title: Deciphering the acylation pattern of Yersinia enterocolitica lipid A.
abstract: Pathogenic bacteria may modify their surface to evade the host innate immune response. Yersinia enterocolitica modulates its lipopolysaccharide (LPS) lipid A structure, and the key regulatory signal is temperature. At 21°C, lipid A is hexa-acylated and may be modified with aminoarabinose or palmitate. At 37°C, Y. enterocolitica expresses a tetra-acylated lipid A consistent with the 3'-O-deacylation of the molecule. In this work, by combining genetic and mass spectrometric analysis, we establish that Y. enterocolitica encodes a lipid A deacylase, LpxR, responsible for the lipid A structure observed at 37°C. Western blot analyses indicate that LpxR exhibits latency at 21°C, deacylation of lipid A is not observed despite the expression of LpxR in the membrane. Aminoarabinose-modified lipid A is involved in the latency. 3-D modelling, docking and site-directed mutagenesis experiments showed that LpxR D31 reduces the active site cavity volume so that aminoarabinose containing Kdo(2)-lipid A cannot be accommodated and, therefore, not deacylated. Our data revealed that the expression of lpxR is negatively controlled by RovA and PhoPQ which are necessary for the lipid A modification with aminoarabinose. Next, we investigated the role of lipid A structural plasticity conferred by LpxR on the expression/function of Y. enterocolitica virulence factors. We present evidence that motility and invasion of eukaryotic cells were reduced in the lpxR mutant grown at 21°C. Mechanistically, our data revealed that the expressions of flhDC and rovA, regulators controlling the flagellar regulon and invasin respectively, were down-regulated in the mutant. In contrast, the levels of the virulence plasmid (pYV)-encoded virulence factors Yops and YadA were not affected in the lpxR mutant. Finally, we establish that the low inflammatory response associated to Y. enterocolitica infections is the sum of the anti-inflammatory action exerted by pYV-encoded YopP and the reduced activation of the LPS receptor by a LpxR-dependent deacylated LPS.
authors.affiliation: Laboratory Microbial Pathogenesis, Fundació d'Investigació Sanitària de les Illes Balears, Recinto Hospital Joan March, Bunyola, Spain.
authors.forename: Mar
authors.initials: M
authors.lastname: Reinés
authors.forename: Enrique
authors.initials: E
authors.lastname: Llobet
authors.forename: Käthe M
authors.initials: KM
authors.lastname: Dahlström
authors.forename: Camino
authors.initials: C
authors.lastname: Pérez-Gutiérrez
authors.forename: Catalina M
authors.initials: CM
authors.lastname: Llompart
authors.forename: Nuria
authors.initials: N
authors.lastname: Torrecabota
authors.forename: Tiina A
authors.initials: TA
authors.lastname: Salminen
authors.forename: José A
authors.initials: JA
authors.lastname: Bengoechea
mesh_terms: D000215:Acylation; D018829:Adhesins, Bacterial / Q000096:biosynthesis; D000818:Animals; D001089:Arabinose / Q000031:analogs & derivatives; D001426:Bacterial Proteins / Q000378:metabolism; D002265:Carboxylic Ester Hydrolases / Q000235:genetics* / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D006367:HeLa Cells; D006801:Humans; D008050:Lipid A / Q000737:chemistry* / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000737:chemistry / Q000378:metabolism; D008264:Macrophages / Q000378:metabolism; D051379:Mice; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010169:Palmitic Acids; D013696:Temperature; D014157:Transcription Factors / Q000378:metabolism; D037521:Virulence Factors / Q000378:metabolism; D015009:Yersinia Infections / Q000235:genetics / Q000276:immunology / Q000382:microbiology; D015008:Yersinia enterocolitica / Q000235:genetics / Q000276:immunology / Q000378:metabolism* / Q000472:pathogenicity*
chemical_list: D018829:Adhesins, Bacterial; D001426:Bacterial Proteins; D008050:Lipid A; D008070:Lipopolysaccharides; D010169:Palmitic Acids; C079792:PhoQ protein, Bacteria; C405626:RovA protein, Yersinia; D014157:Transcription Factors; D037521:Virulence Factors; C064832:YadA protein, Yersinia; C016982:aminoarabinose; C052253:deacylated lipopolysaccharides; D001089:Arabinose; D002265:Carboxylic Ester Hydrolases