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Residues E53, L55, H59, and G70 of the cellular receptor protein Tva mediate cell binding and entry of the novel subgroup K avian leukosis virus. J Biol Chem 2023; 299:102962. [PMID: 36717079 PMCID: PMC9974445 DOI: 10.1016/j.jbc.2023.102962] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Revised: 01/14/2023] [Accepted: 01/16/2023] [Indexed: 01/30/2023] Open
Abstract
Subgroup K avian leukosis virus (ALV-K) is a novel subgroup of ALV isolated from Chinese native chickens. As for a retrovirus, the interaction between its envelope protein and cellular receptor is a crucial step in ALV-K infection. Tva, a protein previously determined to be associated with vitamin B12/cobalamin uptake, has been identified as the receptor of ALV-K. However, the molecular mechanism underlying the interaction between Tva and the envelope protein of ALV-K remains unclear. In this study, we identified the C-terminal loop of the LDL-A module of Tva as the minimal functional domain that directly interacts with gp85, the surface component of the ALV-K envelope protein. Further point-mutation analysis revealed that E53, L55, H59, and G70, which are exposed on the surface of Tva and are spatially adjacent, are key residues for the binding of Tva and gp85 and facilitate the entry of ALV-K. Homology modeling analysis indicated that the substitution of these four residues did not significantly impact the Tva structure but impaired the interaction between Tva and gp85 of ALV-K. Importantly, the gene-edited DF-1 cell line with precisely substituted E53, L55, H59, and G70 was completely resistant to ALV-K infection and did not affect vitamin B12/cobalamin uptake. Collectively, these findings not only contribute to a better understanding of the mechanism of ALV-K entry into host cells but also provide an ideal gene-editing target for antiviral study.
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The Bipartite Sequence Motif in the N and C Termini of gp85 of Subgroup J Avian Leukosis Virus Plays a Crucial Role in Receptor Binding and Viral Entry. J Virol 2020; 94:JVI.01232-20. [PMID: 32878894 DOI: 10.1128/jvi.01232-20] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Accepted: 08/29/2020] [Indexed: 01/24/2023] Open
Abstract
Subgroup J avian leukemia virus (ALV-J), belonging to the genus Alpharetrovirus, enters cells through its envelope surface unit (gp85) via specifically recognizing the cellular receptor chicken Na+/H+ exchanger type I (chNHE1), the 28 to 39 N-terminal residues of which were characterized as the minimal receptor functional domain in our previous studies. In this study, to further clarify the precise organization and properties of the interaction between ALV-J gp85 and chNHE1, we identified the chNHE1-binding domain of ALV-J gp85 using a series of gp85 mutants with segment substitutions and evaluating their effects on chNHE1 binding in protein-cell binding assays. Our results showed that hemagglutinin (HA) substitutions of amino acids (aa) 38 to 131 (N terminus of gp85) and aa 159 to 283 (C terminus of gp85) significantly inhibited the interaction between gp85 and chNHE1/chNHE1 loop 1. In addition, these HA-substituted chimeric gp85 proteins could not effectively block the entry of ALV-J into chNHE1-expressing cells. Furthermore, analysis of various N-linked glycosylation sites and cysteine mutants in gp85 revealed that glycosylation sites (N6 and N11) and cysteines (C3 and C9) were directly involved in receptor-gp85 binding and important for the entry of ALV-J into cells. Taken together, our findings indicated that the bipartite sequence motif, spanning aa 38 to 131 and aa 159 to 283, of ALV-J gp85 was essential for binding to chNHE1, with its two N-linked glycosylation sites and two cysteines being important for its receptor-binding function and subsequent viral infection steps.IMPORTANCE Infection of a cell by retroviruses requires the attachment and fusion of the host and viral membranes. The specific adsorption of envelope (Env) surface proteins to cell receptors is a key step in triggering infections and has been the target of antiviral drug screening. ALV-J is an economically important avian pathogen that belongs to the genus Alpharetrovirus and has a wider host range than other ALV subgroups. Our results showed that the amino acids 38 to 131 of the N terminus and 159 to 283 of the C terminus of ALV-J gp85 controlled the efficiency of gp85 binding to chNHE1 and were critical for viral infection. In addition, the glycosylation sites (N6 and N11) and cysteines (C3 and C9) of gp85 played a crucial role in the receptor binding and viral entry. These findings might help elucidate the mechanism of the entry of ALV-J into host cells and provide antiviral targets for the control of ALV-J.
