Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
J Virol. 2013 Aug;87(15):8408-18. doi: 10.1128/JVI.00769-13. Epub 2013 May 22.
Previous studies have demonstrated that the murine coronavirus mouse hepatitis virus (MHV) nonstructural protein 2 (ns2) is a 2',5'-phosphodiesterase that inhibits activation of the interferon-induced oligoadenylate synthetase (OAS)-RNase L pathway. Enzymatically active ns2 is required for efficient MHV replication in macrophages, as well as for the induction of hepatitis in C57BL/6 mice. In contrast, following intranasal or intracranial inoculation, efficient replication of MHV in the brain is not dependent on an enzymatically active ns2. The replication of wild-type MHV strain A59 (A59) and a mutant with an inactive phosphodiesterase (ns2-H126R) was assessed in primary hepatocytes and primary central nervous system (CNS) cell types-neurons, astrocytes, and oligodendrocytes. A59 and ns2-H126R replicated with similar kinetics in all cell types tested, except macrophages and microglia. RNase L activity, as assessed by rRNA cleavage, was induced by ns2-H126R, but not by A59, and only in macrophages and microglia. Activation of RNase L correlated with the induction of type I interferon and the consequent high levels of OAS mRNA induced in these cell types. Pretreatment of nonmyeloid cells with interferon restricted A59 and ns2-H126R to the same extent and failed to activate RNase L following infection, despite induction of OAS expression. However, rRNA degradation was induced by treatment of astrocytes or oligodendrocytes with poly(I·C). Thus, RNase L activation during MHV infection is cell type specific and correlates with relatively high levels of expression of OAS genes, which are necessary but not sufficient for induction of an effective RNase L antiviral response.
先前的研究表明，鼠冠状病毒鼠肝炎病毒（MHV）非结构蛋白 2（ns2）是一种 2'，5'-磷酸二酯酶，可抑制干扰素诱导的寡聚腺苷酸合成酶（OAS）-RNase L 途径的激活。具有酶活性的 ns2 是 MHV 在巨噬细胞中有效复制所必需的，也是在 C57BL/6 小鼠中诱导肝炎所必需的。相比之下，在鼻内或颅内接种后，MHV 在大脑中的有效复制并不依赖于具有酶活性的 ns2。野生型 MHV 株 A59（A59）和具有无磷酸二酯酶活性的突变体（ns2-H126R）的复制在原代肝细胞和原代中枢神经系统（CNS）细胞类型-神经元、星形胶质细胞和少突胶质细胞中进行了评估。除了巨噬细胞和小胶质细胞外，A59 和 ns2-H126R 在所有测试的细胞类型中以相似的动力学复制。ns2-H126R 诱导了 RNase L 活性，如 rRNA 切割所评估的那样，但 A59 没有诱导，并且仅在巨噬细胞和小胶质细胞中诱导。RNase L 的激活与 I 型干扰素的诱导以及这些细胞类型中诱导的 OAS mRNA 的高水平相关。非髓样细胞用干扰素预处理限制了 A59 和 ns2-H126R 的复制程度相同，并且在感染后未能激活 RNase L，尽管诱导了 OAS 表达。然而，用 poly（I·C）处理星形胶质细胞或少突胶质细胞可诱导 rRNA 降解。因此，MHV 感染期间 RNase L 的激活是细胞类型特异性的，并与 OAS 基因的相对高水平表达相关，这是诱导有效的 RNase L 抗病毒反应所必需的，但不是充分的。
