Saribas A Sami, Khalili Kamel, Sariyer Ilker Kudret
a Department of Neuroscience Center for Neurovirology ; Temple University School of Medicine ; Philadelphia , PA USA.
Cell Cycle. 2015;14(18):2899-904. doi: 10.1080/15384101.2015.1069927. Epub 2015 Jul 15.
Viruses often exploit autophagy, a common cellular process of degradation of damaged proteins, organelles, and pathogens, to avoid destruction. HIV-1 dysregulates this process in several cell types by means of Nef protein. Nef is a small HIV-1 protein which is expressed abundantly in astrocytes of HIV-1-infected brains and has been suggested to have a role in the pathogenesis of HIV-Associated Neurocognitive Disorders (HAND). In order to explore its effect in the CNS with respect to autophagy, HIV-1 Nef was expressed in primary human fetal astrocytes (PHFA) using an adenovirus vector (Ad-Nef). We observed that Nef expression triggered the accumulation of autophagy markers, ATG8/LC3 and p62 (SQSMT1). Similar results were obtained with Bafilomycin A1, an autophagy inhibitor which blocks the fusion of autophagosome to lysosome. Furthermore co-expression of tandem LC3 vector (mRFP-EGFP-LC3) and Ad-Nef in these cells produced mainly yellow puncta (mRFP+, EGFP+) strongly suggesting that autophagosome fusion to lysosome is blocked in PHFA cells in the presence of Nef. Together these data indicate that HIV-1 Nef mimics Bafilomycin A1 and blocks the last step of autophagy thereby helping HIV-1 virus to avoid autophagic degradation in human astrocytes.
病毒常常利用自噬（一种降解受损蛋白质、细胞器和病原体的常见细胞过程）来避免被破坏。HIV-1通过Nef蛋白在多种细胞类型中破坏这一过程。Nef是一种小的HIV-1蛋白，在HIV-1感染的脑星形胶质细胞中大量表达，并被认为在HIV相关神经认知障碍（HAND）的发病机制中起作用。为了探究其在中枢神经系统中对自噬的影响，使用腺病毒载体（Ad-Nef）在原代人胎儿星形胶质细胞（PHFA）中表达HIV-1 Nef。我们观察到Nef表达引发了自噬标志物ATG8/LC3和p62（SQSMT1）的积累。用巴弗洛霉素A1（一种阻断自噬体与溶酶体融合的自噬抑制剂）也获得了类似结果。此外，在这些细胞中串联LC3载体（mRFP-EGFP-LC3）和Ad-Nef共表达主要产生黄色斑点（mRFP+，EGFP+），强烈表明在存在Nef的情况下PHFA细胞中自噬体与溶酶体的融合被阻断。这些数据共同表明，HIV-1 Nef模拟巴弗洛霉素A1并阻断自噬的最后一步，从而帮助HIV-1病毒在人星形胶质细胞中避免自噬降解。
