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The Epstein-Barr virus (EBV) glycoprotein B cytoplasmic C-terminal tail domain regulates the energy requirement for EBV-induced membrane fusion.

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journal contribution
posted on 28.01.2016, 00:00 by J. Chen, X. Zhang, T.S. Jardetzky, R. Longnecker
The entry of enveloped viruses into host cells is preceded by membrane fusion, which in Epstein-Barr virus (EBV) is thought to be mediated by the refolding of glycoprotein B (gB) from a prefusion to a postfusion state. In our current studies, we characterized a gB C-terminal tail domain (CTD) mutant truncated at amino acid 843 (gB843). This truncation mutant is hyperfusogenic as monitored by syncytium formation and in a quantitative fusion assay and is dependent on gH/gL for fusion activity. gB843 can rescue the fusion function of other glycoprotein mutants that have null or decreased fusion activity in epithelial and B cells. In addition, gB843 requires less gp42 and gH/gL for fusion, and can function in fusion at a lower temperature than wild-type gB, indicating a lower energy requirement for fusion activation. Since a key step in fusion is the conversion of gB from a prefusion to an active postfusion state by gH/gL, gB843 may access this activated gB state more readily. Our studies indicate that the gB CTD may participate in the fusion function by maintaining gB in an inactive prefusion form prior to activation by receptor binding. Importance: Diseases resulting from Epstein-Barr virus (EBV) infection in humans range from the fairly benign disease infectious mononucleosis to life-threatening cancer. As an enveloped virus, EBV must fuse with a host cell membrane for entry and infection by using glycoproteins gH/gL, gB, and gp42. Among these glycoproteins, gB is thought to be the protein that executes fusion. To further characterize the function of the EBV gB cytoplasmic C-terminal tail domain (CTD) in fusion, we used a previously constructed CTD truncation mutant and studied its fusion activity in the context of other EBV glycoprotein mutants. From these studies, we find that the gB CTD regulates fusion by altering the energy requirements for the triggering of fusion mediated by gH/gL or gp42. Overall, our studies may lead to a better understanding of EBV fusion and entry, which may result in novel therapies that target the EBV entry step.

Funding

This research was supported by grant AI076183 (to R.L. and T.S.J.) from the National Institute of Allergy and Infectious Diseases, by grant CA117794 (to R.L. and T.S.J.) from the National Cancer Institute, and by postdoctoral fellowships 12POST9380013 (to J.C.) and 14POST18600021 (to J.C.) from the American Heart Association, Midwest Affiliate. This work was supported in part by the Katten Muchin Rosenman Travel Scholarship Program and the Robert H. Lurie Comprehensive Cancer Center of Northwestern University.

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Publisher Statement

This is a copy of an article published in the Journal of Virology © 2014 American Society for Microbiology Publications. jvi.asm.org

Publisher

American Society for Microbiology

issn

0022-538X

Issue date

01/10/2014

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