Infectious Bronchitis Virus Nonstructural Protein 4 Alone Induces Membrane Pairing.

Nicole Doyle,Philippa Hawes,Helena Maier,Judith Mantell,Hasan Alrashedi,Paul Verkade,Benjamin Neuman,Jennifer Simpson

doi:10.3390/v10090477

Nicole Doyle, Philippa Hawes + Show 6 more

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https://doi.org/10.3390/v10090477

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Abstract

Positive-strand RNA viruses, such as coronaviruses, induce cellular membrane rearrangements during replication to form replication organelles allowing for efficient viral RNA synthesis. Infectious bronchitis virus (IBV), a pathogenic avian Gammacoronavirus of significant importance to the global poultry industry, has been shown to induce the formation of double membrane vesicles (DMVs), zippered endoplasmic reticulum (zER) and tethered vesicles, known as spherules. These membrane rearrangements are virally induced; however, it remains unclear which viral proteins are responsible. In this study, membrane rearrangements induced when expressing viral non-structural proteins (nsps) from two different strains of IBV were compared. Three non-structural transmembrane proteins, nsp3, nsp4, and nsp6, were expressed in cells singularly or in combination and the effects on cellular membranes investigated using electron microscopy and electron tomography. In contrast to previously studied coronaviruses, IBV nsp4 alone is necessary and sufficient to induce membrane pairing; however, expression of the transmembrane proteins together was not sufficient to fully recapitulate DMVs. This indicates that although nsp4 is able to singularly induce membrane pairing, further viral or host factors are required in order to fully assemble IBV replicative structures. This study highlights further differences in the mechanism of membrane rearrangements between members of the coronavirus family.

Highlights

Viruses rely on their host cell to provide most of what they need to replicate and in order to do this, they hijack many cellular processes
Our previous studies have shown that Infectious bronchitis virus (IBV) is able to induce diverse membrane rearrangements in
Induction of host cell membrane rearrangements is a tool used by many +RNA viruses, such as coronaviruses [1,2]

Summary

Introduction

Viruses rely on their host cell to provide most of what they need to replicate and in order to do this, they hijack many cellular processes. A well-studied example is the ability of positive-sense single-stranded RNA viruses (+RNA) to induce cellular membrane rearrangements upon expression of viral proteins [1,2]. This reorganization of cellular membranes is a critical step in the viral replication cycle since these areas of restructured membranes act as a site for assembly of all components required for viral RNA synthesis as well as offer protection from detection by the host antiviral defenses [3,4]. Most common are double membrane vesicles (DMVs), which are discrete from the cytoplasm and are produced by viruses, such as poliovirus [7,8], hepatitis C virus [9,10], human norovirus [11], and recently the equine torovirus, Berne virus [12]

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