MICROFILAMENT ASSEMBLY IS REQUIRED FOR ANTI-IGM DEPENDENT MAPK AND P90(RSK) ACTIVATION IN HUMAN B-LYMPHOCYTES

Mitogen-activated protein kinases (MAPK) are important mediators of si gnal transduction from the cell surface to the nucleus. These MAPK pat hways serve different receptor-mediated signaling pathways leading to dual phosphorylation on serine/threonine and tyrosine residues. The me chanisms linking cytoplasmic MAPK activation to later events is still unclear. In this study we demonstrate that the microfilament system ha s an active role in MAPK activation. Cross-linking of surface IgM or d irect activation of PKC with PMA resulted in time and concentration-de pendent increases in F-actin content, MAPK (p42(erk-2)) activation, an d phosphorylation of p90(rsk). Pretreatment of the B cells with cytoch alasin D or botulinum C-2 toxin, microfilament-disrupting agents, prev ented the increases in F-actin content as well as MAPK and p90(rsk) ac tivation. These data indicate a role for the microfilament system in t he complex and divergent functions of MAPK. (C) 1995 Academic Press, I nc.