Cryo-electron tomography reveals postsynaptic nanoblocks in excitatory synapses for transcellular alignment

Abstract

AbstractThe nanoscale organization of proteins within synapses is critical for maintaining and regulating synaptic transmission and plasticity. Here, we use cryogenic electron tomography to directly visualize thein situthree-dimensional architecture and supramolecular organization of transsynaptic alignment of pre-cleft-postsynaptic components in their native cellular context in both synaptosomes from rat hippocampi and synapses from rat primary cultured neurons. High-resolution electron microscopy and quantitative analyses reveal that release sites align with adhesion molecules, receptor clusters, and postsynaptic density (PSD) nanoblocks as a physical, transsynaptic, nano- alignment. Additionally, it has been determined that the PSDs contain different-sized, membrane-associated, subsynaptic protein nanoblocks. Furthermore, large nanoblocks are formed by small nanoblocks positioned close enough together. Lastly, the tomograms of synaptosomes allow us to detect the glutamate receptor-like particles by subtomogram averaging at resolutions of 24 Å and 26 Å. The results of this study provide a more comprehensive understanding of synaptic ultrastructure and demonstrate that PSD is organized into subsynaptic nanoblocks to form transcellular alignment.