IP3-mediated Ca2+ transfer from ER to mitochondria stimulates ATP synthesis in primary hippocampal neurons
During electrical activity, Ca2+ enhances mitochondrial ATP production, helping to replenish the energy consumed during this process. Most Ca2+ enters the cell via ligand- or voltage-gated channels on the neuronal membrane, where it stimulates the release of additional Ca2+ from the endoplasmic reticulum (ER). Although the influence of cytosolic Ca2+ on neuronal metabolism has been widely investigated, relatively few studies have explored the contribution of ER Ca2+ release in this context. Therefore, we investigated how activity-driven Ca2+ crosstalk between the ER and mitochondria influences the regulation of mitochondrial ATP production. We show that in primary hippocampal neurons derived from rat pups of either sex, depletion of ER Ca2+ led to a reduction in mitochondrial Ca2+ levels during both resting and stimulated states, while exerting only a minimal impact on cytosolic Ca2+ levels. Additionally, impaired ER-mitochondria Ca{superscript 2} transfer led to a reduction in mitochondrial ATP production. Similar effects were observed when inositol-3-phosphate receptors (IP3Rs), but not ryanodine receptors (RyRs), were pharmacologically inhibited. Together, our findings show that, in hippocampal neurons, Ca2+ is transferred from the ER to mitochondria through IP3 receptors, and this Ca2+ crosstalk in turn enhances mitochondrial ATP production in response to neuronal activity. HighlightsO_LICa2+ adjusts mitochondrial ATP synthesis to neuronal activity C_LIO_LIIn the neuronal somata ER-mitochondria Ca2+ crosstalk occurs via IP3 receptors C_LIO_LIIP3-mediated Ca2+ release occurs across a wide range of firing intensities. C_LI