Polysaccharide structural variability in mycobacteria: identification and characterization of phosphorylated mannan and arabinomannan

Abstract

Arabinomannan (AMannan) and mannan (Mannan) are major polysaccharides antigens of the mycobacterial capsule. They are highly related to the lipoarabinomannan (LAM) and lipomannan (LM) lipoglycans of the cell wall, known to participate to the immunopathogenesis of mycobacterial infections. Here we present the identification of two related polysaccharides from Mycobacterium kansasii that co-purified with AMannan and Mannan. Structural analysis using GC, MALDI-MS and NMR clearly established these molecules as non-acylated phosphorylated AMannan and Mannan designated P-AMannan and P-Mannan, respectively. These glycoconjugates represent a new source of polysaccharide structural variability in mycobacteria and constitute unique tools for structure-activity relationship studies in order to investigate the role of fatty acids in the biological functions of LAM and LM. The potential participation of these polysaccharides in influencing the outcome of the infection is also discussed.

Identification by surface plasmon resonance of the mycobacterial lipomannan and lipoarabinomannan domains involved in binding to CD14 and LPS‐binding protein

“…Mannan, P-Mannan, AMannan and P-AMannan were extracted from detergent depleted phase of M. kansasii after phase partitioning with Triton X-114 and separated by successive gel chromatographies as already described [31].…”

“…These natural cell wall-associated glycoconjugates only differ from the parental LM and LAM molecules by lacking the fatty acids attached to the MPI anchor, hence their names P-Mannan and P-AMannan (Fig. 1b) [31]. Mannan and AMannan molecules, respectively corresponding to LM and LAM lacking the entire MPI anchors, were also added in our experiments.…”

“…Because these polysaccharides correspond to LAM and LM devoid of MPI anchors, the lack of interactions could be attributed either to the absence of phosphatidylinositol or to the absence of fatty acids bound to the MPI anchor. In order to discriminate between the two possibilities, we analysed the binding properties of P-AMannan and P-Mannan (only differing from LAM and LM by the absence of the two fatty acids of the MPI anchor [31]). As shown in Fig.…”

“…LBP is an acute-phase serum protein which disaggregates and transfers bacterial glycolipids to CD14 [29,30]. CD14 is a glycoprotein which exists in two forms, either bound to the membrane of monocytes/macrophages by a GPI anchor (mCD14) or soluble in plasma (sCD14) [31]. Anti-CD14 antibodies decreased Abbreviations: LM, lipomannan; LAM, lipoarabinomannan; LBP, L-PS-binding protein; MMP, matrix metalloproteinase; LPS, lipopolysaccharide; MPI, mannosyl-phosphatidyl-myo-inositol; TLR, Toll-like receptor; PIM 2 , phosphatidyl-myo-inositol dimannoside; PIM, phosphatidyl-myo-inositol mannoside; DC-SIGN, dendritic cell-specific ICAM-3 grabbing non-integrin; AMannan, arabinomannan; P-AMannan, phosphorylated arabinomannan; Mannan, mannan; P-Mannan, phosphorylated mannan; PRR, pattern recognition receptor; SPR, surface plasmon resonance technology; RU, resonance unit; Requ, equilibrium response values the TLR2-dependent activities of LM and PILAM on macrophages [17,20], whereas a CD14/TLR2 cotransfection or the addition of sCD14 to cells, enhanced the biological responses [25][26][27].…”

Innate immune receptors in development of Mycobacterium tuberculosis infection

“…Другими поверхностными маннозилированными молекулами M. tuberculosis, которые являются потенциальными лигандами для маннозного рецептора, являются арабиноманнаны, маннопротеины, фосфорилированный арабиноманнан и маннан [63]. Микобактериальные поверхностные маннозилированные молекулы играют важную роль в регуляции фагоцитоза и реакции хозяина.…”