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Lubinski B, Whittaker GR. Host Cell Proteases Involved in Human Respiratory Viral Infections and Their Inhibitors: A Review. Viruses 2024; 16:984. [PMID: 38932275 PMCID: PMC11209347 DOI: 10.3390/v16060984] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2024] [Revised: 06/06/2024] [Accepted: 06/11/2024] [Indexed: 06/28/2024] Open
Abstract
Viral tropism is most commonly linked to receptor use, but host cell protease use can be a notable factor in susceptibility to infection. Here we review the use of host cell proteases by human viruses, focusing on those with primarily respiratory tropism, particularly SARS-CoV-2. We first describe the various classes of proteases present in the respiratory tract, as well as elsewhere in the body, and incorporate the targeting of these proteases as therapeutic drugs for use in humans. Host cell proteases are also linked to the systemic spread of viruses and play important roles outside of the respiratory tract; therefore, we address how proteases affect viruses across the spectrum of infections that can occur in humans, intending to understand the extrapulmonary spread of SARS-CoV-2.
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Affiliation(s)
- Bailey Lubinski
- Department of Microbiology & Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14850, USA;
| | - Gary R. Whittaker
- Department of Microbiology & Immunology and Public & Ecosystem Health, College of Veterinary Medicine, Cornell University, Ithaca, NY 14850, USA
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Shi Q, Zhao R, Chen L, Liu T, Di T, Zhang C, Zhang Z, Wang F, Han Z, Sun J, Liu S. Newcastle disease virus activates diverse signaling pathways via Src to facilitate virus entry into host macrophages. J Virol 2024; 98:e0191523. [PMID: 38334327 PMCID: PMC10949470 DOI: 10.1128/jvi.01915-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2023] [Accepted: 12/27/2023] [Indexed: 02/10/2024] Open
Abstract
As an intrinsic cellular mechanism responsible for the internalization of extracellular ligands and membrane components, caveolae-mediated endocytosis (CavME) is also exploited by certain pathogens for endocytic entry [e.g., Newcastle disease virus (NDV) of paramyxovirus]. However, the molecular mechanisms of NDV-induced CavME remain poorly understood. Herein, we demonstrate that sialic acid-containing gangliosides, rather than glycoproteins, were utilized by NDV as receptors to initiate the endocytic entry of NDV into HD11 cells. The binding of NDV to gangliosides induced the activation of a non-receptor tyrosine kinase, Src, leading to the phosphorylation of caveolin-1 (Cav1) and dynamin-2 (Dyn2), which contributed to the endocytic entry of NDV. Moreover, an inoculation of cells with NDV-induced actin cytoskeletal rearrangement through Src to facilitate NDV entry via endocytosis and direct fusion with the plasma membrane. Subsequently, unique members of the Rho GTPases family, RhoA and Cdc42, were activated by NDV in a Src-dependent manner. Further analyses revealed that RhoA and Cdc42 regulated the activities of specific effectors, cofilin and myosin regulatory light chain 2, responsible for actin cytoskeleton rearrangement, through diverse intracellular signaling cascades. Taken together, our results suggest that an inoculation of NDV-induced Src-mediated cellular activation by binding to ganglioside receptors. This process orchestrated NDV endocytic entry by modulating the activities of caveolae-associated Cav1 and Dyn2, as well as specific Rho GTPases and downstream effectors. IMPORTANCE In general, it is known that the paramyxovirus gains access to host cells through direct penetration at the plasma membrane; however, emerging evidence suggests more complex entry mechanisms for paramyxoviruses. The endocytic entry of Newcastle disease virus (NDV), a representative member of the paramyxovirus family, into multiple types of cells has been recently reported. Herein, we demonstrate the binding of NDV to induce ganglioside-activated Src signaling, which is responsible for the endocytic entry of NDV through caveolae-mediated endocytosis. This process involved Src-dependent activation of the caveolae-associated Cav1 and Dyn2, as well as specific Rho GTPase and downstream effectors, thereby orchestrating the endocytic entry process of NDV. Our findings uncover a novel molecular mechanism of endocytic entry of NDV into host cells and provide novel insight into paramyxovirus mechanisms of entry.
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Affiliation(s)
- Qiankai Shi
- Division of Avian Infectious Diseases, State Key Laboratory of Animal Disease Control and Prevention, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin, China
| | - Ran Zhao
- Division of Avian Infectious Diseases, State Key Laboratory of Animal Disease Control and Prevention, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin, China
| | - Linna Chen
- Division of Avian Infectious Diseases, State Key Laboratory of Animal Disease Control and Prevention, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin, China
| | - Tianyi Liu
- Division of Avian Infectious Diseases, State Key Laboratory of Animal Disease Control and Prevention, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin, China
| | - Tao Di
- Division of Avian Infectious Diseases, State Key Laboratory of Animal Disease Control and Prevention, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin, China
| | - Chunwei Zhang
- Division of Avian Infectious Diseases, State Key Laboratory of Animal Disease Control and Prevention, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin, China
| | - Zhiying Zhang
- Division of Avian Infectious Diseases, State Key Laboratory of Animal Disease Control and Prevention, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin, China
| | - Fangfang Wang
- Division of Avian Infectious Diseases, State Key Laboratory of Animal Disease Control and Prevention, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin, China
| | - Zongxi Han
- Division of Avian Infectious Diseases, State Key Laboratory of Animal Disease Control and Prevention, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin, China
| | - Junfeng Sun
- Division of Avian Infectious Diseases, State Key Laboratory of Animal Disease Control and Prevention, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin, China
| | - Shengwang Liu
- Division of Avian Infectious Diseases, State Key Laboratory of Animal Disease Control and Prevention, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin, China
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Chen Y, Zhu S, Liao T, Wang C, Han J, Yang Z, Lu X, Hu Z, Hu J, Wang X, Gu M, Gao R, Liu K, Liu X, Ding C, Hu S, Liu X. The HN protein of Newcastle disease virus induces cell apoptosis through the induction of lysosomal membrane permeabilization. PLoS Pathog 2024; 20:e1011981. [PMID: 38354122 PMCID: PMC10866534 DOI: 10.1371/journal.ppat.1011981] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Accepted: 01/17/2024] [Indexed: 02/16/2024] Open
Abstract
Lysosomes are acidic organelles that mediate the degradation and recycling of cellular waste materials. Damage to lysosomes can cause lysosomal membrane permeabilization (LMP) and trigger different types of cell death, including apoptosis. Newcastle disease virus (NDV) can naturally infect most birds. Additionally, it serves as a promising oncolytic virus known for its effective infection of tumor cells and induction of intensive apoptotic responses. However, the involvement of lysosomes in NDV-induced apoptosis remains poorly understood. Here, we demonstrate that NDV infection profoundly triggers LMP, leading to the translocation of cathepsin B and D and subsequent mitochondria-dependent apoptosis in various tumor and avian cells. Notably, the released cathepsin B and D exacerbate NDV-induced LMP by inducing the generation of reactive oxygen species. Additionally, we uncover that the viral Hemagglutinin neuraminidase (HN) protein induces the deglycosylation and degradation of lysosome-associated membrane protein 1 (LAMP1) and LAMP2 dependent on its sialidase activity, which finally contributes to NDV-induced LMP and cellular apoptosis. Overall, our findings elucidate the role of LMP in NDV-induced cell apoptosis and provide novel insights into the function of HN during NDV-induced LMP, which provide innovative approaches for the development of NDV-based oncolytic agents.
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Affiliation(s)
- Yu Chen
- Animal Infectious Disease Laboratory, College of Veterinary Medicine, Yangzhou University; Yangzhou, Jiangsu, China
- Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, China
- Jiangsu Key Laboratory of Zoonosis, Yangzhou University, Yangzhou, China
| | - Shanshan Zhu
- Animal Infectious Disease Laboratory, College of Veterinary Medicine, Yangzhou University; Yangzhou, Jiangsu, China
| | - Tianxing Liao
- Animal Infectious Disease Laboratory, College of Veterinary Medicine, Yangzhou University; Yangzhou, Jiangsu, China
| | - Chunxuan Wang
- Animal Infectious Disease Laboratory, College of Veterinary Medicine, Yangzhou University; Yangzhou, Jiangsu, China
| | - Jiajun Han
- Animal Infectious Disease Laboratory, College of Veterinary Medicine, Yangzhou University; Yangzhou, Jiangsu, China
| | - Zhenyu Yang
- Animal Infectious Disease Laboratory, College of Veterinary Medicine, Yangzhou University; Yangzhou, Jiangsu, China
| | - Xiaolong Lu
- Animal Infectious Disease Laboratory, College of Veterinary Medicine, Yangzhou University; Yangzhou, Jiangsu, China
- Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, China
- Jiangsu Key Laboratory of Zoonosis, Yangzhou University, Yangzhou, China
| | - Zenglei Hu
- Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, China
- Joint International Research Laboratory of Agriculture and Agri-Product Safety, The Ministry of Education of China, Yangzhou University, Yangzhou, China
| | - Jiao Hu
- Animal Infectious Disease Laboratory, College of Veterinary Medicine, Yangzhou University; Yangzhou, Jiangsu, China
- Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, China
- Jiangsu Key Laboratory of Zoonosis, Yangzhou University, Yangzhou, China
| | - Xiaoquan Wang
- Animal Infectious Disease Laboratory, College of Veterinary Medicine, Yangzhou University; Yangzhou, Jiangsu, China
- Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, China
- Jiangsu Key Laboratory of Zoonosis, Yangzhou University, Yangzhou, China
| | - Min Gu
- Animal Infectious Disease Laboratory, College of Veterinary Medicine, Yangzhou University; Yangzhou, Jiangsu, China
- Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, China
- Jiangsu Key Laboratory of Zoonosis, Yangzhou University, Yangzhou, China
| | - Ruyi Gao
- Animal Infectious Disease Laboratory, College of Veterinary Medicine, Yangzhou University; Yangzhou, Jiangsu, China
- Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, China
- Jiangsu Key Laboratory of Zoonosis, Yangzhou University, Yangzhou, China
| | - Kaituo Liu
- Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, China
- Joint International Research Laboratory of Agriculture and Agri-Product Safety, The Ministry of Education of China, Yangzhou University, Yangzhou, China
| | - Xiaowen Liu
- Animal Infectious Disease Laboratory, College of Veterinary Medicine, Yangzhou University; Yangzhou, Jiangsu, China
- Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, China
- Jiangsu Key Laboratory of Zoonosis, Yangzhou University, Yangzhou, China
| | - Chan Ding
- Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, China
- Department of Avian Infectious Diseases, Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, China
| | - Shunlin Hu
- Animal Infectious Disease Laboratory, College of Veterinary Medicine, Yangzhou University; Yangzhou, Jiangsu, China
- Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, China
- Jiangsu Key Laboratory of Zoonosis, Yangzhou University, Yangzhou, China
| | - Xiufan Liu
- Animal Infectious Disease Laboratory, College of Veterinary Medicine, Yangzhou University; Yangzhou, Jiangsu, China
- Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, China
- Jiangsu Key Laboratory of Zoonosis, Yangzhou University, Yangzhou, China
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FeMV is a cathepsin-dependent unique morbillivirus infecting the kidneys of domestic cats. Proc Natl Acad Sci U S A 2022; 119:e2209405119. [PMID: 36251995 PMCID: PMC9618091 DOI: 10.1073/pnas.2209405119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Feline morbillivirus (FeMV) is a recently discovered pathogen of domestic cats and has been classified as a morbillivirus in the Paramyxovirus family. We determined the complete sequence of FeMVUS5 directly from an FeMV-positive urine sample without virus isolation or cell passage. Sequence analysis of the viral genome revealed potential divergence from characteristics of archetypal morbilliviruses. First, the virus lacks the canonical polybasic furin cleavage signal in the fusion (F) glycoprotein. Second, conserved amino acids in the hemagglutinin (H) glycoprotein used by all other morbilliviruses for binding and/or fusion activation with the cellular receptor CD150 (signaling lymphocyte activation molecule [SLAM]/F1) are absent. We show that, despite this sequence divergence, FeMV H glycoprotein uses feline CD150 as a receptor and cannot use human CD150. We demonstrate that the protease responsible for cleaving the FeMV F glycoprotein is a cathepsin, making FeMV a unique morbillivirus and more similar to the closely related zoonotic Nipah and Hendra viruses. We developed a reverse genetics system for FeMVUS5 and generated recombinant viruses expressing Venus fluorescent protein from an additional transcription unit located either between the phospho-protein (P) and matrix (M) genes or the H and large (L) genes of the genome. We used these recombinant FeMVs to establish a natural infection and demonstrate that FeMV causes an acute morbillivirus-like disease in the cat. Virus was shed in the urine and detectable in the kidneys at later time points. This opens the door for long-term studies to address the postulated role of this morbillivirus in the development of chronic kidney disease.
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The Key Role of Lysosomal Protease Cathepsins in Viral Infections. Int J Mol Sci 2022; 23:ijms23169089. [PMID: 36012353 PMCID: PMC9409221 DOI: 10.3390/ijms23169089] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2022] [Revised: 08/10/2022] [Accepted: 08/12/2022] [Indexed: 11/17/2022] Open
Abstract
Cathepsins encompass a family of lysosomal proteases that mediate protein degradation and turnover. Although mainly localized in the endolysosomal compartment, cathepsins are also found in the cytoplasm, nucleus, and extracellular space, where they are involved in cell signaling, extracellular matrix assembly/disassembly, and protein processing and trafficking through the plasma and nuclear membrane and between intracellular organelles. Ubiquitously expressed in the body, cathepsins play regulatory roles in a wide range of physiological processes including coagulation, hormone secretion, immune responses, and others. A dysregulation of cathepsin expression and/or activity has been associated with many human diseases, including cancer, diabetes, obesity, cardiovascular and inflammatory diseases, kidney dysfunctions, and neurodegenerative disorders, as well as infectious diseases. In viral infections, cathepsins may promote (1) activation of the viral attachment glycoproteins and entry of the virus into target cells; (2) antigen processing and presentation, enabling the virus to replicate in infected cells; (3) up-regulation and processing of heparanase that facilitates the release of viral progeny and the spread of infection; and (4) activation of cell death that may either favor viral clearance or assist viral propagation. In this review, we report the most relevant findings on the molecular mechanisms underlying cathepsin involvement in viral infection physiopathology, and we discuss the potential of cathepsin inhibitors for therapeutical applications in viral infectious diseases.
