A critical role of conventional protein kinase C in morphological changes of rodent mast cells

In mast cells, crosslinking the high‐affinity IgE receptor (FcεRI) results in a dynamic reorganization of the actin cytoskeleton that is associated with membrane ruffling. Although the signaling involved in degranulation has been well described, it is less understood in morphological changes. In this study, we investigated the specific role of conventional protein kinase C (cPKC), a crucial signal for degranulation, in antigen‐induced membrane ruffling of mast cells. In RBL‐2H3 mast cells, antigen induced a long‐lasting membrane ruffling, which was blocked with late‐added Gö6976, a specific cPKC inhibitor, indicating that sustained activation of cPKC is required for maintaining the reaction. Immunofluorescence staining of endogenous PKCα/β and real‐time imaging of transfected green fluorescent protein‐tagged PKCα/β demonstrated that in response to antigen both PKCα and PKCβI quickly translocated to the plasma membrane and were colocalized with actin filaments at the ruffling sites. These reactions were blocked by expression of kinase‐negative PKCβI, but not kinase‐negative PKCα, and by treatment with a specific PKCβ inhibitor, LY333531. The adhesion, spreading and membrane ruffling of mouse bone marrow‐derived mast cells (BMMCs), which are mostly nonadhesive, were promoted by both antigen and thymeleatoxin. Treatment with Gö6976 abolished all these reactions. Antigen‐mediated migration of BMMC was also sensitive to Gö6076 and LY333531. In addition, BMMC adhesion by and migration toward stem cell factor were shown to be dependent on cPKC. Thus, cPKC, at least PKCβ subtype, may be critical for the dynamic morphological changes that lead to the migration of mast cells.