Cholesterol-Rich Lipid Rafts in the Cellular Membrane Play an Essential Role in Avian Reovirus Replication.

Yuyang Wang,Xiaorong Zhang,Yantao Wu,Hongyan Zhao,Chengcheng Zhang,Maozhi Hu,Qiuxiang Yan,Yangyang Zhang

doi:10.3389/fmicb.2020.597794

Abstract

Cholesterol is an essential component of lipid rafts in cellular plasma membranes. Although lipid rafts have been reported to have several functions in multiple stages of the life cycles of many different enveloped viruses, the mechanisms by which non-enveloped viruses, which lack outer lipid membranes, infect host cells remain unclear. In this study, to investigate the dependence of non-enveloped avian reovirus (ARV) infection on the integrity of cholesterol-rich membrane rafts, methyl-β-cyclodextrin (MβCD) was used to deplete cellular membrane cholesterol at the ARV attachment, entry, and post-entry stages. Treatment with MβCD significantly inhibited ARV replication at both the entry and post-entry stages in a dose-dependent manner, but MβCD had a statistically insignificant effect when it was added at the attachment stage. Moreover, MβCD treatment markedly reduced syncytium formation, which occurs at a relatively late stage of the ARV life cycle and is involved in cell-cell transmission and release. Furthermore, the addition of exogenous cholesterol reversed the effects mentioned above. Colocalization data also showed that the ARV proteins σC, μNS, and p10 prefer to localize to cholesterol-rich lipid raft regions during ARV infection. Altogether, these results suggest that cellular cholesterol in lipid rafts plays a critical role in ARV replication.

Highlights

Avian reovirus (ARV) is an important pathogen that causes viral arthritis syndrome and immunosuppression in domestic fowl, leading to considerable losses to the poultry industry (Jones and Kibenge, 1984; Neelima et al, 2003)
Cell membrane cholesterol was stained with filipin III, and the efficiency of cell membrane cholesterol removal by MβCD was
Cholesterol-rich lipid rafts are specific microdomains in the cell membrane enriched in cholesterol and sphingolipids (Brown and London, 2000)

Summary

Introduction

Avian reovirus (ARV) is an important pathogen that causes viral arthritis syndrome and immunosuppression in domestic fowl, leading to considerable losses to the poultry industry (Jones and Kibenge, 1984; Neelima et al, 2003). ARV has a genome of 10 double-stranded RNA (dsRNA) segments enclosed in a doubleprotein capsid shell. Based on their electrophoretic mobilities, these segments are divided into L (large), M (medium), and S (small) classes, which encode the proteins designated lambda (λ), mu (μ), and sigma (σ), respectively. ARV infection is initiated by the attachment of the outer capsid protein σC to cell surface receptors, and this binding event causes virions to enter cells through receptor-mediated endocytosis (Grande et al, 2002). The p10 protein probably plays a key role in virus release and dissemination It is a member of the fusion-associated small transmembrane (FAST) protein family composed of proteins that induce cellcell membrane fusion and syncytium formation (Ciechonska and Duncan, 2014; Duncan, 2019). Some details of the ARV life cycle are well known, the underlying mechanism on how ARV is internalized into cells remains controversial, and its virion assembly and release are still poorly understood

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Conclusion