Year: 2017
Type: dissertation
Abstract: An inflammasome is a multi-protein complex that consists of a sensor protein, caspase-1, and often an adaptor protein ASC. An inflammasome assembles in response to microbial or danger signals and the assembly leads to autoproteolysis of pro-caspase-1 and, consequently, to processing of the inflammatory cytokines pro-IL-1β and pro-IL-18 and to a type of cell death called pyroptosis. NLRP1B is a cytosolic protein that forms an inflammasome in response to anthrax lethal toxin or reduction in cytosolic ATP levels. NLRP1B detects anthrax lethal toxin when the toxin cleaves an amino-terminal fragment from the protein. The mechanism by which NLRP1B senses reduction in cytosolic ATP is unknown. In chapter 3, I addressed whether the amino-terminal region of NLRP1B also serves as a sensor of reduced ATP levels. I found that an NLRP1B mutant lacking the amino- terminal region exhibited some spontaneous activity and failed to be further activated by lethal toxin, but was still activated by metabolic inhibitors, indicating that the amino-terminal region is not the sole sensing domain of NLRP1B. Comparison of NLRP1B alleles that differed in their response to metabolic inhibitors, but not to lethal toxin, led to the finding that a repeated sequence in the FIIND facilitated detection of ATP depletion. NLRP1B might sense ATP depletion as a way of sensing microbial infections. In chapter 4, I show that an infection with an intracellular pathogen, Listeria monocytogenes caused a reduction of cytosolic ATP levels and activation of the NLRP1B inflammasome in a reconstituted system. NLRP1B activation was dependent on Listeriaâ s expression of a protein required for vacuolar escape, listeriolysin O. Furthermore, I show that infection with Listeria monocytogenes and Shigella flexneri also caused reduction of ATP and activation of NLRP1B in the murine RAW264.7 macrophage cell line.
Source: TSpace (University of Toronto)
Author: Jana Neiman-Zenevich
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W3090867337