title: Pseudomonas aeruginosa quorum-sensing molecule homoserine lactone modulates inflammatory signaling through PERK and eI-F2α.
abstract: Pseudomonas aeruginosa secrete N-(3-oxododecanoyl)-homoserine lactone (HSL-C12) as a quorum-sensing molecule to regulate bacterial gene expression. Because HSL-C12 is membrane permeant, multiple cell types in P. aeruginosa-infected airways may be exposed to HSL-C12, especially adjacent to biofilms where local (HSL-C12) may be high. Previous reports showed that HSL-C12 causes both pro- and anti-inflammatory effects. To characterize HSL-C12's pro- and anti-inflammatory effects in host cells, we measured protein synthesis, NF-κB activation, and KC (mouse IL-8) and IL-6 mRNA and protein secretion in wild-type mouse embryonic fibroblasts (MEF). To test the role of the endoplasmic reticulum stress inducer, PERK we compared these responses in PERK(-/-) and PERK-corrected PERK(-/-) MEF. During 4-h treatments of wild-type MEF, HSL-C12 potentially activated NF-κB p65 by preventing the resynthesis of IκB and increased transcription of KC and IL-6 genes (quantitative PCR). HSL-C12 also inhibited secretion of KC and/or IL-6 into the media (ELISA) both in control conditions and also during stimulation by TNF-α. HSL-C12 also activated PERK (as shown by increased phosphorylation of eI-F2α) and inhibited protein synthesis (as measured by incorporation of [(35)S]methionine by MEF). Comparisons of PERK(-/-) and PERK-corrected MEF showed that HSL-C12's effects were explained in part by activation of PERK→phosphorylation of eI-F2α→inhibition of protein synthesis→reduced IκBα production→activation of NF-κB→increased transcription of the KC gene but reduced translation and secretion of KC. HSL-C12 may be an important modulator of early (up to 4 h) inflammatory signaling in P. aeruginosa infections.
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Grabiner
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720.
authors.forename: Zhu
authors.initials: Z
authors.lastname: Fu
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720.
authors.forename: Tara
authors.initials: T
authors.lastname: Wu
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720.
authors.forename: Kevin C
authors.initials: KC
authors.lastname: Barry
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720.
authors.forename: Christian
authors.initials: C
authors.lastname: Schwarzer
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720 tmachen@berkeley.edu.
authors.forename: Terry E
authors.initials: TE
authors.lastname: Machen
mesh_terms: D015107:4-Butyrolactone / Q000031:analogs & derivatives* / Q000502:physiology; D000818:Animals; D002460:Cell Line; D059865:Endoplasmic Reticulum Stress / Q000276:immunology; D015852:Eukaryotic Initiation Factor-2 / Q000502:physiology*; D018836:Inflammation Mediators / Q000502:physiology*; D051379:Mice; D011550:Pseudomonas aeruginosa / Q000276:immunology*; D053038:Quorum Sensing / Q000276:immunology*; D015398:Signal Transduction / Q000276:immunology*; D019892:eIF-2 Kinase / Q000172:deficiency / Q000502:physiology*
chemical_list: D015107:4-Butyrolactone; D015852:Eukaryotic Initiation Factor-2; D018836:Inflammation Mediators; D019892:eIF-2 Kinase; C088386:homoserine lactone