The essential role of the CopN protein in Chlamydia pneumonia intracellular growth

Jin Huang, et al. Nature 2008; 456: 112-117

Speaker: Chih-Yu Huang (黃智郁)                               Time: 15:00-16:00, Sep. 23, 2009

Commentator: Dr. Jiunn-Jong Wu (吳俊忠老師) Place: Room 601

Abstract:

Chlamydia pneumoniae, an obligate intracellular pathogen, can replicate within a membrane-bound vacuole called inclusion body and cause pneumonia. It has long been recognized that the bacterial virulence determinants can be identified based on the approach known as “molecular Koch’s postulate”¹. However, this approach is limited to the genetically tractable organisms but not C. pneumoniae. The yeast Saccharomyces cerevisiae has been demonstrated to be a powerful system for determining the functions of a bacterial virulence protein², probing the eukaryotic cellular processes and modeling the mammalian infections. In this study, by expressing five probable virulence proteins of C. pneumoniae in yeast, the authors found that only CopN could inhibit yeast growth and resulted in the accumulation of large-budded yeast. Flow cytometry analysis revealed that the yeast expressing CopN was arrested at the G2/M phase of the cell cycle and it was owing to the alterations of microtubule cytoskeleton. The expression of CopN also similarly induced a G2/M cell cycle arrest in the mammalian cells. To investigate the role of CopN during infection, a library of about 40,000 small compounds were screened for those that could recover the growth of CopN-expressing yeast. Two compounds, 0433YC1 and 0433YC2, were found to reproducibly restore the growth of CopN-expressing yeast. In the mammalian cells, treatment of infected cells with these compounds resulted in a significantly reduced intracellular replication of C. pneumoniae and absence of large inclusion bodies. Collectively, with the CopN inhibitors identified in yeast, it was demonstrated that CopN is required for intracellular growth of C. pneumoniae and thus plays an important role in virulence in the cell culture model of infection.

References:

1.          Falkow, S. Molecular Koch’s postulates applied to microbial pathogenicity. Rev. Infect. Dis. 10 (Suppl. 2), S274-276 (1988)

2.          Lesser, C.F. and Miller, S. I. expression of microbial virulence proteins in Saccharomyces cerevisiae models mammalian infection. EMBO J. 20,1840-1849 (2001)