Glucohexaose-induced protein phosphatase 2C regulates cell redox status of cucumber seedling

Protein Phosphatase 2C (PP2C) is an important phosphatase-like protein in eukaryotic organisms that can negatively regulate protein kinase cascade abscisic acid (ABA) signal system through phosphorylation and carry out vital roles in various cell processes. The previous study indicated that the accumulation of reactive oxygen species (ROS) is a part of mechanism of glucohexaose-induced resistance in cucumber cotyledons, and CsPP2C80s might play a crucial role in processes related to ROS produce and signal transduction. To identify the mechanism of CsPP2C80s involved in glucohexaose and ABA signaling regulating cell redox status, the effects of glucohexaose and ROS inhibitor pretreatment on endogenous ABA content and ABA signaling genes expression levels of cucumber seedlings were analysed. These results suggest that cucumber CsPP2C80s are involved in ROS accumulation and ABA signal transduction pathway induced by glucohexaose, CsPP2C80s play a positive regulatory role in process of ABA combined with ABA receptors (PYLs) to activate SNF1-related protein kinases 2 (SnRK2s) and regulate NADPH oxidase to produce extracellular hydrogen peroxide (H2O2), providing unequivocal molecular evidence of PP2C-mediated ABA response mechanisms functioning in cell redox status induced by glucohexaose.

Small Interfering RNA-Mediated Silencing of Heat Shock Protein 27 (HSP27) Increases Chemosensitivity to Paclitaxel by Increasing Production of Reactive Oxygen Species in Human Ovarian Cancer Cells (HO8910)

Increasing evidence indicates that reactive oxygen species (ROS) are involved in paclitaxel cytotoxicity. Modulating the oxidant–antioxidant status of tumour cells may increase the antitumour activity of paclitaxel. The cytoprotective roles of heat shock protein 27 (HSP27) include chaperoning cellular proteins, regulating apoptotic signalling and modulating oxidative stress. Immunohistochemical staining for HSP27 in human ovarian cancer specimens showed HSP27 was associated with aggressive malignant ovarian disease. Small interfering RNA (siRNA) was used to down-regulate HSP27 in human ovarian cancer cells (HO8910). Reduction of HSP27 expression increased the in vitro chemosensitivity of HO8910 cells to paclitaxel and increased paclitaxel-induced apoptosis and ROS production, although the ROS scavenger, N-acetyl-l-cysteine, partly offset the effects of HSP27 siRNA. Thus, gene knock-down of HSP27 offsets the role of this protein in resisting oxidant stress, thereby indirectly increasing the sensitivity of cells to paclitaxel. The siRNA-induced knock-down of HSP27 could be a novel and potent strategy to help overcome chemotherapeutic resistance to paclitaxel in epithelial ovarian cancer cells.