Ca2+-phospholipid-dependent regulation of Munc13-1 is essential for post-tetanic potentiation at mossy fiber synapses and supports working memory

• Ca²⁺-dependent Munc13-1 priming supports synaptic short-term facilitation • Ca²⁺-dependent Munc13-1 priming enhancement is required for post-tetanic potentiation • Disrupted Ca²⁺-dependent Munc13-1 regulation impairs spatial working memory Ca²⁺-dependent Munc13-1 priming supports synaptic short-term facilitation Ca²⁺-dependent Munc13-1 priming enhancement is required for post-tetanic potentiation Disrupted Ca²⁺-dependent Munc13-1 regulation impairs spatial working memory Hippocampal mossy fiber (hMF) to CA3 pyramidal cell synapses are thought to support the formation of working memory through presynaptic short-term facilitation (STF) and post-tetanic potentiation (PTP). However, the molecular mechanisms underlying these transient forms of synaptic enhancement are unclear. We show here that Munc13-1-mediated priming of synaptic vesicles at active zones controls hMF STF and PTP in response to Ca 2+ -phospholipid and Ca 2+ -calmodulin signaling. Knockin mice expressing Munc13-1 variants insensitive to either signaling pathway exhibit pronounced deficits in STF and PTP, and the PTP induction threshold is markedly increased upon blockade of Ca 2+ -phospholipid-Munc13-1 signaling. Since these synaptic defects are accompanied by working memory deficits, especially in mice expressing the Ca 2+ -phospholipid-insensitive Munc13-1 variant, we conclude that the Ca 2+ -dependent regulation of Munc13-1-mediated SV priming co-determines hMF short-term plasticity and working memory formation.