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Kovač V, Čurin Šerbec V. Prion Protein: The Molecule of Many Forms and Faces. Int J Mol Sci 2022; 23:ijms23031232. [PMID: 35163156 PMCID: PMC8835406 DOI: 10.3390/ijms23031232] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Revised: 01/10/2022] [Accepted: 01/21/2022] [Indexed: 02/06/2023] Open
Abstract
Cellular prion protein (PrPC) is a glycosylphosphatidylinositol (GPI)-anchored protein most abundantly found in the outer membrane of neurons. Due to structural characteristics (a flexible tail and structured core), PrPC interacts with a wide range of partners. Although PrPC has been proposed to be involved in many physiological functions, only peripheral nerve myelination homeostasis has been confirmed as a bona fide function thus far. PrPC misfolding causes prion diseases and PrPC has been shown to mediate β-rich oligomer-induced neurotoxicity in Alzheimer’s and Parkinson’s disease as well as neuroprotection in ischemia. Upon proteolytic cleavage, PrPC is transformed into released and attached forms of PrP that can, depending on the contained structural characteristics of PrPC, display protective or toxic properties. In this review, we will outline prion protein and prion protein fragment properties as well as overview their involvement with interacting partners and signal pathways in myelination, neuroprotection and neurodegenerative diseases.
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Antivirals targeting paramyxovirus membrane fusion. Curr Opin Virol 2021; 51:34-47. [PMID: 34592709 DOI: 10.1016/j.coviro.2021.09.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2021] [Revised: 09/01/2021] [Accepted: 09/02/2021] [Indexed: 01/29/2023]
Abstract
The Paramyxoviridae family includes enveloped single-stranded negative-sense RNA viruses such as measles, mumps, human parainfluenza, canine distemper, Hendra, and Nipah viruses, which cause a tremendous global health burden. The ability of paramyxoviral glycoproteins to merge viral and host membranes allows entry of the viral genome into host cells, as well as cell-cell fusion, an important contributor to disease progression. Recent molecular and structural advances in our understanding of the paramyxovirus membrane fusion machinery gave rise to various therapeutic approaches aiming at inhibiting viral infection, spread, and cytopathic effects. These therapeutic approaches include peptide mimics, antibodies, and small molecule inhibitors with various levels of success at inhibiting viral entry, increasing the potential of effective antiviral therapeutic development.
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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] [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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Novel Roles of the N1 Loop and N4 Alpha-Helical Region of the Nipah Virus Fusion Glycoprotein in Modulating Early and Late Steps of the Membrane Fusion Cascade. J Virol 2021; 95:JVI.01707-20. [PMID: 33568505 DOI: 10.1128/jvi.01707-20] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2020] [Accepted: 01/27/2021] [Indexed: 11/20/2022] Open
Abstract
Nipah virus (NiV) is a zoonotic bat henipavirus in the family Paramyxoviridae NiV is deadly to humans, infecting host cells by direct fusion of the viral and host cell plasma membranes. This membrane fusion process is coordinated by the receptor-binding attachment (G) and fusion (F) glycoproteins. Upon G-receptor binding, F fuses membranes via a cascade that sequentially involves F-triggering, fusion pore formation, and viral or genome entry into cells. Using NiV as an important paramyxoviral model, we identified two novel regions in F that modulate the membrane fusion cascade. For paramyxoviruses and other viral families with class I fusion proteins, the heptad repeat 1 (HR1) and HR2 regions in the fusion protein prefusion conformation bind to form a six-helix bundle in the postfusion conformation. Here, structural comparisons between the F prefusion and postfusion conformations revealed that a short loop region (N1) undergoes dramatic spatial reorganization and a short alpha helix (N4) undergoes secondary structural changes. The roles of the N1 and N4 regions during the membrane fusion cascade, however, remain unknown for henipaviruses and paramyxoviruses. By performing alanine scanning mutagenesis and various functional analyses, we report that specific residues within these regions alter various steps in the membrane fusion cascade. While the N1 region affects early F-triggering, the N4 region affects F-triggering, F thermostability, and extensive fusion pore expansion during syncytium formation, also uncovering a link between F-G interactions and F-triggering. These novel mechanistic roles expand our understanding of henipaviral and paramyxoviral F-triggering, viral entry, and cell-cell fusion (syncytia), a pathognomonic feature of paramyxoviral infections.IMPORTANCE Henipaviruses infect bats, agriculturally important animals, and humans, with high mortality rates approaching ∼75% in humans. Known human outbreaks have been concentrated in Southeast Asia and Australia. Furthermore, about 20 new henipaviral species have been recently discovered in bats, with geographical spans in Asia, Africa, and South America. The development of antiviral therapeutics requires a thorough understanding of the mechanism of viral entry into host cells. In this study, we discovered novel roles of two regions within the fusion protein of the deadly henipavirus NiV. Such roles were in allowing viral entry into host cells and cell-cell fusion, a pathological hallmark of this and other paramyxoviruses. These novel roles were in the previously undescribed N1 and N4 regions within the fusion protein, modulating early and late steps of these important processes of viral infection and henipaviral disease. Notably, this knowledge may apply to other henipaviruses and more broadly to other paramyxoviruses.
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Roles of Cholesterol in Early and Late Steps of the Nipah Virus Membrane Fusion Cascade. J Virol 2021; 95:JVI.02323-20. [PMID: 33408170 DOI: 10.1128/jvi.02323-20] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Accepted: 12/11/2020] [Indexed: 02/06/2023] Open
Abstract
Cholesterol has been implicated in various viral life cycle steps for different enveloped viruses, including viral entry into host cells, cell-cell fusion, and viral budding from infected cells. Enveloped viruses acquire their membranes from their host cells. Although cholesterol has been associated with the binding and entry of various enveloped viruses into cells, cholesterol's exact function in the viral-cell membrane fusion process remains largely elusive, particularly for the paramyxoviruses. Furthermore, paramyxoviral fusion occurs at the host cell membrane and is essential for both virus entry (virus-cell fusion) and syncytium formation (cell-cell fusion), central to viral pathogenicity. Nipah virus (NiV) is a deadly member of the Paramyxoviridae family, which also includes Hendra, measles, mumps, human parainfluenza, and various veterinary viruses. The zoonotic NiV causes severe encephalitis, vasculopathy, and respiratory symptoms, leading to a high mortality rate in humans. We used NiV as a model to study the role of membrane cholesterol in paramyxoviral membrane fusion. We used a combination of methyl-beta cyclodextrin (MβCD), lovastatin, and cholesterol to deplete or enrich cell membrane cholesterol outside cytotoxic concentrations. We found that the levels of cellular membrane cholesterol directly correlated with the levels of cell-cell fusion induced. These phenotypes were paralleled using NiV/vesicular stomatitis virus (VSV)-pseudotyped viral infection assays. Remarkably, our mechanistic studies revealed that cholesterol reduces an early F-triggering step but enhances a late fusion pore formation step in the NiV membrane fusion cascade. Thus, our results expand our mechanistic understanding of the paramyxoviral/henipaviral entry and cell-cell fusion processes.IMPORTANCE Cholesterol has been implicated in various steps of the viral life cycle for different enveloped viruses. Nipah virus (NiV) is a highly pathogenic enveloped virus in the Henipavirus genus within the Paramyxoviridae family, capable of causing a high mortality rate in humans and high morbidity in domestic and agriculturally important animals. The role of cholesterol for NiV or the henipaviruses is unknown. Here, we show that the levels of cholesterol influence the levels of NiV-induced cell-cell membrane fusion during syncytium formation and virus-cell membrane fusion during viral entry. Furthermore, the specific role of cholesterol in membrane fusion is not well defined for the paramyxoviruses. We show that the levels of cholesterol affect an early F-triggering step and a late fusion pore formation step during the membrane fusion cascade. Thus, our results expand our mechanistic understanding of the viral entry and cell-cell fusion processes, which may aid the development of antivirals.
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Third Helical Domain of the Nipah Virus Fusion Glycoprotein Modulates both Early and Late Steps in the Membrane Fusion Cascade. J Virol 2020; 94:JVI.00644-20. [PMID: 32669342 DOI: 10.1128/jvi.00644-20] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Accepted: 07/08/2020] [Indexed: 01/21/2023] Open
Abstract
Medically important paramyxoviruses, such as measles, mumps, parainfluenza, Nipah, and Hendra viruses, infect host cells by directing fusion of the viral and cellular plasma membranes. Upon infection, paramyxoviruses cause a second type of membrane fusion, cell-cell fusion (syncytium formation), which is linked to pathogenicity. Host cell receptor binding causes conformational changes in the attachment glycoprotein (HN, H, or G) that trigger a conformational cascade in the fusion (F) glycoprotein that mediates membrane fusion. F, a class I fusion protein, contains the archetypal heptad repeat regions 1 (HR1) and 2 (HR2). It is well established that binding of HR1 and HR2 is key to fusing viral and cellular membranes. In this study, we uncovered a novel fusion-modulatory role of a third structurally conserved helical region (HR3) in F. Based on its location within the F structure, and structural differences between its prefusion and postfusion conformations, we hypothesized that the HR3 modulates triggering of the F conformational cascade (still requiring G). We used the deadly Nipah virus (NiV) as an important paramyxoviral model to perform alanine scan mutagenesis and a series of multidisciplinary structural/functional analyses that dissect the various states of the membrane fusion cascade. Remarkably, we found that specific residues within the HR3 modulate not only early F-triggering but also late extensive fusion pore expansion steps in the membrane fusion cascade. Our results characterize these novel fusion-modulatory roles of the F HR3, improving our understanding of the membrane fusion process for NiV and likely for the related Henipavirus genus and possibly Paramyxoviridae family members.IMPORTANCE The Paramyxoviridae family includes important human and animal pathogens, such as measles, mumps, and parainfluenza viruses and the deadly henipaviruses Nipah (NiV) and Hendra (HeV) viruses. Paramyxoviruses infect the respiratory tract and the central nervous system (CNS) and can be highly infectious. Most paramyxoviruses have a limited host range. However, the biosafety level 4 NiV and HeV are highly pathogenic and have a wide mammalian host range. Nipah viral infections result in acute respiratory syndrome and severe encephalitis in humans, leading to 40 to 100% mortality rates. The lack of licensed vaccines or therapeutic approaches against NiV and other important paramyxoviruses underscores the need to understand viral entry mechanisms. In this study, we uncovered a novel role of a third helical region (HR3) of the NiV fusion glycoprotein in the membrane fusion process that leads to viral entry. This discovery sets HR3 as a new candidate target for antiviral strategies for NiV and likely for related viruses.
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Fischer K, Groschup MH, Diederich S. Importance of Endocytosis for the Biological Activity of Cedar Virus Fusion Protein. Cells 2020; 9:cells9092054. [PMID: 32911832 PMCID: PMC7565975 DOI: 10.3390/cells9092054] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Revised: 09/03/2020] [Accepted: 09/04/2020] [Indexed: 01/02/2023] Open
Abstract
Endocytosis plays a particular role in the proteolytic activation of highly pathogenic henipaviruses Hendra (HeV) and Nipah virus (NiV) fusion (F) protein precursors. These proteins require endocytic uptake from the cell surface to be cleaved by cellular proteases within the endosomal compartment, followed by recycling to the plasma membrane for incorporation into budding virions or mediation of cell-cell fusion. This internalization largely depends on a tyrosine-based consensus motif for endocytosis present in the cytoplasmic tail of HeV and NiV F. Given the large number of tyrosine residues present in the F protein cytoplasmic domain of Cedar virus (CedV), a closely related but low pathogenic henipavirus, we aimed to investigate whether CedV F protein undergoes signal-mediated endocytosis from the cell surface controlled by tyrosine-based motifs present in its cytoplasmic tail and whether endocytosis is relevant for its biological activity. Therefore, tyrosine-based signals were mutated, and mutations were assessed for their effect on F cell surface expression, endocytosis, and biological activity. A membrane-proximal YXXΦ motif and a C-terminal di-tyrosine motif are of particular importance for cell surface expression and endocytosis rate. Furthermore, our data strongly indicate the pivotal role of endocytosis for the biological activity of the CedV F protein.
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Brenna S, Altmeppen HC, Mohammadi B, Rissiek B, Schlink F, Ludewig P, Krisp C, Schlüter H, Failla AV, Schneider C, Glatzel M, Puig B, Magnus T. Characterization of brain-derived extracellular vesicles reveals changes in cellular origin after stroke and enrichment of the prion protein with a potential role in cellular uptake. J Extracell Vesicles 2020; 9:1809065. [PMID: 32944194 PMCID: PMC7480459 DOI: 10.1080/20013078.2020.1809065] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2020] [Revised: 07/28/2020] [Accepted: 08/09/2020] [Indexed: 02/06/2023] Open
Abstract
Extracellular vesicles (EVs) are important means of intercellular communication and a potent tool for regenerative therapy. In ischaemic stroke, transient blockage of a brain artery leads to a lack of glucose and oxygen in the affected brain tissue, provoking neuronal death by necrosis in the core of the ischaemic region. The fate of neurons in the surrounding penumbra region depends on the stimuli, including EVs, received during the following hours. A detailed characterization of such stimuli is crucial not only for understanding stroke pathophysiology but also for new therapeutic interventions. In the present study, we characterize the EVs in mouse brain under physiological conditions and 24 h after induction of transient ischaemia in mice. We show that, in steady-state conditions, microglia are the main source of small EVs (sEVs), whereas after ischaemia the main sEV population originates from astrocytes. Brain sEVs presented high amounts of the prion protein (PrP), which were further increased after stroke. Moreover, EVs were enriched in a proteolytically truncated PrP fragment (PrP-C1). Because of similarities between PrP-C1 and certain viral surface proteins, we studied the cellular uptake of brain-derived sEVs from mice lacking (PrP-KO) or expressing PrP (WT). We show that PrP-KO-sEVs are taken up significantly faster and more efficiently than WT-EVs by primary neurons. Furthermore, microglia and astrocytes engulf PrP-KO-sEVs more readily than WT-sEVs. Our results provide novel information on the relative contribution of brain cell types to the sEV pool in murine brain and indicate that increased release of sEVs by astrocytes together with elevated levels of PrP in sEVs may play a role in intercellular communication at early stages after stroke. In addition, amounts of PrP (and probably PrP-C1) in brain sEVs seem to contribute to regulating their cellular uptake.
