Regulation of expression and mechanism of secretion of the Toll/Interleukin-1 receptor protein C of uropathogenic E. coli
Immunology
Final Report Abstract
The research project explored the ability of the well-characterized uropathogenic Escherichia coli strain CFT073, which causes urinary tract infections, to sense its environment. We explored previously that CFT073 contains the virulence gene TIR-containing protein C (tcpC). Its product impairs innate immune cells by dampening the signaling of two important pattern recognition receptors. Pattern recognition receptors such as Toll-like receptors are crucial for the detection of infections by the host. We derived the name of the virulence factor from the Toll/Interleukin-1 receptor domain (TIR), which is present in Toll-like receptor proteins, their adapters and the Interleukin-1 receptor and is crucial for signaling. A number of pathogens including uropathogenic E. coli possess proteins with TIR-domains, which dampen innate immunity and increase their virulence. Overexpression of this virulence factor in CFT073 retards its replication. Therefore, the expression of tcpC needs to be controlled. Thus, we generated reporter constructs, which contain the putative promoter region of the tcpC gene. Within this region, we could define a transcription start and thus verify the region as promoter. Using these constructs, we found that increasing pH and glucose concentrations increase, while FeSO4 lowers promoter activity and thus defined the first set of environmental parameters influencing the promoter activity. We also reasoned that this important virulence factor of CFT073 has to be expressed in time before innate immune cells impose danger on the pathogen. We found that an uroepithelial and a monocytic cell line induce the tcpC promoter. If the bacteria are in close proximity to or intracellular in the monocytic cell line the promoter is induced the most. Potassium is the most abundant intracellular ion and present in the urine. This prompted us to test whether potassium activates the tcpC promoter as well. Potassium concentrations within the physiological range stimulate the promoter efficiently. Sodium, which is present in high concentration in the kidney was reported to act as an antibacterial shield and might present a further stimulus to activate the virulence promoter. Indeed, sodium also increased the activity of the promoter. The promoter activity of genes is usually fine-tuned by regulatory proteins. In case of the tcpC promoter, we defined the protein H-NS as a negative regulator. H-NS is known to impair the transcriptional activity of foreign DNA, i.e. DNA, which was introduced into the genome of the host-bacterium. The tcpC gene is located in a small pathogenicity island, which was transferred into the genome of the E. coli strain CFT073. Taken together the project successfully defined different factors present in the urinary tract, which activate the promoter of an important virulence gene of a well-characterized uropathogenic E. coli strain.
Publications
- 2021. Regulation of Expression of the TIR-Containing Protein C Gene of the Uropathogenic Escherichia coli Strain CFT073. Pathogens. 10:549
Ittensohn J, J. Hemberger, H. Griffiths, M. Keller, S. Albrecht S, and T. Miethke
(See online at https://doi.org/10.3390/pathogens10050549) - 2021. TcpC inhibits toll-like receptor signaling pathway by serving as an E3 ubiquitin ligase that promotes degradation of myeloid differentiation factor 88. PLoS Pathog.;17:e1009481
Fang, J. Q., Q. Ou, J. Pan, J. Fang, D. Y. Zhang, M. Q. Qiu, Y. Q. Li, X. H.Wang, X. Y. Yang, Z. Chi, W. Gao,J. P. Guo, T. Miethke, and J. P. Pan
(See online at https://doi.org/10.1371/journal.ppat.1009481)
