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The amino terminus of the salmonid alphavirus capsid protein determines subcellular localization and inhibits cellular proliferation

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Abstract

Salmonid alphavirus (SAV) is the most divergent member of the family Togaviridae and constitutes a threat to farming of salmonid fish in Europe. Here, we report cloning, expression and preliminary functional analysis of the capsid protein of SAV, confirming it to be expressed as an approximately 31-kDa protein in infected cells. The protein localizes strictly to the cytoplasm in Chinook salmon embryo cells, and either to the nucleus or cytoplasm in bluegill fry cells. An expression study of full-length and different truncated versions of the SAV capsid fused to the enhanced green fluorescent protein demonstrated that the localization is independent of other viral components in both cell lines, and controlled by the N-terminal 82 aa, which include a conserved, predicted helix and a downstream positively charged region. Thus, the results suggest that the SAV capsid possesses a cell-type-dependent potential for nuclear import and export. Moreover, the SAV capsid and its N-terminal 82 aa were shown to be associated with inhibition of cellular proliferation, a hallmark of the cytopathic effect caused by SAV. These results highlight that the SAV capsid is a multifunctional protein with possible importance for pathogenesis.

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Acknowledgments

This work was funded by the University of Bergen and the Norwegian Research Council Grant 185188/S40. Confocal work was done using the Molecular Imaging Centre (MIC) facilities (FUGE platform), University of Bergen. MK is grateful to Endy Spriet at MIC for excellent assistance.

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Author notes

  1. Muhammed Naveed Yousaf

    Present address: Bodø University College, Bodø, Norway

Authors and Affiliations

  1. Department of Biology, University of Bergen, Thor Møhlens gate 55, 5020, Bergen, Norway

    Marius Karlsen & Are Nylund

  2. Norwegian School of Veterinary Science, Oslo, Norway

    Muhammed Naveed Yousaf & Espen Rimstad

  3. Intervet Norbio, Thor Møhlens gate 55, 5008, Bergen, Norway

    Stephane Villoing

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  1. Marius Karlsen
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  2. Muhammed Naveed Yousaf
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Correspondence to Marius Karlsen.

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Karlsen, M., Yousaf, M.N., Villoing, S. et al. The amino terminus of the salmonid alphavirus capsid protein determines subcellular localization and inhibits cellular proliferation. Arch Virol 155, 1281–1293 (2010). https://doi.org/10.1007/s00705-010-0717-x

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