Downstream Regulators of Beta-Amyloid Induced Neuronal Death

我们的总体目标是确定淀粉样蛋白（A）诱导的突触丢失的分子机制， 神经元死亡不溶性A？的沉积，以及缠结的形成，突触和神经元的丧失， 老年痴呆症的症状最近在AD中发现了可溶性A？寡聚物， 这些可能与突触丧失有关。虽然关于这些因素在疾病中的作用的争论仍在继续， 重要的是要开发模型系统，以便研究这些过程。研究表明，增加A？ 诱导突触毒性，这是一个与AD认知能力下降相关的参数。我们工作中的证据 来自其他实验室的研究表明，聚集的和寡聚的A？诱导培养的神经元凋亡， 亚致死浓度的A？诱导原代神经元和脑切片中突触形态的变化。 我们的工作表明，A？诱导caspase-2和-3的激活，但只有caspase-2执行死亡。 Caspase-2及其下游靶点Bim在AD脑中增加。我们提出，在神经元中， 暴露于A <$，caspase-3的主要功能是调节突触可塑性，而不是执行细胞的功能。 死亡; caspase-2执行死亡。我们提出了一个假设，即存在剂量依赖性激活不同的 半胱天冬酶通过A？导致突触重塑、突触丢失和神经元死亡。亚致死剂量的A？ 激活caspase-3; caspase-3在这种情况下不执行死亡，但负责重塑突触， 一种响应A？的保护机制; caspase-3的活性受IAP调节。随着增加 暴露的时间或增加的水平，突触修剪变得过度，导致突触毒性 这反过来又诱导营养因子剥夺，导致进一步的突触损失，并最终激活 caspase-2和神经元死亡。致死剂量的A？激活caspase-2和caspase-3; caspase-2诱导Bim和 在执行神经元死亡时，caspase-3活性被cIAP 1抑制而不执行死亡。不同的复合体 来调节神经元中caspase-2的活性。Caspase-2激活需要RAIDD; PIDD与RAIDD复合物 以防止caspase-2激活。我们将使用初等方法来检验这些假设。 海马神经元培养物和神经变性的小鼠模型，具有以下具体目的：1.到 确定半胱天冬酶如何调节A？诱导的突触丢失。2：确定半胱天冬酶是如何 由A？和TFD调节和激活。3：确定caspase-2如何调节Bim的诱导 A治疗后。

Our overall aim is to determine the molecular mechanisms of ¿-amyloid (A¿)-induced synaptic loss and neuronal death. Deposition of insoluble A¿, together with tangle formation, loss of synapses and neurons, are hallmarks of Alzheimer¿s disease. More recently soluble A¿ oligomeric species have been found in AD and these may correlate with synaptic loss. While the debate continues about the role of each of these in the disease it is important to develop model systems where these processes can be studied. Studies show that increased A¿ induces synaptotoxicity, a parameter which correlates with cognitive decline in AD. Evidence from our work and from other laboratories shows that aggregated and oligomeric A¿ induce apoptosis in cultured neurons and that sublethal concentrations of A¿ induce changes in synapse morphology in primary neurons and brain slices. Our work shows that A¿ induces activation of caspase-2 and -3 but that only caspase-2 executes death. Caspase-2 and its downstream target Bim are increased in AD brains. We are proposing that, in neurons exposed to A¿, the main function of caspase-3 is the regulation of synaptic plasticity, not the execution of cell death; caspase-2 executes death. We propose the hypothesis that there is dose-dependent activation of different caspases by A¿ leading to synaptic remodeling, synaptic loss and neuronal death. Sublethal doses of A¿ activate caspase-3; caspase-3 in this setting does not execute death but is responsible for remodeling synapses as a protective mechanism in response to A¿; the activity of caspase-3 is modulated by IAPs. With increasing time of exposure or increasing levels of A¿, synapse pruning becomes excessive, leading to synaptotoxicity which in turn induces trophic factor deprivation leading to further synaptic loss and eventually to activation of caspase-2 and neuronal death. Lethal doses of A¿ activate caspase-2 and caspase-3; caspase-2 induces Bim and executes the neuron, caspase-3 activity is inhibited from executing death by cIAP1. Different complexes serve to regulate caspase-2 activity in neurons. Caspase-2 activation requires RAIDD; PIDD complexes with RAIDD in healthy neurons to prevent caspase-2 activation. We will examine these hypotheses using primary hippocampal neuron cultures and mouse models of neurodegeneration, with the following specific aims: 1. To determine how caspases regulate synaptic loss induced by A¿. 2: To determine how caspases are regulated and activated by A¿ and TFD. 3: To determine how caspase-2 regulates the induction of Bim after A¿ treatment.