Two mechanisms underlie the inhibitory/acceleratory action of chemical compounds on tau aggregation including the regulation of cellular kinases and phosphatases activity and direct binding to tau protein. Vitamin B12 is one of the tau polymerization inhibitors, and its deficiency is linked to inactivation of protein phosphatase 2A and subsequently hyperphosphorylation and aggregation of tau protein. Regarding the structure and function of vitamin B12 and tau protein, we assumed that vitamin B12 is also able to directly bind to tau protein. Hence, we investigated the interaction of vitamin B12 with tau protein in vitro using fluorometry and circular dichrosim. Interaction studies was followed by investigation into the effect of vitamin B12 on tau aggregation using ThT fluorescence, circular dichroism, transmission electron microscopy, and SDS-PAGE. The results indicated that vitamin B12 interacts with tau protein and prevents fibrillization of tau protein. Blocking the cysteine residues of tau confirmed the cysteine-mediated binding of vitamin B12 to tau and showed that binding to cysteine is essential for inhibitory effect of vitamin B12 on tau aggregation. SDS-PAGE analysis indicated that vitamin B12 inhibits tau aggregation and that tau oligomers formed in the presence of vitamin B12 are mostly SDS-soluble. We propose that direct binding of vitamin B12 is another mechanism underlying the inhibitory role of vitamin B12 on tau aggregation and neurodegeneration.

中文翻译：

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维生素B12通过与Tau的半胱氨酸残基结合来抑制Tau的原纤维化

化合物对tau聚集的抑制/促进作用是两种机制的基础，包括细胞激酶和磷酸酶活性的调节以及与tau蛋白的直接结合。维生素B12是tau聚合抑制剂之一，其缺乏与蛋白质磷酸酶2A的失活以及随后tau蛋白的过度磷酸化和聚集有关。关于维生素B12和tau蛋白的结构和功能，我们认为维生素B12也能够直接与tau蛋白结合。因此，我们使用荧光测定法和圆二色谱法研究了维生素B12与tau蛋白的相互作用。相互作用研究之后，使用ThT荧光，圆二色性，透射电子显微镜和SDS-PAGE研究了维生素B12对tau聚集的影响。结果表明维生素B12与tau蛋白相互作用并阻止tau蛋白的原纤维化。阻断tau的半胱氨酸残基证实了半胱氨酸介导的维生素B12与tau的结合，并表明与半胱氨酸的结合对于维生素B12对tau聚集的抑制作用至关重要。SDS-PAGE分析表明，维生素B12抑制tau聚集，并且在维生素B12存在下形成的tau低聚物大部分可溶于SDS。我们提出维生素B12的直接结合是维生素B12对tau聚集和神经退行性变的抑制作用的另一种机制。阻断tau的半胱氨酸残基证实了半胱氨酸介导的维生素B12与tau的结合，并表明与半胱氨酸的结合对于维生素B12对tau聚集的抑制作用至关重要。SDS-PAGE分析表明，维生素B12抑制tau聚集，并且在维生素B12存在下形成的tau低聚物大部分可溶于SDS。我们提出维生素B12的直接结合是维生素B12对tau聚集和神经退行性变的抑制作用的另一种机制。阻断tau的半胱氨酸残基证实了半胱氨酸介导的维生素B12与tau的结合，并表明与半胱氨酸的结合对于维生素B12对tau聚集的抑制作用至关重要。SDS-PAGE分析表明，维生素B12抑制tau聚集，并且在维生素B12存在下形成的tau低聚物大部分可溶于SDS。我们提出维生素B12的直接结合是维生素B12对tau聚集和神经退行性变的抑制作用的另一种机制。