Department of Molecular Microbiology and Immunology, University of Missouri, School of Medicine and the Christopher S. Bond Life Sciences Center, Columbia, MO 65211, USA.
Gene Therapies Branch, Center for Biologics Evaluation and Research, FDA, 10903 New Hampshire Ave, Silver Spring, MD 20903, USA.
Viruses. 2018 Oct 19;10(10):573. doi: 10.3390/v10100573.
The Human immunodeficiency virus-1 (HIV-1) accessory protein Vpu modulates numerous proteins, including the host proteins CD4 and BST-2/tetherin. Vpu interacts with the Skp, Cullin, F-Box (SCF) ubiquitin ligase through interactions with the F-Box protein βTrCP (1 and/or 2). This interaction is dependent on phosphorylation of S in Vpu. Mutation of S, or inhibition of the SCF, abolishes most Vpu activity against CD4 and partly reduces activity against BST-2/tetherin. Recently, Vpu has also been reported to interact with the clathrin adapter proteins AP-1 and AP-2, and these interactions were also found to be required for BST-2/tetherin antagonism in an S -dependent manner. In assays where HIV-1 is pseudotyped with gibbon ape leukemia virus (GaLV Env), Vpu has also been found to prevent GaLV Env from being incorporated into viral particles, but the mechanism for this antagonism is not fully understood. To clarify the role of the βTrCPs in Vpu function we used CRISPR/Cas9 to generate a clonal cell line lacking both βTrCP-1 and -2. Vpu activity against CD4 and GaLV Env was abolished in this cell line, and activity against BST-2/tetherin reduced significantly. Mutation of the S residues no longer affected Vpu activity against BST-2/tetherin in this cell line. These data suggest that the primary role of the S residues in antagonism of CD4, GaLV Env, and BST-2/tetherin is to recruit the SCF/βTrCP ubiquitin ligase.
人类免疫缺陷病毒 1（HIV-1）辅助蛋白 Vpu 调节多种蛋白，包括宿主蛋白 CD4 和 BST-2/ tetherin。Vpu 通过与 F 盒蛋白 βTrCP（1 和/或 2）相互作用，与 Skp、Cullin、F-Box（SCF）泛素连接酶相互作用。这种相互作用依赖于 Vpu 中 S 的磷酸化。S 突变或 SCF 抑制会消除 Vpu 对 CD4 的大部分活性，并部分降低对 BST-2/tetherin 的活性。最近，Vpu 也被报道与网格蛋白衔接蛋白 AP-1 和 AP-2 相互作用，并且这些相互作用也被发现以 S 依赖性方式对抗 BST-2/tetherin 是必需的。在 HIV-1 用长臂猿白血病病毒（GaLV Env）假型化的测定中，还发现 Vpu 可防止 GaLV Env 被纳入病毒颗粒，但这种拮抗作用的机制尚未完全阐明。为了阐明 βTrCP 在 Vpu 功能中的作用，我们使用 CRISPR/Cas9 生成了一种缺乏βTrCP-1 和βTrCP-2 的克隆细胞系。在该细胞系中，Vpu 对 CD4 和 GaLV Env 的活性被消除，而对 BST-2/tetherin 的活性显著降低。S 残基的突变不再影响该细胞系中 Vpu 对 BST-2/tetherin 的活性。这些数据表明，S 残基在拮抗 CD4、GaLV Env 和 BST-2/tetherin 中的主要作用是募集 SCF/βTrCP 泛素连接酶。
