Synapses drive local mitochondrial ATP synthesis to fuel plasticity

Our brain constantly forms new memories and stabilizes existing memories. To achieve such cognitive flexibility, the brain is wired by plastic synapses that are hotspots of energy consumption. Supplying energy to distant synapses is challenging as they are distributed throughout dendrites and axons, spanning hundreds of microns from their cell body. Synapses, therefore, require an instant and local energy supply provided by mitochondria stabilized near dendritic spines. However, the mechanisms by which synapses communicate their energy demands to locally stable mitochondria to drive local energy production and sustain synaptic plasticity is unknown. Using highly sensitive spine- and mitochondrial ATP reporters and two-photon glutamate uncaging to stimulate individual spines, we find that synaptic plasticity input drives instant and sustained increase in spine ATP levels, provided by local ATP synthesis in [~]10-20 m spatially confined compartments within mitochondria. This spatially localized mitochondrial ATP generation is driven by a spatially localized mitochondrial calcium influx independent of the endoplasmic reticulum. Notably, the initial spine ATP increase, supported by local mitochondrial ATP synthesis, is independent of CaMKII and the energy demands of spine structural plasticity. Without local calcium signaling and mitochondrial stabilization, synapses do not meet their instant and sustained energy needs, resulting in synaptic plasticity defects, as observed in neurological disorders.