Downstream Regulators of Beta-Amyloid Induced Neuronal Death

我们的总体目标是确定-淀粉样蛋白(A_)诱导的突触丢失和神经元死亡的分子机制。不溶性A_2的沉积，以及缠结形成、突触和神经元的丧失，是阿尔茨海默病的特征。最近在AD中发现了可溶性A_寡聚体物种，它们可能与突触丢失有关。虽然关于这些过程中的每一个在疾病中的作用的争论仍在继续，但重要的是开发可以研究这些过程的模型系统。研究表明，增加的A_2可诱导突触毒性，这一参数与AD的认知功能减退有关。我们的工作和其他实验室的证据表明，聚集性和寡聚体A_2诱导培养的神经元凋亡，亚致死浓度的A_1诱导原代神经元和脑片突触形态的改变。我们的工作表明，A_2诱导caspase-2和-3的激活，但只有caspase-2执行死亡。Caspase-2及其下游靶标Bim和Caspase-3在AD脑内表达增加。我们认为，在暴露于A_2的神经元中，caspase-3的主要功能是调节突触可塑性，而不是执行细胞死亡；caspase-2执行死亡。我们提出的假设是，A_1对不同的caspase有剂量依赖性的激活，导致突触重构、突触丢失和神经元死亡。亚致死剂量的A_激活caspase-3；在这种情况下，caspase-3不会导致死亡，但负责重塑突触，作为对A_的保护机制；caspase-3的活性受IAP的调节。随着暴露时间的延长或A_2水平的增加，突触修剪过度，导致突触毒性，进而导致营养因子剥夺，导致进一步的突触丢失，最终导致caspase-2激活和神经元死亡。致死剂量A激活caspase-2和caspase-3；caspase-2诱导BIM并执行神经元，caspase-3活性被cIAP1抑制执行死亡。不同的复合体可以调节神经元中caspase-2的活性。Caspase-2的激活需要RAIDD；在健康神经元中，PIDD与RAIDD形成复合体，以阻止caspase-2的激活。我们将使用原代海马神经元培养和小鼠神经退行性变模型来检验这些假说，具体目的如下： 1.探讨Caspase-3和IAP是否参与了A_1诱导的脊髓损伤。 2.2：研究A_2和TFD对caspase-2的调控和激活作用。3：检测caspase-2对Bim表达的影响。

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, and caspase-3 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 if caspase-3 and IAPs mediate spine changes induced by A_. 2. 2: To determine how caspase-2 is regulated and activated by A_ and TFD. 3: To determine how caspase-2 induces of Bim expression.