NG2 proteoglycan mediates beta1 integrin-independent cell adhesion and spreading on collagen VI.
Collagens V and VI have been previously identified as specific extracellular matrix (ECM) ligands for the NG2 proteoglycan. In order to study the functional consequences of NG2/collagen interactions, we have utilized the GD25 cell line, which does not express the major collagen-binding beta(1) integrin heterodimers. Use of these cells has allowed us to study beta(1) integrin-independent phenomena that are mediated by binding of NG2 to collagens V and VI. Heterologous expression of NG2 in the GD25 line endows these cells with the capability of attaching to surfaces coated with collagens V and VI. The specificity of this effect is emphasized by the failure of NG2-positive GD25 cells to attach to other collagens or to laminin-1. More importantly, NG2-positive GD25 cells spread extensively on collagen VI. beta(1) integrin-independent extension of ruffling lamellipodia demonstrates that engagement of NG2 by the collagen VI substratum triggers signaling events that lead to rearrangement of the actin cytoskeleton. In contrast, even though collagens V and VI each bind to the central segment of the NG2 ectodomain, collagen V engagement of NG2 does not trigger cell spreading. The distinct morphological consequences of NG2/collagen VI and NG2/collagen V interaction indicate that closely-related ECM ligands for NG2 differ in their ability to initiate transmembrane signaling via engagement of the proteoglycan.
Tillet
Emmanuelle
E
Institut de Biologie et Chimie des Protéines, CNRS UMR 5086-Université Lyon I, 7 passage du Vercors, 69367 Lyon cedex 07, France. etillet@cea.fr
Gential
Blandine
B
Garrone
Robert
R
Stallcup
William B
WB
D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D000941:Antigens / Q000378:metabolism*; D015153:Blotting, Western; D002448:Cell Adhesion / Q000502:physiology*; D002461:Cell Line, Transformed / Q000378:metabolism; D024142:Collagen Type VI / Q000378:metabolism*; D018076:DNA, Complementary / Q000096:biosynthesis; D016326:Extracellular Matrix Proteins / Q000502:physiology; D005353:Fibronectins / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D006801:Humans; D007797:Laminin / Q000378:metabolism*; D008024:Ligands; D011509:Proteoglycans / Q000378:metabolism*; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D014162:Transfection; D000099216:Chondroitin Sulfate Proteoglycan 4
D000911:Antibodies, Monoclonal; D000941:Antigens; D024142:Collagen Type VI; D018076:DNA, Complementary; D016326:Extracellular Matrix Proteins; D005353:Fibronectins; D007797:Laminin; D008024:Ligands; D011509:Proteoglycans; D011994:Recombinant Proteins; D000099216:Chondroitin Sulfate Proteoglycan 4; C121346:laminin 1