Kawahara A, Enari M, Talanian R V, Wong W W, Nagata S
Department of Genetics, Osaka University Medical School, Suita, Japan.
Genes Cells. 1998 May;3(5):297-306. doi: 10.1046/j.1365-2443.1998.00189.x.
Fas is a member of the tumour necrosis factor (TNF) receptor family. Activation of Fas by its ligand or an agonistic anti-Fas antibody causes apoptosis in Fas-bearing cells, by activating various members of the caspase family.
Specific fluorogenic substrates (MCA-DEVDAPK[dnp] and MCA-VEVDAPK[dnp]) for caspases 3 and 6 were prepared. Using these substrates, a gradual increase of the caspase 3-and 6-like proteases were detected during the Fas engagement in human Jurkat. This activation of caspases correlated well with the cleavage of poly(ADP-ribose) polymerase and lamin B1, as well as with DNA fragmentation. When the recombinant caspases were added to the extracts from Jurkat cells, caspase 3 produced active caspase 6-like protease, while caspase 6 activated the caspase 3 protease, suggesting that these proteases can activate each other. The caspase-treated cell extracts, as well as the extracts from the Fas-activated cells, caused the proteolysis of nuclear proteins and DNA degradation. The cleavage of nuclear proteins was inhibited by caspase inhibitors, while the same inhibitors had no effect on DNA degradation.
At one stage of the caspase cascade, caspases activate each other, and amplify the apoptotic signal. Caspases downstream of the cascade then cause the proteolysis of nuclear proteins and DNA degradation.
Fas是肿瘤坏死因子（TNF）受体家族的成员。Fas被其配体或抗Fas激动性抗体激活后，通过激活半胱天冬酶家族的各个成员，导致表达Fas的细胞发生凋亡。
制备了半胱天冬酶3和6的特异性荧光底物（MCA-DEVDAPK[dnp]和MCA-VEVDAPK[dnp]）。使用这些底物，在人Jurkat细胞中Fas激活过程中检测到半胱天冬酶3和6样蛋白酶逐渐增加。这种半胱天冬酶的激活与聚（ADP-核糖）聚合酶和核纤层蛋白B1的裂解以及DNA片段化密切相关。当将重组半胱天冬酶添加到Jurkat细胞提取物中时，半胱天冬酶3产生活性半胱天冬酶6样蛋白酶，而半胱天冬酶6激活半胱天冬酶3蛋白酶，表明这些蛋白酶可以相互激活。经半胱天冬酶处理的细胞提取物以及Fas激活细胞的提取物导致核蛋白的蛋白水解和DNA降解。核蛋白的裂解被半胱天冬酶抑制剂抑制，而相同的抑制剂对DNA降解没有影响。
在半胱天冬酶级联反应的一个阶段，半胱天冬酶相互激活，并放大凋亡信号。级联反应下游的半胱天冬酶随后导致核蛋白的蛋白水解和DNA降解。