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Residues 28 to 39 of the Extracellular Loop 1 of Chicken Na +/H + Exchanger Type I Mediate Cell Binding and Entry of Subgroup J Avian Leukosis Virus. J Virol 2017; 92:JVI.01627-17. [PMID: 29070685 DOI: 10.1128/jvi.01627-17] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Accepted: 10/17/2017] [Indexed: 12/14/2022] Open
Abstract
Chicken Na+/H+ exchanger type I (chNHE1), a multispan transmembrane protein, is a cellular receptor of the subgroup J avian leukosis virus (ALV-J). To identify the functional determinants of chNHE1 responsible for the ALV-J receptor activity, a series of chimeric receptors was created by exchanging the extracellular loops (ECL) of human NHE1 (huNHE1) and chNHE1 and by ECL replacement with a hemagglutinin (HA) tag. These chimeric receptors then were used in binding and entry assays to map the minimal ALV-J gp85-binding domain of chNHE1. We show that ECL1 of chNHE1 (chECL1) is the critical functional ECL that interacts directly with ALV-J gp85; ECL3 is also involved in ALV-J gp85 binding. Amino acid residues 28 to 39 of the N-terminal membrane-proximal region of chECL1 constitute the minimal domain required for chNHE1 binding of ALV-J gp85. These residues are sufficient to mediate viral entry into ALV-J nonpermissive cells. Point mutation analysis revealed that A30, V33, W38, and E39 of chECL1 are the key residues mediating the binding between chNHE1 and ALV-J gp85. Further, the replacement of residues 28 to 39 of huNHE1 with the corresponding chNHE1 residues converted the nonfunctional ALV-J receptor huNHE1 to a functional one. Importantly, soluble chECL1 and huECL1 harboring chNHE1 residues 28 to 39 both could effectively block ALV-J infection. Collectively, our findings indicate that residues 28 to 39 of chNHE1 constitute a domain that is critical for receptor function and mediate ALV-J entry.IMPORTANCE chNHE1 is a cellular receptor of ALV-J, a retrovirus that causes infections in chickens and serious economic losses in the poultry industry. Until now, the domains determining the chNHE1 receptor function remained unknown. We demonstrate that chECL1 is critical for receptor function, with residues 28 to 39 constituting the minimal functional domain responsible for chNHE1 binding of ALV-J gp85 and efficiently mediating ALV-J cell entry. These residues are located in the membrane-proximal region of the N terminus of chECL1, suggesting that the binding site of ALV-J gp85 on chNHE1 is probably located on the apex of the molecule; the receptor-binding mode might be different from that of retroviruses. We also found that soluble chECL1, as well as huECL1 harboring chNHE1 residues 28 to 39, effectively blocked ALV-J infection. These findings contribute to a better understanding of the ALV-J infection mechanism and also provide new insights into the control strategies for ALV-J infection.
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Nonsynonymous changes of equine lentivirus receptor-1 (ELR1) gene in amino acids involved in the interaction with equine infectious anemia virus (EIAV). Res Vet Sci 2017; 112:185-191. [PMID: 28500993 DOI: 10.1016/j.rvsc.2017.05.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Revised: 03/17/2017] [Accepted: 05/01/2017] [Indexed: 11/24/2022]
Abstract
Equine lentivirus receptor-1 (ELR1) has been characterized as the specific functional receptor that mediates equine infectious anemia virus (EIAV) entrance to horse macrophages. This receptor is tumor necrosis factor receptor superfamily member 14 (TNFRSF14). The aim of this study was to investigate the occurrence of allelic variants in the coding sequence of equine TNFRSF14 gene by screening for single-nucleotide polymorphisms (SNPs) in different equine populations. Forty seven horse samples were randomly selected from a reservoir of EIAV-seropositive and seronegative samples collected from different outbreaks and regions of Argentina. DNA samples were scanned via PCR and direct sequencing of exon 3 and exon 5 of TNFRSF14 gene. A total of 21 SNPs were identified, of which 11 were located in coding sequences. Within exon 5, four SNPs caused nonsynonymous substitutions, while two other SNPs caused synonymous substitutions in crucial residues (Ser112 and Thr114) implicated in the interaction with EIAV. Despite some of exon 5 variants occurred exclusively in EIAV-positive or EIAV-negative horses, critical residues for the function of the mature protein were conserved, accounting for selective pressures in favor of preserving the specific function of TNFRSF members and the host immune response. To our knowledge, this is the first report of the existence of allelic variations involving some crucial amino acid residues in horse ELR1. Further, it could be an initial step to test the possible functional relevance and relationship of these variants with EIAV infection and disease progression as well as to develop preventive strategies.
