Caspase-3 is actively involved in okadaic acid-induced lens epithelial cell apoptosis

Phosphorylation and dephosphorylation are important cellular events regulat ing major metabolic activities such as signal transduction, gene expression , cell cycle progression, and apoptosis. It is well documented that okadaic acid, a potent inhibitor of protein phosphatase-1 (PP-1) and -2A (PP-2A), can induce apoptosis in a variety of cell lines. Our recent studies have re vealed that in the immortal rabbit lens epithelial cell Line, N/N1003A, inh ibition of PP-1, but not PP-2A, leads to rapid apoptosis of the lens epithe lial cells. This induction of cell death is associated with up-regulated ex pression of a set of genes, including the tumor-suppressor gene, p53, and t he proapoptotic gene, box. In the present study, we demonstrate that inhibi tion of PP-1 by okadaic acid in the primary cultures of rat lens epithelial cells also leads to apoptotic death. Moreover,we show that the cysteine pr otease, caspase-3, is important in the execution of okadaic acid-induced ap optosis. Treatment of the primary cultures of rat lens epithelial cells wit h 100 nM okadaic acid up-regulates expression of caspase-3 at the mRNA, pro tein, and enzyme activity levels. Inhibition of the caspase 3 activity with a chemically synthesized inhibitor prevents okadaic acid-induced apoptosis in rat lens epithelial cells. Similar results are also observed in the imm ortal cell line N/N1003A. Furthermore, stable expression of the mouse gene encoding lens alphaB crystallin inhibits okadaic acid-induced apoptosis, an d this inhibition is associated with repression of the okadaic acid-induced up-regulation of caspase-3 activity. Taken together, these results demonst rate that caspase-3 is actively involved in okadaic acid-induced lens epith elial cell apoptosis. (C) 2001 Academic Press.