Calcium-dependent synaptic proteomics reveals EGFR signaling at active synapses

Synapses are dynamic structures whose protein composition remodels in response to activity. These activity-dependent processes shape synaptic maturation and plasticity, enabling the development and adaptation of neural circuits. However, defining the molecular basis of activity-dependent synaptic remodeling remains challenging because active synapses are sparse and transient, and current proteomic approaches cannot selectively label proteins at these sites. To address this, we took advantage of activity-driven calcium transients and developed a synapse-targeted calcium-dependent biotin ligase (synaptic Cal-ID). Using synaptic Cal-ID, we examined the activity-dependent synaptic proteome in cultured neurons and mouse brains. We identified two previously uncharacterized synaptic proteins, Anks1a and Ubash3b. Both proteins are rapidly recruited to synapses in response to activity, where they cooperatively promote EGF receptor (EGFR) accumulation and signaling at synapses to support synaptic maturation. Together, these results establish activity-dependent EGFR signaling as a crucial mechanism linking synaptic activity to synaptic remodeling and maturation. More broadly, our findings highlight a molecular mechanism by which calcium-dependent activity rapidly reorganizes key signaling machinery at active synapses to dynamically regulate local synaptic signaling.