Cell biology of HIV-1 Nef and Vpr

本研究对HIV-1 Nef的作用机制进行了详细的阐述，并对HIV-1 Vpr的强大的致瘤作用进行了研究，发现HIV-1 Nef通过调节病毒颗粒增强病毒的感染性。我们发现，HIV-1病毒粒子在Nef的情况下产生的病毒进入和DNA合成的过程是有缺陷的。HIV-1有效进入细胞所需的HIV-1 Nef是生产细胞依赖性的。PxxP和RR结构域均被修饰以增强病毒进入，从而表明Nef与细胞因子的另一种相互作用参与病毒进入过程。据报道，各种重要的功能，如病毒的感染性，Nef掺入病毒粒子，和下调MHC-I定位到HIV-1 Nef的N-末端部分。通过对Nef第20位氨基酸点突变的分析，我们发现Nef诱导的MHC-I下调与其病毒粒子掺入、增强病毒感染性和CD 4下调在功能上是分离的，Vpr对细胞凋亡的调节存在争议。有的报道Vpr诱导细胞凋亡，有的报道Vpr具有抗凋亡作用。为了确定HIV-1 Vpr是否是细胞凋亡的诱导剂，我们分析了HIV-1/VSV假型病毒感染的细胞。该系统不需要选择产生Vpr的细胞，因此可以直接监测细胞中的凋亡。通过该系统，我们发现HIV- 1 Vpr是一种强的凋亡诱导剂，而Vpr没有表现出可检测到的抗凋亡作用。总之，我们在理解HIV-1 Nef和Vpr的生物学方面取得了很大进展。因此，对HIV-1 Nef和Vpr在体内的功能进行详细的研究是十分必要的。

In this study, we have demonstrated the detaild action mechanisms of HIV-1 Nef and the strong apoptosis-inducing ability of HIV-1 Vpr.HIV-1 Nef has been reported to act via modulation of viral particles to enhance virus infectivity. We showed that HIV-1 virions produced in the absence of Nef are defective for the processes of virus entry and DNA synthesis. Requirement of HIV-1 Nef for efficient entry of HIV-l into cells was producer cell-dependent The PxxP and RR domains were both dispensable for enhanced viral entry, thus suggesting that another interaction of Nef with a cellular factor(s) is involved in the process of viral entry. It has been reported that various important functions such as the viral infectivity, incorporation of Nef into virions, and down-regulation of MHC-I are mapped to the N-terminal portion of HIV-1 Nef. We showed, by the analysis of point mutants regarding 20th amino acid of the Nef, that Nef-induced MHC-I down-regulation is functionally dissociated from its virion incorporation, enhancement of viral infectivity, and CD4 down-regulation.It is controversial about the regulation of apoptosis by Vpr. Some report that Vpr induces apoptosis, and others that Vpr shows anti-apoptotic function. To determine whether HIV-1 Vpr is an inducer of apoptosis, we analyzed the cells infected with HIV-1/VSV pseudotype virus. This system does not require the selection of cells producing Vpr, and thus it is possible to directly monitor the apoptosis in cells. We showed by this system that HIV- 1 Vpr is a strong inducer of apoptosis, and that Vpr displays no detectable anti-apoptotic action.In conclusion, we have made great progress in understanding the biology of HIV-1 Nef and Vpr. It is much clearer that the detaild studies on the functions in vivo of HIV-1 Nef and Vpr is required.