School of Medicine, Department of Microbiology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA.
School of Medicine, Division of Infectious Disease, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA.
J Virol. 2014 Aug;88(16):9458-71. doi: 10.1128/JVI.01323-14. Epub 2014 Jun 11.
Since its introduction in New York City, NY, in 1999, West Nile virus (WNV) has spread to all 48 contiguous states of the United States and is now the leading cause of epidemic encephalitis in North America. As a member of the family Flaviviridae, WNV is part of a group of clinically important human pathogens, including dengue virus and Japanese encephalitis virus. The members of this family of positive-sense, single-stranded RNA viruses have limited coding capacity and are therefore obligated to co-opt a significant amount of cellular factors to translate their genomes effectively. Our previous work has shown that WNV growth was independent of macroautophagy activation, but the role of the evolutionarily conserved mammalian target of rapamycin (mTOR) pathway during WNV infection was not well understood. mTOR is a serine/threonine kinase that acts as a central cellular censor of nutrient status and exercises control of vital anabolic and catabolic cellular responses such as protein synthesis and autophagy, respectively. We now show that WNV activates mTOR and cognate downstream activators of cap-dependent protein synthesis at early time points postinfection and that pharmacologic inhibition of mTOR (KU0063794) significantly reduced WNV growth. We used an inducible Raptor and Rictor knockout mouse embryonic fibroblast (MEF) system to further define the role of mTOR complexes 1 and 2 in WNV growth and viral protein synthesis. Following inducible genetic knockout of the major mTOR cofactors raptor (TOR complex 1 [TORC1]) and rictor (TORC2), we now show that TORC1 supports flavivirus protein synthesis via cap-dependent protein synthesis pathways and supports subsequent WNV growth.
Since its introduction in New York City, NY, in 1999, West Nile virus (WNV) has spread to all 48 contiguous states in the United States and is now the leading cause of epidemic encephalitis in North America. Currently, the mechanism by which flaviviruses such as WNV translate their genomes in host cells is incompletely understood. Elucidation of the host mechanisms required to support WNV genome translation will provide broad understanding for the basic mechanisms required to translate capped viral RNAs. We now show that WNV activates mTOR and cognate downstream activators of cap-dependent protein synthesis at early time points postinfection. Following inducible genetic knockout of the major mTOR complex cofactors raptor (TORC1) and rictor (TORC2), we now show that TORC1 supports WNV growth and protein synthesis. This study demonstrates the requirement for TORC1 function in support of WNV RNA translation and provides insight into the mechanisms underlying flaviviral RNA translation in mammalian cells.
自 1999 年在美国纽约市首次出现以来，西尼罗河病毒（WNV）已传播至美国所有 48 个相邻州，目前已成为北美流行脑炎的主要病因。目前，人们对黄病毒（如 WNV）在宿主细胞中翻译基因组的机制还不完全了解。阐明支持 WNV 基因组翻译所需的宿主机制将为翻译 capped 病毒 RNA 所需的基本机制提供广泛的认识。我们现在表明，WNV 在感染后早期激活 mTOR 和帽依赖性蛋白合成的同源下游激活物。在诱导型遗传敲除主要 mTOR 复合物共因子 raptor（TORC1）和 rictor（TORC2）之后，我们现在表明 TORC1 支持 WNV 的生长和蛋白合成。这项研究证明了 TORC1 支持 WNV RNA 翻译的功能要求，并深入了解了哺乳动物细胞中黄病毒 RNA 翻译的机制。
