ABSTRACT
Although reduced expression of CD82 transmembrane protein facilitates metastasis of cancer cells, little is known about its biological function. Here we have investigated the role of CD82 in B cell lymphocyte adhesion. When IM-9 cells were engaged with anti-CD82 monoclonal antibody, they formed homotypic aggregates in a short time. This adhesion was inhibited by anti-CD11a monoclonal antibody that has been known to block LFA-1-mediated cell adhesion. The cell surface expression of LFA-1 has not been changed by CD82 engagement. Homotypic aggregation was decreased in the cells in which the level of CD82 expression was low, and it was not recovered by anti-CD99 monoclonal antibody or PMA that has been known to stimulate cell adhesion. In addition, it was recovered by Mg++ treatment that induces conformational change of LFA-1 moleucles, but not by Ca++ treatment that leads to clustering of LFA-1 on the cell surface. CD82-induced cell aggregation was dramatically abrogated by addition of the phos-phatidylinositol 3-kinase (PI3-K) inhibitor LY294002 or p38 mitogen-activated protein kinase (MAPK) inhibitor SB203580. Taken together, these results suggest that CD82 molecule may fascilitate adhesion of lymphocytes by inducing conformational change of LFA-1 to pro-adhesive structure through PI3-K or p38 MAPK signal pathway.