The integrin complex αvβ3 participates in the adhesion of microvascular endothelial cells to fibronectin

Abstract

Fibronectin is a major adhesive glycoprotein of the vascular basement membrane. Since fibronectin is also found in the interstitium, it may be important not only for attachment but also for endothelial cell migration during neovascularization. We have analyzed how human dermal microvascular endothelial cells use their diverse set of integrin receptors to interact with this ligand. Immunofluorescent staining with specific antibodies identified both β 1 and β 3 integrin receptor complexes in focal adhesion plaques on cells adhering to immobilized fibronectin. Adhesion assays with blocking monoclonal antibodies implicated both β 1 and β 3 complexes, specifically α 5 β 1 and α v β 3, in the initial adhesion of cells to fibronectin. Finally, ligand affinity chromatography of extracts of surface radiolabeled cells established that both α 5 β 1 and α v β 3 could bind to the 110-kDa cell-binding fragment of fibronectin. An additional receptor complex composed of an α v subunit and a β 5-like subunit was also detected. These results provide evidence that microvascular endothelial cells use multiple integrin receptors, from several β families, to attach to fibronectin surfaces.