Maeda Fumio, Arii Jun, Hirohata Yoshitaka, Maruzuru Yuhei, Koyanagi Naoto, Kato Akihisa, Kawaguchi Yasushi
Division of Molecular Virology, Department of Microbiology and Immunology, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan.
Department of Infectious Disease Control, International Research Center for Infectious Diseases, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan.
J Virol. 2017 May 26;91(12). doi: 10.1128/JVI.00271-17. Print 2017 Jun 15.
Upon herpes simplex virus 1 (HSV-1) infection, the CD98 heavy chain (CD98hc) is redistributed around the nuclear membrane (NM), where it promotes viral de-envelopment during the nuclear egress of nucleocapsids. In this study, we attempted to identify the factor(s) involved in CD98hc accumulation and demonstrated the following: (i) the null mutation of HSV-1 UL34 caused specific dispersion throughout the cytoplasm of CD98hc and the HSV-1 de-envelopment regulators, glycoproteins B and H (gB and gH); (ii) as observed with CD98hc, gB, and gH, wild-type HSV-1 infection caused redistribution of the endoplasmic reticulum (ER) markers calnexin and ERp57 around the NM, whereas the UL34-null mutation caused cytoplasmic dispersion of these markers; (iii) the ER markers colocalized efficiently with CD98hc, gB, and gH in the presence and absence of UL34 in HSV-1-infected cells; (iv) at the ultrastructural level, wild-type HSV-1 infection caused ER compression around the NM, whereas the UL34-null mutation caused cytoplasmic dispersion of the ER; and (v) the UL34-null mutation significantly decreased the colocalization efficiency of lamin protein markers of the NM with CD98hc and gB. Collectively, these results indicate that HSV-1 infection causes redistribution of the ER around the NM, with resulting accumulation of ER-associated CD98hc, gB, and gH around the NM and that UL34 is required for ER redistribution, as well as for efficient recruitment to the NM of the ER-associated de-envelopment factors. Our study suggests that HSV-1 induces remodeling of the global ER architecture for recruitment of regulators mediating viral nuclear egress to the NM. The ER is an important cellular organelle that exists as a complex network extending throughout the cytoplasm. Although viruses often remodel the ER to facilitate viral replication, information on the effects of herpesvirus infections on ER morphological integrity is limited. Here, we showed that HSV-1 infection led to compression of the global ER architecture around the NM, resulting in accumulation of ER-associated regulators associated with nuclear egress of HSV-1 nucleocapsids. We also identified HSV-1 UL34 as a viral factor that mediated ER remodeling. Furthermore, we demonstrated that UL34 was required for efficient targeting of these regulators to the NM. To our knowledge, this is the first report showing that a herpesvirus remodels ER global architecture. Our study also provides insight into the mechanism by which the regulators for HSV-1 nuclear egress are recruited to the NM, where this viral event occurs.
在单纯疱疹病毒1型（HSV-1）感染后，CD98重链（CD98hc）会重新分布在核膜（NM）周围，在核衣壳的核出芽过程中促进病毒脱壳。在本研究中，我们试图确定参与CD98hc积累的因素，并得到了以下结果：（i）HSV-1 UL34基因的无效突变导致CD98hc以及HSV-1脱壳调节因子糖蛋白B和H（gB和gH）在整个细胞质中特异性分散；（ii）与CD98hc、gB和gH的情况一样，野生型HSV-1感染导致内质网（ER）标记物钙连蛋白和内质网蛋白57在核膜周围重新分布，而UL34基因无效突变导致这些标记物在细胞质中分散；（iii）在感染HSV-1的细胞中，无论有无UL34，内质网标记物都能与CD98hc、gB和gH高效共定位；（iv）在超微结构水平上，野生型HSV-1感染导致核膜周围内质网受压，而UL34基因无效突变导致内质网在细胞质中分散；（v）UL34基因无效突变显著降低了核膜层粘连蛋白标记物与CD98hc和gB的共定位效率。总体而言，这些结果表明，HSV-1感染导致内质网在核膜周围重新分布，从而使内质网相关的CD98hc、gB和gH在核膜周围积累，并且UL34是内质网重新分布以及将内质网相关脱壳因子有效招募到核膜所必需的。我们的研究表明，HSV-1诱导内质网整体结构重塑，以便将介导病毒核出芽的调节因子招募到核膜。内质网是一种重要的细胞器，以延伸至整个细胞质的复杂网络形式存在。尽管病毒经常重塑内质网以促进病毒复制，但关于疱疹病毒感染对内质网形态完整性影响的信息有限。在这里，我们表明HSV-1感染导致核膜周围内质网整体结构受压，导致与HSV-1核衣壳核出芽相关的内质网相关调节因子积累。我们还确定HSV-1 UL34是介导内质网重塑的病毒因子。此外，我们证明UL34是将这些调节因子有效靶向到核膜所必需的。据我们所知，这是第一份显示疱疹病毒重塑内质网整体结构的报告。我们的研究还深入了解了HSV-1核出芽调节因子被招募到核膜（病毒发生这一事件的部位）的机制。
