TBC1D15-regulated mitochondria–lysosome membrane contact exerts neuroprotective effects by alleviating mitochondrial calcium overload in seizure

Mitochondrial calcium overload plays an important role in the neurological insults in seizure. The Rab7 GTPase-activating protein, Tre-2/Bub2/Cdc16 domain family member 15 (TBC1D15), is involved in the regulation of mitochondrial calcium dynamics by mediating mitochondria-lysosome membrane contact. However, whether TBC1D15-regulated mitochondria-lysosome membrane contact and mitochondrial calcium participate in neuronal injury in seizure is unclear. We aimed to investigate the effect of TBC1D15-regulated mitochondria-lysosome membrane contact on epileptiform discharge-induced neuronal damage and further explore the underlying mechanism. Lentiviral vectors (Lv) infection and stereotaxic adeno-associated virus (AAV) injection were used to regulate TBC1D15 expression before establishing in vitro epileptiform discharge and in vivo status epilepticus (SE) models. TBC1D15's effect on inter-organellar interactions, mitochondrial calcium levels and neuronal injury in seizure was evaluated. The results showed that abnormalities in mitochondria-lysosome membrane contact, mitochondrial calcium overload, mitochondrial dysfunction, increased levels of reactive oxygen species, and prominent neuronal damage were partly relieved by TBC1D15 overexpression, whereas TBC1D15 knockdown markedly deteriorated these phenomena. Further examination revealed that epileptiform discharge-induced mitochondrial calcium overload in primary hippocampal neurons was closely associated with abnormal mitochondria-lysosome membrane contact. This study highlights the crucial role played by TBC1D15-regulated mitochondria-lysosome membrane contact in epileptiform discharge-induced neuronal injury by alleviating mitochondrial calcium overload.