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Yun BL, Guan XL, Liu YZ, Zhang Y, Wang YQ, Qi XL, Cui HY, Liu CJ, Zhang YP, Gao HL, Gao L, Li K, Gao YL, Wang XM. Integrin αvβ1 Modulation Affects Subtype B Avian Metapneumovirus Fusion Protein-mediated Cell-Cell Fusion and Virus Infection. J Biol Chem 2016; 291:14815-25. [PMID: 27226547 DOI: 10.1074/jbc.m115.711382] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Indexed: 01/08/2023] Open
Abstract
Avian metapneumovirus (aMPV) fusion (F) protein mediates virus-cell membrane fusion to initiate viral infection, which requires F protein binding to its receptor(s) on the host cell surface. However, the receptor(s) for aMPV F protein is still not identified. All known subtype B aMPV (aMPV/B) F proteins contain a conserved Arg-Asp-Asp (RDD) motif, suggesting that the aMPV/B F protein may mediate membrane fusion via the binding of RDD to integrin. When blocked with integrin-specific peptides, aMPV/B F protein fusogenicity and viral replication were significantly reduced. Specifically we identified integrin αv and/or β1-mediated F protein fusogenicity and viral replication using antibody blocking, small interfering RNAs (siRNAs) knockdown, and overexpression. Additionally, overexpression of integrin αv and β1 in aMPV/B non-permissive cells conferred aMPV/B F protein binding and aMPV/B infection. When RDD was altered to RAE (Arg-Ala-Glu), aMPV/B F protein binding and fusogenic activity were profoundly impaired. These results suggest that integrin αvβ1 is a functional receptor for aMPV/B F protein-mediated membrane fusion and virus infection, which will provide new insights on the fusogenic mechanism and pathogenesis of aMPV.
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Affiliation(s)
- Bing-Ling Yun
- From the Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, No. 427 Maduan Street, Nan Gang District, Harbin 150001, Heilongjiang Province and
| | - Xiao-Lu Guan
- From the Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, No. 427 Maduan Street, Nan Gang District, Harbin 150001, Heilongjiang Province and
| | - Yong-Zhen Liu
- From the Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, No. 427 Maduan Street, Nan Gang District, Harbin 150001, Heilongjiang Province and
| | - Yao Zhang
- From the Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, No. 427 Maduan Street, Nan Gang District, Harbin 150001, Heilongjiang Province and
| | - Yong-Qiang Wang
- From the Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, No. 427 Maduan Street, Nan Gang District, Harbin 150001, Heilongjiang Province and
| | - Xiao-Le Qi
- From the Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, No. 427 Maduan Street, Nan Gang District, Harbin 150001, Heilongjiang Province and
| | - Hong-Yu Cui
- From the Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, No. 427 Maduan Street, Nan Gang District, Harbin 150001, Heilongjiang Province and
| | - Chang-Jun Liu
- From the Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, No. 427 Maduan Street, Nan Gang District, Harbin 150001, Heilongjiang Province and
| | - Yan-Ping Zhang
- From the Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, No. 427 Maduan Street, Nan Gang District, Harbin 150001, Heilongjiang Province and
| | - Hong-Lei Gao
- From the Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, No. 427 Maduan Street, Nan Gang District, Harbin 150001, Heilongjiang Province and
| | - Li Gao
- From the Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, No. 427 Maduan Street, Nan Gang District, Harbin 150001, Heilongjiang Province and
| | - Kai Li
- From the Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, No. 427 Maduan Street, Nan Gang District, Harbin 150001, Heilongjiang Province and
| | - Yu-Long Gao
- From the Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, No. 427 Maduan Street, Nan Gang District, Harbin 150001, Heilongjiang Province and
| | - Xiao-Mei Wang
- From the Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, No. 427 Maduan Street, Nan Gang District, Harbin 150001, Heilongjiang Province and the Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Disease and Zoonoses, Yangzhou 225009, China
