Miyake Yasunobu, Masatsugu Oh-hora, Yamasaki Sho
Division of Molecular Immunology, Medical Institute of Bioregulation, Kyushu University, Fukuoka 812-8582, Japan; and.
Division of Molecular Immunology, Medical Institute of Bioregulation, Kyushu University, Fukuoka 812-8582, Japan; and Division of Molecular Immunology, Medical Mycology Research Center, Chiba University, Chiba 260-8673, Japan
J Immunol. 2015 Jun 1;194(11):5366-74. doi: 10.4049/jimmunol.1402429. Epub 2015 Apr 17.
C-type lectin receptors expressed in APCs are recently defined pattern recognition receptors that play a crucial role in immune responses against pathogen-associated molecular patterns. Among pathogen-associated molecular patterns, cord factor (trehalose-6,6'-dimycolate [TDM]) is the most potent immunostimulatory component of the mycobacterial cell wall. Two C-type lectin receptors, macrophage-inducible C-type lectin (Mincle) and macrophage C-type lectin (MCL), are required for immune responses against TDM. Previous studies indicate that MCL is required for TDM-induced Mincle expression. However, the mechanism by which MCL induces Mincle expression has not been fully understood. In this study, we demonstrate that MCL interacts with Mincle to promote its surface expression. After LPS or zymosan stimulation, MCL-deficient bone marrow-derived dendritic cells (BMDCs) had a lower level of Mincle protein expression, although mRNA expression was comparable with wild-type BMDCs. Meanwhile, BMDCs from MCL transgenic mice showed an enhanced level of Mincle expression on the cell surface. MCL was associated with Mincle through the stalk region and this region was necessary and sufficient for the enhancement of Mincle expression. This interaction appeared to be mediated by the hydrophobic repeat of MCL, as substitution of four hydrophobic residues within the stalk region with serine (MCL(4S)) abolished the function to enhance the surface expression of Mincle. MCL(4S) mutant failed to restore the defective TDM responses in MCL-deficient BMDCs. These results suggest that MCL positively regulates Mincle expression through protein-protein interaction via its stalk region, thereby magnifying Mincle-mediated signaling.
在抗原呈递细胞（APCs）中表达的C型凝集素受体是最近定义的模式识别受体，在针对病原体相关分子模式的免疫反应中起关键作用。在病原体相关分子模式中，索状因子（海藻糖-6,6'-二霉菌酸酯[TDM]）是分枝杆菌细胞壁中最有效的免疫刺激成分。针对TDM的免疫反应需要两种C型凝集素受体，即巨噬细胞诱导型C型凝集素（Mincle）和巨噬细胞C型凝集素（MCL）。先前的研究表明，MCL是TDM诱导的Mincle表达所必需的。然而，MCL诱导Mincle表达的机制尚未完全了解。在本研究中，我们证明MCL与Mincle相互作用以促进其表面表达。在脂多糖（LPS）或酵母聚糖刺激后，MCL缺陷的骨髓来源的树突状细胞（BMDCs）的Mincle蛋白表达水平较低，尽管mRNA表达与野生型BMDCs相当。同时，来自MCL转基因小鼠的BMDCs在细胞表面显示出增强的Mincle表达水平。MCL通过柄区与Mincle相关联，该区域对于增强Mincle表达是必要且充分的。这种相互作用似乎是由MCL的疏水重复序列介导的，因为用丝氨酸替代柄区内的四个疏水残基（MCL(4S)）消除了增强Mincle表面表达的功能。MCL(4S)突变体未能恢复MCL缺陷的BMDCs中缺陷的TDM反应。这些结果表明，MCL通过其柄区通过蛋白质-蛋白质相互作用正向调节Mincle表达，从而放大Mincle介导的信号传导。
