Dynamic Interactions of IP3 Receptor Ligands

描述（申请人的描述） 细胞内钙（Ca）是一种关键的细胞信使，它触发了多种 细胞过程。它可以从细胞外介质进入细胞质 或者它可以通过至少两种类型的 通道：肌醇1，4，5-三磷酸受体（InsP 3R）和ryanodine 受体（RyR）。该提议的假设是，lnsP 3R的控制 通过Ca和lnsP 3的作用，可以在受体上调节Ca的释放。 亚细胞水平。这一假设将使用生物物理， 生物化学和分子生物学技术。具体的长期目标 这个项目是为了了解如何lnsP 3门控通道的功能， 细胞调节通道以优化细胞反应，以及如何调节 在病理生理状态下发生改变。 在所提出的实验中，我们将研究Ca和 InsP 3在I型InsP 3R调节中的作用。通道的Ca依赖性 活性是InsP 3浓度的函数。在低浓度的 InsP 3 Ca既能激活又能抑制通道活性，而在高浓度时， 浓度的InsP_3时，Ca的抑制作用减弱。在这项提案中， 有两个模型被提出来解释这种复杂的相互作用 将检查Ca和InsP 3之间的关系。第一个模型表明， 活性取决于InsP 3和Ca结合的动力学和顺序。的 第二个模型表明，lnsP 3.结合到最近确定的低亲和力 I型InsP 3R的位点对于持续的通道活性是必需的。第一、 模型将通过表征以下单通道特性进行测试： InsP 3R的正常和突变形式。然后， 将在完整细胞中研究单通道特性。我们的工作 假设表明，这两个模型的组成部分将是重要的解释 通道功能确定控制这些的分子机制 通道将有助于理解各种各样的过程， 平滑肌收缩和运动学习，并可能提供见解， 诸如高血压和共济失调的病症，涉及 这个通道的活动异常。

DESCRIPTION (applicant's description) Intracellular calcium (Ca) is a key cellular messenger that triggers a variety of cellular processes. It can enter the cytosol from the extracellular medium or it can be released from intracellular stores via at least two types of channel: the inositol 1,4,5-trisphosphate receptor (InsP3R) and the ryanodine receptor (RyR). The hypothesis of this proposal is that control of the lnsP3R by Ca and lnsP3 allows Ca release from the receptor to be regulated at the subcellular level. This hypothesis will be addressed using biophysical, biochemical and molecular biological techniques. Specific long-term goals of this project are to understand how the lnsP3-gated channel functions, how the cell regulates the channel to optimize cellular responses, and how regulation is altered in pathophysiological Situations. In the proposed experiments, we will investigate the interaction Of Ca and lnsP3 in the regulation of the type I lnsP3R. The Ca dependence of channel activity is a function of the lnsP3 concentration. At low concentrations of lnsP3 Ca can both activate and inhibit channel activity whereas at high concentrations of lnsP3 the inhibition by Ca is decreased. In this proposal the two models that have been put forward to explain this complex interaction between Ca and lnsP3 will be examined. The first model suggests that channel activity depends upon the kinetics and order of binding of lnsP3and Ca. The second model suggests that lnsP3.binding to a recently identified low affinity site of the type I lnsP3R is necessary for sustained channel activity. First, the models will be tested by characterizing the single channel properties of normal and mutant forms of the lnsP3R. Then, the functional consequences of the single channel properties will be investigated in intact cells. Our working hypothesis suggests that components of both models will be important to explain channel function. Identification of the molecular mechanisms controlling these channels will assist in the understanding of processes as diverse as secretion, smooth muscle contraction, and motor learning and may provide insights into conditions such as hypertension and ataxia, processes that involve abnormalities in the activity of this channel.