MRC Human Immunology Unit, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford OX3 9DS, UK.
"Jožef Stefan" Institute, Jamova c. 39, SI-1000 Ljubljana, Slovenia.
Viruses. 2018 Aug 8;10(8):415. doi: 10.3390/v10080415.
Human Immunodeficiency Virus type-1 (HIV-1) acquires its lipid membrane from the plasma membrane of the infected cell from which it buds out. Previous studies have shown that the HIV-1 envelope is an environment of very low mobility, with the diffusion of incorporated proteins two orders of magnitude slower than in the plasma membrane. One of the reasons for this difference is thought to be the HIV-1 membrane composition that is characterised by a high degree of rigidity and lipid packing, which has, until now, been difficult to assess experimentally. To further refine the model of the molecular mobility on the HIV-1 surface, we herein investigated the relative importance of membrane composition and curvature in simplified model membrane systems, large unilamellar vesicles (LUVs) of different lipid compositions and sizes (0.1⁻1 µm), using super-resolution stimulated emission depletion (STED) microscopy-based fluorescence correlation spectroscopy (STED-FCS). Establishing an approach that is also applicable to measurements of molecule dynamics in virus-sized particles, we found, at least for the 0.1⁻1 µm sized vesicles, that the lipid composition and thus membrane rigidity, but not the curvature, play an important role in the decreased molecular mobility on the vesicles' surface. This observation suggests that the composition of the envelope rather than the particle geometry contributes to the previously described low mobility of proteins on the HIV-1 surface. Our vesicle-based study thus provides further insight into the dynamic properties of the surface of individual HIV-1 particles, as well as paves the methodological way towards better characterisation of the properties and function of viral lipid envelopes in general.
人类免疫缺陷病毒 1 型（HIV-1）从其出芽的感染细胞的质膜获得其脂质膜。先前的研究表明，HIV-1 包膜是一种流动性非常低的环境，其中掺入的蛋白质的扩散速度比质膜慢两个数量级。造成这种差异的原因之一被认为是 HIV-1 膜的组成，其具有高度刚性和脂质堆积，这在实验上一直难以评估。为了进一步完善 HIV-1 表面分子流动性模型，我们在此使用基于超分辨率受激发射损耗（STED）显微镜的荧光相关光谱（STED-FCS），在不同脂质组成和大小（0.1-1 µm）的简化模型膜系统，即大单室脂质体（LUV）中，研究了膜组成和曲率的相对重要性。我们建立了一种也适用于病毒大小颗粒中分子动力学测量的方法，我们发现，至少对于 0.1-1 µm 大小的囊泡，脂质组成，即膜刚性，但不是曲率，在囊泡表面分子流动性降低中起着重要作用。这一观察结果表明，包膜的组成而不是颗粒几何形状导致了 HIV-1 表面上先前描述的蛋白质低流动性。因此，我们的基于囊泡的研究进一步深入了解了单个 HIV-1 颗粒表面的动态特性，并为更好地表征病毒脂质包膜的性质和功能铺平了方法学道路。
