Mitochondrial Calcium Signaling in the Brain: From Molecular Mechanisms to Behavioral Outcomes

Mitochondria are multifaceted organelles positioned at the intersection of multiple signaling pathways. Beyond serving as one of the main energy providers in the brain, they play crucial roles in shaping cytosolic calcium signals across both neuronal and glial cell populations, modulating synaptic transmission and plasticity, and regulating neuronal excitability and network activity. The involvement of mitochondrial calcium handling in brain cell physiology has been explored for many years. However, by enabling in vivo cell-specific manipulations, the molecular identification of mitochondrial calcium signaling protein complexes, over the past 2 decades, has tremendously improved our understanding of how mitochondria regulate brain function and behavior. This review synthesizes current knowledge of mitochondrial calcium handling mechanisms and protein complexes in the nervous system, as well as their involvement in brain function, from cellular physiology to behavioral consequences. We discuss pharmacological and genetic evidence for a role of mitochondrial calcium handling in synaptic transmission, neuronal excitability, astrocyte functions, and circuit activity. We underline experimental differences across approaches and models, as well as show how genetic tools have challenged or confirmed earlier pharmacological results. Finally, we examine how recent advances using transgenic models have revealed complex roles for mitochondrial calcium signaling in behavioral responses and opened new research avenues.