Thy-1 regulates fibroblast focal adhesions, cytoskeletal organization and migration through modulation of p190 RhoGAP and Rho GTPase activity.
The precise biological role of Thy-1, a glycophosphatidyl-inositol (GPI)-linked cell surface glycoprotein in non-caveolar lipid raft microdomains, remains enigmatic. Evidence suggests that Thy-1 affects intracellular signaling through src-family protein kinases, and modulates adhesive and migratory events, such as thymocyte adhesion and neurite extension. Primary fibroblasts sorted based on presence or absence of cell surface Thy-1 display strikingly distinct morphologies and differ with respect to production of and response to cytokines and growth factors. It is unclear the extent to which Thy-1 mediates these differences. Findings reported here indicate a novel role for Thy-1 in regulating the activity of Rho GTPase, a critical regulator of cellular adhesion and cytoskeletal organization. Endogenous or heterologous Thy-1 expression promotes focal adhesion and stress fiber formation, characteristic of increased Rho GTPase activity, and inhibits migration. Immunoblotting following transfection of RFL6 fibroblasts with Thy-1 demonstrates that Thy-1 expression inhibits src-family protein tyrosine kinase (SFK) activation, resulting in decreased phosphorylation of p190 Rho GTPase-activating protein (GAP). This results in a net increase in active Rho, and increased stress fibers and focal adhesions. We therefore conclude that Thy-1 surface expression regulates fibroblast focal adhesions, cytoskeletal organization and migration by modulating the activity of p190 RhoGAP and Rho GTPase.
Barker
Thomas H
TH
Department of Medicine, The University of Alabama at Birmingham, Birmingham, AL 35294, USA.
Grenett
Hernan E
HE
MacEwen
Mark W
MW
Tilden
Samuel G
SG
Fuller
Gerald M
GM
Settleman
Jeffrey
J
Woods
Anne
A
Murphy-Ullrich
Joanne
J
Hagood
James S
JS
D000818:Animals; D002465:Cell Movement; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000378:metabolism*; D004268:DNA-Binding Proteins; D004789:Enzyme Activation; D005347:Fibroblasts / Q000201:enzymology / Q000378:metabolism*; D022001:Focal Adhesions / Q000378:metabolism*; D020690:GTPase-Activating Proteins; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D008168:Lung / Q000166:cytology; D051379:Mice; D018345:Mice, Knockout; D008954:Models, Biological; D009687:Nuclear Proteins / Q000378:metabolism*; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D051381:Rats; D011917:Rats, Inbred Lew; D012097:Repressor Proteins; D018800:Thy-1 Antigens / Q000378:metabolism*; D020741:rho GTP-Binding Proteins / Q000378:metabolism*; D019061:src-Family Kinases / Q000037:antagonists & inhibitors
C513041:Arhgap35 protein, mouse; C513040:Arhgap35 protein, rat; C513042:Arhgap5 protein, mouse; D004268:DNA-Binding Proteins; D020690:GTPase-Activating Proteins; D020662:Guanine Nucleotide Exchange Factors; D009687:Nuclear Proteins; D012097:Repressor Proteins; D018800:Thy-1 Antigens; D011505:Protein-Tyrosine Kinases; D019061:src-Family Kinases; D020741:rho GTP-Binding Proteins