Immunocytochemical evidence for phorbol ester-induced directional translocations of protein kinase C in HL60, K562, CHO, and E7SKS cells: possible role in differentiation.

The effects of phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) on the directions of protein kinase C (PKC) translocation in two leukemic cell lines (HL60 and K562) and two fibroblastic cell lines (CHO and E7SKS), related to their susceptibility to the differentiating effect of TPA, were examined. Immunocytochemical evidence indicated that TPA induced a redistribution (outward) of PKC to the plasma membrane in TPA-sensitive HL60 cells, whereas it caused a translocation (inward) of the enzyme to the nucleus or the perinuclear region in K562, CHO, and E7SKS cells, which are resistant to TPA in terms of cell growth and differentiation. Immunoblot analysis of the nuclear proteins from K562 cells revealed that TPA induced an increase in the amount of immunoreactive proteins. TPA, however, did not increase the amount of these immunoreactive species in nuclei isolated from CHO and E7SKS cells, indicating that the translocated PKC was associated only with perinuclear structures of the TPA-treated cells. It is suggested that directional redistribution of PKC to the plasma membrane, as opposed to the nuclear and perinuclear region, might represent an early event required for the TPA-induced differentiation and maturation of HL60 cells.