title: Lipid A 3'-O-deacylation by Salmonella outer membrane enzyme LpxR modulates the ability of lipid A to stimulate Toll-like receptor 4.
abstract: Modification of lipopolysaccharides, including the membrane anchor portion lipid A, is essential for bacterial adaptation to its host. We examined whether lipid A 3'-O-deacylation by Salmonella lipid A deacylase LpxR affected the ability of lipid A to stimulate the Toll-like receptor 4 (TLR4) and MD-2 complex. Unmodified lipid A and 3'-O-deacylated lipid A were purified from Escherichia coli and E. coli expressing recombinant LpxR, respectively. Inactive lipid A species, palmitoylated lipid A and a lipid A biosynthetic precursor lacking the myristate moiety were purified from E. coli expressing recombinant Salmonella lipid A palmitoyltransferase PagP and E. coli mutant defective in lipid A biosynthesis, respectively. Mass spectrometric analysis of the purified lipid A preparations showed a spectra of single lipid A species and gave a single band on thin layer chromatography. An NF-κB-dependent reporter activation assay was used to determine the bioactivity of the lipid A species in a cell line that expressed human TLR4 and MD-2 complex. Deacylated lipid A was less active than unmodified lipid A, suggesting that lipid A 3'-O-deacylation by LpxR is beneficial for bacteria to evade host immune surveillance: On the other hand, deacylated lipid A was more active than palmitoylated lipid A and the lipid A precursor. Taken together, these results indicated that lipid A 3'-O-deacylation by LpxR significantly reduces the bioactivity of lipid A.
authors.affiliation: Faculty of Pharmaceutical Sciences, Doshisha Women's College, Kyotanabe 610-0395, Japan. kkawasak@dwc.doshisha.ac.jp
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Kawasaki
authors.forename: Mai
authors.initials: M
authors.lastname: Teramoto
authors.forename: Rie
authors.initials: R
authors.lastname: Tatsui
authors.forename: Shoko
authors.initials: S
authors.lastname: Amamoto
mesh_terms: D002265:Carboxylic Ester Hydrolases / Q000737:chemistry*; D002460:Cell Line; D006801:Humans; D008050:Lipid A / Q000737:chemistry* / Q000276:immunology*; D051218:Lymphocyte Antigen 96 / Q000276:immunology; D051197:Toll-Like Receptor 4 / Q000819:agonists / Q000276:immunology*
chemical_list: C495377:LY96 protein, human; D008050:Lipid A; D051218:Lymphocyte Antigen 96; D051197:Toll-Like Receptor 4; D002265:Carboxylic Ester Hydrolases; C513984:LpxR protein, Salmonella typhimurium