Dufrasne François E, Lombard Catherine, Goubau Patrick, Ruelle Jean
AIDS Reference Laboratory, Medical Microbiology Unit (MBLG), Institut de Recherche Expérimentale et Clinique (IREC), Université catholique de Louvain, Avenue Hippocrate 54 B1.54.05, B-1200 Brussels, Belgium.
Pôle de Pédiatrie (PEDI), Institut de Recherche Expérimentale et Clinique (IREC), Université catholique de Louvain, Avenue Mounier 52 B1.52.03, B-1200 Brussels, Belgium.
Viruses. 2016 Oct 14;8(10):285. doi: 10.3390/v8100285.
BST-2 or tetherin is a host cell restriction factor that prevents the budding of enveloped viruses at the cell surface, thus impairing the viral spread. Several countermeasures to evade this antiviral factor have been positively selected in retroviruses: the human immunodeficiency virus type 2 (HIV-2) relies on the envelope glycoprotein (Env) to overcome BST-2 restriction. The Env gp36 ectodomain seems involved in this anti-tetherin activity, however residues and regions interacting with BST-2 are not clearly defined. Among 32 HIV-2 ROD Env mutants tested, we demonstrated that the asparagine residue at position 659 located in the gp36 ectodomain is mandatory to exert the anti-tetherin function. Viral release assays in cell lines expressing BST-2 showed a loss of viral release ability for the HIV-2 N659D mutant virus compared to the HIV-2 wild type virus. In inactivated H9 cells, those differences were lost. Subtilisin treatment of infected cells demonstrated that the N659D mutant was more tethered at the cell surface. Förster resonance energy transfer (FRET) experiments confirmed a direct molecular link between Env and BST-2 and highlighted an inability of the mutant to bind BST-2. We also tested a virus presenting a truncation of 109 amino acids at the C-terminal part of Env, a cytoplasmic tail partial deletion that is spontaneously selected in vitro. Interestingly, viral release assays and FRET experiments indicated that a full Env cytoplasmic tail was essential in BST-2 antagonism. In HIV-2 infected cells, an efficient Env-mediated antagonism of BST-2 is operated through an intermolecular link involving the asparagine 659 residue as well as the C-terminal part of the cytoplasmic tail.
BST-2或栓系蛋白是一种宿主细胞限制因子，可阻止包膜病毒在细胞表面出芽，从而损害病毒传播。逆转录病毒中已积极选择了几种逃避这种抗病毒因子的对策：2型人类免疫缺陷病毒（HIV-2）依靠包膜糖蛋白（Env）来克服BST-2的限制。Env gp36胞外域似乎参与了这种抗栓系蛋白活性，然而，与BST-2相互作用的残基和区域尚未明确界定。在测试的32个HIV-2 ROD Env突变体中，我们证明位于gp36胞外域第659位的天冬酰胺残基对于发挥抗栓系蛋白功能是必需的。在表达BST-2的细胞系中进行的病毒释放试验表明，与HIV-2野生型病毒相比，HIV-2 N659D突变病毒的病毒释放能力丧失。在灭活的H9细胞中，这些差异消失了。对感染细胞进行枯草杆菌蛋白酶处理表明，N659D突变体在细胞表面的栓系作用更强。荧光共振能量转移（FRET）实验证实了Env与BST-2之间存在直接的分子联系，并突出显示突变体无法结合BST-2。我们还测试了一种病毒变体，该变体在Env的C末端部分截短了109个氨基酸，这是在体外自发选择的细胞质尾巴部分缺失。有趣的是，病毒释放试验和FRET实验表明，完整的Env细胞质尾巴对于BST-2拮抗作用至关重要。在HIV-2感染的细胞中，有效的Env介导的BST-2拮抗作用是通过涉及天冬酰胺659残基以及细胞质尾巴C末端部分的分子间联系来实现的。
