Urinary tract infections (UTIs) continue to be the second most common bacterial infections in man. Most of these infections are caused by uropathogenic E. coli (UPEC) that gain access into bladder epithelial cells and persist intracellularly, where they are inaccessible to the immune system and also antibiotics. Remarkably, recent in vivo and in vitro studies on infected bladder epithelial cells have revealed that these cells have a powerful capacity to exocytose large proportions of infecting UPEC without loss of cell viability. These observations point to a powerful capacity of BECs to sense intracellular bacteria and initiate bacterial exocytosis. They also suggest that if the underlying mechanism were understood, it may be possible to utilize drugs targeting this pathway to boost this cellular defense mechanism. To date, using biochemical and molecular approaches, we have determined that a key molecule responsible for recognizing intracellular UPEC is the imunosurveillance molecule, Toll like Receptor (TLR) 4. We have also identified several key mediators of bacterial exocytosis, which include components of the exocyst complex a Rab GTPase, Rab11 and the SNARE complex. Additionally, we have implicated subcellular microdomains called caveolae in this exocytic process, in the extrusion of bacteria through the plasma membrane. Here we propose to examine how these various signaling components, pathways and subcellular microdomians integrate and achieve bacterial expulsion. We plan to confirm and extend this observation in the following specific aims: (i) Elucidate how intravesicular UPEC are detected by TLR4 in BECs. (ii) Determine how cellular machinery for vesicle trafficking mediates bacterial exocytosis. (iii) Investigate the role of SNARE proteins to docking and discharge of intravesicular UPEC (IV). Identify novel bacterial expulsion components using proteome mining approach.
Recently we discovered that bladder epithelial cells have the innate unique capacity to expel infecting uropathogenic E. coli. We propose to examine how bladder epithelial cells sense intracellular E. coli and mediate bacterial expulsion without loss o cell viability. These studies are directed at an overlooked aspect of the host cell's innate immune response and could potentially lead to the development of novel strategies to combat urinary tract infections.
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