RAPID: Molecular Insights into the SARS-CoV-2 Spike Protein Activation via a Novel Interaction with a Human Cell Surface Target Protein

严重急性呼吸综合征冠状病毒2 （SARS-CoV-2）是一种包膜单链RNA病毒，属于冠状病毒科sarbecvirus亚属。冠状病毒科的成员包括SARS-CoV和中东呼吸综合征冠状病毒（MERS-CoV），它们是导致普通感冒和其他新出现的严重呼吸道疾病的人类病原体。SARS-CoV和SARS-CoV-2通过与血管紧张素转换酶2 （ACE2）受体结合而附着在宿主细胞上。冠状病毒刺突蛋白的受体结合域（RBD）与ACE2受体结合，促进了病毒的进入。然而，SARS-CoV-2靶向的是与其他器官中ACE2表达相对较低的肺II型肺泡细胞。因此，已经确定了其他共同受体，它们是病毒的目标，可能为病毒提供了另一种进入点。虽然与SARS-CoV相比，SARS-CoV-2感染的器官较少，但其机制仍不确定。该研究项目将为人类细胞表面蛋白在SARS-CoV-2进入和复制中的新作用提供结构见解。迫切需要深入了解病毒进入细胞的第二个可能入口点。此外，该项目还包括面向代表性不足的少数民族，特别是年轻人口的教育外展部分，这是一个非常重要的次受欢迎群体，他们可能低估了SARS的影响。该研究项目将使用迄今为止在美国安装的第一台300千伏低温原子分辨率显微镜（ARM）来确定人类细胞表面蛋白与SARS-CoV-2刺突蛋白之间新型相互作用的近原子分辨率结构。生化分析将进一步验证结构发现。因此，从美国的一种新型冷冻电子显微镜上获得的数据中，对病毒发病机制的重要机制见解将迅速发表，该显微镜已经帮助从包括欧洲和亚洲在内的几个海外实验室对许多生物过程进行了近原子分辨率的了解。通过确定SARS-CoV-2与SARS-CoV相比如何感染更少的器官的机制见解，本研究项目获得的发现可以解释SARS-CoV-2与SARS-CoV相比死亡率较低的原因。总的来说，对SARS-CoV-2刺突蛋白与人类细胞表面蛋白相互作用机制的结构见解将：(i)进一步了解COVID-19如何传播，（ii）阐明SARS-CoV-2与SARS-CoV的一些关键差异，以及（iii）为SARS-CoV-2的高传播性提供机制见解。这样的病毒-宿主研究将有助于更广泛地了解病毒的发病机制。该RAPID奖由分子和细胞生物科学部的细胞动力学和功能项目获得，资金来自《冠状病毒援助、救济和经济安全法案》。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an enveloped, single-stranded RNA virus that belongs to the subgenus sarbecvirus of Coronaviridae. Members of the Coronaviridae family include the SARS-CoV and the Middle East respiratory syndrome coronavirus (MERS-CoV), which are the responsible human pathogens for the common cold and other emerging severe respiratory conditions. SARS-CoV and SARS-CoV-2 attach to the host cells by binding to the angiotensin converting enzyme 2 (ACE2) receptor. Viral entry is facilitated by the binding of the receptor binding domain (RBD) of the coronavirus spike protein to the ACE2 receptor. However, SARS-CoV-2 targets type II alveolar cells in the lung that have relatively low ACE2 expression compared to ACE2 expression in other organs. Thus, other co-receptors have been identified that are targeted by the virus and which likely provide for an alternative entry point for the virus. While SARS-CoV-2 infects fewer organs compared to SARS-CoV, the mechanisms remain inconclusive. This research project will provide structural insights into the novel role of a human cell surface protein in SARS-CoV-2 entry and replication. There is an urgent need for gaining insight into this possible second entry point for the virus into cells. Additionally, this project includes an educational outreach component geared towards the underrepresented minorities and in particular the younger population, an incredibly important sub popular who might be underestimating the impact of SARS.This research project will use the first 300 kV cryo Atomic Resolution Microscope (ARM), installed to date in the US, to determine the near atomic resolution structures of the novel interaction between a human cell surface protein and the SARS-CoV-2 spike protein. Biochemical assays will additionally validate the structural findings. Thus, significant mechanistic insights into viral pathogenesis will be published rapidly from data obtained on a new cryo-electron microscope in the US that has aided near atomic resolution insights into many biological processes from several laboratories overseas, including from Europe and Asia. By determining the mechanistic insights into how SARS-CoV-2 infects fewer organs compared to SARS-CoV, the findings obtained in this research project could explain the lower mortality of SARS-CoV-2 compared to SARS-CoV. Collectively, the structural insights into the mechanism of the interaction of the SARS-CoV-2 spike protein with a human cell surface protein will: (i) further the understanding on how COVID-19 is spreading, (ii) shed light onto some of the key differences of SARS-CoV-2 versus SARS-CoV, and (iii) provide mechanistic insights into the higher transmissibility of SARS-CoV-2. Such virus-host study will contribute to a broader understanding of viral pathogenesis.This RAPID award is made by the Cellular Dynamics and Functionl Program in the Division of Molecular and Cellular Biosciences, using funds from the Coronavirus Aid, Relief, and Economic Security (CARES) Act.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.