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Escalera A, Laporte M, Turner S, Karakus U, Gonzalez-Reiche AS, van de Guchte A, Farrugia K, Khalil Z, van Bakel H, Smith D, García-Sastre A, Aydillo T. The impact of S2 mutations on Omicron SARS-CoV-2 cell surface expression and fusogenicity. Emerg Microbes Infect 2024; 13:2297553. [PMID: 38112266 PMCID: PMC10866063 DOI: 10.1080/22221751.2023.2297553] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Accepted: 12/17/2023] [Indexed: 12/21/2023]
Abstract
SARS-CoV-2 Omicron subvariants are still emerging and spreading worldwide. These variants contain a high number of polymorphisms in the spike (S) glycoprotein that could potentially impact their pathogenicity and transmission. We have previously shown that the S:655Y and P681H mutations enhance S protein cleavage and syncytia formation. Interestingly, these polymorphisms are present in Omicron S protein. Here, we characterized the cleavage efficiency and fusogenicity of the S protein of different Omicron sublineages. Our results showed that Omicron BA.1 subvariant is efficiently cleaved but it is poorly fusogenic compared to previous SARS-CoV-2 strains. To understand the basis of this phenotype, we generated chimeric S protein using combinations of the S1 and S2 domains from WA1, Delta and Omicron BA.1 variants. We found that the S2 domain of Omicron BA.1 hindered efficient cell-cell fusion. Interestingly, this domain only contains six unique polymorphisms never detected before in ancestral SARS-CoV-2 variants. WA1614G S proteins containing the six individuals S2 Omicron mutations were assessed for their fusogenicity and S surface expression after transfection in cells. Results showed that the S:N856K and N969K substitutions decreased syncytia formation and impacted S protein cell surface levels. However, we observed that "first-generation" Omicron sublineages that emerged subsequently, had convergently evolved to an enhanced fusogenic activity and S expression on the surface of infected cells while "second-generation" Omicron variants have highly diverged and showed lineage-specific fusogenic properties. Importantly, our findings could have potential implications in the improvement and redesign of COVID-19 vaccines.
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Affiliation(s)
- Alba Escalera
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Graduate School of Biomedical Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Manon Laporte
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Sam Turner
- Center for Pathogen Evolution, Department of Zoology, University of Cambridge, Cambridge, UK
| | - Umut Karakus
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Ana S. Gonzalez-Reiche
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Adriana van de Guchte
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Keith Farrugia
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Zain Khalil
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Harm van Bakel
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Icahn Genomics Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Derek Smith
- Center for Pathogen Evolution, Department of Zoology, University of Cambridge, Cambridge, UK
| | - Adolfo García-Sastre
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Department of Medicine, Division of Infectious Diseases, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Department of Pathology, Molecular and Cell-Based Medicine, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- The Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Teresa Aydillo
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
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Merckens A, Sieler M, Keil S, Dittmar T. Altered Phenotypes of Breast Epithelial × Breast Cancer Hybrids after ZEB1 Knock-Out. Int J Mol Sci 2023; 24:17310. [PMID: 38139138 PMCID: PMC10744253 DOI: 10.3390/ijms242417310] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Revised: 12/06/2023] [Accepted: 12/07/2023] [Indexed: 12/24/2023] Open
Abstract
ZEB1 plays a pivotal role in epithelial-to-mesenchymal transition (EMT), (cancer) cell stemness and cancer therapy resistance. The M13HS tumor hybrids, which were derived from spontaneous fusion events between the M13SV1-EGFP-Neo breast epithelial cells and HS578T-Hyg breast cancer cells, express ZEB1 and exhibit prospective cancer stem cell properties. To explore a possible correlation between the ZEB1 and stemness/ EMT-related properties in M13HS tumor hybrids, ZEB1 was knocked-out by CRISPR/Cas9. Colony formation, mammosphere formation, cell migration, invasion assays, flow cytometry and Western blot analyses were performed for the characterization of ZEB1 knock-out cells. The ZEB1 knock-out in M13HS tumor cells was not correlated with the down-regulation of the EMT-related markers N-CADHERIN (CDH2) and VIMENTIN and up-regulation of miR-200c-3p. Nonetheless, both the colony formation and mammosphere formation capacities of the M13HS ZEB1 knock-out cells were markedly reduced. Interestingly, the M13HS-2 ZEB1-KO cells harbored a markedly higher fraction of ALDH1-positive cells. The Transwell/ Boyden chamber migration assay data indicated a reduced migratory activity of the M13HS ZEB1-knock-out tumor hybrids, whereas in scratch/ wound-healing assays only the M13SH-8 ZEB1-knock-out cells possessed a reduced locomotory activity. Similarly, only the M13HS-8 ZEB1-knock-out tumor hybrids showed a reduced invasion capacity. Although the ZEB1 knock-out resulted in only moderate phenotypic changes, our data support the role of ZEB1 in EMT and stemness.
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Affiliation(s)
| | | | | | - Thomas Dittmar
- Institute of Immunology, Center for Biomedical Education and Research (ZBAF), Witten/Herdecke University, Stockumer Str. 10, 58448 Witten, Germany; (A.M.); (M.S.); (S.K.)
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3
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Xia S, Wang L, Jiao F, Yu X, Xu W, Huang Z, Li X, Wang Q, Zhu Y, Man Q, Jiang S, Lu L. SARS-CoV-2 Omicron subvariants exhibit distinct fusogenicity, but similar sensitivity, to pan-CoV fusion inhibitors. Emerg Microbes Infect 2023; 12:2178241. [PMID: 36748716 PMCID: PMC9970205 DOI: 10.1080/22221751.2023.2178241] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Continuous emergence of the Omicron variant, along with its subvariants, has caused an increasing number of infections, reinfections, and vaccine-breakthrough infections, seriously threatening human health. Recently, several new Omicron subvariants, such as BA.5, BA.2.75, BA.4.6, and BF.7, bearing distinct mutation profiles in their spike (S) proteins, have significantly increased their capacity to evade vaccine-induced immunity and have shown enhanced infectivity and transmissibility, quickly becoming dominant sublineages. In this study, we found the S proteins of these Omicron subvariants to have 2- to 4-fold more efficient membrane fusion kinetics than that of the original Omicron variant (BA.1), indicating that these novel Omicron subvariants might possess increased pathogenicity. We also identified that peptide-based pan-CoV fusion inhibitors, EK1 and EK1C4, showed equal efficacy against membrane fusion mediated by S proteins of the noted Omicron subvariants and infection by their pseudoviruses. Additionally, either immune sera induced by wild-type (WT) SARS-CoV-2 RBD-based vaccine or BA.2 convalescent sera showed potent synergism with EK1 against both WT SARS-CoV-2 and various Omicron subvariants, further suggesting that EK1-based fusion inhibitors are promising candidates for development as clinical antiviral agents against the currently circulating Omicron subvariants.
