Arginine regulation of alpha cell proliferation and function

项目摘要 传统上，糖尿病被定义为导致葡萄糖稳态受损的胰岛素作用降低。 然而，胰高血糖素的不适当分泌也有助于糖尿病中的高血糖症。阻挡 胰高血糖素作用降低血糖，但也导致高胰高血糖素血症，伴随α细胞增殖， 增生我们证明，这是由于血液中的氨基酸水平高， 肝脏中的氨基酸催化剂（再生）。这些研究证明了经典的内分泌反馈 loop，肝-胰岛α细胞轴。作为我们K 01资助调查的一部分，我们发现， 精氨酸是高氨基酸水平对α细胞增殖和功能的影响所必需的。我们确定 SLC 7A 2（CAT 2）是胰岛α细胞中的主要精氨酸转运蛋白。使用全基因CAT 2敲除小鼠， 我们发现CAT 2的缺失会导致α细胞增生的保护和胰高血糖素的完全缺失 分泌，甚至对强去极化剂作出反应。这表明CAT 2在这一过程中发挥着重要作用。 在α细胞中，除了影响膜极化外， 尼古丁刺激的分泌。我们目前的目的是明确姜黄素刺激α细胞的机制， 增殖和分泌。在目标1中R 01的支持下，我们将描述α细胞的变化 当使用α细胞特异性靶向缺失使CAT 2表达丧失时，包括α细胞增殖和质量， 胰高血糖素分泌、Ca 2+动力学以及基因和蛋白质表达。我们还将测试异二聚体 氨基酸交换器LAT 2（SLC 7A 8/SLC 3A 2）是α细胞增殖和功能所必需的。在目标2中， 将研究一种名为TM 4SF 4的新型推定精氨酸细胞表面结合蛋白，该蛋白具有选择性和 在胰腺α细胞上稳健表达。我们将充分表征TM 4SF 4精氨酸结合动力学、蛋白质 α细胞中的结合伴侣，对精氨酸转运的影响，以及α细胞增殖和功能的调节。一个 我们工作的一个重要特点是，我们将把我们在小鼠胰岛中的发现转化为人类胰岛。 这些研究将为正常α细胞功能以及α细胞如何靶向修复提供新的见解 糖尿病中胰高血糖素分泌失调。

PROJECT SUMMARY Traditionally, diabetes is defined as decreased insulin action resulting in impaired glucose homeostasis. However, inappropriate secretion of glucagon also contributes to the hyperglycemia in diabetes. Blocking glucagon action lowers blood glucose, but also leads to hyperglucagonemia with α cell proliferation and hyperplasia. We demonstrated that this is due to high blood levels of amino acids resulting from impaired amino acid catabolism in liver (gluconeogenesis). These studies demonstrated a classical endocrine feedback loop, the liver-islet α cell axis. As part of our K01 funded investigations, we discovered that high levels of arginine are required for the effects of high amino acid levels on α cell proliferation and function. We identified SLC7A2 (CAT2) is the major arginine transporter in pancreatic islet α cells. Using global CAT2 knockout mice, we found that loss of CAT2 results in protection from α cell hyperplasia and a complete loss of glucagon secretion even in response to strong depolarizing agents. This suggests that CAT2 is playing an important role in α cells beyond affecting membrane polarization as had been previously proposed as a mechanism for arginine-stimulated secretion. Our current objective is to define the mechanisms of arginine-stimulated α cell proliferation and secretion. Under the support of this R01 in Aim 1, we will characterize changes in the α cell when CAT2 expression is lost using α cell specific targeted deletion, including α cell proliferation and mass, glucagon secretion, Ca2+ dynamics, and gene and protein expression. We will also test if the heterodimeric amino acid exchanger LAT2 (SLC7A8/SLC3A2) is required for α cell proliferation and function. In Aim 2, we will examine a novel putative arginine cell surface binding protein called TM4SF4 that is selectively and robustly expressed on pancreatic α cells. We will fully characterize TM4SF4 arginine binding kinetics, protein binding partners in α cells, effects on arginine transport, and regulation of α cell proliferation and function. An important feature of our work is that we will translate our discoveries made in mouse islets using human islets. These studies will provide new insights into normal α cell function and how α cells could be targeted to repair dysregulated glucagon secretion in diabetes.