Coffey Caroline M, Sheh Alexander, Kim Irene S, Chandran Kartik, Nibert Max L, Parker John S L
Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
J Virol. 2006 Sep;80(17):8422-38. doi: 10.1128/JVI.02601-05.
The mechanisms by which reoviruses induce apoptosis have not been fully elucidated. Earlier studies identified the mammalian reovirus S1 and M2 genes as determinants of apoptosis induction. However, no published results have demonstrated the capacities of the proteins encoded by these genes to induce apoptosis, either independently or in combination, in the absence of reovirus infection. Here we report that the mammalian reovirus micro1 protein, encoded by the M2 gene, was sufficient to induce apoptosis in transfected cells. We also found that micro1 localized to lipid droplets, endoplasmic reticulum, and mitochondria in both transfected cells and infected cells. Two small regions encompassing amphipathic alpha-helices within a carboxyl-terminal portion of micro1 were necessary for efficient induction of apoptosis and association with lipid droplets, endoplasmic reticulum, and mitochondria in transfected cells. Induction of apoptosis by micro1 and its association with lipid droplets and intracellular membranes in transfected cells were abrogated when micro1 was coexpressed with sigma3, with which it is known to coassemble. We propose that micro1 plays a direct role in the induction of apoptosis in infected cells and that this property may relate to the capacity of micro1 to associate with intracellular membranes. Moreover, during reovirus infection, association with sigma3 may regulate apoptosis induction by micro1.
呼肠孤病毒诱导细胞凋亡的机制尚未完全阐明。早期研究确定哺乳动物呼肠孤病毒的S1和M2基因是诱导细胞凋亡的决定因素。然而，尚无已发表的结果表明在没有呼肠孤病毒感染的情况下，这些基因所编码的蛋白质单独或联合诱导细胞凋亡的能力。在此我们报告，由M2基因编码的哺乳动物呼肠孤病毒micro1蛋白足以在转染细胞中诱导细胞凋亡。我们还发现，在转染细胞和感染细胞中，micro1定位于脂滴、内质网和线粒体。在micro1羧基末端部分内包含两亲性α螺旋的两个小区域，对于在转染细胞中有效诱导细胞凋亡以及与脂滴、内质网和线粒体结合是必需的。当micro1与已知与其共同组装的sigma3共表达时，micro1在转染细胞中诱导细胞凋亡及其与脂滴和细胞内膜的结合被消除。我们提出，micro1在感染细胞的凋亡诱导中起直接作用，并且这种特性可能与micro1与细胞内膜结合的能力有关。此外，在呼肠孤病毒感染期间，与sigma3的结合可能调节micro1诱导的细胞凋亡。
