Structural Dynamics of Presynaptic Membrane Fusion

描述(申请人提供)：这个跨学科项目的目标是从结构-生物物理的角度阐明突触前膜融合的机制。分泌途径中细胞膜的融合是由超分子机器介导的，超分子机器根据需要组装，并在任务完成时拆卸。突触前(和其他细胞内)膜融合的核心是SNARE核心复合体的组装。该领域最流行的模型是，SNARE核心复合体的组装通过一种仍然鲜为人知的机制来驱动膜合并。SNARES的组装和拆解被认为是由许多辅助蛋白调控和催化的，包括SM-蛋白、NSF和α-SNAP。尽管其中许多蛋白质的可溶性域的结构是已知的，甚至是它们之间的一些复合体的结构，并且对我们目前对它们在膜融合中可能的作用做出了巨大的贡献，但它们在膜对接和融合的不同步骤中的确切作用部位还没有确定。同样，在分子水平上对突触融合中的钙感受器突触素的作用部位仍然知之甚少。因此，这个计划的主要焦点是将注意力转移到在膜的背景下研究这些膜蛋白的空间关系和相互作用。三个主要的程序组成部分将解决这些融合机器如何在膜上组装/拆卸，以及如何在膜上工作，最终将它们转化为有效的融合孔。为了实现这一目标，将开发和使用新的生物物理技术。

DESCRIPTION (provided by applicant): The goal of this interdisciplinary program is to elucidate the mechanism of presynaptic membrane fusion from a mostly structural-biophysical perspective. Fusions of intracellular membranes in the secretory pathway are mediated by supramolecular machines that are assembled on demand and disassembled when the task is completed. At the core of presynaptic (and other intracellular) membrane fusion is the assembly of the SNARE core complex. The most prevalent model in the field is that the assembly of the SNARE core complex drives the membrane merger by a mechanism that is still poorly understood. The assembly and disassembly of SNAREs is believed to be regulated and catalyzed by numerous accessory proteins including SM-proteins, NSF, and alpha-SNAP. Although structures of soluble domains of many of these proteins and even of some complexes between them are known and have enormously contributed to our current understanding of their possible roles in membrane fusion, their precise sites of action at different steps of membrane docking and fusion have not yet been determined. Likewise, the site of action of the calcium sensor synaptotagmin in synaptic fusion is still poorly understood at the molecular level. Therefore, the main focus of this program is to shift attention to studying spatial relationships and interactions of these membrane proteins in the context of membranes. The three major program components will address how these fusion machines assemble/disassemble on membranes and work on membranes to eventually convert them to form productive fusion pores. To accomplish this goal, new biophysical techniques will be developed and used.