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Affiliation(s)
- Santra Brenna
- Neurology Department, Experimental Research in Stroke and Inflammation, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Hermann C. Altmeppen
- Institute of Neuropathology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Behnam Mohammadi
- Institute of Neuropathology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Björn Rissiek
- Neurology Department, Experimental Research in Stroke and Inflammation, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Florence Schlink
- Neurology Department, Experimental Research in Stroke and Inflammation, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Peter Ludewig
- Neurology Department, Experimental Research in Stroke and Inflammation, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Christoph Krisp
- Institute of Clinical Chemistry and Laboratory Medicine, Mass Spectrometric Proteomics University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Hartmut Schlüter
- Institute of Clinical Chemistry and Laboratory Medicine, Mass Spectrometric Proteomics University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Antonio Virgilio Failla
- UKE Microscopy Imaging Facility, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Carola Schneider
- Heinrich Pette Institute, Leibniz Institute for Experimental Virology, Hamburg, Germany
| | - Markus Glatzel
- Institute of Neuropathology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Berta Puig
- Neurology Department, Experimental Research in Stroke and Inflammation, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Tim Magnus
- Neurology Department, Experimental Research in Stroke and Inflammation, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
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Azarm KD, Lee B. Differential Features of Fusion Activation within the Paramyxoviridae. Viruses 2020; 12:v12020161. [PMID: 32019182 PMCID: PMC7077268 DOI: 10.3390/v12020161] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Revised: 01/25/2020] [Accepted: 01/29/2020] [Indexed: 12/13/2022] Open
Abstract
Paramyxovirus (PMV) entry requires the coordinated action of two envelope glycoproteins, the receptor binding protein (RBP) and fusion protein (F). The sequence of events that occurs during the PMV entry process is tightly regulated. This regulation ensures entry will only initiate when the virion is in the vicinity of a target cell membrane. Here, we review recent structural and mechanistic studies to delineate the entry features that are shared and distinct amongst the Paramyxoviridae. In general, we observe overarching distinctions between the protein-using RBPs and the sialic acid- (SA-) using RBPs, including how their stalk domains differentially trigger F. Moreover, through sequence comparisons, we identify greater structural and functional conservation amongst the PMV fusion proteins, as compared to the RBPs. When examining the relative contributions to sequence conservation of the globular head versus stalk domains of the RBP, we observe that, for the protein-using PMVs, the stalk domains exhibit higher conservation and find the opposite trend is true for SA-using PMVs. A better understanding of conserved and distinct features that govern the entry of protein-using versus SA-using PMVs will inform the rational design of broader spectrum therapeutics that impede this process.
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Nipah Virus-Like Particle Egress Is Modulated by Cytoskeletal and Vesicular Trafficking Pathways: a Validated Particle Proteomics Analysis. mSystems 2019; 4:4/5/e00194-19. [PMID: 31551400 PMCID: PMC6759566 DOI: 10.1128/msystems.00194-19] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Classified as a biosafety level 4 (BSL4) select agent, Nipah virus (NiV) is a deadly henipavirus in the Paramyxoviridae family, with a nearly 75% mortality rate in humans, underscoring its global and animal health importance. Elucidating the process of viral particle production in host cells is imperative both for targeted drug design and viral particle-based vaccine development. However, little is understood concerning the functions of cellular machinery in paramyxoviral and henipaviral assembly and budding. Recent studies showed evidence for the involvement of multiple NiV proteins in viral particle formation, in contrast to the mechanisms understood for several paramyxoviruses as being reliant on the matrix (M) protein alone. Further, the levels and purposes of cellular factor incorporation into viral particles are largely unexplored for the paramyxoviruses. To better understand the involvement of cellular machinery and the major structural viral fusion (F), attachment (G), and matrix (M) proteins, we performed proteomics analyses on virus-like particles (VLPs) produced from several combinations of these NiV proteins. Our findings indicate that NiV VLPs incorporate vesicular trafficking and actin cytoskeletal factors. The involvement of these biological processes was validated by experiments indicating that the perturbation of key factors in these cellular processes substantially modulated viral particle formation. These effects were most impacted for NiV-F-modulated viral particle formation either autonomously or in combination with other NiV proteins, indicating that NiV-F budding relies heavily on these cellular processes. These findings indicate a significant involvement of the NiV fusion protein, vesicular trafficking, and actin cytoskeletal processes in efficient viral particle formation.IMPORTANCE Nipah virus is a zoonotic biosafety level 4 agent with high mortality rates in humans. The genus to which Nipah virus belongs, Henipavirus, includes five officially recognized pathogens; however, over 20 species have been identified in multiple continents within the last several years. As there are still no vaccines or treatments for NiV infection, elucidating its process of viral particle production is imperative both for targeted drug design as well as for particle-based vaccine development. Developments in high-throughput technologies make proteomic analysis of isolated viral particles a highly insightful approach to understanding the life cycle of pathogens such as Nipah virus.
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Nanbo A, Ohba Y. Budding of Ebola Virus Particles Requires the Rab11-Dependent Endocytic Recycling Pathway. J Infect Dis 2019; 218:S388-S396. [PMID: 30476249 PMCID: PMC6249604 DOI: 10.1093/infdis/jiy460] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
The Ebola virus-encoded major matrix protein VP40 traffics to the plasma membrane, which leads to the formation of filamentous viral particles and subsequent viral egress. However, the cellular machineries underlying this process are not fully understood. In the present study, we have assessed the role of host endocytic recycling in Ebola virus particle formation. We found that a small GTPase Rab11, which regulates recycling of molecules among the trans-Golgi network, recycling endosomes, and the plasma membrane, was incorporated in Ebola virus-like particles. Although Rab11 predominantly localized in the perinuclear region, it distributed diffusely in the cytoplasm and partly localized in the periphery of the cells transiently expressing VP40. In contrast, Rab11 exhibited a perinuclear distribution when 2 VP40 derivatives that lack ability to traffic to the plasma membrane were expressed. Finally, expression of a dominant-negative form of Rab11 or knockdown of Rab11 inhibited both VP40-induced clusters at the plasma membrane and release of viral-like particles. Taken together, our findings demonstrate that Ebola virus exploits host endocytic recycling machinery to facilitate the trafficking of VP40 to the cell surface and the subsequent release of viral-like particles for its establishment of efficient viral egress.
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Affiliation(s)
- Asuka Nanbo
- Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan
| | - Yusuke Ohba
- Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan
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Voigt K, Hoffmann M, Drexler JF, Müller MA, Drosten C, Herrler G, Krüger N. Fusogenicity of the Ghana Virus ( Henipavirus: Ghanaian bat henipavirus) Fusion Protein is Controlled by the Cytoplasmic Domain of the Attachment Glycoprotein. Viruses 2019; 11:v11090800. [PMID: 31470664 PMCID: PMC6784138 DOI: 10.3390/v11090800] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2019] [Revised: 08/28/2019] [Accepted: 08/28/2019] [Indexed: 01/11/2023] Open
Abstract
The Ghana virus (GhV) is phylogenetically related to the zoonotic henipaviruses Nipah (NiV) and Hendra virus. Although GhV uses the highly conserved receptor ephrin-B2, the fusogenicity is restricted to cell lines of bat origin. Furthermore, the surface expression of the GhV attachment glycoprotein (G) is reduced compared to NiV and most of this protein is retained in the endoplasmic reticulum (ER). Here, we generated truncated as well as chimeric GhV G proteins and investigated the influence of the structural domains (cytoplasmic tail, transmembrane domain, ectodomain) of this protein on the intracellular transport and the fusogenicity following coexpression with the GhV fusion protein (F). We demonstrate that neither the cytoplasmic tail nor the transmembrane domain is responsible for the intracellular retention of GhV G. Furthermore, the cytoplasmic tail of GhV G modulates the fusogenicity of GhV F and therefore controls the species-restricted fusogenicity of the GhV surface glycoproteins.
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Affiliation(s)
- Kathleen Voigt
- Institute of Virology, University of Veterinary Medicine Hannover, 30559 Hannover, Germany
- Research Center for Emerging Infections and Zoonoses, University of Veterinary Medicine Hannover, 30559 Hannover, Germany
| | - Markus Hoffmann
- Infection Biology Unit, German Primate Center-Leibniz Institute for Primate Research, 37077 Göttingen, Germany
| | - Jan Felix Drexler
- Institute of Virology, Charité Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin and Berlin Institute of Health, 10117 Berlin, Germany
| | - Marcel Alexander Müller
- Institute of Virology, Charité Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin and Berlin Institute of Health, 10117 Berlin, Germany
| | - Christian Drosten
- Institute of Virology, Charité Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin and Berlin Institute of Health, 10117 Berlin, Germany
| | - Georg Herrler
- Institute of Virology, University of Veterinary Medicine Hannover, 30559 Hannover, Germany
| | - Nadine Krüger
- Institute of Virology, University of Veterinary Medicine Hannover, 30559 Hannover, Germany.
- Research Center for Emerging Infections and Zoonoses, University of Veterinary Medicine Hannover, 30559 Hannover, Germany.
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Ramharack P, Devnarain N, Shunmugam L, Soliman MES. Navigating Research Toward the Re-emerging Nipah Virus- A New Piece to the Puzzle. Curr Pharm Des 2019; 25:1392-1401. [PMID: 31258065 DOI: 10.2174/1381612825666190620104203] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Accepted: 05/22/2019] [Indexed: 11/22/2022]
Abstract
BACKGROUND The recent Nipah virus (NiV) outbreak in India has caused a state of chaos, with potential to become the next international pandemic. There is still a great deal to learn about NiV for the development of a potent treatment against it. The NiV non-structural proteins play important roles in the lifecycle of the virus, with the RNA-dependent RNA-polymerase (RdRp) being a vital component in viral replication. In this study, we not only provide a comprehensive overview of all the literature concerning NiV, we also propose a model of the NiV RdRp and screen for potential inhibitors of the viral enzyme. METHODS In this study, computational tools were utilized in the design of a NiV RdRp homology model. The active site of RdRp was then identified and potential inhibitors of the protein were discovered with the use of pharmacophore-based screening. RESULTS Ramachandran plot analysis revealed a favourable model. Upon binding of nucleoside analog, 4'- Azidocytidine, active site residues Trp1714 and Ser1713 took part in stabilizing hydrogen bonds, while Thr1716, Ser1478, Ser1476 and Glu1465 contributed to hydrophobic interactions. Pharmacophore based screening yielded 18 hits, of which ZINC00085930 demonstrated the most optimal binding energy (-8.1 kcal/mol), validating its use for further analysis as an inhibitor of NiV. CONCLUSION In this study we provide a critical guide, elucidating on the in silico requirements of the drug design and discovery process against NiV. This material lays a foundation for future research into the design and development of drugs that inhibit NiV.
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Affiliation(s)
- Pritika Ramharack
- Molecular Bio-computation and Drug Design Laboratory, School of Health Sciences, University of KwaZulu-Natal, Westville Campus, Durban 4001, South Africa
| | - Nikita Devnarain
- Molecular Bio-computation and Drug Design Laboratory, School of Health Sciences, University of KwaZulu-Natal, Westville Campus, Durban 4001, South Africa
| | - Letitia Shunmugam
- Molecular Bio-computation and Drug Design Laboratory, School of Health Sciences, University of KwaZulu-Natal, Westville Campus, Durban 4001, South Africa
| | - Mahmoud E S Soliman
- Molecular Bio-computation and Drug Design Laboratory, School of Health Sciences, University of KwaZulu-Natal, Westville Campus, Durban 4001, South Africa
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Ringel M, Heiner A, Behner L, Halwe S, Sauerhering L, Becker N, Dietzel E, Sawatsky B, Kolesnikova L, Maisner A. Nipah virus induces two inclusion body populations: Identification of novel inclusions at the plasma membrane. PLoS Pathog 2019; 15:e1007733. [PMID: 31034506 PMCID: PMC6488097 DOI: 10.1371/journal.ppat.1007733] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Accepted: 03/26/2019] [Indexed: 01/31/2023] Open
Abstract
Formation of cytoplasmic inclusion bodies (IBs) is a hallmark of infections with non-segmented negative-strand RNA viruses (order Mononegavirales). We show here that Nipah virus (NiV), a bat-derived highly pathogenic member of the Paramyxoviridae family, differs from mononegaviruses of the Rhabdo-, Filo- and Pneumoviridae families by forming two types of IBs with distinct localizations, formation kinetics, and protein compositions. IBs in the perinuclear region form rapidly upon expression of the nucleocapsid proteins. These IBperi are highly mobile and associate with the aggresome marker y-tubulin. IBperi can recruit unrelated overexpressed cytosolic proteins but do not contain the viral matrix (M) protein. Additionally, NiV forms an as yet undescribed IB population at the plasma membrane (IBPM) that is y-tubulin-negative but contains the M protein. Infection studies with recombinant NiV revealed that IBPM require the M protein for their formation, and most likely represent sites of NiV assembly and budding. The identification of this novel type of plasma membrane-associated IBs not only provides new insights into NiV biology and may open new avenues to develop novel antiviral approaches to treat these highly pathogenic viruses, it also provides a basis for a more detailed characterization of IBs and their role in virus assembly and replication in infections with other Mononegavirales. Inclusion bodies (IBs) induced by non-segmented negative-strand RNA viruses (Mononegavirales) are described as mobile cytosolic compartments that concentrate viral proteins and represent the main viral replication sites in infected cells. This general concept is mainly based on studies with mononegaviruses from the Rhabdo-, Filo- and Pneumoviridae families. IBs induced by members of the Paramyxoviridae family are much less well characterized, and this study provides evidence that paramyxoviral IBs may have different compositions and functions. The main finding of this study is that Nipah virus (NiV), a highly pathogenic member of the genus Henipavirus in the family Paramyxoviridae, forms a novel type of IB whose formation at plasma membrane assembly sites depends on the viral matrix protein, and suggests a role for IBs not yet described for other Mononegavirales. This discovery clearly extents the current concept of IB functions and illustrates the need to further investigate IBs formed by other paramyxoviruses.
