Seshagiri S, Chang W T, Miller L K
Department of Entomology, The University of Georgia, Athens 30602, USA.
FEBS Lett. 1998 May 22;428(1-2):71-4. doi: 10.1016/s0014-5793(98)00493-1.
Much of our knowledge concerning the genetics that regulate cell death has come from the studies of cell death during the development of the nematode Caenorhabditis elegans. Of the 14 genes identified as components of nematode cell death pathways, two genes, ced-3 and ced-4, are required to promote cell death and a third, ced-9, blocks cell death. Recent studies show CED-4 to be an activator of CED-3 and CED-9 to be an inhibitor of CED-4. Two published sequence alignments suggest that CED-4 contains a death effector domain (DED), a protein sequence motif present in other death signaling proteins like Fadd and Flice; one study suggests a DED sequence similarity near the N-terminus while the other found sequence similarity near the C-terminus of CED-4. Using mutational analysis we have tested the functional significance of the conserved residues found within the putative DEDs of CED-4. Mutations in two conserved residues within the putative N-terminal DED of CED-4 affected its function, while mutations in the conserved residues within the putative C-terminal DED had no effect on CED-4 function. Our results do not support the presence of a DED in the C-terminus of CED-4 and suggest a potential role for the N-terminus in CED-4 function, possibly as a DED or as a CARD (caspase recruitment domain). We also found that CED-9 associated with all the CED-4 mutants and inhibited the activity of all the active-CED-4 mutants.
我们关于调控细胞死亡的遗传学知识，很大一部分来自对线虫秀丽隐杆线虫发育过程中细胞死亡的研究。在被鉴定为线虫细胞死亡途径组成部分的14个基因中，有两个基因ced - 3和ced - 4是促进细胞死亡所必需的，第三个基因ced - 9则阻止细胞死亡。最近的研究表明，CED - 4是CED - 3的激活剂，CED - 9是CED - 4的抑制剂。两项已发表的序列比对表明，CED - 4含有一个死亡效应结构域（DED），这是一种存在于其他死亡信号蛋白（如Fadd和Flice）中的蛋白质序列基序；一项研究表明在CED - 4的N端附近有DED序列相似性，而另一项研究则在CED - 4的C端附近发现了序列相似性。我们通过突变分析测试了CED - 4假定的DED中保守残基的功能意义。CED - 4假定的N端DED内两个保守残基的突变影响了其功能，而假定的C端DED内保守残基的突变对CED - 4功能没有影响。我们的结果不支持CED - 4的C端存在DED，并表明N端在CED - 4功能中可能发挥潜在作用，可能作为一个DED或作为一个CARD（半胱天冬酶募集结构域）。我们还发现CED - 9与所有CED - 4突变体相关，并抑制了所有活性CED - 4突变体的活性。
