REGULATION OF ENDOTHELIAL-CELL MOTILITY BY COMPLEXES OF TETRASPAN MOLECULES CD81 TAPA-1 AND CD151/PETA-3 WITH ALPHA-3-BETA-1 INTEGRIN LOCALIZED AT ENDOTHELIAL LATERAL JUNCTIONS/

Cell-to-cell junction structures play a key role in cell growth rate c ontrol and cell polarization. In endothelial cells (EC), these structu res are also involved in regulation of vascular permeability and leuko cyte extravasation. To identify novel components in EC intercellular j unctions, mAbs against these cells were produced and selected using a morphological screening by immunofluorescence microscopy. Two novel mA bs, LIA1/1 and VJ1/16, specifically recognized a 25-kD protein that wa s selectively localized at cell-cell junctions of EC, both in the prim ary formation of cell monolayers and when EC reorganized in the proces s of wound healing. This antigen corresponded to the recently cloned p latelet-endothelial tetraspan antigen CD151/PETA-3 (platelet-endotheli al tetraspan antigen-3), and was consistently detected at EC cell-cell contact sites. In addition to CD151/PETA-3, two other members of the tetraspan superfamily, CD9 and CD81/TAPA-1 (target of antiproliferativ e antibody-1), localized at endothelial cell-to-cell junctions. Bioche mical analysis demonstrated molecular associations among tetraspan mol ecules themselves and those of CD151/PETA-3 and CD9 with alpha 3 beta 1 integrin. Interestingly, mAbs directed to both CD151/PETA-3 and CD81 /TAPA-1 as well as mAb specific for alpha 3 integrin, were able to inh ibit the migration of ECs in the process of wound healing. The engagem ent of CD151/PETA-3 and CD81/TAPA-1 inhibited the movement of individu al ECs, as determined by quantitative time-lapse video microscopy stud ies. Furthermore, mAbs against the CD151/PETA-3 molecule diminished th e rate of EC invasion into collagen gels. In addition, these mAbs were able to increase the adhesion of EC to extracellular matrix proteins. Together these results indicate that CD81/TAPA-1 and CD151/PETA3 tetr aspan molecules are components of the endothelial lateral junctions im plicated in the regulation of cell motility, either directly or by mod ulation of the function of the associated integrin heterodimers.