Cathepsin L is a key host cysteine protease utilized by coronaviruses for cell entry and is a promising drug target for novel antivirals against SARS-CoV-2. The marine natural product gallinamide A and several synthetic analogues were identified as potent inhibitors of cathepsin L with IC50 values in the picomolar range. Lead molecules possessed selectivity over other cathepsins and alternative host proteases involved in viral entry. Gallinamide A directly interacted with cathepsin L in cells and, together with two lead analogues, potently inhibited SARS-CoV-2 infection in vitro, with EC50 values in the nanomolar range. Reduced antiviral activity was observed in cells overexpressing transmembrane protease, serine 2 (TMPRSS2); however, a synergistic improvement in antiviral activity was achieved when combined with a TMPRSS2 inhibitor. These data highlight the potential of cathepsin L as a COVID-19 drug target as well as the likely need to inhibit multiple routes of viral entry to achieve efficacy.
- MeSH
- antivirové látky chemická syntéza chemie farmakologie MeSH
- biologické přípravky chemická syntéza chemie farmakologie MeSH
- buňky A549 MeSH
- Cercopithecus aethiops MeSH
- COVID-19 metabolismus MeSH
- farmakoterapie COVID-19 * MeSH
- inhibitory cysteinových proteinas chemická syntéza chemie farmakologie MeSH
- kathepsin L antagonisté a inhibitory metabolismus MeSH
- kationické antimikrobiální peptidy chemická syntéza chemie farmakologie MeSH
- lidé MeSH
- mikrobiální testy citlivosti MeSH
- molekulární konformace MeSH
- proteomika MeSH
- SARS-CoV-2 účinky léků MeSH
- Vero buňky MeSH
- vztah mezi dávkou a účinkem léčiva MeSH
- vztahy mezi strukturou a aktivitou MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, N.I.H., Extramural MeSH
- Názvy látek
- antivirové látky MeSH
- biologické přípravky MeSH
- CTSL protein, human MeSH Prohlížeč
- gallinamide A MeSH Prohlížeč
- inhibitory cysteinových proteinas MeSH
- kathepsin L MeSH
- kationické antimikrobiální peptidy MeSH
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 (EC50< 74 nM), HeLa/ACE2 (4 nM), Caco-2 (EC90 = 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, EC50 was 7 nM, but in the ATCC Calu-3 cell line without ACE2 enrichment, EC50 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.
- MeSH
- antivirové látky farmakologie MeSH
- Cercopithecus aethiops MeSH
- fenylalanin farmakologie MeSH
- glykoprotein S, koronavirus chemie metabolismus MeSH
- inhibitory cysteinových proteinas farmakologie MeSH
- internalizace viru účinky léků MeSH
- kathepsin L antagonisté a inhibitory metabolismus MeSH
- lidé MeSH
- mikrobiální testy citlivosti MeSH
- nádorové buněčné linie MeSH
- piperaziny farmakologie MeSH
- proteinové domény MeSH
- proteolýza MeSH
- SARS-CoV-2 účinky léků MeSH
- tosylové sloučeniny farmakologie MeSH
- Vero buňky MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- Research Support, N.I.H., Extramural MeSH
- Názvy látek
- antivirové látky MeSH
- fenylalanin MeSH
- glykoprotein S, koronavirus MeSH
- inhibitory cysteinových proteinas MeSH
- kathepsin L MeSH
- N-pip-phenylalanine-homophenylalanine-vinyl sulfone phenyl MeSH Prohlížeč
- piperaziny MeSH
- spike protein, SARS-CoV-2 MeSH Prohlížeč
- tosylové sloučeniny MeSH
K777 is a di-peptide analog that contains an electrophilic vinyl-sulfone moiety and is a potent, covalent inactivator of cathepsins. Vero E6, HeLa/ACE2, Caco-2, A549/ACE2, and Calu-3, cells were exposed to SARS-CoV-2, and then treated with K777. K777 reduced viral infectivity with EC50 values of inhibition of viral infection of: 74 nM for Vero E6, <80 nM for A549/ACE2, and 4 nM for HeLa/ACE2 cells. In contrast, Calu-3 and Caco-2 cells had EC50 values in the low micromolar range. No toxicity of K777 was observed for any of the host cells at 10-100 μM inhibitor. K777 did not inhibit activity of the papain-like cysteine protease and 3CL cysteine protease, encoded by SARS-CoV-2 at concentrations of ≤ 100 μM. These results suggested that K777 exerts its potent anti-viral activity by inactivation of mammalian cysteine proteases which are essential to viral infectivity. Using a propargyl derivative of K777 as an activity-based probe, K777 selectively targeted cathepsin B and cathepsin L in Vero E6 cells. However only cathepsin L cleaved the SARS-CoV-2 spike protein and K777 blocked this proteolysis. The site of spike protein cleavage by cathepsin L was in the S1 domain of SARS-CoV-2 , differing from the cleavage site observed in 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 viral spike protein processing.
