Francisella tularensis is a highly infectious bacterium that causes the potentially lethal disease tularemia. This extremely virulent bacterium is able to replicate in the cytosolic compartments of infected macrophages. To invade macrophages and to cope with their intracellular environment, Francisella requires multiple virulence factors, which are still being identified. Proteins containing tetratricopeptide repeat (TPR)-like domains seem to be promising targets to investigate, since these proteins have been reported to be directly involved in virulence-associated functions of bacterial pathogens. Here, we studied the role of the FTS_0201, FTS_0778, and FTS_1680 genes, which encode putative TPR-like proteins in Francisella tularensis subsp. holarctica FSC200. Mutants defective in protein expression were prepared by TargeTron insertion mutagenesis. We found that the locus FTS_1680 and its ortholog FTT_0166c in the highly virulent Francisella tularensis type A strain SchuS4 are required for proper intracellular replication, full virulence in mice, and heat stress tolerance. Additionally, the FTS_1680-encoded protein was identified as a membrane-associated protein required for full cytopathogenicity in macrophages. Our study thus identifies FTS_1680/FTT_0166c as a new virulence factor in Francisella tularensis.

• MeSH
• bakteriální proteiny genetika   metabolismus   MeSH
• cytosol mikrobiologie   MeSH
• faktory virulence genetika   metabolismus   MeSH
• Francisella tularensis genetika   růst a vývoj   fyziologie   MeSH
• genetické lokusy * MeSH
• genový knockout MeSH
• inzerční mutageneze MeSH
• makrofágy mikrobiologie   MeSH
• modely nemocí na zvířatech MeSH
• myši inbrední BALB C MeSH
• tularemie mikrobiologie   patologie   MeSH
• virulence MeSH
• zvířata MeSH
• Check Tag
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

The Francisella tularensis strain LVS phagosome disintegrates during the first few hours after bacterial entry and microbes are released to the cytosol. Within 12 h both rapid multiplication of microbes and a steep increase of apoptosis of infected macrophages occur. We searched for signals involved in the death of macrophages and detected molecules associated with the autophagy machinery cathepsin D, PTEN, p53 and LC3, whose levels or modification were influenced by ongoing in vitro tularemic infection. The sequestration of cytoplasmic F. tularensis LVS into autophagosomes was confirmed by co-localization of the LVS strain containing vacuoles with LC3 (an autophagosomal marker). We also demonstrated the presence of MHC II antigens in these autophagosomes, indicating that they might act as a source of endogenous tularemic antigens for presentation to CD4+ T lymphocytes.

• MeSH
• buněčná smrt genetika   imunologie   MeSH
• cytosol fyziologie   imunologie   mikrobiologie   MeSH
• financování organizované využití   MeSH
• fluorescenční mikroskopie využití   MeSH
• fosfohydroláza PTEN genetika   imunologie   izolace a purifikace   MeSH
• Francisella tularensis imunologie   izolace a purifikace   MeSH
• imunoblotting metody   využití   MeSH
• kathepsin D genetika   imunologie   izolace a purifikace   MeSH
• makrofágy imunologie   mikrobiologie   MeSH
• tularemie etiologie   imunologie   mikrobiologie   MeSH