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应用活细胞显微镜技术研究 F-肌动蛋白在人类免疫缺陷病毒组装中的作用。

Investigating the role of F-actin in human immunodeficiency virus assembly by live-cell microscopy.

机构信息

Department of Infectious Diseases, Virology, University Hospital Heidelberg, Heidelberg, Germany.

Bioquant, University of Heidelberg, Heidelberg, Germany.

出版信息

J Virol. 2014 Jul;88(14):7904-14. doi: 10.1128/JVI.00431-14. Epub 2014 Apr 30.

Abstract

Human immunodeficiency virus type 1 (HIV-1) particles assemble at the plasma membrane, which is lined by a dense network of filamentous actin (F-actin). Large amounts of actin have been detected in HIV-1 virions, proposed to be incorporated by interactions with the nucleocapsid domain of the viral polyprotein Gag. Previous studies addressing the role of F-actin in HIV-1 particle formation using F-actin-interfering drugs did not yield consistent results. Filamentous structures pointing toward nascent HIV-1 budding sites, detected by cryo-electron tomography and atomic force microscopy, prompted us to revisit the role of F-actin in HIV-1 assembly by live-cell microscopy. HeLa cells coexpressing HIV-1 carrying fluorescently labeled Gag and a labeled F-actin-binding peptide were imaged by live-cell total internal reflection fluorescence microscopy (TIR-FM). Computational analysis of image series did not reveal characteristic patterns of F-actin in the vicinity of viral budding sites. Furthermore, no transient recruitment of F-actin during bud formation was detected by monitoring fluorescence intensity changes at nascent HIV-1 assembly sites. The chosen approach allowed us to measure the effect of F-actin-interfering drugs on the assembly of individual virions in parallel with monitoring changes in the F-actin network of the respective cell. Treatment of cells with latrunculin did not affect the efficiency and dynamics of Gag assembly under conditions resulting in the disruption of F-actin filaments. Normal assembly rates were also observed upon transient stabilization of F-actin by short-term treatment with jasplakinolide. Taken together, these findings indicate that actin filament dynamics are dispensable for HIV-1 Gag assembly at the plasma membrane of HeLa cells. Importance: HIV-1 particles assemble at the plasma membrane of virus-producing cells. This membrane is lined by a dense network of actin filaments that might either present a physical obstacle to the formation of virus particles or generate force promoting the assembly process. Drug-mediated interference with the actin cytoskeleton showed different results for the formation of retroviral particles in different studies, likely due to general effects on the cell upon prolonged drug treatment. Here, we characterized the effect of actin-interfering compounds on the HIV-1 assembly process by direct observation of virus formation in live cells, which allowed us to measure assembly rate constants directly upon drug addition. Virus assembly proceeded with normal rates when actin filaments were either disrupted or stabilized. Taken together with the absence of characteristic actin filament patterns at viral budding sites in our analyses, this indicates that the actin network is dispensable for HIV-1 assembly.

摘要

人类免疫缺陷病毒 1 型(HIV-1)颗粒在质膜处组装,质膜由丝状肌动蛋白(F-actin)的密集网络构成。在 HIV-1 病毒粒子中检测到大量肌动蛋白,据推测是通过与病毒多蛋白 Gag 的核衣壳域相互作用而掺入的。使用肌动蛋白干扰药物研究 F-actin 在 HIV-1 颗粒形成中的作用并未产生一致的结果。通过冷冻电子断层扫描和原子力显微镜检测到指向 HIV-1 出芽起始位点的丝状结构,促使我们通过活细胞显微镜重新研究 F-actin 在 HIV-1 组装中的作用。共表达带有荧光标记的 Gag 和标记的 F-actin 结合肽的 HeLa 细胞通过活细胞全内反射荧光显微镜(TIR-FM)进行成像。对图像系列的计算分析未在病毒出芽部位附近显示出 F-actin 的特征模式。此外,通过监测新生 HIV-1 组装部位的荧光强度变化,未检测到在芽形成过程中 F-actin 的瞬时募集。所选择的方法使我们能够在平行监测各自细胞的 F-actin 网络变化的同时,测量 F-actin 干扰药物对单个病毒粒子组装的影响。在导致 F-actin 丝断裂的条件下,用 latrunculin 处理细胞不会影响 Gag 组装的效率和动力学。用 jasplakinolide 短期处理短暂稳定 F-actin 也观察到正常的组装速率。总之,这些发现表明肌动蛋白丝动力学对于 HeLa 细胞质膜上的 HIV-1 Gag 组装是可有可无的。重要性:HIV-1 颗粒在产生病毒的细胞的质膜处组装。该膜由肌动蛋白丝的密集网络构成,这些丝可能既构成病毒颗粒形成的物理障碍,也产生促进组装过程的力。药物介导的对肌动蛋白细胞骨架的干扰在不同的研究中对逆转录病毒颗粒的形成产生了不同的结果,这可能是由于长期药物处理对细胞的一般影响。在这里,我们通过直接观察活细胞中的病毒形成,对肌动蛋白干扰化合物对 HIV-1 组装过程的影响进行了特征描述,这使我们能够在添加药物时直接测量组装速率常数。当肌动蛋白丝被破坏或稳定时,病毒组装以正常速率进行。与我们的分析中病毒出芽部位不存在特征性肌动蛋白丝模式相结合,这表明肌动蛋白网络对于 HIV-1 组装是可有可无的。

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