:Cell Adhesion / Q000187:drug effects*; D002451:Cell Compartmentation; D002478:Cells, Cultured; D004622:Embryo, Mammalian / Q000166:cytology; D004789:Enzyme Activation; D005347:Fibroblasts / Q000166:cytology; D019012:Integrin beta1 / Q000378:metabolism; D039661:Integrin beta3; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism*; D010766:Phosphorylation; D010980:Platelet Membrane Glycoproteins / Q000378:metabolism; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D011485:Protein Binding; D051381:Rats
D015703:Antigens, CD; D019012:Integrin beta1; D039661:Integrin beta3; D018129:Phosphatidylinositol Phosphates; D010980:Platelet Membrane Glycoproteins; D010982:Platelet-Derived Growth Factor; C060974:phosphatidylinositol 3,4,5-triphosphate; D000185:Actinin; D019869:Phosphatidylinositol 3-Kinases