Isocitrate dehydrogenase (IDH) mutations as drivers of organelle stress and dysfunction"

摘要/摘要 异柠檬酸脱氢酶1(IDH1)和IDH2突变在癌症中的后果是不寻常的。尽管 这些突变导致依赖于异柠檬酸的NADP转换的正常活性的功能丧失 对于α-酮戊二酸(αKG)来说，突变的IDH更多的是一种癌基因，而不是肿瘤抑制因子，作为一种新的活性 还推断：αKG依赖于NADPH产生肿瘤代谢物D-2-羟基戊二酸(D2HG)。 D2HG抑制αKG依赖的酶，如脱氧核糖核酸和组蛋白去甲基酶，NADPH耗竭导致 氧化应激。影响IDH1中残基R132的各种点突变可以赋予这些催化特性， 导致显著的结构修改，使突变的IDH1成为真正的药物靶点。事实上，一种自我- 选择性变构突变体IDH1抑制剂现已进入临床。突变体和野生型IDH1都定位于细胞质和 过氧化物体，而IDH2存在于线粒体中，这增加了细胞器特有后果的可能性 IDH突变，尽管这一点还没有被研究。有趣的是，有一条通信管道在 过氧酶体和线粒体在脂质加工和缓解糖尿病中起着相互联系的作用 氧化应激，尽管IDH在这种交流中的作用尚不清楚。到目前为止，有几个限制 限制了突变IDH研究的严谨性。首先，外推了R132H-IDH1的催化和抑制谱 对于其他与疾病相关的IDH1突变体，尽管我们显示了几个突变体具有非常独特的特征。第二, 在研究后果时，NADPH耗竭以及氧化应激的作用常常被忽视。 D2HG。第三，研究集中在突变体IDH1的全局/胞质贡献上，而忽略了它的SOLE作用 NADPH和αKG在该细胞器中产生。然而，我们报告了脂质生物合成功能障碍的证据。 引入细胞IDH1突变时过氧化体中的途径。我们研究的总体目标是 程序是确定代谢酶的催化、调节、抑制和细胞/组织的机制。 细胞在健康和疾病中的功能，从化学物质到细胞水平。通过利用动力、结构、 细胞和组学技术，我们可以确定与疾病相关的突变的独特后果 代谢酶的变种。在这里，我们已经确定了关键问题来阐明突变的IDH1的作用 疾病：1)蛋白质动力学如何影响IDH1的催化和抑制？2)氧化的影响是什么？ IDH1和IDH2的压力？3)IDH1突变的细胞器特有的后果是什么？4)IDH1突变的 IDH1突变在细胞器串扰中的作用？通过这项工作，我们将发现基本的催化和 影响WT和突变型IDH活性的调节策略，确定IDH1在过氧体和 确定该位置突变的独特后果，并确定突变的IDH1在促进 过氧化体/线粒体脂质生物合成和氧化应激信号。在完成这项工作后，我们将 开发有价值的新工具，并确定可能在治疗上有针对性的途径或机制。

ABSTRACT/SUMMARY The consequences of mutations in isocitrate dehydrogenase 1 (IDH1) and IDH2 in cancer are unusual. Though these mutations confer a loss of function of the normal activity of the NADP+-dependent conversion of isocitrate to α-ketoglutarate (αKG), mutant IDH is more of an oncogene than tumor suppressor, as a neomorphic activity is also conferred: the NADPH-dependent production of oncometabolite D-2-hydroxyglutarate (D2HG) from αKG. D2HG inhibits αKG-dependent enzymes like DNA and histone demethylases, and NADPH depletion results in oxidative stress. A variety of point mutations affecting residue R132 in IDH1 can grant these catalytic properties, causing prominent structural modifications that allow mutant IDH1 to be a bona fide drug target. Indeed, a se- lective allosteric mutant IDH1 inhibitor is now in the clinic. Both mutant and WT IDH1 localize to the cytosol and peroxisomes, while IDH2 is found in the mitochondria, raising the possibility of organelle-specific consequences of IDH mutations, though this has not yet been explored. Interestingly, there is a communication pipeline between the peroxisomes and mitochondria in that they share an interconnected role in lipid processing and mitigation of oxidative stress, though the role of IDH in this communication is not yet known. To date, several limitations have restricted the rigor of mutant IDH studies. First, the catalytic and inhibition profile for R132H IDH1 is extrapolated to other disease-relevant IDH1 mutants, though we show several mutants have very unique profiles. Second, the role of NADPH depletion, and thus oxidative stress, is often overlooked in favor of studying consequences of D2HG. Third, studies focus on the global/cytosolic contributions of mutant IDH1, ignoring its role of sole NADPH and αKG producer in this organelle. However, we report evidence of dysfunctional lipid biosynthetic pathways in the peroxisomes upon introduction of cellular IDH1 mutations. The overall goal of our research program is to determine the mechanisms of metabolic enzyme catalysis, regulation, inhibition, and cellular/orga- nellular function in health and disease, from the chemical to the cellular levels. By leveraging kinetic, structural, cellular, and -omics technologies, we can establish the unique consequences of disease-relevant mutational variants in metabolic enzymes. Here, we have identified critical questions to illuminate the role of mutant IDH1 in disease: 1) How do protein dynamics affect IDH1 catalysis and inhibition? 2) What are the effects of oxidative stress on IDH1 and IDH2? 3) What are the organelle-specific consequences of IDH1 mutations? 4) What are the roles of IDH1 mutations in organelle crosstalk? Through this work, we will uncover fundamental catalytic and regulatory strategies affecting WT and mutant IDH activity, determine the role of IDH1 in the peroxisomes and identify the unique consequences of mutation at this location, and establish the role of mutant IDH1 in facilitating peroxisomal/mitochondrial lipid biosynthesis and oxidative stress signalling. Upon completing this work we will generate valuable new tools, and identify pathways or mechansims that may be therapeutically targetable.