PDF(Pubmed)
Abstract：
Fusion-associated small transmembrane (FAST) proteins are a diverse family of nonstructural viral proteins. Once expressed on the plasma membrane of infected cells, they drive fusion with neighboring cells, increasing viral spread and pathogenicity. Unlike viral fusogens with tall ectodomains that pull two membranes together through conformational changes, FAST proteins have short fusogenic ectodomains that cannot bridge the intermembrane gap between neighboring cells. One orthoreovirus FAST protein, p14, has been shown to hijack the actin cytoskeleton to drive cell-cell fusion, but the actin adaptor-binding motif identified in p14 is not found in any other FAST protein. Here, we report that an evolutionarily divergent FAST protein, p22 from aquareovirus, also hijacks the actin cytoskeleton but does so through different adaptor proteins, Intersectin-1 and Cdc42, that trigger N-WASP-mediated branched actin assembly. We show that despite using different pathways, the cytoplasmic tail of p22 can replace that of p14 to create a potent chimeric fusogen, suggesting they are modular and play similar functional roles. When we directly couple p22 with the parallel filament nucleator formin instead of the branched actin nucleation promoting factor N-WASP, its ability to drive fusion is maintained, suggesting that localized mechanical pressure on the plasma membrane coupled to a membrane-disruptive ectodomain is sufficient to drive cell-cell fusion. This work points to a common biophysical strategy used by FAST proteins to push rather than pull membranes together to drive fusion, one that may be harnessed by other short fusogens responsible for physiological cell-cell fusion.
摘要：
融合相关的小跨膜(FAST)蛋白是非结构病毒蛋白的多样化家族。一旦在感染细胞的质膜上表达，它们驱动与邻近细胞的融合，增加病毒传播和致病性。与具有高胞外域的病毒融合剂不同，它们通过构象变化将两个膜拉在一起，FAST蛋白具有短的融合胞外域,其不能桥接相邻细胞之间的膜间间隙。一种正切病毒FAST蛋白，p14，已被证明劫持肌动蛋白细胞骨架驱动细胞-细胞融合，但是在p14中鉴定的肌动蛋白衔接子结合基序在任何其他FAST蛋白中都没有发现。这里,我们报道了一种进化上分歧的FAST蛋白，P22来自水病毒，也劫持肌动蛋白细胞骨架，但通过不同的衔接蛋白，Interectin-1和Cdc42，触发N-WASP介导的分支肌动蛋白组装。我们表明，尽管使用了不同的途径，p22的胞质尾可以取代p14的胞质尾，产生一种有效的嵌合融合蛋白，这表明它们是模块化的，并且扮演着类似的功能角色。当我们直接将p22与平行丝成核剂形式的形式而不是分支肌动蛋白成核促进因子N-WASP偶联时，它驱动融合的能力得以保持，表明与膜破坏性胞外域耦合的质膜上的局部机械压力足以驱动细胞-细胞融合。这项工作指出了FAST蛋白使用的一种常见的生物物理策略来推动而不是将膜拉在一起以驱动融合，一种可以被负责生理细胞-细胞融合的其他短融合剂利用。
