Nanoscale architecture of synaptic vesicles and scaffolding complexes revealed by cryo- electron tomography

• 成果类型: Article
• 署名作者: Held, Richard G.; Liang, Jiahao; Brunger, Axel T.
• 署名单位: Stanford University; Stanford University; Stanford University; Stanford University; Stanford University; Howard Hughes Medical Institute
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-8846
• DOI: 10.1073/pnas.2403136121
• 发表日期: 2024-07-02
• 关键词: cryoelectron tomography; neurotransmitter release; snare complexes; nmda receptors; ampa receptors; ca2+ channels; synapses; synaptotagmin; transmission; proteins

摘要

The spatial distribution of proteins and their arrangement within the cellular ultrastructure regulates the opening of alpha- amino - 3 - hydroxy - 5 - methyl - 4 - isoxazolepropionic acid (AMPA) receptors in response to glutamate release at the synapse. Fluorescence microscopy imaging revealed that the postsynaptic density (PSD) and scaffolding proteins in the presynaptic active zone (AZ) align across the synapse to form a trans - synaptic nanocolumn, but the relation to synaptic vesicle release sites is uncertain. Here, we employ focused - ion beam (FIB) milling and cryoelectron tomography to image synapses under near - native conditions. Improved image contrast, enabled by FIB milling, allows simultaneous visualization of supramolecular nanoclusters within the AZ and PSD and synaptic vesicles. Surprisingly, membraneproximal synaptic vesicles, which fuse to release glutamate, are not preferentially aligned with AZ or PSD nanoclusters. These synaptic vesicles are linked to the membrane by peripheral protein densities, often consistent in size and shape with Munc13, as well as globular densities bridging the synaptic vesicle and plasma membrane, consistent with prefusion complexes of SNAREs, synaptotagmins, and complexin. Monte Carlo simulations of synaptic transmission events using biorealistic models guided by our tomograms predict that clustering AMPARs within PSD nanoclusters increases the variability of the postsynaptic response but not its average amplitude. Together, our data support a model in which synaptic strength is tuned at the level of single vesicles by the spatial relationship between scaffolding nanoclusters and single synaptic vesicle fusion sites.