Regulation of prostate cancer cell survival by protein kinase Cepsilon involves bad phosphorylation and modulation of the TNFalpha/JNK pathway.
Protein kinase Cepsilon (PKCepsilon), a diacyglycerol- and phorbol ester-responsive serine-threonine kinase, has been implicated in mitogenic and survival control, and it is markedly overexpressed in human tumors, including in prostate cancer. Although prostate cancer cells undergo apoptosis in response to phorbol ester stimulation via PKCdelta-mediated release of death factors, the involvement of PKCepsilon in this response is not known. PKCepsilon depletion by RNAi or expression of a dominant negative kinase-dead PKCepsilon mutant potentiated the apoptotic response of PMA and sensitized LNCaP cells to the death receptor ligand TNFalpha. On the other hand, overexpression of PKCepsilon by adenoviral means protected LNCaP cells against apoptotic stimuli. Interestingly, PKCepsilon RNAi depletion significantly enhanced the release of TNFalpha in response to PMA and greatly potentiated JNK activation by this cytokine. Further mechanistic analysis revealed that PMA fails to promote phosphorylation of Bad in Ser(112) in PKCepsilon-depleted LNCaP cells, whereas PKCepsilon overexpression greatly enhanced Bad phosphorylation. This effect was independent of Akt, ERK, or p90Rsk, well established kinases for Ser(112) in Bad. Moreover, expression of a S112A-Bad mutant potentiated PMA-induced apoptosis. Finally, we found that upon activation PKCepsilon accumulated in mitochondrial fractions in LNCaP cells and that Bad was a substrate of PKCepsilon in vitro. Our results established that PKCepsilon modulates survival in prostate cancer cells via multiple pathways.
Meshki
John
J
Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6160, USA.
Caino
M Cecilia
MC
von Burstin
Vivian A
VA
Griner
Erin
E
Kazanietz
Marcelo G
MG
D017209:Apoptosis; D045744:Cell Line, Tumor; D002470:Cell Survival; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008297:Male; D010766:Phosphorylation; D011471:Prostatic Neoplasms / Q000378:metabolism* / Q000473:pathology*; D051744:Protein Kinase C-epsilon / Q000378:metabolism*; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*; D051025:bcl-Associated Death Protein
C494819:BAD protein, human; D014409:Tumor Necrosis Factor-alpha; D051025:bcl-Associated Death Protein; D051744:Protein Kinase C-epsilon; D048031:JNK Mitogen-Activated Protein Kinases; D013755:Tetradecanoylphorbol Acetate