Modeling synaptic vesicles: how does alpha-Synuclein inhibit fusion?

项目摘要 我们的目标是发展一个机制的理解抑制突触囊泡融合， 单体突触核蛋白（S）。这项研究将为新的治疗策略奠定基础， 帕金森病（PD）的治疗。越来越多的人一致认为，单体S是一种中央调节因子， 突触囊泡运输的组成部分。虽然路易体的形成，介导的聚集 通常与PD相关，高水平的<$S也被证明会破坏 正常的囊泡运输，并显着抑制神经递质的释放，而不形成戊S聚集体。 我们的方法将涉及突触囊泡的生物物理和力学性质的定量研究 膜，我们将联合收割机结合粗粒分子动力学模拟与面板， 补充生物物理实验。精确理解 单体S和突触囊泡膜将使我们能够评估蛋白质在囊泡中的作用。 与PD相关的贩运缺陷。 有限的生物物理数据产生了关于S过度表达如何抑制囊泡的相互矛盾的观点。 在没有原纤维形成的情况下运输和融合。在从酵母到啮齿动物的多个模型系统中， 过量的硫已被证明会使质膜上正常的突触囊泡循环停止。一 一种观点认为，这种病理学可能是由S和其他突触或质膜之间的相互作用驱动的。 蛋白质（例如SNARES）。我们提出了另一种观点，基于我们的实验室和其他人最近的工作。 根据这一观点，S可以直接改变膜内脂质的物理性质，即 膜的刚性和相位。这是在与其他蛋白质没有特异性相互作用的情况下实现的。我们 因此，我们推测S可能具有控制突触囊泡融合的内在能力。这种假设是 受我们的初步数据和生物物理实验结果的激励，这些结果表明， 降低了膜的刚性，可以改变膜的曲率，并且可以抑制合成的（否则， 无蛋白质）脂质囊泡。 我们提出的研究紧密结合了计算建模与实验x射线散射 和原子力显微镜来弥合理解S如何产生物理屏障的关键差距， 囊泡融合拟议的研究途径将提供有关PD相关贩运的关键信息 缺陷最终，我们的工作将导致更好地了解正常和异常的功能， 定位社区以开发利用蛋白质的天然状态的新的治疗策略（即， 恢复适当的囊泡运输）。

PROJECT SUMMARY Our goal is to develop a mechanistic understanding of the inhibition of synaptic vesicle fusion by monomeric ¿-Synuclein (¿S). This research will establish the foundation for new therapeutic strategies in the treatment of Parkinson's disease (PD). There is growing consensus that monomeric ¿S is a central regulatory component of synaptic vesicle trafficking. Although the formation of Lewy bodies, mediated by the aggregation of ¿S into insoluble fibrils, is commonly associated with PD, high levels of ¿S have also been shown to disrupt normal vesicle trafficking and markedly inhibit neurotransmitter release without the formation of ¿S aggregates. Our approach will involve quantitative studies of the biophysical and mechanical properties of synaptic vesicle membranes for which we will combine coarse-grained molecular dynamics simulations with a panel of complementary biophysical experiments. A precise understanding of the native interactions between monomeric ¿S and synaptic vesicle membranes will position us to evaluate the protein's role in vesicle trafficking defects as they relate to PD. Limited biophysical data have yielded conflicting views on how ¿S over-expression inhibits vesicle trafficking and fusion in the absence of fibril formation. In multiple model systems from yeast to rodents, an overabundance of ¿S has been shown to stall proper synaptic vesicle cycling at the plasma membrane. One view is that this pathology may be driven by interactions between ¿S and other synaptic or plasma membrane proteins (e.g. SNARES). We propose an alternate view based on recent work both from our labs and others. According to this view, ¿S can directly alter the physical properties of lipids within membranes - namely membrane rigidity and phase. This is achieved in the absence of specific interactions with other proteins. We therefore reason that ¿S might have an intrinsic capacity to control synaptic vesicle fusion. This hypothesis is motivated by our preliminary data and published result from biophysical experiments, which show that ¿S reduces a membrane's rigidity, can alter membrane curvature, and can inhibit fusion of synthetic (otherwise protein-free) lipid vesicles. Our proposed research intimately combines computational modeling with experimental x-ray scattering and atomic force microscopy to bridge a critical gap in understanding how ¿S creates physical barriers to vesicle fusion. The proposed research avenue will provide critical information about PD associated trafficking defects. Ultimately, our work will lead to better understanding of normal and abnormal functions of ¿S and position the community to develop new therapeutic strategies that exploit the native state of the protein (i.e., restoring proper vesicle trafficking).