Vesicular stomatitis virus G protein transmembrane region is crucial for the hemi-fusion to full fusion transition

Yali Ci,Lei Shi,Caimin Xu,Yang Yang

doi:10.1038/s41598-018-28868-y

Yali Ci, Lei Shi + Show 2 more

Open Access

https://doi.org/10.1038/s41598-018-28868-y

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Abstract

Viral fusion proteins are essential for enveloped virus infection. These proteins mediate fusion between the virus envelope and host cellular membrane to release the viral genome into cells. Vesicular stomatitis virus G (VSV G) protein is a typical type III viral fusion protein. To study the mechanism of VSV G protein mediated membrane fusion, we set up a cell-cell fusion system in which cells are marked by different fluorescent proteins. Taking advantage of this system, we performed real-time recording and quantitative analysis of the cell fusion mediated by VSV G. We found that the time scale required for VSV G mediated cell-cell fusion was approximately 1–2 minutes. Next, we specifically examined the function of the transmembrane (TM) region of VSV G protein in membrane fusion by replacing the TM region with those of other fusion proteins. The TM region replacements dramatically impaired VSV G protein function in the cell-cell fusion assay and diminished VSV G mediated lentivirus and recombinant VSV infection efficiency. Further experiments implied that the TM region played a role in the transition from hemi-fusion to full fusion. Several residues within the TM region were identified as important for membrane fusion. Overall, our findings unraveled the important function of the TM region in VSV G mediated viral fusion.

Highlights

Membrane fusion is a universal and important biological phenomenon involved in multiple physiological and pathological processes, ranging from cell fusion and organelle dynamics to vesicle trafficking and viral infection[1,2,3,4,5]
To interpret these apparently conflicting results, we studied the function of the virus G protein (VSV G) protein TM region through cell-cell fusion assays and viral infection assays
We report here that the TM region was important for VSV G protein mediated membrane fusion and viral infection

Summary

Introduction

Membrane fusion is a universal and important biological phenomenon involved in multiple physiological and pathological processes, ranging from cell fusion and organelle dynamics to vesicle trafficking and viral infection[1,2,3,4,5]. The SNARE proteins on vesicles (v-SNARE) and those on target membranes (t-SNARE) provide recognition specificity and the energy needed for vesicle fusion[9] Viral fusion is another important fusion event. Evidence from some other viral fusion proteins and SNAREs indicates that the TM regions are essential for membrane fusion[23,24,25] To interpret these apparently conflicting results, we studied the function of the VSV G protein TM region through cell-cell fusion assays and viral infection assays. Our findings provide new insight into the mechanism of VSV G mediated virus fusion and suggest a common rule in which the TM region acts as a key element for the fusion activity of versatile membrane fusion proteins

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