title: Caspase-3 is actively involved in okadaic acid-induced lens epithelial cell apoptosis.
abstract: Phosphorylation and dephosphorylation are important cellular events regulating 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 revealed that in the immortal rabbit lens epithelial cell line, N/N1003A, inhibition of PP-1, but not PP-2A, leads to rapid apoptosis of the lens epithelial cells. This induction of cell death is associated with up-regulated expression of a set of genes, including the tumor-suppressor gene, p53, and the proapoptotic gene, bax. In the present study, we demonstrate that inhibition 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 protease, caspase-3, is important in the execution of okadaic acid-induced apoptosis. Treatment of the primary cultures of rat lens epithelial cells with 100 nM okadaic acid up-regulates expression of caspase-3 at the mRNA, protein, 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 immortal cell line N/N1003A. Furthermore, stable expression of the mouse gene encoding lens alphaB crystallin inhibits okadaic acid-induced apoptosis, and this inhibition is associated with repression of the okadaic acid-induced up-regulation of caspase-3 activity. Taken together, these results demonstrate that caspase-3 is actively involved in okadaic acid-induced lens epithelial cell apoptosis.
authors.affiliation: Laboratory of Molecular and Cellular Biology, Harkness Eye Institute, College of Physicians and Surgeons of Columbia University, 630 West 168th Street, New York, New York 10032, USA. Lidw@umdnj.edu
authors.forename: D W
authors.initials: DW
authors.lastname: Li
authors.forename: H
authors.initials: H
authors.lastname: Xiang
authors.forename: Y W
authors.initials: YW
authors.lastname: Mao
authors.forename: J
authors.initials: J
authors.lastname: Wang
authors.forename: U
authors.initials: U
authors.lastname: Fass
authors.forename: X Y
authors.initials: XY
authors.lastname: Zhang
authors.forename: C
authors.initials: C
authors.lastname: Xu
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3; D020169:Caspases / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D002478:Cells, Cultured; D003459:Crystallins / Q000235:genetics; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D004792:Enzyme Precursors / Q000096:biosynthesis / Q000235:genetics; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D007908:Lens, Crystalline / Q000166:cytology* / Q000201:enzymology; D051379:Mice; D019319:Okadaic Acid / Q000494:pharmacology*; D009842:Oligopeptides / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors; D054645:Protein Phosphatase 1; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D014407:Tumor Cells, Cultured; D015854:Up-Regulation
chemical_list: D003459:Crystallins; D004791:Enzyme Inhibitors; D004792:Enzyme Precursors; D009842:Oligopeptides; D012333:RNA, Messenger; C099158:acetyl-aspartyl-glutamyl-valyl-aspartal; D019319:Okadaic Acid; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; C505409:Casp3 protein, mouse; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases