The subcellular distribution of protein kinase C alpha, -epsilon, and -zeta isoforms during cardiac cell differentiation

There is little information on the molecular events that control the subcel lular distribution of protein kinase C during cardiac cell differentiation. We examined protein kinase C activity and the subcellular distribution of representatives of the "classical," "novel," and "atypical" protein kinase C's in P19 murine teratoma cells induced to undergo differentiation into ca rdiac myocytes by the addition of dimethylsulfoxide to the medium (Grepin e t al., Development 124, 2387-2395, 1997), Differentiation was assessed by t he presence of striated myosin, a morphological marker for cardiac cells. A ddition of dimethyl sulfoxide to the medium resulted in the appearance of s triated myosin by 10 days postincubation. Immunolocalization and Western bl ot studies revealed that a significant proportion of protein kinase C alpha , -epsilon, and -zeta were associated with the particulate fraction in P19 cells prior to differentiation. Differentiation into cardiac cells resulted in a translocation of protein kinase C activity from the particulate fract ion to cytosol and localization of most of protein kinase C alpha, -epsilon , and -zeta to the cytoplasmic compartment. The total cellular protein kina se C activity was unaltered during differentiation. The translocation of pr otein kinase C activity during differentiation of P19 cells into cardiac my ocytes was associated with a decrease in the levels of cellular 1,2-diacyl- sn-glycerol. The cellular levels of phosphatidylserine and phosphatidylinos itol did not change during differentiation. Addition of 1,2-dioctanoyl-sn-g lycerol, a cell-permeant 1,2-diacyl-sn-glycerol analog, reversed the differ entiation-induced switch in the relative distribution of protein kinase C a ctivity and dramatically increased the association of protein kinase Ca wit h the particulate fraction. Addition of 1,2-dioctanoyl-sn-glycerol did not reverse the pattern of distribution for protein kinase C epsilon or -zeta. The results indicate that protein kinase C activity and protein kinase C al pha, -epsilon and -zeta isoforms are redistributed from the particulate to the cytosolic fraction during differentiation of P19 cells into cardiomyocy tes. The mechanism for the redistribution of protein kinase Ca may be relat ed to the reduction in the cellular 1,2-diacyl-sn-glycerol levels that acco mpany differentiation. (C) 1999 Academic Press.