Genetic analysis of a truncated insulin receptor.

项目总结 支持胰岛素抵抗发展的分子机制仍然不清楚，但 更好地理解这一过程至关重要，因为肥胖、代谢疾病和糖尿病 在美国达到流行状态。我们发现，在蠕虫体内，胰岛素受体的选择性剪接， 小鼠和人类产生截短的异构体，通过抑制能够减弱胰岛素信号 通过全长受体发出信号。这些新异构体的生理意义的测定 在确定它们在胰岛素抵抗的病理生理学中的作用方面至关重要。然而，这类研究在 哺乳动物价格昂贵，耗时长，风险大。相比之下，线虫线虫提供了一种 快速确定它们的生理相关性的经济系统。为此，我们已经开始 鉴定线虫胰岛素受体的截短亚型，称为DAF-2B，即 直接类似于哺乳动物的截短受体，称为IR-C和IR-D。 初步分析表明，daf-2b的表达在不同组织和不同发育过程中有所不同。 重要的是，我们发现截短的daf-2b亚型的基因缺失赋予胰岛素敏感性，而过量的 在蠕虫中表达daf-2b基因会产生与减弱的胰岛素信号相一致的表型。我们 目前正集中于确定DAF-2b调节胰岛素敏感性的机制(S)， 使用一组关于daf-2b动态的新型记者，以及组织特异性基因 DAF-2b的操作。使用一种新的报告菌株，允许可视化差异剪接 体内的全长和截短的daf-2亚型，我们确定了改变 DAF-2b的表达。剪接因子活性调控基因表达机制的探讨 DAF-2b的研究将确定这一途径中的新的调节点和干预点。这些发现在C. 优雅的人现在正在指导对哺乳动物截短的IRS的研究，包括表征作用模式 IR-C和IR-D的表达，以及检测导致这些截短的表达的调控因素 哺乳动物中的受体。最后，对小鼠IR-C和IR-D在体内的表达进行了全面的调查， 相对于全长胰岛素受体，将建立其生理和病理生理调节。 我们假设截短的IR-C和IR-D亚型的异常或错误调节的表达 哺乳动物可能与胰岛素抵抗、糖尿病和其他形式的糖尿病的发病有因果关系。 代谢性疾病。在这方面，识别遗传靶点和调节机制 影响截短的胰岛素受体亚型的表达将加速发现治疗策略 以这种新的胰岛素调节机制为目标。

PROJECT SUMMARY The molecular mechanisms that underpin the development of insulin resistance remain poorly defined, yet a better understanding of this process is critical, given the fact that obesity, metabolic disease and diabetes have reached epidemic status in the US. We discovered that alternative splicing of the insulin receptor, in worms, mice and humans, generates truncated isoforms that are able to attenuate insulin signaling, by inhibiting signaling through the full length receptor. Determination of the physiological significance of these new isoforms is critical in establishing their role in the pathophysiology of insulin resistance. However, such studies in mammals are expensive, time consuming and risky. In contrast, the nematode C. elegans provides an economical system in which to rapidly determine their physiological relevance. To this end, we have started to characterize the truncated isoform of the insulin receptor in the nematode C. elegans, termed DAF-2B, that is directly analogous to mammalian truncated receptors, termed IR-C and IR-D. Preliminary analysis indicates that daf-2b expression varies across tissues and through development. Importantly, we find that genetic deletion of the truncated daf-2b isoform confers insulin sensitivity, while over- expression of a daf-2b cDNA in worms produces phenotypes consistent with attenuated insulin signaling. We are now focused on determining the mechanism(s) by which daf-2b mediates its effects on insulin sensitivity, using a combination of novel reporters that inform on daf-2b dynamics, as well as tissue-specific genetic manipulation of daf-2b. Using a novel reporter strain that permits visualization of differential splicing between the full length and truncated daf-2 isoforms in vivo, we identified specific splicing factors that alter the expression of daf-2b. Exploration of the mechanism by which splicing factor activity regulates the expression of daf-2b will identify novel points of regulation and intervention in this pathway. These discoveries in C. elegans are now guiding studies of the mammalian truncated IRs, including characterization the mode of action of IR-C and IR-D, as well as examining the regulatory factors that lead to expression of these truncated receptors in mammals. Finally, a comprehensive survey of the expression of murine IR-C and IR-D in vivo, relative to full length insulin receptors, will establish their physiological and pathophysiological regulation. We hypothesize that aberrant or mis-regulated expression of truncated IR-C and IR-D isoforms in mammals could be causally involved in the pathogenesis of insulin resistance, diabetes and other forms of metabolic disease. In this respect, the identification of genetic targets and regulatory mechanisms that influence expression of truncated insulin receptor isoforms will expedite the discovery of therapeutic strategies that target this novel insulin regulatory mechanism.