Novel Calcium Release Mechanism Regulates Dendritic Cell Function

描述（由申请人提供）：树突状细胞（DC）是免疫系统的多能调节剂。许多关键的DC功能涉及钙（Ca 2+）信号传导。Ca 2+是最通用的真核细胞内信使，介导对细胞生命重要的许多过程的调节。DC和许多其他免疫细胞类型中的Ca 2+水平在静息状态期间以及在激活期间通过多种机制受到严格调节。趋化因子受体刺激增加细胞内Ca 2+浓度（[Ca 2 +]i）和DC的趋化性。尽管我们对淋巴细胞中Ca 2+信号传导的理解取得了重要进展，但参与DCs细胞内Ca 2+形成的分子参与者仍有待表征。目前的范例表明，DC胞质Ca 2+水平的增加是由内质网（ER）Ca 2+储存释放和/或通过质膜上储存操作的Ca 2+通道的开放引起的细胞外Ca 2+流入引起的。我们提出了一种新的钙释放机制，在DC中，它通过一个钙通道表达的溶酶体室，我们假设这条途径是必不可少的钙依赖性DC功能。支持我们的提议的初步数据显示：i）功能性Ca 2+渗透性美拉汀相关瞬时受体电位通道（TRPM 2）在DC的内溶酶体隔室中的唯一定位。ii）腺苷二磷酸核糖（ADPR）和趋化因子均诱导TRPM 2介导的DC中的Ca 2+信号。iii）TRPM 2通道充当DC中的Ca 2+释放通道。iv）TRPM 2缺陷型DC表现出对趋化因子的趋化性应答受损。V）TRPM 2缺陷型小鼠在感染后引起减少的炎症募集。基于这些数据，我们假设：TRPM 2作为细胞内溶酶体相关的钙释放通道，调节DC中的Ca 2+依赖性过程。为了严格检验我们的假设，我们提出了以下具体目标：目标1。识别通过TRPM 2通道激活Ca 2+释放的机制，并阐明该途径如何影响DC Ca 2+依赖性功能。目标2.使用尿路感染小鼠模型，确定TRPM 2介导的Ca 2+信号在炎症、免疫和细胞炎症浸润至粘膜期间在DC中的特定作用。从这个建议的结果将提供深入了解TRPM 2通道的细胞内功能如何影响钙离子介导的信号转导途径，发挥中央调节作用，在DC响应。这些研究的完成将揭示新的药理学靶点（ADPR和/或TRPM 2）用于操纵DC的Ca 2+反应和功能的效用，并将进一步促进慢性炎症或感染性疾病的新治疗策略的设计，其中DC可能发挥重要的致病作用。

DESCRIPTION (provided by applicant): Dendritic cells (DCs) are multi-potent regulators of the immune system. Many critical DC functions involve calcium (Ca2+) signaling. Ca2+ is the most versatile eukaryotic intracellular messenger that mediates regulation of many processes important to cell life. Ca2+ levels in DCs and many other immune cell types are tightly regulated through multiple mechanisms during the resting state as well as during activation. Chemokine receptor stimulation increases intracellular Ca2+ concentration ([Ca2+]i) and chemotaxis in DCs. Despite important advances in our understanding of Ca2+ signaling in lymphocytes, the molecular players involved in shaping intracellular Ca2+ in DCs remain to be characterized. The current paradigm states that increases in DC cytosolic Ca2+ levels are caused by release from endoplasmic reticulum (ER) Ca2+ stores and/or via influx of extracellular Ca2+ by opening of store-operated Ca2+ channels at the plasma membrane. We propose a novel Ca2+ release mechanism in DCs, which operates via a Ca2+ channel expressed on lysosomal compartments and, we postulate this pathway is essential for Ca2+-dependent DC functions. Preliminary data that support our proposal show: i) Exclusive localization of functional Ca2+-permeant melastatin-related transient receptor potential channel (TRPM2) in endolysosomal compartments of DCs. ii) Both adenosine diphosphoribose (ADPR) and chemokines induce TRPM2 mediated Ca2+ signals in DCs, iii) TRPM2 channel acts as a Ca2+ release channel in DCs. iv) TRPM2-deficient DCs exhibit impaired chemotactic responses to chemokines. v) TRPM2-deficient mice elicit reduced inflammatory recruitment upon infection. Based upon these data, we hypothesize that: TRPM2 functions as an intracellular lysosome- associated calcium release channel that regulates Ca2+-dependent processes in DCs. To critically test our hypothesis, we propose the following specific aims: Aim 1. Identify mechanisms of activation of Ca2+ release via TRPM2 channel, and elucidate how this pathway impacts on DC Ca2+-dependent functions. Aim 2. Define the specific roles for TRPM2-mediated Ca2+ signaling in DCs during inflammation, immunization and cellular inflammatory infiltration to the mucosa using a mouse model of urinary tract infection. The findings from this proposal will provide insights into how the intracellular function of TRPM2 channel affects Ca2+-mediated signal transduction pathways that play a central regulatory role during DC responses. The completion of these studies will unveil the utility of new pharmacological targets (ADPR and/or TRPM2) for manipulation of DCs' Ca2+responses and functions, and will further facilitate the design of new therapeutic strategies for chronic inflammatory or infectious diseases, where DCs may play important pathogenic roles.