Dahmani Ismail, Ludwig Kai, Chiantia Salvatore
University of Potsdam, Institute of Biochemistry and Biology, Karl-Liebknecht-Str. 24-25, Potsdam 14476, Germany.
Forschungszentrum für Elektronenmikroskopie und Gerätezentrum BioSupraMol, Institut für Chemie und Biochemie, Freie Universität Berlin, Fabeckstr. 36a, Berlin 14195, Germany.
Biosci Rep. 2019 Aug 5;39(8). doi: 10.1042/BSR20191024. Print 2019 Aug 30.
The matrix protein M1 of the Influenza A virus (IAV) is supposed to mediate viral assembly and budding at the plasma membrane (PM) of infected cells. In order for a new viral particle to form, the PM lipid bilayer has to bend into a vesicle toward the extracellular side. Studies in cellular models have proposed that different viral proteins might be responsible for inducing membrane curvature in this context (including M1), but a clear consensus has not been reached. In the present study, we use a combination of fluorescence microscopy, cryogenic transmission electron microscopy (cryo-TEM), cryo-electron tomography (cryo-ET) and scanning fluorescence correlation spectroscopy (sFCS) to investigate M1-induced membrane deformation in biophysical models of the PM. Our results indicate that M1 is indeed able to cause membrane curvature in lipid bilayers containing negatively charged lipids, in the absence of other viral components. Furthermore, we prove that protein binding is not sufficient to induce membrane restructuring. Rather, it appears that stable M1-M1 interactions and multimer formation are required in order to alter the bilayer three-dimensional structure, through the formation of a protein scaffold. Finally, our results suggest that, in a physiological context, M1-induced membrane deformation might be modulated by the initial bilayer curvature and the lateral organization of membrane components (i.e. the presence of lipid domains).
甲型流感病毒（IAV）的基质蛋白M1被认为在受感染细胞的质膜（PM）上介导病毒组装和出芽。为了形成新的病毒颗粒，质膜脂质双层必须向细胞外侧弯曲成囊泡。细胞模型研究表明，在这种情况下，不同的病毒蛋白（包括M1）可能负责诱导膜曲率，但尚未达成明确的共识。在本研究中，我们结合使用荧光显微镜、低温透射电子显微镜（cryo-TEM）、低温电子断层扫描（cryo-ET）和扫描荧光相关光谱（sFCS），来研究PM生物物理模型中M1诱导的膜变形。我们的结果表明，在没有其他病毒成分的情况下，M1确实能够在含有带负电荷脂质的脂质双层中引起膜曲率。此外，我们证明蛋白质结合不足以诱导膜重构。相反，似乎需要稳定的M1-M1相互作用和多聚体形成，以便通过形成蛋白质支架来改变双层三维结构。最后，我们的结果表明，在生理环境中，M1诱导的膜变形可能受初始双层曲率和膜成分的侧向组织（即脂质结构域的存在）调节。