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Affiliation(s)
- Marc Ringel
- Institute of Virology, Philipps University Marburg, Marburg, Germany
| | - Anja Heiner
- Institute of Virology, Philipps University Marburg, Marburg, Germany
| | - Laura Behner
- Institute of Virology, Philipps University Marburg, Marburg, Germany
| | - Sandro Halwe
- Institute of Virology, Philipps University Marburg, Marburg, Germany
| | - Lucie Sauerhering
- Institute of Virology, Philipps University Marburg, Marburg, Germany
| | - Nico Becker
- Institute of Virology, Philipps University Marburg, Marburg, Germany
| | - Erik Dietzel
- Institute of Virology, Philipps University Marburg, Marburg, Germany
| | - Bevan Sawatsky
- Division of Veterinary Medicine, Paul-Ehrlich-Institut, Langen, Germany
| | | | - Andrea Maisner
- Institute of Virology, Philipps University Marburg, Marburg, Germany
- * E-mail:
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Flint M, Chatterjee P, Lin DL, McMullan LK, Shrivastava-Ranjan P, Bergeron É, Lo MK, Welch SR, Nichol ST, Tai AW, Spiropoulou CF. A genome-wide CRISPR screen identifies N-acetylglucosamine-1-phosphate transferase as a potential antiviral target for Ebola virus. Nat Commun 2019; 10:285. [PMID: 30655525 PMCID: PMC6336797 DOI: 10.1038/s41467-018-08135-4] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Accepted: 12/19/2018] [Indexed: 12/28/2022] Open
Abstract
There are no approved therapies for Ebola virus infection. Here, to find potential therapeutic targets, we perform a screen for genes essential for Ebola virus (EBOV) infection. We identify GNPTAB, which encodes the α and β subunits of N-acetylglucosamine-1-phosphate transferase. We show that EBOV infection of a GNPTAB knockout cell line is impaired, and that this is reversed by reconstituting GNPTAB expression. Fibroblasts from patients with mucolipidosis II, a disorder associated with mutations in GNPTAB, are refractory to EBOV, whereas cells from their healthy parents support infection. Impaired infection correlates with loss of the expression of cathepsin B, known to be essential for EBOV entry. GNPTAB activity is dependent upon proteolytic cleavage by the SKI-1/S1P protease. Inhibiting this protease with the small-molecule PF-429242 blocks EBOV entry and infection. Disruption of GNPTAB function may represent a strategy for a host-targeted therapy for EBOV. Genetic screens are important tools to identify host factors associated with viral infections. Here, Flint et al. perform a genome-wide CRISPR screen using infectious Ebola virus (EBOV) and show that the host transferase GNPTAB is required for EBOV infection and a potential target for antiviral therapies
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Affiliation(s)
- Mike Flint
- Viral Special Pathogens Branch, Division of High-Consequence Pathogens and Pathology, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, 1600 Clifton Road, MS G-14, Atlanta, GA, 30329, USA.
| | - Payel Chatterjee
- Viral Special Pathogens Branch, Division of High-Consequence Pathogens and Pathology, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, 1600 Clifton Road, MS G-14, Atlanta, GA, 30329, USA
| | - David L Lin
- Department of Microbiology & Immunology, University of Michigan Medical School, Ann Arbor, MI, 48109, USA
| | - Laura K McMullan
- Viral Special Pathogens Branch, Division of High-Consequence Pathogens and Pathology, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, 1600 Clifton Road, MS G-14, Atlanta, GA, 30329, USA
| | - Punya Shrivastava-Ranjan
- Viral Special Pathogens Branch, Division of High-Consequence Pathogens and Pathology, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, 1600 Clifton Road, MS G-14, Atlanta, GA, 30329, USA
| | - Éric Bergeron
- Viral Special Pathogens Branch, Division of High-Consequence Pathogens and Pathology, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, 1600 Clifton Road, MS G-14, Atlanta, GA, 30329, USA
| | - Michael K Lo
- Viral Special Pathogens Branch, Division of High-Consequence Pathogens and Pathology, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, 1600 Clifton Road, MS G-14, Atlanta, GA, 30329, USA
| | - Stephen R Welch
- Viral Special Pathogens Branch, Division of High-Consequence Pathogens and Pathology, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, 1600 Clifton Road, MS G-14, Atlanta, GA, 30329, USA
| | - Stuart T Nichol
- Viral Special Pathogens Branch, Division of High-Consequence Pathogens and Pathology, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, 1600 Clifton Road, MS G-14, Atlanta, GA, 30329, USA
| | - Andrew W Tai
- Department of Microbiology & Immunology, University of Michigan Medical School, Ann Arbor, MI, 48109, USA.,Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, 48109, USA
| | - Christina F Spiropoulou
- Viral Special Pathogens Branch, Division of High-Consequence Pathogens and Pathology, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, 1600 Clifton Road, MS G-14, Atlanta, GA, 30329, USA.
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Behner L, Zimmermann L, Ringel M, Weis M, Maisner A. Formation of high-order oligomers is required for functional bioactivity of an African bat henipavirus surface glycoprotein. Vet Microbiol 2018; 218:90-97. [DOI: 10.1016/j.vetmic.2018.03.031] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2018] [Revised: 03/29/2018] [Accepted: 03/31/2018] [Indexed: 10/17/2022]
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Host Cell Proteases: Cathepsins. ACTIVATION OF VIRUSES BY HOST PROTEASES 2018. [PMCID: PMC7123490 DOI: 10.1007/978-3-319-75474-1_10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Cathepsins are proteolytic enzymes with a broad spectrum of substrates. They are known to reside within endo-lysosomes where they acquire optimal conditions for proteolytic activity and substrate cleavage. However, cathepsins have been detected in locations other than the canonical compartments of the endocytotic pathway. They are often secreted from cells in either proteolytically inactive proform or as mature and active enzyme; this may happen in both physiological and pathological conditions. Moreover, cytosolic and nuclear forms of cathepsins have been described and are currently an emerging field of research aiming at understanding their functions in such unexpected cellular locations. This chapter summarizes the canonical pathways of biosynthesis and transport of cathepsins in healthy cells. We further describe how cathepsins can reach unexpected locations such as the extracellular space or the cytosol and the nuclear matrix. No matter where viruses and cathepsins encounter, several outcomes can be perceived. Thus, scenarios are discussed on how cathepsins may support virus entry into host cells, involve in viral fusion factor and polyprotein processing in different host cell compartments, or help in packaging of viral particles during maturation. It is of note to mention that this review is not meant to comprehensively cover the present literature on viruses encountering cathepsins but rather illustrates, on some representative examples, the possible roles of cathepsins in replication of viruses and in the course of disease.
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King B, Tarr AW. How have retrovirus pseudotypes contributed to our understanding of viral entry? Future Virol 2017. [DOI: 10.2217/fvl-2017-0062] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Study of virus entry into host cells is important for understanding viral tropism and pathogenesis. Studying the entry of in vitro cultured viruses is not always practicable. Study of highly pathogenic viruses, viruses that do not grow in culture, and viruses that rapidly change phenotype in vitro can all benefit from alternative models of entry. Retrovirus particles can be engineered to display the envelope proteins of heterologous enveloped viruses. This approach, broadly termed ‘pseudotyping’, is an important technique for interrogating virus entry. In this perspective we consider how retrovirus pseudotypes have addressed these challenges and improved our understanding of the entry pathways of diverse virus species, including Ebolavirus, human immunodeficiency virus and hepatitis C virus.
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Affiliation(s)
- Barnabas King
- National Institute for Health Research (NIHR) Nottingham Biomedical Research Centre, Nottingham University Hospitals NHS Trust & the University of Nottingham, Nottingham, UK
- School of Life Sciences, Faculty of Medicine & Health Sciences, University of Nottingham, Nottingham, UK
| | - Alexander W Tarr
- National Institute for Health Research (NIHR) Nottingham Biomedical Research Centre, Nottingham University Hospitals NHS Trust & the University of Nottingham, Nottingham, UK
- School of Life Sciences, Faculty of Medicine & Health Sciences, University of Nottingham, Nottingham, UK
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Mutations in the Transmembrane Domain and Cytoplasmic Tail of Hendra Virus Fusion Protein Disrupt Virus-Like-Particle Assembly. J Virol 2017; 91:JVI.00152-17. [PMID: 28468881 DOI: 10.1128/jvi.00152-17] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Accepted: 04/12/2017] [Indexed: 12/13/2022] Open
Abstract
Hendra virus (HeV) is a zoonotic paramyxovirus that causes deadly illness in horses and humans. An intriguing feature of HeV is the utilization of endosomal protease for activation of the viral fusion protein (F). Here we investigated how endosomal F trafficking affects HeV assembly. We found that the HeV matrix (M) and F proteins each induced particle release when they were expressed alone but that their coexpression led to coordinated assembly of virus-like particles (VLPs) that were morphologically and physically distinct from M-only or F-only VLPs. Mutations to the F protein transmembrane domain or cytoplasmic tail that disrupted endocytic trafficking led to failure of F to function with M for VLP assembly. Wild-type F functioned normally for VLP assembly even when its cleavage was prevented with a cathepsin inhibitor, indicating that it is endocytic F trafficking that is important for VLP assembly, not proteolytic F cleavage. Under specific conditions of reduced M expression, we found that M could no longer induce significant VLP release but retained the ability to be incorporated as a passenger into F-driven VLPs, provided that the F protein was competent for endocytic trafficking. The F and M proteins were both found to traffic through Rab11-positive recycling endosomes (REs), suggesting a model in which F and M trafficking pathways converge at REs, enabling these proteins to preassemble before arriving at plasma membrane budding sites.IMPORTANCE Hendra virus and Nipah virus are zoonotic paramyxoviruses that cause lethal infections in humans. Unlike that for most paramyxoviruses, activation of the henipavirus fusion protein occurs in recycling endosomal compartments. In this study, we demonstrate that the unique endocytic trafficking pathway of Hendra virus F protein is required for proper viral assembly and particle release. These results advance our basic understanding of the henipavirus assembly process and provide a novel model for the interplay between glycoprotein trafficking and paramyxovirus assembly.
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Cytoplasmic Motifs in the Nipah Virus Fusion Protein Modulate Virus Particle Assembly and Egress. J Virol 2017; 91:JVI.02150-16. [PMID: 28250132 DOI: 10.1128/jvi.02150-16] [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: 10/27/2016] [Accepted: 02/21/2017] [Indexed: 01/19/2023] Open
Abstract
Nipah virus (NiV), a paramyxovirus in the genus Henipavirus, has a mortality rate in humans of approximately 75%. While several studies have begun our understanding of NiV particle formation, the mechanism of this process remains to be fully elucidated. For many paramyxoviruses, M proteins drive viral assembly and egress; however, some paramyxoviral glycoproteins have been reported as important or essential in budding. For NiV the matrix protein (M), the fusion glycoprotein (F) and, to a much lesser extent, the attachment glycoprotein (G) autonomously induce the formation of virus-like particles (VLPs). However, functional interactions between these proteins during assembly and egress remain to be fully understood. Moreover, if the F-driven formation of VLPs occurs through interactions with host cell machinery, the cytoplasmic tail (CT) of F is a likely interactive domain. Therefore, we analyzed NiV F CT deletion and alanine mutants and report that several but not all regions of the F CT are necessary for efficient VLP formation. Two of these regions contain YXXØ or dityrosine motifs previously shown to interact with cellular machinery involved in F endocytosis and transport. Importantly, our results showed that F-driven, M-driven, and M/F-driven viral particle formation enhanced the recruitment of G into VLPs. By identifying key motifs, specific residues, and functional viral protein interactions important for VLP formation, we improve our understanding of the viral assembly/egress process and point to potential interactions with host cell machinery.IMPORTANCE Henipaviruses can cause deadly infections of medical, veterinary, and agricultural importance. With recent discoveries of new henipa-like viruses, understanding the mechanisms by which these viruses reproduce is paramount. We have focused this study on identifying the functional interactions of three Nipah virus proteins during viral assembly and particularly on the role of one of these proteins, the fusion glycoprotein, in the incorporation of other viral proteins into viral particles. By identifying several regions in the fusion glycoprotein that drive viral assembly, we further our understanding of how these viruses assemble and egress from infected cells. The results presented will likely be useful toward designing treatments targeting this aspect of the viral life cycle and for the production of new viral particle-based vaccines.
