Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Ciencias, Universidad de Extremadura and Instituto Universitario de Biomarcadores de Patologías Moleculares, Universidad de Extremadura, Badajoz 06006, Spain.
Neuropharmacology. 2018 Sep 1;139:163-172. doi: 10.1016/j.neuropharm.2018.07.012. Epub 2018 Jul 9.
The phenothiazine methylene blue (MB) is attracting increasing attention because it seems to have beneficial effects in the pathogenesis of Alzheimer's disease (AD). Among other factors, the presence of neuritic plaques of amyloid-β peptide (Aβ) aggregates, neurofibrilar tangles of tau and perturbation of cytosolic Ca are important players of the disease. It has been proposed that MB decreases the formation of neuritic plaques due to Aβ aggregation. However, the molecular mechanism underlying this effect is far from clear. In this work, we show that MB stimulates the Ca-ATPase activity of the plasma membrane Ca-ATPase (PMCA) in human tissues from AD-affected brain and age-matched controls and also from pig brain and cell cultures. In addition, MB prevents and even blocks the inhibitory effect of Aβ on PMCA activity. Functional analysis with mutants and fluorescence experiments strongly suggest that MB binds to PMCA, at the C-terminal tail, in a site located close to the last transmembrane helix and also that MB binds to the peptide. Besides, Aβ increases PMCA affinity for MB. These results point out a novel molecular basis of MB action on Aβ and PMCA as mediator of its beneficial effect on AD.
苯并噻嗪亚甲基蓝（MB）因其在阿尔茨海默病（AD）发病机制中似乎具有有益作用而受到越来越多的关注。在其他因素中，淀粉样β肽（Aβ）聚集的神经突斑块、tau 的神经纤维缠结和细胞溶质 Ca 的紊乱是疾病的重要参与者。有人提出 MB 由于 Aβ 聚集而减少神经突斑块的形成。然而，这种作用的分子机制还远不清楚。在这项工作中，我们表明 MB 刺激人 AD 脑和年龄匹配对照脑以及猪脑和细胞培养物中质膜 Ca-ATP 酶（PMCA）的 Ca-ATP 酶活性。此外，MB 可预防甚至阻断 Aβ对 PMCA 活性的抑制作用。通过突变体和荧光实验进行的功能分析强烈表明 MB 结合到 PMCA 的 C 末端尾部，位于靠近最后一个跨膜螺旋的位置，并且 MB 结合到肽上。此外，Aβ增加了 PMCA 对 MB 的亲和力。这些结果指出了 MB 对 Aβ 和 PMCA 的作用的新分子基础，作为其对 AD 有益作用的介导物。
