Cellular FLICE-inhibitory protein splice variants inhibit different steps of caspase-8 activation at the CD95 death-inducing signaling complex
Cellular FLICE-inhibitory protein splice variants inhibit different steps of caspase-8 activation at the CD95 death-inducing signaling complex
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DOI：
10.1074/jbc.m101780200
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发表时间：
2001-06-08
影响因子：
4.8
通讯作者：
Kirchhoff, S
中科院分区：
文献类型：
--
作者：
Krueger, A;Schmitz, I;Kirchhoff, S
在刺激后，CD 95（APO-1/Fas）将衔接分子FADD/MORT 1、半胱氨酸天冬氨酸蛋白酶原-8和细胞FLICE抑制蛋白（c-FLIP）募集到死亡诱导信号复合物（DISC）中。根据诱导邻近模型，半胱氨酸天冬氨酸蛋白酶原-8在DISC中通过两个后续切割步骤以自蛋白水解的方式被激活。c-FLIP蛋白以长（c-FLIPL）和短（c-FLIP）剪接变体的形式存在，它们都能够保护细胞免于死亡受体介导的凋亡。在稳定转染的BJAB细胞中，c-FLIPL和c-FLIPS均阻断DISC处的半胱天冬酶原-8活化。然而，切割在不同步骤被阻断。c-FLIPL允许半胱天冬酶原-8的第一个切割步骤，导致p10亚基的产生。有趣的是，缺乏p12亚基的p43-c-FLIPL也阻止了半胱天冬酶原-8的切割。相反，c-FLIPL的不可加工突变体允许半胱天冬酶原-8的第一次切割。总之，两种c-FLIP蛋白在DISC的半胱天冬酶原-8加工的不同水平下阻止半胱天冬酶-8活化。我们的研究结果表明，c-FLIPL诱导的半胱氨酸蛋白酶原-8的构象，允许部分但不完全的蛋白水解加工，而相反，c-FLIPS甚至阻止部分半胱氨酸蛋白酶原-8活化的DISC。
Upon stimulation, CD95 (APO-1/Fas) recruits the adapter molecule FADD/MORT1, procaspase-8, and the cellular FLICE-inhibitory proteins (c-FLIP) into the death-inducing signaling complex (DISC), According to the induced proximity model, procaspase-8 is activated in the DISC in an autoproteolytic manner by two subsequent cleavage steps. c-FLIP proteins exist as a long (c-FLIPL) and a short (c-FLIP,) splice variant, both of them capable of protecting cells from death receptor-mediated apoptosis. In stably transfected BJAB cells, both c-FLIPL and c-FLIPS block procaspase-8 activation at the DISC. However, cleavage is blocked at different steps. c-FLIPL allows the first cleavage step of procaspase-8, leading to the generation of the p10 subunit. In contrast, c-FLIPS completely inhibits cleavage of procaspase-8, Interestingly, p43-c-FLIPL lacking the p12 subunit also prevents cleavage of procaspase-8, In contrast, a nonprocessable mutant of c-FLIPL allows the first cleavage of procaspase-8, In conclusion, both c-FLIP proteins prevent caspase-8 activation at different levels of procaspase-8 processing at the DISC. Our results indicate that c-FLIPL induces a conformation of procaspase-8 that allows partial but not complete proteolytical processing, whereas in contrast c-FLIPS even prevents partial procaspase-8 activation at the DISC.