Promotion of Endoplasmic Reticulum-Associated Degradation of Procathepsin D by Human Herpesvirus 8-Encoded Viral Interleukin-6
Promotion of Endoplasmic Reticulum-Associated Degradation of Procathepsin D by Human Herpesvirus 8-Encoded Viral Interleukin-6
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DOI：
10.1128/jvi.00375-15
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发表时间：
2015-08-01
影响因子：
5.4
通讯作者：
Nicholas, John
中科院分区：
文献类型：
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作者：
Chen, Daming;Nicholas, John
人疱疹病毒8的白细胞介素-6同源物（病毒白细胞介素-6 [vIL-6]）由于其通过gp 130受体信号传导实现的促增殖、炎症和血管生成特性而与病毒发病机制有关。在原发性渗出性淋巴瘤（PEL）细胞中，vIL-6潜伏表达，并且对于正常细胞生长和活力是必需的。这部分是通过抑制促凋亡组织蛋白酶D（CatD）介导的，通过内质网（ER）定位的CatD前体，pro-CatD（pCatD）和vIL-6与以前未知的ER膜蛋白维生素K环氧化物还原酶复合物亚基1变体2（VKORC 1v 2）的共复合。vIL-6对CatD的抑制也发生在PEL细胞中重新激活的生产性复制期间，并且可能有助于vIL-6的前复制功能。在这里，我们报告说，vIL-6抑制CatD通过vIL-6，VKORC 1v 2，和pCatD协会与ER相关的降解（ERAD）机制的组成部分。在转染的细胞中，vIL-6沿着CatD的表达导致CatD水平的蛋白酶体依赖性（对底物敏感）降低和pCatD多聚泛素化的促进。消耗特定ERAD相关异构酶、凝集素和易位子组分，包括ERAD E3泛素连接酶HRD 1，减少vIL-6对CatD的抑制。共沉淀试验鉴定了VKORC 1v 2、vIL-6和pCatD与易位蛋白（SEL 1 L和/或HRD 1）和ERAD相关凝集素OS 9和XTP 3-B的直接或间接相互作用。内源性CatD在PEL细胞中的表达增加ERAD组件的耗尽，和抑制CatD的vIL-6在PEL细胞中的过表达依赖于HRD 1。我们的数据揭示了一个新的机制ER定位vIL-6的活动，并进一步表征VKORC 1v 2 function.IMPORTANCEHuman疱疹病毒8（HHV-8）病毒白细胞介素-6（vIL-6），不像细胞的IL-6蛋白，分泌效率低下，主要在内质网（ER），从那里它可以通过gp 130受体信号隔离。我们最近报道，vIL-6还与一种新的膜蛋白，称为维生素K环氧化物还原酶复合物亚基1变体2（VKORC 1v 2）和介导的VKORC 1v 2-cointeracting组织蛋白酶D，压力释放的促凋亡蛋白的抑制产生负面影响HHV-8潜伏感染的原发性渗出性淋巴瘤（PEL）细胞活力和重新激活的病毒生产性复制。在这里，我们已经研究了VKORC 1v 2-vIL-6相互作用依赖性抑制组织蛋白酶D的机制基础，并发现vIL-6的这种新活性是通过VKORC 1v 2、组织蛋白酶原D和vIL-6与ER相关降解（ERAD）机制的组分的共缔合来介导的。我们的研究结果为VKORC 1v 2介导的vIL-6活性的潜在抗病毒和治疗靶向提供了重要信息，也表明了VKORC 1v 2在正常细胞生物学中的功能性质。
The interleukin-6 homologue (viral interleukin-6 [vIL-6]) of human herpesvirus 8 is implicated in viral pathogenesis due to its proproliferative, inflammatory, and angiogenic properties, effected through gp130 receptor signaling. In primary effusion lymphoma (PEL) cells, vIL-6 is expressed latently and is essential for normal cell growth and viability. This is mediated partly via suppression of proapoptotic cathepsin D (CatD) via cocomplexing of the endoplasmic reticulum (ER)-localized CatD precursor, pro-CatD (pCatD), and vIL-6 with the previously uncharacterized ER membrane protein vitamin K epoxide reductase complex subunit 1 variant 2 (VKORC1v2). vIL-6 suppression of CatD occurs also during reactivated productive replication in PEL cells and is likely to contribute to proreplication functions of vIL-6. Here, we report that vIL-6 suppresses CatD through vIL-6, VKORC1v2, and pCatD association with components of the ER-associated degradation (ERAD) machinery. In transfected cells, expression of vIL-6 along with CatD led to proteasome-dependent (inhibitor-sensitive) decreases in CatD levels and the promotion of pCatD polyubiquitination. Depletion of particular ERAD-associated isomerases, lectins, and translocon components, including ERAD E3 ubiquitin ligase HRD1, diminished suppression of CatD by vIL-6. Coprecipitation assays identified direct or indirect interactions of VKORC1v2, vIL-6, and pCatD with translocon proteins (SEL1L and/or HRD1) and ERAD-associated lectins OS9 and XTP3-B. Endogenous CatD expression in PEL cells was increased by depletion of ERAD components, and suppression of CatD by vIL-6 overexpression in PEL cells was dependent on HRD1. Our data reveal a new mechanism of ER-localized vIL-6 activity and further characterize VKORC1v2 function.IMPORTANCEHuman herpesvirus 8 (HHV-8) viral interleukin-6 (vIL-6), unlike cellular IL-6 proteins, is secreted inefficiently and sequestered mainly in the endoplasmic reticulum (ER), from where it can signal through the gp130 receptor. We have recently reported that vIL-6 also associates with a novel membrane protein termed vitamin K epoxide reductase complex subunit 1 variant 2 (VKORC1v2) and mediates suppression of VKORC1v2-cointeracting cathepsin D, a stress-released proapoptotic protein negatively impacting HHV-8 latently infected primary effusion lymphoma (PEL) cell viability and reactivated virus productive replication. Here, we have examined the mechanistic basis of the VKORC1v2-vIL-6 interaction-dependent suppression of cathepsin D and have found that this novel activity of vIL-6 is mediated through coassociation of VKORC1v2, procathepsin D, and vIL-6 with components of the ER-associated degradation (ERAD) machinery. Our findings provide information of significance for potential antiviral and therapeutic targeting of VKORC1v2-mediated vIL-6 activities and also indicate the nature of VKORC1v2 function in normal cell biology.