Salmonella Pathogenicity Island 4 encodes a giant non-fimbrial adhesin and the cognate type 1 secretion system
Article first published online: 26 FEB 2007
Volume 9, Issue 7, pages 1834–1850, July 2007
How to Cite
Gerlach, R. G., Jäckel, D., Stecher, B., Wagner, C., Lupas, A., Hardt, W.-D. and Hensel, M. (2007), Salmonella Pathogenicity Island 4 encodes a giant non-fimbrial adhesin and the cognate type 1 secretion system. Cellular Microbiology, 9: 1834–1850. doi: 10.1111/j.1462-5822.2007.00919.x
- Issue published online: 26 FEB 2007
- Article first published online: 26 FEB 2007
- Received 24 November, 2006; revised 19 January, 2007; accepted 22 January, 2007.
Pathogenicity Islands play a major role in the pathogenesis of infections by Salmonella enterica. The molecular function of Salmonella Pathogenicity Island 4 (SPI4) is largely unknown, but recent work indicated a role of SPI4 for Salmonella pathogenesis in certain animal models. We analysed the virulence functions of SPI4 and observed that SPI4 is contributing to intestinal inflammation in a mouse model. On a cellular level, SPI4 mediates adhesion to epithelial cells. We demonstrate the function of SPI4-encoded proteins as a type I secretion system (T1SS) and identify SiiE as the substrate protein of the T1SS. SiiE is secreted into the culture medium but mediates contact-dependent adhesion to epithelial cell surfaces. SiiE is a very large non-fimbrial adhesin of 600 kDa and consists of 53 repeats of Ig domains. Our study describes the first T1SS-secreted protein that functions as a non-fimbrial adhesin in binding to eukaryotic cells. The SPI4-encoded T1SS and SiiE might functionally resemble the type I fimbrial adhesins.