ENHANCED EXPRESSION OF THE BETA-II SUBSPECIES OF PROTEIN-KINASE-C IN DIFFERENTIATING ERYTHROLEUKEMIA-CELLS

Polyclonal antipeptide antibodies which recognize selected isozymes (α, β I, β II, and γ) of the protein kinase C family were used to identify specific subspecies in undifferentiated Friend erythroleukemia cells and in cells triggered to differentiate with hexamethylene bisacetamide. The β II isozyme of protein kinase C was the primary isozyme expressed and its abundance was significantly increased (P < 0.05) in differentiated cells. Differences in immunostaining between control and experimental groups were objectively quantitated by determining percentage transmission of light through cells based on color threshold rather than gray intensity levels. Staining was localized to the cytoplasm predominantly in differentiated cells, whereas nuclei stained more intensely in undifferentiated cells. These results provide immunocytochemical evidence to support the hypothesis that changes in the expression of the β II subspecies of protein kinase C are essential to the programmed maturation of differentiating Friend erythroleukemia cells. © 1990.