Laboratory of Histology, Neuroanatomy and Neuropathology, Faculty of Medicine, Université Libre de Bruxelles, 808, Route de Lennik, Bldg GE, 1070, Brussels, Belgium.
Acta Neuropathol. 2012 Jan;123(1):71-84. doi: 10.1007/s00401-011-0901-4. Epub 2011 Nov 18.
Fast anterograde and retrograde axoplasmic transports in neurons rely on the activity of molecular motors and are critical for maintenance of neuronal and synaptic functions. Disturbances of axoplasmic transport have been identified in Alzheimer's disease and in animal models of this disease, but their mechanisms are not well understood. In this study we have investigated the distribution and the level of expression of kinesin light chains (KLCs) (responsible for binding of cargos during anterograde transport) and of dynein intermediate chain (DIC) (a component of the dynein complex during retrograde transport) in frontal cortex and cerebellar cortex of control subjects and Alzheimer's disease patients. By immunoblotting, we found a significant decrease in the levels of expression of KLC1 and 2 and DIC in the frontal cortex, but not in the cerebellar cortex, of Alzheimer's disease patients. A significant decrease in the levels of synaptophysin and of tubulin-β3 proteins, two neuronal markers, was also observed. KLC1 and DIC immunoreactivities did not co-localize with neurofibrillary tangles. The mean mRNA levels of KLC1, 2 and DIC were not significantly different between controls and AD patients. In SH-SY5Y neural cells, GSK-3β phosphorylated KLC1, a change associated to decreased association of KLC1 with its cargoes. Increased levels of active GSK-3β and of phosphorylated KLC1 were also observed in AD frontal cortex. We suggest that reduction of KLCs and DIC proteins in AD cortex results from both reduced expression and neuronal loss, and that these reductions and GSK-3β-mediated phosphorylation of KLC1 contribute to disturbances of axoplasmic flows and synaptic integrity in Alzheimer's disease.
神经元内快速的顺行和逆行轴浆运输依赖于分子马达的活性，对于维持神经元和突触功能至关重要。在阿尔茨海默病和这种疾病的动物模型中已经发现了轴浆运输的紊乱，但它们的机制尚不清楚。在这项研究中，我们研究了控制对象和阿尔茨海默病患者的额皮质和小脑皮质中驱动蛋白轻链（KLC）（负责顺行运输过程中货物的结合）和动力蛋白中间链（DIC）（逆行运输过程中动力蛋白复合物的组成部分）的分布和表达水平。通过免疫印迹，我们发现阿尔茨海默病患者额皮质中 KLC1 和 2 和 DIC 的表达水平显著降低，但小脑皮质中没有。还观察到突触小体蛋白和微管蛋白-β3 蛋白（两种神经元标志物）的水平显著降低。KLC1 和 DIC 免疫反应性与神经原纤维缠结不共存。KLC1、2 和 DIC 的平均 mRNA 水平在对照组和 AD 患者之间没有显著差异。在 SH-SY5Y 神经细胞中，GSK-3β 磷酸化 KLC1，这种变化与 KLC1 与其货物的结合减少有关。还观察到 AD 额皮质中活性 GSK-3β 和磷酸化 KLC1 的水平增加。我们认为，AD 皮质中 KLC 和 DIC 蛋白的减少既来自于表达减少，也来自于神经元丢失，这些减少以及 GSK-3β 介导的 KLC1 磷酸化导致了阿尔茨海默病中轴浆流动和突触完整性的紊乱。
