The human polyoma JC virus agnoprotein acts as a viroporin.
The human polyoma JC virus agnoprotein acts as a viroporin.
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DOI：
10.1371/journal.ppat.1000801
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发表时间：
2010-03-12
期刊：
影响因子：
6.7
通讯作者：
Sawa H
中科院分区：
文献类型：
--
作者：
Suzuki T;Orba Y;Okada Y;Sunden Y;Kimura T;Tanaka S;Nagashima K;Hall WW;Sawa H
病毒感染可导致一系列细胞损伤，通常这涉及质膜和细胞内膜，导致渗透性增强。病毒孔蛋白是一组与质膜相互作用的蛋白质，其改变渗透性并且可以促进病毒颗粒的释放。虽然这些蛋白质不是病毒复制所必需的，但它们的活性肯定会促进病毒生长。进行性多灶性白质脑病（PML）是一种由多瘤病毒JC病毒（JCV）溶解性感染少突胶质细胞引起的致死性脱髓鞘疾病。JCV的基因组编码六种主要蛋白质，包括一种称为未知蛋白的小辅助蛋白。对其他多瘤病毒未知蛋白的研究表明，该蛋白可能有助于病毒在复制周期的各个阶段的繁殖，包括转录、翻译、晚期病毒蛋白的加工、病毒体的组装和病毒繁殖。我们和其他实验室的先前研究已经表明，JCV未知蛋白在JCV的繁殖中起着重要的作用，尽管尚未完全理解。在这里，我们证明了未知蛋白具有通常与病毒孔蛋白相关的特性。我们的研究结果表明：（i）Agnoprotein的缺失突变体在病毒体释放和病毒繁殖中有缺陷;（ii）Agnoprotein在感染早期定位于ER，但在感染后期也在质膜上发现;（iii）Agnoprotein是一种整合的膜蛋白并形成同源寡聚体;（iv）Agnoprotein增强细胞对翻译抑制剂潮霉素B的渗透性;（v）Agnoprotein诱导细胞外Ca 2+的流入;（vi）Agnoprotein关键的氨基酸位置8和9处的碱性残基是病毒孔蛋白活性的决定因素。未知蛋白的病毒孔蛋白样性质导致膜通透性增加和细胞内Ca 2+稳态的改变，从而导致膜功能障碍和病毒释放的增强。大多数无包膜病毒在细胞裂解后离开其宿主细胞，这涉及细胞膜的破裂和宿主细胞的死亡，并且这可能是质膜渗透性增加的最终结果。JC病毒（JC virus，JCV）是多瘤病毒家族的一种无包膜病毒，是导致进行性多灶性白质脑病（progressive multifocal leukoencephalopathy，PML）的病原体。已表明成熟子代多瘤病毒病毒粒子的细胞外释放发生在细胞解体或破裂时;然而，JCV诱导细胞裂解和促进病毒粒子释放的分子机制仍然难以理解。病毒孔蛋白是一组改变细胞膜通透性并促进病毒颗粒从感染细胞释放的蛋白质。这些蛋白质对于病毒的复制不是必需的，但它们的存在通常会增强病毒的生长。在这里，我们表明，JCV的agnoprotein形式的同源寡聚体作为一个完整的膜蛋白，并作为一个病毒孔蛋白，和agnoprotein的表达导致质膜透化和病毒体释放。这些观察结果表明，该无包膜DNA病毒的病毒体释放过程受到单一病毒蛋白的高度调节。
Virus infections can result in a range of cellular injuries and commonly this involves both the plasma and intracellular membranes, resulting in enhanced permeability. Viroporins are a group of proteins that interact with plasma membranes modifying permeability and can promote the release of viral particles. While these proteins are not essential for virus replication, their activity certainly promotes virus growth. Progressive multifocal leukoencephalopathy (PML) is a fatal demyelinating disease resulting from lytic infection of oligodendrocytes by the polyomavirus JC virus (JCV). The genome of JCV encodes six major proteins including a small auxiliary protein known as agnoprotein. Studies on other polyomavirus agnoproteins have suggested that the protein may contribute to viral propagation at various stages in the replication cycle, including transcription, translation, processing of late viral proteins, assembly of virions, and viral propagation. Previous studies from our and other laboratories have indicated that JCV agnoprotein plays an important, although as yet incompletely understood role in the propagation of JCV. Here, we demonstrate that agnoprotein possesses properties commonly associated with viroporins. Our findings demonstrate that: (i) A deletion mutant of agnoprotein is defective in virion release and viral propagation; (ii) Agnoprotein localizes to the ER early in infection, but is also found at the plasma membrane late in infection; (iii) Agnoprotein is an integral membrane protein and forms homo-oligomers; (iv) Agnoprotein enhances permeability of cells to the translation inhibitor hygromycin B; (v) Agnoprotein induces the influx of extracellular Ca2+; (vi) The basic residues at amino acid positions 8 and 9 of agnoprotein key are determinants of the viroporin activity. The viroporin-like properties of agnoprotein result in increased membrane permeability and alterations in intracellular Ca2+ homeostasis leading to membrane dysfunction and enhancement of virus release. Most non-enveloped viruses exit their host cells following cell lysis, which involves breakdown of the cell membrane and death of the host cell, and which is presumably the final result of an increase in plasma membrane permeability. JC virus (JCV) is the causative agent of progressive multifocal leukoencephalopathy (PML) and belongs to the polyomavirus family, which have non-enveloped virions. The extracellular release of mature progeny polyomavirus virions has been suggested to occur when cells disintegrate or rupture; however, the molecular mechanism(s) employed by JCV to induce cell lysis and facilitate virion release remain elusive. Viroporins are a group of proteins that modify the permeability of cellular membranes and promote the release of viral particles from infected cells. These proteins are not essential for the replication of viruses, but their presence often enhances virus growth. Here, we demonstrate that the JCV agnoprotein forms homo-oligomers as an integral membrane protein and acts as a viroporin, and that expression of agnoprotein results in plasma membrane permeabilization and virion release. These observations suggest that the process of virion release of this non-enveloped DNA virus is highly regulated by a single viral protein.
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