LIGATION OF CD53 OX44, A TETRASPAN ANTIGEN, INDUCES HOMOTYPIC ADHESION MEDIATED BY SPECIFIC CELL-CELL INTERACTIONS/

The CD53 antigen is a member of the tetraspan family of proteins with unknown function. Stimulation of rat IR938F B-cell lymphoma cells with monoclonal antibody MRC OX44 (anti-rat CD53) triggered a homotypic ad hesion reaction which reached a maximum effect at 24 hr. This effect o ccurred at 37 degrees C but not at 4 degrees C. Adhesion was prevented by removal of divalent cations, Ca2+ and Mg2+, with EGTA and EDTA as chelating agents. The adhesion induced by MRC OX44 was inhibited by cy cloheximide and actinomycin D, suggesting that de novo protein synthes is was required for this effect. The addition of mAb WT1 against rat L FA-1 (CD11a) antigen had no effect on adhesion, suggesting that the ce ll-cell interaction is not mediated by the expression of LFA-1 antigen . The intracellular signals required to induce adhesion were inhibited by two tyrosine kinase inhibitors, genistein and piceatannol. Wortman nin, a selective inhibitor of phosphoinositide 3-kinase activity, comp letely blocked adhesion. Two protein kinase C inhibitors, H7 and bisin dolylmaleimide, inhibited the adhesion, suggesting that part of the si gnal is mediated by PKC. Electron microscopy of aggregated cells showe d that the interaction is localized to short membrane regions, where c ontact areas of higher density in opposing zones from both cells were detected. We postulate that there is a common adhesion mechanism that is modulated by several tetraspan family members and associated protei ns. This adhesion structure might represent a novel form of cell commu nication among lymphoid cells. (C) 1997 Academic Press.