HIV-1 Promotes the Degradation of Components of the Type 1 IFN JAK/STAT Pathway and Blocks Anti-viral ISG Induction.
HIV-1 Promotes the Degradation of Components of the Type 1 IFN JAK/STAT Pathway and Blocks Anti-viral ISG Induction.
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DOI：
10.1016/j.ebiom.2018.03.006
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发表时间：
2018-04
期刊：
影响因子：
11.1
通讯作者：
Stevenson NJ
中科院分区：
文献类型：
--
作者：
Gargan S;Ahmed S;Mahony R;Bannan C;Napoletano S;O'Farrelly C;Borrow P;Bergin C;Stevenson NJ
抗逆转录病毒疗法成功地抑制了HIV-1感染，但未能治愈。在感染过程中，1型IFN通常在病毒清除中发挥重要作用，但在体内IFN-α对HIV-1感染的影响不大，这表明其可能被HIV靶向。在这里，我们报告说，HIV蛋白，Vif，抑制有效的IFN-α信号通过降解的必要JAK/STAT途径的组成部分。我们发现STAT 1和STAT 3在表达Vif的HEK 293 T细胞中特异性减少，并且全长感染性HIV-1 IIIB株以Vif依赖性方式促进其降解。骨髓ThP-1细胞的HIV-1 IIIB感染也减少了IFN-α介导的抗病毒基因ISG 15的诱导，但不减少MxA，揭示了这种HIV-1介导的免疫逃避策略的功能后果。有趣的是，虽然体外IIIB感染原代人PBMC后总STAT水平未降低，但IFN-α介导的STAT 1和STAT 3磷酸化和ISG诱导明显降低，去除Vif（IIIBΔVif），部分恢复pSTAT、ISG 15和MxB诱导。同样，与健康对照相比，HIV感染患者PBMC中pSTAT 1和pSTAT 3表达以及IFN-α诱导的ISG 15降低。此外，IFN-α预处理a CEM T淋巴母细胞显著抑制HIV感染/复制（通过细胞p24测量），仅在不存在Vif（IIIBΔVif）的情况下，但不能抑制全长IIIB感染。当分析Vif可能靶向JAK/STAT通路的机制时，我们发现Vif与STAT 1和STAT 3相互作用（但不与STAT 2相互作用），并且其表达促进两种蛋白质的泛素化和MG 132敏感性蛋白质体降解。Vif的Elongin-Cullin-SOCS盒结合基序能够形成活性E3连接酶复合物，我们发现这是Vif降解STAT 1和STAT 3所必需的。事实上，E3连接酶支架蛋白Cul 5和Rbx 2也被发现是Vif介导的STAT 1和STAT 3的蛋白酶体降解所必需的。这些结果揭示了HIV-1-Vif的靶点，并证明了HIV-1如何损害1型IFN的抗病毒活性，这可能解释了为什么内源性和治疗性IFN-α都不能激活对HIV感染的更有效控制。HIV-Vif蛋白靶向1型IFN JAK/STAT途径蛋白（STAT 1和STAT 3）进行蛋白酶体降解。HIV-Vif使用宿主ECS E3连接酶复合物降解STAT 1和STAT 3。HIV-Vif蛋白阻断IFN-α诱导的STAT磷酸化和抗病毒ISG诱导尽管I型IFN在病毒感染后强烈表达，但IFN-α未能治愈HIV。我们的研究表明，HIV-Vif蛋白通过降解其JAK/STAT信号级联介导IFN-α抗病毒反应的抑制。这些结果概述了HIV阻断这种重要的抗病毒途径的机制，并可能解释为什么这种强大的细胞因子不能消除病毒。这些发现使我们对艾滋病毒介导的免疫逃避的理解发生了范式转变，并可能成为我们全球寻求开发新的免疫恢复治疗艾滋病毒的基础。
Anti-retroviral therapy successfully suppresses HIV-1 infection, but fails to provide a cure. During infection Type 1 IFNs normally play an essential role in viral clearance, but in vivo IFN-α only has a modest impact on HIV-1 infection, suggesting its possible targeting by HIV. Here, we report that the HIV protein, Vif, inhibits effective IFN-α signalling via degradation of essential JAK/STAT pathway components. We found that STAT1 and STAT3 are specifically reduced in HEK293T cells expressing Vif and that full length, infectious HIV-1 IIIB strain promotes their degradation in a Vif-dependent manner. HIV-1 IIIB infection of myeloid ThP-1 cells also reduced the IFN-α-mediated induction of the anti-viral gene, ISG15, but not MxA, revealing a functional consequence of this HIV-1-mediated immune evasion strategy. Interestingly, while total STAT levels were not reduced upon in vitro IIIB infection of primary human PBMCs, IFN-α-mediated phosphorylation of STAT1 and STAT3 and ISG induction were starkly reduced, with removal of Vif (IIIBΔVif), partially restoring pSTATs, ISG15 and MxB induction. Similarly, pSTAT1 and pSTAT3 expression and IFN-α-induced ISG15 were reduced in PBMCs from HIV-infected patients, compared to healthy controls. Furthermore, IFN-α pre-treatment of a CEM T lymphoblast cells significantly inhibited HIV infection/replication (measured by cellular p24), only in the absence of Vif (IIIBΔVif), but was unable to suppress full length IIIB infection. When analysing the mechanism by which Vif might target the JAK/STAT pathway, we found Vif interacts with both STAT1 and STAT3, (but not STAT2), and its expression promotes ubiquitination and MG132-sensitive, proteosomal degradation of both proteins. Vif's Elongin-Cullin-SOCS-box binding motif enables the formation of an active E3 ligase complex, which we found to be required for Vif's degradation of STAT1 and STAT3. In fact, the E3 ligase scaffold proteins, Cul5 and Rbx2, were also found to be essential for Vif-mediated proteasomal degradation of STAT1 and STAT3. These results reveal a target for HIV-1-Vif and demonstrate how HIV-1 impairs the anti-viral activity of Type 1 IFNs, possibly explaining why both endogenous and therapeutic IFN-α fail to activate more effective control over HIV infection. HIV-Vif protein targets Type 1 IFN JAK/STAT pathway proteins (STAT1 and STAT3) for proteasomal degradation. HIV-Vif uses the host ECS E3 ligase complex to degrade STAT1 and STAT3. HIV-Vif protein blocks IFN-α-induced STAT phosphorylation and anti-viral ISG induction. Even though Type I IFNs are strongly expressed upon viral infection, IFN-α fails to cure HIV. Our study reveals that the HIV-Vif protein mediates inhibition of IFN-α's anti-viral responses through degradation of its JAK/STAT signalling cascade. These results outline the mechanism by which HIV blocks this essential anti-viral pathway and may explain why this powerful cytokine cannot eliminate the virus. These discoveries make a paradigm shift in our understanding of HIV-mediated immune evasion and may be fundamental in our global quest to develop new, immune restoring, therapy against HIV.
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影响因子：
2.3
作者：
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DOI：
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