title: A lipomannan variant with strong TLR-2-dependent pro-inflammatory activity in Saccharothrix aerocolonigenes.
abstract: Lipomannans (LMs) are powerful pro-inflammatory lipoglycans found in mycobacteria and related genera, however the molecular bases of their activity are not fully understood. We report here the isolation and the structural and functional characterization of a new lipomannan variant present in the Pseudonocardineae, Saccharothrix aerocolonigenes, designated SaeLM. Using a range of chemical degradations, NMR experiments, and mass spectrometry analyses, SaeLM revealed a mannosylphosphatidyl-myo-inositol (MPI) anchor glycosylated by an original carbohydrate structure whereby an (alpha1-->6)-Manp backbone is substituted at >80% of the O-2 position by side chains composed of Manp-(alpha1-->2)-Manp-(alpha1-->. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry analysis indicated a distribution of SaeLM glyco-forms ranging from 19 to 61 Manp units, which centered on species containing 37 or 40 Manp units. SaeLM induced a Toll-like receptor 2 (TLR-2)-dependent production of tumor necrosis factor-alpha (TNF-alpha) by human THP-1 monocyte/macrophage cell lines and interestingly was found to be the strongest inducer of this pro-inflammatory cytokine when compared with other LAM/LM-like molecules. We previously established that a linear (alpha1-->6)-Manp chain, linked to the MPI anchor, is sufficient in providing pro-inflammatory activity. We demonstrate here that by adding side chains and increasing their size, one may potentiate this activity. These findings should enable a better understanding of the structure/function relationships of TLR-2-dependent lipoglycan signaling.
authors.affiliation: School of Bioscience, The University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom.
authors.forename: Kevin J C
authors.initials: KJ
authors.lastname: Gibson
authors.forename: Martine
authors.initials: M
authors.lastname: Gilleron
authors.forename: Patricia
authors.initials: P
authors.lastname: Constant
authors.forename: Bénédicte
authors.initials: B
authors.lastname: Sichi
authors.forename: Germain
authors.initials: G
authors.lastname: Puzo
authors.forename: Gurdyal S
authors.initials: GS
authors.lastname: Besra
authors.forename: Jérôme
authors.initials: J
authors.lastname: Nigou
mesh_terms: D000192:Actinomycetales / Q000235:genetics* / Q000472:pathogenicity*; D002460:Cell Line; D014644:Genetic Variation; D006801:Humans; D007249:Inflammation; D008070:Lipopolysaccharides / Q000737:chemistry*; D008264:Macrophages / Q000502:physiology; D009682:Magnetic Resonance Spectroscopy; D008562:Membrane Glycoproteins / Q000502:physiology*; D009000:Monocytes / Q000502:physiology; D011956:Receptors, Cell Surface / Q000502:physiology*; D051195:Toll-Like Receptor 2; D051193:Toll-Like Receptors; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis
chemical_list: D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D011956:Receptors, Cell Surface; C495342:TLR2 protein, human; D051195:Toll-Like Receptor 2; D051193:Toll-Like Receptors; D014409:Tumor Necrosis Factor-alpha; C064351:lipomannan