Structural basis for differential regulation and selective inhibition of human CTP synthase 1

项目摘要 细胞增殖增加了对核糖核苷酸库的需求，以提供增加的RNA，DNA， 和膜合成。这种需求超过了吸收和回收途径的能力，必须 通过增加从头生物合成来满足。特别是，淋巴细胞增殖依赖于增加的 核苷酸水平，靶向核苷酸生物合成途径是许多高度成功的基础 免疫抑制治疗。CTP合成酶（CTPS）是嘧啶核苷酸合成的关键调控酶 生物合成人类有两种CTPS同种型编码在不同的基因上，CTPS1和CTPS2。而 CTPS1的表达通常在增殖组织中增加，但关于CTPS1的不同作用知之甚少。 这两种异构体或它们是如何被调节的。CTPS1在免疫应答中起着关键作用，并且CTPS1的丧失是免疫应答的一部分。 人类的功能突变导致严重的免疫缺陷。CTPS1的缺失导致T和B细胞受损 增殖，但在其他人体组织中不具有有害作用，表明对细胞增殖的独特依赖性。 CTPS1功能的免疫应答。因此，CTPS1的选择性抑制被认为是一种潜在的 这是一种强有力的免疫抑制治疗方法，具有有限的脱靶效应。一些抑制剂， 特异性靶向CTPS1的抑制剂最近已有报道，但其抑制机制仍不清楚。在这里， 我们重点关注天然变构蛋白对CTPS1和CTPS2调节的结构和功能特征， 调节剂和选择性小分子抑制剂。这项工作将提供深入了解控制核苷酸 在细胞增殖过程中的生物合成，并作为基础的设计和有针对性的发现， 具有免疫抑制治疗潜力的化合物。

PROJECT SUMMARY Cellular proliferation increases demand for ribonucleotide pools to provide precursors for increased RNA, DNA, and membrane synthesis. This demand exceeds the capacity of uptake and salvage pathways, and must be met by increased de novo biosynthesis. In particular, lymphocyte proliferation is dependent on increased nucleotide levels, and targeting nucleotide biosynthesis pathways is the basis for a number of highly successful immunosuppressive treatments. CTP Synthase (CTPS) is the key regulatory enzyme in pyrimidine nucleotide biosynthesis. Humans have two CTPS isoforms encoded on separate genes, CTPS1 and CTPS2. While CTPS1 expression is generally increased in proliferative tissues, little else is known about differential roles of the two isoforms or how they are regulated. CTPS1 plays a critical role in the immune response, and loss of function mutations in humans cause severe immunodeficiency. Loss of CTPS1 results in impaired T and B-cell proliferation, but does not have deleterious effects in other human tissues, indicating unique dependence of the immune response on CTPS1 function. Selective inhibition of CTPS1, therefore, is considered a potentially powerful approach to immunosuppressive therapies with limited off-target effects. A number of inhibitors that specifically target CTPS1 have recently been reported, but the mechanisms of inhibition remain unclear. Here, we focus on the structural and functional characterization of CTPS1 and CTPS2 regulation by native allosteric regulators and by selective small molecule inhibitors. This work will provide insight into the control of nucleotide biosynthesis during cellular proliferation, and serve as the basis for design and targeted discovery of novel compounds with potential for immunosuppressive therapies.