Salmonella entericaserotype Typhimurium MisL is an intestinal colonization factor that binds fibronectin

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Abstract
Summary: MisL is an autotransporter protein encoded bySalmonellapathogenicity island 3 (SPI3). To investigate the role of MisL inSalmonella entericaserotype Typhimurium (S.Typhimurium) pathogenesis, we characterized its function during infection of mice and identified a host receptor for this adhesin. In a mouse model ofS.Typhimurium intestinal persistence, amisLmutant was shed with the faeces in significantly lower numbers than the wild type and was impaired in its ability to colonize the cecum. Previous studies have implicated binding of extracellular matrix proteins as a possible mechanism forS.Typhimurium intestinal persistence. A gluthathione‐S‐transferase (GST) fusion protein to the MisL passenger domain (GST–MisL29‐281) was constructed to investigate binding to extracellular matrix proteins. In a solid‐phase binding assay the purified GST–MisL29‐281fusion protein bound to fibronectin and collagen IV, but not to collagen I. MisL expression was not detected by Western blot inS.Typhimurium grown under standard laboratory conditions. However, when expression of the clonedmisLgene was driven by theEscherichia coliarabinose promoter, MisL could be detected in theS.Typhimurium outer membrane by Western blot and on the bacterial cell surface by flow cytometry. Expression of MisL enabledS.Typhimurium to bind fibronectin to its cell surface, resulting in attachment to fibronectin‐coated glass slides and in increased invasiveness for human epithelial cells derived from colonic carcinoma (T84 cells). These data identify MisL as an extracellular matrix adhesin involved in intestinal colonization.

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