Receptor Binding-Induced Conformational Changes in Herpes Simplex Virus Glycoprotein D Permit Interaction with the gH/gL Complex to Activate Fusion
Herpes simplex virus (HSV) requires four essential virion glycoproteins—gD, gH, gL, and gB—for virus entry and cell fusion. To initiate fusion, the receptor binding protein gD interacts with one of two major cell receptors, HVEM or nectin-1. Once gD binds to a receptor, fusion is carried out by the...
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| Format: | Article |
| Language: | English |
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MDPI AG
2023-03-01
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| Series: | Viruses |
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| Online Access: | https://www.mdpi.com/1999-4915/15/4/895 |
| _version_ | 1797603183644639232 |
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| author | Doina Atanasiu Wan Ting Saw Tina M. Cairns Harvey M. Friedman Roselyn J. Eisenberg Gary H. Cohen |
| author_facet | Doina Atanasiu Wan Ting Saw Tina M. Cairns Harvey M. Friedman Roselyn J. Eisenberg Gary H. Cohen |
| author_sort | Doina Atanasiu |
| collection | DOAJ |
| description | Herpes simplex virus (HSV) requires four essential virion glycoproteins—gD, gH, gL, and gB—for virus entry and cell fusion. To initiate fusion, the receptor binding protein gD interacts with one of two major cell receptors, HVEM or nectin-1. Once gD binds to a receptor, fusion is carried out by the gH/gL heterodimer and gB. A comparison of free and receptor-bound gD crystal structures revealed that receptor binding domains are located within residues in the N-terminus and core of gD. Problematically, the C-terminus lies across and occludes these binding sites. Consequentially, the C-terminus must relocate to allow for both receptor binding and the subsequent gD interaction with the regulatory complex gH/gL. We previously constructed a disulfide bonded (K190C/A277C) protein that locked the C-terminus to the gD core. Importantly, this mutant protein bound receptor but failed to trigger fusion, effectively separating receptor binding and gH/gL interaction. Here, we show that “unlocking” gD by reducing the disulfide bond restored not only gH/gL interaction but fusion activity as well, confirming the importance of C-terminal movement in triggering the fusion cascade. We characterize these changes, showing that the C-terminus region exposed by unlocking is: (1) a gH/gL binding site; (2) contains epitopes for a group (competition community) of monoclonal antibodies (Mabs) that block gH/gL binding to gD and cell–cell fusion. Here, we generated 14 mutations within the gD C-terminus to identify residues important for the interaction with gH/gL and the key conformational changes involved in fusion. As one example, we found that gD L268N was antigenically correct in that it bound most Mabs but was impaired in fusion, exhibited compromised binding of MC14 (a Mab that blocks both gD–gH/gL interaction and fusion), and failed to bind truncated gH/gL, all events that are associated with the inhibition of C-terminus movement. We conclude that, within the C-terminus, residue 268 is essential for gH/gL binding and induction of conformational changes and serves as a flexible inflection point in the critical movement of the gD C-terminus. |
| first_indexed | 2024-03-11T04:26:50Z |
| format | Article |
| id | doaj.art-139f9394e3f1442584ed5210e04d903e |
| institution | Directory Open Access Journal |
| issn | 1999-4915 |
| language | English |
| last_indexed | 2024-03-11T04:26:50Z |
| publishDate | 2023-03-01 |
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| record_format | Article |
| series | Viruses |
