N-glycan branching inhibits pro-inflammatory B cell activity by controlling TLR4 and BCR signaling.

Abstract

Abstract N-glycosylation is a critical regulator of T cell function. The branching and number of N-glycans on cell surface glycoproteins drive binding to galectins, forming a galectin-glycoprotein lattice that controls T cell growth, differentiation and development by regulating receptor clustering, distribution and endocytosis. N-glycan branching is ~1.5–2 fold higher in B cells compared to T cells, yet effects on B cell function are unknown. Here we report that branching regulates pro-inflammatory signaling via Toll Like Receptor – 4 (TLR4) and the B cell receptor (BCR). Mechanisms controlling pro-inflammatory (cell surface) versus anti-inflammatory (endosomal) TLR4 signaling in B cells is poorly understood. Loss of branching in B cells de-couples LPS induced proliferative from pro-inflammatory responses by inhibiting TLR4 endocytosis. Similar de-coupling is observed with BCR signaling, where loss of branching inhibits BCR driven proliferation and Lyn/Syk/PLCγ2/Ca2+ signaling via reduced CD19 surface expression while concurrently driving pro-inflammatory effector functions and PI3K/Akt/mTOR activation. Together, these data reveal N-glycan branching as a critical negative regulator of TLR4 and BCR triggered pro-inflammatory B cell responses.