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J. Virol. doi:10.1128/JVI.02076-07
Copyright (c) 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Functional Analysis of Picornavirus 2B Proteins: Effects on Calcium Homeostasis and Intracellular Protein Trafficking

Departments of Medical Microbiology and Biochemistry, Radboud University Nijmegen Medical Centre, Nijmegen Centre for Molecular Life Sciences, PO Box 9101, 6500 HB Nijmegen, The Netherlands

^* To whom correspondence should be addressed. Email: f.vankuppeveld{at}ncmls.ru.nl.

	Abstract

The family of Picornaviridae consists of a large group of plus-strand RNA viruses that share a similar genome organization. The nomenclature of the picornavirus proteins is based on their position in the viral RNA genome but does not necessarily imply a conserved function of proteins of the different genera. The enterovirus 2B protein is a small hydrophobic protein that upon individual expression is localized to the ER and Golgi complex and reduces ER and Golgi Ca²⁺ levels, most likely by forming transmembrane pores, and inhibits protein trafficking through the Golgi complex. At present, little is known about the function of the other picornavirus 2B proteins. Here, we show that rhinovirus 2B, which is phylogenetically closely related to enterovirus 2B, shows a similar subcellular localization and function as enterovirus 2B. In contrast, 2B of hepatitis A virus, foot-and-mouth disease virus, and encephalomyocarditis virus, all of which are more distantly related to enteroviruses, show a different localization and have little, if any, effects on Ca²⁺ homeostasis and intracellular protein trafficking. Our data suggest that 2B of enterovirus and rhinovirus share the same function in virus replication, while the other picornavirus 2B proteins support the viral life cycle in a different manner. Moreover, we show that an enterovirus 2B protein that is retained in the ER is unable to modify Ca²⁺ homeostasis and inhibit protein trafficking, demonstrating the importance of the Golgi localization for its functioning.