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

项目总结 细胞增殖增加了对核糖核酸库的需求，以提供增加的RNA，DNA， 和膜合成。这一需求超出了吸收和打捞途径的能力，必须 伴随着新生物合成的增加。特别是，淋巴细胞的增殖依赖于 核苷酸水平，并靶向核苷酸生物合成途径是许多非常成功的基础 免疫抑制治疗。CTP合成酶(CTPS)是嘧啶核苷酸的关键调节酶 生物合成。人类有两种CTPS亚型，分别编码在不同的基因上，CTPS1和CTPS2。而当 CTPS1在增生性组织中的表达普遍增加，其他方面对CTPS1的不同作用知之甚少 两种异构体或它们是如何被调控的。CTPS1在免疫应答中起着关键作用，而 人类的功能突变会导致严重的免疫缺陷。CTPS1缺失导致T和B细胞受损 增殖，但对其他人体组织没有有害影响，表明对 CTPS1功能的免疫应答。因此，选择性抑制CTPS1被认为是一种潜在的 有效的免疫抑制治疗方法，具有有限的非靶向效应。一系列的抑制剂 最近报道了特异性靶向CTPS1的研究，但其抑制机制尚不清楚。这里, 我们主要研究天然变构对CTPS1和CTPS2调控的结构和功能特征 调节剂和选择性小分子抑制剂。这项工作将为核苷酸的控制提供洞察力 在细胞增殖过程中的生物合成，并作为设计和有针对性地发现新的 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.