title: Severe acute respiratory syndrome-associated coronavirus 3a protein forms an ion channel and modulates virus release.
abstract: Fourteen ORFs have been identified in the severe acute respiratory syndrome-associated coronavirus (SARS-CoV) genome. ORF 3a of SARS-CoV codes for a recently identified transmembrane protein, but its function remains unknown. In this study we confirmed the 3a protein expression and investigated its localization at the surface of SARS-CoV-infected or 3a-cDNA-transfected cells. Our experiments showed that recombinant 3a protein can form a homotetramer complex through interprotein disulfide bridges in 3a-cDNA-transfected cells, providing a clue to ion channel function. The putative ion channel activity of this protein was assessed in 3a-complement RNA-injected Xenopus oocytes by two-electrode voltage clamp. The results suggest that 3a protein forms a potassium sensitive channel, which can be efficiently inhibited by barium. After FRhK-4 cells were transfected with an siRNA, which is known to suppress 3a expression, followed by infection with SARS-CoV, the released virus was significantly decreased, whereas the replication of the virus in the infected cells was not changed. Our observation suggests that SARS-CoV ORF 3a functions as an ion channel that may promote virus release. This finding will help to explain the highly pathogenic nature of SARS-CoV and to develop new strategies for treatment of SARS infection.
authors.affiliation: Laboratory of Molecular Virology, Institut Pasteur of Shanghai, Chinese Academy of Sciences, 225 South Chongqing Road, Shanghai 200025, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Lu
authors.forename: Bo-Jian
authors.initials: BJ
authors.lastname: Zheng
authors.forename: Ke
authors.initials: K
authors.lastname: Xu
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Schwarz
authors.forename: Lanying
authors.initials: L
authors.lastname: Du
authors.forename: Charlotte K L
authors.initials: CK
authors.lastname: Wong
authors.forename: Jiadong
authors.initials: J
authors.lastname: Chen
authors.forename: Shuming
authors.initials: S
authors.lastname: Duan
authors.forename: Vincent
authors.initials: V
authors.lastname: Deubel
authors.forename: Bing
authors.initials: B
authors.lastname: Sun
mesh_terms: D000818:Animals; D002460:Cell Line; D006801:Humans; D007473:Ion Channels / Q000235:genetics / Q000378:metabolism*; D009865:Oocytes / Q000166:cytology / Q000502:physiology; D016366:Open Reading Frames; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D045473:Severe acute respiratory syndrome-related coronavirus / Q000235:genetics / Q000378:metabolism*; D014759:Viral Envelope Proteins; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*; D000086082:Viroporin Proteins; D014779:Virus Replication; D014982:Xenopus laevis
chemical_list: C487105:3a protein, SARS-CoV; D007473:Ion Channels; D034741:RNA, Small Interfering; D011994:Recombinant Proteins; D014759:Viral Envelope Proteins; D014764:Viral Proteins; D000086082:Viroporin Proteins; D011188:Potassium