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Effects of the immunosuppressive bacterial protein TcpC on the inflammasome pathway

Zheng, Yunji (2015) MOBN01 20141
Degree Projects in Molecular Biology
Abstract
Recently, uropathogenic Escherichia coli were shown to express a virulence factor that specifically inhibits Toll-like receptor (TLR) signaling. The TIR-domain protein C (TcpC), has high homology with the TIR (Toll Interleukin Receptor) domains of innate immune signaling molecules such as TLR4, TRIF, TRAM and MyD88. By binding to these domains, TcpC prevents TIR homodimerization and inhibits innate immune signaling.

This project investigated the effect of TcpC on the activation and secretion of IL-1βand on the interaction of TcpC with the NLRP3 inflammasome. We show in human bladder epithelial cells representing the mucosa that infection with the Escherichia coli strain CFT073 increases the expression of IL-1β, NACHT leucine-rich PYD... (More)
Recently, uropathogenic Escherichia coli were shown to express a virulence factor that specifically inhibits Toll-like receptor (TLR) signaling. The TIR-domain protein C (TcpC), has high homology with the TIR (Toll Interleukin Receptor) domains of innate immune signaling molecules such as TLR4, TRIF, TRAM and MyD88. By binding to these domains, TcpC prevents TIR homodimerization and inhibits innate immune signaling.

This project investigated the effect of TcpC on the activation and secretion of IL-1βand on the interaction of TcpC with the NLRP3 inflammasome. We show in human bladder epithelial cells representing the mucosa that infection with the Escherichia coli strain CFT073 increases the expression of IL-1β, NACHT leucine-rich PYD domains-containing protein 3 (NLRP3) and Caspase-1 but infection did not affect adaptor molecule apoptosis-associated speck like protein (ASC). Compared to CFT073 wild type a mutant strain lacking TcpC, CFT073 tcpC::kan, showed increased nuclear staining for IL-1β and caspase-1. There was no difference in IL-1 β processing or secretion between CFT073wt and mutant strains in those cells. In macrophages, in contrast, this difference in nuclear staining was not observed but TcpC reduced the secretion of IL-1β via NLRP3 and caspase-­1. By confocal microscopy colocalization, TcpC was shown to interact directly with NLRP3 and caspase-1, inhibit caspase-1 and impair mature IL-1β secretion. In summary, TcpC differentially affects TLR-signaling and inflammasome responses in epithelial cells and macrophages. (Less)
Popular Abstract
How do bacteria modify the host innate immune system?

Urinary tract infection is one of the most common bacterial infections in humans. Depending on the site of infection and the severity of disease UTIs are diagnosed as acute pyelonephritis, acute cystitis or asymptomatic bacteriuria. The severity reflects the inflammatory response to infection, which also is needed to eliminate the bacteria from the infected tissues. Bacteria try to survive in the infected host by defending themselves against this host response To avoid the attack from human immune defense, these microbes have evolved sophisticated molecular strategies to inhibit the immune response. This project focuses on Escherichia coli CFT073 that inhibits the host immune system... (More)
How do bacteria modify the host innate immune system?

Urinary tract infection is one of the most common bacterial infections in humans. Depending on the site of infection and the severity of disease UTIs are diagnosed as acute pyelonephritis, acute cystitis or asymptomatic bacteriuria. The severity reflects the inflammatory response to infection, which also is needed to eliminate the bacteria from the infected tissues. Bacteria try to survive in the infected host by defending themselves against this host response To avoid the attack from human immune defense, these microbes have evolved sophisticated molecular strategies to inhibit the immune response. This project focuses on Escherichia coli CFT073 that inhibits the host immune system by secreting the protein TcpC.

TcpC, known as TIR-domain containing protein C, inhibits Toll-like receptor molecules (TLRs )by binding to adaptor proteins like MyD88. TLRs are sensors, recognizing specific pathogenic molecular patterns, and activate the innate immune response. The inflammasome which is regulated by the TLRs is a multiprotein consisted by caspase-1, NLRPs, and ASC. Inflammasome proteins are working together to cleave the important cytokine pro-IL-1β to active IL-1β, which is important for the innate immune response. In this project, I have examined if IL-1β and inflammasome signaling are activated by infection, and if TcpC inhibits inflammasome response.

Results
We show that infection of human bladder epithelial cells with the E. coli strain CFT073 increases the expression of IL-1β, NACHT leucine-rich PYD domains-containing protein 3 (NLRP3)and Caspase-1 by uro-epithelial cells. Compared to CFT073 wild type the mutant strain CFT073 tcpC::kan showed increased nuclear staining for IL-1β and caspase-1. In contrast, there was no difference in IL-1β processing or secretion between CFT073wt and mutant strains in those cells. In macrophages, this difference in nuclear staining was not observed but TcpC reduced the secretion of IL-1β via NLRP3 and caspase-1. By colocalization, TcpC interacted directly with NLRP3 and caspase-1 and inhibited caspase-1 and impaired mature IL-1β secretion. In summary, TcpC differentially affects TLR-signaling and inflammasome responses in epithelial cells and macrophages.

Advisor: Catharina Svanborg
Master´s Degree Project 45 credits in Molecular biology 2015
Department of Biology, Lund University (Less)
Please use this url to cite or link to this publication:
author
Zheng, Yunji
supervisor
organization
course
MOBN01 20141
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
7763951
date added to LUP
2015-08-18 14:53:39
date last changed
2015-08-19 08:25:35
@misc{7763951,
  abstract     = {Recently, uropathogenic Escherichia coli were shown to express a virulence factor that specifically inhibits Toll-like receptor (TLR) signaling. The TIR-domain protein C (TcpC), has high homology with the TIR (Toll Interleukin Receptor) domains of innate immune signaling molecules such as TLR4, TRIF, TRAM and MyD88. By binding to these domains, TcpC prevents TIR homodimerization and inhibits innate immune signaling.

This project investigated the effect of TcpC on the activation and secretion of IL-1βand on the interaction of TcpC with the NLRP3 inflammasome. We show in human bladder epithelial cells representing the mucosa that infection with the Escherichia coli strain CFT073 increases the expression of IL-1β, NACHT leucine-rich PYD domains-containing protein 3 (NLRP3) and Caspase-1 but infection did not affect adaptor molecule apoptosis-associated speck like protein (ASC). Compared to CFT073 wild type a mutant strain lacking TcpC, CFT073 tcpC::kan, showed increased nuclear staining for IL-1β and caspase-1. There was no difference in IL-1 β processing or secretion between CFT073wt and mutant strains in those cells. In macrophages, in contrast, this difference in nuclear staining was not observed but TcpC reduced the secretion of IL-1β via NLRP3 and caspase-­1. By confocal microscopy colocalization, TcpC was shown to interact directly with NLRP3 and caspase-1, inhibit caspase-1 and impair mature IL-1β secretion. In summary, TcpC differentially affects TLR-signaling and inflammasome responses in epithelial cells and macrophages.},
  author       = {Zheng, Yunji},
  language     = {eng},
  note         = {Student Paper},
  title        = {Effects of the immunosuppressive bacterial protein TcpC on the inflammasome pathway},
  year         = {2015},
}