Hilterbrand Adam T, Boutz Daniel R, Marcotte Edward M, Upton Jason W
Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, LaMontagne Center for Infectious Disease, University of Texas at Austin, Austin, Texas, USA.
Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, Center for Systems and Synthetic Biology, University of Texas at Austin, Austin, Texas, USA.
mBio. 2017 Jan 17;8(1):e01864-16. doi: 10.1128/mBio.01864-16.
Maintaining control over inflammatory processes represents a paradox for viral pathogens. Although many viruses induce host inflammatory responses to facilitate infection, control is necessary to avoid overactivation. One way is through the manipulation of proinflammatory chemokine levels, both host and viral. Murine cytomegalovirus (MCMV), a model betaherpesvirus, encodes a viral C-C chemokine, MCK2, which promotes host inflammatory responses and incorporates into virions to facilitate viral dissemination. Here, we show that the activity of M48, the conserved MCMV deubiquitinating enzyme (DUB), regulates MCK2 levels during infection. Inactivation of M48 DUB activity results in viral attenuation and exacerbates virally induced, MCK2-dependent inflammatory responses. M48 DUB activity also influences MCK2 incorporation into virions. Importantly, attenuation of DUB-mutant virus acute replication in vitro and in vivo is largely ameliorated by targeted deletion of MCK2. Thus, uncontrolled MCK2 levels appear to mediate DUB-mutant virus attenuation in specific tissues or cell types. This demonstrates that MCMV M48 DUB activity plays a previously unappreciated role in controlling MCK2 levels, thereby managing MCK2-dependent processes. These findings reveal a novel intrinsic control mechanism of virally induced inflammation and support the identification of betaherpesvirus DUBs as possible new targets for antiviral therapies.
Human cytomegalovirus infections represent a tremendous burden not only to those afflicted but also to health care systems worldwide. As cytomegalovirus infections are a leading cause of nongenetic sensory loss and neurodevelopmental delay, it is imperative that valuable model systems exist in order that we might understand what viral factors contribute to replication and pathogenesis. Currently, the only approved drug treatments against CMV infection are nucleoside analogues, to which some strains have become resistant. Understanding unique viral enzymatic contributions to infections will allow the development of novel pharmacological therapies. Here, we show that M48, the conserved MCMV deubiquitinase, is critical for MCMV replication in mice and demonstrate that attenuation is due to deregulated production of a viral proinflammatory chemokine. The deubiquitinases of both human and murine CMV represent structurally unique DUBs and are therefore attractive targets for pharmacological intervention. Continued research into the substrates of these DUBs will lend additional insight into their potential as targets.
对炎症过程进行控制对病毒病原体而言是一个矛盾。尽管许多病毒会诱导宿主炎症反应以促进感染，但进行控制对于避免过度激活是必要的。一种方式是通过操纵宿主和病毒的促炎趋化因子水平。小鼠巨细胞病毒（MCMV），一种典型的β疱疹病毒，编码一种病毒C-C趋化因子MCK2，它可促进宿主炎症反应并整合到病毒粒子中以促进病毒传播。在此，我们表明，M48，即保守的MCMV去泛素化酶（DUB），在感染过程中调节MCK2水平。M48 DUB活性的失活导致病毒减毒，并加剧病毒诱导的、依赖MCK2的炎症反应。M48 DUB活性也影响MCK2整合到病毒粒子中。重要的是，通过靶向缺失MCK2，DUB突变病毒在体外和体内急性复制的减毒在很大程度上得到改善。因此，不受控制的MCK2水平似乎介导了DUB突变病毒在特定组织或细胞类型中的减毒。这表明MCMV M48 DUB活性在控制MCK2水平从而调控依赖MCK2的过程中发挥了先前未被认识到的作用。这些发现揭示了病毒诱导炎症的一种新的内在控制机制，并支持将β疱疹病毒DUBs鉴定为抗病毒治疗的可能新靶点。
人类巨细胞病毒感染不仅给患者带来巨大负担，也给全球医疗系统带来巨大负担。由于巨细胞病毒感染是非遗传性感觉丧失和神经发育延迟的主要原因，因此必须有有价值的模型系统，以便我们了解哪些病毒因素有助于复制和发病机制。目前，唯一被批准用于治疗CMV感染的药物是核苷类似物，一些毒株已对其产生耐药性。了解病毒独特的酶对感染的作用将有助于开发新的药物疗法。在此，我们表明，M48，即保守的MCMV去泛素酶，对MCMV在小鼠中的复制至关重要，并证明减毒是由于病毒促炎趋化因子的产生失控所致。人类和小鼠CMV的去泛素酶代表结构独特的DUBs，因此是药物干预的有吸引力的靶点。对这些DUBs底物的持续研究将有助于进一步了解它们作为靶点的潜力。
