Apellániz Beatriz, Nieva José L
Biophysics Unit (CSIC, UPV/EHU) and Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), P.O. Box 644, 48080 Bilbao, Spain.
Biochim Biophys Acta. 2015 Apr;1848(4):1014-22. doi: 10.1016/j.bbamem.2015.01.011. Epub 2015 Jan 21.
The replicative cycle of the human immunodeficiency virus type-1 begins after fusion of the viral and target-cell membranes. The envelope glycoprotein gp41 transmembrane subunit contains conserved hydrophobic domains that engage and perturb the merging lipid bilayers. In this work, we have characterized the fusion-committed state generated in vesicles by CpreTM, a synthetic peptide derived from the sequence connecting the membrane-proximal external region (MPER) and the transmembrane domain (TMD) of gp41. Pre-loading cholesterol-rich vesicles with CpreTM rendered them competent for subsequent lipid-mixing with fluorescently-labeled target vesicles. Highlighting the physiological relevance of the lasting fusion-competent state, the broadly neutralizing antibody 4E10 bound to the CpreTM-primed vesicles and inhibited lipid-mixing. Heterotypic fusion assays disclosed dependence on the lipid composition of the vesicles that acted either as virus or cell membrane surrogates. Lipid-mixing exhibited above all a critical dependence on the cholesterol content in those experiments. We infer that the fusion-competent state described herein resembles bona-fide perturbations generated by the pre-hairpin MPER-TMD connection within the viral membrane.
1型人类免疫缺陷病毒的复制周期始于病毒膜与靶细胞膜融合之后。包膜糖蛋白gp41跨膜亚基包含保守的疏水结构域，这些结构域参与并扰乱融合的脂质双层。在这项研究中，我们对由CpreTM在囊泡中产生的融合 committed 状态进行了表征，CpreTM是一种合成肽，源自连接gp41的膜近端外部区域（MPER）和跨膜结构域（TMD）的序列。用CpreTM预加载富含胆固醇的囊泡，使其能够随后与荧光标记的靶囊泡进行脂质混合。具有广泛中和作用的抗体4E10与CpreTM引发的囊泡结合并抑制脂质混合，突出了持久融合能力状态的生理相关性。异型融合试验揭示了对充当病毒或细胞膜替代物的囊泡脂质组成的依赖性。在那些实验中，脂质混合首先表现出对胆固醇含量的关键依赖性。我们推断，本文所述的融合能力状态类似于病毒膜内前发夹MPER-TMD连接产生的真正扰动。
