CD45R, CD44 and MHC class II are signaling molecules for the cytoskeleton-dependent induction of dendrites and motility in activated B cells

Anti-CD44 or anti-MHC II antibodies bound to tissue culture plates have pre viously been shown to induce a dramatic generation of dendritic processes i n activated murine B cells. In this study, we demonstrate a similar generat ion of dendrites and cell motility in activated B cells through CD45R. The dynamic formation of dendritic processes and associated induction of cell m otility were analyzed by video microscopy and were characterized by a rapid , and multidirectional emission of dendrites with retractile behavior. The addition of cytochalasin E totally blocked dendrites formation and motility induced through either CD45R, CD44 or MHC II, suggesting that the necessar y cytoskeletal rearrangements require active polymerization of actin. Confo cal microscopy showed an accumulation of F-actin in the dendrites, as long as cells were elongating. In contrast, G-actin was localized in the perinuc lear area and also accumulated in sites where dendrites originated. Preincu bation of B cells with staurosporine (a PKC inhibitor) or BAPTA-AM (a calci um chelator) prevented these morphological changes, indicating additionally a requirement for a PKC-calcium-dependent activity. Dendrite formation and cellular motility, therefore, seem to be two manifestations of the same ph enomenon, and CD44, CD45R and MHC II appear to be signaling molecules for t he observed cytoskeleton-dependent morphological changes.