Presenilins and neuronal calcium dyshomeostasis

摘要 该项目广泛的、长期的目标是了解神经元钙(钙)的重要性。 阿尔茨海默病(AD)发病机制的信号转导。早老素是一种跨膜蛋白，定位于 内质网(ER)。早老素错义突变占家族性AD(FAD)病例的40%。 早老素的许多FAD突变也与内质网(ER)钙异常有关 (Ca2+)信令。目前这项提议的主要目的是了解基因突变之间的联系 阿尔茨海默病中的早老素、神经元内质网钙信号的失调以及突触丢失和功能障碍。具体来说， 我们将重点检验这一新的假设，即内质网钙信号的缺陷可能导致细胞内钙离子的不稳定 “蘑菇刺”被广泛认为是记忆存储的物理单位，通过攻击这些目标：。 1.探讨突触后钙离子通道的重要性 阿尔茨海默病成熟突触棘突缺失的下调。 我们的初步数据表明，神经元内质网钙离子水平的增加导致代偿性 下调神经元库操控的钙内流途径(NSOC)。我们发现， NSOC的下调是由于nSOC的主要调节因子STIM2蛋白表达减少所致。 我们认为，突触nSOC的减少会导致不稳定，并最终消除蘑菇 脊椎，导致失忆和大脑老化。这一假设将在实验中得到验证。 采用PS1-FAD小鼠模型和STIM2条件性基因敲除小鼠模型。 2.探讨神经元活动失调与LTP失稳的关系。 在AD组诱导成熟的突触棘突。 我们的初步数据表明，适当的神经元活动模式对维持成熟至关重要。 “蘑菇刺”。我们进一步发现，异常的内质网钙信号导致这一模式的破坏 在PS1-FAD神经元中。我们将进行一系列实验，旨在剖析内质网之间的联系 阿尔茨海默病神经元内钙稳态、神经元活动模式和蘑菇棘的稳定性。我们将评估 在这一过程中，细胞内钙库和SK家族的钙激活钾通道起着至关重要的作用。 3.分析淀粉样蛋白与钙信号通路在AD发病机制中的相互作用。 A42寡聚体通过多种途径影响神经元钙信号转导和神经元活动。为了实现这一目标，我们 将研究在SA1和SA2中探索的一些与钙相关的靶点和途径是否也适用于 淀粉样突触毒性模型。这些实验将在A42的体外模型上进行 突触毒性和最近产生的AD的APP-KI小鼠模型。

ABSTRACT The broad, long-term objective of the project is to understand the importance of neuronal calcium (Ca2+) signaling in pathogenesis of Alzheimer's disease (AD). Presenilins are transmembrane proteins localized to endoplasmic reticulum (ER). Missense mutations in presenilins account for 40% of familial AD (FAD) cases. Many FAD mutations in presenilins have been also linked to abnormal endoplasmic reticulum (ER) calcium (Ca2+) signaling. The main aim of the current proposal is to understand the connection between mutations in presenilins, dysregulation of neuronal ER Ca2+ signaling and synaptic loss and dysfunction in AD. Specifically, we will focus on testing the novel hypothesis that defects in ER Ca2+ signaling may lead to destabilization of "mushroom spines" widely considered to be physical units for memory storage by attacking these aims:. 1. To investigate the importance of postsynaptic store-operated calcium (SOC) entry pathway downregulation in loss of mature synaptic spines in AD. Our preliminary data suggest that the increase in neuronal ER Ca2+ levels leads to a compensatory downregulation of neuronal store-operated Ca2+ entry pathway (nSOC). We discovered that the downregulation of nSOC occurs due to reduced expression of STIM2 protein, a master regulator of nSOC. We propose that reduction in synaptic nSOC causes destabilization and eventual elimination of mushroom spines, leading to loss of memories in FAD and aging brains. This hypothesis will be tested in experiments with PS1-FAD mouse model and STIM2 conditional knockout mouse model. 2. To investigate the connection between dysregulation of neuronal activity and destabilization of LTP- induced mature synaptic spines in AD. Our preliminary data indicate that appropriate pattern of neuronal activity is critical for maintenance of mature "mushroom spines". We further discovered that abnormal ER Ca2+ signaling causes disruption of this pattern in PS1-FAD neurons. We will perform a series of experiments aimed at dissecting the connection between ER Ca2+ homeostasis, neuronal activity pattern and stability of mushroom spines in AD neurons. We will evaluate a crucial role of intracellular Ca2+ stores and SK family of Ca2+-activated potassium channels in this process. 3. To analyze the cross-talk of amyloid and calcium pathways for AD pathogenesis. A 42 oligomers influence neuronal Ca2+ signaling and neuronal activity via variety of pathways. In this aim we will investigate if some of the Ca2+-related targets and pathways explored in SA1 and SA2 may also apply to models of amyloid synaptotoxicity. These experiments will be performed with in vitro model of A 42 synaptotoxicity and with recently generated APP-KI mouse model of AD.