Cervantes Marcos, Hess Tobin, Morbioli Giorgio G, Sengar Anjali, Kasson Peter M
Departments of Molecular Physiology and Biomedical Engineering, University of Virginia Charlottesville VA 22908 USA
Science for Life Laboratory and Department of Molecular and Cellular Biology, Uppsala University Uppsala SE 75123 USA.
Chem Sci. 2023 Jun 5;14(25):6997-7004. doi: 10.1039/d2sc06967a. eCollection 2023 Jun 28.
The SARS-CoV-2 coronavirus infects human cells the ACE2 receptor. Structural evidence suggests that ACE2 may not just serve as an attachment factor but also conformationally activate the SARS-CoV-2 spike protein for membrane fusion. Here, we test that hypothesis directly, using DNA-lipid tethering as a synthetic attachment factor in place of ACE2. We find that SARS-CoV-2 pseudovirus and virus-like particles are capable of membrane fusion without ACE2 if activated with an appropriate protease. Thus, ACE2 is not biochemically required for SARS-CoV-2 membrane fusion. However, addition of soluble ACE2 speeds up the fusion reaction. On a per-spike level, ACE2 appears to promote activation for fusion and then subsequent inactivation if an appropriate protease is not present. Kinetic analysis suggests at least two rate-limiting steps for SARS-CoV-2 membrane fusion, one of which is ACE2 dependent and one of which is not. Since ACE2 serves as a high-affinity attachment factor on human cells, the possibility to replace it with other factors implies a flatter fitness landscape for host adaptation by SARS-CoV-2 and future related coronaviruses.
严重急性呼吸综合征冠状病毒2（SARS-CoV-2）感染人类细胞的血管紧张素转换酶2（ACE2）受体。结构证据表明，ACE2可能不仅作为一种附着因子，还能通过构象激活SARS-CoV-2刺突蛋白以实现膜融合。在此，我们直接验证这一假设，使用DNA-脂质连接作为一种合成附着因子来替代ACE2。我们发现，如果用适当的蛋白酶激活，SARS-CoV-2假病毒和病毒样颗粒在没有ACE2的情况下也能够进行膜融合。因此，SARS-CoV-2膜融合在生化层面上并不需要ACE2。然而，添加可溶性ACE2会加速融合反应。在每个刺突水平上，如果不存在适当的蛋白酶，ACE2似乎会促进融合激活，然后引发后续失活。动力学分析表明，SARS-CoV-2膜融合至少有两个限速步骤，其中一个依赖于ACE2，另一个则不依赖。由于ACE2在人类细胞上作为一种高亲和力附着因子，用其他因子替代它的可能性意味着SARS-CoV-2及未来相关冠状病毒在宿主适应性方面具有更平坦的适应度景观。
