MAP KINASE IN ISLET FUNCTION

描述（由申请人提供）：糖尿病是一个巨大的健康负担，由于生活质量下降和治疗费用上升。仅在美国，约8%的人口患有糖尿病，目前估计近三分之一的成年人有患糖尿病的风险。肥胖、胰岛素抵抗和肝脏、脂肪和肌肉的代谢异常是疾病的重要因素。然而，最近发现的大多数与2型糖尿病相关的基因位点编码的蛋白质使胰腺细胞能够产生胰岛素。营养物质和激素不仅调节胰岛素的分泌，而且还调节细胞继续产生胰岛素的能力。在这个建议中，我们关注的作用机制的营养物质和药剂，提高胰岛素的生产在细胞中。总体目标是阐明可操纵的机制，以改善细胞功能，克服长期高血糖期间细胞发生的生理变化，导致胰岛素释放不足。在目标1中，我们将确定胰腺细胞中味觉受体复合物（T1R1/T1R3）的功能。这种二聚体G蛋白偶联受体（GPR）参与氨基酸感应。这种受体在味觉神经元中被发现，与多种氨基酸结合，但尚未在细胞上进行研究。我们发现T1R3的稳定下调会减少胰岛素分泌和胰岛素含量，并导致与自噬相关的事件。我们将探索这些表型变化的基础，我们也将研究潜在的信号机制。在第二个目标中，我们将研究增强β细胞功能的小分子作用的分子机制。这些分子刺激细胞产生胰岛素，改善小鼠的口服葡萄糖耐量，并在长期培养中恢复人胰岛产生胰岛素。我们已经确定了在这些药物治疗的细胞中发生的一些变化，包括表观遗传改变和关键转录因子浓度的变化。我们将评估可能介导这些药物通过药物亲和色谱鉴定的作用的候选物质。最后，我们将继续研究控制胰岛素基因转录的erk1 /2依赖性信号事件，重点关注辅激活子p300的募集机制。这些研究将为氨基酸如何调节胰岛素的产生、稳定和释放提供新的认识，并将利用新的药理学工具来确定正常和衰竭胰岛中胰岛素产生和胰岛素转录的机制。

DESCRIPTION (provided by applicant): Diabetes mellitus is a huge health burden due to decreased quality of life and the escalating cost of treatment. In the United States alone, ~8% of the population is diabetic and nearly one-third of adults are now estimated to be at risk to develop the disease. Obesity, insulin resistance and metabolic abnormalities in liver, adipose, and muscle are important factors in disease. Yet, most of the gene loci recently found associated with type 2 diabetes encode proteins that enable insulin production from pancreatic cells. Nutrients and hormones regulate not only insulin secretion but also the capacity of cells to continue to produce insulin. In this proposal we focus on mechanisms of action of nutrients and agents that enhance insulin production in cells. The overarching goals are to elucidate mechanisms that can be manipulated to improve -cell function and overcome the physiological changes in cells that occur during prolonged hyperglycemia, contributing to inadequate insulin release. In aim 1 we will determine the functions of the taste receptor complex (T1R1/T1R3) in pancreatic cells. This dimeric G protein-coupled receptor (GPR) is involved in amino acid-sensing. This receptor, identified in gustatory neurons, binds to a variety of amino acids, but has not been studied on cells. We find that stable knockdown of T1R3 reduces insulin secretion, and insulin content, and causes events associated with autophagy. We will explore the bases for these phenotypic changes and we will also examine the underlying signaling mechanisms. In the second aim we will examine molecular mechanisms of action of small molecules that enhance beta-cell function. These molecules stimulate insulin production by cells, improve oral glucose tolerance of db/db mice, and restore insulin production by human islets in long term culture. We have identified a number of changes that take place in cells treated with these drugs, including epigenetic alterations, and changes in concentrations of key transcription factors. We will evaluate candidates that may mediate the actions of these drugs identified by drug-affinity chromatography. Finally, we will continue to investigate ERK1/2-dependent signaling events that control insulin gene transcription by focusing on mechanisms of recruitment of the coactivator p300. These studies should provide new understanding of how amino acids regulate insulin production, stability and release and will exploit a new pharmacological tool to identify mechanisms to enhance insulin production and insulin transcription in normal and failing islets.