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Affiliation(s)
- Shuai Xia
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS), Shanghai Institute of Infectious Disease and Biosecurity, School of Basic Medical Sciences, Shanghai Frontiers Science Center of Pathogenic Microbes and Infection, Fudan University, Shanghai, People’s Republic of China,Shuai Xia Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS), Shanghai Institute of Infectious Disease and Biosecurity, School of Basic Medical Sciences, Shanghai Frontiers Science Center of Pathogenic Microbes and Infection, Fudan University, Shanghai, People’s Republic of China
| | - Lijue Wang
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS), Shanghai Institute of Infectious Disease and Biosecurity, School of Basic Medical Sciences, Shanghai Frontiers Science Center of Pathogenic Microbes and Infection, Fudan University, Shanghai, People’s Republic of China
| | - Fanke Jiao
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS), Shanghai Institute of Infectious Disease and Biosecurity, School of Basic Medical Sciences, Shanghai Frontiers Science Center of Pathogenic Microbes and Infection, Fudan University, Shanghai, People’s Republic of China
| | - Xueying Yu
- Department of Clinical Laboratory, Shanghai Fourth People's Hospital, School of Medicine, Tongji University, Shanghai, People’s Republic of China
| | - Wei Xu
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS), Shanghai Institute of Infectious Disease and Biosecurity, School of Basic Medical Sciences, Shanghai Frontiers Science Center of Pathogenic Microbes and Infection, Fudan University, Shanghai, People’s Republic of China
| | - Ziqi Huang
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS), Shanghai Institute of Infectious Disease and Biosecurity, School of Basic Medical Sciences, Shanghai Frontiers Science Center of Pathogenic Microbes and Infection, Fudan University, Shanghai, People’s Republic of China
| | - Xicheng Li
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS), Shanghai Institute of Infectious Disease and Biosecurity, School of Basic Medical Sciences, Shanghai Frontiers Science Center of Pathogenic Microbes and Infection, Fudan University, Shanghai, People’s Republic of China
| | - Qian Wang
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS), Shanghai Institute of Infectious Disease and Biosecurity, School of Basic Medical Sciences, Shanghai Frontiers Science Center of Pathogenic Microbes and Infection, Fudan University, Shanghai, People’s Republic of China
| | - Yun Zhu
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, People’s Republic of China
| | - Qiuhong Man
- Department of Clinical Laboratory, Shanghai Fourth People's Hospital, School of Medicine, Tongji University, Shanghai, People’s Republic of China,Qiuhong Man Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS), Shanghai Institute of Infectious Disease and Biosecurity, School of Basic Medical Sciences, Shanghai Frontiers Science Center of Pathogenic Microbes and Infection, Fudan University, Shanghai, People’s Republic of China
| | - Shibo Jiang
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS), Shanghai Institute of Infectious Disease and Biosecurity, School of Basic Medical Sciences, Shanghai Frontiers Science Center of Pathogenic Microbes and Infection, Fudan University, Shanghai, People’s Republic of China,Shibo Jiang Department of Clinical Laboratory, Shanghai Fourth People's Hospital, School of Medicine, Tongji University, Shanghai, People’s Republic of China
| | - Lu Lu
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS), Shanghai Institute of Infectious Disease and Biosecurity, School of Basic Medical Sciences, Shanghai Frontiers Science Center of Pathogenic Microbes and Infection, Fudan University, Shanghai, People’s Republic of China, Lu Lu Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS), Shanghai Institute of Infectious Disease and Biosecurity, School of Basic Medical Sciences, Shanghai Frontiers Science Center of Pathogenic Microbes and Infection, Fudan University, Shanghai, People’s Republic of China
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Sfera A, Rahman L, Zapata-Martín Del Campo CM, Kozlakidis Z. Long COVID as a Tauopathy: Of "Brain Fog" and "Fusogen Storms". Int J Mol Sci 2023; 24:12648. [PMID: 37628830 PMCID: PMC10454863 DOI: 10.3390/ijms241612648] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2023] [Revised: 08/04/2023] [Accepted: 08/06/2023] [Indexed: 08/27/2023] Open
Abstract
Long COVID, also called post-acute sequelae of SARS-CoV-2, is characterized by a multitude of lingering symptoms, including impaired cognition, that can last for many months. This symptom, often called "brain fog", affects the life quality of numerous individuals, increasing medical complications as well as healthcare expenditures. The etiopathogenesis of SARS-CoV-2-induced cognitive deficit is unclear, but the most likely cause is chronic inflammation maintained by a viral remnant thriving in select body reservoirs. These viral sanctuaries are likely comprised of fused, senescent cells, including microglia and astrocytes, that the pathogen can convert into neurotoxic phenotypes. Moreover, as the enteric nervous system contains neurons and glia, the virus likely lingers in the gastrointestinal tract as well, accounting for the intestinal symptoms of long COVID. Fusogens are proteins that can overcome the repulsive forces between cell membranes, allowing the virus to coalesce with host cells and enter the cytoplasm. In the intracellular compartment, the pathogen hijacks the actin cytoskeleton, fusing host cells with each other and engendering pathological syncytia. Cell-cell fusion enables the virus to infect the healthy neighboring cells. We surmise that syncytia formation drives cognitive impairment by facilitating the "seeding" of hyperphosphorylated Tau, documented in COVID-19. In our previous work, we hypothesized that the SARS-CoV-2 virus induces premature endothelial senescence, increasing the permeability of the intestinal and blood-brain barrier. This enables the migration of gastrointestinal tract microbes and/or their components into the host circulation, eventually reaching the brain where they may induce cognitive dysfunction. For example, translocated lipopolysaccharides or microbial DNA can induce Tau hyperphosphorylation, likely accounting for memory problems. In this perspective article, we examine the pathogenetic mechanisms and potential biomarkers of long COVID, including microbial cell-free DNA, interleukin 22, and phosphorylated Tau, as well as the beneficial effect of transcutaneous vagal nerve stimulation.
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Affiliation(s)
- Adonis Sfera
- Paton State Hospital, 3102 Highland Ave, Patton, CA 92369, USA
- School of Behavioral Health, Loma Linda University, 11139 Anderson St., Loma Linda, CA 92350, USA
- Department of Psychiatry, University of California, Riverside 900 University Ave, Riverside, CA 92521, USA
| | - Leah Rahman
- Department of Neuroscience, University of Oregon, 222 Huestis Hall, Eugene, OR 97401, USA
| | | | - Zisis Kozlakidis
- International Agency for Research on Cancer, World Health Organization, 69000 Lyon, France
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5
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Reuter N, Chen X, Kropff B, Peter AS, Britt WJ, Mach M, Überla K, Thomas M. SARS-CoV-2 Spike Protein Is Capable of Inducing Cell-Cell Fusions Independent from Its Receptor ACE2 and This Activity Can Be Impaired by Furin Inhibitors or a Subset of Monoclonal Antibodies. Viruses 2023; 15:1500. [PMID: 37515187 PMCID: PMC10384293 DOI: 10.3390/v15071500] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Revised: 06/27/2023] [Accepted: 06/30/2023] [Indexed: 07/30/2023] Open
Abstract
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which was responsible for the COVID-19 pandemic, efficiently spreads cell-to-cell through mechanisms facilitated by its membrane glycoprotein spike. We established a dual split protein (DSP) assay based on the complementation of GFP and luciferase to quantify the fusogenic activity of the SARS-CoV-2 spike protein. We provide several lines of evidence that the spike protein of SARS-CoV-2, but not SARS-CoV-1, induced cell-cell fusion even in the absence of its receptor, angiotensin-converting enzyme 2 (ACE2). This poorly described ACE2-independent cell fusion activity of the spike protein was strictly dependent on the proteasomal cleavage of the spike by furin while TMPRSS2 was dispensable. Previous and current variants of concern (VOCs) differed significantly in their fusogenicity. The Delta spike was extremely potent compared to Alpha, Beta, Gamma and Kappa, while the Omicron spike was almost devoid of receptor-independent fusion activity. Nonetheless, for all analyzed variants, cell fusion was dependent on furin cleavage and could be pharmacologically inhibited with CMK. Mapping studies revealed that amino acids 652-1273 conferred the ACE2-independent fusion activity of the spike. Unexpectedly, residues proximal to the furin cleavage site were not of major relevance, whereas residue 655 critically regulated fusion. Finally, we found that the spike's fusion activity in the absence of ACE2 could be inhibited by antibodies directed against its N-terminal domain (NTD) but not by antibodies targeting its receptor-binding domain (RBD). In conclusion, our BSL-1-compatible DSP assay allowed us to screen for inhibitors or antibodies that interfere with the spike's fusogenic activity and may therefore contribute to both rational vaccine design and development of novel treatment options against SARS-CoV-2.
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Affiliation(s)
- Nina Reuter
- Virologisches Institut, Klinische und Molekulare Virologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - Xiaohan Chen
- Virologisches Institut, Klinische und Molekulare Virologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - Barbara Kropff
- Virologisches Institut, Klinische und Molekulare Virologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - Antonia Sophia Peter
- Virologisches Institut, Klinische und Molekulare Virologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - William J Britt
- Departments of Pediatrics, Microbiology and Neurobiology, Children's Hospital of Alabama, School of Medicine, University of Alabama, Birmingham, AL 35233-1771, USA
| | - Michael Mach
- Virologisches Institut, Klinische und Molekulare Virologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - Klaus Überla
- Virologisches Institut, Klinische und Molekulare Virologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - Marco Thomas
- Virologisches Institut, Klinische und Molekulare Virologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054 Erlangen, Germany
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6
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Zhou X, Cimato G, Zhou Y, Frascaroli G, Brune W. A Virus Genetic System to Analyze the Fusogenicity of Human Cytomegalovirus Glycoprotein B Variants. Viruses 2023; 15:v15040979. [PMID: 37112959 PMCID: PMC10142178 DOI: 10.3390/v15040979] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 04/09/2023] [Accepted: 04/14/2023] [Indexed: 04/29/2023] Open
Abstract
Viruses can induce the fusion of infected and neighboring cells, leading to the formation of syncytia. Cell-cell fusion is mediated by viral fusion proteins on the plasma membrane of infected cells that interact with cellular receptors on neighboring cells. Viruses use this mechanism to spread rapidly to adjacent cells or escape host immunity. For some viruses, syncytium formation is a hallmark of infection and a known pathogenicity factor. For others, the role of syncytium formation in viral dissemination and pathogenicity remains poorly understood. Human cytomegalovirus (HCMV) is an important cause of morbidity and mortality in transplant patients and the leading cause of congenital infections. Clinical HCMV isolates have broad cell tropism but differ in their ability to induce cell-cell fusions, and little is known about the molecular determinants. We developed a system to analyze HCMV glycoprotein B (gB) variants in a defined genetic background. HCMV strains TB40/E and TR were used as vectors to compare the fusogenicity of six gB variants from congenitally infected fetuses with those from three laboratory strains. Five of them conferred the ability to induce the fusion of MRC-5 human embryonic lung fibroblasts to one or both backbone strains, as determined by a split GFP-luciferase reporter system. The same gB variants were not sufficient to induce syncytia in infected ARPE-19 epithelial cells, suggesting that additional factors are involved. The system described here allows a systematic comparison of the fusogenicity of viral envelope glycoproteins and may help to clarify whether fusion-promoting variants are associated with increased pathogenicity.
