Protein Succination: a Mechanistic Mediator of Adipocyte Dysfunction in Diabetes

 描述(申请人提供)：考虑到大约2,600万美国人患有糖尿病，估计有7,900万人患有糖尿病前期，我们必须了解脂肪组织膨胀在全身代谢功能障碍发展中的作用。然而，脂肪组织功能障碍的许多生化机制仍不清楚。此前，我们已经检测到S-(2-琥珀醇)半胱氨酸(2SC)，也被称为蛋白质琥珀酸化，一种新的蛋白质翻译后修饰。2SC是由Krebs环中间体富马酸与蛋白质中反应性半胱氨酸残基反应形成的。在糖尿病的脂肪细胞中，富马酸和琥珀酸化的蛋白质似乎选择性地增加，从而损害蛋白质的结构和功能。富马酸的增加是由于过量的燃料供应，ATP和NADH的积累，内线粒体膜(IMM)超极化，从而反馈抑制Krebs循环。这一假设认为，蛋白质琥珀酸化增加是线粒体应激和错误折叠蛋白质积累之间的一种新的机制联系，从而导致糖尿病脂肪细胞内质网(ER)应激。此外，我们认为氧化还原活性蛋白的琥珀酸化调节糖尿病的氧化还原应激。该项目有3个具体目标：(1)检测富马酸在脂肪细胞中积累和选择性琥珀酸化作用的影响；(2)确定琥珀酸化作用是否在脂肪细胞线粒体和内质网应激之间存在机械联系；(3)检测富马酸与蛋白质硒半胱氨酸作为一种新的氧化还原调节剂的反应性。我们计划使用一种新型的基因敲除小鼠，在脂肪组织中选择性地积累富马酸。在这些研究完成后，我们将证明脂肪细胞蛋白琥珀酸化在糖尿病代谢功能障碍中的重要贡献，对开发治疗线粒体疾病的新的治疗途径具有重要意义。

 DESCRIPTION (provided by applicant): Considering that ~26 million Americans have diabetes and an estimated 79 million have prediabetes, it is critical that we understand the role of expanding adipose tissue mass in the development of systemic metabolic dysfunction. However, many of the biochemical mechanisms underlying adipose tissue dysfunction remain unclear. Previously, we have detected S-(2-succinol)cysteine (2SC), also termed protein succination, a new chemical post-translational modification of proteins. 2SC is formed by reaction of the Krebs cycle intermediate fumarate with reactive cysteine residues in protein. Both fumarate and succination of proteins appear to be selectively increased in adipocytes in diabetes, impairing protein structure and function. The increase in fumarate develops as a result of excess fuel supply, accumulation of ATP and NADH, inner mitochondrial membrane (IMM) hyperpolarization and consequently feedback inhibition of the Krebs cycle. This proposal hypothesizes that the increase in protein succination is a novel mechanistic link between mitochondrial stress and the accumulation of misfolded proteins, contributing to endoplasmic reticulum (ER) stress in the adipocyte in diabetes. In addition, we propose that the succination of redox-active proteins modulates redox stress in diabetes. This project has 3 specific aims: (1) To examine the impact of fumarate accumulation and selective succination in the adipocyte; (2) To determine if succination mechanistically links mitochondrial and ER stress in the adipocyte; and (3) To examine the reactivity of fumarate with protein selenocysteines as a novel redox modulator. We plan to use a novel knockout mouse with selective fumarate accumulation in the adipose tissue. Upon completion of these studies, we will demonstrate the significant contribution of adipocyte protein succination to metabolic dysfunction in diabetes, with important implications for the development of novel therapeutic avenues for the treatment of mitochondrial diseases.