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  • Galectin-9 suppresses B cell receptor signaling and is regulated by I-branching of N-glycans.

Galectin-9 suppresses B cell receptor signaling and is regulated by I-branching of N-glycans.

Nature communications (2018-08-19)
N Giovannone, J Liang, A Antonopoulos, J Geddes Sweeney, S L King, S M Pochebit, N Bhattacharyya, G S Lee, A Dell, H R Widlund, S M Haslam, C J Dimitroff
ABSTRACT

Leukocytes are coated with a layer of heterogeneous carbohydrates (glycans) that modulate immune function, in part by governing specific interactions with glycan-binding proteins (lectins). Although nearly all membrane proteins bear glycans, the identity and function of most of these sugars on leukocytes remain unexplored. Here, we characterize the N-glycan repertoire (N-glycome) of human tonsillar B cells. We observe that naive and memory B cells express an N-glycan repertoire conferring strong binding to the immunoregulatory lectin galectin-9 (Gal-9). Germinal center B cells, by contrast, show sharply diminished binding to Gal-9 due to upregulation of I-branched N-glycans, catalyzed by the β1,6-N-acetylglucosaminyltransferase GCNT2. Functionally, we find that Gal-9 is autologously produced by naive B cells, binds CD45, suppresses calcium signaling via a Lyn-CD22-SHP-1 dependent mechanism, and blunts B cell activation. Thus, our findings suggest Gal-9 intrinsically regulates B cell activation and may differentially modulate BCR signaling at steady state and within germinal centers.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
MISSION® esiRNA, targeting human LGALS9
Sigma-Aldrich
MISSION® esiRNA, targeting human GCNT2
Sigma-Aldrich
3,4-Diaminobenzophenone, 97%