Han J, Wallen H D, Nuñez G, White E
Center for Advanced Biotechnology and Medicine, Rutgers University, Piscataway, New Jersey 08854, USA.
Mol Cell Biol. 1998 Oct;18(10):6052-62. doi: 10.1128/MCB.18.10.6052.
Genetic studies of the nematode Caenorhabditis elegans (C. elegans) have identified several important components of the cell death pathway, most notably CED-3, CED-4, and CED-9. CED-4 directly interacts with the Bcl-2 homologue CED-9 (or the mammalian Bcl-2 family member Bcl-xL) and the caspase CED-3 (or the mammalian caspases ICE and FLICE). This trimolecular complex of CED-4, CED-3, and CED-9 is functional in that CED-9 inhibits CED-4 from activating CED-3 and thereby inhibits apoptosis in heterologous systems. The E1B 19,000-molecular weight protein (E1B 19K) is a potent apoptosis inhibitor and the adenovirus homologue of Bcl-2-related apoptosis inhibitors. Since E1B 19K and Bcl-xL have functional similarity, we determined if E1B 19K interacts with CED-4 and regulates CED-4-dependent caspase activation. Binding analysis indicated that E1B 19K interacts with CED-4 in a Saccharomyces cerevisiae two-hybrid assay, in vitro, and in mammalian cell lysates. The subcellular localization pattern of CED-4 was dramatically changed by E1B 19K, supporting the theory of a functional interaction between CED-4 and E1B 19K. Whereas expression of CED-4 alone could not induce cell death, coexpression of CED-4 and FLICE augmented cell death induction by FLICE, which was blocked by expression of E1B 19K. Even though E1B 19K did not prevent FLICE-induced apoptosis, it did inhibit CED-4-dependent, FLICE-mediated apoptosis, which suggested that CED-4 was required for E1B 19K to block FLICE activation. Thus, E1B 19K functions through interacting with CED-4, and presumably a mammalian homologue of CED-4, to inhibit caspase activation and apoptosis.
对线虫秀丽隐杆线虫（C. elegans）的遗传学研究已经确定了细胞死亡途径的几个重要组成部分，最显著的是CED - 3、CED - 4和CED - 9。CED - 4直接与Bcl - 2同源物CED - 9（或哺乳动物Bcl - 2家族成员Bcl - xL）以及半胱天冬酶CED - 3（或哺乳动物半胱天冬酶ICE和FLICE）相互作用。CED - 4、CED - 3和CED - 9的这种三分子复合物具有功能，因为CED - 9抑制CED - 4激活CED - 3，从而在异源系统中抑制细胞凋亡。E1B 19,000分子量蛋白（E1B 19K）是一种有效的细胞凋亡抑制剂，也是Bcl - 2相关细胞凋亡抑制剂的腺病毒同源物。由于E1B 19K和Bcl - xL具有功能相似性，我们确定E1B 19K是否与CED - 4相互作用并调节依赖于CED - 4的半胱天冬酶激活。结合分析表明，E1B 19K在酿酒酵母双杂交试验、体外和哺乳动物细胞裂解物中与CED - 4相互作用。E1B 19K显著改变了CED - 4的亚细胞定位模式，支持了CED - 4与E1B 19K之间存在功能相互作用的理论。虽然单独表达CED - 4不能诱导细胞死亡，但CED - 4和FLICE的共表达增强了FLICE诱导的细胞死亡，而E1B 19K的表达则阻断了这种增强。尽管E1B 19K不能阻止FLICE诱导的细胞凋亡，但它确实抑制了依赖于CED - 4的、FLICE介导的细胞凋亡，这表明CED - 4是E1B 19K阻断FLICE激活所必需的。因此，E1B 19K通过与CED - 4以及可能的CED - 4哺乳动物同源物相互作用来抑制半胱天冬酶激活和细胞凋亡。
