Mycobacterium marinum lipooligosaccharides are unique caryophyllose-containing cell wall glycolipids that inhibit tumor necrosis factor-alpha secretion in macrophages.
Earlier studies have reported a role for lipooligosaccharides (LOSs) in sliding motility, biofilm formation, and infection of host macrophages in Mycobacterium marinum. Although a LOS biosynthetic gene cluster has recently been identified in this species, many structural features of the different LOSs (LOS-I-IV) are still unknown. This clearly hampers assessing the contribution of each LOS in mycobacterial virulence as well as structure-function-based studies of these important cell wall-associated glycolipids. In this study, we have identified an M. marinum isolate, M. marinum 7 (Mma7), which failed to produce LOS-IV but instead accumulated large amounts of LOS-III. Local genomic comparison of the LOS biosynthetic cluster established the presence of a highly disorganized region in Mma7 compared with the standard M strain, characterized by multiple genetic lesions that are likely to be responsible for the defect in LOS-IV production in Mma7. Our results indicate that the glycosyltransferase LosA alone is not sufficient to ensure LOS-IV biosynthesis. The availability of different M. marinum strains allowed us to determine the precise structure of individual LOSs through the combination of mass spectrometric and NMR techniques. In particular, we established the presence of two related 4-C-branched monosaccharides within LOS-II to IV sequences, of which one was never identified before. In addition, we provided evidence that LOSs are capable of inhibiting the secretion of tumor necrosis factor-alpha in lipopolysaccharide-stimulated human macrophages. This unexpected finding suggests that these cell wall-associated glycolipids represent key effectors capable of interfering with the establishment of a pro-inflammatory response.
Rombouts
Yoann
Y
Unité de Glycobiologie Structurale et Fonctionnelle, CNRS UMR 8576, IFR 147, Université des Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq Cedex, France.
Burguière
Adeline
A
Maes
Emmanuel
E
Coddeville
Bernadette
B
Elass
Elisabeth
E
Guérardel
Yann
Y
Kremer
Laurent
L
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000032:analysis / Q000737:chemistry / Q000235:genetics; D002236:Carbohydrate Conformation; D002241:Carbohydrates / Q000032:analysis / Q000737:chemistry*; D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D002473:Cell Wall / Q000187:drug effects / Q000378:metabolism*; D002855:Chromatography, Thin Layer; D016680:Genome, Bacterial / Q000235:genetics; D006017:Glycolipids / Q000378:metabolism*; D006801:Humans; D008070:Lipopolysaccharides / Q000096:biosynthesis / Q000737:chemistry / Q000494:pharmacology*; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D009005:Monosaccharides / Q000032:analysis / Q000737:chemistry*; D005810:Multigene Family; D019910:Mycobacterium marinum / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D017421:Sequence Analysis; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
D001426:Bacterial Proteins; D002241:Carbohydrates; D006017:Glycolipids; D008070:Lipopolysaccharides; D009005:Monosaccharides; D014409:Tumor Necrosis Factor-alpha; C023023:lipid-linked oligosaccharides