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Carbohydrate Dependent Binding of Langerin to SodC, a Cell Wall Glycoprotein of Mycobacterium leprae.

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 2-D Western blot, and by surface plasmon resonance demonstrated 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 (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.

More information

Type
Journal Article
Author
Kim H
Brennan PJ
Heaslip D
Udey M
Modlin RL
Belisle JT

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