Department of Immunology and Microbiology, The Scripps Research Institute, La Jolla, California, USA.
Department of Immunology and Microbiology, The Scripps Research Institute, La Jolla, California, USA
J Virol. 2018 May 14;92(11). doi: 10.1128/JVI.02256-17. Print 2018 Jun 1.
Mammarenaviruses cause chronic infections in their natural rodent hosts. Infected rodents shed infectious virus into excreta. Humans are infected through mucosal exposure to aerosols or direct contact of abraded skin with fomites, resulting in a wide range of manifestations from asymptomatic or mild febrile illness to severe life-threatening hemorrhagic fever. The mammarenavirus matrix Z protein has been shown to be a main driving force of virus budding and to act as a negative regulator of viral RNA synthesis. To gain a better understanding of how the Z protein exerts its several different functions, we investigated the interaction between Z and viral polymerase L protein using the prototypic mammarenavirus, lymphocytic choriomeningitis virus (LCMV). We found that in the presence of an active viral ribonucleoprotein (vRNP), the Z protein translocated from nonionic detergent-resistant, membrane-rich structures to a subcellular compartment with a different membrane composition susceptible to disruption by nonionic detergents. Alanine (A) substitution of a highly conserved leucine (L) at position 72 in LCMV Z protein abrogated Z-L interaction. The L72A mutation did not affect the stability or budding activity of Z when expressed alone, but in the presence of an active vRNP, mutation L72A promoted rapid degradation of Z via a proteasome- and lysosome-independent pathway. Accordingly, L72A mutation in the Z protein resulted in nonviable LCMV. Our findings have uncovered novel aspects of the dynamics of the Z protein for which a highly conserved L residue was strictly required. Several mammarenaviruses, chiefly Lassa virus (LASV), cause hemorrhagic fever disease in humans and pose important public health concerns in their regions of endemicity. Moreover, mounting evidence indicates that the worldwide-distributed, prototypic mammarenavirus, lymphocytic choriomeningitis virus (LCMV), is a neglected human pathogen of clinical significance. The mammarenavirus matrix Z protein plays critical roles in different steps of the viral life cycle by interacting with viral and host cellular components. Here we report that alanine substitution of a highly conserved leucine residue, located at position 72 in LCMV Z protein, abrogated Z-L interaction. The L72A mutation did not affect Z budding activity but promoted its rapid degradation in the presence of an active viral ribonucleoprotein (vRNP). Our findings have uncovered novel aspects of the dynamics of the Z protein for which a highly conserved L residue was strictly required.
沙粒病毒会在其自然啮齿动物宿主中引起慢性感染。受感染的啮齿动物会将传染性病毒排放到排泄物中。人类通过粘膜暴露于气溶胶或直接接触受磨损的皮肤与污染物而感染，导致从无症状或轻度发热疾病到严重危及生命的出血热等多种表现。沙粒病毒的基质 Z 蛋白已被证明是病毒出芽的主要驱动力，并作为病毒 RNA 合成的负调节剂。为了更好地了解 Z 蛋白如何发挥其多种不同功能，我们使用原型沙粒病毒淋巴细胞性脉络丛脑膜炎病毒（LCMV）研究了 Z 蛋白与病毒聚合酶 L 蛋白之间的相互作用。我们发现，在存在活性病毒核糖核蛋白（vRNP）的情况下，Z 蛋白从非离子型去垢剂抗性、富含膜的结构转位到具有不同膜组成的亚细胞区室，该亚细胞区室易受非离子型去垢剂破坏。LCMV Z 蛋白中位置 72 的高度保守亮氨酸（L）突变为丙氨酸（A），破坏了 Z-L 相互作用。当单独表达时，L72A 突变不会影响 Z 的稳定性或出芽活性，但在存在活性 vRNP 的情况下，L72A 突变通过蛋白酶体和溶酶体非依赖性途径促进 Z 的快速降解。因此，Z 蛋白中的 L72A 突变导致 LCMV 丧失活力。我们的发现揭示了 Z 蛋白动态的新方面，其中高度保守的 L 残基是严格必需的。几种沙粒病毒，主要是拉沙病毒（LASV），会在人类中引起出血热疾病，并在其流行地区引起重要的公共卫生关注。此外，越来越多的证据表明，分布广泛的原型沙粒病毒淋巴细胞性脉络丛脑膜炎病毒（LCMV）是一种被忽视的具有临床意义的人类病原体。沙粒病毒基质 Z 蛋白通过与病毒和宿主细胞成分相互作用，在病毒生命周期的不同步骤中发挥关键作用。在这里，我们报告说，LCMV Z 蛋白中位于位置 72 的高度保守亮氨酸残基被丙氨酸取代，破坏了 Z-L 相互作用。L72A 突变不影响 Z 的出芽活性，但在存在活性病毒核糖核蛋白（vRNP）的情况下促进其快速降解。我们的发现揭示了 Z 蛋白动态的新方面，其中高度保守的 L 残基是严格必需的。
