How mutations in proinsulin cause diabetes: a protein-misfolding disease

描述（由申请人提供）：胰岛素原突变如何导致糖尿病：一种蛋白质错误折叠疾病胰岛素在脊椎动物代谢的调节中起着核心作用。该激素是单链前体（胰岛素原）的翻译后产物，是一种含有两条链A（21个残基）和B（30个残基）的球状蛋白。人类遗传学的最新进展已经确定了胰岛素基因的显性负突变，导致永久性糖尿病（DM）。这一跨学科应用的目的是研究这种综合征作为蛋白质错误折叠的模型疾病的生化，结构和细胞生物学机制。我们假设临床突变阻断了胰腺细胞内质网（ER）中前体的折叠。突变胰岛素原的结构分析将提供对折叠性的天然决定因素的深入了解。尽管野生型等位基因的表达在其他情况下足以维持稳态，但对相应小鼠模型的研究激发了这样的假设，即错误折叠的变体通过形成含有野生型和突变多肽的非天然聚集体来干扰野生型生物合成。受损的细胞分泌与ER应激、扭曲的细胞器结构和最终的细胞死亡有关。为了验证这一中心假设并确定病理性错误折叠的结构基础，CWRU、密歇根大学和芝加哥大学组建了一个团队，将生物化学、生物物理学、结构生物学、细胞生物学和转基因小鼠模型结合起来。因此，这项合作提案提供了一种令人兴奋的可能性，可以破译蛋白质错误折叠的人类疾病的分子基础。虽然新生儿糖尿病并不常见，但胰岛素原错误折叠和ER应激对代谢综合征和2型糖尿病中的细胞功能障碍机制的贡献将这种应用的意义扩展到不同的人群。

DESCRIPTION (provided by applicant): How mutations in proinsulin cause diabetes: a protein-misfolding disease Insulin plays a central role in the regulation of vertebrate metabolism. The hormone, the post-translational product of a single-chain precursor (proinsulin), is a globular protein containing two chains, A (21 residues) and B (30 residues). Recent advances in human genetics have identified dominant negative mutations in the insulin gene causing permanent neonatal-onset diabetes mellitus (DM). The objective of this interdisciplinary application is to investigate the biochemical, structural, and cell-biological mechanisms of this syndrome as a model disease of protein misfolding. We hypothesize that the clinical mutations block folding of the precursor in the endoplasmic reticulum (ER) of pancreatic ¿-cells. Structural analysis of the mutant proinsulins will provide insight into native determinants of foldability. Although expression of the wild-type allele would in other circumstances be sufficient to maintain homeostasis, studies of a corresponding mouse model motivate the hypothesis that the misfolded variant perturbs wild-type biosynthesis through formation of non-native aggregates containing both wild-type and mutant polypeptides. Impaired ¿-cell secretion is associated with ER stress, distorted organelle architecture, and eventual cell death. To test this central hypothesis and to define the structural bases of pathological misfolding, a team has been assembled at CWRU, University of Michigan, and University of Chicago to bring to bear the combined power of biochemistry, biophysics, structural biology, cell biology, and transgenic mouse models. This collaborative proposal thus offers the exciting possibility of deciphering the molecular basis of a human disease of protein misfolding. Although neonatal diabetes is uncommon, the proposed contribution of proinsulin misfolding and ER stress to the mechanism of ¿-cell dysfunction in the metabolic syndrome and type 2 diabetes mellitus extends the significance of this application to diverse human populations.