Neutral endopeptidase promotes phorbol ester-induced apoptosis in prostate cancer cells by inhibiting neuropeptide-induced protein kinase C delta degradation.
Phorbol esters induce apoptosis in androgen-sensitive LNCaP cells, which express neutral endopeptidase (NEP), but not in androgen-independent prostate cancer (PC) cells, which lack NEP expression. We investigated the role of NEP in PC cell susceptibility to 12-O-tetradecanoylphorbol-13-acetate (TPA). Western analysis showed that expression of NEP and protein kinase Cdelta (PKCdelta) correlated with PC cell sensitivity to TPA-induced growth arrest and apoptosis in LNCaP cells and in TSU-Prl cells expressing an inducible wild-type NEP protein. Inhibition of NEP enzyme activity using the specific NEP inhibitor CGS24592, or inhibition of PKCdelta using Rottlerin at concentrations that inhibit PKCdelta but not PKCalpha, significantly inhibited TPA-induced growth inhibition and cell death. Furthermore, pulse-chase experiments showed PKCdelta is stabilized in LNCaP cells and in TSU-Pr1 cells overexpressing wild-type NEP compared with PC cells lacking NEP expression. This results from NEP inactivation of its neuropeptide substrates (bombesin and endothelin-1), which in the absence of NEP stimulate cSrc kinase activity and induce rapid degradation of PKCdelta protein. These results indicate that expression of enzymatically active NEP by PC cells is necessary for TPA-induced apoptosis, and that NEP inhibits neuropeptide-induced, cSrc-mediated PKCdelta degradation.
Sumitomo
M
M
Department of Urology, Joan and Stanford I. Weill Medical College of Cornell University, New York, New York 10021, USA.
Shen
R
R
Goldberg
J S
JS
Dai
J
J
Navarro
D
D
Nanus
D M
DM
D000595:Amino Acid Sequence; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D001839:Bombesin / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D000081247:CSK Tyrosine-Protein Kinase; D002455:Cell Division / Q000187:drug effects; D015536:Down-Regulation / Q000187:drug effects; D019332:Endothelin-1 / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D006131:Growth Inhibitors / Q000494:pharmacology; D006801:Humans; D007527:Isoenzymes / Q000096:biosynthesis / Q000378:metabolism*; D008297:Male; D008969:Molecular Sequence Data; D015260:Neprilysin / Q000378:metabolism / Q000502:physiology*; D011471:Prostatic Neoplasms / Q000201:enzymology* / Q000473:pathology; D011493:Protein Kinase C / Q000096:biosynthesis / Q000378:metabolism*; D051745:Protein Kinase C-delta; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014407:Tumor Cells, Cultured / Q000187:drug effects; D019061:src-Family Kinases
D019332:Endothelin-1; D006131:Growth Inhibitors; D007527:Isoenzymes; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; D019061:src-Family Kinases; C000631346:CSK protein, human; C497258:PRKCD protein, human; D011493:Protein Kinase C; D051745:Protein Kinase C-delta; D015260:Neprilysin; D013755:Tetradecanoylphorbol Acetate; D001839:Bombesin