FUNCTIONAL REGULATION OF THE HUMAN INTEGRIN VLA-1 (CD49A CD29) BY DIVALENT-CATIONS AND STIMULATORY BETA-1 ANTIBODIES/

We have investigated the regulation by divalent cations Mg2+, Ca2+ and Mn2+ of the functional activity of the human integrin VLA-1 expressed on neuroblastoma NB100 cells. VLA-1-mediated adhesion of NB100 cells to ligand collagen type I was supported by either mM concentrations of extracellular Mg2+ or mu M levels of Mn2+. In contrast, Ca2+ alone di d not induce activation of VLA-1 but exerted a potent inhibitory effec t on the Mg2+-supported cell adhesion. We have also demonstrated that VLA-1 can be directly activated by the stimulatory monoclonal antibody TS2/16 specific for the integrin beta 1 subunit, resulting in effecti ve adhesion of NB100 cells to type I collagen. This study has been pos sible by using a novel blocking VLA-alpha 1 specific monoclonal antibo dy, 5E8D9.