| spelling | doaj.art-139f9394e3f1442584ed5210e04d903e2023-11-17T21:45:18ZengMDPI AGViruses1999-49152023-03-0115489510.3390/v15040895Receptor Binding-Induced Conformational Changes in Herpes Simplex Virus Glycoprotein D Permit Interaction with the gH/gL Complex to Activate FusionDoina Atanasiu0Wan Ting Saw1Tina M. Cairns2Harvey M. Friedman3Roselyn J. Eisenberg4Gary H. Cohen5Department of Basic and Translational Sciences, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA 19104, USADepartment of Basic and Translational Sciences, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA 19104, USADepartment of Basic and Translational Sciences, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA 19104, USASchool of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USASchool of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA 19104, USADepartment of Basic and Translational Sciences, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA 19104, USAHerpes simplex virus (HSV) requires four essential virion glycoproteins—gD, gH, gL, and gB—for virus entry and cell fusion. To initiate fusion, the receptor binding protein gD interacts with one of two major cell receptors, HVEM or nectin-1. Once gD binds to a receptor, fusion is carried out by the gH/gL heterodimer and gB. A comparison of free and receptor-bound gD crystal structures revealed that receptor binding domains are located within residues in the N-terminus and core of gD. Problematically, the C-terminus lies across and occludes these binding sites. Consequentially, the C-terminus must relocate to allow for both receptor binding and the subsequent gD interaction with the regulatory complex gH/gL. We previously constructed a disulfide bonded (K190C/A277C) protein that locked the C-terminus to the gD core. Importantly, this mutant protein bound receptor but failed to trigger fusion, effectively separating receptor binding and gH/gL interaction. Here, we show that “unlocking” gD by reducing the disulfide bond restored not only gH/gL interaction but fusion activity as well, confirming the importance of C-terminal movement in triggering the fusion cascade. We characterize these changes, showing that the C-terminus region exposed by unlocking is: (1) a gH/gL binding site; (2) contains epitopes for a group (competition community) of monoclonal antibodies (Mabs) that block gH/gL binding to gD and cell–cell fusion. Here, we generated 14 mutations within the gD C-terminus to identify residues important for the interaction with gH/gL and the key conformational changes involved in fusion. As one example, we found that gD L268N was antigenically correct in that it bound most Mabs but was impaired in fusion, exhibited compromised binding of MC14 (a Mab that blocks both gD–gH/gL interaction and fusion), and failed to bind truncated gH/gL, all events that are associated with the inhibition of C-terminus movement. We conclude that, within the C-terminus, residue 268 is essential for gH/gL binding and induction of conformational changes and serves as a flexible inflection point in the critical movement of the gD C-terminus.https://www.mdpi.com/1999-4915/15/4/895HSVglycoproteinsprotein–protein interactionsconformational changesantibodies |
| spellingShingle | Doina Atanasiu Wan Ting Saw Tina M. Cairns Harvey M. Friedman Roselyn J. Eisenberg Gary H. Cohen Receptor Binding-Induced Conformational Changes in Herpes Simplex Virus Glycoprotein D Permit Interaction with the gH/gL Complex to Activate Fusion Viruses HSV glycoproteins protein–protein interactions conformational changes antibodies |
| title | Receptor Binding-Induced Conformational Changes in Herpes Simplex Virus Glycoprotein D Permit Interaction with the gH/gL Complex to Activate Fusion |
| title_full | Receptor Binding-Induced Conformational Changes in Herpes Simplex Virus Glycoprotein D Permit Interaction with the gH/gL Complex to Activate Fusion |
| title_fullStr | Receptor Binding-Induced Conformational Changes in Herpes Simplex Virus Glycoprotein D Permit Interaction with the gH/gL Complex to Activate Fusion |
| title_full_unstemmed | Receptor Binding-Induced Conformational Changes in Herpes Simplex Virus Glycoprotein D Permit Interaction with the gH/gL Complex to Activate Fusion |
| title_short | Receptor Binding-Induced Conformational Changes in Herpes Simplex Virus Glycoprotein D Permit Interaction with the gH/gL Complex to Activate Fusion |
| title_sort | receptor binding induced conformational changes in herpes simplex virus glycoprotein d permit interaction with the gh gl complex to activate fusion |
| topic | HSV glycoproteins protein–protein interactions conformational changes antibodies |
| url | https://www.mdpi.com/1999-4915/15/4/895 |
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