Down-regulation of granulocyte-macrophage colony-stimulating factor by 3C-like proteinase in transfected A549 human lung carcinoma cells

BMC Immunol. 2011 Feb 17:12:16. doi: 10.1186/1471-2172-12-16.


Background: Severe Acute Respiratory Syndrome (SARS) is a severe respiratory illness caused by a novel virus, the SARS coronavirus (SARS-CoV). 3C-like protease (3CLpro) of SARS-CoV plays a role in processing viral polypeptide precursors and is responsible of viral maturation. However, the function of 3CLpro in host cells remains unknown. This study investigated how the 3CLpro affected the secretion of cytokines in the gene-transfected cells.

Results: From immunofluorescence microscopy, the localization of c-myc tagged 3CLpro was detected both in the cytoplasm and nucleus of transfected A549 cells. Expression of granulocyte-macrophage colony-stimulating factor (GM-CSF) was significantly decreased in 3CLpro-transfected cells by both RT-PCR and ELISA, but without changes in other cytokines, i.e., IL-1β, IL-6, IL-8, IL12p40, TNF-α, and TGF-β. Furthermore, the protein levels of NF-kB decreased in 3CLpro-transfected A549 cells when compared to EGFP transfected cells.

Conclusions: Our results suggest that the 3CLpro may suppress expression of GM-CSF in transfected A549 cells through down-regulation of NF-kB production.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Blotting, Western
  • Cell Line, Tumor
  • Coronavirus 3C Proteases
  • Cysteine Endopeptidases / genetics
  • Cysteine Endopeptidases / metabolism*
  • Down-Regulation*
  • Enzyme-Linked Immunosorbent Assay
  • Granulocyte-Macrophage Colony-Stimulating Factor / genetics
  • Granulocyte-Macrophage Colony-Stimulating Factor / metabolism*
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • Humans
  • Interleukin-12 Subunit p40 / metabolism
  • Interleukin-1beta / metabolism
  • Interleukin-6 / metabolism
  • Interleukin-8 / metabolism
  • Lung Neoplasms / genetics
  • Lung Neoplasms / metabolism
  • Lung Neoplasms / pathology
  • Microscopy, Fluorescence
  • Mutation
  • NF-kappa B / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction
  • Transfection
  • Transforming Growth Factor beta / metabolism
  • Tumor Necrosis Factor-alpha / metabolism
  • Viral Proteins / genetics
  • Viral Proteins / metabolism*


  • Interleukin-12 Subunit p40
  • Interleukin-1beta
  • Interleukin-6
  • Interleukin-8
  • NF-kappa B
  • Transforming Growth Factor beta
  • Tumor Necrosis Factor-alpha
  • Viral Proteins
  • Green Fluorescent Proteins
  • Granulocyte-Macrophage Colony-Stimulating Factor
  • Cysteine Endopeptidases
  • Coronavirus 3C Proteases