Excitatory synapses exhibit characteristic proteinaceous microcompartments at the post-synaptic membrane known as the post-synaptic density (PSD). The PSD is richly organized into multi-protein complexes composed of glutamate receptors, scaffolding proteins, kinases, cytoskeleton, and G-protein signaling effectors. The dynamic reorganizations of the higher-order architecture and composition of PSD signaling complexes underlies synaptic plasticity, learning, and memory. Dysfunction or disruption of PSD complexes is implicated in neurological disorders such as Alzheimer’s disease, Parkinson’s disease, autism spectrum disorders, depression, and schizophrenia. Transmembrane glutamate receptor/ion channels (NMDAR and AMPAR) form the functional core of the PSD. The dynamic trafficking of receptors into and out of the PSD ultimately controls the strength of synaptic connections. Scaffolding proteins (e.g., PSD-95, GRIP1, Shank) corral these receptors along with signaling effectors (e.g., CaMKII, Ras, SynGAP, nNOS) and cytoskeleton to actively remodel the PSD and tune neuronal activity.
Illuminating the architecture of these scaffolded PSD signaling complexes remains a frontier goal in molecular neurobiology. Nevertheless, synaptic signaling complexes are large and highly dynamic, problematic targets for structural biology. To address the challenges of exploring the architecture of PSD scaffolded signaling complexes, we apply a battery of protein footprinting, chemical biology, and proteomics approaches.