Lorenzen Nikolai, Nielsen Søren B, Yoshimura Yuichi, Vad Brian S, Andersen Camilla Bertel, Betzer Cristine, Kaspersen Jørn D, Christiansen Gunna, Pedersen Jan S, Jensen Poul Henning, Mulder Frans A A, Otzen Daniel E
From the Interdisciplinary Nanoscience Center, Center for Insoluble Protein Structures.
From the Interdisciplinary Nanoscience Center, Center for Insoluble Protein Structures, Departments of Chemistry.
J Biol Chem. 2014 Aug 1;289(31):21299-310. doi: 10.1074/jbc.M114.554667. Epub 2014 Jun 6.
Oligomeric species of various proteins are linked to the pathogenesis of different neurodegenerative disorders. Consequently, there is intense focus on the discovery of novel inhibitors, e.g. small molecules and antibodies, to inhibit the formation and block the toxicity of oligomers. In Parkinson disease, the protein α-synuclein (αSN) forms cytotoxic oligomers. The flavonoid epigallocatechin gallate (EGCG) has previously been shown to redirect the aggregation of αSN monomers and remodel αSN amyloid fibrils into disordered oligomers. Here, we dissect EGCG's mechanism of action. EGCG inhibits the ability of preformed oligomers to permeabilize vesicles and induce cytotoxicity in a rat brain cell line. However, EGCG does not affect oligomer size distribution or secondary structure. Rather, EGCG immobilizes the C-terminal region and moderately reduces the degree of binding of oligomers to membranes. We interpret our data to mean that the oligomer acts by destabilizing the membrane rather than by direct pore formation. This suggests that reduction (but not complete abolition) of the membrane affinity of the oligomer is sufficient to prevent cytotoxicity.
多种蛋白质的寡聚体与不同神经退行性疾病的发病机制相关。因此，人们高度关注新型抑制剂的发现，例如小分子和抗体，以抑制寡聚体的形成并阻断其毒性。在帕金森病中，蛋白质α-突触核蛋白（αSN）形成细胞毒性寡聚体。此前已表明，类黄酮表没食子儿茶素没食子酸酯（EGCG）可改变αSN单体的聚集方向，并将αSN淀粉样原纤维重塑为无序寡聚体。在此，我们剖析EGCG的作用机制。EGCG抑制预先形成的寡聚体使囊泡通透并在大鼠脑细胞系中诱导细胞毒性的能力。然而，EGCG并不影响寡聚体的大小分布或二级结构。相反，EGCG固定了C末端区域，并适度降低了寡聚体与膜的结合程度。我们将我们的数据解释为寡聚体通过使膜不稳定而非直接形成孔来发挥作用。这表明降低（但不是完全消除）寡聚体与膜的亲和力足以防止细胞毒性。
