title: Evidence that protein kinase Cepsilon mediates phorbol ester inhibition of calphostin C- and tumor necrosis factor-alpha-induced apoptosis in U937 histiocytic lymphoma cells.
abstract: Protein kinase C (PKC) activators, such as the tumor-promoting phorbol esters, have been reported to protect several cell lines from apoptosis induced by a variety of agents. Recent evidence suggests that PKCepsilon is involved in protection of cardiac myocytes from hypoxia-induced cell death (Gray, M. O., Karliner, J. S., and Mochly-Rosen, D. (1997) J. Biol. Chem. 272, 30945-30951). We investigated the protective effects of the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) on U937 histiocytic lymphoma cells induced to undergo apoptosis by tumor necrosis factor-alpha (TNF-alpha) or by the specific PKC inhibitor calphostin C. U937 cells were transiently permeabilized with a peptide (epsilonV1-2) derived from the V1 region of PKCepsilon that has been reported to specifically block translocation of PKCepsilon. The epsilonV1-2 peptide blocked the inhibitory effect of TPA on both TNF-alpha- and calphostin C-induced apoptosis. A scrambled version of epsilonV1-2 and a peptide reported to inhibit PKCbeta translocation (betaC2-4) had no effect on the ability of TPA to inhibit apoptosis. These results suggest that PKCepsilon is required for the protective effect of TPA in TNF-alpha- and calphostin C-induced apoptosis. Furthermore, calphostin C reduced membrane-associated PKCepsilon activity and immunoreactivity, suggesting that PKCepsilon may play an important role in leukemic cell survival.
authors.affiliation: School of Biological Sciences, Faculty of Science and Engineering, Flinders University of South Australia, Adelaide, South Australia 5001, Australia. bigcm@flinder.edu.au
authors.forename: G C
authors.initials: GC
authors.lastname: Mayne
authors.forename: A W
authors.initials: AW
authors.lastname: Murray
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D002843:Chromatin / Q000187:drug effects / Q000502:physiology; D053938:DNA Fragmentation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D016403:Lymphoma, Large B-Cell, Diffuse; D009281:Naphthalenes / Q000494:pharmacology*; D009707:Nucleosomes / Q000187:drug effects / Q000502:physiology; D010446:Peptide Fragments / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D051744:Protein Kinase C-epsilon; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology* / Q000502:physiology
chemical_list: D002843:Chromatin; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D009281:Naphthalenes; D009707:Nucleosomes; D010446:Peptide Fragments; D014409:Tumor Necrosis Factor-alpha; C497255:PRKCE protein, human; D011493:Protein Kinase C; D051744:Protein Kinase C-epsilon; C058819:calphostin C; D013755:Tetradecanoylphorbol Acetate