α-Hemolysin promotes uropathogenic E. coli persistence in bladder epithelial cells via abrogating bacteria-harboring lysosome acidification

There is a growing consensus that a significant proportion of recurrent urinary tract infections are linked to the persistence of uropathogens within the urinary tract and their re-emergence upon the conclusion of antibiotic treatment. Studies in mice and human have revealed that uropathogenic Escherichia coli (UPEC) can persist in bladder epithelial cells (BECs) even after the apparent resolution of the infection. Here, we found that, following the entry of UPEC into RAB27b+ fusiform vesicles in BECs, some bacteria escaped into the cytoplasmic compartment via a mechanism involving hemolysin A (HlyA). However, these UPEC were immediately recaptured within LC3A/B+ autophagosomes that matured into LAMP1+ autolysosomes. Thereafter, HlyA+ UPEC-containing lysosomes failed to acidify, which is an essential step for bacterial elimination. This lack of acidification was related to the inability of bacteria-harboring compartments to recruit V-ATPase proton pumps, which was attributed to the defragmentation of cytosolic microtubules by HlyA. The persistence of UPEC within LAMP1+ compartments in BECs appears to be directly linked to HlyA. Thus, through intravesicular instillation of microtubule stabilizer, this host defense response can be co-opted to reduce intracellular bacterial burden following UTIs in the bladder potentially preventing recurrence.Author summary: Many strains of uropathogenic E.coli are capable of secreting the soluble toxin α-hemolysin (HlyA). Intracellular UPEC persistence within bladder epithelial cells is highly correlated with their ability to express HlyA. HlyA disrupted cytosolic microtubules, which are required for the recruitment of V-ATPase proton pumps to LAMP1+ vesicles. Therefore, the majority of LAMP1+ vesicles carrying UPEC in host cells were unable to be acidified, which is a critical step for killing bacteria. Since HlyA-mediated microtubule fragmentation is essential for UPEC persistence in the bladder, treatment with paclitaxel (a microtubule stabilizer) in the bladders of UPEC-infected mice significantly reduced the bladder bacterial burden even in the absence of antibiotic treatment.