Intracellular metabolite β-glucosylceramide is an endogenous Mincle ligand possessing immunostimulatory activity

Abstract

Sensing and reacting to tissue damage is a fundamental function of immune systems. Macrophage inducible C-type lectin (Mincle) is an activating C-type lectin receptor that senses damaged cells. Notably, Mincle also recognizes glycolipid ligands on pathogens. To elucidate endogenous glycolipids ligands derived from damaged cells, we fractionated supernatants from damaged cells and identified a lipophilic component that activates reporter cells expressing Mincle. Mass spectrometry and NMR spectroscopy identified the component structure as β-glucosylceramide (GlcCer), which is a ubiquitous intracellular metabolite. Synthetic β-GlcCer activated myeloid cells and induced production of inflammatory cytokines; this production was abrogated in Mincle-deficient cells. Sterile inflammation induced by excessive cell death in the thymus was exacerbated by hematopoietic-specific deletion of degrading enzyme of β-GlcCer (β-glucosylceramidase, GBA1). However, this enhanced inflammation was ameliorated in a Mincle-deficient background. GBA1-deficient dendritic cells (DCs) in which β-GlcCer accumulates triggered antigen-specific T-cell responses more efficiently than WT DCs, whereas these responses were compromised in DCs from GBA1 × Mincle double-deficient mice. These results suggest that β-GlcCer is an endogenous ligand for Mincle and possesses immunostimulatory activity.

Glucocerebrosidase: Functions in and Beyond the Lysosome

“…The topic was recently reviewed [34]. Glycosphingolipid-enriched lipid rafts essentially contribute to immunological functions as, for example, activation of T cells [35][36][37][38].…”

The regulatory roles of glycosphingolipid‐enriched lipid rafts in immune systems

“…α‐Linked glycosylceramides were determined to be the main endogenous ligands on NKT cells . Macrophage inducible C‐type lectin (Mincle) responds to β‐GlcCer, which is an endogenous ligand and possess immunostimulatory activity . These findings suggest that GSL‐mediated NKT activation is a potential target for immunotherapy of several disorders.…”

“…α‐Linked glycosylceramides were identified as the major endogenous ligands of NKT cells , which control innate and adaptive immune responses. In addition, β‐GlcCer was identified as an endogenous ligand for Mincle , suggesting that GSL‐receptor trans‐interactions may regulate immune responses. GSLs may play important roles in tuning the cross talk of signaling pathways in immune systems, by regulating their expression and release.…”

C-Type Lectin-Like Receptors: Head or Tail in Cell Death Immunity

“…MINCLE was also shown to play a specific role on plasmacytoid DCs in skin allergies by recognizing cholesterol sulfate and inducing secretion of pro-inflammatory mediators such as IL-1α, IL-1β, MIP-1α, and MIP-1β (82). Furthermore, β-GlcCer whose accumulation leads to the systemic inflammation of Gaucher disease, was also characterized as a ligand for MINCLE, able to potentiate acquired immune response (90). Thus, MINCLE, via its high expression on M1-type macrophages and its ability to sense dead cells was also shown to be an important mediator of additional inflammatory diseases such as obesity and acute kidney injury (77,78,99,100).…”