1
|
Analysis of Hendra Virus Fusion Protein N-Terminal Transmembrane Residues. Viruses 2021; 13:v13122353. [PMID: 34960622 PMCID: PMC8707071 DOI: 10.3390/v13122353] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Revised: 11/22/2021] [Accepted: 11/23/2021] [Indexed: 11/17/2022] Open
Abstract
Hendra virus (HeV) is a zoonotic enveloped member of the family Paramyoxviridae. To successfully infect a host cell, HeV utilizes two surface glycoproteins: the attachment (G) protein to bind, and the trimeric fusion (F) protein to merge the viral envelope with the membrane of the host cell. The transmembrane (TM) region of HeV F has been shown to have roles in F protein stability and the overall trimeric association of F. Previously, alanine scanning mutagenesis has been performed on the C-terminal end of the protein, revealing the importance of β-branched residues in this region. Additionally, residues S490 and Y498 have been demonstrated to be important for F protein endocytosis, needed for the proteolytic processing of F required for fusion. To complete the analysis of the HeV F TM, we performed alanine scanning mutagenesis to explore the residues in the N-terminus of this region (residues 487-506). In addition to confirming the critical roles for S490 and Y498, we demonstrate that mutations at residues M491 and L492 alter F protein function, suggesting a role for these residues in the fusion process.
Collapse
|
2
|
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.
Collapse
|
3
|
Barrett CT, Neal HE, Edmonds K, Moncman CL, Thompson R, Branttie JM, Boggs KB, Wu CY, Leung DW, Dutch RE. Effect of clinical isolate or cleavage site mutations in the SARS-CoV-2 spike protein on protein stability, cleavage, and cell-cell fusion. J Biol Chem 2021; 297:100902. [PMID: 34157282 PMCID: PMC8214756 DOI: 10.1016/j.jbc.2021.100902] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Revised: 06/08/2021] [Accepted: 06/18/2021] [Indexed: 12/14/2022] Open
Abstract
The trimeric severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein (S) is the sole viral protein responsible for both viral binding to a host cell and the membrane fusion event needed for cell entry. In addition to facilitating fusion needed for viral entry, S can also drive cell-cell fusion, a pathogenic effect observed in the lungs of SARS-CoV-2-infected patients. While several studies have investigated S requirements involved in viral particle entry, examination of S stability and factors involved in S cell-cell fusion remain limited. A furin cleavage site at the border between the S1 and S2 subunits (S1/S2) has been identified, along with putative cathepsin L and transmembrane serine protease 2 cleavage sites within S2. We demonstrate that S must be processed at the S1/S2 border in order to mediate cell-cell fusion and that mutations at potential cleavage sites within the S2 subunit alter S processing at the S1/S2 border, thus preventing cell-cell fusion. We also identify residues within the internal fusion peptide and the cytoplasmic tail that modulate S-mediated cell-cell fusion. In addition, we examined S stability and protein cleavage kinetics in a variety of mammalian cell lines, including a bat cell line related to the likely reservoir species for SARS-CoV-2, and provide evidence that proteolytic processing alters the stability of the S trimer. This work therefore offers insight into S stability, proteolytic processing, and factors that mediate S cell-cell fusion, all of which help give a more comprehensive understanding of this high-profile therapeutic target.
Collapse
Affiliation(s)
- Chelsea T Barrett
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, USA
| | - Hadley E Neal
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, USA
| | - Kearstin Edmonds
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, USA
| | - Carole L Moncman
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, USA
| | - Rachel Thompson
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, USA
| | - Jean M Branttie
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, USA
| | - Kerri Beth Boggs
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, USA
| | - Cheng-Yu Wu
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, USA
| | - Daisy W Leung
- Division of Infectious Diseases, Department of Medicine, Washington University School of Medicine in St Louis, St Louis, Missouri, USA
| | - Rebecca E Dutch
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, USA.
| |
Collapse
|
4
|
Barrett CT, Neal HE, Edmonds K, Moncman CL, Thompson R, Branttie JM, Boggs KB, Wu CY, Leung DW, Dutch RE. Effect of mutations in the SARS-CoV-2 spike protein on protein stability, cleavage, and cell-cell fusion function. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2021:2021.01.24.428007. [PMID: 33532777 PMCID: PMC7852270 DOI: 10.1101/2021.01.24.428007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The SARS-CoV-2 spike protein (S) is the sole viral protein responsible for both viral binding to a host cell and the membrane fusion event needed for cell entry. In addition to facilitating fusion needed for viral entry, S can also drive cell-cell fusion, a pathogenic effect observed in the lungs of SARS-CoV-2 infected patients. While several studies have investigated S requirements involved in viral particle entry, examination of S stability and factors involved in S cell-cell fusion remain limited. We demonstrate that S must be processed at the S1/S2 border in order to mediate cell-cell fusion, and that mutations at potential cleavage sites within the S2 subunit alter S processing at the S1/S2 border, thus preventing cell-cell fusion. We also identify residues within the internal fusion peptide and the cytoplasmic tail that modulate S cell-cell fusion. Additionally, we examine S stability and protein cleavage kinetics in a variety of mammalian cell lines, including a bat cell line related to the likely reservoir species for SARS-CoV-2, and provide evidence that proteolytic processing alters the stability of the S trimer. This work therefore offers insight into S stability, proteolytic processing, and factors that mediate S cell-cell fusion, all of which help give a more comprehensive understanding of this highly sought-after therapeutic target.
Collapse
Affiliation(s)
- Chelsea T. Barrett
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, USA
| | - Hadley E. Neal
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, USA
| | - Kearstin Edmonds
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, USA
| | - Carole L. Moncman
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, USA
| | - Rachel Thompson
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, USA
| | - Jean M. Branttie
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, USA
| | - Kerri Beth Boggs
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, USA
| | - Cheng-Yu Wu
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, USA
| | - Daisy W. Leung
- Division of Infection Diseases, Department of Medicine, Washington University School of Medicine in St. Louis, St. Louis, Missouri, USA
| | - Rebecca E. Dutch
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, USA
| |
Collapse
|
5
|
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.
Collapse
|
6
|
Barrett CT, Dutch RE. Viral Membrane Fusion and the Transmembrane Domain. Viruses 2020; 12:v12070693. [PMID: 32604992 PMCID: PMC7412173 DOI: 10.3390/v12070693] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Revised: 06/24/2020] [Accepted: 06/25/2020] [Indexed: 01/05/2023] Open
Abstract
Initiation of host cell infection by an enveloped virus requires a viral-to-host cell membrane fusion event. This event is mediated by at least one viral transmembrane glycoprotein, termed the fusion protein, which is a key therapeutic target. Viral fusion proteins have been studied for decades, and numerous critical insights into their function have been elucidated. However, the transmembrane region remains one of the most poorly understood facets of these proteins. In the past ten years, the field has made significant advances in understanding the role of the membrane-spanning region of viral fusion proteins. We summarize developments made in the past decade that have contributed to the understanding of the transmembrane region of viral fusion proteins, highlighting not only their critical role in the membrane fusion process, but further demonstrating their involvement in several aspects of the viral lifecycle.
Collapse
|