Department of Biological Sciences and Bioengineering, Indian Institute of Technology Kanpur, Kanpur, Uttar Pradesh 208016, India.
Infection Biology Unit, German Primate Center, Kellnerweg 4, 37077 Göttingen, Germany; Faculty of Biology and Psychology, Georg-August-University Göttingen, Wilhelmsplatz 1, 37073 Göttingen, Germany.
Cell Rep. 2022 Apr 19;39(3):110694. doi: 10.1016/j.celrep.2022.110694. Epub 2022 Apr 9.
Mutations in the spike protein generated a highly infectious and transmissible D614G variant, which is present in newly evolved fast-spreading variants. The D614G, Alpha, Beta, and Delta spike variants of SARS-CoV-2 appear to expedite membrane fusion process for entry, but the mechanism of spike-mediated fusion is unknown. Here, we reconstituted an in vitro pseudovirus-liposome fusion reaction and report that SARS-CoV-2 wild-type spike is a dynamic Ca sensor, and D614G mutation enhances dynamic calcium sensitivity of spike protein for facilitating membrane fusion. This dynamic calcium sensitivity for fusion is found to be higher in Alpha and Beta variants and highest in Delta spike variant. We find that efficient fusion is dependent on Ca concentration at low pH, and the fusion activity of spike dropped as the Ca level rose beyond physiological levels. Thus, evolved spike variants may control the high fusion probability for entry by increasing Ca sensing ability.
刺突蛋白突变产生了一种高度传染性和高传播性的 D614G 变体，该变体存在于新出现的快速传播变体中。SARS-CoV-2 的 D614G、Alpha、Beta 和 Delta 刺突变体似乎加速了进入的膜融合过程，但刺突介导融合的机制尚不清楚。在这里，我们重建了体外假病毒-脂质体融合反应，并报告 SARS-CoV-2 野生型刺突是一种动态的 Ca 传感器，而 D614G 突变增强了刺突蛋白的动态钙敏感性，从而促进膜融合。我们发现，Alpha 和 Beta 变体中的融合动态钙敏感性更高，而 Delta 刺突变体中的融合动态钙敏感性最高。我们发现，有效的融合依赖于低 pH 下的 Ca 浓度，并且随着 Ca 水平超过生理水平，刺突的融合活性下降。因此，进化的刺突变体可能通过增加 Ca 感应能力来控制进入的高融合概率。
