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K. Xing, R. Badamas, M. F. Lou; Thioredoxin Binding Protein-2 (TBP-2)/Txnip-Induced Cell Apoptosis. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2124.
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The bioavailability of thioredoxin (Trx) is regulated by the expression of its binding protein, thioredoxin binding protein-2 (TBP-2)/Txnip. In previous study we have found that TBP-2 over-expressed cells had lower Trx activity and induced cell apoptosis. The purpose of this study is to investigate the mechanism of Thioredoxin Binding Protein (TBP-2)-induced cell growth retardation in human lens epithelial (HLE B3) cells.
TBP-2 or vector- transfected HLE B3 cells were grown in MEM with 20%FBS for experiment. For cell growth analysis, 1x10^6 cells were seeded and cell number was counted on 7th day. Western blot analysis was performed to detect caspase-3 and the phosphorylation of JNK, ERK1/2, and p38. Activation of Caspase-3 was examined using both Western blot analysis and activity assay. Cell cycle was analyzed using flow cytometry.
In TBP-2-transfected HLE B3 cells, TBP-2 was over-expressed without changing the expression of thioredoxin (Trx). TBP-2-transfected cells grew more slowly than vector-transfected cells. In comparison to the vector-transfected cells, TBP-2 over-expression induced higher activation of JNK (P-JNK) but had no effect on ERK1/2 or p38 activation. Active form of caspase-3 was detected in TBP-2-transfected cells with the activity of caspase-3/7 elevated 3-fold in comparison with the control cells. Cell cycle analysis showed that TBP-2 transfected cells were stopped and accumulated in G2-M stage.
Over-expression of TBP-2 induced cell growth retardation in HLE B3 cells by the activation of cell apoptotic pathway.
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