Diacylglycerol kinase alpha suppresses tumor necrosis factor-alpha-induced apoptosis of human melanoma cells through NF-kappaB activation.
We investigated the implication of diacylglycerol kinase (DGK) alpha (type I isoform) in melanoma cells because we found that this DGK isoform was expressed in several human melanoma cell lines but not in noncancerous melanocytes. Intriguingly, the overexpression of wild-type (WT) DGKalpha, but not of its kinase-dead (KD) mutant, markedly suppressed tumor necrosis factor (TNF)-alpha-induced apoptosis of AKI human melanoma cells. In the reverse experiment, siRNA-mediated knockdown of DGKalpha significantly enhanced the apoptosis. The overexpression of other type I isoforms (DGKbeta and DGKgamma) had, on the other hand, no detectable effects on the apoptosis. These results indicate that DGKalpha specifically suppresses the TNF-alpha-induced apoptosis through its catalytic action. We found that the overexpression of DGKalpha-WT, but not of DGKalpha-KD, further enhanced the TNF-alpha-stimulated transcriptional activity of an anti-apoptotic factor, NF-kappaB. Conversely, DGKalpha-knockdown considerably inhibited the NF-kappaB activity. Moreover, an NF-kappaB inhibitor blunted the anti-apoptotic effect of DGKalpha overexpression. Together, these results strongly suggest that DGKalpha is a novel positive regulator of NF-kappaB, which suppresses TNF-alpha-induced melanoma cell apoptosis.
Yanagisawa
Kenji
K
Department of Dermatology, Sapporo Medical University School of Medicine, Sapporo, Japan.
Yasuda
Satoshi
S
Kai
Masahiro
M
Imai
Shin-ichi
S
Yamada
Keiko
K
Yamashita
Toshiharu
T
Jimbow
Kowichi
K
Kanoh
Hideo
H
Sakane
Fumio
F
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D019852:Diacylglycerol Kinase / Q000378:metabolism*; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D008544:Melanocytes / Q000187:drug effects / Q000201:enzymology; D008545:Melanoma / Q000201:enzymology* / Q000473:pathology*; D016328:NF-kappa B / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects; D034741:RNA, Small Interfering / Q000378:metabolism; D051381:Rats; D013552:Swine; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D007527:Isoenzymes; D016328:NF-kappa B; D034741:RNA, Small Interfering; D014409:Tumor Necrosis Factor-alpha; D019852:Diacylglycerol Kinase