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Duan L, Du J, Wang X, Zhou J, Wang X, Liu X. Structural and functional characterization of EIAV gp45 fusion peptide proximal region and asparagine-rich layer. Virology 2016; 491:64-72. [PMID: 26874586 DOI: 10.1016/j.virol.2016.01.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2015] [Revised: 01/14/2016] [Accepted: 01/19/2016] [Indexed: 10/22/2022]
Abstract
Equine infectious anaemia virus (EIAV) and human immunodeficiency virus (HIV) are members of the lentiviral genus. Similar to HIV gp41, EIAV gp45 is a fusogenic protein that mediates fusion between the viral particle and the host cell membrane. The crystal structure of gp45 reported reveals a different conformation in the here that includes the fusion peptide proximal region (FPPR) and neighboring asparagine-rich layer compared with previous HIV-1 gp41 structures. A complicated hydrogen-bond network containing a cluster of solvent molecules appears to be critical for the stability of the gp45 helical bundle. Interestingly, viral replication was relatively unaffected by site-directed mutagenesis of EIAV, in striking contrast to that of HIV-1. Based on these observations, we speculate that EIAV is more adaptable to emergent mutations, which might be important for the evolution of EIAV as a quasi-species, and could potentially contribute to the success of the EIAV vaccine.
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Affiliation(s)
- Liangwei Duan
- State Key Laboratory of Medicinal Chemical Biology, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Jiansen Du
- State Key Laboratory of Medicinal Chemical Biology, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Xuefeng Wang
- Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, China
| | - Jianhua Zhou
- Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, China
| | - Xiaojun Wang
- Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, China
| | - Xinqi Liu
- State Key Laboratory of Medicinal Chemical Biology, College of Life Sciences, Nankai University, Tianjin 300071, China.
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Liu Q, Ma J, Wang XF, Xiao F, Li LJ, Zhang JE, Lin YZ, Du C, He XJ, Wang X, Zhou JH. Infection with equine infectious anemia virus vaccine strain EIAVDLV121 causes no visible histopathological lesions in target organs in association with restricted viral replication and unique cytokine response. Vet Immunol Immunopathol 2016; 170:30-40. [PMID: 26832985 PMCID: PMC7112881 DOI: 10.1016/j.vetimm.2016.01.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Revised: 11/10/2015] [Accepted: 01/20/2016] [Indexed: 11/06/2022]
Abstract
The live equine infectious anemia virus (EIAV) vaccine strain EIAVDLV121 was developed by in vitro attenuation of a virulent strain, EIAVLN40, in the 1970s, and it has been demonstrated to induce protective immunity under laboratory and natural EIAV infection conditions. The detailed biological features of this attenuated virus remain to be further investigated. Experimental inoculation with EIAVDLV121 did not result in clinical symptoms even with immunosuppressive treatment in our previous studies. Here, we further investigated whether the replication of the vaccine strain EIAVDLV121 in experimentally infected horses causes histopathological lesions to develop in the targeted organs. Both the lungs and the spleen have been demonstrated to support EIAV replication. By evaluating the gross macroscopic and histological changes, we found that EIAVDLV121 did not cause detectable histopathological lesions and that it replicated several hundred times more slowly than its parental virulent strain, EIAVLN40, in tissues. Immunochemical assays of these tissues indicated that the primary target cells of EIAVDLV121 were monocytes/macrophages, but that EIAVLN40 also infected alveolar epithelial cells and vascular endothelial cells. In addition, both of these viral strains promoted the up- and down-regulation of the expression of various cytokines and chemokines, implicating the potential involvement of these cellular factors in the pathological outcomes of EIAV infection and host immune responses. Taken together, these results demonstrate that the EIAV vaccine strain does not cause obvious histopathological lesions or clinical symptoms and that it induces a unique cytokine response profile. These features are considered essential for EIAVDLV121 to function as an effective live vaccine.
