Cell entry mechanisms of SARS-CoV-2

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 117; no. 21; pp. 11727 - 11734
• Main Authors: Shang, Jian, Wan, Yushun, Luo, Chuming, Ye, Gang, Geng, Qibin, Auerbach, Ashley, Li, Fang
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 26.05.2020
• Subjects: ACE2; Affinity; Angiotensin-converting enzyme 2; Binding; Biological Sciences; Cell Line; Coronaviridae; Coronaviruses; COVID-19; Furin; Humans; Immune Evasion; Immunosurveillance; Pandemics; Peptidyl-Dipeptidase A - chemistry; Peptidyl-Dipeptidase A - metabolism; Proprotein convertases; Protein Domains; Receptors; Receptors, Virus - chemistry; Receptors, Virus - metabolism; SARS Virus - chemistry; SARS Virus - immunology; SARS Virus - physiology; Severe acute respiratory syndrome; Severe acute respiratory syndrome coronavirus 2; Spike Glycoprotein, Coronavirus - chemistry; Spike Glycoprotein, Coronavirus - immunology; Spike Glycoprotein, Coronavirus - metabolism; Spike protein; Viral diseases; Virus Activation; Virus Internalization; Viruses; COVID-19; proprotein convertase furin; ACE2 receptor; SARS-CoV-2; SARS-CoV
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.2003138117

A novel severe acute respiratory syndrome (SARS)-like coronavirus (SARS-CoV-2) is causing the global coronavirus disease 2019 (COVID-19) pandemic. Understanding how SARS-CoV-2 enters human cells is a high priority for deciphering its mystery and curbing its spread. A virus surface spike protein mediates SARS-CoV-2 entry into cells. To fulfill its function, SARS-CoV-2 spike binds to its receptor human ACE2 (hACE2) through its receptor-binding domain (RBD) and is proteolytically activated by human proteases. Here we investigated receptor binding and protease activation of SARS-CoV-2 spike using biochemical and pseudovirus entry assays. Our findings have identified key cell entry mechanisms of SARS-CoV-2. First, SARS-CoV-2 RBD has higher hACE2 binding affinity than SARS-CoV RBD, supporting efficient cell entry. Second, paradoxically, the hACE2 binding affinity of the entire SARS-CoV-2 spike is comparable to or lower than that of SARS-CoV spike, suggesting that SARS-CoV-2 RBD, albeit more potent, is less exposed than SARS-CoV RBD. Third, unlike SARS-CoV, cell entry of SARS-CoV-2 is preactivated by proprotein convertase furin, reducing its dependence on target cell proteases for entry. The high hACE2 binding affinity of the RBD, furin preactivation of the spike, and hidden RBD in the spike potentially allow SARS-CoV-2 to maintain efficient cell entry while evading immune surveillance. These features may contribute to the wide spread of the virus. Successful intervention strategies must target both the potency of SARS-CoV-2 and its evasiveness.