Leber's hereditary optic neuropathy-associated ND1 3733G>C mutation ameliorates the mitochondrial quality control and cellular homeostasis

Abstract

Leber's hereditary optic neuropathy (LHON) is a paradigm for mitochondrial retinopathy because of mitochondrial DNA (mtDNA) mutations. However, the mechanism underlying LHON-linked mtDNA mutations, especially their impact on mitochondrial and cellular integrity, is not well understood. Recently, the ND1 3733G>C (p.E143Q) mutation was identified in three Chinese pedigrees with LHON. In this study, we investigated the pathogenic mechanism of m.3733G>C mutation using cybrids generated by fusing mtDNA-less ρ⁰ cells with enucleated cells from a Chinese patient carrying the m.3733G>C mutation and control subject. Molecular dynamics simulations showed that p.E143Q mutation destabilized these interactions between residues E143 and S110/Y114 or between S141 and W290 in the ND1. Its impact of ND1 structure and function was further evidenced by reduced levels of ND1 in mutant cells. The m.3733G>C mutation caused defective assembly and activity of complex I, respiratory deficiency, diminished mitochondrial ATP production, and increased production of reactive oxygen species in the mutant cybrids carrying the m.3733G>C mutation. These mitochondrial dysfunctions regulated mitochondrial quality control via mitochondrial dynamics and mitophagy. The m.3733G>C mutation-induced dysfunction yielded elevating mitochondrial localization of DRP1, decreasing network connectivity, and increasing fission with abnormal morphologies. Furthermore, the m.3733G>C mutation downregulated ubiquitin-dependent mitophagy pathway, evidenced by decreasing the levels of Parkin and PINK1, but not ubiquitin-independent mitophagy pathway. The m.3733G>C mutation-induced deficiencies reshaped the cellular homeostasis via impairing autophagy process and promoting intrinsic apoptosis. Our findings provide new insights into pathophysiology of LHON arising from the m.3733G>C mutation-induced mitochondrial dysfunctions and reprograming organocellular and cellular homeostasis.

Keywords: ATP; Leber's hereditary optic neuropathy; NADH:ubiquinone oxidoreductase; ND1 mutation; apoptosis; autophagy; mitochondria; mitochondrial fusion and fission; mitophagy; oxidative phosphorylation; reactive oxygen species; vision loss.