Medema J P, Toes R E, Scaffidi C, Zheng T S, Flavell R A, Melief C J, Peter M E, Offringa R, Krammer P H
Tumorimmunology Program, German Cancer Research Center, Heidelberg.
Eur J Immunol. 1997 Dec;27(12):3492-8. doi: 10.1002/eji.1830271250.
Cytotoxic T lymphocytes induce apoptosis in target cells through the CD95(APO-1/Fas) and the perforin/granzyme B (GrB) pathway. The exact substrate of GrB in vivo is still unknown, but to induce apoptosis GrB requires the activity of caspases in target cells. We show here that in HeLa target cells induction of apoptosis through the perforin/GrB pathway resulted in minor direct cleavage of CPP32 (caspase-3) by GrB. Most caspase-3 cleavage resulted from activation of an upstream caspase. Moreover, target cells derived from caspase-3(-/-) mice displayed GrB-induced poly(ADP-ribose) polymerase (PARP) cleavage with only partially reduced efficiency compared to wild-type target cells. This indicates that other PARP-cleaving caspases can be activated during perforin/GrB-induced cell death. In contrast to caspase-3, FLICE (caspase-8) was directly cleaved by GrB in HeLa cells. We therefore conclude that FLICE not only plays a central role in CD95(APO-1/Fas)-induced apoptosis but can also be directly activated during perforin/GrB-induced apoptosis.
细胞毒性T淋巴细胞通过CD95（APO-1/Fas）和穿孔素/颗粒酶B（GrB）途径诱导靶细胞凋亡。GrB在体内的确切作用底物尚不清楚，但GrB诱导凋亡需要靶细胞中半胱天冬酶的活性。我们在此表明，在HeLa靶细胞中，通过穿孔素/GrB途径诱导凋亡导致GrB对CPP32（半胱天冬酶-3）的直接切割作用较小。大多数半胱天冬酶-3的切割是由上游半胱天冬酶的激活引起的。此外，与野生型靶细胞相比，源自半胱天冬酶-3基因敲除小鼠的靶细胞在GrB诱导下显示出聚（ADP-核糖）聚合酶（PARP）的切割，但其效率仅部分降低。这表明在穿孔素/GrB诱导的细胞死亡过程中，其他能切割PARP的半胱天冬酶也可被激活。与半胱天冬酶-3不同，在HeLa细胞中，FLICE（半胱天冬酶-8）可被GrB直接切割。因此我们得出结论，FLICE不仅在CD95（APO-1/Fas）诱导的凋亡中起核心作用，在穿孔素/GrB诱导的凋亡过程中也可被直接激活。