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Affiliation(s)
- Xuan Zhou
- Leibniz Institute of Virology (LIV), 20251 Hamburg, Germany
| | - Giorgia Cimato
- Leibniz Institute of Virology (LIV), 20251 Hamburg, Germany
| | - Yihua Zhou
- Departments of Laboratory Medicine and Infectious Diseases, Nanjing Drum Tower Hospital and Jiangsu Key Laboratory for Molecular Medicine, Medical School of Nanjing University, Nanjing 210008, China
| | | | - Wolfram Brune
- Leibniz Institute of Virology (LIV), 20251 Hamburg, Germany
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7
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Zhang Y, Zhang L, Wu J, Yu Y, Liu S, Li T, Li Q, Ding R, Wang H, Nie J, Cui Z, Wang Y, Huang W, Wang Y. A second functional furin site in the SARS-CoV-2 spike protein. Emerg Microbes Infect 2022; 11:182-194. [PMID: 34856891 PMCID: PMC8741242 DOI: 10.1080/22221751.2021.2014284] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The ubiquitously-expressed proteolytic enzyme furin is closely related to the pathogenesis of SARS-CoV-2 and therefore represents a key target for antiviral therapy. Based on bioinformatic analysis and pseudovirus tests, we discovered a second functional furin site located in the spike protein. Furin still increased the infectivity of mutated SARS-CoV-2 pseudovirus in 293T-ACE2 cells when the canonical polybasic cleavage site (682-686) was deleted. However, K814A mutation eliminated the enhancing effect of furin on virus infection. Furin inhibitor prevented infection by 682-686-deleted SARS-CoV-2 in 293T-ACE2-furin cells, but not the K814A mutant. K814A mutation did not affect the activity of TMPRSS2 and cathepsin L but did impact the cleavage of S2 into S2' and cell-cell fusion. Additionally, we showed that this functional furin site exists in RaTG13 from bat and PCoV-GD/GX from pangolin. Therefore, we discovered a new functional furin site that is pivotal in promoting SARS-CoV-2 infection.
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Affiliation(s)
- Yue Zhang
- Division of HIV/AIDS and Sex-transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), Beijing, People's Republic of China
- National Vaccine & Serum Institute, Beijing, People's Republic of China
| | - Li Zhang
- Division of HIV/AIDS and Sex-transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), Beijing, People's Republic of China
| | - Jiajing Wu
- Division of HIV/AIDS and Sex-transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), Beijing, People's Republic of China
| | - Yuanling Yu
- Division of HIV/AIDS and Sex-transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), Beijing, People's Republic of China
| | - Shuo Liu
- Division of HIV/AIDS and Sex-transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), Beijing, People's Republic of China
| | - Tao Li
- Division of HIV/AIDS and Sex-transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), Beijing, People's Republic of China
| | - Qianqian Li
- Division of HIV/AIDS and Sex-transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), Beijing, People's Republic of China
| | - Ruxia Ding
- Division of HIV/AIDS and Sex-transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), Beijing, People's Republic of China
| | - Haixin Wang
- Division of HIV/AIDS and Sex-transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), Beijing, People's Republic of China
| | - Jianhui Nie
- Division of HIV/AIDS and Sex-transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), Beijing, People's Republic of China
| | - Zhimin Cui
- Division of HIV/AIDS and Sex-transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), Beijing, People's Republic of China
| | - Yulin Wang
- National Vaccine & Serum Institute, Beijing, People's Republic of China
| | - Weijin Huang
- Division of HIV/AIDS and Sex-transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), Beijing, People's Republic of China
| | - Youchun Wang
- Division of HIV/AIDS and Sex-transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), Beijing, People's Republic of China
- Lead Contact
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8
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Zhang L, Li Q, Wu J, Yu Y, Zhang Y, Nie J, Liang Z, Cui Z, Liu S, Wang H, Ding R, Jiang F, Li T, Nie L, Lu Q, Li J, Qin L, Jiang Y, Shi Y, Xu W, Huang W, Wang Y. Analysis of SARS-CoV-2 variants B.1.617: host tropism, proteolytic activation, cell-cell fusion, and neutralization sensitivity. Emerg Microbes Infect 2022; 11:1024-1036. [PMID: 35293847 PMCID: PMC9004538 DOI: 10.1080/22221751.2022.2054369] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2021] [Accepted: 03/12/2022] [Indexed: 12/13/2022]
Abstract
SARS-CoV-2 has caused the COVID-19 pandemic. B.1.617 variants (including Kappa and Delta) have been transmitted rapidly in India. The transmissibility, pathogenicity, and neutralization characteristics of these variants have received considerable interest. In this study, 22 pseudotyped viruses were constructed for B.1.617 variants and their corresponding single amino acid mutations. B.1.617 variants did not exhibit significant enhanced infectivity in human cells, but mutations T478K and E484Q in the receptor binding domain led to enhanced infectivity in mouse ACE2-overexpressing cells. Furin activities were slightly increased against B.1.617 variants and cell-cell fusion after infection of B.1.617 variants were enhanced. Furthermore, B.1.617 variants escaped neutralization by several mAbs, mainly because of mutations L452R, T478K, and E484Q in the receptor binding domain. The neutralization activities of sera from convalescent patients, inactivated vaccine-immunized volunteers, adenovirus vaccine-immunized volunteers, and SARS-CoV-2 immunized animals against pseudotyped B.1.617 variants were reduced by approximately twofold, compared with the D614G variant.
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Affiliation(s)
- Li Zhang
- Division of HIV/AIDS and Sex-transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), Beijing, People's Republic of China
| | - Qianqian Li
- Division of HIV/AIDS and Sex-transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), Beijing, People's Republic of China
- Jiangsu Recbio Technology Co., Ltd., Taizhou, China
| | - Jiajing Wu
- Division of HIV/AIDS and Sex-transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), Beijing, People's Republic of China
| | - Yuanling Yu
- Division of HIV/AIDS and Sex-transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), Beijing, People's Republic of China
| | - Yue Zhang
- Division of HIV/AIDS and Sex-transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), Beijing, People's Republic of China
| | - Jianhui Nie
- Division of HIV/AIDS and Sex-transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), Beijing, People's Republic of China
| | - Ziteng Liang
- Division of HIV/AIDS and Sex-transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), Beijing, People's Republic of China
| | - Zhimin Cui
- Division of HIV/AIDS and Sex-transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), Beijing, People's Republic of China
| | - Shuo Liu
- Division of HIV/AIDS and Sex-transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), Beijing, People's Republic of China
| | - Haixin Wang
- Division of HIV/AIDS and Sex-transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), Beijing, People's Republic of China
| | - Ruxia Ding
- Division of HIV/AIDS and Sex-transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), Beijing, People's Republic of China
| | - Fei Jiang
- Division of HIV/AIDS and Sex-transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), Beijing, People's Republic of China
| | - Tao Li
- Division of HIV/AIDS and Sex-transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), Beijing, People's Republic of China
| | - Lingling Nie
- Division of HIV/AIDS and Sex-transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), Beijing, People's Republic of China
| | - Qiong Lu
- Division of HIV/AIDS and Sex-transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), Beijing, People's Republic of China
| | - Jiayi Li
- Division of HIV/AIDS and Sex-transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), Beijing, People's Republic of China
| | - Lili Qin
- Acro Biosystems, Inc., Beijing, People’s Republic of China
| | - Yinan Jiang
- Acro Biosystems, Inc., Beijing, People’s Republic of China
| | - Yi Shi
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, People’s Republic of China
- Research Network of Immunity and Health (RNIH), Beijing Institutes of Life Science, Chinese Academy of Sciences, Beijing, People’s Republic of China
| | - Wenbo Xu
- National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, People’s Republic of China
| | - Weijin Huang
- Division of HIV/AIDS and Sex-transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), Beijing, People's Republic of China
| | - Youchun Wang
- Division of HIV/AIDS and Sex-transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), Beijing, People's Republic of China
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9
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Abstract
Swine acute diarrhea syndrome coronavirus (SADS-CoV) was reported in China in 2017 and is a causative agent of porcine enteric disease. Recent studies indicate that cells from various hosts are susceptible to SADS-CoV, suggesting the zoonotic potential of this virus. However, little is known about the mechanisms through which this virus enters cells. In this study, we investigated the role of furin in SADS-CoV spike (S)-mediated cell-cell fusion and entry. We found that the SADS-CoV S protein induced the fusion of various cells. Cell-cell fusion was inhibited by the proprotein convertase inhibitor dec-RVKR-cmk, and between cells transfected with mutant S proteins resistant to furin cleavage. These findings revealed that furin-induced cleavage of the SADS-CoV S protein is required for cell-cell fusion. Using mutagenesis analysis, we demonstrated that furin cleaves the SADS-CoV S protein near the S1/S2 cleavage site, 446RYVR449 and 543AVRR546. We used pseudotyped viruses to determine whether furin-induced S cleavage is also required for viral entry. Pseudotyped viruses expressing S proteins with a mutated furin cleavage site could be transduced into target cells, indicating that furin-induced cleavage is not required for pseudotyped virus entry. Our data indicate that S cleavage is critical for SADS-CoV S-mediated cell-cell fusion and suggest that furin might be a host target for SADS-CoV antivirals.