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Affiliation(s)
- Qiang Liu
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute of Chinese Academy of Agricultural Sciences, Harbin 150001, China
| | - Jian Ma
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute of Chinese Academy of Agricultural Sciences, Harbin 150001, China
| | - Xue-Feng Wang
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute of Chinese Academy of Agricultural Sciences, Harbin 150001, China
| | - Fei Xiao
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute of Chinese Academy of Agricultural Sciences, Harbin 150001, China
| | - Li-Jia Li
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute of Chinese Academy of Agricultural Sciences, Harbin 150001, China
| | - Jiao-Er Zhang
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute of Chinese Academy of Agricultural Sciences, Harbin 150001, China
| | - Yue-Zhi Lin
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute of Chinese Academy of Agricultural Sciences, Harbin 150001, China
| | - Cheng Du
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute of Chinese Academy of Agricultural Sciences, Harbin 150001, China
| | - Xi-Jun He
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute of Chinese Academy of Agricultural Sciences, Harbin 150001, China.
| | - Xiaojun Wang
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute of Chinese Academy of Agricultural Sciences, Harbin 150001, China.
| | - Jian-Hua Zhou
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute of Chinese Academy of Agricultural Sciences, Harbin 150001, China; Harbin Pharmaceutical Group Biovaccine Company, Harbin 150069, China.
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Qian L, Han X, Liu X. Structural insight into equine lentivirus receptor 1. Protein Sci 2015; 24:633-42. [PMID: 25559821 DOI: 10.1002/pro.2634] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2014] [Revised: 12/23/2014] [Accepted: 12/29/2014] [Indexed: 11/07/2022]
Abstract
Equine lentivirus receptor 1 (ELR1) has been identified as a functional cellular receptor for equine infectious anemia virus (EIAV). Herein, recombinant ELR1 and EIAV surface glycoprotein gp90 were respectively expressed in Drosophila melanogaster S2 cells, and purified to homogeneity by Ni-NTA affinity chromatography and gel filtration chromatography. Gel filtration chromatography and analytical ultracentrifugation (AUC) analyses indicated that both ELR1 and gp90 existed as individual monomers in solution and formed a complex with a stoichiometry of 1:1 when mixed. The structure of ELR1 was first determined with the molecular replacement method, which belongs to the space group P42 21 2 with one molecule in an asymmetric unit. It contains eight antiparallel β-sheets, of which four are in cysteine rich domain 1 (CRD1) and two are in CRD2 and CRD3, respectively. Alignment of ELR1 with HVEM and CD134 indicated that Tyr61, Leu70, and Gly72 in CRD1 of ELR1 are important residues for binding to gp90. Isothermal titration calorimetry (ITC) experiments further confirmed that Leu70 and Gly72 are the critical residues.
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Affiliation(s)
- Lei Qian
- State Key Laboratory of Medicinal Chemical Biology, College of Life Sciences, Nankai University, Tianjin, 300071, China
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Lin YZ, Yang F, Zhang SQ, Sun LK, Wang XF, Du C, Zhou JH. The soluble form of the EIAV receptor encoded by an alternative splicing variant inhibits EIAV infection of target cells. PLoS One 2013; 8:e79299. [PMID: 24278125 PMCID: PMC3838338 DOI: 10.1371/journal.pone.0079299] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2013] [Accepted: 09/20/2013] [Indexed: 01/21/2023] Open
Abstract
Equine lentivirus receptor 1 (ELR1) has been identified as the sole receptor for equine infectious anemia virus (EIAV) and is a member of the tumor necrosis factor receptor (TNFR) superfamily. In addition to the previously described membrane-associated form of ELR1, two other major alternative splicing variant mRNAs were identified in equine monocyte-derived macrophages (eMDMs). One major spliced species (ELR1-IN) contained an insertion of 153 nt, which resulted in a premature stop codon situated 561 nt upstream of the predicted membrane spanning domain. The other major species (ELR1-DE) has a deletion of 109 nt that causes a shift of the open reading frame and generates a stop codon 312 nt downstream. Because ELR1-DE presumably encodes a peptide of a mere 23 residues, only ELR1-IN was further analyzed. The expression of a soluble form of ELR1 (sELR1) by ELR1-IN was confirmed by Western blot and immunofluorescence analyses. Similar to ELR1, the transcription level of ELR1-IN varied among individual horses and at different time points in the same individuals. The ratio of ELR1-IN mRNA species to ELR1 mRNA was approximately 1∶2.5. Pre-incubation of the recombinant sELR1 with EIAV significantly inhibited EIAV infection in equine macrophages, the primary in vivo target cell of the virus. Fetal equine dermal (FED) cells are susceptible to EIAV in vitro, and the replication of EIAV in FED cells transiently transfected with ELR1-IN was markedly reduced when compared with replication in cells transfected with the empty vector. Finally, the expression levels of both forms of the EIAV receptor were significantly regulated by infection with this virus. Taken together, our data indicate that sELR1 acts as a secreted cellular factor that inhibits EIAV infection in host cells.
