Allosteric regulation of lysine degradation as a novel pathophysiological mechanism in glutaric aciduria type 1

项目总结/摘要 在这个项目中，研究人员建议研究调节赖氨酸降解的变构机制 并获得对罕见孤儿疾病戊二酸尿症1型（GA 1）的新病理生理学见解。GA 1是 赖氨酸、羟赖氨酸和色氨酸降解的常染色体隐性遗传缺陷。患者可以提出 伴有脑萎缩和大头畸形，并可能在急性脑病危象后发生肌张力障碍， 纹状体变性这种疾病是由戊二酰辅酶A脱氢酶（GCDH）缺乏引起的， 导致神经毒性谷氨酸和3-羟基谷氨酸的积累。GA 1被认为是可治疗的 因此，许多国家将其纳入新生儿筛查计划。目前的治疗 包括饮食干预，肉毒碱补充剂，和紧急治疗， 护理人员、患者和临床团队的努力。它必须精心维护，但在25%的患者中， 神经系统疾病仍在发展，其结果反映了历史上的健康不平等和社会不平等。 疾病的决定因素。因此，GA 1治疗需要进一步改进，但新疗法的开发 由于对病理生理机制的理解有限而受到阻碍。在人类患者和GA 1中， 在小鼠模型中，有症状的疾病伴随着神经毒性谷胱甘肽和3- 羟基谷氨酸积累。研究人员推测，有毒代谢物的积累， 由于GCDH的缺乏，GA 1受到赖氨酸降解途径的变构调节的控制。中 高通量筛选，他们已经确定了小分子抑制剂和激活剂的赖氨酸-2- 2-氨基己二酸半醛合酶（AASS）的酮戊二酸还原酶结构域（LOR）。这导致 发现了这种关键酶在赖氨酸降解中的变构调节的显着潜力。结构 研究揭示了LOR中两个新的变构位点，一个能够结合抑制剂，另一个能够结合活化剂。 因此，本提案的总体目标是了解赖氨酸降解的变构调节。 本论文将研究LOR/AASS变构调节的结构和生化机制 使用LOR/AASS与变构激活剂/抑制剂复合的X射线晶体学和酶学。在 目的2、LOR/AASS变构调节的生物学意义及其在决定赖氨酸中的作用 将研究降解通量。研究者将鉴定内源性抑制剂和激活剂， LOR/AASS，并定义了AASS的天然蛋白质相互作用网络。这些知识将用于定义 这种变构机制如何控制赖氨酸降解并促进GA 1中代谢物的积累 细胞系模型在AIM 3中，LOR/AASS的中性活化剂将使用药物组合开发， 化学和基于结构的药物设计本项目的最终目标是更好地了解 GA 1的病理生理学，并提供新的治疗选择。

Project Summary / Abstract In this project, the investigators propose to study the allosteric mechanisms that regulate lysine degradation and gain novel pathophysiological insights into the rare orphan disease glutaric aciduria type 1 (GA1). GA1 is an autosomal recessive inborn error of lysine, hydroxylysine and tryptophan degradation. Patients can present with brain atrophy and macrocephaly and may develop dystonia after acute encephalopathic crises that lead to striatal degeneration. The disorder is caused by a deficiency of glutaryl-CoA dehydrogenase (GCDH), which leads to the accumulation of neurotoxic glutaric acid and 3-hydroxyglutaric acid. GA1 is considered a treatable disorder and therefore included in newborn screening programs in many countries. However, current treatment consists of dietary intervention, carnitine supplementation, and emergency treatment which requires intense efforts from both caregiver, patient and clinical team. It must be meticulously maintained, but in 25% of patients neurological disease still develops with the outcome reflecting historical health inequities and social determinants of disease. Thus, GA1 treatment needs further improvement, but development of new therapies is hampered by limited understanding of pathophysiological mechanisms. In human patients and the GA1 mouse model, symptomatic disease is accompanied by a striking increase in neurotoxic glutaric- and 3- hydroxyglutaric acid accumulation. The investigators hypothesize that the accumulation of toxic metabolites in GA1 due to the deficiency of GCDH is controlled by allosteric regulation of the lysine degradation pathway. In a high throughput screen, they have identified small molecule inhibitors and activators of the lysine-2- oxoglutarate reductase domain (LOR) of 2-aminoadipic semialdehyde synthase (AASS). This led to the discovery of a remarkable potential for allosteric regulation of this key enzyme in lysine degradation. Structural studies revealed two novel allosteric sites in LOR, one able to bind inhibitors, the other binding activators. Therefore the overall objective of this proposal is to understand the allosteric regulation of lysine degradation. In AIM 1, the structural and biochemical mechanisms of allosteric regulation of LOR/AASS will be studied using X-ray crystallography of LOR/AASS in complex with allosteric activators/inhibitors and enzymology. In AIM 2, the biological significance of allosteric regulation of LOR/AASS and its role in determining lysine degradation flux will be studied. The investigators will identify endogenous inhibitors and activators of LOR/AASS, and define the native protein interaction network of AASS. This knowledge will be used to define how this allosteric mechanism controls lysine degradation and contributes to metabolite accumulation in a GA1 cell line model. In AIM 3, neutral activators of LOR/AASS will be developed using a combination of medicinal chemistry and structure-based drug design. The ultimate goal of this project is to better understand the pathophysiology of GA1 and provide new treatment options.