Nelson P T, Marton L, Saper C B
Department of Pharmacological and Physiological Sciences, University of Chicago, IL.
Brain Res. 1993 Jan 15;600(2):285-97. doi: 10.1016/0006-8993(93)91385-6.
Alz-50 is a monoclonal antibody raised against ventral forebrain tissue from patients with Alzheimer's disease (AD). It was originally believed that the antigen recognized by Alz-50 was only found in degenerating neurons. However, recent studies indicate that Alz-50 stains neurons in a limited but specific distribution in normal brains throughout life. As the antigen recognized by Alz-50 in normal brains may give some insight into the AD degenerative process, we characterized Alz-50 staining in the normal ovine striatum using immunoblots and immunocytochemistry at the light and electron microscope levels. We then compared the Alz-50 staining pattern with those of NADPH diaphorase histochemistry and immunocytochemistry using antisera against several neuropeptides, Alzheimer-related proteins, and heat-shock proteins. Western blot analysis indicated that the epitope recognized by Alz-50 in the normal sheep brain is on the microtubule-associated protein tau, and preadsorbing Alz-50 with a peptide corresponding to the amino terminus of the tau molecule eliminated staining. Alz-50 labeled a single population of cells in the ovine striatum, the medium aspiny neurons. At the light microscope level, the granular staining pattern closely resembled Alz-50 immunoreactive neurons in the normal human striatum and in cells undergoing early degeneration in AD. Alz-50 immunoreactive neurons stained immunocytochemically with antisera against somatostatin, neuropeptide Y, and histochemically for NADPH diaphorase. These cells were morphologically characterized by smooth dendrites, elaborate local axonal plexuses, and indented nuclei with filamentous inclusions. Ultrastructurally, Alz-50 immunodecorated ribosomes and membranous structures (e.g. vesicles, endoplasmic reticulum), and many boutons which contained Alz-50-positive synaptic vesicles. None of the antisera against other Alzheimer-related proteins, including paired helical filament protein, ubiquitin, beta-amyloid protein, or heat-shock proteins specifically stained the population of cells labelled by Alz-50. Other tau antisera also did not specifically stain these cells. We conclude that Alz-50 recognizes an amino terminal epitope that is exposed on tau proteins within a single, discrete population of neurons in the normal sheep striatum. The presence of this epitope in a normal cell population raises the possibility that the early stages of AD degeneration may involve the activation of a normal cellular pathway that modifies the tau molecule.
Alz-50是一种针对阿尔茨海默病（AD）患者腹侧前脑组织产生的单克隆抗体。最初人们认为Alz-50识别的抗原仅存在于退化的神经元中。然而，最近的研究表明，Alz-50在正常大脑中终其一生都以有限但特定的分布模式对神经元进行染色。由于Alz-50在正常大脑中识别的抗原可能为AD的退化过程提供一些线索，我们利用免疫印迹法以及光镜和电镜水平的免疫细胞化学方法，对正常绵羊纹状体中的Alz-50染色进行了表征。然后，我们将Alz-50的染色模式与用抗几种神经肽、阿尔茨海默病相关蛋白和热休克蛋白的抗血清进行的NADPH黄递酶组织化学和免疫细胞化学的染色模式进行了比较。蛋白质免疫印迹分析表明，Alz-50在正常绵羊大脑中识别的表位位于微管相关蛋白tau上，用与tau分子氨基末端对应的肽预吸附Alz-50可消除染色。Alz-50标记了绵羊纹状体中的单一细胞群，即中等无棘神经元。在光镜水平上，颗粒状染色模式与正常人类纹状体以及AD中处于早期退化阶段的细胞中的Alz-50免疫反应性神经元非常相似。Alz-50免疫反应性神经元用抗生长抑素、神经肽Y的抗血清进行免疫细胞化学染色，并对NADPH黄递酶进行组织化学染色。这些细胞在形态上的特征是具有光滑的树突、精细的局部轴突丛以及带有丝状内含物的凹陷细胞核。在超微结构上，Alz-50免疫标记核糖体和膜性结构（如囊泡、内质网），以及许多含有Alz-50阳性突触小泡的终扣。针对其他阿尔茨海默病相关蛋白的抗血清，包括成对螺旋丝蛋白、泛素、β淀粉样蛋白或热休克蛋白，均未特异性地对Alz-50标记的细胞群进行染色。其他tau抗血清也未特异性地对这些细胞进行染色。我们得出结论，Alz-50识别正常绵羊纹状体中单个离散神经元群内tau蛋白上暴露的氨基末端表位。在正常细胞群中存在这种表位增加了AD退化早期阶段可能涉及修饰tau分子的正常细胞途径激活的可能性。
