Human microvascular endothelial cells use beta 1 and beta 3 integrin receptor complexes to attach to laminin.
Microvascular endothelial cells (MEC) use a set of surface receptors to adhere not only to the vascular basement membrane but, during angiogenic stimulation, to the interstitium. We examined how cultured human MEC interact with laminin-rich basement membranes. By using a panel of monoclonal antibodies, we found that MEC cells express a number of integrin-related receptor complexes, including alpha 1 beta 1, alpha 2 beta 1, alpha 3 beta 1, alpha 5 beta 1, alpha 6 beta 1, alpha V beta 3. Attachment to laminin, a major adhesive protein in basement membranes, was studied in detail. Blocking monoclonal antibodies specific to different integrin receptor complexes showed that the alpha 6 beta 1 complex was important for MEC adhesion to laminin. In addition, blocking antibody also implicated the vitronectin receptor (alpha V beta 3) in laminin adhesion. We used ligand affinity chromatography of detergent-solubilized receptor complexes to further define receptor specificity. On laminin-Sepharose columns, we identified several integrin receptor complexes whose affinity for the ligand was dependent on the type of divalent cation present. Several beta 1 complexes, including alpha 1 beta 1, alpha 2 beta 1, and alpha 6 beta 1 bound strongly to laminin. In agreement with the antibody blocking experiments, alpha V beta 3 was found to bind well to laminin. However, unlike binding to its other ligands (e.g., vitronectin, fibrinogen, von Willebrand factor), alpha V beta 3 interaction with laminin did not appear to be Arg-Gly-Asp (RGD) sensitive. Finally, immunofluorescent staining demonstrated both beta 1 and beta 3 complexes in vinculin-positive focal adhesion plaques on the basal surface of MEC adhering to laminin-coated substrates. The results indicate that both these subfamilies of integrin heterodimers are involved in promoting MEC adhesion to laminin and the vascular basement membrane.
Kramer
R H
RH
Department of Stomatology, University of California, San Francisco 94143-0512.
Cheng
Y F
YF
Clyman
R
R
D000911:Antibodies, Monoclonal; D001485:Basement Membrane / Q000502:physiology; D002448:Cell Adhesion / Q000502:physiology; D004730:Endothelium, Vascular / Q000166:cytology / Q000502:physiology*; D006801:Humans; D066298:In Vitro Techniques; D016023:Integrins / Q000378:metabolism*; D007797:Laminin / Q000378:metabolism*; D046911:Macromolecular Substances; D008833:Microcirculation / Q000166:cytology; D011485:Protein Binding; D011971:Receptors, Immunologic / Q000378:metabolism; D019030:Receptors, Vitronectin
D000911:Antibodies, Monoclonal; D016023:Integrins; D007797:Laminin; D046911:Macromolecular Substances; D011971:Receptors, Immunologic; D019030:Receptors, Vitronectin