Munc13-1 is a Ca2+-phospholipid-dependent vesicle priming hub that shapes synaptic short-term plasticity and enables sustained neurotransmission

Abstract

During ongoing presynaptic action potential (AP) firing, transmitter release is limited by the availability of release-ready synaptic vesicles (SVs). The rate of SV recruitment (SVR) to release sites is strongly upregulated at high AP frequencies to balance SV consumption. We show that Munc13-1-an essential SV priming protein-regulates SVR via a Ca²⁺-phospholipid-dependent mechanism. Using knockin mouse lines with point mutations in the Ca²⁺-phospholipid-binding C₂B domain of Munc13-1, we demonstrate that abolishing Ca²⁺-phospholipid binding increases synaptic depression, slows recovery of synaptic strength after SV pool depletion, and reduces temporal fidelity of synaptic transmission, while increased Ca²⁺-phospholipid binding has the opposite effects. Thus, Ca²⁺-phospholipid binding to the Munc13-1-C₂B domain accelerates SVR, reduces short-term synaptic depression, and increases the endurance and temporal fidelity of neurotransmission, demonstrating that Munc13-1 is a core vesicle priming hub that adjusts SV re-supply to demand.

Keywords: C2 domains; Calcium; Munc13; Phospholipids; Presynapse; Short-termsynaptic plasticity; Synapse; Synaptic transmission; Synaptic vesicle replenishment; calyx of Held.