title: SipA, SopA, SopB, SopD, and SopE2 contribute to Salmonella enterica serotype typhimurium invasion of epithelial cells.
abstract: The centisome 63 type III secretion system (T3SS-1) encoded by Salmonella pathogenicity island 1 (SPI1) mediates invasion of epithelial cells by Salmonella enterica serotype Typhimurium. Characterization of mutants lacking individual genes has revealed that T3SS-1 secreted proteins (effectors) SopE2 and SopB are required for invasion while the SipA protein accelerates entry into cells. Here we have revisited the question of which T3SS-1 effectors contribute to the invasion of epithelial cells by complementing a strain lacking all of the effector genes that are required to cause diarrhea in a calf (a sipA sopABDE2 mutant). Introduction of either the cloned sipA, the cloned sopB, or the cloned sopE2 gene increased the invasiveness of the sipA sopABDE2 mutant for nonpolarized HT-29 cells. However, a contribution of sopA or sopD to invasion was not apparent when invasion assays were performed with the nonpolarized colon carcinoma cell lines T84 and HT-29. In contrast, introduction of either the sopA, the sopB, the sopD, or the sopE2 gene increased the invasiveness of the sipA sopABDE2 mutant for polarized T84 cells. Furthermore, introduction of a plasmid carrying sipA and sopB increased the invasiveness of the sipA sopABDE2 mutant for polarized T84 cells significantly compared to the introduction of plasmids carrying only sipA or sopB. We conclude that SipA, SopA, SopB, SopD, and SopE2 contribute to S. enterica serotype Typhimurium invasion of epithelial cells in vitro.
authors.affiliation: Department of Medical Microbiology and Immunology, College of Medicine, Texas A&M University System Health Science Center, 407 Reynolds Medical Building, College Station, TX 77843-1114, USA.
authors.forename: Manuela
authors.initials: M
authors.lastname: Raffatellu
authors.forename: R Paul
authors.initials: RP
authors.lastname: Wilson
authors.forename: Daniela
authors.initials: D
authors.lastname: Chessa
authors.forename: Helene
authors.initials: H
authors.lastname: Andrews-Polymenis
authors.forename: Quynh T
authors.initials: QT
authors.lastname: Tran
authors.forename: Sara
authors.initials: S
authors.lastname: Lawhon
authors.forename: Sangeeta
authors.initials: S
authors.lastname: Khare
authors.forename: L Garry
authors.initials: LG
authors.lastname: Adams
authors.forename: Andreas J
authors.initials: AJ
authors.lastname: Bäumler
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000502:physiology*; D002417:Cattle; D016764:Cell Polarity; D004847:Epithelial Cells / Q000382:microbiology; D020662:Guanine Nucleotide Exchange Factors / Q000502:physiology*; D019073:HT29 Cells; D006801:Humans; D008297:Male; D008840:Microfilament Proteins / Q000502:physiology*; D012486:Salmonella typhimurium / Q000472:pathogenicity*; D012703:Serotyping
chemical_list: D001426:Bacterial Proteins; D020662:Guanine Nucleotide Exchange Factors; D008840:Microfilament Proteins; C118287:SipA protein, Salmonella; C116105:SopD protein, Salmonella; C436324:SopE2 protein, Salmonella typhimurium; C060971:SopA protein, Bacteria; C489224:SopB protein, Salmonella