Clarifying pathogenesis of MIDY - a new form of diabetes mellitus

阐明 MIDY 的发病机制 - 一种新型糖尿病

• 批准号: 9320635
• 负责人: Corey Nathaniel Cunningham
• 金额: $ 3.52万
• 依托单位: UNIVERSITY OF MICHIGAN AT ANN ARBOR
• 依托单位国家: 美国
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-05-01 至 2019-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9320635
• 关键词: Alleles; Anabolism; Autoantibodies; Beta Cell; Binding; Blood Glucose; Cell physiology; Cleaved cell; Complex; Coupled; Cytosol; Data; Degradation Pathway; Diabetes Mellitus; Disease; Dominant-Negative Mutation; Endoplasmic Reticulum; Endoplasmic Reticulum Degradation Pathway; Generations; Genes; Goals; Golgi Apparatus; Human; INS gene; Insulin; Insulin-Dependent Diabetes Mellitus; Membrane; Metabolic syndrome; Missense Mutation; Molecular Chaperones; Molecular Weight; N-terminal; Pathogenesis; Pathogenicity; Pathway interactions; Patients; Peptide Signal Sequences; Play; Process; Proinsulin; Proteins; Quality Control; Reaction; Role; Route; Secretory Vesicles; Structure of beta Cell of islet; Sum; Syndrome; Testing; Triage; Up-Regulation; Youth; blood glucose regulation; disease phenotype; disulfide bond; endoplasmic reticulum stress; gain of function; insight; insulin secretion; misfolded protein; multicatalytic endopeptidase complex; mutant; novel; overexpression; peptide hormone; preproinsulin; prevent; restoration; secretory protein; therapeutic development

Abstract Diabetes mellitus (DM) is a metabolic syndrome caused by the insufficient secretion of insulin, a peptide hormone secreted by pancreatic β-cells to control blood glucose levels. To initiate insulin secretion, the precursor proinsulin translocates into the endoplasmic reticulum (ER) where it undergoes oxidative folding. Properly folded proinsulin exits the ER, sorts to the Golgi apparatus, and then secretory granules where proinsulin is processed to form insulin poised for secretion. Recent analysis of the human insulin gene revealed nearly 30 missense mutations that cause proinsulin to misfold in the ER, resulting in a new syndrome called Mutant INS-gene-induced Diabetes of Youth (MIDY). These mutant proinsulins exert a toxic gain-of- function effect on wildtype (WT) insulin secretion by forming high molecular weight (MW) aggregates with WT proinsulin in the ER – this engagement blocks WT proinsulin ER exit, maturation, and secretion. Decreases in insulin secretion result in upregulation of even more WT and mutant proinsulin, thereby exacerbating beta cell ER stress due to accumulation of misfolded proteins. Whether these mutant proinsulins are degraded, and if so, whether their selective degradation might liberate WT proinsulin that allows for its secretion, are unknown. In this context, we recently identified the ER-associated degradation (ERAD) pathway as responsible for degrading the classic MIDY mutant Akita; ERAD is a key ER quality control process that disposes misfolded ER proteins to the cytosol for proteasomal degradation. Our unpublished findings now suggest that an ER- resident factor called Grp170 targets Akita for disposal via ERAD. We hypothesize that Grp170 does so by untangling Akita from the high MW aggregates, generating smaller Akita oligomers that undergo ERAD. Importantly, as WT proinsulin is also disentangled in this reaction, it efficiently exits the ER, matures, and is secreted. Grp170-induced Akita degradation thus restores insulin secretion and alleviates the MIDY disease. To test this hypothesis, we will clarify how Grp170 promotes Akita for ERAD-dependent degradation (Aim 1), and elucidate if WT insulin secretion can be restored by stimulating Grp170-induced Akita degradation (Aim 2). In sum, this proposal seeks to reveal the basic pathogenic mechanism underlying a form of DM called MIDY.

摘要 糖尿病（DM）是一种代谢综合征，由胰岛素（一种肽）分泌不足引起 胰腺β细胞分泌的控制血糖水平的激素。为了启动胰岛素分泌， 前体胰岛素原易位到内质网（ER）中，在内质网中进行氧化折叠。 正确折叠的胰岛素原离开内质网，分类到高尔基体，然后是分泌颗粒， 胰岛素原被加工形成准备分泌的胰岛素。人胰岛素基因的研究进展 揭示了近30个错义突变，导致胰岛素原在ER中错误折叠，导致一种新的综合征 名为突变INS基因诱导的青年糖尿病（MIDY）。这些突变的胰岛素原发挥毒性增益- 通过与野生型（WT）形成高分子量（MW）聚集体对野生型（WT）胰岛素分泌的功能影响 ER中的胰岛素原-这种接合阻断WT胰岛素原ER的退出、成熟和分泌。减少 胰岛素分泌导致甚至更多WT和突变胰岛素原的上调，从而加重β细胞 由于错误折叠蛋白质的积累而导致的ER应激。这些突变的胰岛素原是否被降解， 因此，它们选择性降解是否可能释放WT胰岛素原以允许其分泌，是未知的。 在这种情况下，我们最近确定了ER相关降解（ERAD）途径， 降解经典的MIDY突变体秋田; ERAD是一个关键的ER质量控制过程， ER蛋白质进入胞质溶胶进行蛋白酶体降解。我们未发表的研究结果现在表明，ER- 名为Grp 170的常驻因子将秋田作为目标，通过ERAD进行处置。我们假设Grp 170通过以下方式实现这一点： 从高MW聚集体中解开秋田，产生经历ERAD的较小的秋田低聚物。 重要的是，由于WT胰岛素原也在该反应中解缠结，因此其有效地离开ER，成熟，并被释放。 秘密的Grp 170诱导的秋田降解从而恢复胰岛素分泌并缓解MIDY疾病。 为了验证这一假设，我们将阐明Grp 170如何促进秋田的ERAD依赖性降解（目的1）， 并阐明是否可以通过刺激Grp 170诱导的秋田降解来恢复WT胰岛素分泌（目的2）。 总之，该建议旨在揭示一种称为MIDY的DM形式的基本致病机制。