高效的疱疹病毒核输出需要核骨架与细胞骨架连接物的完整性。
Integrity of the Linker of Nucleoskeleton and Cytoskeleton Is Required for Efficient Herpesvirus Nuclear Egress.
作者信息
Klupp Barbara G, Hellberg Teresa, Granzow Harald, Franzke Kati, Dominguez Gonzalez Beatriz, Goodchild Rose E, Mettenleiter Thomas C
机构信息
Institute of Molecular Virology and Cell Biology, Friedrich-Loeffler-Institut, Greifswald-Insel Riems, Germany.
Institute of Infectology, Friedrich-Loeffler-Institut, Greifswald-Insel Riems, Germany.
出版信息
J Virol. 2017 Sep 12;91(19). doi: 10.1128/JVI.00330-17. Print 2017 Oct 1.
Herpesvirus capsids assemble in the nucleus, while final virion maturation proceeds in the cytoplasm. This requires that newly formed nucleocapsids cross the nuclear envelope (NE), which occurs by budding at the inner nuclear membrane (INM), release of the primary enveloped virion into the perinuclear space (PNS), and subsequent rapid fusion with the outer nuclear membrane (ONM). During this process, the NE remains intact, even at late stages of infection. In addition, the spacing between the INM and ONM is maintained, as is that between the primary virion envelope and nuclear membranes. The linker of nucleoskeleton and cytoskeleton (LINC) complex consists of INM proteins with a luminal SUN (Sad1/UNC-84 homology) domain connected to ONM proteins with a KASH (Klarsicht, ANC-1, SYNE homology) domain and is thought to be responsible for spacing the nuclear membranes. To investigate the role of the LINC complex during herpesvirus infection, we generated cell lines constitutively expressing dominant negative (dn) forms of SUN1 and SUN2. Ultrastructural analyses revealed a significant expansion of the PNS and the contiguous intracytoplasmic lumen, most likely representing endoplasmic reticulum (ER), especially in cells expressing dn-SUN2. After infection, primary virions accumulated in these expanded luminal regions, also very distant from the nucleus. The importance of the LINC complex was also confirmed by reduced progeny virus titers in cells expressing dn-SUN2. These data show that the intact LINC complex is required for efficient nuclear egress of herpesviruses, likely acting to promote fusion of primary enveloped virions with the ONM. While the viral factors for primary envelopment of nucleocapsids at the inner nuclear membrane are known to the point of high-resolution structures, the roles of cellular components and regulators remain enigmatic. Furthermore, the machinery responsible for fusion with the outer nuclear membrane is unsolved. We show here that dominant negative SUN2 interferes with efficient herpesvirus nuclear egress, apparently by interfering with fusion between the primary virion envelope and outer nuclear membrane. This identifies a new cellular component important for viral egress and implicates LINC complex integrity in nonconventional nuclear membrane trafficking.
疱疹病毒衣壳在细胞核中组装,而病毒体的最终成熟在细胞质中进行。这要求新形成的核衣壳穿过核膜(NE),这一过程通过在内核膜(INM)出芽、将初级包膜病毒体释放到核周间隙(PNS)以及随后与外核膜(ONM)快速融合来实现。在此过程中,即使在感染后期,核膜仍保持完整。此外,INM和ONM之间的间距以及初级病毒体包膜与核膜之间的间距也得以维持。核骨架与细胞骨架连接复合体(LINC复合体)由具有腔内SUN(Sad1/UNC-84同源)结构域的INM蛋白与具有KASH(Klarsicht、ANC-1、SYNE同源)结构域的ONM蛋白组成,被认为负责维持核膜间距。为了研究LINC复合体在疱疹病毒感染过程中的作用,我们构建了组成型表达显性负性(dn)形式的SUN1和SUN2的细胞系。超微结构分析显示,PNS和相邻的胞质内腔显著扩张,很可能代表内质网(ER),尤其是在表达dn-SUN2的细胞中。感染后,初级病毒体积聚在这些扩张的腔区域,且离细胞核也很远。在表达dn-SUN2的细胞中后代病毒滴度降低也证实了LINC复合体的重要性。这些数据表明,完整的LINC复合体是疱疹病毒高效核输出所必需的,可能起到促进初级包膜病毒体与ONM融合的作用。虽然已知在内核膜上核衣壳初级包膜化的病毒因子已达到高分辨率结构水平,但细胞成分和调节因子的作用仍不清楚。此外,负责与外核膜融合的机制尚未解决。我们在此表明,显性负性SUN2通过干扰初级病毒体包膜与外核膜之间的融合,干扰了疱疹病毒的高效核输出。这确定了一种对病毒出芽很重要的新细胞成分,并表明LINC复合体完整性在非常规核膜运输中的作用。
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