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 in intact neural circuits remains challenging because active synapses are sparse and transient, and current proteomic approaches cannot selectively label proteins at these sites. To address this, we developed a synapse-targeted calcium-dependent biotin ligase (synaptic Cal-ID) that labels proteins at active synapses in response to activity-driven calcium transients. Using synaptic Cal-ID, we examined the molecular landscape of active synapses in cultured neurons and mouse brains, enabling their proteomic characterization in a native physiological context. 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 epidermal growth factor receptor (EGFR) accumulation and signaling at synapses to support synaptic maturation. Consistent with a broader role in activity-dependent synaptic remodeling, EGFR signaling was also required for synaptic plasticity and memory. Together, our findings uncover a molecular mechanism by which activity-driven calcium signals rapidly reorganize signaling machinery at synapses to couple synaptic activity with maturation, plasticity and memory.