ENDOTHELIAL-CELL ATTACHMENT AND SPREADING ON HUMAN TENASCIN IS MEDIATED BY ALPHA-2-BETA-1 AND ALPHA-V-BETA-3 INTEGRINS

Human umbilical vein endothelial cells were found to attach and partia lly spread on human tenascin. The attachment of endothelial cells to t enascin results in elongated cells with interconnecting processes and is distinct from the flattened appearance of endothelial cells on fibr onectin, collagen, vitronectin or laminin substrata, suggesting a role for tenascin in modulating cell adhesion and motility. Endothelial at tachment to tenascin was partially inhibitable by the SRRGDMS peptide derived from human tenascin and completely inhibitable by anti-integri n antibodies to alpha2beta1 and alpha(V)beta3. Endothelial cell attach ment to tenascin could be inhibited up to 80% with anti-alpha2 and ant i-beta1 monoclonal antibodies P1E6 and P4C10, respectively, and this w as associated with a complete loss in cell spreading. In contrast, pre treatment of endothelial cells with the anti-alpha(V)beta3 monoclonal antibody LM609, resulted in a 35% inhibition in cell attachment but di d not alter cell spreading. In combination the anti-alpha2 and anti-al pha(V)beta3 antibodies, could completely abrogate cell spreading and a ttachment to tenascin-coated surfaces. Affinity purification of I-125- labeled endothelial cell extract on a tenascin matrix column followed by immunoprecipitation with monoclonal antibodies to different integri n alpha and beta subunits resulted in the identification of alpha2beta 1 and alpha(V)beta3 integrins, respectively, as tenascin binding recep tors. Collagen affinity-purified alpha2beta1 receptor from endothelial cells bound not only to collagen and laminin but also to tenascin in a radio receptor binding assay. The results demonstrate that alpha2bet a1 and alpha(V)beta3 mediate distinct endothelial cell interactions wi th tenascin; cell spreading and cell binding, respectively. Binding by alpha(V)beta3 is mediated by the SRRGDMS site on tenascin, whereas th e alpha2beta1 binding site remains undefined. The interaction Of alpha 2beta1 and alpha(V)beta3 with tenascin may be regulated in a cell type -specific manner as evidenced by the binding of endothelial cell alpha 2beta1 and alpha(V)beta3 to tenascin, and the lack of binding by the s ame receptors on osteosarcoma MG63 to tenascin.