Over the past decade, we have contributed to the chemistry of microbial natural products and synthetic ligands, related to riboflavin and uracils, that modulate immune cells called mucosal associated invariant T cells (MAIT cells). These highly abundant T lymphocytes were only discovered in 2003 and have become recognized for their importance in mammalian immunology. Unlike other T cells, MAIT cells are not activated by peptide or lipid antigens. In collaboration with immunology and structural biology research groups, we discovered that they are instead activated by unstable nitrogen-containing heterocycles synthesized by bacteria. The most potent naturally occurring activating compound (antigen) is 5-(2-oxopropylideneamino)-d-ribitylaminouracil (5-OP-RU). This compound is an imine (Schiff base) formed through condensation between an intermediate in the biosynthesis of riboflavin (vitamin B2) and a metabolic byproduct of mammalian and microbial glycolysis. Although it is very unstable in water due to intramolecular ring closure or hydrolysis, we were able to develop a non-enzymatic synthesis that yields a pure kinetically stable compound in a nonaqueous solvent. This compound has revolutionized the study of MAIT cell immunology due to its potent activation (EC₅₀ = 2 pM) of MAIT cells and its development into immunological reagents for detecting and characterizing MAIT cells in tissues. MAIT cells are now linked to key physiological processes and disease, including antibacterial defense, tissue repair, regulation of graft-vs-host disease, gastritis, inflammatory bowel diseases, and cancer. 5-OP-RU activates MAIT cells and, like a vaccine, has been shown to protect mice from bacterial infections and cancers. Mechanistic studies on the binding of 5-OP-RU to its dual protein targets, the major histocompatibility complex class I related protein (MR1) and the MAIT cell receptor (MAIT TCR), have involved synthetic chemistry, 2D ¹H NMR spectroscopy, mass spectrometry, computer modeling and molecular dynamics simulations, biochemical, cellular, and immunological assays, and protein structural biology. These combined studies have revealed structural influences for 5-OP-RU in solution on protein binding and antigen presentation and potency; informed the development of potent (EC₅₀ = 2 nM) and water stable analogues; led to fluorescent analogues for detecting and tracking binding proteins in and on cells; and enabled discovery of drugs and drug-like molecules that bind MR1 and modulate MAIT cell function. MAIT cells offer new opportunities for chemical synthesis to enhance the stability, potency, selectivity, and bioavailability of small molecule ligands for MR1 or MAIT TCR proteins, and to contribute to the understanding of T cell immunity and the development of prospective new immunomodulating medicines.

中文翻译：

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黏膜相关不变 T 细胞的化学调节剂

在过去十年中，我们为与核黄素和尿嘧啶相关的微生物天然产物和合成配体的化学做出了贡献，这些配体调节称为粘膜相关不变 T 细胞 (MAIT 细胞) 的免疫细胞。这些高度丰富的 T 淋巴细胞在 2003 年才被发现，并因其在哺乳动物免疫学中的重要性而得到认可。与其他 T 细胞不同，MAIT 细胞不会被肽或脂质抗原激活。我们与免疫学和结构生物学研究小组合作，发现它们被细菌合成的不稳定含氮杂环激活。最有效的天然活化化合物（抗原）是5 -（2-氧代亚丙基氨基）-d-核糖氨基尿嘧啶（5-OP-RU）。该化合物是一种亚胺（席夫碱），通过核黄素（维生素 B2）生物合成中的中间体与哺乳动物和微生物糖酵解的代谢副产物之间的缩合形成。尽管由于分子内闭环或水解，它在水中非常不稳定，但我们能够开发一种非酶合成，在非水溶剂中产生纯的动力学稳定化合物。该化合物彻底改变了 MAIT 细胞免疫学的研究，因为它可以有效地激活 MAIT 细胞 (EC ₅₀ = 2 pM)，并发展成为用于检测和表征组织中 MAIT 细胞的免疫试剂。MAIT 细胞现在与关键的生理过程和疾病有关，包括抗菌防御、组织修复、移植物调节抗宿主病、胃炎、炎症性肠病和癌症。5-OP-RU 激活 MAIT 细胞，并且像疫苗一样，已被证明可以保护小鼠免受细菌感染和癌症。5-OP-RU 与其双重蛋白质靶标、主要组织相容性复合物 I 类相关蛋白 (MR1) 和 MAIT 细胞受体 (MAIT TCR) 结合的机制研究涉及合成化学、2D ¹ H NMR 光谱、质谱光谱学、计算机建模和分子动力学模拟、生化、细胞和免疫学分析，以及蛋白质结构生物学。这些联合研究揭示了溶液中 5-OP-RU 对蛋白质结合和抗原呈递和效力的结构影响；通知强效（EC ₅₀= 2 nM) 和水稳定的类似物；导致用于检测和跟踪细胞内和细胞上的结合蛋白的荧光类似物；并能够发现结合 MR1 并调节 MAIT 细胞功能的药物和药物样分子。MAIT 细胞为化学合成提供了新的机会，以增强 MR1 或 MAIT TCR 蛋白的小分子配体的稳定性、效力、选择性和生物利用度，并有助于理解 T 细胞免疫和开发具有前瞻性的新型免疫调节药物。