PROTEIN-KINASE-C CHIMERAS - CATALYTIC DOMAINS OF ALPHA-PROTEIN-KINASE-C AND BETA(II)-PROTEIN-KINASE-C CONTAIN DETERMINANTS FOR ISOTYPE-SPECIFIC FUNCTION

Protein kinase C (PKC) is involved in the proliferation and differenti ation of many cell types, In human erythroleukemia (K-562) cells, the PKC isoforms alpha and beta(I)I play distinct functional roles, alpha PKC is involved in phorbol 12-myristate 13-acetate-induced cytostasis and megakaryocytic differentiation, whereas beta(I)I PKC is required f or proliferation, To identify regions within alpha and beta(I)I PKC th at allow participation in these divergent pathways, we constructed chi meras in which the regulatory and catalytic domains of alpha and beta( I)I PKC were exchanged, These PKC chimeras can be stably expressed, ex hibit enzymatic properties similar to native alpha and beta(I)I PKC in vitro, and participate in alpha and beta(I)I PKC isotype-specific pat hways in K-562 cells. Expression of the beta/alpha PKC chimera induces cytostasis in the same manner as overexpression of wild-type alpha PK C. In contrast, the alpha/beta(I)I PKC chimera, like wild-type beta(I) I PKC, selectively translocates to the nucleus acid leads to increased phosphorylation of the nuclear envelope polypeptide lamin B in respon se to bryostatin-1. Therefore, the catalytic domains of alpha and beta (I)I PKC contain determinants important for alpha and beta(I)I PKC iso type function, These results suggest that the catalytic domain represe nts a potential target for modulating PKC isotype activity in vivo.