PKC isoform expression in MKs.

(A) The expression of conventional and novel isoforms of PKC in MKs was tested by Western blot analysis. MKs were purified from cultures by unit gravity sedimentation and lysed. Fifty micrograms of protein was loaded per lane. The positive controls for PKCα and β were UT7 cells and those for PKCγ, δ, and ε were BaF3 cells. (B) PKC isoform downmodulation by PMA in megakaryocytes. Purified MKs were cultured in TPO alone, TPO and plasma, or TPO and plasma and 100 ng/mL PMA for 48 hours. Cells were then lysed and examined for PKC isoform expression by Western blot analysis. Chronic PMA stimulation markedly down-modulated PKCα, but not PKCγ expression.