Furin cleavage of SARS-CoV-2 Spike promotes but is not essential for infection and cell-cell fusion

• Published in: PLoS pathogens Vol. 17; no. 1; p. e1009246
• Main Authors: Papa, Guido, Mallery, Donna L, Albecka, Anna, Welch, Lawrence G, Cattin-Ortolá, Jérôme, Luptak, Jakub, Paul, David, McMahon, Harvey T, Goodfellow, Ian G, Carter, Andrew, Munro, Sean, James, Leo C
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 25.01.2021; Public Library of Science (PLoS)
• Subjects: Amino acids; Animals; Biology and life sciences; Cell activation; Cell Fusion; Cell membranes; Chlorocebus aethiops; Cleavage; Coronaviruses; COVID-19; CRISPR-Cas Systems; Disease transmission; Furin; Furin - genetics; Gene Knockout Techniques; Genetic aspects; HEK293 Cells; Host-virus relationships; Humans; Hydrophobicity; Infections; Kinetics; Medicine and health sciences; Membrane fusion; Mutation; Pandemics; Pathogenesis; Peptides; Physiological aspects; Proteases; Protein Structure, Tertiary; Proteins; Proteolysis; Research and analysis methods; SARS-CoV-2; Serine Endopeptidases; Severe acute respiratory syndrome; Severe acute respiratory syndrome coronavirus 2; Spike Glycoprotein, Coronavirus - chemistry; Statistical analysis; Structure; Syncytia; Vero Cells; Viral diseases; Viral proteins; Virus Internalization; Virus research; Viruses; United Kingdom
• ISSN: 1553-7374; 1553-7366; 1553-7374
• DOI: 10.1371/journal.ppat.1009246

Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2) infects cells by binding to the host cell receptor ACE2 and undergoing virus-host membrane fusion. Fusion is triggered by the protease TMPRSS2, which processes the viral Spike (S) protein to reveal the fusion peptide. SARS-CoV-2 has evolved a multibasic site at the S1-S2 boundary, which is thought to be cleaved by furin in order to prime S protein for TMPRSS2 processing. Here we show that CRISPR-Cas9 knockout of furin reduces, but does not prevent, the production of infectious SARS-CoV-2 virus. Comparing S processing in furin knockout cells to multibasic site mutants reveals that while loss of furin substantially reduces S1-S2 cleavage it does not prevent it. SARS-CoV-2 S protein also mediates cell-cell fusion, potentially allowing virus to spread virion-independently. We show that loss of furin in either donor or acceptor cells reduces, but does not prevent, TMPRSS2-dependent cell-cell fusion, unlike mutation of the multibasic site that completely prevents syncytia formation. Our results show that while furin promotes both SARS-CoV-2 infectivity and cell-cell spread it is not essential, suggesting furin inhibitors may reduce but not abolish viral spread.