Receptor-regulated Calcium Entry in Exocrine Secretion

描述(申请人提供)：细胞内钙离子浓度的增加是由多种激素和神经递质作用于与磷脂酶C(PLC)偶联的受体所产生的细胞信号的主要成分。这些钙信号的一个普遍特征是细胞外钙离子进入增强。我们研究的重点是了解这种钙离子进入的性质，以及它在整个细胞内信号机制中的作用(S)。直到最近，这种进入被认为只涉及所谓的存储操作的钙通道(或SOC通道)，其门控依赖于细胞内钙存储的耗尽。然而，近年来，我们和其他人发现了一种新的花生四烯酸依赖的激动剂激活的钙进入途径，这与商店操作的途径完全不同。我们现在已经在全细胞水平上表征了负责的通道(ARC通道，对于花生四烯酸调节的钙通道)(最近，在单通道水平上)，并鉴定了它们在各种不同类型的细胞中的存在。重要的是，我们在过去三(3)年的研究表明，正是这些ARC通道，而不是SOC通道，为生理相关刺激水平上的钙离子增强进入提供了主要途径。因此，了解这些新渠道的规则和功能至关重要，并构成当前提案的基础。在目标1中，我们研究了花生四烯酸在单通道水平激活ARC通道的机制。目标2阐述了通过磷酸化和相关的激酶对通道进行调节的潜在机制。目的3探讨ARC通道在整个细胞内钙信号中所起的独特作用，这既是通过调节信号本身，也是通过钙离子进入ARC通道对特定效应分子的直接影响。尽管这一新通道的分子特性尚不清楚，但很明显，它的主要特征--它的性质、调节和作用--的表征对于我们理解细胞内PLC依赖的钙信号具有至关重要的意义。

DESCRIPTION (provided by applicant): Increases in the cytosolic concentration of Ca2+ ions represent a major component of the cellular signals generated by a variety of hormones and neurotransmitters acting on receptors coupled to phospholipase C (PLC). A general feature of these Ca2+ signals is an enhanced entry of extracellular Ca2+. The focus of our research is to understand the nature of this Ca2+ entry, and its role(s) in the overall intracellular signaling mechanisms. Until recently, such entry was thought to exclusively involve so-called store-operated Ca2+ channels (or SOC channels) whose gating was dependent on the depletion of intracellular Ca2+ stores. However, in recent years we, and others, have identified a novel arachidonic acid-dependent pathway for agonist-activated Ca2+ entry that is entirely distinct from the store-operated pathway. We have now characterized the channels responsible (ARC channels, for Arachidonate-Regulated Ca2+ channels) at the whole-cell level, (and, more recently, at the single channels level), and have identified their presence in a variety of different cell types. Importantly, our studies over the past three (3) years have demonstrated that it is these ARC channels, and not the SOC channels, that provide the predominant route for the enhanced entry of Ca2+ seen at physiologically relevant levels of stimulation. Understanding the regulation and function of these novel channels is, therefore, of key importance and forms the basis of the current proposal. In Aim 1, we examine the mechanism by which arachidonic acid activates the ARC channels at the single channel level. Aim 2 addresses the mechanisms underlying the demonstrated regulation of the channels by phosphorylation and the kinases responsible. Aim 3 explores the unique roles that the ARC channels play in overall cellular Ca2+ signaling, both by modulating the signals themselves, as well as by a direct influence on specific effectors by the Ca2+ entering the ARC channels. Although the molecular identity of this novel channel remains unknown, it is clear that the characterization of its key features - its properties, its regulation, and its roles - is of critical significance to our understanding of PLC dependent Ca2+ signaling in cells.