Beyond the Crystal Structure of Human Macrophage C-Type Lectin.
Beyond the Crystal Structure of Human Macrophage C-Type Lectin.
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超越人类巨噬细胞 C 型凝集素的晶体结构。
DOI：
10.1021/acs.biochem.3c00642
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发表时间：
2024
期刊：
影响因子：
2.9
通讯作者：
Birrane,Gabriel
中科院分区：
文献类型：
--
作者：
Gabba,Adele;Murphy,PaulV;Kiessling,LauraL;Birrane,Gabriel
巨噬细胞半乳糖型凝集素(MGL，CLEC10A)是已知的唯一与N-乙酰半乳糖胺(GalNAc)优先结合的APC受体(KD>；100μM，单价GalNAc)。虽然GalNAc很少在健康的人类细胞中发现，但它在许多病原体和肿瘤细胞的表面都有大量的存在。MGL识别GalNAc的能力使这种凝集素成为免疫调节治疗的一个特别有趣的靶点；然而，需要全面了解MGL在APC上的功能。MGL是一种跨膜受体：细胞内的信号域包含细胞内的YENF基序，而细胞外的结构域则呈现一个卷曲(CC)区域，该区域将三个结构不同的碳水化合物识别结构域(CRD)结合在一起(图1A)。每个CRD都有一个标志性的QPD基序，介导钙依赖与GalNAc的结合。研究表明，MGL具有双重作用，其抑制或激活免疫系统依赖于抗原的结构和结合的凝集素的构象。蛋白质核磁共振研究表明，MGL CRD具有显著的柔韧性，当与来自Forssman抗原、A血型抗原和GM2糖脂的含GalNAc分子结合时，其构象会发生不同的变化。1尽管有这些数据，但抗原的化学结构与MGL信号之间的关系仍未得到研究。我们推测，合理设计配体以激活或抑制MGL信号将受益于关于MGL CRD及其与GalNAc衍生物的结合的结构信息。我们用X射线结晶学确定了MGL CRD在未结合状态(PDBID 6PUV)以及与GalNAc衍生物(PDBID 6XIY，6PY1)，包括癌症相关的TN-Ser抗原(PDBID 6W12)的络合物的结构。这些发现发表在2021年的《生物化学》杂志上。结合结构支持单一的配体结合模式，并解释了GalNAc优先于Gal的原因。GalNac乙酰胺基团参与了与Mgl的His286的氢键，并使CH−π与Tyr236相互作用(图1A)。
The macrophage galactose-type lectin (MGL, CLEC10A) is the only known receptor on APCs to show preferential binding for N-acetylgalactosamine (GalNAc)(Kd> 100 μM for monovalent GalNAc). Though rarely found on healthy human cells, GalNAc is abundant on the surface of numerous pathogens and tumor cells. MGL’s ability to recognize GalNAc makes this lectin a particularly interesting target for immunomodulatory therapeutics; however, a comprehensive understanding of MGL function on APCs is needed. MGL is a transmembrane receptor: the intracellular signaling domain contains the endocytic YENF motif, while the extracellular domain presents a coiled-coil (CC) region that holds together three structurally distinct carbohydrate recognition domains (CRDs)(Figure 1 A). Each CRD has the signature QPD motif that mediates calcium-dependent binding to GalNAc. Studies suggest that MGL plays a dichotomous role; it can suppress or activate the immune system depending on the structure of the antigen and the conformation of the bound lectin. A protein nuclear magnetic resonance (NMR) study showed the MGL CRD is remarkably flexible, and its conformation is differentially altered upon binding to GalNAc-containing molecules derived from the Forssman antigen, the blood group A antigen, and the GM2 glycolipid. 1 Despite these data, the relationship between the chemical structure of the antigen and MGL signaling remains understudied.We reasoned that the rational design of ligands to activate or suppress MGL signaling would benefit from structural information regarding the MGL CRD and its engagement with GalNAc derivatives. We used X-ray crystallography to determine the structure of MGL CRD in its unbound state (PDBID 6PUV) and in complex with GalNAc derivatives (PDBIDs 6XIY, 6PY1), including the cancer-associated Tn-Ser antigen (PDBID 6W12). These findings were reported in Biochemistry in 2021. The bound structures support a single mode of ligand engagement and explain the preference for GalNAc over Gal. The GalNAc acetamide group is involved in hydrogen bonding to His286 of MGL and makes CH− π interactions with Tyr236 (Figure 1 A).