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Affiliation(s)
- Yue-Zhi Lin
- Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Science, Harbin, China
| | - Fei Yang
- Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Science, Harbin, China
| | - Shu-Qin Zhang
- Institute of Special Wild Economic Animal and Plant Science, Chinese Academy of Agricultural Science, Changchun, China
| | - Liu-Ke Sun
- Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Science, Harbin, China
| | - Xue-Feng Wang
- Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Science, Harbin, China
| | - Cheng Du
- Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Science, Harbin, China
| | - Jian-Hua Zhou
- Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Science, Harbin, China
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Schwartz EJ, Pawelek KA, Harrington K, Cangelosi R, Madrid S. Immune Control of Equine Infectious Anemia Virus Infection by Cell-Mediated and Humoral Responses. ACTA ACUST UNITED AC 2013. [DOI: 10.4236/am.2013.48a023] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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11
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Sun C, Chu J, Singh S, Salter RD. Identification and characterization of a novel variant of the human P2X(7) receptor resulting in gain of function. Purinergic Signal 2009; 6:31-45. [PMID: 19838818 DOI: 10.1007/s11302-009-9168-9] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2009] [Accepted: 10/05/2009] [Indexed: 11/30/2022] Open
Abstract
The P2X(7) receptor exhibits significant allelic polymorphism in humans, with both loss and gain of function variants potentially impacting on a variety of infectious and inflammatory disorders. At least five loss-of-function polymorphisms (G150R, R307Q, T357S, E496A, and I568N) and two gain-of-function polymorphisms (H155Y and Q460R) have been identified and characterized to date. In this study, we used RT-PCR cloning to isolate and characterize P2X(7) cDNA clones from human PBMCs and THP-1 cells. A previously unreported variant with substitutions of V80M and A166G was identified. When expressed in HEK293 cells, this variant exhibited heightened sensitivity to the P2X(7) agonist (BzATP) relative to the most frequent allele, as shown by pore formation measured by fluorescent dye uptake into cells. Mutational analyses showed that A166G alteration was critical for the gain-of-function change, while V80M was not. Full-length variants with multiple previously identified nonsynonymous SNPs (H155Y, H270R, A348T, and E496A) were also identified. Distinct functional phenotypes of the P2X(7) variants or mutants constructed with multiple polymorphisms were observed. Gain-of-function variations (A166G or H155Y) could not rescue the loss-of-function E496A polymorphism. Synergistic effects of the gain-of-function variations were also observed. We also identified the A348T alteration as a weak gain-of-function variant. Thus, these results identify the new gain-of-function variant A166G and demonstrate that multiple-gene polymorphisms contribute to functional phenotypes of the human P2X(7) receptor. Furthermore, the results demonstrate that the C-terminal of the cysteine-rich domain 1 of P2X(7) is critical for regulation of P2X(7)-mediated pore formation.
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Affiliation(s)
- Chengqun Sun
- Department of Immunology, University of Pittsburgh School of Medicine, E1052 Biomedical Science Tower, Pittsburgh, PA 15261 USA
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Sedý JR, Spear PG, Ware CF. Cross-regulation between herpesviruses and the TNF superfamily members. Nat Rev Immunol 2008; 8:861-73. [PMID: 18949019 DOI: 10.1038/nri2434] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Herpesviruses have evolved numerous strategies to subvert host immune responses so they can coexist with their host species. These viruses 'co-opt' host genes for entry into host cells and then express immunomodulatory genes, including mimics of members of the tumour-necrosis factor (TNF) superfamily, that initiate and alter host-cell signalling pathways. TNF superfamily members have crucial roles in controlling herpesvirus infection by mediating the direct killing of infected cells and by enhancing immune responses. Despite these strong immune responses, herpesviruses persist in a latent form, which suggests a dynamic relationship between the host immune system and the virus that results in a balance between host survival and viral control.
