EV713C protease cleaves host anti-viral factor OAS3 and enhances virus replication

The global spread of enteroviruses(EVs)has become more frequent,severe and life-threatening.Intereron(IFN)I has been proved to control EVs by regulating IFN-stimulated genes(ISG)expression.20-50-oligoadenylate synthetases 3(OAS3)is an important ISG in the OAS/RNase L antiviral system.The relationship between OAS3 and EVs is still unclear.Here,we reveal that OAS3,superior to OAS1 and OAS2,significantly inhibited EV71 replication in vitro.However,EV71 utilized autologous 3C protease(3C^(pro))to cleave intracellular OAS3 and enhance viral replication.Rupintrivir,a human rhinovirus 3C protease inhibitor,completely abolished the cleavage of EV713C^(pro)on OAS3.And the proteolytically deficient mutants H40G,E71A,and C147G of EV713C^(pro)also lost the ability of OAS3 cleavage.Mechanistically,the Q982-G983 motif in C-terminal of OAS3 was identified as a crucial 3C^(pro)cutting site.Further investigation indicated that OAS3 inhibited not only EV71 but also Coxsackievirus B3(CVB3),Coxsackievirus A16(CA16),Enterovirus D68(EVD68),and Coxsackievirus A6(CA6)subtypes.Notably,unlike other four subtypes,CA163C^(pro)could not cleave OAS3.Two key amino acids variation Ile36 and Val86 in CA163C^(pro)might result in weak and delayed virus replication of CA16 because of failure of OAS and 3AB cleavage.Our works elucidate the broad anti-EVs function of OAS3,and illuminate a novel mechanism by which EV71 use 3C^(pro)to escape the antiviral effect of OAS3.These findings can be an important entry point for developing novel therapeutic strategies for multiple EVs infection.

TAR DNA-Binding Protein 43 is Cleaved by the Protease 3C of Enterovirus A71

Enterovirus A71(EV-A71)is one of the etiological pathogens leading to hand,foot,and mouth disease(HFMD),which can cause severe neurological complications.The neuropathogenesis of EV-A71 infection is not well understood.The mislocalization and aggregation of TAR DNA-binding protein 43(TDP-43)is the pathological hallmark of amyotrophic lateral sclerosis(ALS).However,whether TDP-43 was impacted by EV-A71 infection is unknown.This study demonstrated that TDP-43 was cleaved during EV-A71 infection.The cleavage of TDP-43 requires EV-A71 replication rather than the activated caspases due to viral infection.TDP-43 is cleaved by viral protease 3 C between the residues 331 Q and332 S,while mutated TDP-43(Q331 A)was not cleaved.In addition,mutated 3 C which lacks the protease activity failed to induce TDP-43 cleavage.We also found that TDP-43 was translocated from the nucleus to the cytoplasm,and the mislocalization of TDP-43 was induced by viral protease 2 A rather than 3 C.Taken together,we demonstrated that TDP-43 was cleaved by viral protease and translocated to the cytoplasm during EV-A71 infection,implicating the possible involvement of TDP-43 in the pathogenesis of EV-A71 infection.

Structure of the HRV-C 3C-Rupintrivir Complex Provides New Insights for Inhibitor Design

Human rhinoviruses(HRVs)are the predominant infectious agents for the common cold worldwide.The HRV-C species cause severe illnesses in children and are closely related to acute exacerbations of asthma.3C protease,a highly conserved enzyme,cleaves the viral polyprotein during replication and assists the virus in escaping the host immune system.These key roles make 3C protease an important drug target.A few structures of 3Cs complexed with an irreversible inhibitor rupintrivir have been determined.These structures shed light on the determinants of drug specificity.Here we describe the structures of HRV-C153C in free and inhibitor-bound forms.The volume-decreased S1'subsite and half-closed S2 subsite,which were thought to be unique features of enterovirus A 3C proteases,appear in the HRV-C 3C protease.Rupintrivir assumes an“intermediate”conformation in the complex,which might open up additional avenues for the design of potent antiviral inhibitors.Analysis of the features of the three-dimensional structures and the amino acid sequences of 3C proteases suggest new applications for existing drugs.

Potential medicinal plants involved in inhibiting 3CL^(pro) activity:A practical alternate approach to combating COVID-19

At present,a variety of vaccines have been approved,and existing antiviral drugs are being tested to find an effective treatment for coronavirus disease 2019(COVID-19).However,no standardized treatment has yet been approved by the World Health Organization.The virally encoded chymotrypsin-like protease(3CL^(pro))from severe acute respiratory syndrome coronavirus 2(SARS-CoV-2),which facilitates the replication of SARS-CoV in the host cells,is one potential pharmacological target for the development of antiSARS drugs.Online search engines,such as Web of Science,Google Scholar,Scopus and PubMed,were used to retrieve data on the traditional uses of medicinal plants and their inhibitory effects against the SARS-CoV 3CL^(pro).Various pure compounds,including polyphenols,terpenoids,chalcones,alkaloids,biflavonoids,flavanones,anthraquinones and glycosides,have shown potent inhibition of SARS-CoV-2 3CL^(pro) activity with 50% inhibitory concentration(IC_(50))values ranging from 2-44μg/mL.Interestingly,most of these active compounds,including xanthoangelol E(isolated from Angelica keiskei),dieckol 1(isolated from Ecklonia cava),amentoflavone(isolated from Torreya nucifera),celastrol,pristimerin,tingenone and iguesterin(isolated from Tripterygium regelii),tannic acid(isolated from Camellia sinensis),and theaflavin-3,3’-digallate,3-isotheaflav1in-3 gallate and dihydrotanshinone I(isolated from Salvia miltiorrhiza),had IC_(50)values of less than 15μg/mL.Kinetic mechanistic studies of several active compounds revealed that their mode of inhibition was dose-dependent and competitive,with K_(i)values ranging from 2.4-43.8μmol/L.Given the significance of plant-based compounds and the many promising results obtained,there is still need to explore the phytochemical and mechanistic potentials of plants and their products.These medicinal plants could serve as an effective inexpensive nutraceutical for the general public to help manage COVID-19.