VLA‐2 is a collagen receptor on endothelial cells

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Abstract
Summary: In order to identify cell‐substrate adhesion receptors on vascular endothelium, murine monoclonal antibodies (MoAb) were raised against human umbilical vein endothelial cells (HUVE). One anti‐HUVE MoAb, RMAC11, identified the adhesion receptor VLA‐2 as it immunoprecipitated a non‐covalently linked heterodimer of 160 kD and 130 kD, which was identical to the heterodimer immunoprecipitated by the anti‐VLA‐2 MoAb, 12F1 and 5E8, Furthermore, proteolytic peptide maps of the VLA‐2 α‐ and β‐chains were highly homologous with those of the RMAC11‐recognized molecule. However, unlike other VLA‐2 MoAb, RMAC11 also identified an 85 kD band which migrated to 90 kD under reducing conditions. This band was most likely a fragment of the 160 kD α‐chain as a similar α‐chain derived fragment has been demonstrated in the immunoprecipitates of some VLA‐4 reactive monoclonals. However the possibility that this may be a novel molecule associated with VLA‐2 has not been excluded. In vitro assays of HUVE adhesion to collagen types 1 and 4, laminin and fibronectin showed that RMAC11 blocked adhesion to collagen (types 1 and 4) and laminin, but had no effect on HUVE adhesion to fibronectin, confirming that VLA‐2 is a collagen and laminin receptor for HUVE.