School of Pharmacy, Lanzhou University, Lanzhou 730000, China.
State Key Laboratory of Quality Research in Chinese Medicine, Macau Institute for Applied Research in Medicine and Health, Macau University of Science and Technology, Taipa, Macau, China.
ACS Chem Neurosci. 2020 Mar 4;11(5):772-782. doi: 10.1021/acschemneuro.9b00679. Epub 2020 Feb 18.
Conformational transition from the normal cellular form of prion protein (PrP) to the pathogenic "scrapie" form (PrP) is considered to be a key event in the occurrence of prion disease. Additionally, the H2 C-terminus is widely considered to be a vital site for PrP conformational transition, which can be used as an important region to explore the potential mechanism of PrP misfolding. Therefore, to study the misfolding mechanism of PrP, 500 ns well-tempered metadynamics simulations were performed by focusing on the H2 C-terminus of PrP. For comparison, three systems were designed in total, including PrP in neutral and acidic conditions, as well as H187R mutant. The resulting free energy surfaces (FESs) obtained from metadynamics simulations reveal that acidic conditions and H187R mutation can facilitate PrP misfolding by decreasing free energy barriers for conformational transition and forming energy stable conformational states. Further analyses aimed at H2 C-terminus show that due to the increase of positive charge on residue 187 in both acidic and H187R systems, the electrostatic repulsion of residue 187 and R136/R156 increases greatly, which disrupts the electrostatic interaction network around H2 C-terminus and exposes the hydrophobic core to the solvent. Taken together, acidic conditions and H187R mutation can accelerate PrP misfolding mainly by forming more energetically stable metastable conformations with lower free energy barriers, and electrostatic network disruption involving residue 187 drives the initial misfolding of H2 C-terminus. This study provides quantitative insight into the related function of the H2 C-terminus in the PrP misfolding process, which may guide H2 C-terminus mediated drug design in the future.
构象从朊病毒蛋白（PrP）的正常细胞形式到致病的“瘙痒”形式（PrP）的转变被认为是朊病毒病发生的关键事件。此外，H2 C 端被广泛认为是 PrP 构象转变的关键部位，可以作为探索 PrP 错误折叠潜在机制的重要区域。因此，为了研究 PrP 的错误折叠机制，通过聚焦于 PrP 的 H2 C 端，对其进行了 500 ns 的-well tempered 元动力学模拟。为了进行比较，总共设计了三个系统，包括中性和酸性条件下的 PrP，以及 H187R 突变体。元动力学模拟得到的自由能面（FES）揭示了酸性条件和 H187R 突变可以通过降低构象转变的自由能障碍和形成能量稳定的构象状态来促进 PrP 的错误折叠。进一步针对 H2 C 端的分析表明，由于在酸性和 H187R 系统中，残基 187 上的正电荷增加，残基 187 和 R136/R156 之间的静电排斥大大增加，破坏了 H2 C 端周围的静电相互作用网络，并使疏水性核心暴露于溶剂中。综上所述，酸性条件和 H187R 突变可以通过形成具有更低自由能障碍的更稳定的亚稳态构象来加速 PrP 的错误折叠，并且涉及残基 187 的静电网络破坏导致 H2 C 端的初始错误折叠。这项研究提供了关于 H2 C 端在 PrP 错误折叠过程中的相关功能的定量见解，这可能有助于未来 H2 C 端介导的药物设计。
