Sun, B (reprint author), Chinese Acad Prevent Med, Inst Pasteur, Mol Virol Lab, 225 S Chongqing Rd, Shanghai 200025, Peoples R China,email@example.com
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.
Lu, Wei; Zheng, Bo-Jian; Xu, Ke; Schwarz, Wolfgang; Du, Lanying; Wong, Charlotte K. L.; Chen, Jiandong; Duan, Shuming; Deubel, Vincent; Sun, Bing.Severe acute respiratory syndrome-associated coronavirus 3a protein forms an ion channel and modulates virus release,PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA,2006,103(33):12540-12545