title: 3-O-deacylation of lipid A by PagL, a PhoP/PhoQ-regulated deacylase of Salmonella typhimurium, modulates signaling through Toll-like receptor 4.
abstract: Toll-like receptor 4 (TLR4)-mediated responses, which are induced by the lipid A portion of lipopolysaccharide, are important for host defense against Salmonellae infection. A variety of different data indicate that the acylation state of lipid A can alter TLR4-mediated responses. The S. typhimurium virulence gene product PhoP/PhoQ signals the presence of host microenvironments to regulate the expression of a lipid A 3-O-deacylase, PagL, and a lipid A palmitoyltransferase, PagP. We now demonstrate that 3-O-deacylation and palmitoylation of lipid A decreases its ability to induce TLR4-mediated signaling. Deacylated lipid A, deacylated and palmitoylated lipid A, palmitoylated lipid A, and unmodified lipid A species were purified from Escherichia coli heterologously expressing PagL and/or PagP. The purified lipid A preparations showed spectra of a single lipid A species on mass spectrometry and gave a single band on thin layer chromatography. The activity of purified lipid A species was examined using human and mouse cell lines that express recombinant human TLR4. Compared with unmodified lipid A, the modified lipid A species are 30-100-fold less active in the ability to induce NF-kappaB-dependent reporter activation. These results suggest that the lipid A modifications reduce TLR4-signaling as part of Salmonellae adaptation to host environments.
authors.affiliation: Department of Microbiology, University of Washington, Seattle, WA 98195, USA.
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Kawasaki
authors.forename: Robert K
authors.initials: RK
authors.lastname: Ernst
authors.forename: Samuel I
authors.initials: SI
authors.lastname: Miller
mesh_terms: D000217:Acyltransferases / Q000502:physiology; D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry / Q000502:physiology*; D002265:Carboxylic Ester Hydrolases / Q000737:chemistry / Q000502:physiology*; D002855:Chromatography, Thin Layer; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000502:physiology; D006801:Humans; D008050:Lipid A / Q000737:chemistry*; D013058:Mass Spectrometry; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000502:physiology*; D051379:Mice; D008956:Models, Chemical; D016328:NF-kappa B / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000502:physiology*; D011994:Recombinant Proteins / Q000737:chemistry; D015398:Signal Transduction; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D008050:Lipid A; D008562:Membrane Glycoproteins; D016328:NF-kappa B; D011956:Receptors, Cell Surface; D011994:Recombinant Proteins; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D000217:Acyltransferases; C468520:PagP protein, E coli; D002265:Carboxylic Ester Hydrolases; C424702:PagL protein, Salmonella typhimurium