title: Salmonella enterica serovar Typhimurium-induced internalization and IL-8 expression in HeLa cells does not have a direct relationship with intracellular Ca(2+) levels.
abstract: The invasion-associated type III secretion system (T3SS-1) of S. Typhimurium is required to initiate and sustain an acute inflammatory response in the intestine. We investigated the relationship of S. Typhimurium T3SS-1-induced IL-8 expression and invasion with intracellular Ca(2+) mobilization in HeLa cells. Compared to the sipAsopABDE2 mutant, strains carrying a mutation in sipA, or mutations in sopABDE2 induced higher levels of IL-8 and greater bacterial internalization despite the fact that these mutants elicited similarly low intracellular concentrations of Ca(2+). Likewise, complemented sipAsopABDE2 mutant with sopE2 did not affect intracellular Ca(2+) concentrations or IL-8 expression, but significantly increased bacterial internalization. Treating HeLa cells with the calcium chelator BAPTA-AM or with D-BAPTA-AM, a derivative with greatly reduced Ca(2+) chelating activity, yielded strong evidence that BAPTA-AM does not affect invasion and inhibits IL-8 secretion by a calcium-dependent mechanism. These findings suggest that, although wild-type S. Typhimurium-induced IL-8 expression and bacterial internalization in HeLa cells coincides with increased cytosolic Ca(2+), the differing levels of IL-8 and invasion induced by strains carrying different effector proteins are unrelated to levels of intracellular Ca(2+).
authors.affiliation: Department of Veterinary Pathobiology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX 77843-4467, USA.
authors.forename: Josely F
authors.initials: JF
authors.lastname: Figueiredo
authors.forename: Rola
authors.initials: R
authors.lastname: Barhoumi
authors.forename: Manuela
authors.initials: M
authors.lastname: Raffatellu
authors.forename: Sara D
authors.initials: SD
authors.lastname: Lawhon
authors.forename: Bernard
authors.initials: B
authors.lastname: Rousseau
authors.forename: Robert C
authors.initials: RC
authors.lastname: Burghardt
authors.forename: Renée M
authors.initials: RM
authors.lastname: Tsolis
authors.forename: Andreas J
authors.initials: AJ
authors.lastname: Bäumler
authors.forename: L Garry
authors.initials: LG
authors.lastname: Adams
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics; D002118:Calcium / Q000032:analysis*; D015169:Colony Count, Microbial; D003593:Cytoplasm / Q000737:chemistry* / Q000382:microbiology*; D017353:Gene Deletion; D005816:Genetic Complementation Test; D006367:HeLa Cells; D006801:Humans; D016209:Interleukin-8 / Q000096:biosynthesis*; D008840:Microfilament Proteins / Q000235:genetics; D012486:Salmonella typhimurium / Q000472:pathogenicity*
chemical_list: D001426:Bacterial Proteins; D016209:Interleukin-8; D008840:Microfilament Proteins; C118287:SipA protein, Salmonella; C103987:SopE protein, Salmonella; D002118:Calcium