Super-Resolution Microscopy Reveals a Nanoscale Organization of Acetylcholine Receptors for Trans-Synaptic Alignment at Neuromuscular Synapses.

• Type of Material: Article
• Authors: Amanda L. York, Emory University; James Zheng, Emory University
• Language: English
• Date: 2017-07-31
• Publisher: Society for Neuroscience
• Publication Version: Final Published Version
• Copyright Statement: © 2017 York and Zheng
• License: Creative Commons Attribution 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1523/ENEURO.0232-17.2017
• Title of Journal or Parent Work: eNeuro
• ISSN: 2373-2822
• Volume: 4
• Issue: 4
• Grant/Funding Information: NIH; This work was also supported by the Emory University Integrated Cellular Imaging Microscopy Core of the Emory Neuroscience NINDS Core Facilities Grant 5P30NS055077 and by the Robert P. Apkarian Integrated Electron Microscopy Core Grant UL1TR000454.; National Institute of Mental Health (NIMH) 100000025, MH104632, MH108025 (to J.Q.Z.).; This work was supported by the following grants: National Institute of General Medical Sciences (NIGMS) 100000057, GM083889; HHS
• Keywords: super-resolution microscopy; NMJ; synaptic receptors; spatial distribution; junctional folds
• Research Categories: Biology, Neuroscience; Biology, Cell

Abstract

The neuromuscular junction (NMJ) is a chemical synapse formed between motoneurons and skeletal muscle fibers. The vertebrate NMJ uses acetylcholine (ACh) as the neurotransmitter and features numerous invaginations of the postsynaptic muscle membrane termed junctional folds. ACh receptors (AChRs) are believed to be concentrated on the crest of junctional folds but their spatial organization remains to be fully understood. In this study, we utilized super-resolution microscopy to examine the nanoscale organization of AChRs at NMJ. Using Structured Illumination Microscopy, we found that AChRs appear as stripes within the pretzel-shaped mouse NMJs, which however, do not correlate with the size of the crests of junctional folds. By comparing the localization of AChRs with several pre- and postsynaptic markers of distinct compartments of NMJs, we found that AChRs are not distributed evenly across the crest of junctional folds as previously thought. Instead, AChR stripes are more closely aligned with the openings of junctional folds as well as with the presynaptic active zone. Using Stochastic Optical Reconstruction Microscopy (STORM) for increased resolution, we found that each AChR stripe contains an AChR-poor slit at the center that is equivalent to the size of the opening of junctional folds. Together, these findings indicate that AChRs are largely localized to the edges of crests surrounding the opening of folds to align with the presynaptic active zones. Such a nanoscale organization of AChRs potentially enables trans-synaptic alignment for effective synaptic transmission of NMJs.