CD43 INTERACTS WITH MOESIN AND EZRIN AND REGULATES ITS REDISTRIBUTIONTO THE UROPODS OF T-LYMPHOCYTES AT THE CELL-CELL CONTACTS

Chemokines as well as the signaling through the adhesion molecules int ercellular adhesion molecule (ICAM)-3 and CD43 are able to induce in T lymphocytes their switching from a spherical to a polarized motile mo rphology, with the formation of a uropod at the rear of the cell. We i nvestigated here the role of CD43 in the regulation of T-cell polarity , CD43-cytoskeletal interactions, and lymphocyte aggregation. Pro-acti vatory anti-CD43 monoclonal antibody (MoAb) induced polarization of T lymphocytes with redistribution of CD43 to the uropod and the CCR2 che mokine receptor to the leading edge of the cell. Immunofluorescence an alysis showed that all three ezrin-radixin-moesin (ERM) actin-binding proteins localized in the uropod of both human T lymphoblasts stimulat ed with anti-CD43 MoAb and tumor infiltrating T lymphocytes. Radixin l ocalized at the uropod neck, whereas ezrin and moesin colocalized with CD43 in the uropod. Biochemical analyses showed that ezrin and moesin coimmunoprecipitated with CD43 in T lymphoblasts. Furthermore, in the se cells, the CD43-associated moesin increased after stimulation throu gh CD43. The interaction of moesin and ezrin with CD43 was specificall y mediated by the cytoplasmic domain of CD43, as shown by precipitatio n of both ERM proteins with a GST-fusion protein containing the CD43 c ytoplasmic tail. Videomicroscopy analysis of homotypic cell aggregatio n induced through CD43 showed that cellular uropods mediate cell-cell contacts and lymphocyte recruitment. Immunofluorescence microscopy per formed in parallel showed that uropods enriched in CD43 and moesin loc alized at the cell-cell contact areas of cell aggregates. The polariza tion and homotypic cell aggregation induced through CD43 was prevented by butanedione monoxime, indicating the involvement of myosin cytoske leton in these phenomena. Altogether, these data indicate that CD43 pl ays an important regulatory role in remodeling T-cell morphology, like ly through its interaction with actin binding proteins ezrin and moesi n. In addition, the redistribution of CD43 to the uropod region of mig rating lymphocytes and during the formation of cell aggregates togethe r with the enhancing effect of anti-CD43 antibodies on lymphocyte cell recruitment suggest that CD43 plays a key role in the regulation of c ell-cell interactions during lymphocyte traffic. (C) 1998 by The Ameri can Society of Hematology.