Open AccessA Clinical-Stage Cysteine Protease Inhibitor blocks SARS-CoV-2 Infection of Human and Monkey Cells
Author(s) -
Drake M. Mellott,
Chien Te K. Tseng,
Aleksandra Drelich,
Pavla Fajtová,
Balachandra Chenna,
Demetrios H. Kostomiris,
Jason C. Hsu,
Jiyun Zhu,
Zane W. Taylor,
Klaudia I. Kocurek,
Vivian Tat,
Ardala Katzfuss,
Linfeng Li,
Miriam A. Giardini,
Danielle Skinner,
Ken Hirata,
Michael C. Yoon,
Sungjun Beck,
Aaron F. Carlin,
Alex E. Clark,
Laura Beretta,
Daniel C. Maneval,
Vivian Hook,
Felix W. Frueh,
Brett L. Hurst,
Hong Wang,
Frank M. Raushel,
Anthony J. O’Donoghue,
Jair L. Siqueira-Neto,
Thomas D. Meek,
James H. McKerrow
Publication year - 2021
Publication title -
acs chemical biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.899
H-Index - 111
eISSN - 1554-8937
pISSN - 1554-8929
DOI - 10.1021/acschembio.0c00875
Subject(s) - vero cell , proteases , cathepsin l , infectivity , cathepsin b , cysteine protease , cathepsin , cell culture , protease , cysteine , biology , microbiology and biotechnology , cysteine proteinase inhibitors , virology , biochemistry , enzyme , virus , programmed cell death , caspase , apoptosis , genetics
Host-cell cysteine proteases play an essential role in the processing of the viral spike protein of SARS coronaviruses. K777, an irreversible, covalent inactivator of cysteine proteases that has recently completed phase 1 clinical trials, reduced SARS-CoV-2 viral infectivity in several host cells: Vero E6 (EC 50 < 74 nM), HeLa/ACE2 (4 nM), Caco-2 (EC 90 = 4.3 μM), and A549/ACE2 (<80 nM). Infectivity of Calu-3 cells depended on the cell line assayed. If Calu-3/2B4 was used, EC 50 was 7 nM, but in the ATCC Calu-3 cell line without ACE2 enrichment, EC 50 was >10 μM. There was no toxicity to any of the host cell lines at 10-100 μM K777 concentration. Kinetic analysis confirmed that K777 was a potent inhibitor of human cathepsin L, whereas no inhibition of the SARS-CoV-2 cysteine proteases (papain-like and 3CL-like protease) was observed. Treatment of Vero E6 cells with a propargyl derivative of K777 as an activity-based probe identified human cathepsin B and cathepsin L as the intracellular targets of this molecule in both infected and uninfected Vero E6 cells. However, cleavage of the SARS-CoV-2 spike protein was only carried out by cathepsin L. This cleavage was blocked by K777 and occurred in the S1 domain of the SARS-CoV-2 spike protein, a different site from that previously observed for the SARS-CoV-1 spike protein. These data support the hypothesis that the antiviral activity of K777 is mediated through inhibition of the activity of host cathepsin L and subsequent loss of cathepsin L-mediated viral spike protein processing.