A glaucoma-associated mutant of optineurin selectively induces death of retinal ganglion cells which is inhibited by antioxidants

Abstract

Purpose: Mutations in the coding region of the OPTN gene are associated with certain glaucomas. Although the function of the optineurin protein is yet to be elucidated, the most common mutation, E50K, is associated with a severe phenotype. This study explores some functional features of optineurin and its mutants. Methods: Plasmids expressing normal or wild-type (WT) and E50K, R545Q, H26D, and H486R mutant optineurin were transfected into HeLa, Cos-1, IMR32, and the rat retinal ganglion cell (RGC) line RGC-5, and their effects on cell survival monitored by morphologic observation of cells were studied. Expression of optineurin and its mutants was monitored by immunofluorescence staining of cells and by Western blotting. Results: The E50K mutant of optineurin selectively induced the death of retinal ganglion cells but not of the other cell lines tested. Although the expression of optineurin and E50K mutant suppressed cell death induced by tumor necrosis factor-α in HeLa cells, they potentiated this cell death in retinal ganglion cells. Cell death induced by the optineurin mutant in retinal ganglion cells was inhibited by the antioxidants N-acetylcysteine and Trolox. Reactive oxygen species (ROS) were produced upon expression of E50K, which were reduced by antioxidants. Coexpression of manganese superoxide dismutase with the E50K mutant abolished ROS production and inhibited cell death. Conclusions: The E50K mutation of optineurin acquired the ability to induce cell death selectively in retinal ganglion cells. This cell death was mediated by oxidative stress. The present findings raise the possibility of antioxidant use for delaying or controlling some forms of glaucoma.