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Influenza Virus Overcomes Cellular Blocks To Productively Replicate, Impacting Macrophage Function. J Virol 2017; 91:JVI.01417-16. [PMID: 27807237 DOI: 10.1128/jvi.01417-16] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Accepted: 10/27/2016] [Indexed: 11/20/2022] Open
Abstract
Whether influenza virus replication in macrophages is productive or abortive has been a topic of debate. Utilizing a panel of 28 distinct human, avian, and swine influenza viruses, we found that only a small subset can overcome cellular blocks to productively replicate in murine and primary human macrophages. Murine macrophages have two cellular blocks. The first block is during viral entry, where virions with relatively acid-stable hemagglutinin (HA) proteins are rendered incapable of pH-induced triggering for membrane fusion, resulting in lysosomal degradation. The second block is downstream of viral replication but upstream of late protein synthesis. In contrast, primary human macrophages only have one cellular block that occurs after late protein synthesis. To determine the impact of abortive replication at different stages of the viral life cycle or productive replication on macrophage function, we assessed cytotoxicity, nitric oxide or reactive oxygen species production, and phagocytosis. Intriguingly, productive viral replication decreased phagocytosis of IgG-opsonized bioparticles and Fc receptor CD16 and CD32 surface levels, a function, to our knowledge, never before reported for an RNA virus. These data suggest that replication in macrophages affects cellular function and plays an important role in pathogenesis during infection in vivo IMPORTANCE: Macrophages are a critical first line of defense against respiratory pathogens. Thus, understanding how viruses evade or exploit macrophage function will provide greater insight into viral pathogenicity and antiviral responses. We previously showed that only a subset of highly pathogenic avian (HPAI) H5N1 influenza virus strains could productively replicate in murine macrophages through a hemagglutinin (HA)-mediated mechanism. These studies expand upon this work and demonstrate that productive replication is not specific to unique HPAI H5N1 viruses; an H1N1 strain (A/WSN/33) can also replicate in macrophages. Importantly, we identify two cellular blocks limiting replication that can be overcome by an avian-like pH of activation for nuclear entry and a yet-to-be-identified mechanism(s) to overcome a postnuclear entry block. Overcoming these blocks reduces the cell's ability to phagocytose IgG-opsonized bioparticles by decreasing Fc receptor surface levels, a mechanism previously thought to occur during bacterial and DNA viral infections.
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Sauerhering L, Zickler M, Elvert M, Behner L, Matrosovich T, Erbar S, Matrosovich M, Maisner A. Species-specific and individual differences in Nipah virus replication in porcine and human airway epithelial cells. J Gen Virol 2016; 97:1511-1519. [PMID: 27075405 DOI: 10.1099/jgv.0.000483] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Highly pathogenic Nipah virus (NiV) causes symptomatic infections in pigs and humans. The severity of respiratory symptoms is much more pronounced in pigs than in humans, suggesting species-specific differences of NiV replication in porcine and human airways. Here, we present a comparative study on productive NiV replication in primary airway epithelial cell cultures of the two species. We reveal that NiV growth substantially differs in primary cells between pigs and humans, with a more rapid spread of infection in human airway epithelia. Increased replication, correlated with higher endogenous expression levels of the main NiV entry receptor ephrin-B2, not only significantly differed between airway cells of the two species but also varied between cells from different human donors. To our knowledge, our study provides the first experimental evidence of species-specific and individual differences in NiV receptor expression and replication kinetics in primary airway epithelial cells. It remains to be determined whether and how these differences contribute to the viral host range and pathogenicity.
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Affiliation(s)
- Lucie Sauerhering
- Institute of Virology, Philipps University Marburg, Marburg, Germany
| | - Martin Zickler
- Institute of Virology, Philipps University Marburg, Marburg, Germany
| | - Mareike Elvert
- Institute of Virology, Philipps University Marburg, Marburg, Germany
| | - Laura Behner
- Institute of Virology, Philipps University Marburg, Marburg, Germany
| | | | - Stephanie Erbar
- Institute of Virology, Philipps University Marburg, Marburg, Germany
| | | | - Andrea Maisner
- Institute of Virology, Philipps University Marburg, Marburg, Germany
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White JM, Whittaker GR. Fusion of Enveloped Viruses in Endosomes. Traffic 2016; 17:593-614. [PMID: 26935856 PMCID: PMC4866878 DOI: 10.1111/tra.12389] [Citation(s) in RCA: 281] [Impact Index Per Article: 35.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2016] [Revised: 02/25/2016] [Accepted: 02/25/2016] [Indexed: 12/12/2022]
Abstract
Ari Helenius launched the field of enveloped virus fusion in endosomes with a seminal paper in the Journal of Cell Biology in 1980. In the intervening years, a great deal has been learned about the structures and mechanisms of viral membrane fusion proteins as well as about the endosomes in which different enveloped viruses fuse and the endosomal cues that trigger fusion. We now recognize three classes of viral membrane fusion proteins based on structural criteria and four mechanisms of fusion triggering. After reviewing general features of viral membrane fusion proteins and viral fusion in endosomes, we delve into three characterized mechanisms for viral fusion triggering in endosomes: by low pH, by receptor binding plus low pH and by receptor binding plus the action of a protease. We end with a discussion of viruses that may employ novel endosomal fusion‐triggering mechanisms. A key take‐home message is that enveloped viruses that enter cells by fusing in endosomes traverse the endocytic pathway until they reach an endosome that has all of the environmental conditions (pH, proteases, ions, intracellular receptors and lipid composition) to (if needed) prime and (in all cases) trigger the fusion protein and to support membrane fusion.
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Affiliation(s)
- Judith M White
- Department of Cell Biology, University of Virginia, Charlottesville, VA, USA
| | - Gary R Whittaker
- Department of Microbiology & Immunology, Cornell University, Ithaca, NY, USA
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Hoffmann M, Krüger N, Zmora P, Wrensch F, Herrler G, Pöhlmann S. The Hemagglutinin of Bat-Associated Influenza Viruses Is Activated by TMPRSS2 for pH-Dependent Entry into Bat but Not Human Cells. PLoS One 2016; 11:e0152134. [PMID: 27028521 PMCID: PMC4814062 DOI: 10.1371/journal.pone.0152134] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Accepted: 03/09/2016] [Indexed: 11/18/2022] Open
Abstract
New World bats have recently been discovered to harbor influenza A virus (FLUAV)-related viruses, termed bat-associated influenza A-like viruses (batFLUAV). The internal proteins of batFLUAV are functional in mammalian cells. In contrast, no biological functionality could be demonstrated for the surface proteins, hemagglutinin (HA)-like (HAL) and neuraminidase (NA)-like (NAL), and these proteins need to be replaced by their human counterparts to allow spread of batFLUAV in human cells. Here, we employed rhabdoviral vectors to study the role of HAL and NAL in viral entry. Vectors pseudotyped with batFLUAV-HAL and -NAL were able to enter bat cells but not cells from other mammalian species. Host cell entry was mediated by HAL and was dependent on prior proteolytic activation of HAL and endosomal low pH. In contrast, sialic acids were dispensable for HAL-driven entry. Finally, the type II transmembrane serine protease TMPRSS2 was able to activate HAL for cell entry indicating that batFLUAV can utilize human proteases for HAL activation. Collectively, these results identify viral and cellular factors governing host cell entry driven by batFLUAV surface proteins. They suggest that the absence of a functional receptor precludes entry of batFLUAV into human cells while other prerequisites for entry, HAL activation and protonation, are met in target cells of human origin.
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Affiliation(s)
- Markus Hoffmann
- Infection Biology Unit, German Primate Center, Göttingen, Germany
- * E-mail: (SP); (MH)
| | - Nadine Krüger
- Institute of Virology, University of Veterinary Medicine Hannover, Hannover, Germany
| | - Pawel Zmora
- Infection Biology Unit, German Primate Center, Göttingen, Germany
| | - Florian Wrensch
- Infection Biology Unit, German Primate Center, Göttingen, Germany
| | - Georg Herrler
- Institute of Virology, University of Veterinary Medicine Hannover, Hannover, Germany
| | - Stefan Pöhlmann
- Infection Biology Unit, German Primate Center, Göttingen, Germany
- * E-mail: (SP); (MH)
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Abstract
Many viruses exploit specific arms of the endomembrane system. The unique composition of each arm prompts the development of remarkably specific interactions between viruses and sub-organelles. This review focuses on the viral–host interactions occurring on the endocytic recycling compartment (ERC), and mediated by its regulatory Ras-related in brain (Rab) GTPase Rab11. This protein regulates trafficking from the ERC and the trans-Golgi network to the plasma membrane. Such transport comprises intricate networks of proteins/lipids operating sequentially from the membrane of origin up to the cell surface. Rab11 is also emerging as a critical factor in an increasing number of infections by major animal viruses, including pathogens that provoke human disease. Understanding the interplay between the ERC and viruses is a milestone in human health. Rab11 has been associated with several steps of the viral lifecycles by unclear processes that use sophisticated diversified host machinery. For this reason, we first explore the state-of-the-art on processes regulating membrane composition and trafficking. Subsequently, this review outlines viral interactions with the ERC, highlighting current knowledge on viral-host binding partners. Finally, using examples from the few mechanistic studies available we emphasize how ERC functions are adjusted during infection to remodel cytoskeleton dynamics, innate immunity and membrane composition.
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Affiliation(s)
- Sílvia Vale-Costa
- Cell Biology of Viral Infection Lab, Instituto Gulbenkian de Ciência, Rua da Quinta Grande, 6, 2780-156 Oeiras, Portugal.
| | - Maria João Amorim
- Cell Biology of Viral Infection Lab, Instituto Gulbenkian de Ciência, Rua da Quinta Grande, 6, 2780-156 Oeiras, Portugal.
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Preventing Cleavage of the Respiratory Syncytial Virus Attachment Protein in Vero Cells Rescues the Infectivity of Progeny Virus for Primary Human Airway Cultures. J Virol 2015; 90:1311-20. [PMID: 26581976 DOI: 10.1128/jvi.02351-15] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2015] [Accepted: 11/05/2015] [Indexed: 01/20/2023] Open
Abstract
UNLABELLED All live attenuated respiratory syncytial virus (RSV) vaccines that have advanced to clinical trials have been produced in Vero cells. The attachment (G) glycoprotein in virions produced in these cells is smaller than that produced in other immortalized cells due to cleavage. These virions are 5-fold less infectious for primary well-differentiated human airway epithelial (HAE) cell cultures. Because HAE cells are isolated directly from human airways, Vero cell-grown vaccine virus would very likely be similarly inefficient at initiating infection of the nasal epithelium following vaccination, and therefore, a larger inoculum would be required for effective vaccination. We hypothesized that Vero cell-derived virus containing an intact G protein would be more infectious for HAE cell cultures. Using protease inhibitors with increasing specificity, we identified cathepsin L to be the protease responsible for cleavage. Our evidence suggests that cleavage occurs in the late endosome or lysosome during endocytic recycling. Cathepsin L activity was 100-fold greater in Vero cells than in HeLa cells. In addition, cathepsin L was able to cleave the G protein in Vero cell-grown virions but not in HeLa cell-grown virions, suggesting a difference in G-protein posttranslational modification in the two cell lines. We identified by mutagenesis amino acids important for cleavage, and these amino acids included a likely cathepsin L cleavage site. Virus containing a modified, noncleavable G protein produced in Vero cells was 5-fold more infectious for HAE cells in culture, confirming our hypothesis and indicating the value of including such a mutation in future live attenuated RSV vaccines. IMPORTANCE Worldwide, RSV is the second leading infectious cause of infant death, but no vaccine is available. Experimental live attenuated RSV vaccines are grown in Vero cells, but during production the virion attachment (G) glycoprotein is cleaved. Virions containing a cleaved G protein are less infectious for primary airway epithelial cells, the natural RSV target. In the study described here we identified the protease responsible, located the cleavage site, and demonstrated that cleavage likely occurs during endocytic recycling. Moreover, we showed that the infectivity of Vero cell-derived virus for primary airway epithelial cells is increased 5-fold if the virus contains a mutation in the G protein that prevents cleavage. The blocking of cleavage should improve RSV vaccine yield, consequently reducing production costs. Posttranslational cleavage of the fusion glycoprotein of many viruses plays an essential role in activation; however, cleavage of the RSV G protein is a novel example of a detrimental effect of cleavage on virus infectivity.
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Abstract
UNLABELLED Human cathepsin W (CtsW) is a cysteine protease, which was identified in a genome-wide RNA interference (RNAi) screen to be required for influenza A virus (IAV) replication. In this study, we show that reducing the levels of expression of CtsW reduces viral titers for different subtypes of IAV, and we map the target step of CtsW requirement to viral entry. Using a set of small interfering RNAs (siRNAs) targeting CtsW, we demonstrate that knockdown of CtsW results in a decrease of IAV nucleoprotein accumulation in the nuclei of infected cells at 3 h postinfection. Assays specific for the individual stages of IAV entry further show that attachment, internalization, and early endosomal trafficking are not affected by CtsW knockdown. However, we detected impaired escape of viral particles from late endosomes in CtsW knockdown cells. Moreover, fusion analysis with a dual-labeled influenza virus revealed a significant reduction in fusion events, with no detectable impact on endosomal pH, suggesting that CtsW is required at the stage of viral fusion. The defect in IAV entry upon CtsW knockdown could be rescued by ectopic expression of wild-type CtsW but not by the expression of a catalytically inactive mutant of CtsW, suggesting that the proteolytic activity of CtsW is required for successful entry of IAV. Our results establish CtsW as an important host factor for entry of IAV into target cells and suggest that CtsW could be a promising target for the development of future antiviral drugs. IMPORTANCE Increasing levels of resistance of influenza viruses to available antiviral drugs have been observed. Development of novel treatment options is therefore of high priority. In parallel to the classical approach of targeting viral enzymes, a novel strategy is pursued: cell-dependent factors of the virus are identified with the aim of developing small-molecule inhibitors against a cellular target that the virus relies on. For influenza A virus, several genome-wide RNA interference (RNAi) screens revealed hundreds of potential cellular targets. However, we have only limited knowledge on how these factors support virus replication, which would be required for drug development. We have characterized cathepsin W, one of the candidate factors, and found that cathepsin W is required for escape of influenza virus from the late endosome. Importantly, this required the proteolytic activity of cathepsin W. We therefore suggest that cathepsin W could be a target for future host cell-directed antiviral therapies.