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Affiliation(s)
- Jinman Kim
- Laboratory of Veterinary Public Health, College of Veterinary Medicine, Chungnam National University, Daejeon 34134, Republic of Korea
| | - Jaewon Yoon
- Laboratory of Veterinary Public Health, College of Veterinary Medicine, Chungnam National University, Daejeon 34134, Republic of Korea
| | - Jung-Eun Park
- Laboratory of Veterinary Public Health, College of Veterinary Medicine, Chungnam National University, Daejeon 34134, Republic of Korea.,Research Institute of Veterinary Medicine, Chungnam National University, Daejeon 34134, Republic of Korea
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10
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Zeng C, Evans JP, King T, Zheng YM, Oltz EM, Whelan SPJ, Saif LJ, Peeples ME, Liu SL. SARS-CoV-2 spreads through cell-to-cell transmission. Proc Natl Acad Sci U S A 2022; 119:e2111400119. [PMID: 34937699 DOI: 10.1073/pnas.2111400119] [Citation(s) in RCA: 121] [Impact Index Per Article: 60.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/29/2021] [Indexed: 02/07/2023] Open
Abstract
It is currently unknown if SARS-CoV-2 can spread through cell–cell contacts, and if so, the underlying mechanisms and implications. In this work, we show, by using lentiviral pseudotyped virus, that the spike protein of SARS-CoV-2 mediates the viral cell-to-cell transmission, with an efficiency higher than that of SARS-CoV. We also find that cell–cell fusion contributes to cell-to-cell transmission, yet ACE2 is not absolutely required. While the authentic variants of concern (VOCs) B.1.1.7 (alpha) and B.1.351 (beta) differ in cell-free infectivity from wild type and from each other, these VOCs have similar cell-to-cell transmission capability and exhibit differential sensitivity to neutralization by vaccinee sera. Results from our study will contribute to a better understanding of SARS-CoV-2 spread and pathogenesis. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a highly transmissible coronavirus responsible for the global COVID-19 pandemic. Herein, we provide evidence that SARS-CoV-2 spreads through cell–cell contact in cultures, mediated by the spike glycoprotein. SARS-CoV-2 spike is more efficient in facilitating cell-to-cell transmission than is SARS-CoV spike, which reflects, in part, their differential cell–cell fusion activity. Interestingly, treatment of cocultured cells with endosomal entry inhibitors impairs cell-to-cell transmission, implicating endosomal membrane fusion as an underlying mechanism. Compared with cell-free infection, cell-to-cell transmission of SARS-CoV-2 is refractory to inhibition by neutralizing antibody or convalescent sera of COVID-19 patients. While angiotensin-converting enzyme 2 enhances cell-to-cell transmission, we find that it is not absolutely required. Notably, despite differences in cell-free infectivity, the authentic variants of concern (VOCs) B.1.1.7 (alpha) and B.1.351 (beta) have similar cell-to-cell transmission capability. Moreover, B.1.351 is more resistant to neutralization by vaccinee sera in cell-free infection, whereas B.1.1.7 is more resistant to inhibition by vaccinee sera in cell-to-cell transmission. Overall, our study reveals critical features of SARS-CoV-2 spike-mediated cell-to-cell transmission, with important implications for a better understanding of SARS-CoV-2 spread and pathogenesis.
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11
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Tang J, Frascaroli G, Zhou X, Knickmann J, Brune W. Cell Fusion and Syncytium Formation in Betaherpesvirus Infection. Viruses 2021; 13:v13101973. [PMID: 34696402 PMCID: PMC8537622 DOI: 10.3390/v13101973] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Revised: 09/22/2021] [Accepted: 09/28/2021] [Indexed: 12/14/2022] Open
Abstract
Cell–cell fusion is a fundamental and complex process that occurs during reproduction, organ and tissue growth, cancer metastasis, immune response, and infection. All enveloped viruses express one or more proteins that drive the fusion of the viral envelope with cellular membranes. The same proteins can mediate the fusion of the plasma membranes of adjacent cells, leading to the formation of multinucleated syncytia. While cell–cell fusion triggered by alpha- and gammaherpesviruses is well-studied, much less is known about the fusogenic potential of betaherpesviruses such as human cytomegalovirus (HCMV) and human herpesviruses 6 and 7 (HHV-6 and HHV-7). These are slow-growing viruses that are highly prevalent in the human population and associated with several diseases, particularly in individuals with an immature or impaired immune system such as fetuses and transplant recipients. While HHV-6 and HHV-7 are strictly lymphotropic, HCMV infects a very broad range of cell types including epithelial, endothelial, mesenchymal, and myeloid cells. Syncytia have been observed occasionally for all three betaherpesviruses, both during in vitro and in vivo infection. Since cell–cell fusion may allow efficient spread to neighboring cells without exposure to neutralizing antibodies and other host immune factors, viral-induced syncytia may be important for viral dissemination, long-term persistence, and pathogenicity. In this review, we provide an overview of the viral and cellular factors and mechanisms identified so far in the process of cell–cell fusion induced by betaherpesviruses and discuss the possible consequences for cellular dysfunction and pathogenesis.
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Affiliation(s)
- Jiajia Tang
- Leibniz Institute for Experimental Virology (HPI), 20251 Hamburg, Germany; (J.T.); (G.F.); (X.Z.); (J.K.)
- Center for Single-Cell Omics, School of Medicine, Shanghai Jiao Tong University, Shanghai 200025, China
| | - Giada Frascaroli
- Leibniz Institute for Experimental Virology (HPI), 20251 Hamburg, Germany; (J.T.); (G.F.); (X.Z.); (J.K.)
| | - Xuan Zhou
- Leibniz Institute for Experimental Virology (HPI), 20251 Hamburg, Germany; (J.T.); (G.F.); (X.Z.); (J.K.)
| | - Jan Knickmann
- Leibniz Institute for Experimental Virology (HPI), 20251 Hamburg, Germany; (J.T.); (G.F.); (X.Z.); (J.K.)
| | - Wolfram Brune
- Leibniz Institute for Experimental Virology (HPI), 20251 Hamburg, Germany; (J.T.); (G.F.); (X.Z.); (J.K.)
