Association of C-Type Lectin Mincle with Fc\u03b5RI\u03b2\u03b3 Subunits Leads to Functional Activation of RBL-2H3 Cells through Syk

Chisato Honjoh,Hatsumi Yoshiki,Shota Yamauchi,Kazuyasu Chihara,Yukio Hida,Kiyonao Sada,Yuji Kato,Tamotsu Ishizuka,Kenji Takeuchi

doi:10.1038/srep46064

Chisato Honjoh, Hatsumi Yoshiki + Show 7 more

Open Access

https://doi.org/10.1038/srep46064

Copy DOI

Abstract

Macrophage-inducible C-type lectin (Mincle) interacts with the γ-subunit of high-affinity IgE receptor (FcεRIγ) and activates Syk by recognizing its specific ligand, trehalose-6,6′-dimycolate, a glycolipid produced by Mycobacterium tuberculosis. It has been suggested that mast cells participate in the immune defense against pathogenic microbes including M. tuberculosis, although the functions are still uncertain. In this study, we examined the Mincle-mediated signaling pathway and cellular responses using RBL-2H3 cells. Mincle formed a protein complex with not only FcεRIγ but also FcεRIβ in a stable cell line expressing myc-tagged Mincle. In addition, engagement of Mincle increased the levels of protein tyrosine phosphorylation and ERK phosphorylation. A pull-down assay demonstrated that cross-linking of Mincle induced binding of FcεRIβγ subunits to the Src homology 2 domain of Syk. Pharmacological and genetic studies indicated that activation of Syk was critical for Mincle-mediated activation of phospholipase Cγ2, leading to the activation of ERK and nuclear factor of activated T cells. Moreover, engagement of Mincle efficiently induced up-regulation of characteristic mast cell genes in addition to degranulation. Taken together, our present results suggest that mast cells contribute to Mincle-mediated immunity through Syk activation triggered by association with the FcεRIβγ complex.

Highlights

Mast cells are known to play important roles in the initiation of allergic reactions
Because it is possible that the mechanism of receptor-mediated activation of cellular signaling is different between Dectin-1 and Macrophage-inducible C-type lectin (Mincle), we investigated the functions of Mincle in RBL-2H3 cells
Molecular size markers are indicated at the left in kDa. (b) Cells expressing wild type (WT) Mincle (WT), Syk-deficient cells (Syk KO), and PLCγ2-deficient cells (PLCγ2 KO) were transiently transfected with luciferase reporter plasmids

Summary

Introduction

Mast cells are known to play important roles in the initiation of allergic reactions. In addition to IgE-dependent allergic reactions, it has been suggested that mast cells are involved in innate immunity to pathogens[5,6]. Pattern recognition receptors, such as Toll-like receptors (TLRs) and some C-type lectin receptors (CLRs), act as sensors for invading microbes[7,8]. In addition to TLRs, expression of Dectin-1, a member of the CLRs, has been shown in mast cells, which enhances the production of leukotrienes and reactive oxygen species in response to stimulation by fungal cell wall zymosan[12,13]. Mincle expression is maintained at a relatively low level in unstimulated macrophages, it is dramatically up-regulated in response to LPS, TNF-α, IL-6, and IFN-γ23

Methods

Results

Conclusion