Differential regulation of protein kinase C isoenzymes during sphinganine potentiation of retinoic acid-induced granulocytic differentiation in human leukemia HL-60 cells

Differential changes in the expression of PKC isoenzymes in the RA-induced differentiation were noted. As measured by Western blot analysis, our results indicated the expressions of PKC-α, and -β isoenzymes decreased in the cell membrane but increased in the cytosol during the RA-induced granulocytic differentiation. The amounts of PKC-γ, on the other hand, decreased in the cell membrane while there was no significant changes in the cytosol. Similarly, the expression of PKC-δ was not altered in the cytosol, but was slightly reduced during the SP enhancement of RA-induced differentiation. In contrast, there were virtually little changes in the expression of PKC-ε and -ζ in the cell membrane or in the cytosol during the RA-induced differentiation in the absence of presence of SP. Concomitant with the decreased total PKC activity, there was a decline in the generation of sn-1,2-diacylglycerol (DAG) during the RA-induced differentiation. SP, enhancing the RA-induced differentiation, also potentiated the decrease of DAG content.