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J Bacteriol. 2015 Feb;197(3):615-25. doi: 10.1128/JB.02080-14. Epub 2014 Nov 24.

Carbohydrate-dependent binding of langerin to SodC, a cell wall glycoprotein of Mycobacterium leprae.

Author information

1
Mycobacteria Research Laboratories, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado, USA.
2
Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA.
3
Division of Dermatology and Department of Microbiology, Immunology and Molecular Genetics, David Geffen School of Medicine at the University of California, Los Angeles, California, USA.
4
Mycobacteria Research Laboratories, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado, USA john.belisle@colostate.edu.

Abstract

Langerhans cells participate in the immune response in leprosy by their ability to activate T cells that recognize the pathogen, Mycobacterium leprae, in a langerin-dependent manner. We hypothesized that langerin, the distinguishing C-type lectin of Langerhans cells, would recognize the highly mannosylated structures in pathogenic Mycobacterium spp. The coding region for the extracellular and neck domain of human langerin was cloned and expressed to produce a recombinant active trimeric form of human langerin (r-langerin). Binding assays performed in microtiter plates, by two-dimensional (2D) Western blotting, and by surface plasmon resonance demonstrated that r-langerin possessed carbohydrate-dependent affinity to glycoproteins in the cell wall of M. leprae. This lectin, however, yielded less binding to mannose-capped lipoarabinomannan (ManLAM) and even lower levels of binding to phosphatidylinositol mannosides. However, the superoxide dismutase C (SodC) protein of the M. leprae cell wall was identified as a langerin-reactive ligand. Tandem mass spectrometry verified the glycosylation of a recombinant form of M. leprae SodC (rSodC) produced in Mycobacterium smegmatis. Analysis of r-langerin affinity by surface plasmon resonance revealed a carbohydrate-dependent affinity of rSodC (equilibrium dissociation constant [KD] = 0.862 μM) that was 20-fold greater than for M. leprae ManLAM (KD = 18.69 μM). These data strongly suggest that a subset of the presumptively mannosylated M. leprae glycoproteins act as ligands for langerin and may facilitate the interaction of M. leprae with Langerhans cells.

PMID:
25422308
PMCID:
PMC4285976
DOI:
10.1128/JB.02080-14
[Indexed for MEDLINE]
Free PMC Article

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