Department of Infectious Disease, King's College London School of Medicine, Guy's Hospital, London SE1 9RT, UK.
J Virol. 2011 Oct;85(19):9737-48. doi: 10.1128/JVI.00479-11. Epub 2011 Jul 20.
Tetherin (BST-2/CD317) is thought to restrict retroviral particle release by cross-linking nascent viral and cellular membranes. Unlike the Vpu proteins encoded by human immunodeficiency virus type 1 (HIV-1) group M strains (M-Vpu), those from the nonpandemic HIV-1 group O (O-Vpu) are not able to counteract tetherin activity. Here, we characterized the basis of this defect in O-Vpu. O-Vpu differs from M-Vpu in that it fails to interact with tetherin and downregulate it from the cell surface. Unlike M-Vpu, O-Vpu localizes to the endoplasmic reticulum (ER) rather than the trans-Golgi network (TGN). Interestingly M-Vpu bearing an ER retention signal at the C terminus localizes similarly to O-Vpu. While it still interacts with tetherin, it fails to promote virus release, suggesting that O-Vpu deficiency correlates with its cellular distribution in the endoplasmic reticulum as well as its failure to bind tetherin. O-Vpu-M-Vpu chimeras were designed to identify the minimal changes required to restore tetherin antagonism. While several chimeric proteins bearing residues of the M-Vpu transmembrane domain into the O-Vpu transmembrane domain recovered tetherin binding in coimmunoprecipitation studies, efficient antagonism required an additional glutamic acid-to-lysine change in the membrane-proximal hinge region of the O-Vpu cytoplasmic tail that was sufficient to abolish ER retention and permit TGN localization.
tetherin（BST-2/CD317）被认为通过交联新生病毒和细胞膜来限制逆转录病毒颗粒的释放。与人类免疫缺陷病毒 1 型（HIV-1）M 株编码的 Vpu 蛋白（M-Vpu）不同，非流行的 HIV-1 O 组（O-Vpu）的 Vpu 蛋白不能拮抗 tetherin 的活性。在这里，我们描述了 O-Vpu 中这种缺陷的基础。O-Vpu 与 M-Vpu 的不同之处在于它不能与 tetherin 相互作用，并将其从细胞表面下调。与 M-Vpu 不同，O-Vpu 定位于内质网（ER）而不是反式高尔基体网络（TGN）。有趣的是，带有 C 端 ER 保留信号的 M-Vpu 也定位于类似的位置。虽然它仍然与 tetherin 相互作用，但它不能促进病毒释放，这表明 O-Vpu 的缺乏与其在 ER 中的细胞分布以及与 tetherin 的结合失败有关。设计了 O-Vpu-M-Vpu 嵌合体以确定恢复 tetherin 拮抗作用所需的最小变化。虽然几个带有 M-Vpu 跨膜域残基的嵌合蛋白在 coimmunoprecipitation 研究中恢复了与 tetherin 的结合，但有效的拮抗作用需要在 O-Vpu 细胞质尾部的膜近端铰链区域中额外的谷氨酸到赖氨酸变化，这足以消除 ER 保留并允许 TGN 定位。
