Strauss Joshua D, Hammonds Jason E, Yi Hong, Ding Lingmei, Spearman Paul, Wright Elizabeth R
Department of Pediatrics, Emory University School of Medicine, and Children's Healthcare of Atlanta, Atlanta, Georgia, USA.
Robert P. Apkarian Integrated Electron Microscopy Core, Emory University, Atlanta, Georgia, USA.
J Virol. 2015 Nov 18;90(3):1507-21. doi: 10.1128/JVI.01880-15. Print 2016 Feb 1.
Tetherin (BST2, CD317, or HM1.24) is a host cellular restriction factor that prevents the release of enveloped viruses by mechanically linking virions to the plasma membrane. The precise arrangement of tetherin molecules at the plasma membrane site of HIV-1 assembly, budding, and restriction is not well understood. To gain insight into the biophysical mechanism underlying tetherin-mediated restriction of HIV-1, we utilized cryo-electron tomography (cryo-ET) to directly visualize HIV-1 virus-like particles (VLPs) and virions tethered to human cells in three dimensions (3D). Rod-like densities that we refer to as tethers were seen connecting HIV-1 virions to each other and to the plasma membrane. Native immunogold labeling showed tetherin molecules located on HIV-1 VLPs and virions in positions similar to those of the densities observed by cryo-ET. The location of the tethers with respect to the ordered immature Gag lattice or mature conical core was random. However, tethers were not uniformly distributed on the viral membrane but rather formed clusters at sites of contact with the cell or other virions. Chains of tethered HIV-1 virions often were arranged in a linear fashion, primarily as single chains and, to a lesser degree, as branched chains. Distance measurements support the extended tetherin model, in which the coiled-coil ectodomains are oriented perpendicular with respect to the viral and plasma membranes.
Tetherin is a cellular factor that restricts HIV-1 release by directly cross-linking the virus to the host cell plasma membrane. We used cryo-electron tomography to visualize HIV-1 tethered to human cells in 3D. We determined that tetherin-restricted HIV-1 virions were physically connected to each other or to the plasma membrane by filamentous tethers that resembled rods ∼15 nm in length, which is consistent with the extended tetherin model. In addition, we found the position of the tethers to be arbitrary relative to the ordered immature Gag lattice or the mature conical cores. However, when present as multiple copies, the tethers clustered at the interface between virions. Tethered HIV-1 virions were arranged in a linear fashion, with the majority as single chains. This study advances our understanding of tetherin-mediated HIV-1 restriction by defining the spatial arrangement and orientation of tetherin molecules at sites of HIV-1 restriction.
束缚素（BST2、CD317或HM1.24）是一种宿主细胞限制因子，它通过将病毒粒子机械连接到质膜上来阻止包膜病毒的释放。束缚素分子在HIV-1组装、出芽和限制的质膜部位的精确排列尚不清楚。为了深入了解束缚素介导的HIV-1限制的生物物理机制，我们利用冷冻电子断层扫描（cryo-ET）在三维空间（3D）中直接观察与人类细胞相连的HIV-1病毒样颗粒（VLP）和病毒粒子。我们看到将HIV-1病毒粒子相互连接并连接到质膜上的杆状密度，我们将其称为系链。天然免疫金标记显示束缚素分子位于HIV-1 VLP和病毒粒子上，其位置与cryo-ET观察到的密度位置相似。系链相对于有序的未成熟Gag晶格或成熟的锥形核心的位置是随机的。然而，系链并非均匀分布在病毒膜上，而是在与细胞或其他病毒粒子接触的部位形成簇。相连的HIV-1病毒粒子链通常呈线性排列，主要为单链，较少为分支链。距离测量支持延伸的束缚素模型，其中卷曲螺旋胞外结构域相对于病毒膜和质膜垂直定向。
束缚素是一种细胞因子，通过将病毒直接交联到宿主细胞质膜上来限制HIV-1的释放。我们使用冷冻电子断层扫描在三维空间中观察与人类细胞相连的HIV-1。我们确定，受束缚素限制的HIV-1病毒粒子通过类似于长度约为15 nm的杆状丝状系链彼此物理连接或连接到质膜上，这与延伸的束缚素模型一致。此外，我们发现系链相对于有序的未成熟Gag晶格或成熟的锥形核心的位置是任意的。然而，当以多个拷贝存在时，系链聚集在病毒粒子之间的界面处。相连的HIV-1病毒粒子呈线性排列，大多数为单链。这项研究通过定义束缚素分子在HIV-1限制部位的空间排列和定向，推进了我们对束缚素介导的HIV-1限制的理解。
