Salmonella Pathogenicity Island 4 encodes a giant non-fimbrial adhesin and the cognate type 1 secretion system.
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.
Gerlach
Roman G
RG
Institut für Klinische Mikrobiologie, Immunologie und Hygiene, FAU Erlangen-Nürnberg, D-91054 Erlangen, Germany.
Jäckel
Daniela
D
Stecher
Bärbel
B
Wagner
Carolin
C
Lupas
Andrei
A
Hardt
Wolf-Dietrich
WD
Hensel
Michael
M
D018829:Adhesins, Bacterial / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D018938:Caco-2 Cells; D002460:Cell Line; D003092:Colitis / Q000382:microbiology; D044404:Genomic Islands; D006367:HeLa Cells; D006801:Humans; D007413:Intestinal Mucosa / Q000382:microbiology; D008264:Macrophages; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D011817:Rabbits; D012481:Salmonella Infections, Animal / Q000382:microbiology; D012486:Salmonella typhimurium / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D037521:Virulence Factors
D018829:Adhesins, Bacterial; D001426:Bacterial Proteins; D008565:Membrane Proteins; D037521:Virulence Factors