Protein-disulfide isomerase-mediated reduction of two disulfide bonds of HIV envelope glycoprotein 120 occurs post-CXCR4 binding and is required for fusion
Protein-disulfide isomerase-mediated reduction of two disulfide bonds of HIV envelope glycoprotein 120 occurs post-CXCR4 binding and is required for fusion
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DOI：
10.1074/jbc.m205467200
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发表时间：
2003-01-31
影响因子：
4.8
通讯作者：
Fenouillet, E
中科院分区：
文献类型：
--
作者：
Barbouche, R;Miquelis, R;Fenouillet, E
人免疫缺陷病毒（HIV）包膜（Env）糖蛋白（gp）120是将HIV附着于淋巴细胞表面受体CD4和CXCR 4的高度二硫键键合的分子。gp120内的构象变化由结合引起并触发HIV/细胞融合。抑制淋巴细胞表面相关蛋白二硫键异构酶（PDI）阻断HIV/细胞融合，表明Env内的氧化还原变化是必需的。使用基于硫醇试剂的灵敏测定，我们表明（i）gp120的硫醇含量为0.5 - 1 pmol SH/pmol gp120，所述gp120由哺乳动物细胞分泌或结合至淋巴细胞表面，使CD4而非CXCR 4结合（ii）PDI抑制剂阻止了这种变化;（iii）显示2 SH/gp120的gp120显示出CD4结合能力，但不显示CXCR4结合能力。此外，PDI抑制不损害gp120与受体的结合。我们的结论是，平均两个九个二硫化物的gp120减少在与淋巴细胞表面的相互作用后，CXCR4结合融合之前，细胞表面的PDI催化这一过程。Env内的二硫键重组可能构成诱导融合能力的受体结合后构象变化的分子基础。
The human immunodeficiency virus (HIV) envelope (Env) glycoprotein (gp) 120 is a highly disulfide-bonded molecule that attaches HIV to the lymphocyte surface receptors CD4 and CXCR4. Conformation changes within gp120 result from binding and trigger HIV/cell fusion. Inhibition of lymphocyte surface-associated protein-disulfide isomerase (PDI) blocks HIV/cell fusion, suggesting that redox changes within Env are required. Using a sensitive assay based on a thiol reagent, we show that (i) the thiol content of gp120, either secreted by mammalian cells or bound to a lymphocyte surface enabling CD4 but not CXCR4 binding, was 0.5-1 pmol SH/pmol gp120 (SH/gp120), whereas that of gp120 after its interaction with a surface enabling both CD4 and CXCR4 binding was raised to 4 SH/gp120; (ii) PDI inhibitors prevented this change; and (iii) gp120 displaying 2 SH/gp120 exhibited CD4 but not CXCR4 binding capacity. In addition, PDI inhibition did not impair gp120 binding to receptors. We conclude that on average two of the nine disulfides of gp120 are reduced during interaction with the lymphocyte surface after CXCR4 binding prior to fusion and that cell surface PDI catalyzes this process. Disulfide bond restructuring within Env may constitute the molecular basis of the post-receptor binding conformational changes that induce fusion competence.