- Correspondence:
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12
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Gamble A, Yeo YY, Butler AA, Tang H, Snedden CE, Mason CT, Buchholz DW, Bingham J, Aguilar HC, Lloyd-Smith JO. Drivers and Distribution of Henipavirus-Induced Syncytia: What Do We Know? Viruses 2021; 13:1755. [PMID: 34578336 PMCID: PMC8472861 DOI: 10.3390/v13091755] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Revised: 08/21/2021] [Accepted: 08/25/2021] [Indexed: 12/20/2022] Open
Abstract
Syncytium formation, i.e., cell-cell fusion resulting in the formation of multinucleated cells, is a hallmark of infection by paramyxoviruses and other pathogenic viruses. This natural mechanism has historically been a diagnostic marker for paramyxovirus infection in vivo and is now widely used for the study of virus-induced membrane fusion in vitro. However, the role of syncytium formation in within-host dissemination and pathogenicity of viruses remains poorly understood. The diversity of henipaviruses and their wide host range and tissue tropism make them particularly appropriate models with which to characterize the drivers of syncytium formation and the implications for virus fitness and pathogenicity. Based on the henipavirus literature, we summarized current knowledge on the mechanisms driving syncytium formation, mostly acquired from in vitro studies, and on the in vivo distribution of syncytia. While these data suggest that syncytium formation widely occurs across henipaviruses, hosts, and tissues, we identified important data gaps that undermined our understanding of the role of syncytium formation in virus pathogenesis. Based on these observations, we propose solutions of varying complexity to fill these data gaps, from better practices in data archiving and publication for in vivo studies, to experimental approaches in vitro.
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Affiliation(s)
- Amandine Gamble
- Department of Ecology & Evolutionary Biology, University of California Los Angeles, Los Angeles, CA 90095, USA; (A.A.B.); (H.T.); (C.E.S.); (J.O.L.-S.)
| | - Yao Yu Yeo
- Department of Microbiology & Immunology, Cornell University, Ithaca, NY 14850, USA; (Y.Y.Y.); (D.W.B.); (H.C.A.)
| | - Aubrey A. Butler
- Department of Ecology & Evolutionary Biology, University of California Los Angeles, Los Angeles, CA 90095, USA; (A.A.B.); (H.T.); (C.E.S.); (J.O.L.-S.)
| | - Hubert Tang
- Department of Ecology & Evolutionary Biology, University of California Los Angeles, Los Angeles, CA 90095, USA; (A.A.B.); (H.T.); (C.E.S.); (J.O.L.-S.)
| | - Celine E. Snedden
- Department of Ecology & Evolutionary Biology, University of California Los Angeles, Los Angeles, CA 90095, USA; (A.A.B.); (H.T.); (C.E.S.); (J.O.L.-S.)
| | - Christian T. Mason
- Department of Computational Medicine, University of California Los Angeles, Los Angeles, CA 90095, USA;
| | - David W. Buchholz
- Department of Microbiology & Immunology, Cornell University, Ithaca, NY 14850, USA; (Y.Y.Y.); (D.W.B.); (H.C.A.)
| | - John Bingham
- CSIRO Australian Centre for Disease Preparedness, Geelong, VIC 3220, Australia;
| | - Hector C. Aguilar
- Department of Microbiology & Immunology, Cornell University, Ithaca, NY 14850, USA; (Y.Y.Y.); (D.W.B.); (H.C.A.)
| | - James O. Lloyd-Smith
- Department of Ecology & Evolutionary Biology, University of California Los Angeles, Los Angeles, CA 90095, USA; (A.A.B.); (H.T.); (C.E.S.); (J.O.L.-S.)
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13
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Sieler M, Weiler J, Dittmar T. Cell-Cell Fusion and the Roads to Novel Properties of Tumor Hybrid Cells. Cells 2021; 10:cells10061465. [PMID: 34207991 PMCID: PMC8230653 DOI: 10.3390/cells10061465] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Revised: 06/07/2021] [Accepted: 06/09/2021] [Indexed: 12/15/2022] Open
Abstract
The phenomenon of cancer cell–cell fusion is commonly associated with the origin of more malignant tumor cells exhibiting novel properties, such as increased drug resistance or an enhanced metastatic capacity. However, the whole process of cell–cell fusion is still not well understood and seems to be rather inefficient since only a certain number of (cancer) cells are capable of fusing and only a rather small population of fused tumor hybrids will survive at all. The low survivability of tumor hybrids is attributed to post-fusion processes, which are characterized by the random segregation of mixed parental chromosomes, the induction of aneuploidy and further random chromosomal aberrations and genetic/epigenetic alterations in daughter cells. As post-fusion processes also run in a unique manner in surviving tumor hybrids, the occurrence of novel properties could thus also be a random event, whereby it might be speculated that the tumor microenvironment and its spatial habitats could direct evolving tumor hybrids towards a specific phenotype.
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14
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Thakur N, Conceicao C, Isaacs A, Human S, Modhiran N, McLean RK, Pedrera M, Tan TK, Rijal P, Townsend A, Taylor G, Young PR, Watterson D, Chappell KJ, Graham SP, Bailey D. Micro-fusion inhibition tests: quantifying antibody neutralization of virus-mediated cell-cell fusion. J Gen Virol 2021; 102:jgv001506. [PMID: 33054904 PMCID: PMC8116787 DOI: 10.1099/jgv.0.001506] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Although enveloped viruses canonically mediate particle entry through virus-cell fusion, certain viruses can spread by cell-cell fusion, brought about by receptor engagement and triggering of membrane-bound, viral-encoded fusion proteins on the surface of cells. The formation of pathogenic syncytia or multinucleated cells is seen in vivo, but their contribution to viral pathogenesis is poorly understood. For the negative-strand paramyxoviruses respiratory syncytial virus (RSV) and Nipah virus (NiV), cell-cell spread is highly efficient because their oligomeric fusion protein complexes are active at neutral pH. The recently emerged severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has also been reported to induce syncytia formation in infected cells, with the spike protein initiating cell-cell fusion. Whilst it is well established that fusion protein-specific antibodies can block particle attachment and/or entry into the cell (canonical virus neutralization), their capacity to inhibit cell-cell fusion and the consequences of this neutralization for the control of infection are not well characterized, in part because of the lack of specific tools to assay and quantify this activity. Using an adapted bimolecular fluorescence complementation assay, based on a split GFP-Renilla luciferase reporter, we have established a micro-fusion inhibition test (mFIT) that allows the identification and quantification of these neutralizing antibodies. This assay has been optimized for high-throughput use and its applicability has been demonstrated by screening monoclonal antibody (mAb)-mediated inhibition of RSV and NiV fusion and, separately, the development of fusion-inhibitory antibodies following NiV vaccine immunization in pigs. In light of the recent emergence of coronavirus disease 2019 (COVID-19), a similar assay was developed for SARS-CoV-2 and used to screen mAbs and convalescent patient plasma for fusion-inhibitory antibodies. Using mFITs to assess antibody responses following natural infection or vaccination is favourable, as this assay can be performed entirely at low biocontainment, without the need for live virus. In addition, the repertoire of antibodies that inhibit cell-cell fusion may be different to those that inhibit particle entry, shedding light on the mechanisms underpinning antibody-mediated neutralization of viral spread.
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Affiliation(s)
- Nazia Thakur
- The Pirbright Institute, Ash Road, Pirbright, Woking, GU24 0NF, UK
| | - Carina Conceicao
- The Pirbright Institute, Ash Road, Pirbright, Woking, GU24 0NF, UK
| | - Ariel Isaacs
- University of Queensland, Brisbane, Queensland 4071, Australia
| | - Stacey Human
- The Pirbright Institute, Ash Road, Pirbright, Woking, GU24 0NF, UK
| | - Naphak Modhiran
- University of Queensland, Brisbane, Queensland 4071, Australia
| | - Rebecca K McLean
- The Pirbright Institute, Ash Road, Pirbright, Woking, GU24 0NF, UK
| | - Miriam Pedrera
- The Pirbright Institute, Ash Road, Pirbright, Woking, GU24 0NF, UK
| | - Tiong Kit Tan
- MRC Human Immunology Unit, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford OX3 9DS, UK
| | - Pramila Rijal
- MRC Human Immunology Unit, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford OX3 9DS, UK
| | - Alain Townsend
- MRC Human Immunology Unit, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford OX3 9DS, UK
| | - Geraldine Taylor
- The Pirbright Institute, Ash Road, Pirbright, Woking, GU24 0NF, UK
| | - Paul R Young
- University of Queensland, Brisbane, Queensland 4071, Australia
| | | | | | - Simon P Graham
- The Pirbright Institute, Ash Road, Pirbright, Woking, GU24 0NF, UK
| | - Dalan Bailey
- The Pirbright Institute, Ash Road, Pirbright, Woking, GU24 0NF, UK
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15
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Abstract
Cell-cell fusion is indispensable for creating life and building syncytial tissues and organs. Ever since the discovery of cell-cell fusion, how cells join together to form zygotes and multinucleated syncytia has remained a fundamental question in cell and developmental biology. In the past two decades, Drosophila myoblast fusion has been used as a powerful genetic model to unravel mechanisms underlying cell-cell fusion in vivo. Many evolutionarily conserved fusion-promoting factors have been identified and so has a surprising and conserved cellular mechanism. In this review, we revisit key findings in Drosophila myoblast fusion and highlight the critical roles of cellular invasion and resistance in driving cell membrane fusion.
