Caspase-3 is actively involved in okadaic acid-induced lens epithelial cell apoptosis.
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.
Li
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DW
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
Xiang
H
H
Mao
Y W
YW
Wang
J
J
Fass
U
U
Zhang
X Y
XY
Xu
C
C
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
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