Receptor-regulated Calcium Entry in Exocrine Secretion

描述（由申请人提供）：细胞内Ca2+离子浓度的增加是多种激素和神经递质作用于磷脂酶C （PLC）偶联受体产生的细胞信号的主要组成部分。这些Ca2+信号的一般特征是细胞外Ca2+的进入增强。我们的研究重点是了解这种Ca2+进入的性质，及其在整体细胞内信号传导机制中的作用。直到最近，这种进入被认为只涉及所谓的存储操作Ca2+通道（或SOC通道），其门控依赖于细胞内Ca2+存储的消耗。然而，近年来，我们和其他人已经确定了一种新的花生四烯酸依赖途径，用于激动剂激活的Ca2+进入，这与储存操作的途径完全不同。我们现在已经在全细胞水平（以及最近在单通道水平）表征了负责的通道（ARC通道，为花生四烯酮调节的Ca2+通道），并确定了它们在各种不同细胞类型中的存在。重要的是，我们过去三(3)年的研究表明，正是这些ARC通道，而不是SOC通道，提供了在生理相关刺激水平下Ca2+增强进入的主要途径。因此，了解这些新渠道的调节和功能至关重要，并构成了当前建议的基础。在目的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。目的2解决了通过磷酸化和相关激酶对通道进行调节的潜在机制。Aim 3探讨了ARC通道在整个细胞Ca2+信号传导中发挥的独特作用，既可以调节信号本身，也可以通过进入ARC通道的Ca2+对特定效应器的直接影响。尽管这种新通道的分子特性仍然未知，但很明显，其关键特征的表征-它的性质，它的调节和它的作用-对我们理解细胞中PLC依赖的Ca2+信号传导具有关键意义。

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.