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Weis M, Maisner A. Nipah virus fusion protein: Importance of the cytoplasmic tail for endosomal trafficking and bioactivity. Eur J Cell Biol 2015; 94:316-22. [PMID: 26059400 PMCID: PMC7114669 DOI: 10.1016/j.ejcb.2015.05.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Nipah virus (NiV) is a highly pathogenic paramyxovirus which encodes two surface glycoproteins: the receptor-binding protein G and the fusion protein F. As for all paramyxoviruses, proteolytic activation of the NiV-F protein is an indispensable prerequisite for viral infectivity. Interestingly, proteolytic activation of NiV-F differs principally from other paramyxoviruses with respect to protease usage (cathepsins instead of trypsin- or furin-like proteases), and the subcellular localization where cleavage takes place (endosomes instead of Golgi or plasma membrane). To allow efficient F protein activation needed for productive virus replication and cell-to-cell fusion, the NiV-F cytoplasmic tail contains a classical tyrosine-based endocytosis signal (Y525RSL) that we have shown earlier to be needed for F uptake and proteolytic activation. In this report, we furthermore revealed that an intact endocytosis signal alone is not sufficient for full bioactivity. The very C-terminus of the cytoplasmic tail is needed in addition. Deletions of more than four residues did not affect F uptake or endosomal cleavage but downregulated the surface expression, likely by delaying the intracellular trafficking through endosomal-recycling compartments. Given that the NiV-F cytoplasmic tail is needed for timely and correct intracellular trafficking, endosomal cleavage and fusion activity, the influence of tail truncations on NiV-mediated cell-to-cell fusion and on pseudotyping lentiviral vectors is discussed.
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Affiliation(s)
- Michael Weis
- Institute of Virology, Philipps University of Marburg, Marburg, Germany
| | - Andrea Maisner
- Institute of Virology, Philipps University of Marburg, Marburg, Germany.
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Brix K, McInnes J, Al-Hashimi A, Rehders M, Tamhane T, Haugen MH. Proteolysis mediated by cysteine cathepsins and legumain-recent advances and cell biological challenges. PROTOPLASMA 2015; 252:755-774. [PMID: 25398648 DOI: 10.1007/s00709-014-0730-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Accepted: 11/04/2014] [Indexed: 06/04/2023]
Abstract
Proteases play essential roles in protein degradation, protein processing, and extracellular matrix remodeling in all cell types and tissues. They are also involved in protein turnover for maintenance of homeostasis and protein activation or inactivation for cell signaling. Proteases range in function and specificity, with some performing distinct substrate cleavages, while others accomplish proteolysis of a wide range of substrates. As such, different cell types use specialized molecular mechanisms to regulate the localization of proteases and their function within the compartments to which they are destined. Here, we focus on the cysteine family of cathepsin proteases and legumain, which act predominately within the endo-lysosomal pathway. In particular, recent knowledge on cysteine cathepsins and their primary regulator legumain is scrutinized in terms of their trafficking to endo-lysosomal compartments and other less recognized cellular locations. We further explore the mechanisms that regulate these processes and point to pathological cases which arise from detours taken by these proteases. Moreover, the emerging biological roles of specific forms and variants of cysteine cathepsins and legumain are discussed. These may be decisive, pathogenic, or even deadly when localizing to unusual cellular compartments in their enzymatically active form, because they may exert unexpected effects by alternative substrate cleavage. Hence, we propose future perspectives for addressing the actions of cysteine cathepsins and legumain as well as their specific forms and variants. The increasing knowledge in non-canonical aspects of cysteine cathepsin- and legumain-mediated proteolysis may prove valuable for developing new strategies to utilize these versatile proteases in therapeutic approaches.
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Affiliation(s)
- Klaudia Brix
- Research Area HEALTH, Research Center MOLIFE-Molecular Life Sciences, Jacobs University Bremen, Campus Ring 1, 28759, Bremen, Germany,
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Weis M, Behner L, Binger T, Drexler JF, Drosten C, Maisner A. Fusion activity of African henipavirus F proteins with a naturally occurring start codon directly upstream of the signal peptide. Virus Res 2015; 201:85-93. [PMID: 25725148 DOI: 10.1016/j.virusres.2015.02.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Revised: 02/05/2015] [Accepted: 02/17/2015] [Indexed: 11/24/2022]
Abstract
Compared to the fusion proteins of pathogenic Nipah and Hendra viruses, the F protein of prototype African henipavirus GH-M74a displays a drastically reduced surface expression and fusion activity. A probable reason for limited F expression is the unusually long sequence located between the gene start and the signal peptide (SP) not present in other henipaviruses. Such a long pre-SP extension can prevent efficient ER translocation or protein maturation and processing. As its truncation can therefore enhance surface expression, the recent identification of a second in-frame start codon directly upstream of the SP in another African henipavirus F gene (GH-UP28) raised the question if such a naturally occurring minor sequence variation can lead to the synthesis of a pre-SP truncated translation product, thereby increasing the production of mature F proteins. To test this, we analyzed surface expression and biological activity of F genes carrying the second SP-proximal start codon of GH-UP28. Though we observed minor differences in the expression levels, introduction of the additional start codon did not result in an increased fusion activity, even if combined with further mutations in the pre-SP region. Thus, limited bioactivity of African henipavirus F protein is maintained even after sequence changes that alter the gene start allowing the production of F proteins without an unusually long pre-SP.
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Affiliation(s)
- Michael Weis
- Institute of Virology, Philipps University Marburg, Marburg, Germany
| | - Laura Behner
- Institute of Virology, Philipps University Marburg, Marburg, Germany
| | - Tabea Binger
- Institute of Virology, University of Bonn Medical Centre, Bonn, Germany
| | - Jan Felix Drexler
- Institute of Virology, University of Bonn Medical Centre, Bonn, Germany
| | - Christian Drosten
- Institute of Virology, University of Bonn Medical Centre, Bonn, Germany
| | - Andrea Maisner
- Institute of Virology, Philipps University Marburg, Marburg, Germany.
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Analysis of cathepsin and furin proteolytic enzymes involved in viral fusion protein activation in cells of the bat reservoir host. PLoS One 2015; 10:e0115736. [PMID: 25706132 PMCID: PMC4338073 DOI: 10.1371/journal.pone.0115736] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Accepted: 11/18/2014] [Indexed: 12/12/2022] Open
Abstract
Bats of different species play a major role in the emergence and transmission of highly pathogenic viruses including Ebola virus, SARS-like coronavirus and the henipaviruses. These viruses require proteolytic activation of surface envelope glycoproteins needed for entry, and cellular cathepsins have been shown to be involved in proteolysis of glycoproteins from these distinct virus families. Very little is currently known about the available proteases in bats. To determine whether the utilization of cathepsins by bat-borne viruses is related to the nature of proteases in their natural hosts, we examined proteolytic processing of several viral fusion proteins in cells derived from two fruit bat species, Pteropus alecto and Rousettus aegyptiacus. Our work shows that fruit bat cells have homologs of cathepsin and furin proteases capable of cleaving and activating both the cathepsin-dependent Hendra virus F and the furin-dependent parainfluenza virus 5 F proteins. Sequence analysis comparing Pteropus alecto furin and cathepsin L to proteases from other mammalian species showed a high degree of conservation; however significant amino acid variation occurs at the C-terminus of Pteropus alecto furin. Further analysis of furin-like proteases from fruit bats revealed that these proteases are catalytically active and resemble other mammalian furins in their response to a potent furin inhibitor. However, kinetic analysis suggests that differences may exist in the cellular localization of furin between different species. Collectively, these results indicate that the unusual role of cathepsin proteases in the life cycle of bat-borne viruses is not due to the lack of active furin-like proteases in these natural reservoir species; however, differences may exist between furin proteases present in fruit bats compared to furins in other mammalian species, and these differences may impact protease usage for viral glycoprotein processing.
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Zhou Y, Vedantham P, Lu K, Agudelo J, Carrion R, Nunneley JW, Barnard D, Pöhlmann S, McKerrow JH, Renslo AR, Simmons G. Protease inhibitors targeting coronavirus and filovirus entry. Antiviral Res 2015; 116:76-84. [PMID: 25666761 PMCID: PMC4774534 DOI: 10.1016/j.antiviral.2015.01.011] [Citation(s) in RCA: 441] [Impact Index Per Article: 49.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Revised: 01/14/2015] [Accepted: 01/25/2015] [Indexed: 11/15/2022]
Abstract
We identify vinylsulfones as lead candidate inhibitors of Ebola virus and SARS-CoV. K11777 inhibited Ebola virus and SARS-CoV entry in the sub-nanomolar range. Potent inhibition correlated with the presence of a basic piperazine ring at P3. Serine protease inhibitor and K11777 blocked coronavirus entry into caco-2 cells. Camostat protected 6 out of ten mice from lethal infection with SARS-CoV.
In order to gain entry into cells, diverse viruses, including Ebola virus, SARS-coronavirus and the emerging MERS-coronavirus, depend on activation of their envelope glycoproteins by host cell proteases. The respective enzymes are thus excellent targets for antiviral intervention. In cell culture, activation of Ebola virus, as well as SARS- and MERS-coronavirus can be accomplished by the endosomal cysteine proteases, cathepsin L (CTSL) and cathepsin B (CTSB). In addition, SARS- and MERS-coronavirus can use serine proteases localized at the cell surface, for their activation. However, it is currently unclear which protease(s) facilitate viral spread in the infected host. We report here that the cysteine protease inhibitor K11777, ((2S)-N-[(1E,3S)-1-(benzenesulfonyl)-5-phenylpent-1-en-3-yl]-2-{[(E)-4-methylpiperazine-1-carbonyl]amino}-3-phenylpropanamide) and closely-related vinylsulfones act as broad-spectrum antivirals by targeting cathepsin-mediated cell entry. K11777 is already in advanced stages of development for a number of parasitic diseases, such as Chagas disease, and has proven to be safe and effective in a range of animal models. K11777 inhibition of SARS-CoV and Ebola virus entry was observed in the sub-nanomolar range. In order to assess whether cysteine or serine proteases promote viral spread in the host, we compared the antiviral activity of an optimized K11777-derivative with that of camostat, an inhibitor of TMPRSS2 and related serine proteases. Employing a pathogenic animal model of SARS-CoV infection, we demonstrated that viral spread and pathogenesis of SARS-CoV is driven by serine rather than cysteine proteases and can be effectively prevented by camostat. Camostat has been clinically used to treat chronic pancreatitis, and thus represents an exciting potential therapeutic for respiratory coronavirus infections. Our results indicate that camostat, or similar serine protease inhibitors, might be an effective option for treatment of SARS and potentially MERS, while vinyl sulfone-based inhibitors are excellent lead candidates for Ebola virus therapeutics.
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Affiliation(s)
- Yanchen Zhou
- Blood Systems Research Institute, San Francisco, CA 94118, USA; Department of Laboratory Medicine, University of California, San Francisco, San Francisco, CA 94118, USA
| | - Punitha Vedantham
- Small Molecule Discovery Center and Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Kai Lu
- Blood Systems Research Institute, San Francisco, CA 94118, USA
| | - Juliet Agudelo
- Blood Systems Research Institute, San Francisco, CA 94118, USA
| | - Ricardo Carrion
- Texas Biomedical Research Institute, San Antonio, TX 78227, USA
| | | | - Dale Barnard
- Institute for Antiviral Research, Department of Animal, Dairy and Veterinary Science, Utah State University, Logan, UT 84322, USA
| | - Stefan Pöhlmann
- Infection Biology Unit, German Primate Center, 37077 Göttingen, Germany
| | - James H McKerrow
- Department of Pathology and Center for Discovery and Innovation in Parasitic Diseases, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Adam R Renslo
- Small Molecule Discovery Center and Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Graham Simmons
- Blood Systems Research Institute, San Francisco, CA 94118, USA; Department of Laboratory Medicine, University of California, San Francisco, San Francisco, CA 94118, USA.
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Palgen JL, Jurgens EM, Moscona A, Porotto M, Palermo LM. Unity in diversity: shared mechanism of entry among paramyxoviruses. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2014; 129:1-32. [PMID: 25595799 DOI: 10.1016/bs.pmbts.2014.10.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The Paramyxoviridae family includes many viruses that are pathogenic in humans, including parainfluenza viruses, measles virus, respiratory syncytial virus, and the emerging zoonotic Henipaviruses. No effective treatments are currently available for these viruses, and there is a need for efficient antiviral therapies. Paramyxoviruses enter the target cell by binding to a cell surface receptor and then fusing the viral envelope with the target cell membrane, allowing the release of the viral genome into the cytoplasm. Blockage of these crucial steps prevents infection and disease. Binding and fusion are driven by two virus-encoded glycoproteins, the receptor-binding protein and the fusion protein, that together form the viral "fusion machinery." The development of efficient antiviral drugs requires a deeper understanding of the mechanism of action of the Paramyxoviridae fusion machinery, which is still controversial. Here, we review recent structural and functional data on these proteins and the current understanding of the mechanism of the paramyxovirus cell entry process.
