Taste receptor signaling in beta cells and role in postprandial insulin secretion

描述（由申请人提供）：我们最近发现胰腺β细胞表达一个信号系统，与传统的葡萄糖诱导代谢途径互补，参与刺激胰岛素释放。传统上参与舌头味觉感知的味觉受体及其信号机制也在胰岛中表达。我们发现，TR激动剂刺激原发胰岛的胰岛素分泌，这些反应可以通过拮抗剂和靶向TR信号成分的敲除策略来阻断。这一建议解决了这些发现的生理学相关性。我们假设β细胞中的TR机制是一个重要的感觉系统，它根据摄入的营养物质（如单糖和氨基酸）调节胰岛素分泌。我们认为β细胞中的TR信号通过调节葡萄糖刺激胰岛素分泌（GSIS）的作用，有助于餐后葡萄糖稳态。我们的实验计划评估了TR在β细胞中的作用，并阐明了生理TR激动剂诱导的下游信号通路。我们将使用T1R3敲除（KO）小鼠来研究TRs在体外调节胰岛素分泌和体内葡萄糖稳态中的作用。我们将在静态和灌注实验中比较野生型和T1R3 KO胰岛的体外GSIS，并评估β细胞应激下T1R3 KO小鼠的体内代谢表型。我们还将确定餐后甜味营养素通过TRs作用，以增强胰岛素释放。最后，我们将通过使用PLC-生物传感器（PHPLC4-GFP）评估PLC的激活来阐明TR信号通路，并使用特定的ER钙生物传感器（D1ER cameleon）分析ER钙的动态变化。这些研究结果将极大地增强我们对胰岛素释放调控的理解，并证实β细胞中存在的TRs介导的一种新的调控途径。

DESCRIPTION (provided by applicant): We recently discovered that pancreatic beta-cells express a signaling system complementary to the traditional glucose-induced metabolic pathway that participates in the stimulation of insulin release. Taste receptors (TRs) and their signaling machinery that are traditionally involved in taste perception on the tongue are also expressed in pancreatic islets. We found that TR agonists stimulate insulin secretion in primary pancreatic islets, and that these responses can be blocked using antagonists and knock out strategies targeting TR signaling components. This proposal addresses the physiological relevance of these findings. We hypothesize that the TR machinery in beta-cells is an important sensory system that modulates insulin secretion in response to ingested nutrients, such as monosaccharides and amino acids. We propose that TR signaling in beta-cells contributes to postprandial glucose homeostasis by modulating the effects of glucose-stimulated insulin secretion (GSIS). Our experimental plan evaluates the role of TRs in beta-cells, and elucidates the downstream signaling pathway induced by physiological TR agonists. We will use T1R3 knock out (KO) mice to investigate the role of TRs in the regulation of insulin secretion in vitro and glucose homeostasis in vivo. We will compare in vitro GSIS between wild type and T1R3 KO islets in static and perifusion experiments, and assess the in vivo metabolic phenotype of T1R3 KO mice subjected to beta-cell stress. We will also identify postprandial sweet taste nutrients that act through TRs to potentiate insulin release. Finally, we will elucidate the TR signaling pathway by evaluating the activation of PLC using a PLC-biosensor (PHPLC4-GFP), and analyze dynamic changes in ER calcium using a specific ER calcium biosensor (D1ER cameleon). Results from these studies will greatly enhance our understanding of the regulation of insulin release and confirm a novel regulatory pathway mediated by TRs present in beta-cells.