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p53の転写活性化能に依存しないアポトーシスとFasを介さないcaspaseの活性化：高崇峰、土田信夫（東医歯大 歯 細菌）

Activation of caspases in p53-induced transactivation-independent apoptosis is not mediated by Fas pathway: Chongfeng GAO and Nobuo TSUCHIDA (Dept. of Mol. Cell. Oncol., Tokyo Med. & Dent. University )

p53-induced apoptosis plays an important role in tumor suppression. However, the mechanism(s) by which p53 induces apoptosis is still unclear. Previously we constructed a human temperature-sensitive (ts) p53 mutant (138Ala→Val) and established a Jurkat cell line (J138V5C) carrying the ts p53. Upon temperature shift-down from 37.5℃ to 32.5℃, J138V5C cells underwent apoptisis characterized by membrane blebbing, DNA fragmentation and loss of viability. Although several p53 transcrptional target genes were induced at 32.5℃, the apotosis was not blocked by the translation inhibitor (cyclohexiimde) indicating that the translation of p53 transcritional target genes was not essential for p53-indced apotptosis in this system. Western blot analysis showed that both PARP, CPP32 and ICH-1 precursors were cleaved during apoptosis. CPP32 preferred tetrapeptide inhibitior, Ac-DEVD-CHO blocked the cleavage of ICH-1 and PARP precursors, suggesting CPP32 or other DEVD-sensitive caspase(s) to be upstream activator of ICH-1. To explore the pathway leading to activation of caspases, we evaluated the role of Fas pathway by using Fas adn Fas ligand-neutralizing antibodies. The results showed that both antibodies failed to block p53-induced apoptosis. Taken together, our reslutls indicated that p53-idnuced transactivation-independent apoptosis in Jurkat cells involved sequential actiavation of CPP32 and DEVD-sensitive caspase(s) and ICH-1, which was not mediated by Fas pathway.