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Affiliation(s)
- Jean-Louis Palgen
- Department of Pediatrics, Weill Cornell Medical College, Cornell University, New York, USA; Department of Biology, Ecole Normale Supérieure, Lyon, France
| | - Eric M Jurgens
- Department of Pediatrics, Weill Cornell Medical College, Cornell University, New York, USA
| | - Anne Moscona
- Department of Pediatrics, Weill Cornell Medical College, Cornell University, New York, USA; Department of Microbiology and Immunology, Weill Cornell Medical College, Cornell University, New York, USA
| | - Matteo Porotto
- Department of Pediatrics, Weill Cornell Medical College, Cornell University, New York, USA.
| | - Laura M Palermo
- Department of Pediatrics, Weill Cornell Medical College, Cornell University, New York, USA; Department of Microbiology and Immunology, Weill Cornell Medical College, Cornell University, New York, USA
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Monaghan P, Green D, Pallister J, Klein R, White J, Williams C, McMillan P, Tilley L, Lampe M, Hawes P, Wang LF. Detailed morphological characterisation of Hendra virus infection of different cell types using super-resolution and conventional imaging. Virol J 2014; 11:200. [PMID: 25428656 PMCID: PMC4254186 DOI: 10.1186/s12985-014-0200-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Accepted: 11/07/2014] [Indexed: 01/22/2023] Open
Abstract
BACKGROUND Hendra virus (HeV) is a pleomorphic virus belonging to the Paramyxovirus family. Our long-term aim is to understand the process of assembly of HeV virions. As a first step, we sought to determine the most appropriate cell culture system with which to study this process, and then to use this model to define the morphology of the virus and identify the site of assembly by imaging key virus encoded proteins in infected cells. METHODS A range of primary cells and immortalised cell lines were infected with HeV, fixed at various time points post-infection, labelled for HeV proteins and imaged by confocal, super-resolution and transmission electron microscopy. RESULTS Significant differences were noted in viral protein distribution depending on the infected cell type. At 8 hpi HeV G protein was detected in the endoplasmic reticulum and M protein was seen predominantly in the nucleus in all cells tested. At 18 hpi, HeV-infected Vero cells showed M and G proteins throughout the cell and in transmission electron microscope (TEM) sections, in pleomorphic virus-like structures. In HeV infected MDBK, A549 and HeLa cells, HeV M protein was seen predominantly in the nucleus with G protein at the membrane. In HeV-infected primary bovine and porcine aortic endothelial cells and two bat-derived cell lines, HeV M protein was not seen at such high levels in the nucleus at any time point tested (8,12, 18, 24, 48 hpi) but was observed predominantly at the cell surface in a punctate pattern co-localised with G protein. These HeV M and G positive structures were confirmed as round HeV virions by TEM and super-resolution (SR) microscopy. SR imaging demonstrated for the first time sub-virion imaging of paramyxovirus proteins and the respective localisation of HeV G, M and N proteins within virions. CONCLUSION These findings provide novel insights into the structure of HeV and show that for HeV imaging studies the choice of tissue culture cells may affect the experimental results. The results also indicate that HeV should be considered a predominantly round virus with a mean diameter of approximately 280 nm by TEM and 310 nm by SR imaging.
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Affiliation(s)
- Paul Monaghan
- CSIRO Australian Animal Health Laboratory, 5 Portarlington Road, Geelong, VIC, 3220, Australia.
| | - Diane Green
- CSIRO Australian Animal Health Laboratory, 5 Portarlington Road, Geelong, VIC, 3220, Australia.
| | - Jackie Pallister
- CSIRO Australian Animal Health Laboratory, 5 Portarlington Road, Geelong, VIC, 3220, Australia.
| | - Reuben Klein
- CSIRO Australian Animal Health Laboratory, 5 Portarlington Road, Geelong, VIC, 3220, Australia.
| | - John White
- CSIRO Australian Animal Health Laboratory, 5 Portarlington Road, Geelong, VIC, 3220, Australia.
| | - Catherine Williams
- CSIRO Australian Animal Health Laboratory, 5 Portarlington Road, Geelong, VIC, 3220, Australia.
| | - Paul McMillan
- Department of Biochemistry and Molecular Biology, Melbourne, Australia.
- ARC Centre of Excellence for Coherent X-ray Science, Melbourne, Australia.
- Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Melbourne, VIC, 3010, Australia.
- Current Address: Biological Optical Microscopy Platform, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Melbourne, VIC, 3010, Australia.
| | - Leann Tilley
- Department of Biochemistry and Molecular Biology, Melbourne, Australia.
- ARC Centre of Excellence for Coherent X-ray Science, Melbourne, Australia.
- Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Melbourne, VIC, 3010, Australia.
- Current Address: Biological Optical Microscopy Platform, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Melbourne, VIC, 3010, Australia.
| | - Marko Lampe
- Leica Microsystems, CMS GmbH, Ernst-Leitz Strasse 17-37, Wetzlar, Germany.
- Current Address: European Molecular Biology Laboratory, Meyerhofstr 1, D-69117, Heidelberg, Germany.
- Current Address: Translational Lung Research Center (TLRC), Department Translational Pulmonology, University of Heidelberg, Im Neuenheimer Feld 350, D-69120, Heidelberg, Germany.
| | - Pippa Hawes
- Pirbright Institute, Pirbright, Woking, Surrey, GU240NF, UK.
| | - Lin-Fa Wang
- CSIRO Australian Animal Health Laboratory, 5 Portarlington Road, Geelong, VIC, 3220, Australia.
- Duke-NUS Graduate Medical School, Singapore, Singapore.
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Theoretical insight into the mechanism for the inhibition of the cysteine protease cathepsin B by 1,2,4-thiadiazole derivatives. J Mol Model 2014; 20:2254. [DOI: 10.1007/s00894-014-2254-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Accepted: 04/21/2014] [Indexed: 10/25/2022]
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Mattera R, Farías GG, Mardones GA, Bonifacino JS. Co-assembly of viral envelope glycoproteins regulates their polarized sorting in neurons. PLoS Pathog 2014; 10:e1004107. [PMID: 24831812 PMCID: PMC4022726 DOI: 10.1371/journal.ppat.1004107] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2013] [Accepted: 03/24/2014] [Indexed: 12/14/2022] Open
Abstract
Newly synthesized envelope glycoproteins of neuroinvasive viruses can be sorted in a polarized manner to the somatodendritic and/or axonal domains of neurons. Although critical for transneuronal spread of viruses, the molecular determinants and interregulation of this process are largely unknown. We studied the polarized sorting of the attachment (NiV-G) and fusion (NiV-F) glycoproteins of Nipah virus (NiV), a paramyxovirus that causes fatal human encephalitis, in rat hippocampal neurons. When expressed individually, NiV-G exhibited a non-polarized distribution, whereas NiV-F was specifically sorted to the somatodendritic domain. Polarized sorting of NiV-F was dependent on interaction of tyrosine-based signals in its cytosolic tail with the clathrin adaptor complex AP-1. Co-expression of NiV-G with NiV-F abolished somatodendritic sorting of NiV-F due to incorporation of NiV-G•NiV-F complexes into axonal transport carriers. We propose that faster biosynthetic transport of unassembled NiV-F allows for its proteolytic activation in the somatodendritic domain prior to association with NiV-G and axonal delivery of NiV-G•NiV-F complexes. Our study reveals how interactions of viral glycoproteins with the host's transport machinery and between themselves regulate their polarized sorting in neurons. Neurons are highly polarized cells exhibiting somatodendritic and axonal domains with distinct protein and lipid compositions. Some enveloped viruses target neurons by binding of the viral envelope glycoproteins to neuronal surface receptors. The ensuing fusion of the viral and neuronal membranes delivers the genetic material of the virus into the neurons. During viral replication in neurons, newly synthesized envelope glycoproteins are sorted to the somatodendritic and/or axonal domains. Although critical for viral propagation, the mechanisms responsible for this sorting are largely unknown. We studied the neuronal sorting of the attachment (NiV-G) and fusion (NiV-F) glycoproteins of Nipah virus, a pathogen that causes fatal human encephalitis. When analyzed individually, NiV-G was delivered to both the axonal and somatodendritic domains. In contrast, NiV-F was exclusively targeted to the somatodendritic domain by virtue of interaction of specific signals in this protein with AP-1, a component of the neuronal protein transport machinery. Assembly with NiV-G, however, abolished somatodendritic sorting of NiV-F due to incorporation of complexes into axon-bound vesicles. Thus, coordinated interactions of viral glycoproteins with the host's sorting machinery and between themselves allow temporal and spatial regulation of their distribution in neurons. We propose that this coordination facilitates viral spread among neurons.
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Affiliation(s)
- Rafael Mattera
- Cell Biology and Metabolism Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Ginny G. Farías
- Cell Biology and Metabolism Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Gonzalo A. Mardones
- Cell Biology and Metabolism Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Juan S. Bonifacino
- Cell Biology and Metabolism Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail:
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Rotaviruses reach late endosomes and require the cation-dependent mannose-6-phosphate receptor and the activity of cathepsin proteases to enter the cell. J Virol 2014; 88:4389-402. [PMID: 24501398 DOI: 10.1128/jvi.03457-13] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
UNLABELLED Rotaviruses (RVs) enter cells through different endocytic pathways. Bovine rotavirus (BRV) UK uses clathrin-mediated endocytosis, while rhesus rotavirus (RRV) employs an endocytic process independent of clathrin and caveolin. Given the differences in the cell internalization pathway used by these viruses, we tested if the intracellular trafficking of BRV UK was the same as that of RRV, which is known to reach maturing endosomes (MEs) to infect the cell. We found that BRV UK also reaches MEs, since its infectivity depends on the function of Rab5, the endosomal sorting complex required for transport (ESCRT), and the formation of endosomal intraluminal vesicles (ILVs). However, unlike RRV, the infectivity of BRV UK was inhibited by knocking down the expression of Rab7, indicating that it has to traffic to late endosomes (LEs) to infect the cell. The requirement for Rab7 was also shared by other RV strains of human and porcine origin. Of interest, most RV strains that reach LEs were also found to depend on the activities of Rab9, the cation-dependent mannose-6-phosphate receptor (CD-M6PR), and cathepsins B, L, and S, suggesting that cellular factors from the trans-Golgi network (TGN) need to be transported by the CD-M6PR to LEs to facilitate RV cell infection. Furthermore, using a collection of UK × RRV reassortant viruses, we found that the dependence of BRV UK on Rab7, Rab9, and CD-M6PR is associated with the spike protein VP4. These findings illustrate the elaborate pathway of RV entry and reveal a new process (Rab9/CD-M6PR/cathepsins) that could be targeted for drug intervention. IMPORTANCE Rotavirus is an important etiological agent of severe gastroenteritis in children. In most instances, viruses enter cells through an endocytic pathway that delivers the viral particle to vesicular organelles known as early endosomes (EEs). Some viruses reach the cytoplasm from EEs, where they start to replicate their genome. However, other viruses go deeper into the cell, trafficking from EEs to late endosomes (LEs) to disassemble and reach the cytoplasm. In this work, we show that most RV strains have to traffic to LEs, and the transport of endolysosomal proteases from the Golgi complex to LEs, mediated by the mannose-6-phosphate receptor, is necessary for the virus to exit the vesicular compartment and efficiently start viral replication. We also show that this deep journey into the cell is associated with the virus spike protein VP4. These findings illustrate the elaborate pathway of RV entry that could be used for drug intervention.
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Wei S, Huang Y, Huang X, Cai J, Yan Y, Guo C, Qin Q. Characterization of cathepsin B gene from orange-spotted grouper, Epinephelus coioides involved in SGIV infection. FISH & SHELLFISH IMMUNOLOGY 2014; 36:194-205. [PMID: 24239598 DOI: 10.1016/j.fsi.2013.11.006] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2013] [Revised: 11/01/2013] [Accepted: 11/04/2013] [Indexed: 06/02/2023]
Abstract
The lysosomal cysteine protease cathepsin B of papain family is a key regulator and signaling molecule that involves in various biological processes, such as the regulation of apoptosis and activation of virus. In the present study, cathepsin B gene (Ec-CB) was cloned and characterized from orange-spotted grouper, Epinephelus coioides. The full-length Ec-CB cDNA was composed of 1918 bp and encoded a polypeptide of 330 amino acids with higher identities to cathepsin B of teleosts and mammalians. Ec-CB possessed typical cathepsin B structural features including an N-terminal signal peptide, the propeptide region and the cysteine protease domain which were conserved in other cathepsin B sequences. Phylogenetic analysis revealed that Ec-CB was most closely related to Lutjanus argentimaculatus. RT-PCR analysis showed that Ec-CB transcript was expressed in all the examined tissues which abundant in spleen, kidney and gill. After challenged with Singapore grouper iridovirus (SGIV) stimulation, the mRNA expression of cathepsin B in E. coioides was up-regulated at 24 h post-infection. Subcellular localization analysis revealed that Ec-CB was distributed predominantly in the cytoplasm. When the fish cells (GS or FHM) were treated with the cathepsin B specific inhibitor CA-074Me, the occurrence of CPE induced by SGIV was delayed, and the viral gene transcription was significantly inhibited. Additionally, SGIV-induced typical apoptosis was also inhibited by CA-074Me in FHM cells. Taken together, our results demonstrated that the Ec-CB might play a functional role in SGIV infection.
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Affiliation(s)
- Shina Wei
- Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, 164 West Xingang Road, Guangzhou 510301, China
| | - Youhua Huang
- Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, 164 West Xingang Road, Guangzhou 510301, China
| | - Xiaohong Huang
- Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, 164 West Xingang Road, Guangzhou 510301, China
| | - Jia Cai
- Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, 164 West Xingang Road, Guangzhou 510301, China; University of Chinese Academy of Sciences, 19 Yuquan Road, Beijing 100049, China
| | - Yang Yan
- Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, 164 West Xingang Road, Guangzhou 510301, China
| | - Chuanyu Guo
- Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, 164 West Xingang Road, Guangzhou 510301, China; University of Chinese Academy of Sciences, 19 Yuquan Road, Beijing 100049, China
| | - Qiwei Qin
- Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, 164 West Xingang Road, Guangzhou 510301, China.
