Characterization of the 3a protein of SARS-associated coronavirus in infected vero E6 cells and SARS patients.

Research Center for Proteome Analysis, Key Lab of Proteomics, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yue-Yang Road, Shanghai 200031, China.
Journal of Molecular Biology (Impact Factor: 3.96). 08/2004; 341(1):271-9. DOI: 10.1016/j.jmb.2004.06.016
Source: PubMed

ABSTRACT Proteomics was used to identify a protein encoded by ORF 3a in a SARS-associated coronavirus (SARS-CoV). Immuno-blotting revealed that interchain disulfide bonds might be formed between this protein and the spike protein. ELISA indicated that sera from SARS patients have significant positive reactions with synthesized peptides derived from the 3a protein. These results are concordant with that of a spike protein-derived peptide. A tendency exists for co-mutation between the 3a protein and the spike protein of SARS-CoV isolates, suggesting that the function of the 3a protein correlates with the spike protein. Taken together, the 3a protein might be tightly correlated to the spike protein in the SARS-CoV functions. The 3a protein may serve as a new clinical marker or drug target for SARS treatment.


Available from: Ruifu Yang, Apr 19, 2015
1 Follower
  • [Show abstract] [Hide abstract]
    ABSTRACT: In addition to a set of canonical genes, coronaviruses encode additional accessory proteins. A locus located between the spike and envelope genes is conserved in all coronaviruses and contains a complete or truncated open reading frame (ORF). Previously, we demonstrated that this locus, which contains the gene for accessory protein 3a from Severe Acute Respiratory Syndrome coronavirus (SARS-CoV), encodes a protein that forms ion channels and regulates virus release. In the current study, we explored whether the ORF4a protein of HCoV-229E has similar functions. Our findings revealed that ORF4a proteins were expressed in infected cells and localized at the endoplasmic reticulum/Golgi intermediate compartment (ERGIC). The ORF4a proteins formed homo-oligomers through disulfide bridges and possessed ion channel activity in both Xenopus oocytes and yeast. Based on measurement of conductance to different monovalent cations, the ORF4a was suggested to form a non-selective channel for monovalent cations, although Li(+) partially reduced the inward current. Furthermore, viral production decreased when ORF4a protein expression was suppressed by siRNA in infected cells. Collectively, this evidence indicates that the HCoV-229E ORF4a protein is functionally analogous to the SARS-CoV 3a protein, which also acts as a viroporin that regulates virus production. This article is part of a Special Issue entitled:Viral Membrane Proteins - Channels for Cellular Networking.
    Biochimica et Biophysica Acta 07/2013; 1838(4). DOI:10.1016/j.bbamem.2013.07.025 · 4.66 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The SARS coronavirus (SARS-CoV) 3a protein functions as an ion channel, induces apoptosis and is important for viral pathogenesis. It is expressed on the cell surface and contains a tyrosine-based sorting motif and a di-acidic motif, which may be crucial for its intracellular trafficking. However the role of these motifs is not fully understood in the case of 3a protein. The subcellular distribution of the 3a protein was studied by immunofluorescence staining of cells transfected with wild type and mutant constructs along with markers for different intracellular compartments. Semi-quantitative RT-PCR was performed to estimate the mRNA where as western blotting was carried out to detect protein levels of wild type and mutant 3a proteins. In vitro transcription- translation was performed to estimate cell free protein synthesis. While the wild type 3a protein is efficiently transported to the plasma membrane, the protein with mutations in the tyrosine and valine residues within the YXXV motif (DeltaYXXPhi) accumulated in the Golgi compartment. However the 3a protein with mutations within the EXD di-acidic motif (DeltaEXD) showed an intracellular distribution similar to the wild type protein. Increased retention of the DeltaYXXPhi protein in the Golgi compartment also increased its association with lipid droplets. The DeltaYXXPhi protein also expressed at significantly lower levels compared to the wild type 3a protein, which was reversed with Brefeldin A and Aprotonin. The data suggest that the YXXPhi motif of the SARS-CoV 3a protein is necessary for Golgi to plasma membrane transport, in the absence of which the protein is targeted to lysosomal degradation compartment via lipid droplets.
    Virology Journal 04/2014; 11(1):75. DOI:10.1186/1743-422X-11-75 · 2.09 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The huge RNA genome of SARS coronavirus comprises a number of open reading frames that code for a total of eight accessory proteins. Although none of these are essential for virus replication, some appear to have a role in virus pathogenesis. Notably, some SARS-CoV accessory proteins have been shown to modulate the interferon signaling pathways and the production of pro-inflammatory cytokines. The structural information on these proteins is also limited, with only two (p7a and p9b) having their structures determined by X-ray crystallography. This review makes an attempt to summarize the published knowledge on SARS-CoV accessory proteins, with an emphasis on their involvement in virus-host interaction. The accessory proteins of other coronaviruses are also briefly discussed. This paper forms part of a series of invited articles in Antiviral Research on "From SARS to MERS: 10years of research on highly pathogenic human coronaviruses" (see Introduction by R. Hilgenfeld & M. Peiris, Antiviral Res. 100, 286-295 (2013)).
    07/2014; 109. DOI:10.1016/j.antiviral.2014.06.013