Nuclear translocation of beta II PKC isoenzyme in phorbol ester-stimulated KM-3 pre-B human leukemic cells

Members of the protein kinase C (PKC) family play a key role in regulating cell growth and differentiation in response to several stimuli, including hormones, neurotransmitters, and growth factors. The different properties and substrate specificity of the PKC isoforms are not fully understood, and they are assumed to have specific functions in intracellular signaling. In lymphoid cells, the effects of PMA and Ca2+ ionophore, singly or in combination, on activation and expression of Ca(2+)-dependent PKC at the level of protein and messenger RNA have been examined. Starting from these observations and the possibility that differential isoenzyme expression might contribute to the differences in phorbol ester sensitivity of lymphoid cells, it seemed worthwhile to investigate the expression and the modulation of PKC isoforms in KM-3 cells, a human pre-B cell line, upon treatment with phorbol 12-myristate 13-acetate (PMA). Using multiparametric analysis we detected three PKC isoforms in the KM-3 cell line: alpha, beta II, and zeta. PMA treatment causes an intranuclear translocation of the beta II isoform, via the nuclear pore complex, associated with the interchromatinic regions. These data suggest that the beta II isoenzyme may play a strategic role in signal transduction and regulation of specific gene expression in B lymphocytes.