Molecular Mechanisms of Dysfunctional Prostaglandin Signaling in the Beta-Cell

描述(申请人提供)：2型糖尿病(T2D)是一种代价高昂且复杂的慢性疾病，是一个严重的公共卫生问题。今天的儿童患糖尿病的总体风险接近50%。因此，开发预防T2D的新方法，识别和正确治疗T2D患者是非常及时和具有重要意义的。T2D的病理生理学与炎症分子有关，如前列腺素E2(PGE2)，一种主要的花生四烯酸代谢产物。β细胞本身表达合成PGE2所需的所有酶，PGE2被认为以自分泌或旁分泌的方式发挥作用，以调节胰岛素的分泌，甚至可能调节β细胞的生长、增殖和生存。尽管这一途径在正常和功能失调的β细胞中具有明显的重要性，但很少有研究探索在β细胞水平上调节PGE2的产生或信号传递的影响，部分原因是对这些途径中重要的分子机制了解不足。我们的长期目标是充分描述正常和糖尿病β细胞中PGE2的合成和信号通路，确定在糖尿病状态下变得功能失调的步骤，并最终出于预防和治疗目的对这些步骤进行调节。这项工作的总体目标是阐明在不同步骤的关键分子相互作用，这些相互作用仍然相对未知，其基本原理是，在完全了解这一重要的β细胞信号通路后，我们将能够更好地利用新颖和创新的方法在T2D预防和治疗中针对功能障碍的β细胞。我们的中心假设是，PGE2合成和信号通路是糖尿病β细胞功能障碍的关键介质，除了环氧合酶-2(COX-2；或前列腺素-内源性过氧化物酶合成酶2，Ptgs2)步骤外，还可以特异性地针对一个或多个关键步骤。我们将检验我们的中心假设，从而通过追求以下三个具体目标来实现这一应用的目标：(1)确定花生四烯酸膜掺入和释放在糖尿病β细胞功能障碍中的作用；(2)确定PGE2受体EP3亚型的C端剪接变异体在偶联G蛋白信号伙伴中的作用；以及(3)阐明EP3下游在促进β细胞功能、复制和生存方面的信号机制。随着这些目标的完成，我们预计将更完整地了解从花生四烯酸到PGE2和其他代谢物的途径，包括PGE2激活其细胞受体如何影响糖尿病β细胞。这样的结果是意料之中的 对这一领域产生重要的积极影响，例如描绘这个早已为人所知但相对 未知的途径，我们可能能够整合文献中的不同结果，揭示和确认T2D预防和治疗的新靶点。

DESCRIPTION (provided by applicant): Type 2 diabetes (T2D) is a costly and complex chronic illness and a serious public health problem. The children of today have an overall lifetime risk of developing diabetes of nearly 50%. Therefore, developing new methods for preventing T2D and identifying and properly treating T2D patients is very timely and of great significance. The pathophysiology of T2D is increasingly being linked with inflammatory molecules such as prostaglandin E2 (PGE2), a major arachidonic acid metabolite. Beta-cells themselves express all of the enzymes required for synthesis of PGE2, which is thought to act in an autocrine or paracrine fashion to regulate insulin secretion and possibly even beta-cell growth, proliferation, and survival. Even with the clear importance of this pathway in the normal and dysfunctional beta-cell, few studies have explored the impact of modulating the production or signaling of PGE2 at the level of the beta-cell, in part because of insufficient knowledge of th molecular mechanisms important in these pathways. Our long-term goal is to fully characterize the PGE2 synthesis and signaling pathways in the normal and diabetic beta-cell, determining steps that become dysfunctional in the diabetic state, and ultimately modulating these steps for preventative and therapeutic purposes. The overall objective of this work is to elucidate critical molecular interactions at distinct steps that have remained relatively uncharacterized, with the rationale that in gaining a complete understanding of this important beta-cell signaling pathway, we will be better able to target the dysfunctional beta-cell in T2D prevention and therapy using novel and innovative approaches. Our central hypothesis is that the PGE2 synthesis and signaling pathway is a critical mediator of diabetic beta-cell dysfunction and can be specifically targeted at one or more key steps besides the well-studied cyclooxygenase-2 (COX-2; or prostaglandin-endoperoxidase synthase 2, PTGS2) step. We will test our central hypothesis and, thereby, accomplish the objective of this application, by pursuing the following three specific aims: (1) Identify the role of arachidonic acid membrane incorporation and release in diabetic beta-cell dysfunction; (2) Determine the role of C-terminal splice variants of the EP3 isoform of the PGE2 receptor in coupling to G-protein signaling partners; and (3) Elucidate the signaling mechanisms downstream of EP3 in promoting beta-cell function, replication, and survival. With the completion of these aims, we anticipate a much more complete understanding of the pathway from arachidonic acid to PGE2 and other metabolites, including how PGE2 activation of its cellular receptor impacts on the diabetic beta-cell. Such results are anticipated to have an important positive impact on the field, as in delineating this long-known but relatively uncharacterized pathway we may be able to meld the discrepant results in the literature and reveal and confirm new targets for the prevention and therapy of T2D.