title: Activation of Human Toll-like Receptor 4 (TLR4)·Myeloid Differentiation Factor 2 (MD-2) by Hypoacylated Lipopolysaccharide from a Clinical Isolate of Burkholderia cenocepacia.
abstract: Lung infection by Burkholderia species, in particular Burkholderia cenocepacia, accelerates tissue damage and increases post-lung transplant mortality in cystic fibrosis patients. Host-microbe interplay largely depends on interactions between pathogen-specific molecules and innate immune receptors such as Toll-like receptor 4 (TLR4), which recognizes the lipid A moiety of the bacterial lipopolysaccharide (LPS). The human TLR4·myeloid differentiation factor 2 (MD-2) LPS receptor complex is strongly activated by hexa-acylated lipid A and poorly activated by underacylated lipid A. Here, we report that B. cenocepacia LPS strongly activates human TLR4·MD-2 despite its lipid A having only five acyl chains. Furthermore, we show that aminoarabinose residues in lipid A contribute to TLR4-lipid A interactions, and experiments in a mouse model of LPS-induced endotoxic shock confirmed the proinflammatory potential of B. cenocepacia penta-acylated lipid A. Molecular modeling combined with mutagenesis of TLR4-MD-2 interactive surfaces suggests that longer acyl chains and the aminoarabinose residues in the B. cenocepacia lipid A allow exposure of the fifth acyl chain on the surface of MD-2 enabling interactions with TLR4 and its dimerization. Our results provide a molecular model for activation of the human TLR4·MD-2 complex by penta-acylated lipid A explaining the ability of hypoacylated B. cenocepacia LPS to promote proinflammatory responses associated with the severe pathogenicity of this opportunistic bacterium.
authors.affiliation: From the Departments of Chemical Sciences and Department of Biotechnology, National Institute of Chemistry, Ljubljana 1000, Slovenia.
authors.forename: Flaviana
authors.initials: F
authors.lastname: Di Lorenzo
authors.affiliation: Department of Chemistry and Biochemistry, Universidad CEU San Pablo, Boadilla del Monte, Madrid 28668, Spain, Department of Biopharmaceutics and Pharmacodynamics, Medical University of Gdańsk, Gdańsk 80-416, Poland.
authors.forename: Łukasz
authors.initials: Ł
authors.lastname: Kubik
authors.affiliation: Department of Biotechnology, National Institute of Chemistry, Ljubljana 1000, Slovenia, Centre of Excellence NMR - Future Innovation for Sustainable Technologies, Ljubljana 1000, Slovenia.
authors.forename: Alja
authors.initials: A
authors.lastname: Oblak
authors.affiliation: Infection and Cystic Fibrosis Unit, Istituto di Ricovero e Cura a Carattere Scientifico-San Raffaele Scientific Institute, Milan 20132, Italy.
authors.forename: Nicola Ivan
authors.initials: NI
authors.lastname: Lorè
authors.affiliation: Infection and Cystic Fibrosis Unit, Istituto di Ricovero e Cura a Carattere Scientifico-San Raffaele Scientific Institute, Milan 20132, Italy.
authors.forename: Cristina
authors.initials: C
authors.lastname: Cigana
authors.affiliation: From the Departments of Chemical Sciences and.
authors.forename: Rosa
authors.initials: R
authors.lastname: Lanzetta
authors.affiliation: Biology, University of Naples Federico II, Naples 80126, Italy.
authors.forename: Michelangelo
authors.initials: M
authors.lastname: Parrilli
authors.affiliation: Department of Microbiology and Immunology, University of Western Ontario, London N6A 5C1, Canada.
authors.forename: Mohamad A
authors.initials: MA
authors.lastname: Hamad
authors.affiliation: Applied Immunobiology and Transplantation Group, Institute of Cellular Medicine, University of Newcastle, Newcastle NE1 7RU, United Kingdom, and.
authors.forename: Anthony
authors.initials: A
authors.lastname: De Soyza
authors.affiliation: From the Departments of Chemical Sciences and.
authors.forename: Alba
authors.initials: A
authors.lastname: Silipo
authors.affiliation: Department of Biotechnology, National Institute of Chemistry, Ljubljana 1000, Slovenia, Centre of Excellence NMR - Future Innovation for Sustainable Technologies, Ljubljana 1000, Slovenia.
authors.forename: Roman
authors.initials: R
authors.lastname: Jerala
authors.affiliation: Infection and Cystic Fibrosis Unit, Istituto di Ricovero e Cura a Carattere Scientifico-San Raffaele Scientific Institute, Milan 20132, Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Bragonzi
authors.affiliation: Department of Microbiology and Immunology, University of Western Ontario, London N6A 5C1, Canada, Centre for Infection and Immunity, Queen's University Belfast, Belfast BT9 7AE, United Kingdom.
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Valvano
authors.affiliation: Department of Chemistry and Biochemistry, Universidad CEU San Pablo, Boadilla del Monte, Madrid 28668, Spain, smsantamaria@cib.csic.es.
authors.forename: Sonsoles
authors.initials: S
authors.lastname: Martín-Santamaría
authors.affiliation: From the Departments of Chemical Sciences and molinaro@unina.it.
authors.forename: Antonio
authors.initials: A
authors.lastname: Molinaro
mesh_terms: D000215:Acylation; D000818:Animals; D019121:Burkholderia Infections / Q000276:immunology*; D057508:Burkholderia cenocepacia / Q000737:chemistry / Q000276:immunology* / Q000302:isolation & purification; D002460:Cell Line; D057809:HEK293 Cells; D006801:Humans; D007113:Immunity, Innate; D007249:Inflammation / Q000276:immunology / Q000382:microbiology; D015850:Interleukin-6 / Q000276:immunology; D008050:Lipid A / Q000737:chemistry / Q000276:immunology*; D051218:Lymphocyte Antigen 96 / Q000276:immunology*; D008810:Mice, Inbred C57BL; D062105:Molecular Docking Simulation; D051197:Toll-Like Receptor 4 / Q000276:immunology*
chemical_list: D015850:Interleukin-6; C495377:LY96 protein, human; D008050:Lipid A; D051218:Lymphocyte Antigen 96; D051197:Toll-Like Receptor 4
keywords: Burkholderia; Gram-negative bacteria; TLR4/MD-2; cystic fibrosis; innate immunity; lipopolysaccharide (LPS); molecular modeling