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Affiliation(s)
- Donghoon M Lee
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA;
| | - Elizabeth H Chen
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA;
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
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16
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Whitaker EE, Matheson NJ, Perlee S, Munson PB, Symeonides M, Thali M. EWI-2 Inhibits Cell-Cell Fusion at the HIV-1 Virological Presynapse. Viruses 2019; 11:E1082. [PMID: 31757023 DOI: 10.3390/v11121082] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Revised: 11/14/2019] [Accepted: 11/16/2019] [Indexed: 12/13/2022] Open
Abstract
Cell-to-cell transfer of virus particles at the Env-dependent virological synapse (VS) is a highly efficient mode of HIV-1 transmission. While cell–cell fusion could be triggered at the VS, leading to the formation of syncytia and preventing exponential growth of the infected cell population, this is strongly inhibited by both viral (Gag) and host (ezrin and tetraspanins) proteins. Here, we identify EWI-2, a protein that was previously shown to associate with ezrin and tetraspanins, as a host factor that contributes to the inhibition of Env-mediated cell–cell fusion. Using quantitative fluorescence microscopy, shRNA knockdowns, and cell–cell fusion assays, we show that EWI-2 accumulates at the presynaptic terminal (i.e., the producer cell side of the VS), where it contributes to the fusion-preventing activities of the other viral and cellular components. We also find that EWI-2, like tetraspanins, is downregulated upon HIV-1 infection, most likely by Vpu. Despite the strong inhibition of fusion at the VS, T cell-based syncytia do form in vivo and in physiologically relevant culture systems, but they remain small. In regard to that, we demonstrate that EWI-2 and CD81 levels are restored on the surface of syncytia, where they (presumably) continue to act as fusion inhibitors. This study documents a new role for EWI-2 as an inhibitor of HIV-1-induced cell–cell fusion and provides novel insight into how syncytia are prevented from fusing indefinitely.
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17
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Qiu J, Liang T, Wu J, Yu F, He X, Tian Y, Xie L, Jiang S, Liu S, Li L. N-Substituted Pyrrole Derivative 12m Inhibits HIV-1 Entry by Targeting Gp41 of HIV-1 Envelope Glycoprotein. Front Pharmacol 2019; 10:859. [PMID: 31427969 PMCID: PMC6688628 DOI: 10.3389/fphar.2019.00859] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Accepted: 07/05/2019] [Indexed: 11/13/2022] Open
Abstract
The combination of three or more antiviral agents that act on different targets is known as highly active antiretroviral therapy (HAART), which is widely used to control HIV infection. However, because drug resistance and adverse effects occur after long-term administration, an increasing number of HIV/AIDS patients do not tolerate HAART. It is necessary to continue developing novel anti-HIV drugs, particularly HIV entry/fusion inhibitors. Our group previously identified a small-molecule compound, NB-64, with weak anti-HIV activity. Here, we found that N-substituted pyrrole derivative 12m (NSPD-12m), which was derived from NB-64, had strong anti-HIV-1 activity, and NSPD-12m-treated cells showed good viability. The mechanism of action of NSPD-12m might be targeting the gp41 transmembrane subunit of the HIV envelope glycoprotein, thus inhibiting HIV entry. Site-directed mutagenesis confirmed that a positively charged lysine residue (K574) located in the gp41 pocket region is pivotal for the binding of NSPD-12m to gp41. These findings suggest that NSPD-12m can serve as a lead compound to develop novel virus entry inhibitors.
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Affiliation(s)
- Jiayin Qiu
- Guangdong Provincial Key Laboratory of New Drug Screening, Guangzhou Key Laboratory of Drug Research for Emerging Virus Prevention and Treatment, School of Pharmaceutical Sciences, Southern Medical University, Guangzhou, China.,School of Pharmaceutical Science, Zhejiang Chinese Medical University, Hangzhou, China.,Department of Pharmacy, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China
| | - Taizhen Liang
- Guangdong Provincial Key Laboratory of New Drug Screening, Guangzhou Key Laboratory of Drug Research for Emerging Virus Prevention and Treatment, School of Pharmaceutical Sciences, Southern Medical University, Guangzhou, China
| | - Junyan Wu
- Department of Pharmacy, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China
| | - Fei Yu
- College of Life Sciences, Agricultural University of Hebei, Baoding, China.,Key Laboratory of Medical Molecular Virology of Ministries of Education and Health, Shanghai Medical College, Fudan University, Shanghai, China
| | - Xiaoyang He
- Beijing Institute of Pharmacology and Toxicology, Beijing, China
| | - Yuanxin Tian
- Guangdong Provincial Key Laboratory of New Drug Screening, Guangzhou Key Laboratory of Drug Research for Emerging Virus Prevention and Treatment, School of Pharmaceutical Sciences, Southern Medical University, Guangzhou, China
| | - Lan Xie
- Beijing Institute of Pharmacology and Toxicology, Beijing, China
| | - Shibo Jiang
- Key Laboratory of Medical Molecular Virology of Ministries of Education and Health, Shanghai Medical College, Fudan University, Shanghai, China
| | - Shuwen Liu
- Guangdong Provincial Key Laboratory of New Drug Screening, Guangzhou Key Laboratory of Drug Research for Emerging Virus Prevention and Treatment, School of Pharmaceutical Sciences, Southern Medical University, Guangzhou, China
| | - Lin Li
- Guangdong Provincial Key Laboratory of New Drug Screening, Guangzhou Key Laboratory of Drug Research for Emerging Virus Prevention and Treatment, School of Pharmaceutical Sciences, Southern Medical University, Guangzhou, China
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18
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Abstract
Myosin II and spectrin β display mechanosensitive accumulations in invasive protrusions during cell-cell fusion of Drosophila myoblasts. The biochemical inhibition and deactivation of these proteins results in significant fusion defects. Yet, a quantitative understanding of how the protrusion geometry and fusion process are linked to these proteins is still lacking. Here we present a quantitative model to interpret the dependence of the protrusion size and the protrusive force on the mechanical properties and microstructures of the actin cytoskeleton and plasma membrane based on a mean-field theory. We build a quantitative linkage between mechanosensitive accumulation of myosin II and fusion pore formation at the tip of the invasive protrusion through local area dilation. The mechanical feedback loop between myosin II and local deformation suggests that myosin II accumulation possibly reduces the energy barrier and the critical radius of fusion pores. We also analyse the effect of spectrin β on maintaining the proper geometry of the protrusions required for the success of cell-cell fusion.
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Affiliation(s)
- Jing Cong
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei, People's Republic of China
| | - Bing Fang
- College of Mechanical and Electronic Engineering, Fujian Agriculture and Forestry University, Fuzhou 350002, People's Republic of China
| | - Qian Wang
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei, People's Republic of China
| | - Yan Su
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei, People's Republic of China
| | - Tianqi Gu
- College of Mechanical Engineering and Automation, Fuzhou University, Fuzhou 350108, People's Republic of China
| | - Tianzhi Luo
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei, People's Republic of China
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19
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Podolnikova NP, Hlavackova M, Wu Y, Yakubenko VP, Faust J, Balabiyev A, Wang X, Ugarova TP. Interaction between the integrin Mac-1 and signal regulatory protein α (SIRPα) mediates fusion in heterologous cells. J Biol Chem 2019; 294:7833-7849. [PMID: 30910815 DOI: 10.1074/jbc.ra118.006314] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Revised: 03/15/2019] [Indexed: 12/11/2022] Open
Abstract
Macrophage fusion leading to the formation of multinucleated giant cells is a hallmark of chronic inflammation. Several membrane proteins have been implicated in mediating cell-cell attachment during fusion, but their binding partners remain unknown. Recently, we demonstrated that interleukin-4 (IL-4)-induced fusion of mouse macrophages depends on the integrin macrophage antigen 1 (Mac-1). Surprisingly, the genetic deficiency of intercellular adhesion molecule 1 (ICAM-1), an established ligand of Mac-1, did not impair macrophage fusion, suggesting the involvement of other counter-receptors. Here, using various approaches, including signal regulatory protein α (SIRPα) knockdown, recombinant proteins, adhesion and fusion assays, biolayer interferometry, and peptide libraries, we show that SIRPα, which, similar to ICAM-1, belongs to the Ig superfamily and has previously been implicated in cell fusion, interacts with Mac-1. The following results support the conclusion that SIRPα is a ligand of Mac-1: (a) recombinant ectodomain of SIRPα supports adhesion of Mac-1-expressing cells; (b) Mac-1-SIRPα interaction is mediated through the ligand-binding αMI-domain of Mac-1; (c) recognition of SIRPα by the αMI-domain conforms to general principles governing binding of Mac-1 to many of its ligands; (d) SIRPα reportedly binds CD47; however, anti-CD47 function-blocking mAb produced only a limited inhibition of macrophage adhesion to SIRPα; and (e) co-culturing of SIRPα- and Mac-1-expressing HEK293 cells resulted in the formation of multinucleated cells. Taken together, these results identify SIRPα as a counter-receptor for Mac-1 and suggest that the Mac-1-SIRPα interaction may be involved in macrophage fusion.