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Affiliation(s)
- John R Sedý
- Division of Molecular Immunology, La Jolla Institute for Allergy and Immunology, La Jolla, California 92037, USA
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Sun C, Zhang B, Jin J, Montelaro RC. Binding of equine infectious anemia virus to the equine lentivirus receptor-1 is mediated by complex discontinuous sequences in the viral envelope gp90 protein. J Gen Virol 2008; 89:2011-2019. [PMID: 18632973 DOI: 10.1099/vir.0.83646-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The identification and characterization of a functional cellular receptor for equine infectious anemia virus (EIAV), designated equine lentivirus receptor-1 (ELR1), a member of the tumour necrosis factor receptor protein family, has been reported previously [Zhang, B. et al. (2005). Proc Natl Acad Sci U S A, 102 , 9918-9923]. The finding of a single receptor for EIAV is distinct from feline, simian and human immunodeficiency viruses, which typically utilize two co-receptors for infection, but is similar to avian and murine oncoviruses, which use single receptors. This study sought to determine ELR1-binding domains of EIAV gp90. Towards this goal, a GFP-tagged gp90 fusion protein (gp90GFP) expression vector was constructed and a specific cell-cell binding assay was developed to measure EIAV gp90 binding to ELR1. Using these assays, the receptor-binding properties of 41 gp90GFP mutants were evaluated, each with a sequential replacement 11 aa linear epitope peptide from the vesicular stomatitis virus glycoprotein (VSV-G tag), as well as eight mutants containing individual gp90 variable-domain deletions. The results of these studies demonstrated that, in general, gp90 constructs containing substitutions or deletions in the N-terminal third of gp90 retained their receptor-binding activity. In contrast, segment substitutions or deletions in the C-terminal two-thirds of gp90 eliminated receptor-binding activity. Thus, these results reveal for the first time that the ELR1-binding domains of EIAV gp90 are located in the C-terminal two-thirds of EIAV gp90, apparently as a complex of discontinuous determinants.
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Affiliation(s)
- Chengqun Sun
- Department of Molecular Genetics and Biochemistry, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - Baoshan Zhang
- Department of Molecular Genetics and Biochemistry, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - Jing Jin
- Department of Infectious Disease and Microbiology, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA 15261, USA.,Department of Molecular Genetics and Biochemistry, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - Ronald C Montelaro
- Department of Infectious Disease and Microbiology, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA 15261, USA.,Department of Molecular Genetics and Biochemistry, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15261, USA
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An equine infectious anemia virus variant superinfects cells through novel receptor interactions. J Virol 2008; 82:9425-32. [PMID: 18667522 DOI: 10.1128/jvi.01142-08] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Wild-type strains of equine infectious anemia virus (EIAV) prevent superinfection of previously infected cells. A variant strain of virus that spontaneously arose during passage, EIAV(vMA-1c), can circumvent this mechanism in some cells, such as equine dermis (ED) cells, but not in others, such as equine endothelial cells. EIAV(vMA-1c) superinfection of ED cells results in a buildup of unintegrated viral DNA and rapid killing of the cell monolayer. Here, we examined the mechanism of resistance that is used by EIAV to prevent superinfection and explored the means by which EIAV(vMA-1c) overcomes this restriction. We found that the cellular receptor used by EIAV, equine lentivirus receptor 1 (ELR1), remains on the surface of cells chronically infected with EIAV, suggesting that wild-type EIAV interferes with superinfection by masking ELR1. The addition of soluble wild-type SU protein to the medium during infection blocked infection by wild-type strains of virus, implicating SU as the viral protein responsible for interfering with virion entry into previously infected cells. Additionally, interference of wild-type EIAV binding to ELR1 by the addition of either anti-ELR1 antibodies or the ELR1 ectodomain prevented entry of the wild-type strains of EIAV into two permissive cell populations. Many of these same interference treatments prevented EIAV(vMA-1c) infection of endothelial cells but only modestly affected the ability of EIAV(vMA-1c) to enter and kill previously infected ED cells. These findings indicate that EIAV(vMA-1c) retains the ability to use ELR1 for entry and suggest that this virus can interact with an additional, unidentified receptor to superinfect ED cells.
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