OPA1 overexpression ameliorates mitochondrial cristae remodeling, mitochondrial dysfunction, and neuronal apoptosis in prion diseases

Prion diseases caused by the cellular prion protein (PrPC) conversion into a misfolded isoform (PrPSc) are associated with multiple mitochondrial damages. We previously reported mitochondrial dynamic abnormalities and cell death in prion diseases via modulation of a variety of factors. Optic atrophy 1 (OPA1) is one of the factors that control mitochondrial fusion, mitochondrial DNA (mtDNA) maintenance, bioenergetics, and cristae integrity. In this study, we observed downregulation of OPA1 in prion disease models in vitro and in vivo, mitochondria structure damage and dysfunction, loss of mtDNA, and neuronal apoptosis. Similar mitochondria findings were seen in OPA1-silenced un-infected primary neurons. Overexpression of OPA1 not only alleviated prion-induced mitochondrial network fragmentation and mtDNA loss, decrease in intracellular ATP, increase in ADP/ATP ratio, and decrease in mitochondrial membrane potential but also protected neurons from apoptosis by suppressing the release of cytochrome c from mitochondria to cytosol and activation of the apoptotic factor, caspase 3. Our results demonstrated that overexpression of OPA1 alleviates prion-associated mitochondrial network fragmentation and cristae remodeling, mitochondrial dysfunction, mtDNA depletion, and neuronal apoptosis, suggesting that OPA1 may be a novel and effective therapeutic target for prion diseases.