title: Bacterial lysis liberates the neutrophil migration suppressor YbcL from the periplasm of uropathogenic Escherichia coli.
abstract: Uropathogenic Escherichia coli (UPEC) modulates aspects of the innate immune response during urinary tract infection to facilitate bacterial invasion of the bladder epithelium, a requirement for the propagation of infection. For example, UPEC-encoded YbcL suppresses the traversal of bladder epithelia by neutrophils in both an in vitro model and an in vivo murine cystitis model. The suppressive activity of YbcL requires liberation from the bacterial periplasm, though the mechanism of release is undefined. Here we present findings on the site of action of YbcL and demonstrate a novel mode of secretion for a UPEC exoprotein. Suppression of neutrophil migration by purified YbcL(UTI), encoded by cystitis isolate UTI89, required the presence of a uroepithelial layer; YbcL(UTI) did not inhibit neutrophil chemotaxis directly. YbcL(UTI) was released to a greater extent during UPEC infection of uroepithelial cells than during that of neutrophils. Release of YbcL(UTI) was maximal when UPEC and bladder epithelial cells were in close proximity. Established modes of secretion, including outer membrane vesicles, the type II secretion system, and the type IV pilus, were dispensable for YbcL(UTI) release from UPEC. Instead, YbcL(UTI) was liberated during bacterial death, which was augmented upon exposure to bladder epithelial cells, as confirmed by detection of bacterial cytoplasmic proteins and DNA in the supernatant and enumeration of bacteria with compromised membranes. As YbcL(UTI) acts on the uroepithelium to attenuate neutrophil migration, this mode of release may represent a type of altruistic cooperation within a UPEC population during colonization of the urinary tract.
authors.affiliation: Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri, USA.
authors.forename: Megan E
authors.initials: ME
authors.lastname: Lau
authors.affiliation: Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri, USA.
authors.forename: Elizabeth S
authors.initials: ES
authors.lastname: Danka
authors.affiliation: Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri, USA.
authors.forename: Kristin M
authors.initials: KM
authors.lastname: Tiemann
authors.affiliation: Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri, USA Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA dhunstad@wustl.edu.
authors.forename: David A
authors.initials: DA
authors.lastname: Hunstad
mesh_terms: D000328:Adult; D002352:Carrier Proteins / Q000378:metabolism*; D004847:Epithelial Cells / Q000382:microbiology; D029968:Escherichia coli Proteins / Q000378:metabolism*; D006801:Humans; D007154:Immune System Diseases; D007166:Immunosuppressive Agents / Q000378:metabolism*; D007960:Leukocyte Disorders; D009504:Neutrophils / Q000187:drug effects* / Q000502:physiology; D033903:Periplasmic Proteins / Q000378:metabolism; D056689:Uropathogenic Escherichia coli / Q000276:immunology*
chemical_list: D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D007166:Immunosuppressive Agents; D033903:Periplasmic Proteins; C432085:ybcL protein, E coli