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Mechanisms of Bacterial Expulsion as a Cell Autonomous Defense Strategy In the Bladder Epithelium

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Date
2015
Author
Miao, Yuxuan
Advisor
Abraham, Soman N.
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Abstract

Due to its close proximity to the gastrointestinal tract, the human urinary tract is

subjected to constant barrage by gut-­associated bacteria. However, for the most part, this tract has resisted infection by various microbes. The impregnability of the urinary tract to microbial colonization is attributable to the ability of the bladder to promptly sense and mount robust responses to microbial challenge. A powerful mechanism for the elimination of invading bacteria was recently described in bladder epithelial cells, involving non-­lytic ejection of intracellular bacteria back into the extracellular milieu. In spite of the effectiveness of this defense strategy, much of the underlying mechanisms surrounding how this powerful cellular defense activity detects intracellular UPEC and shuttles them from their intracellular location to the plasma membrane of BECs to be exported remains largely a mystery.

Here, we describe uropathogenic E.coli (UPEC) expelled from infected bladder

epithelium cells (BECs) within membrane-­bound vesicles as a distinct cellular defense

response. Examination of the intracellular UPEC revealed that intracellular bacteria were

initially processed via autophagy, the conventional degradative pathway, then delivered

into multivesicular bodies (MVBs) and encapsulated in nascent intraluminal vesicle membrane. We further show the bacterial expulsion is triggered when intracellular UPEC follow the natural degradative trafficking pathway and reach lysosomes and attempt to neutralize its pH to avoid degradation. This pathogen-­mediated activity is detected by mucolipin TRP channel 3 (TRPML3), a transient receptor potential cation channel localized on lysosomes, which spontaneously initiates lysosome exocytosis resulting in expulsion of exosome-­encased bacteria. These studies reveal a cellular default system for lysosome homeostasis and also, how it is coopted by the autonomous defense program to clear recalcitrant pathogens.

Type
Dissertation
Department
Molecular Genetics and Microbiology
Subject
Immunology
Microbiology
Cellular biology
Autophagy
Bacterial Expulsion
Exosome secretion
Lysosome exocytosis
TRPMLs
Urinary tract infection
Permalink
https://hdl.handle.net/10161/9862
Citation
Miao, Yuxuan (2015). Mechanisms of Bacterial Expulsion as a Cell Autonomous Defense Strategy In the Bladder Epithelium. Dissertation, Duke University. Retrieved from https://hdl.handle.net/10161/9862.
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This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 United States License.

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