Pivotal role of the carbohydrate recognition domain in self-interaction of CLEC4A to elicit the ITIM-mediated inhibitory function in murine conventional dendritic cells in vitro
Pivotal role of the carbohydrate recognition domain in self-interaction of CLEC4A to elicit the ITIM-mediated inhibitory function in murine conventional dendritic cells in vitro
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DOI：
10.1093/intimm/dxaa034
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发表时间：
2020-10-01
影响因子：
4.4
通讯作者：
Sato, Katsuaki
中科院分区：
文献类型：
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作者：
Nasu, Junta;Uto, Tomofumi;Sato, Katsuaki
C型凝集素受体（CLRs）是一种在细胞外部分具有特征性碳水化合物识别结构域（CRD）的模式识别受体（PRRs），在识别糖基化病原体和自身糖蛋白时介导重要的细胞功能。CLEC 4A是唯一一个具有细胞内免疫受体酪氨酸抑制基序（ITIM）的经典的细胞内受体，其可能转导负信号。然而，CLEC 4A如何发挥细胞抑制作用仍不清楚。在这里，我们报告说，CLEC 4A通过CRD的自我相互作用所需的ITIM介导的抑制功能，在传统的树突状细胞（cDC）。人2型cDC（cDC 2）和单核细胞显示出比cDC 1和浆细胞样DC（pDC）以及B细胞更高的CLEC 4A表达。CLEC 4A的细胞外部分特异性结合表达CLEC 4A的鼠cDC细胞系，而其细胞外部分在CRD内缺乏N-糖基化位点或EPS基序降低了它们的结合。此外，CLEC 4A中CRD或ITIM内EPS基序的缺失几乎完全削弱了其对鼠cDC细胞系活化的抑制作用，而CRD内N-糖基化位点的缺失表现出对它们活化的部分抑制。另一方面，CLEC 4A的拮抗性单克隆抗体（mAb）在鼠转染子中抑制CLEC 4A的自身相互作用及其下游信号传导，在用Toll样受体（TLR）配体刺激时增强单核细胞和单核细胞衍生的未成熟DC的活化。我们的发现表明CRD在CLEC 4A的自身相互作用中起关键作用，以引发ITIM介导的抑制信号来控制cDC的功能。
C-type lectin receptors (CLRs), pattern recognition receptors (PRRs) with a characteristic carbohydrate recognition domain (CRD) in the extracellular portion, mediate crucial cellular functions upon recognition of glycosylated pathogens and self-glycoproteins. CLEC4A is the only classical CLR that possesses an intracellular immunoreceptor tyrosine-based inhibitory motif (ITIM), which possibly transduces negative signals. However, how CLEC4A exerts cellular inhibition remains unclear. Here, we report that the self-interaction of CLEC4A through the CRD is required for the ITIM-mediated suppressive function in conventional dendritic cells (cDCs). Human type 2 cDCs (cDC2) and monocytes display a higher expression of CLEC4A than cDC1 and plasmacytoid DCs (pDCs) as well as B cells. The extracellular portion of CLEC4A specifically binds to a murine cDC cell line expressing CLEC4A, while its extracellular portion lacking the N-glycosylation site or the EPS motif within the CRD reduces their association. Furthermore, the deletion of the EPS motif within the CRD or ITIM in CLEC4A almost completely impairs its suppressive effect on the activation of the murine cDC cell line, whereas the absence of the N-glycosylation site within the CRD exhibits partial inhibition on their activation. On the other hand, antagonistic monoclonal antibody (mAb) to CLEC4A, which inhibits the self-interaction of CLEC4A and its downstream signaling in murine transfectants, enhances the activation of monocytes and monocyte-derived immature DCs upon stimulation with a Toll-like receptor (TLR) ligand.Thus, our findings suggest a pivotal role of the CRD in self-interaction of CLEC4A to elicit the ITIM-mediated inhibitory signal for the control of the function of cDCs.