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Virologie

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Role of calcium ion in replication and structure of rotaviruses Volume 2, issue 2, Mars-Avril 1998

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Rotaviruses are members of the Reoviridae family and the major etiologic agent of gastroenteritis of children and young animals. Rotaviruses are non enveloped, large icosahedral particles having a complex structure consisting of three concentric capsid layers surrounding a genome of eleven segments of double-stranded RNA. Viral replication occurs exclusively in the cell cytoplasm. It is the only virus that has a unique morphogenesis in which particles obtain a transient membrane-envelope as newly made subviral particles bud into the endoplasmic reticulum. Calcium is present in the viral capsid and is responsible for the stability of the outer capsid layer. The concentration of Ca 2 + solubilizing outer capsid proteins from rotavirus particles is dependent on the virus strain but it is always in the range of the cytoplasmic [Ca 2 +] around 100 nM. Solubilization of the outer proteins plays a role in virus entry and uncoating and triggers the structural transcriptase. With progression of the infection, the synthesis of a viral product induces an intracellular [Ca 2+] increase allowing the assembly of the outer protein layer and leading to cellular death. The nonstructural glycoprotein NSP4 may be responsible for the increase in cytosolic calcium observed in rotavirus-infected cells and acting as a viral enterotoxin, could induce diarrhoea by a calcium-dependent signaling pathway.