REGULATION OF ALZHEIMER AMYLOID GENERATION BY NEURONS

阿尔茨海默病(AD)的一个不变特征是在脆弱的脑区沉积β-淀粉样蛋白(Abeta)。Aβ是由淀粉样前体蛋白(βAPP)的受控裂解形成的。β-APP的代谢主要是通过对转染人β-APP克隆细胞系的研究来阐明的。然而，由于神经元是AD中Abeta最丰富的来源，也是AD中受影响最严重的细胞类型，因此研究神经元中的βAPP代谢和Abeta的生成对于阐明AD患者脑内发生的生物学过程具有重要意义。我们的目的是研究啮齿动物原代神经元培养中Abeta和BetaAPP的内源性加工和细胞内转运。此外，我们正在调查是否像在细胞系中观察到的那样，在神经元培养中对BetaAPP处理途径的相对利用进行了类似的调节。已知的βAPP代谢调节因子，如蛋白质磷酸化和第一信使神经递质信号转导系统，以及性腺激素治疗，正在这些皮质培养中进行评估。利用放射测序和代谢标记-质谱法，我们最近发现变异型AbetaGlu11多肽是神经元分泌的主要Abeta物种。此外，我们还发现，用17β-雌二醇或蛋白磷酸酶抑制剂治疗神经元在减少淀粉样变性Abeta多肽的分泌方面特别有效。阐明β-APP和A-β在神经元中代谢的分子和细胞过程将为寻求合理的AD治疗策略提供重要信息。

Deposition of beta-amyloid (Abeta) in vulnerable brain regions is an invariable feature of Alzheimer's disease (AD). Abeta is formed by the regulated cleavage of the amyloid precursor protein (betaAPP). The metabolism of betaAPP has been elucidated mainly by studies in clonal cell lines transfected with human betaAPP. However, since neurons are the most abundant source of Abeta and are the most affected cell-type in AD, the study of betaAPP metabolism and Abeta generation in neurons will be important to elucidate the biological processes occuring in the brain of those afflicted by AD. Our objective is to study the endogenous processing and intracellular trafficking of Abeta and betaAPP in rodent primary neuronal cultures. Furthermore, we are investigating whether the relative utilization of processing pathways for betaAPP are regulated in a similar manner in neuronal cultures as has been observed in cell lines. Known regulators of betaAPP metabolism, such as protein phosphorylation and first messenger neurotransmitter signal transduction systems, and gonadal hormone treatment are being assessed in these cortical cultures. Using radiosequencing and metabolic labeling- mass spectrometry, we have recently discovered that variant AbetaGlu11 peptides are principal Abeta species secreted by neurons. Moreover, we have found that treatment of neurons with 17beta-estradiol or protein phosphatase inhibitors are especially effective at reducing secretion of amyloidogenic Abeta peptides. The elucidation of the molecular and cellular processes governing the metabolism of betaAPP and Abeta in neurons will provide important information in the pursuit of rational therapeutic strategies for AD.