Target specificity of selective bioactive compounds in blocking α-dystroglycan receptor to suppress Lassa virus infection: an in silico approach

Lassa hemorrhagic fever,caused by Lassa mammarenavirus(LASV)infection,accumulates up to 5000 deaths every year.Currently,there is no vaccine available to combat this disease.In this study,a library of 200 bioactive compounds was virtually screened to study their drug-likeness with the capacity to block theα-dystroglycan(α-DG)receptor and prevent LASV influx.Following rigorous absorption,distribution,metabolism,and excretion(ADME)and quantitative structure-activity relationship(QSAR)profiling,molecular docking was conducted with the top ligands against theα-DG receptor.The compounds chrysin,reticuline,and 3-caffeoylshikimic acid emerged as the top three ligands in terms of binding affinity.Post-docking analysis revealed that interactions with Arg76,Asn224,Ser259,and Lys302 amino acid residues of the receptor protein were important for the optimum binding affinity of ligands.Molecular dynamics simulation was performed comprehensively to study the stability of the protein-ligand complexes.In-depth assessment of root-mean-square deviation(RMSD),root mean square fluctuation(RMSF),polar surface area(PSA),B-Factor,radius of gyration(Rg),solvent accessible surface area(SASA),and molecular surface area(MolSA)values of the protein-ligand complexes affirmed that the candidates with the best binding affinity formed the most stable protein-ligand complexes.To authenticate the potentialities of the ligands as target-specific drugs,an in vivo study is underway in real time as the continuation of the research.

Identification of residues in Lassa virus glycoprotein 1 involved in receptor switch

Lassa virus(LASV)is an enveloped,negative-sense RNA virus that causes Lassa hemorrhagic fever.Successful entry of LASV requires the viral glycoprotein 1(GP1)to undergo a receptor switch from its primary receptor alpha-dystroglycan(α-DG)to its endosomal receptor lysosome-associated membrane protein 1(LAMP1).A conserved histidine triad in LASV GP1 has been reported to be responsible for receptor switch.To test the hypothesis that other non-conserved residues also contribute to receptor switch,we constructed a series of mutant LASV GP1 proteins and tested them for binding to LAMP1.Four residues,L84,K88,L107,and H170,were identified as critical for receptor switch.Substituting any of the four residues with the corresponding lymphocytic choriomeningitis virus(LCMV)residue(L84 N,K88E,L10F,and H170S)reduced the binding affinity of LASV GP1 for LAMP1.Moreover,all mutations caused decreases in glycoprotein precursor(GPC)-mediated membrane fusion at both pH 4.5 and 5.2.The infectivity of pseudotyped viruses bearing either GPCL84N or GPCK88E decreased sharply in multiple cell types,while L107F and H170S had only mild effects on infectivity.Using biolayer light interferometry assay,we found that all four mutants had decreased binding affinity to LAMP1,in the order of binding affinity being L84 N>L107F>K88E>H170S.The four amino acid loci identified for the first time in this study have important reference significance for the in-depth investigation of the mechanism of receptor switching and immune escape of LASV occurrence and the development of reserve anti-LASV infection drugs.

Deletion of the first glycosylation site promotes Lassa virus glycoprotein-mediated membrane fusion

The Lassa virus(LASV)is endemic in West Africa and causes severe hemorrhagic Lassa fever in humans.The glycoprotein complex(GPC)of LASV is highly glycosylation-modified,with 11 N-glycosylation sites.All 11 N-linked glycan chains play critical roles in GPC cleavage,folding,receptor binding,membrane fusion,and immune evasion.In this study,we focused on the first glycosylation site because its deletion mutant(N79Q)results in an unexpected enhanced membrane fusion,whereas it exerts little effect on GPC expression,cleavage,and receptor binding.Meanwhile,the pseudotype virus bearing GPC_(N79Q)was more sensitive to the neutralizing antibody 37.7H and was attenuated in virulence.Exploring the biological functions of the key glycosylation site on LASV GPC will help elucidate the mechanism of LASV infection and provide strategies for the development of attenuated vaccines against LASV infection.

广谱沙粒病毒抑制剂的3D-QSAR分析

沙粒病毒(Arenaviruses)遍布全球,其中的拉沙热病毒可引起致命的拉沙热.通过应用比较分子场分析(CoMFA)和比较相似性指数分析法(CoMSIA)对47个广谱沙粒病毒抑制剂进行了三维定量构效关系(3D-QSAR)分析.使用立体场、静电场、疏水场和氢键受体场组合获得最优模型CoMSIA的统计结果为Q2=0.518,R2ncv=0.972,R2pre=0.911,说明该模型的可靠性和较好预测能力.此外,模型等势线图直观地解释了分子结构与其活性的关系,为进一步设计新型高效的沙粒病毒抑制剂提供了理论依据.

Characterizing the Lassa Virus Envelope Glycoprotein Membrane Proximal External Region for Its Role in Fusogenicity

The membrane-proximal external region(MPER)of Lassa virus(LASV)glycoprotein complex(GPC)is critical in modulating its functionality.Till now,the high-resolution structure of the intact GPC,including MPER is not available.In this study,we used alanine substitution to scan all 16 residues located in LASV MPER.Western blotting and quantification fusion assay showed that the residues located at the C terminus of the HR2(M414 and L415)and N terminus of the MPER(K417 and Y419)are critical for GPC-mediated membrane fusion function.Furthermore,cell surface biotinylation experiments revealed that M414 A,K417 A and Y419 A expressed similar levels as WT,whereas L415 A mutant led to a reduction of mature GPC on the cell surface.Moreover,substitution of these residues with the similar residue such as M414 L,L415 I,K417 R and Y419 F would partly compensate the loss of the fusion activity caused by the alanine mutant in these sites.Results from this study showed that several key residues in the MPER region are indispensable to promote the conformational changes that drive fusion events and shed light on the structure analysis of LASV GPC and anti-LASV therapeutics.

Effects of N-Linked Glycan on Lassa Virus Envelope Glycoprotein Cleavage,Infectivity,and Immune Response

Lassa virus(LASV)belongs to the Mammarenavirus genus(family Arenaviridae)and causes severe hemorrhagic fever in humans.The glycoprotein complex(GPC)contains eleven N-linked glycans that play essential roles in GPC functionalities such as cleavage,transport,receptor recognition,epitope shielding,and immune response.We used three mutagenesis strategies(asparagine to glutamine,asparagine to alanine,and serine/tyrosine to alanine mutants)to abolish individual glycan chain on GPC and found that all the three strategies led to cleavage inefficiency on the 2nd(N89),5th(N119),or 8th(N365)glycosylation motif.To evaluate N to Q mutagenesis for further research,it was found that deletion of the 2nd(N89Q)or 8th(N365Q)glycan completely inhibited the transduction efficiency of pseudotyped particles.We further investigated the role of individual glycan on GPC-mediated immune response by DNA immunization of mice.Deletion of the individual 1st(N79Q),3rd(N99Q),5th(N119Q),or 6th(N167Q)glycan significantly enhanced the proportion of effector CD4+cells,whereas deletion of the 1st(N79Q),2nd(N89Q),3rd(N99Q),4th(N109Q),5th(N119Q),6th(N167Q),or 9th(N373Q)glycan enhanced the proportion of CD8+effector T cells.Deletion of specific glycan improves the Th1-type immune response,and abolishment of glycan on GPC generally increases the antibody titer to the glycan-deficient GPC.However,the antibodies from either the mutant or WT GPC-immunized mice show little neutralization effect on wild-type LASV.The glycan residues on GPC provide an immune shield for the virus,and thus represent a target for the design and development of a vaccine.