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.

中文翻译：

---

碳水化合物识别域在 CLEC4A 的自我相互作用中的关键作用，以在体外小鼠常规树突细胞中引发 ITIM 介导的抑制功能。

C 型凝集素受体 (CLR)、模式识别受体 (PRR) 在细胞外部分具有特征性碳水化合物识别域 (CRD)，在识别糖基化病原体和自身糖蛋白后介导关键的细胞功能。CLEC4A 是唯一具有细胞内免疫受体酪氨酸抑制基序 (ITIM) 的经典 CLR，它可能转导负信号。然而，CLEC4A 如何发挥细胞抑制作用仍不清楚。在这里，我们报告了 CLEC4A 通过 CRD 的自相互作用是 ITIM 介导的常规树突细胞 (cDC) 抑制功能所必需的。人类 2 型 cDC (cDC2) 和单核细胞显示出比 cDC1 和浆细胞样 DC (pDC) 以及 B 细胞更高的 CLEC4A 表达。CRD 中的N-糖基化位点或 EPS 基序减少了它们的结合。此外，CLEC4A 中 CRD 或 ITIM 中 EPS 基序的缺失几乎完全削弱了其对鼠 cDC 细胞系激活的抑制作用，而NCRD 内的 -糖基化位点对其活化表现出部分抑制作用。另一方面，CLEC4A 的拮抗性单克隆抗体 (mAb) 抑制 CLEC4A 的自我相互作用及其在小鼠转染子中的下游信号传导，在 Toll 样受体的刺激下增强了单核细胞和单核细胞衍生的未成熟 DC 的激活。 TLR)配体。因此，我们的研究结果表明，CRD 在 CLEC4A 的自相互作用中起关键作用，以引发 ITIM 介导的抑制信号以控制 cDCs 的功能。