ChREBP Isoforms in Pancreatic Beta Cells

胰腺 β 细胞中的 ChREBP 亚型

• 批准号: 9914106
• 负责人: DONALD K. SCOTT
• 金额: $ 41.19万
• 依托单位: ICAHN SCHOOL OF MEDICINE AT MOUNT SINAI
• 依托单位国家: 美国
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-04-18 至 2021-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9914106
• 关键词: Adenoviruses; Adipose tissue; Alternative Splicing; Apoptosis; Beta Cell; Binding; Binding Proteins; Carbohydrates; Cell Death; Cell Nucleus; Cell Proliferation; Cell physiology; Data; Diabetes Mellitus; Gene Expression; Genes; Genetic Transcription; Glucose; Goals; Human; Hyperglycemia; In Vitro; Insulin-Dependent Diabetes Mellitus; Islet Cell; Islets of Langerhans Transplantation; Lead; Length; Liver; LoxP-flanked allele; Mediator of activation protein; Molecular; Mus; Non-Insulin-Dependent Diabetes Mellitus; Nuclear; Nuclear Export; Outcome; Pathway interactions; Physiological; Protein Isoforms; Research Personnel; Response Elements; Rodent; SCID Mice; Signal Transduction; Streptozocin; Structure of beta Cell of islet; System; Testing; Therapeutic; Toxic effect; Transplantation; Viral; blood glucose regulation; diabetic; gain of function; gene product; glucose metabolism; improved; in vivo; insulin sensitivity; islet; lipid biosynthesis; loss of function; novel; overexpression; promoter; tool

Expansion of functional pancreatic beta cell mass is a major therapeutic goal for both Type 1 and Type 2 diabetes. Glucose is a key physiological driver of adaptive beta cell mass expansion, promoting beta cell proliferation both in vitro and in vivo. We have been studying mechanisms of glucose-regulated gene expression for nearly two decades. In 2012 we found that carbohydrate response element binding protein (ChREBP; Mlxipl) is required for glucose-stimulated beta cell proliferation in both rodent and human beta cells. That same year, our co-investigator (Dr. Mark Herman) discovered that ChREBP exists as 2 major isoforms. ChREBPα is the full-length form that is mostly cytoplasmic and repressed in low glucose. ChREBPβ is a product of alternative splicing, with the nuclear export signals and the low glucose inhibitory domain removed. Consequently, ChREBPβ is mostly nuclear, and is constitutively and potently active. ChREBPβ transcription is induced by a powerful carbohydrate response element after activation of the glucose-responsive ChREBPα, creating a vigorous feed-forward loop (Fig. 1). Remarkably, in every system studied in detail, the induction of ChREBPβ is the molecular engine that drives the major physiological effects of ChREBP. In adipose tissue or liver, induction of ChREBPβ increases de novo lipogenesis and either increases or decreases insulin sensitivity, respectively.. In beta cells, we recently showed that the exponential induction of ChREBPβ - from a nearly undetectable level to amounts comparable to ChREBPα - is required for glucose-stimulated proliferation. Strikingly, however, overexpression of ChREBPβ in beta cells, as may happen with prolonged hyperglycemia or by ectopic viral expression, results in beta cell apoptosis. In stark contrast, overexpression of ChREBPα amplifies glucose-stimulated beta cell proliferation without cell death. Our overarching hypothesis is that the ratio of ChREBPα to ChREBPβ abundance is critically important for beta cell function, both for beta cell mass expansion and, when dysregulated, as a mediator of glucose toxicity. We will test our hypothesis by performing the following Specific Aims: (1) Determine the effects of increasing or decreasing the abundance of ChREBPβ specifically in beta cells on beta cell mass and glucose homeostasis; (2) Determine if exogenous expression of ChREBPα or ChREBPβ in human islets improves or worsens islet transplantation outcomes; and (3) Determine how the ratio of ChREBPα to ChREBPβ controls the fate of beta cells. This application uses novel tools that will provide an essential mechanistic understanding of transcriptional glucose sensing that will inform therapies to expand and protect beta cell mass.

功能性胰腺β细胞量的扩展是1型和2型糖尿病的主要治疗目标。葡萄糖是自适应β细胞质量膨胀的关键生理驱动力，在体外和体内促进β细胞增殖。我们一直在研究葡萄糖调节基因表达的机制已有近二十年了。在2012年，我们发现啮齿动物和人β细胞中葡萄糖刺激的β细胞增殖需要碳水化的反应元件结合蛋白（CHREBP； MLXIPL）。同年，我们的共同投资者（马克·赫尔曼（Mark Herman）博士）发现Chrebp是2个主要同工型。 Chrebpα是全长形式，主要是细胞质的，反射在低葡萄糖中。 CHREBPβ是替代剪接的产物，核出口信号和低葡萄糖抑制结构域已移除。因此，Chrebpβ主要是核的，并且始终如一且潜在的活跃。激活葡萄糖反应性chrebpα之后，CHREBPβ转录是由强大的碳水化合物反应元件诱导的，从而产生了剧烈的前馈环（图1）。值得注意的是，在每个详细研究的系统中，Chrebpβ的诱导是驱动Chrebp的主要物理作用的分子发动机。在脂肪组织或肝脏中，Chrebpβ的诱导分别增加了从头脂肪生成，并分别增加或降低胰岛素敏感性。在β细胞中，我们最近表明，从几乎无法检测到的水平与CHREBPα-相当的含量与Chrebpα-相当的数量，需要与Chrebpα-相当。然而，引人注目的是，β细胞中chrebpβ的过表达，就像长期高血糖或异位病毒表达可能发生的那样，导致β细胞凋亡。在鲜明的对比中，Chrebpα放大器葡萄糖刺激的β细胞增殖无细胞死亡的过表达。我们的总体假设是，Chrebpα与Chrebpβ抽象的比率对于β细胞功能至关重要，无论是β细胞质量膨胀，而当失调时，作为葡萄糖毒性的介体。我们将通过 执行以下特定目的：（1）确定增加或减少丰度的影响 Chrebpβ在β细胞质量和葡萄糖稳态上的β细胞中专门在β细胞中； （2）确定人类胰岛中Chrebpα或Chrebpβ的外源表达是否改善或恶化胰岛移植结果； （3）确定Chrebpα与Chrebpβ的比率如何控制β细胞的命运。该应用程序使用新工具，将提供对转录葡萄糖传感的基本机械理解，该传感将为疗法提供扩展和保护β细胞量的疗法。