Knockdown of 15-kDa selenoprotein (Sep15) increases hLE cells' susceptibility to tunicamycin-induced apoptosis.

In this work, we investigated the effect of Sep15 gene knockdown on apoptosis in human lens epithelial (hLE) cells, trying to understand the relevance of Sep15 to cataract formation in the Sep15 knockout (KO) mice. The results showed that sole knockdown of Sep15 by RNA interference did not result in apoptosis; however, reduction of Sep15 expression aggravated tunicamycin (Tm)-induced cell apoptosis and caspases activation. Furthermore, Tm-induced mitochondrial dysfunction was also exacerbated under the Sep15 knockdown condition by measurement of mitochondrial membrane potential decrease and human cytochrome c release into cytosol. Interestingly, the knockdown of Sep15 exacerbated Tm-induced oxidative stress while endoplasmic reticulum (ER) stress was not correspondingly elevated. These results suggest that the protective role of Sep15 against Tm-induced apoptosis in hLE cells is operated via inhibiting oxidative stress rather than regulating Tm-induced ER stress, and the protective role becomes dependent on Sep15 only in acute stress condition.