Differential localization and turnover of infectious bronchitis virus 3b protein in mammalian versus avian cells.
Infectious bronchitis virus (IBV) 3b protein is highly conserved among group 3 coronaviruses, suggesting that it is important for infection. A previous report (Virology 2003, 311:16-27) indicated that transfected IBV 3b localized to the nucleus in mammalian cells using a vaccinia-virus expression system. Although we confirmed these findings, we observed cytoplasmic localization of IBV 3b with apparent exclusion from the nucleus in avian cells (IBV normally infects chickens). IBV 3b was virtually undetectable by microscopy in mammalian cells transfected without vaccinia virus and in IBV-infected mammalian cells because of a greatly reduced half-life in these cells. A proteasome inhibitor stabilized IBV 3b in mammalian cells, but had little effect on IBV 3b in avian cells, suggesting that rapid turnover of IBV 3b in mammalian cells is proteasome-dependent while turnover in avian cells may be proteasome-independent. Our results highlight the importance of using cells derived from the natural host when studying coronavirus non-structural proteins.
Pendleton
Amanda R
AR
Department of Cell Biology, Johns Hopkins University School of Medicine, 725 N. Wolfe St., Baltimore, MD 21205, USA.
Machamer
Carolyn E
CE
D000818:Animals; D001717:Birds / Q000821:virology; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D002642:Chick Embryo; D006224:Cricetinae; D003593:Cytoplasm / Q000378:metabolism*; D006801:Humans; D001351:Infectious bronchitis virus / Q000378:metabolism* / Q000472:pathogenicity*; D008322:Mammals / Q000821:virology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D013045:Species Specificity; D014162:Transfection; D014616:Vaccinia virus / Q000235:genetics / Q000378:metabolism; D017361:Viral Nonstructural Proteins / Q000378:metabolism*
D017361:Viral Nonstructural Proteins; C118611:glycoprotein 3b, coronavirus; D046988:Proteasome Endopeptidase Complex