Effects of optineurin mutants on SH-SY5Y cell survival

Mutations in the optineurin gene (OPTN) have been found to be associated with glaucoma and amyotrophic lateral sclerosis (ALS). However, the mechanism by which this single gene mutation leads to neurodegeneration in those two diseases remains unrevealed. To study the roles of wild-type (WT) OPTN and its pathogenic mutants in neuronal survival, here we overexpressed SH-SY5Y cells with WT OPTN or its four mutants (E50K, M98K, Q398X and E478G), and detected their effects on neuronal viability under normal or oxidative stress conditions. We found that overexpression of WT OPTN or its glaucoma-linked mutants (E50K and M98K) causes little harm in SH-SY5Y cells, while ALS-associated OPTN mutants (Q398X and E478G) leads to remarkably increased oxidative status and decreased antioxidase activity, which might result in severe mitochondrial dysfunction and neuronal injury. Further investigation suggests that overexpression of WT OPTN promotes endogenous antioxidase activation in the SH-SY5Y cells under oxidative stress and increases neuronal survival. Nevertheless, this neuroprotective effect of WT OPTN is abolished by its four mutants. Our results indicate that oxidative stress may play a central role in the pathogenesis of glaucoma and ALS caused by OPTN mutation.