Overexpression of protein kinase C isoform ε but not δ in human interleukin-3-dependent cells suppresses apoptosis and induces bcl-2 expression

Abstract

Hematopoietic progenitor cells die by apoptosis after removal of the appropriate colony-stimulating factor (CSF). Recent pharmacologic data have implicated protein kinase C (PKC) in the suppression of apoptosis in interleukin-3 (IL-3) and granulocyte-macrophage (GM)-CSF-dependent human myeloid cells. Because IL-3 and GM-CSF induce increases in diacylglycerol without mobilizing intracellular Ca++, it seemed that one of the novel Ca++ independent isoforms of PKC was involved. We report here that overexpression of PKCε in factor-dependent human TF-1 cells extends cell survival in the absence of cytokine. Overexpression of PKCδ does not have this effect. By 72 to 96 hours after cytokine withdrawal, the PCKε transfectants remain distributed in all phases of the cell cycle, as shown by fluorescence-activated cell sorting (FACS) analysis, while little intact cellular DNA is detectable in vector of PKCδ transfectants. PKCε induces bcl-2 protein expression fivefold to sixfold over the levels in empty vector transfectants, whereas the levels in PKCδ transfectants are similar to those in vector controls.