Institute of Physical Biology, Heinrich-Heine University, 40225 Düsseldorf, Germany.
Department of Biochemistry and Structural Biology, Centre for Molecular Protein Science, Lund University, SE-221 00 Lund, Sweden.
ACS Chem Neurosci. 2020 Mar 18;11(6):909-918. doi: 10.1021/acschemneuro.9b00594. Epub 2020 Feb 28.
Amyloid fibrils of α-synuclein (α-syn) are a component of Lewy bodies, the characteristic hallmark of Parkinson's disease. Amyloid fibrils arise through primary nucleation from monomers, which in the case of α-syn is often heterogeneous, followed by the growth of the nuclei by monomer addition. Secondary nucleation corresponds to the formation of new fibrils facilitated by pre-existing fibrils. While it is well-established that the newly added monomer in fibril elongation adopts the conformation of the monomers in the seed ("templating"), it is unclear whether fibrils formed through secondary nucleation of monomers on the surface of seed fibrils copy the structure of the "parent" fibril. Here we show by biochemical and microscopical methods that the secondary nucleation of α-syn, enabled at mildly acidic pH, leads to fibrils that structurally resemble more closely those formed under the same conditions, rather than the seeds if these are formed under different solution conditions. This result has important implications for the mechanistic understanding of the secondary nucleation of amyloid fibrils and its role in the propagation of aggregate pathology in protein misfolding diseases.
α-突触核蛋白（α-syn）的淀粉样纤维是路易体的组成部分，路易体是帕金森病的特征性标志物。淀粉样纤维通过单体从初级成核开始形成，在α-syn 的情况下，通常是异质的，然后通过单体的添加来增加核的生长。次级成核对应于新纤维的形成，这是由预先存在的纤维促进的。虽然已经确定在纤维延伸中新添加的单体采用种子中的单体的构象（“模板化”），但尚不清楚通过在种子纤维表面上的单体的次级成核形成的纤维是否复制“母”纤维的结构。在这里，我们通过生化和显微镜方法表明，在轻度酸性 pH 下，α-syn 的次级成核导致的纤维在结构上与在相同条件下形成的纤维更相似，而不是在不同溶液条件下形成的种子。这一结果对淀粉样纤维的次级成核的机制理解及其在蛋白质错误折叠疾病中聚集病理学传播中的作用具有重要意义。
