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Single point mutation in tick-borne encephalitis virus prM protein induces a reduction of virus particle secretion
Kentarou Yoshii1, Akihiro Konno2, Akiko Goto1
1Laboratory of Public Health, Department of Environmental Veterinary Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan.
Abstract:
Flaviviruses are assembled to bud into the lumen of the endoplasmic reticulum (ER) and are secreted through the vesicle transport pathway. Virus envelope proteins play important roles in this process. In this study, the effect of mutations in the envelope proteins of tick-borne encephalitis (TBE) virus on secretion of virus-like particles (VLPs), using a recombinant plasmid expression system was analysed. It was found that a single point mutation at position 63 in prM induces a reduction in secretion of VLPs. The mutation in prM did not affect the folding of the envelope proteins, and chaperone-like activity of prM was maintained. As observed by immunofluorescence microscopy, viral envelope proteins with the mutation in prM were scarce in the Golgi complex, and accumulated in the ER. Electron microscopic analysis of cells expressing the mutated prM revealed that many tubular structures were present in the lumen. The insertion of the prM mutation at aa 63 into the viral genome reduced the production of infectious virus particles. This data suggest that prM plays a crucial role in the virus budding process.
Insights
A mutation in tick-borne encephalitis (TBE) virus prM protein significantly reduces virus-like particle (VLP) secretion. This prM mutation impairs VLP budding from the endoplasmic reticulum, impacting infectious virus production.
Area of Science:
- Virology
- Molecular Biology
- Cell Biology
Background:
- Flaviviruses, including tick-borne encephalitis (TBE) virus, assemble and bud into the endoplasmic reticulum (ER) lumen.
- Virus envelope proteins are critical for flavivirus secretion via the vesicle transport pathway.
- The prM protein is a key component of the flavivirus envelope, involved in maturation and assembly.
Purpose of the Study:
- To investigate the impact of mutations in TBE virus envelope proteins on virus-like particle (VLP) secretion.
- To elucidate the role of the prM protein in the flavivirus budding process.
Main Methods:
- Utilized a recombinant plasmid expression system to generate TBE virus VLPs.
- Analyzed the effect of a specific prM mutation (at position 63) on VLP secretion.
- Employed immunofluorescence microscopy and electron microscopy to examine protein localization and cellular structures.
Main Results:
- A single point mutation at position 63 in the prM protein significantly reduced VLP secretion.
- The prM mutation did not affect envelope protein folding or the chaperone-like activity of prM.
- Mutated viral envelope proteins accumulated in the ER, with scarce presence in the Golgi, and induced tubular structures in the ER lumen.
- Insertion of the prM mutation into the viral genome decreased infectious virus particle production.
Conclusions:
- The prM protein plays a crucial role in the flavivirus budding process from the ER.
- Specific mutations in prM can disrupt VLP secretion and infectious virus production by interfering with ER exit.
- The findings highlight prM's importance in regulating virus assembly and release.
