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Mechanistic studies of an unexpected HIV-1 Vpu function

HIV-1 Vpu 意外功能的机制研究

基本信息

批准号：
8071196
负责人：
Marc C Johnson
金额：
$ 18.75万
依托单位：
UNIVERSITY OF MISSOURI-COLUMBIA
依托单位国家：
美国
项目类别：
财政年份：
2010
资助国家：
美国
起止时间：
2010-05-12 至 2013-04-30
项目状态：
已结题

项目摘要

DESCRIPTION (provided by applicant): HIV-1 infections have caused a worldwide pandemic that has claimed the lives of over 20 million people and infected over 40 million more. In addition to its importance in public health, HIV-1 and other retroviruses have also become important tools for delivery of foreign genes into target cells for gene therapy and other applications. During the assembly process HIV-1 must acquire a viral surface glycoprotein to target and fuse with host cells. Although HIV-1 usually acquires it own surface glycoprotein, it can also assemble into infectious virions with certain foreign viral glycoproteins to form what is called a pseudotyped virus. However, not all foreign glycoproteins are compatible with HIV-1. The glycoprotein from gammaretrovirus gibbon ape leukemia virus (GaLV Env) is an example of a glycoprotein that is not compatible with HIV-1. Co-expression of HIV-1 with GaLV Env yields essentially no infectious pseudotyped virus particles. The element in GaLV responsible for this incompatibility has been mapped to the C-terminal cytoplasmic tail domain (CTD) of the glycoprotein. We recently discovered that the incompatibility between HIV-1 and GaLV Env is modulated by the HIV-1 accessory protein Vpu. In the absence of Vpu, glycoproteins with a GaLV CTD are incorporated into HIV-1 particles, and the particles are infectious. However, in the presence of Vpu, these glycoproteins are not incorporated into HIV-1 particles, and the particle infectivity is reduced by 50 to 100 fold. In some ways this phenomenon is similar to the known Vpu activity of targeting the host cell protein CD4 for degradation at the endoplasmic reticulum. However, the mechanism of GaLV Env restriction is distinct from current models for how CD4 is restricted. Most nobly, Vpu only restricts certain retroviruses from acquiring glycoproteins with a GaLV CTD, and the restriction occurs even in presence of significant surface glycoprotein expression. Although Vpu is known to modulate certain host cell proteins to enhance viral infectivity, it is surprising that Vpu specifically modulates the surface glycoprotein from a foreign virus that displays no obvious similarity to Vpu's known targets. We therefore hypothesize that GaLV Env restriction by Vpu is an incidental effect resulting from GaLV Env mimicking a cellular protein and 'tricking' Vpu into targeting it. By characterizing this downmodulation, we can (1) elucidate the actions of Vpu in infected cells and (2) identify the precise motif in MLV/GaLV Env targeted by Vpu, yielding the necessary information to identify natural Vpu targets in silico. PUBLIC HEALTH RELEVANCE: HIV-1 infections have caused a worldwide pandemic that has claimed the lives of over 20 million people and infected over 40 million more. It has long been recognized that viruses, including HIV, have distinct mechanisms for modulating the host cell to facilitate virus assembly, but these mechanisms remain poorly understood. An understanding of what and how HIV-1 accessory proteins modulate proteins in the infected cell could lead to new targets for antiviral therapies.

描述（由申请人提供）：HIV-1感染已造成全球性大流行，夺去了2000多万人的生命，并感染了4000多万人。除了在公共卫生中的重要性外，HIV-1和其他逆转录病毒也已成为将外源基因输送到靶细胞以进行基因治疗和其他应用的重要工具。在装配过程中，HIV-1必须获得病毒表面糖蛋白以靶向宿主细胞并与宿主细胞融合。虽然HIV-1通常获得其自身的表面糖蛋白，但它也可以与某些外来病毒糖蛋白组装成感染性病毒粒子，形成所谓的假型病毒。然而，并非所有的外源糖蛋白都与HIV-1相容。来自γ逆转录病毒类人猿白血病病毒的糖蛋白（GaLV Env）是与HIV-1不相容的糖蛋白的一个例子。HIV-1与GaLV Env的共表达基本上不产生感染性假型病毒颗粒。GaLV中负责这种不相容性的元件已被映射到糖蛋白的C-末端胞质尾区（CTD）。我们最近发现HIV-1和GaLV Env之间的不相容性受到HIV-1辅助蛋白Vpu的调节。在不存在Vpu的情况下，具有GaLV CTD的糖蛋白被掺入HIV-1颗粒中，并且该颗粒具有感染性。然而，在Vpu的存在下，这些糖蛋白不掺入HIV-1颗粒中，并且颗粒感染性降低50至100倍。在某些方面，这种现象类似于靶向宿主细胞蛋白CD 4以在内质网降解的已知Vpu活性。然而，GaLV Env限制的机制与目前关于如何限制CD 4的模型不同。最重要的是，Vpu仅限制某些逆转录病毒获得具有GaLV CTD的糖蛋白，并且即使在存在显著的表面糖蛋白表达的情况下也会发生限制。尽管已知Vpu调节某些宿主细胞蛋白以增强病毒感染性，但令人惊讶的是，Vpu特异性调节来自与Vpu的已知靶标没有明显相似性的外来病毒的表面糖蛋白。因此，我们假设Vpu对GaLV Env的限制是GaLV Env模仿细胞蛋白并“诱骗”Vpu靶向其的附带效应。通过表征这种下调，我们可以（1）阐明Vpu在感染细胞中的作用，（2）确定Vpu靶向的MLV/GaLV Env中的精确基序，从而获得必要的信息以通过计算机识别天然Vpu靶点。公共卫生关系：HIV-1感染已造成世界范围的流行病，夺去了2 000多万人的生命，另有4 000多万人受到感染。长期以来，人们已经认识到，包括HIV在内的病毒具有调节宿主细胞以促进病毒组装的独特机制，但这些机制仍然知之甚少。了解HIV-1辅助蛋白是什么以及如何调节感染细胞中的蛋白质，可能会为抗病毒治疗带来新的靶点。