Baker Heart and Diabetes Institute, Melbourne, VIC, Australia.
J Lipid Res. 2012 Apr;53(4):696-708. doi: 10.1194/jlr.M023119. Epub 2012 Jan 19.
HIV infection, through the actions of viral accessory protein Nef, impairs activity of cholesterol transporter ABCA1, inhibiting cholesterol efflux from macrophages and elevating the risk of atherosclerosis. Nef also induces lipid raft formation. In this study, we demonstrate that these activities are tightly linked and affect macrophage function and HIV replication. Nef stimulated lipid raft formation in macrophage cell line RAW 264.7, and lipid rafts were also mobilized in HIV-1-infected human monocyte-derived macrophages. Nef-mediated transfer of cholesterol to lipid rafts competed with the ABCA1-dependent pathway of cholesterol efflux, and pharmacological inhibition of ABCA1 functionality or suppression of ABCA1 expression by RNAi increased Nef-dependent delivery of cholesterol to lipid rafts. Nef reduced cell-surface accessibility of ABCA1 and induced ABCA1 catabolism via the lysosomal pathway. Despite increasing the abundance of lipid rafts, expression of Nef impaired phagocytic functions of macrophages. The infectivity of the virus produced in natural target cells of HIV-1 negatively correlated with the level of ABCA1. These findings demonstrate that Nef-dependent inhibition of ABCA1 is an essential component of the viral replication strategy and underscore the role of ABCA1 as an innate anti-HIV factor.
HIV 感染通过病毒辅助蛋白 Nef 的作用，损害胆固醇转运体 ABCA1 的活性，抑制巨噬细胞中胆固醇的外流，增加动脉粥样硬化的风险。Nef 还诱导脂筏的形成。在这项研究中，我们证明这些活动紧密相关，并影响巨噬细胞的功能和 HIV 的复制。Nef 刺激巨噬细胞系 RAW 264.7 中的脂筏形成，脂筏也在 HIV-1 感染的人单核细胞衍生的巨噬细胞中被动员。Nef 介导的胆固醇向脂筏的转移与 ABCA1 依赖的胆固醇外流途径竞争，而 ABCA1 功能的药理学抑制或 RNAi 抑制 ABCA1 的表达增加了 Nef 依赖的胆固醇向脂筏的转移。Nef 降低了 ABCA1 的细胞表面可及性，并通过溶酶体途径诱导 ABCA1 的降解。尽管增加了脂筏的丰度，但 Nef 的表达降低了巨噬细胞的吞噬功能。HIV-1 天然靶细胞中产生的病毒的感染性与 ABCA1 的水平呈负相关。这些发现表明，Nef 依赖性 ABCA1 的抑制是病毒复制策略的一个重要组成部分，并强调了 ABCA1 作为一种先天抗 HIV 因子的作用。
