Noble Beth, Abada Paolo, Nunez-Iglesias Juan, Cannon Paula M
Department of Biochemistry and Molecular Biology, University of Southern California Keck School of Medicine, Los Angeles, USA.
J Virol. 2006 Mar;80(6):2924-32. doi: 10.1128/JVI.80.6.2924-2932.2006.
The envelope (Env) protein of human immunodeficiency virus type 2 (HIV-2) and the HIV-1 Vpu protein stimulate the release of retroviral particles from human cells that restrict virus production, an activity that we call the enhancement of virus release (EVR). We have previously shown that two separate domains in the HIV-2 envelope protein are required for this activity: a glycine-tyrosine-x-x-hydrophobic (GYxxtheta) motif in the cytoplasmic tail and an unmapped region in the ectodomain of the protein. We here report that the cellular partner of the GYxxtheta motif is the adaptor protein complex AP-2. The mutation of this motif or the depletion of AP-2 by RNA interference abrogated EVR activity and changed the cellular distribution of the Env from a predominantly punctate pattern to a more diffuse distribution. Since the L domain of equine infectious anemia virus (EIAV) contains a Yxxtheta motif that interacts with AP-2, we used both wild-type and L domain-defective particles of HIV-1 and EIAV to examine whether the HIV-2 Env EVR function was analogous to L domain activity. We observed that the production of all particles was stimulated by HIV-2 Env or Vpu, suggesting that the L domain and EVR activities play independent roles in the release of retroviruses. Interestingly, we found that the cytoplasmic tail of the murine leukemia virus (MLV) Env could functionally substitute for the HIV-2 Env tail, but it did so in a manner that did not require a Yxxtheta motif or AP-2. The cellular distribution of the chimeric HIV-2/MLV Env was significantly less punctate than the wild-type Env, although confocal analysis revealed an overlap in the steady-state locations of the two proteins. Taken together, these data suggest that the essential GYxxtheta motif in the HIV-2 Env tail recruits AP-2 in order to direct Env to a cellular pathway or location that is necessary for its ability to enhance virus release but that an alternate mechanism provided by the MLV Env tail can functionally substitute.
2型人类免疫缺陷病毒（HIV-2）的包膜（Env）蛋白和HIV-1的Vpu蛋白可刺激限制病毒产生的人类细胞释放逆转录病毒颗粒，我们将这种活性称为病毒释放增强（EVR）。我们之前已经表明，HIV-2包膜蛋白中的两个独立结构域参与了这一活性：细胞质尾中的甘氨酸-酪氨酸-x-x-疏水（GYxxtheta）基序以及该蛋白胞外域中的一个未定位区域。我们在此报告，GYxxtheta基序的细胞伴侣是衔接蛋白复合物AP-2。该基序的突变或RNA干扰导致的AP-2缺失均消除了EVR活性，并使Env的细胞分布从主要的点状模式变为更弥散的分布。由于马传染性贫血病毒（EIAV）的L结构域包含一个与AP-2相互作用的Yxxtheta基序，我们使用HIV-1和EIAV的野生型及L结构域缺陷型颗粒来研究HIV-2 Env的EVR功能是否类似于L结构域活性。我们观察到，所有颗粒的产生均受到HIV-2 Env或Vpu的刺激，这表明L结构域和EVR活性在逆转录病毒释放中发挥独立作用。有趣的是，我们发现鼠白血病病毒（MLV）Env的细胞质尾在功能上可以替代HIV-2 Env尾，但这样做的方式并不需要Yxxtheta基序或AP-2。嵌合的HIV-2/MLV Env的细胞分布明显比野生型Env的点状分布少，尽管共聚焦分析显示这两种蛋白在稳态位置上有重叠。综上所述，这些数据表明，HIV-2 Env尾中的关键GYxxtheta基序招募AP-2，以便将Env引导至对其增强病毒释放能力至关重要的细胞途径或位置，但MLV Env尾提供的另一种机制在功能上可以替代。