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Weis M, Behner L, Hoffmann M, Krüger N, Herrler G, Drosten C, Drexler JF, Dietzel E, Maisner A. Characterization of African bat henipavirus GH-M74a glycoproteins. J Gen Virol 2013; 95:539-548. [PMID: 24296468 DOI: 10.1099/vir.0.060632-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
In recent years, novel henipavirus-related sequences have been identified in bats in Africa. To evaluate the potential of African bat henipaviruses to spread in non-bat mammalian cells, we compared the biological functions of the surface glycoproteins G and F of the prototype African henipavirus GH-M74a with those of the glycoproteins of Nipah virus (NiV), a well-characterized pathogenic member of the henipavirus genus. Glycoproteins are central determinants for virus tropism, as efficient binding of henipavirus G proteins to cellular ephrin receptors and functional expression of fusion-competent F proteins are indispensable prerequisites for virus entry and cell-to-cell spread. In this study, we analysed the ability of the GH-M74a G and F proteins to cause cell-to-cell fusion in mammalian cell types readily permissive to NiV or Hendra virus infections. Except for limited syncytium formation in a bat cell line derived from Hypsignathus monstrosus, HypNi/1.1 cells, we did not observe any fusion. The highly restricted fusion activity was predominantly due to the F protein. Whilst GH-M74a G protein was found to interact with the main henipavirus receptor ephrin-B2 and induced syncytia upon co-expression with heterotypic NiV F protein, GH-M74a F protein did not cause evident fusion in the presence of heterotypic NiV G protein. Pulse-chase and surface biotinylation analyses revealed delayed F cleavage kinetics with a reduced expression of cleaved and fusion-active GH-M74a F protein on the cell surface. Thus, the F protein of GH-M74a showed a functional defect that is most likely caused by impaired trafficking leading to less efficient proteolytic activation and surface expression.
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Affiliation(s)
- Michael Weis
- Institute of Virology, Philipps University Marburg, Marburg, Germany
| | - Laura Behner
- Institute of Virology, Philipps University Marburg, Marburg, Germany
| | - Markus Hoffmann
- Institute of Virology, University of Veterinary Medicine Hannover, Hannover, Germany
| | - Nadine Krüger
- Institute of Virology, University of Veterinary Medicine Hannover, Hannover, Germany
| | - Georg Herrler
- Institute of Virology, University of Veterinary Medicine Hannover, Hannover, Germany
| | - Christian Drosten
- Institute of Virology, University of Bonn Medical Centre, Bonn, Germany
| | - Jan Felix Drexler
- Institute of Virology, University of Bonn Medical Centre, Bonn, Germany
| | - Erik Dietzel
- Institute of Virology, Philipps University Marburg, Marburg, Germany
| | - Andrea Maisner
- Institute of Virology, Philipps University Marburg, Marburg, Germany
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Kopitar-Jerala N. The role of cysteine proteinases and their inhibitors in the host-pathogen cross talk. Curr Protein Pept Sci 2013; 13:767-75. [PMID: 23305363 PMCID: PMC3594739 DOI: 10.2174/138920312804871102] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2012] [Revised: 07/17/2012] [Accepted: 07/25/2012] [Indexed: 01/12/2023]
Abstract
Proteinases and their inhibitors play essential functional roles in basic biological processes in both hosts and pathogens. Endo/lysosomal cathepsins participate in immune response in pathogen recognition and elimination. They are essential for both antigen processing and presentation (host adaptive immune response) and activation of endosomal Toll like receptors (innate immune response). Pathogens can produce proteases and also natural inhibitors to subvert the host immune response. Several pathogens are sensed through the intracellular pathogen recognition receptors, but only some of them use the host proteolytic system to escape into the cytosol. In this review, I provide an update on the most recent developments regarding the role of proteinases and their inhibitors in the initiation and regulation of immune responses.
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Affiliation(s)
- Natasa Kopitar-Jerala
- Department of Biochemistry, Molecular and Structural Biology, ›Jozef Stefan‹ Institute, Jamova 39, 1000 Ljubljana, Slovenia.
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Chitranshi N, Tiwari AK, Somvanshi P, Tripathi PK, Seth PK. Investigating the function of single nucleotide polymorphisms in the CTSB gene: a computational approach. FUTURE NEUROLOGY 2013. [DOI: 10.2217/fnl.13.26] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Aim: Recent genome-wide association studies have revealed large numbers of single nucleotide polymorphisms (SNPs) related to Alzheimer’s disease. Here, we have investigated the gene CTSB, which plays a crucial role in encoding CTSB, a lysosomal cysteine proteinase protein. CTSB is also involved in the proteolytic processing of amyloid precursor protein (APP), which is believed to be a causative factor in Alzheimer’s disease. Materials & methods: Several bioinformatics algorithms such as, Sorting Intolerant from Tolerant (SIFT), Polymorphism Phenotyping (PolyPhen) and CUPSAT could identify the synonymous SNPs and nonsynonymous SNPs (nsSNPs), which are predicted to be deleterious and nondeleterious, respectively. Similar tools were used to predict the impact of single amino acid substitutions on CTSB protein activity. The FASTSNP server and UTRscan were used to predict the influence on splicing regulations. The stability and solvent-accessible surface area of modeled mutated proteins were analyzed using PBEQ solver and NetASA view. Furthermore, the DSP program was used to determine the secondary structures of the modeled protein. Results: A total of 999 SNPs in CTSB were retrieved from the SNP database; 55 nsSNPs, 35 synonymous SNPs, 165 mRNA were found in the 3´untranslated region SNPs, 12 SNPs were found in the 5´untranslated region in addition to 732 intronic SNPs. Potential functions of SNPs in the CTSB gene were identified using different web servers. For example, SIFT, PolyPhen and CUPSAT servers predicted ten nsSNPs to be intolerant, three nsSNPs to be damaging and eight nsSNPs to have the potential to destabilize protein structure. The FASTSNP server predicted 12 SNPs to influence splicing regulation, whereas two SNPs could predict a risk in the range of 3–4 (medium to high). Furthermore, mutant proteins were modeled and the total energy values were compared with the native CTSB protein. It was observed that on the surface of the protein, a mutation from threonine to serine at position 235 (rs17573) caused the greatest impact on stability. Conclusion: The genome-wide association studies database has already found rs7003814 of the CTSB gene reported against Alzheimer’s disease. Our study demonstrates the presence of other deleterious nsSNPs, which may play a crucial role in predicting Alzheimer’s disease risk.
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Affiliation(s)
- Nitin Chitranshi
- Gautam Buddh Technical University, Lucknow 227202, Uttar Pradesh, India
- Bioinformatics Centre, Biotech Park, Sector-G, Jankipuram, Lucknow-226021, Uttar Pradesh, India.
| | - Amit K Tiwari
- Department of Biomedical Sciences, College of Veterinary Medicine, Nursing & Allied Health, Tuskegee University, Tuskegee, AL 36088, USA
| | - Pallavi Somvanshi
- Department of Biotechnology, TERI University, 10, Institutional Area, Vasantkunj, New Delhi 110070, India
| | | | - Prahlad K Seth
- Bioinformatics Centre, Biotech Park, Sector-G, Jankipuram, Lucknow-226021, Uttar Pradesh, India
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Witting SR, Vallanda P, Gamble AL. Characterization of a third generation lentiviral vector pseudotyped with Nipah virus envelope proteins for endothelial cell transduction. Gene Ther 2013; 20:997-1005. [PMID: 23698741 PMCID: PMC3839624 DOI: 10.1038/gt.2013.23] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Revised: 03/20/2013] [Accepted: 04/22/2013] [Indexed: 12/11/2022]
Abstract
Lentiviruses are becoming progressively more popular as gene therapy vectors due to their ability to integrate into quiescent cells and recent clinical trial successes. Directing these vectors to specific cell types and limiting off-target transduction in vivo remains a challenge. Replacing the viral envelope proteins responsible for cellular binding, or pseudotyping, remains a common method to improve lentiviral targeting. Here, we describe the development of a high titer, 3rd generation lentiviral vector pseudotyped with Nipah virus fusion protein (NiV-F) and attachment protein (NiV-G). Critical to high titers was truncation of the cytoplasmic domains of both NiV-F and NiV-G. As known targets of wild-type Nipah virus, primary endothelial cells are shown to be effectively transduced by the Nipah pseudotype. In contrast, human CD34+ hematopoietic progenitors were not significantly transduced. Additionally, the Nipah pseudotype has increased stability in human serum compared to VSV pseudotyped lentivirus. These findings suggest that the use of Nipah virus envelope proteins in 3rd generation lentiviral vectors would be a valuable tool for gene delivery targeted to endothelial cells.
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Affiliation(s)
- S R Witting
- Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN, USA
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Abstract
Filoviruses cause severe hemorrhagic fever in humans with high case-fatality rates. The cellular factors exploited by filoviruses for their spread constitute potential targets for intervention, but are incompletely defined. The viral glycoprotein (GP) mediates filovirus entry into host cells. Recent studies revealed important insights into the host cell molecules engaged by GP for cellular entry. The binding of GP to cellular lectins was found to concentrate virions onto susceptible cells and might contribute to the early and sustained infection of macrophages and dendritic cells, important viral targets. Tyrosine kinase receptors were shown to promote macropinocytic uptake of filoviruses into a subset of susceptible cells without binding to GP, while interactions between GP and human T cell Ig mucin 1 (TIM-1) might contribute to filovirus infection of mucosal epithelial cells. Moreover, GP engagement of the cholesterol transporter Niemann-Pick C1 was demonstrated to be essential for GP-mediated fusion of the viral envelope with a host cell membrane. Finally, mutagenic and structural analyses defined GP domains which interact with these host cell factors. Here, we will review the recent progress in elucidating the molecular interactions underlying filovirus entry and discuss their implications for our understanding of the viral cell tropism.
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Krzyzaniak MA, Zumstein MT, Gerez JA, Picotti P, Helenius A. Host cell entry of respiratory syncytial virus involves macropinocytosis followed by proteolytic activation of the F protein. PLoS Pathog 2013; 9:e1003309. [PMID: 23593008 PMCID: PMC3623752 DOI: 10.1371/journal.ppat.1003309] [Citation(s) in RCA: 205] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2012] [Accepted: 03/03/2013] [Indexed: 12/21/2022] Open
Abstract
Respiratory Syncytial Virus (RSV) is a highly pathogenic member of the Paramyxoviridae that causes severe respiratory tract infections. Reports in the literature have indicated that to infect cells the incoming viruses either fuse their envelope directly with the plasma membrane or exploit clathrin-mediated endocytosis. To study the entry process in human tissue culture cells (HeLa, A549), we used fluorescence microscopy and developed quantitative, FACS-based assays to follow virus binding to cells, endocytosis, intracellular trafficking, membrane fusion, and infection. A variety of perturbants were employed to characterize the cellular processes involved. We found that immediately after binding to cells RSV activated a signaling cascade involving the EGF receptor, Cdc42, PAK1, and downstream effectors. This led to a series of dramatic actin rearrangements; the cells rounded up, plasma membrane blebs were formed, and there was a significant increase in fluid uptake. If these effects were inhibited using compounds targeting Na+/H+ exchangers, myosin II, PAK1, and other factors, no infection was observed. The RSV was rapidly and efficiently internalized by an actin-dependent process that had all hallmarks of macropinocytosis. Rather than fusing with the plasma membrane, the viruses thus entered Rab5-positive, fluid-filled macropinosomes, and fused with the membranes of these on the average 50 min after internalization. Rab5 was required for infection. To find an explanation for the endocytosis requirement, which is unusual among paramyxoviruses, we analyzed the fusion protein, F, and could show that, although already cleaved by a furin family protease once, it underwent a second, critical proteolytic cleavage after internalization. This cleavage by a furin-like protease removed a small peptide from the F1 subunits, and made the virus infectious. Respiratory Syncytial Virus (RSV) is a highly pathogenic paramyxovirus. We developed assays for RSV endocytosis, intracellular trafficking, membrane fusion, and infection. The results showed that RSV was rapidly and efficiently internalized, and that acid-independent membrane fusion occurred intracellularly after endocytosis. Cell biological studies demonstrated that endocytosis was macropinocytic, and that it was required for infection. The process involved activation of the EGF receptor and its downstream effectors including Cdc42, Pak1, and myosin II. RSV induced transient actin rearrangements accompanied by plasma membrane blebbing, elevated fluid uptake, and internalization of intact RSV particles into large macropinosomes. Expression of a dominant negative Rab5 mutant but not Rab7 decreased infection indicating that RSV penetration is intracellular, and takes place in Rab5 positive macropinosomes before fusion with endolysosomal compartments. The reason why RSV, unlike most paramyxoviruses, depended on endocytic entry was found to be the need for activation of the F protein by a second proteolytic cleavage. It occurred after endocytosis, and involved most likely a furin-like, vacuolar enzyme.
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Affiliation(s)
| | | | | | - Paola Picotti
- Institute of Biochemistry, ETH Zurich, Zurich, Switzerland
| | - Ari Helenius
- Institute of Biochemistry, ETH Zurich, Zurich, Switzerland
- * E-mail:
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Abstract
Highly pathogenic Nipah virus (NiV) infections are transmitted via airway secretions and urine, commonly via the respiratory route. Epithelial surfaces represent important replication sites in both primary and systemic infection phases. NiV entry and spread from polarized epithelial cells therefore determine virus entry and dissemination within a new host and influence virus shedding via mucosal surfaces in the respiratory and urinary tract. To date, there is no knowledge regarding the entry and exit sites of NiV in polarized epithelial cells. In this report, we show for the first time that NiV can infect polarized kidney epithelial cells (MDCK) from both cell surfaces, while virus release is primarily restricted to the apical plasma membrane. Substantial amounts of basolateral infectivity were detected only after infection with high virus doses, at time points when the integrity of the cell monolayer was largely disrupted as a result of cell-to-cell fusion. Confocal immunofluorescence analyses of envelope protein distribution at early and late infection stages suggested that apical virus budding is determined by the polarized sorting of the NiV matrix protein, M. Studies with stably M-expressing and with monensin-treated cells furthermore demonstrated that M protein transport is independent from the glycoproteins, implying that the M protein possesses an intrinsic apical targeting signal.
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