Calcium-dependent synaptic proteomics reveals EGFR signaling at active synapses

Activity-dependent remodeling of the synaptic proteome is essential for circuit maturation, plasticity, and adaptation. However, these molecular changes are transient and spatially sparse in intact neural circuits, making them difficult to resolve under physiological conditions. To address this challenge, we developed synaptic Cal-ID, a synapse-targeted, calcium-dependent proximity labeling strategy that enables activity-resolved proteomic profiling under native physiological conditions. Using synaptic Cal-ID, we uncover an unexpected mechanism by which synaptic activity locally engages epidermal growth factor receptor (EGFR) signaling. We identify two novel synaptic proteins, Anks1a and Ubash3b, that are rapidly recruited following activity and cooperatively promote postsynaptic enrichment and signaling of EGFR. Disruption of this pathway impairs synaptic maturation, plasticity, and memory. Together, these findings reveal how neuronal activity establishes local signaling competence at active synapses by concentrating the molecular machinery required to engage a broadly acting growth factor pathway.