Department of Infectious Diseases, Virology, University of Heidelberg, Heidelberg, Germany.
mBio. 2011 May 24;2(3):e00036-11. doi: 10.1128/mBio.00036-11. Print 2011.
The intrinsic immunity factor CD317 (BST-2/HM1.24/tetherin) imposes a barrier to HIV-1 release at the cell surface that can be overcome by the viral protein Vpu. Expression of Vpu results in a reduction of CD317 surface levels; however, the mechanism of this Vpu activity and its contribution to the virological antagonism are incompletely understood. Here, we characterized the influence of Vpu on major CD317 trafficking pathways using quantitative antibody-based endocytosis and recycling assays as well as a microinjection/microscopy-based kinetic de novo expression approach. We report that HIV-1 Vpu inhibited both the anterograde transport of newly synthesized CD317 and the recycling of CD317 to the cell surface, while the kinetics of CD317 endocytosis remained unaffected. Vpu trapped trafficking CD317 molecules at the trans-Golgi network, where the two molecules colocalized. The subversion of both CD317 transport pathways was dependent on the highly conserved diserine S52/S56 motif of Vpu; however, it did not require recruitment of the diserine motif interactor and substrate adaptor of the SCF-E3 ubiquitin ligase complex, β-TrCP. Treatment of cells with the malaria drug primaquine resulted in a CD317 trafficking defect that mirrored that induced by Vpu. Importantly, primaquine could functionally replace Vpu as a CD317 antagonist and rescue HIV-1 particle release.
HIV efficiently replicates in the human host and induces the life-threatening immunodeficiency AIDS. Mammalian genomes encode proteins such as CD317 that can inhibit viral replication at the cellular level. As a countermeasure, HIV has evolved genes like vpu that can antagonize these intrinsic immunity factors. Investigating the mechanism by which Vpu overcomes the virion release restriction imposed by CD317, we find that Vpu subverts recycling and anterograde trafficking pathways of CD317, resulting in surface levels of the restriction factor insufficient to block HIV-1 spread. This describes a novel mechanism of immune evasion by HIV.
内在免疫因子 CD317（BST-2/HM1.24/ tetherin）在细胞表面对 HIV-1 释放施加了一道屏障，该屏障可以被病毒蛋白 Vpu 克服。Vpu 的表达导致 CD317 表面水平降低；然而，这种 Vpu 活性的机制及其对病毒拮抗作用的贡献尚不完全清楚。在这里，我们使用定量抗体内吞和回收测定以及基于微注射/显微镜的从头表达动力学方法，研究了 Vpu 对主要 CD317 运输途径的影响。我们报告称，HIV-1 Vpu 抑制了新合成的 CD317 的顺行运输和 CD317 向细胞表面的再循环，而 CD317 内吞的动力学不受影响。Vpu 将运输中的 CD317 分子捕获在高尔基网络中，这两个分子在那里共定位。两种 CD317 运输途径的颠覆都依赖于 Vpu 高度保守的二丝氨酸 S52/S56 基序；然而，它不需要募集 SCF-E3 泛素连接酶复合物的二丝氨酸基序相互作用物和底物衔接蛋白β-TrCP。用疟疾药物伯氨喹治疗细胞会导致与 Vpu 诱导的类似的 CD317 运输缺陷。重要的是，伯氨喹可以作为 CD317 拮抗剂替代 Vpu 并拯救 HIV-1 颗粒释放。
HIV 在人类宿主中高效复制，并导致危及生命的免疫缺陷艾滋病。哺乳动物基因组编码的蛋白质，如 CD317，可以在细胞水平上抑制病毒复制。作为一种对策，HIV 已经进化出了像 vpu 这样的基因，可以拮抗这些内在免疫因子。通过研究 Vpu 克服 CD317 限制病毒释放的机制，我们发现 Vpu 颠覆了 CD317 的回收和顺行运输途径，导致限制因子的表面水平不足以阻止 HIV-1 的传播。这描述了 HIV 免疫逃避的一种新机制。
