In vitro reconstitution of herpes simplex virus 1 fusion identifies low pH as a fusion co-trigger
ABSTRACTMembrane fusion mediated by herpes simplex virus 1 (HSV-1) is a complex, multi-protein process that is receptor triggered and can occur both at the cell surface and in endosomes. To deconvolute this complexity, we reconstituted HSV-1 fusion with synthetic lipid vesicles in vitro. Using this...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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American Society for Microbiology
2023-12-01
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| Series: | mBio |
| Subjects: | |
| Online Access: | https://journals.asm.org/doi/10.1128/mbio.02087-23 |
| _version_ | 1797378861051150336 |
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| author | J. Martin Ramirez Ariana C. Calderon-Zavala Ariane Balaram Ekaterina E. Heldwein |
| author_facet | J. Martin Ramirez Ariana C. Calderon-Zavala Ariane Balaram Ekaterina E. Heldwein |
| author_sort | J. Martin Ramirez |
| collection | DOAJ |
| description | ABSTRACTMembrane fusion mediated by herpes simplex virus 1 (HSV-1) is a complex, multi-protein process that is receptor triggered and can occur both at the cell surface and in endosomes. To deconvolute this complexity, we reconstituted HSV-1 fusion with synthetic lipid vesicles in vitro. Using this simplified, controllable system, we discovered that HSV-1 fusion required not only a cognate host receptor but also low pH. On the target membrane side, efficient fusion required cholesterol, negatively charged lipids found in the endosomal membranes, and an optimal balance of lipid order and disorder. On the virion side, the four HSV-1 entry glycoproteins—gB, gD, gH, and gL—were sufficient for fusion. We propose that low pH is a biologically relevant co-trigger for HSV-1 fusion. The dependence of fusion on low pH and endosomal lipids could explain why HSV-1 enters most cell types by endocytosis. We hypothesize that under neutral pH conditions, other, yet undefined, cellular factors may serve as fusion co-triggers. The in vitro fusion system established here can be employed to systematically investigate HSV-1-mediated membrane fusion.IMPORTANCEHSV-1 causes lifelong, incurable infections and diseases ranging from mucocutaneous lesions to fatal encephalitis. Fusion of viral and host membranes is a critical step in HSV-1 infection of target cells that requires multiple factors on both the viral and host sides. Due to this complexity, many fundamental questions remain unanswered, such as the identity of the viral and host factors that are necessary and sufficient for HSV-1-mediated membrane fusion and the nature of the fusion trigger. Here, we developed a simplified in vitro fusion assay to examine the fusion requirements and identified low pH as a co-trigger for virus-mediated fusion in vitro. We hypothesize that low pH has a critical role in cell entry and, potentially, pathogenesis. |
| first_indexed | 2024-03-08T20:13:43Z |
| format | Article |
| id | doaj.art-1482a92641794a5794fda17c4fefc753 |
| institution | Directory Open Access Journal |
| issn | 2150-7511 |
| language | English |
| last_indexed | 2024-03-08T20:13:43Z |
| publishDate | 2023-12-01 |
| publisher | American Society for Microbiology |
| record_format | Article |
| series | mBio |
| spelling | doaj.art-1482a92641794a5794fda17c4fefc7532023-12-22T19:53:44ZengAmerican Society for MicrobiologymBio2150-75112023-12-0114610.1128/mbio.02087-23In vitro reconstitution of herpes simplex virus 1 fusion identifies low pH as a fusion co-triggerJ. Martin Ramirez0Ariana C. Calderon-Zavala1Ariane Balaram2Ekaterina E. Heldwein3Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, USADepartment of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, USADepartment of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, USADepartment of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, USAABSTRACTMembrane fusion mediated by herpes simplex virus 1 (HSV-1) is a complex, multi-protein process that is receptor triggered and can occur both at the cell surface and in endosomes. To deconvolute this complexity, we reconstituted HSV-1 fusion with synthetic lipid vesicles in vitro. Using this simplified, controllable system, we discovered that HSV-1 fusion required not only a cognate host receptor but also low pH. On the target membrane side, efficient fusion required cholesterol, negatively charged lipids found in the endosomal membranes, and an optimal balance of lipid order and disorder. On the virion side, the four HSV-1 entry glycoproteins—gB, gD, gH, and gL—were sufficient for fusion. We propose that low pH is a biologically relevant co-trigger for HSV-1 fusion. The dependence of fusion on low pH and endosomal lipids could explain why HSV-1 enters most cell types by endocytosis. We hypothesize that under neutral pH conditions, other, yet undefined, cellular factors may serve as fusion co-triggers. The in vitro fusion system established here can be employed to systematically investigate HSV-1-mediated membrane fusion.IMPORTANCEHSV-1 causes lifelong, incurable infections and diseases ranging from mucocutaneous lesions to fatal encephalitis. Fusion of viral and host membranes is a critical step in HSV-1 infection of target cells that requires multiple factors on both the viral and host sides. Due to this complexity, many fundamental questions remain unanswered, such as the identity of the viral and host factors that are necessary and sufficient for HSV-1-mediated membrane fusion and the nature of the fusion trigger. Here, we developed a simplified in vitro fusion assay to examine the fusion requirements and identified low pH as a co-trigger for virus-mediated fusion in vitro. We hypothesize that low pH has a critical role in cell entry and, potentially, pathogenesis.https://journals.asm.org/doi/10.1128/mbio.02087-23HSV-1VSV pseudotypemembrane fusionin vitro fusionlipidssynthetic liposomes |
| spellingShingle | J. Martin Ramirez Ariana C. Calderon-Zavala Ariane Balaram Ekaterina E. Heldwein In vitro reconstitution of herpes simplex virus 1 fusion identifies low pH as a fusion co-trigger mBio HSV-1 VSV pseudotype membrane fusion in vitro fusion lipids synthetic liposomes |
| title | In vitro reconstitution of herpes simplex virus 1 fusion identifies low pH as a fusion co-trigger |
| title_full | In vitro reconstitution of herpes simplex virus 1 fusion identifies low pH as a fusion co-trigger |
| title_fullStr | In vitro reconstitution of herpes simplex virus 1 fusion identifies low pH as a fusion co-trigger |
| title_full_unstemmed | In vitro reconstitution of herpes simplex virus 1 fusion identifies low pH as a fusion co-trigger |
| title_short | In vitro reconstitution of herpes simplex virus 1 fusion identifies low pH as a fusion co-trigger |
| title_sort | in vitro reconstitution of herpes simplex virus 1 fusion identifies low ph as a fusion co trigger |
| topic | HSV-1 VSV pseudotype membrane fusion in vitro fusion lipids synthetic liposomes |
| url | https://journals.asm.org/doi/10.1128/mbio.02087-23 |
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