Presenilins and neuronal calcium dyshomeostasis

描述（由申请人提供）：该项目的长期目标是了解神经元钙（Ca2+）信号在阿尔茨海默病（AD）发病机制中的重要性。早老素是一种定位于内质网的跨膜蛋白。早老素错义突变占家族性AD病例的40%。早老素中的许多FAD突变也与内质网（ER）钙（Ca2+）信号传导异常有关。目前研究的主要目的是了解早老素突变、神经元ER Ca2+信号失调和AD中突触丧失和功能障碍之间的联系。具体来说，我们将重点测试一个新的假设，即内质膜Ca2+信号的缺陷可能导致被广泛认为是记忆存储的物理单位的“蘑菇棘”的不稳定，通过攻击这些目标：1. 探讨突触后储存操作钙（SOC）进入通路下调在AD成熟突触棘丢失中的重要性。我们的初步数据表明，神经元ER Ca2+水平的增加导致神经元储存操作的Ca2+进入途径（nSOC）的代偿性下调。我们发现nSOC的下调是由于nSOC的主要调控因子STIM2蛋白的表达减少。我们认为突触nSOC的减少会导致蘑菇棘的不稳定和最终消除，从而导致FAD中的记忆丧失和大脑老化。这一假设将在PS1-FAD小鼠模型和STIM2条件敲除小鼠模型中得到验证。2. 探讨阿尔茨海默病中LTP诱导的成熟突触棘失稳与神经元活动失调之间的关系。我们的初步数据表明，适当的神经元活动模式对于维持成熟的“蘑菇刺”至关重要。我们进一步发现异常的ER Ca2+信号导致PS1-FAD神经元的这种模式被破坏。我们将进行一系列实验，旨在剖析AD神经元中ER Ca2+稳态、神经元活动模式和蘑菇棘稳定性之间的联系。我们将评估细胞内Ca2+储存和Ca2+激活钾通道的SK家族在这一过程中的关键作用。3. 分析淀粉样蛋白和钙通路在AD发病机制中的相互作用。Abeta42寡聚物通过多种途径影响神经元Ca2+信号传导和神经元活动。在这个目的中，我们将研究在SA1和SA2中探索的一些Ca2+相关靶点和途径是否也适用于淀粉样蛋白突触毒性模型。这些实验将使用Abeta42突触毒性体外模型和新生成的APP-KI AD小鼠模型进行。

DESCRIPTION (provided by applicant): 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 criticl 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. Abeta42 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 Abeta42 synaptotoxicity and with recently generated APP-KI mouse model of AD.