Thress K, Henzel W, Shillinglaw W, Kornbluth S
Department of Pharmacology and Cancer Biology, Duke University Medical Center, C366 LSRC, Research Drive, Durham, NC 27710, USA.
EMBO J. 1998 Nov 2;17(21):6135-43. doi: 10.1093/emboj/17.21.6135.
Reaper is a central regulator of apoptosis in Drosophila melanogaster. With no obvious catalytic activity or homology to other known apoptotic regulators, reaper's mechanism of action has been obscure. We recently reported that recombinant Drosophila reaper protein induced rapid mitochondrial cytochrome c release, caspase activation and apoptotic nuclear fragmentation in extracts of Xenopus eggs. We now report the purification of a 150 kDa reaper-interacting protein from Xenopus egg extracts, which we have named Scythe. Scythe is highly conserved among vertebrates and contains a ubiquitin-like domain near its N-terminus. Immunodepletion of Scythe from extracts completely prevented reaper-induced apoptosis without affecting apoptosis triggered by activated caspases. Moreover, a truncated variant of Scythe lacking the N-terminal domain induced apoptosis even in the absence of reaper. These data suggest that Scythe is a novel apoptotic regulator that is an essential component in the pathway of reaper-induced apoptosis.
收割者蛋白是黑腹果蝇凋亡过程中的核心调节因子。由于它没有明显的催化活性，也与其他已知的凋亡调节因子没有同源性，其作用机制一直不明。我们最近报道，重组果蝇收割者蛋白可在非洲爪蟾卵提取物中诱导线粒体细胞色素c快速释放、半胱天冬酶激活及凋亡性核碎裂。我们现在报告从非洲爪蟾卵提取物中纯化出一种150 kDa的与收割者蛋白相互作用的蛋白，我们将其命名为大镰刀蛋白。大镰刀蛋白在脊椎动物中高度保守，在其N端附近含有一个类泛素结构域。从提取物中免疫去除大镰刀蛋白可完全阻止收割者蛋白诱导的凋亡，而不影响活化的半胱天冬酶引发的凋亡。此外，一种缺失N端结构域的大镰刀蛋白截短变体即使在没有收割者蛋白的情况下也能诱导凋亡。这些数据表明，大镰刀蛋白是一种新型凋亡调节因子，是收割者蛋白诱导凋亡途径中的一个重要组成部分。
