The Amphipathic Helix of Adenovirus Capsid Protein VI Contributes to Penton Release and Postentry Sorting
The Amphipathic Helix of Adenovirus Capsid Protein VI Contributes to Penton Release and Postentry Sorting
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DOI：
10.1128/jvi.02257-14
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发表时间：
2015-02-01
影响因子：
5.4
通讯作者：
Wodrich, Harald
中科院分区：
文献类型：
--
作者：
Martinez, Ruben;Schellenberger, Pascale;Wodrich, Harald
腺病毒基因组的核传递需要衣壳穿过内细胞室的限制膜，穿过胞浆到达细胞核。这种内体逃逸是在内化时启动的，涉及进入衣壳的部分分解以释放膜裂解的内衣壳蛋白VI的高度协调过程。使用野生型和蛋白VI突变的人腺病毒血清型5(HAdV-C5)，我们表明衣壳稳定性和膜破裂是入侵腺病毒病毒粒子进入相关分选的主要决定因素。此外，通过使用电子冷冻显微镜以及五酮和蛋白VI特异性抗体，我们发现蛋白VI的两亲性螺旋通过防止五酮和蛋白VI的过早分解和部署来促进衣壳的稳定。因此，螺旋具有双重功能，通过防止过早分解和介导有效的膜溶解来避免溶酶体靶向，从而维持衣壳的亚稳态。基于这些发现和冷冻电子显微镜的结构数据，我们提出了一种改进的进入时的分解机制。在这项研究中，我们展示了腺病毒颗粒稳定性和进入依赖于进入的内体逃逸所需的膜溶解衣壳蛋白VI的释放之间的复杂联系。我们证明，腺病毒内部蛋白VI的两亲性螺旋需要稳定颗粒中的五色子，同时与进入时的五色子释放相一致，并且蛋白VI的释放介导了膜的溶解，从而阻止了溶酶体的分选。我们认为，蛋白VI的这种双重功能通过平衡腺病毒成熟颗粒的亚稳状态，确保了最佳的拆解过程。
Nuclear delivery of the adenoviral genome requires that the capsid cross the limiting membrane of the endocytic compartment and traverse the cytosol to reach the nucleus. This endosomal escape is initiated upon internalization and involves a highly coordinated process of partial disassembly of the entering capsid to release the membrane lytic internal capsid protein VI. Using wild-type and protein VI-mutated human adenovirus serotype 5 (HAdV-C5), we show that capsid stability and membrane rupture are major determinants of entry-related sorting of incoming adenovirus virions. Furthermore, by using electron cryomicroscopy, as well as penton- and protein VI-specific antibodies, we show that the amphipathic helix of protein VI contributes to capsid stability by preventing premature disassembly and deployment of pentons and protein VI. Thus, the helix has a dual function in maintaining the metastable state of the capsid by preventing premature disassembly and mediating efficient membrane lysis to evade lysosomal targeting. Based on these findings and structural data from cryo-electron microscopy, we suggest a refined disassembly mechanism upon entry.IMPORTANCEIn this study, we show the intricate connection of adenovirus particle stability and the entry-dependent release of the membrane-lytic capsid protein VI required for endosomal escape. We show that the amphipathic helix of the adenovirus internal protein VI is required to stabilize pentons in the particle while coinciding with penton release upon entry and that release of protein VI mediates membrane lysis, thereby preventing lysosomal sorting. We suggest that this dual functionality of protein VI ensures an optimal disassembly process by balancing the metastable state of the mature adenovirus particle.