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Affiliation(s)
- Nataly P Podolnikova
- From the Center for Metabolic and Vascular Biology, School of Life Sciences, and
| | - Marketa Hlavackova
- From the Center for Metabolic and Vascular Biology, School of Life Sciences, and
| | - Yifei Wu
- From the Center for Metabolic and Vascular Biology, School of Life Sciences, and
| | - Valentin P Yakubenko
- the College of Medicine, East Tennessee State University, Johnson City, Tennessee 37614
| | - James Faust
- From the Center for Metabolic and Vascular Biology, School of Life Sciences, and
| | - Arnat Balabiyev
- From the Center for Metabolic and Vascular Biology, School of Life Sciences, and
| | - Xu Wang
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287 and
| | - Tatiana P Ugarova
- From the Center for Metabolic and Vascular Biology, School of Life Sciences, and
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20
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Wanitchang A, Saenboonrueng J, Kaewborisuth C, Srisutthisamphan K, Jongkaewwattana A. A Single V672F Substitution in the Spike Protein of Field-Isolated PEDV Promotes Cell⁻Cell Fusion and Replication in VeroE6 Cells. Viruses 2019; 11:v11030282. [PMID: 30897856 PMCID: PMC6466060 DOI: 10.3390/v11030282] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Revised: 03/15/2019] [Accepted: 03/19/2019] [Indexed: 02/07/2023] Open
Abstract
While porcine epidemic diarrhea virus (PEDV) infects and replicates in enterocytes lining villi of neonatal piglets with high efficiency, naturally isolated variants typically grow poorly in established cell lines, unless adapted by multiple passages. Cells infected with most cell-adapted PEDVs usually displayed large syncytia, a process triggered by the spike protein (S). To identify amino acids responsible for S-mediated syncytium formation, we constructed and characterized chimeric S proteins of the cell-adapted variant, YN144, in which the receptor binding domain (RBD) and S1/S2 cleavage site were replaced with those of a poorly culturable field isolate (G2). We demonstrated that the RBD, not the S1/S2 cleavage site, is critical for syncytium formation mediated by chimeric S proteins. Further mutational analyses revealed that a single mutation at the amino acid residue position 672 (V672F) could enable the chimeric S with the entire RBD derived from the G2 strain to trigger large syncytia. Moreover, recombinant PEDV viruses bearing S of the G2 strain with the single V672F substitution could induce extensive syncytium formation and replicate efficiently in VeroE6 cells stably expressing porcine aminopeptidase N (VeroE6-APN). Interestingly, we also demonstrated that while the V672F mutation is critical for the syncytium formation in VeroE6-APN cells, it exerts a minimal effect in Huh-7 cells, thereby suggesting the difference in receptor preference of PEDV among host cells.
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Affiliation(s)
- Asawin Wanitchang
- Virology and Cell Technology Laboratory, National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency (NSTDA), Pathumthani 12120, Thailand.
| | - Janya Saenboonrueng
- Virology and Cell Technology Laboratory, National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency (NSTDA), Pathumthani 12120, Thailand.
| | - Challika Kaewborisuth
- Virology and Cell Technology Laboratory, National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency (NSTDA), Pathumthani 12120, Thailand.
| | - Kanjana Srisutthisamphan
- Virology and Cell Technology Laboratory, National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency (NSTDA), Pathumthani 12120, Thailand.
| | - Anan Jongkaewwattana
- Virology and Cell Technology Laboratory, National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency (NSTDA), Pathumthani 12120, Thailand.
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21
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Xia S, Lan Q, Pu J, Wang C, Liu Z, Xu W, Wang Q, Liu H, Jiang S, Lu L. Potent MERS-CoV Fusion Inhibitory Peptides Identified from HR2 Domain in Spike Protein of Bat Coronavirus HKU4. Viruses 2019; 11:E56. [PMID: 30646495 DOI: 10.3390/v11010056] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Revised: 01/02/2019] [Accepted: 01/10/2019] [Indexed: 12/31/2022] Open
Abstract
The Middle East respiratory syndrome coronavirus (MERS-CoV) emerged in 2012 and caused continual outbreaks worldwide with high mortality. However, no effective anti-MERS-CoV drug is currently available. Recently, numerous evolutionary studies have suggested that MERS-CoV originated from bat coronavirus (BatCoV). We herein reported that three peptides derived from the HR2 region in spike protein of BatCoV HKU4, including HKU4-HR2P1, HKU4-HR2P2 and HKU4-HR2P3, could bind the MERS-CoV HR1-derived peptide to form a six-helix bundle (6-HB) with high stability. Moreover, these peptides, particularly HKU4-HR2P2 and HKU4-HR2P3, exhibited potent inhibitory activity against MERS-CoV S-mediated cell–cell fusion and viral infection, suggesting that these HKU4 HR2-derived peptides could be candidates for futher development as antiviral agents against MERS-CoV infection.
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22
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Tsurudome M, Ohtsuka J, Ito M, Nishio M, Nosaka T. The Hemagglutinin-Neuraminidase (HN) Head Domain and the Fusion (F) Protein Stalk Domain of the Parainfluenza Viruses Affect the Specificity of the HN-F Interaction. Front Microbiol 2018; 9:391. [PMID: 29593671 PMCID: PMC5859044 DOI: 10.3389/fmicb.2018.00391] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Accepted: 02/21/2018] [Indexed: 12/31/2022] Open
Abstract
Membrane fusion by the parainfluenza viruses is induced by virus-specific functional interaction between the attachment protein (HN) and the fusion (F) protein. This interaction is thought to be mediated by transient contacts between particular amino acids in the HN stalk domain and those in the F head domain. However, we recently reported that replacement of specified amino acids at or around the dimer interface of the HN head domain remarkably affected the F protein specificity. We then intended to further investigate this issue in the present study and revealed that the HPIV2 HN protein can be converted to an SV41 HN-like protein by substituting at least nine amino acids in the HPIV2 HN head domain with the SV41 HN counterparts in addition to the replacement of the stalk domain, indicating that specified amino acids in the HN head domain play very important roles in determining the specificity of the HN-F interaction. On the other hand, we previously reported that the PIV5 F protein can be converted to an SV41 F-like protein by replacing 21 amino acids in the head domain of the PIV5 F protein with those of the SV41 F protein. We then intended to further investigate this issue in the present study and found that replacement of 15 amino acids in the stalk domain in addition to the replacement of the 21 amino acids in the head domain of the PIV5 F protein resulted in creation of a more SV41 F-like protein, indicating that specified amino acids in the F stalk domain play important roles in determining the specificity of the HN-F interaction. These results suggest that the conformations of the HN stalk domain and the F head domain are dependent on the structures of the HN head domain and the F stalk domain, respectively. Presumably, the conformations of the former domains, which are considered directly involved in the HN-F interaction, can be modified by subtle changes in the structure of the latter domains, resulting in an altered specificity for the interacting partners.
