Porcine epidemic diarrhea virus papain-like protease 2 can be noncompetitively inhibited by 6-thioguanine

Abstract

Porcine epidemic diarrhea virus (PEDV) is a coronavirus (CoV) discovered in the 1970s that infects the intestinal tract of pigs, resulting in diarrhea and vomiting. It can cause extreme dehydration and death in neonatal piglets. In Asia, modified live attenuated vaccines have been used to control PEDV infection in recent years. However, a new strain of PEDV that belongs to genogroup 2a appeared in the USA in 2013 and then quickly spread to Canada and Mexico as well as Asian and European countries. Due to the less effective protective immunity provided by the vaccines against this new strain, it has caused considerable agricultural and economic loss worldwide. The emergence of this new strain increases the importance of understanding PEDV as well as strategies for inhibiting it. Coronaviral proteases, including main proteases and papain-like proteases, are ideal antiviral targets because of their essential roles in viral maturation. Here we provide a first description of the expression, purification and structural characteristics of recombinant PEDV papain-like protease 2, moreover present our finding that 6-thioguanine, a chemotherapeutic drug, in contrast to its competitive inhibition on SARS- and MERS-CoV papain-like proteases, is a noncompetitive inhibitor of PEDV papain-like protease 2.

Computational Determination of Potential Multiprotein Targeting Natural Compounds for Rational Drug Design Against SARS-COV-2

“…Virtual screening of the compounds against of the targets used was done using the AutoDock Vina in PyRx [ 80 ] on Windows 10-supported Dell system (processor: Intel(R) Core(TM) i7-8550U CPU @ 1.80 GHz with a 64-bit operating system, ×64-based processor, a memory of 8.00 GB). First, the docking protocol was validated by docking cocrystallized ligands to the protein keeping the docking parameters default except for the sphere around the binding site, which was set to 15 Å. Validation was also done by comparing the best-ranked compounds conformation relative to the crystallized ligand by root-mean-square deviation (RMSD) [ 81 ].…”

Papain-Like Proteases as Coronaviral Drug Targets: Current Inhibitors, Opportunities, and Limitations

“…It was identified as an allosteric inhibitor of SARS-CoV and a competitive inhibitor of MERS-CoV [ 69 ]. The cysteine protease inhibitor N-Ethylmaleimide (NEM) that covalently modifies the active-site Cys inhibited SARS-CoV, but was a poor inhibitor of MERS-CoV PLpro [ 70 , 71 ].…”

“…Additionally, 6-mercaptopurine (6MP) and 6-thioguanine (6TG) have been widely used in cancer treatment. They are competitive slow-binding inhibitors that form hydrogen bonds with the catalytic triads of SARS-CoV and MERS-CoV PLpro [ 70 , 71 ]. Disulfiram, a drug that has been used in alcohol aversion therapy since 1951, is an irreversible covalent inhibitor for SARS-CoV PLpro (competitive (or mixed)) and MERS-CoV (noncompetitive) [ 72 ].…”

Drawing Comparisons between SARS-CoV-2 and the Animal Coronaviruses

“…In another study, Galanthus nivalis agglutinin and nelfinavir were shown to synergistically exert an antiviral effect on FCoVs in vitro [ 179 ]. The chemotherapeutic drug, 6-thioguanine, was found to noncompetitively inhibit the PEDV papain-like protease 2 [ 180 ]. Interestingly, 3CLpro inhibitor resistant MHV mutants were shown to be attenuated for replication and pathogenesis in mice, revealing a low genetic barrier but high fitness cost of resistance for CoVs [ 181 ].…”