Vincent I, Jicha G, Rosado M, Dickson D W
Departments of Pathology and Neurology, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
J Neurosci. 1997 May 15;17(10):3588-98. doi: 10.1523/JNEUROSCI.17-10-03588.1997.
We have shown previously that M-phase phospho-epitopes accumulate in neuronal tau proteins incorporated into the hallmark neurofibrillary tangles (NFT) of Alzheimer's disease (AD). In M phase, the epitopes are produced by cdc2/cyclin B1 kinase by a highly conserved mechanism believed to be quiescent in terminally differentiated neurons of adult brain. To determine whether an M-phase mechanism is possible in AD neurons, we first investigated the presence of cdc2 and cyclin B1 in AD. Both proteins were enriched in neurons with NFT and in neurons susceptible to NFT. An antibody specific for catalytically active cdc2 stained numerous NFT-containing neurons in AD but did not react with normal neurons. Double-labeling studies showed that active cdc2 and cyclin B1 coexist in AD neurons and co-localize with AD-specific mitotic phospho-epitopes. Mitotic kinase purified from AD and normal brain, using the yeast p13suc1 protein as affinity ligand, showed higher histone H1 phosphorylation activity in AD. Accordingly, the levels of cdc2 and cyclin B1 in p13suc1 fractions from AD were higher than normal. Consistent with a physiological relationship between NFT and mitotic kinase, NFT proteins co-purified with and became phosphorylated by the p13suc1-bound kinase in vitro. Furthermore, cdc2/cyclin B1 is the only one of several proline-directed kinases that created the TG/MC mitotic phospho-epitopes in recombinant tau in vitro. These findings suggest that aberrantly reexpressed cdc2/cyclin B1 in NFT-bearing neurons in AD brain contributes to the generation of M-phase phospho-epitopes in NFT.
我们之前已经表明，M期磷酸化表位会在纳入阿尔茨海默病（AD）标志性神经原纤维缠结（NFT）的神经元tau蛋白中积累。在M期，这些表位由cdc2/细胞周期蛋白B1激酶通过一种高度保守的机制产生，这种机制被认为在成人大脑的终末分化神经元中处于静止状态。为了确定AD神经元中是否可能存在M期机制，我们首先研究了AD中cdc2和细胞周期蛋白B1的存在情况。这两种蛋白在含有NFT的神经元以及易形成NFT的神经元中均有富集。一种针对具有催化活性的cdc2的抗体在AD中可对众多含有NFT的神经元进行染色，但不与正常神经元发生反应。双重标记研究表明，活性cdc2和细胞周期蛋白B1在AD神经元中共存，并与AD特异性有丝分裂磷酸化表位共定位。利用酵母p13suc1蛋白作为亲和配体从AD和正常大脑中纯化得到的有丝分裂激酶，显示出AD中组蛋白H1磷酸化活性更高。因此，来自AD的p13suc1组分中cdc2和细胞周期蛋白B1的水平高于正常水平。与NFT和有丝分裂激酶之间的生理关系一致，NFT蛋白在体外与p13suc1结合的激酶共纯化，并被其磷酸化。此外，cdc2/细胞周期蛋白B1是几种脯氨酸定向激酶中唯一能在体外重组tau中产生TG/MC有丝分裂磷酸化表位的激酶。这些发现表明，AD大脑中含有NFT的神经元中异常重新表达的cdc2/细胞周期蛋白B1有助于NFT中M期磷酸化表位的产生。
