Caspase-mediated p65 cleavage promotes TRAIL-induced apoptosis.
Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is cytotoxic to a wide variety of transformed cells, but not to most normal cells, implying potential therapeutic value against advanced cancer. However, signal transduction in TRAIL-mediated apoptosis is not clearly understood compared with other TNF family members. Specifically, it is not yet understood how TRAIL controls nuclear factor kappaB (NF-kappaB) activation and overcomes its anti-apoptotic effect. We explored the regulation of NF-kappaB activity by TRAIL and its role in apoptosis. TRAIL combined with IkappaBalpha-"superrepressor" induced potent apoptosis of SK-Hep1 hepatoma cells at low concentrations of TRAIL that do not independently induce apoptosis. Apoptosis by high concentrations of TRAIL was not affected by IkappaBalpha-superrepressor. Although TRAIL alone did not induce NF-kappaB activity, TRAIL combined with z-VAD significantly increased NF-kappaB activation. Analysis of the NF-kappaB activation pathway indicated that TRAIL unexpectedly induced cleavage of p65 at Asp97, which was blocked by z-VAD, accounting for all of these findings. p65 expression abrogated apoptosis and increased NF-kappaB activity in TRAIL-treated cells. Cleavage-resistant p65D97A further increased NF-kappaB activity in TRAIL-treated cells, whereas the COOH-terminal p65 fragment acted as a dominant-negative inhibitor. XIAP levels were increased by TRAIL in combination with z-VAD, whereas XIAP levels were decreased by TRAIL alone. Cleavage of p65 was also detected after FRO thyroid cancer cells were treated with TRAIL. These results suggest that TRAIL induces NF-kappaB activation, but simultaneously abrogates NF-kappaB activation by cleaving p65, and thereby inhibits the induction of anti-apoptotic proteins such as XIAP, which contributes to the strong apoptotic activity of TRAIL compared with other TNF family members.
Kim
Hun Sik
HS
Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Kangnam-ku, Seoul, Korea.
Chang
Inik
I
Kim
Ja Young
JY
Choi
Kyung-Hee
KH
Lee
Myung-Shik
MS
D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D051017:Apoptosis Regulatory Proteins; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism*; D045744:Cell Line, Tumor; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D008562:Membrane Glycoproteins / Q000494:pharmacology*; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism; D053221:TNF-Related Apoptosis-Inducing Ligand; D051996:Transcription Factor RelA; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D051636:X-Linked Inhibitor of Apoptosis Protein
D051017:Apoptosis Regulatory Proteins; D008562:Membrane Glycoproteins; D016328:NF-kappa B; D011506:Proteins; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D051996:Transcription Factor RelA; D014409:Tumor Necrosis Factor-alpha; D051636:X-Linked Inhibitor of Apoptosis Protein; C496866:XIAP protein, human; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases