Hom L G, Volkman L E
Department of Molecular and Cell Biology, University of California, Berkeley, California, 94720, USA.
Virology. 2000 Nov 10;277(1):178-83. doi: 10.1006/viro.2000.0586.
Infection of permissive insect hosts by the baculovirus Autographa californica M nucleopolyhedrovirus results in liquefaction, a pathogenic effect that enhances the dispersal of progeny virions. Two viral gene products-a protease, V-CATH, and a chitinase, chiA-have been shown to be required for liquefaction to occur. It has been generally accepted that the primary functions of these proteins is to degrade the proteinaceous and chitinous components of the host cadaver, respectively. We have generated suggestive evidence, however, that chiA may also serve as a molecular chaperone for proV-CATH, the precursor of V-CATH. When cells were infected with virus lacking a functional chiA gene, proV-CATH failed to undergo processing in vivo and in vitro and formed insoluble aggregates in the endoplasmic reticulum of infected cells. Thus, expression of chiA may be required for the proper folding of the nascent V-CATH polypeptide in the endoplasmic reticulum. Identical results were obtained when tunicamycin was used to block N-linked glycosylation in cells infected with wildtype virus, suggesting that the putative chiA/V-CATH interaction is mediated by N-linked oligosaccharides.
苜蓿银纹夜蛾多核衣壳核型多角体病毒（Autographa californica M nucleopolyhedrovirus）感染允许性昆虫宿主会导致液化，这是一种致病效应，可增强子代病毒粒子的扩散。两种病毒基因产物——一种蛋白酶V-CATH和一种几丁质酶chiA——已被证明是液化发生所必需的。人们普遍认为，这些蛋白质的主要功能分别是降解宿主尸体的蛋白质和几丁质成分。然而，我们已经产生了一些暗示性证据，表明chiA也可能作为V-CATH的前体proV-CATH的分子伴侣。当细胞被缺乏功能性chiA基因的病毒感染时，proV-CATH在体内和体外都无法进行加工，并在受感染细胞的内质网中形成不溶性聚集体。因此，内质网中新生V-CATH多肽的正确折叠可能需要chiA的表达。当用衣霉素阻断野生型病毒感染细胞中的N-连接糖基化时，也得到了相同的结果，这表明假定的chiA/V-CATH相互作用是由N-连接寡糖介导的。
