Regulated degradation of the HIV-1 Vpu protein through a βTrCP-Independent pathway limits the release of viral particles
Regulated degradation of the HIV-1 Vpu protein through a βTrCP-Independent pathway limits the release of viral particles
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DOI：
10.1371/journal.ppat.0030104
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发表时间：
2007-07-01
期刊：
影响因子：
6.7
通讯作者：
Margottin-Goguet, Florence
中科院分区：
文献类型：
--
作者：
Estrabaud, Emilie;Le Rouzic, Erwann;Margottin-Goguet, Florence
HIV-1 的病毒蛋白 U (Vpu) 在病毒复制中具有两个已知功能：降解其细胞受体 CD4 和增强病毒颗粒释放。 Vpu 结合 CD4，同时通过其组成型磷酸化 DS(52)GXXS(56) 基序招募 SCF beta TrCP 泛素连接酶复合物的 beta TrCP 亚基。在此过程中，Vpu 被发现逃脱了降解，同时抑制了 β-TrCP 天然靶标（例如 β-连环蛋白和 I kappa B α）的降解。我们进一步解决了与 Emi1 和 Cdc25A（参与细胞周期进程的两种 bTrCP 底物）降解有关的 Vpu 抑制功能。在这些实验过程中，我们强调了 Vpu 中新磷酸化位点的重要性。我们发现，特别是在早期有丝分裂停滞的细胞中，Vpu 会经历丝氨酸 61 残基的磷酸化，该残基位于 β TrCP 结合基序附近。该磷酸化事件通过不依赖于 β TrCP 的过程触发 Vpu 降解。 HIV-1原病毒中Vpu S61的突变延长了该蛋白质的半衰期，并显着增加了HeLa细胞中HIV-1颗粒的释放。然而，调节 Vpu 周转的 S61 决定因素在 HIV-1 分离株中高度保守。总而言之，我们的结果强调了一种机制，其中 Vpu 的差异磷酸化决定了其作为不同泛素连接酶的接头或底物的命运。尽管 Vpu 降解决定因素对病毒体释放有负面影响，但它的保守性在 HIV-1 整体适应性中发挥着重要作用。
Viral protein U (Vpu) of HIV-1 has two known functions in replication of the virus: degradation of its cellular receptor CD4 and enhancement of viral particle release. Vpu binds CD4 and simultaneously recruits the beta TrCP subunit of the SCF beta TrCP ubiquitin ligase complex through its constitutively phosphorylated DS(52)GXXS(56) motif. In this process, Vpu was found to escape degradation, while inhibiting the degradation of beta TrCP natural targets such as beta-catenin and I kappa B alpha. We further addressed this Vpu inhibitory function with respect to the degradation of Emi1 and Cdc25A, two bTrCP substrates involved in cell-cycle progression. In the course of these experiments, we underscored the importance of a novel phosphorylation site in Vpu. We show that, especially in cells arrested in early mitosis, Vpu undergoes phosphorylation of the serine 61 residue, which lies adjacent to the beta TrCP-binding motif. This phosphorylation event triggers Vpu degradation by a beta TrCP-independent process. Mutation of Vpu S61 in the HIV-1 provirus extends the half-life of the protein and significantly increases the release of HIV-1 particles from HeLa cells. However, the S61 determinant of regulated Vpu turnover is highly conserved within HIV-1 isolates. Altogether, our results highlight a mechanism where differential phosphorylation of Vpu determines its fate as an adaptor or as a substrate of distinct ubiquitin ligases. Conservation of the Vpu degradation determinant, despite its negative effect on virion release, argues for a role in overall HIV-1 fitness.