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Affiliation(s)
- Masato Tsurudome
- Department of Microbiology and Molecular Genetics, Graduate School of Medicine, Mie University, Tsu, Japan
| | - Junpei Ohtsuka
- Department of Microbiology and Molecular Genetics, Graduate School of Medicine, Mie University, Tsu, Japan
| | - Morihiro Ito
- Department of Biomedical Sciences, College of Life and Health Sciences, Chubu University, Kasugai, Japan
| | - Machiko Nishio
- Department of Microbiology, Wakayama Medical University, Wakayama, Japan
| | - Tetsuya Nosaka
- Department of Microbiology and Molecular Genetics, Graduate School of Medicine, Mie University, Tsu, Japan
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23
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Dudin O, Merlini L, Martin SG. Spatial focalization of pheromone/MAPK signaling triggers commitment to cell-cell fusion. Genes Dev 2017; 30:2226-2239. [PMID: 27798845 PMCID: PMC5088570 DOI: 10.1101/gad.286922.116] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Accepted: 09/21/2016] [Indexed: 12/14/2022]
Abstract
Here, Dudin et al. show that cell fusion does not require a dedicated signal but is triggered by spatial focalization of the same pheromone–GPCR–MAPK signaling cascade that drives earlier mating events in Schizosaccharomyces pombe. Cell fusion is universal in eukaryotes for fertilization and development, but what signals this process is unknown. Here, we show in Schizosaccharomyces pombe that fusion does not require a dedicated signal but is triggered by spatial focalization of the same pheromone–GPCR (G-protein-coupled receptor)–MAPK signaling cascade that drives earlier mating events. Autocrine cells expressing the receptor for their own pheromone trigger fusion attempts independently of cell–cell contact by concentrating pheromone release at the fusion focus, a dynamic actin aster underlying the secretion of cell wall hydrolases. Pheromone receptor and MAPK cascade are similarly enriched at the fusion focus, concomitant with fusion commitment in wild-type mating pairs. This focalization promotes cell fusion by immobilizing the fusion focus, thus driving local cell wall dissolution. We propose that fusion commitment is imposed by a local increase in MAPK concentration at the fusion focus, driven by a positive feedback between fusion focus formation and focalization of pheromone release and perception.
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Affiliation(s)
- Omaya Dudin
- Department of Fundamental Microbiology, University of Lausanne, CH-1015 Lausanne, Switzerland
| | - Laura Merlini
- Department of Fundamental Microbiology, University of Lausanne, CH-1015 Lausanne, Switzerland
| | - Sophie G Martin
- Department of Fundamental Microbiology, University of Lausanne, CH-1015 Lausanne, Switzerland
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24
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Ciechonska M, Duncan R. Reovirus FAST proteins: virus-encoded cellular fusogens. Trends Microbiol 2014; 22:715-24. [PMID: 25245455 DOI: 10.1016/j.tim.2014.08.005] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2014] [Revised: 08/06/2014] [Accepted: 08/08/2014] [Indexed: 10/24/2022]
Abstract
Reovirus fusion-associated small transmembrane (FAST) proteins are the only known nonenveloped virus fusogens and are dedicated to inducing cell-to-cell, not virus-cell, membrane fusion. Numerous structural and functional attributes distinguish this novel family of viral fusogens from all enveloped virus membrane fusion proteins. Both families of viral fusogens play key roles in virus dissemination and pathogenicity, but employ different mechanisms to mediate membrane apposition and merger. However, convergence of these distinct families of viral membrane fusion proteins on common pathways needed for pore expansion and syncytium formation suggests syncytiogenesis represents a cellular response to the presence of cell-cell fusion pores. Together, FAST proteins and enveloped virus fusion proteins provide exceptional insights into the ubiquitous process of cell-cell membrane fusion and syncytium formation.
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Affiliation(s)
- Marta Ciechonska
- Department of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada
| | - Roy Duncan
- Department of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada; Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada; Department of Pediatrics, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada.
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25
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Lavialle C, Cornelis G, Dupressoir A, Esnault C, Heidmann O, Vernochet C, Heidmann T. Paleovirology of 'syncytins', retroviral env genes exapted for a role in placentation. Philos Trans R Soc Lond B Biol Sci 2013; 368:20120507. [PMID: 23938756 DOI: 10.1098/rstb.2012.0507] [Citation(s) in RCA: 249] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The development of the emerging field of 'paleovirology' allows biologists to reconstruct the evolutionary history of fossil endogenous retroviral sequences integrated within the genome of living organisms and has led to the retrieval of conserved, ancient retroviral genes 'exapted' by ancestral hosts to fulfil essential physiological roles, syncytin genes being undoubtedly among the most remarkable examples of such a phenomenon. Indeed, syncytins are 'new' genes encoding proteins derived from the envelope protein of endogenous retroviral elements that have been captured and domesticated on multiple occasions and independently in diverse mammalian species, through a process of convergent evolution. Knockout of syncytin genes in mice provided evidence for their absolute requirement for placenta development and embryo survival, via formation by cell-cell fusion of syncytial cell layers at the fetal-maternal interface. These genes of exogenous origin, acquired 'by chance' and yet still 'necessary' to carry out a basic function in placental mammals, may have been pivotal in the emergence of mammalian ancestors with a placenta from egg-laying animals via the capture of a founding retroviral env gene, subsequently replaced in the diverse mammalian lineages by new env-derived syncytin genes, each providing its host with a positive selective advantage.
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Affiliation(s)
- Christian Lavialle
- UMR 8122, Unité des Rétrovirus Endogènes et Éléments Rétroïdes des Eucaryotes Supérieurs, CNRS, Institut Gustave Roussy, , 94805 Villejuif, France
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26
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Chang CW, Cheong ML, Chang GD, Tsai MS, Chen H. Involvement of Epac1/Rap1/CaMKI/HDAC5 signaling cascade in the regulation of placental cell fusion. Mol Hum Reprod 2013; 19:745-55. [PMID: 23867755 DOI: 10.1093/molehr/gat050] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The placental transcription factor glial cell missing 1 (GCM1) and its target gene syncytin-1 are involved in cAMP-stimulated trophoblastic fusion for syncytiotrophoblast formation. GCM1 DNA-binding activity is inhibited by sumoylation, whereas GCM1 stability is decreased by deacetylation. cAMP enhances GCM1 desumoylation through the Epac1/Rap1/CaMKI signaling cascade and CaMKI is known to down-regulate class IIa HDAC activity. In this paper, we study whether the Epac1/Rap1/CaMKI signaling cascade regulates GCM1 activity and placental cell fusion through class IIa HDACs. Interaction and co-localization of GCM1 and HDAC5 were characterized by co-immunoprecipitation analysis and immunofluorescence microscopy (IFM). Regulation of GCM1 transcription activity and syncytin-1 expression by HDAC5 was studied by transient expression. Phospho-specific antibodies against HDAC5, RNA interference and IFM were used to examine the de-repression of GCM1 activity, syncytin-1 expression and cell-cell fusion by Epac1/Rap1/CaMKI signaling cascade in placental BeWo cells expressing constitutively active Epac1 and CaMKI. We demonstrate that both GCM1 and HDAC5 are expressed in the syncytiotrophoblast layer of full-term placenta and the nuclei of BeWo cells. The interaction between HDAC5 and GCM1 facilitates GCM1 deacetylation and suppresses its transcriptional activity. In contrast, Epac1 stimulates HDAC5 phosphorylation on Ser259 and Ser498 in a Rap1- and CaMKI-dependent manner leading to nuclear export of HDAC5 and thereby de-repression of GCM1 transcriptional activity. Importantly, HDAC5 suppresses syncytin-1 expression and cell-cell fusion in BeWo cells, which is counteracted by Epac1 and CaMKI. Our results reveal a new layer of regulation of GCM1 activity and placental cell fusion through the Epac1/Rap1/CaMKI signaling cascade by restraining HDAC5 from interacting with and mediating GCM1 deacetylation.
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Affiliation(s)
- Ching-Wen Chang
- Institute of Biological Chemistry, Academia Sinica, Nankang, Taipei 115, Taiwan
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27
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Abstract
Macrophages play a pivotal role in host defense against multiple foreign materials such as bacteria, parasites and artificial devices. Some macrophage lineage cells, namely osteoclasts and foreign body giant cells (FBGCs), form multi-nuclear giant cells by the cell-cell fusion of mono-nuclear cells. Osteoclasts are bone-resorbing cells, and are formed in the presence of RANKL on the surface of bones, while FBGCs are formed in the presence of IL-4 or IL-13 on foreign materials such as artificial joints, catheters and parasites. Recently, fusiogenic mechanisms and the molecules required for the cell-cell fusion of these macrophage lineage cells were, at least in part, clarified. Dendritic cell specific transmembrane protein (DC-STAMP) and osteoclast stimulatory transmembrane protein (OC-STAMP), both of which comprise seven transmembrane domains, are required for both osteoclast and FBGC cell-cell fusion. STAT6 was demonstrated to be required for the cell-cell fusion of FBGCs but not osteoclasts. In this review, advances in macrophage cell-cell fusion are discussed.
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Affiliation(s)
- Takeshi Miyamoto
- Department of Orthopedic Surgery; Department of Integrated Bone Metabolism and Immunology; Keio Kanrinmaru Project; Keio University School of Medicine; Tokyo, Japan
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