Stimulation of Na,K-ATPase by low potassium requires reactive oxygen species

Abstract

The signaling pathway that transduces the stimulatory effect of low K+ on the biosynthesis of Na,K-ATPase remains largely unknown. The present study was undertaken to examine whether reactive oxygen species (ROS) mediated the effect of low K+ in Madin-Darby canine kidney (MDCK) cells. Low K+ increased ROS activity in a time- and dose-dependent manner, and this effect was abrogated by catalase and N-acetylcysteine (NAC). To determine the role of ROS in low-K+-induced gene expression, the cells were first stably transfected with expression constructs in which the reporter gene chloramphenicol acetyl transferase (CAT) was under the control of the avian Na,K-ATPase alpha-subunit 1.9 kb and 900-bp 5'-flanking regions that have a negative regulatory element. Low K+ increased the CAT expression in both constructs. Catalase or NAC inhibited the effect of low K+. To determine whether the increased CAT activity was mediated through releasing the repressive effect or a direct stimulation of the promoter, the cells were transfected with a CAT expression construct directed by a 96-bp promoter fragment that has no negative regulatory element. Low K+ also augmented the CAT activity expressed by this construct. More importantly, both catalase and NAC abolished the effect of low K+. Moreover, catalase and NAC also inhibited low-K+-induced increases in the Na,K-ATPase alpha1- and beta1-subunit protein abundance and ouabain binding sites. The antioxidants had no significant effect on the basal levels of CAT activity, protein abundance, or ouabain binding sites. In conclusion, low K+ enhances the Na,K-ATPase gene expression by a direct stimulation of the promoter activity, and ROS mediate this stimulation and also low-K+-induced increases in the Na,K-ATPase protein contents and cell surface molecules.

Impairment of Na+,K+-ATPase in CD95(APO-1)-induced human T-cell leukemia cell apoptosis mediated by glutathione depletion and generation of hydrogen peroxide

“…24 The inhibition of this pump makes a large contribution to plasma membrane depolarization. 25 Regulation of this pump occurs at several levels: (1) the long-term regulation, relevant to the de novo synthesis of this pump as suggested in our previous work; 16,26 (2) the short-term regulation by recruitment/internalization of the active pumps to/from the plasma membrane and modulation of ATPase activity, which is essentially involved under a variety of physiological or pathological conditions, such as sodium reabsorption in kidney. 27 This short-term regulation facilitates cells to promptly respond to the acute changes in intracellular ion environment.…”

Human Salivary Histatin 5 Fungicidal Action Does Not Induce Programmed Cell Death Pathways in Candida albicans

“…Recent evidence suggests that ROS are generated by metabolic conditions and that they have subsequent stimulatory or inhibitory functions in other systems, such as ion transport (reviewed by Kourie [20]). In this regard, low intracellular potassium increased ROS levels, which directly stimulated gene expression for NaK-ATPase activity (44). Thus, ROS themselves may contribute to cellular signaling.…”

Histatin 5 Initiates Osmotic Stress Response in Candida albicans via Activation of the Hog1 Mitogen-Activated Protein Kinase Pathway

“…In this model, activation of oxidative stress response pathways would be the major adaptive response for protection of C. albicans from Hst 5 killing. However, an increase in ROS levels in Candida also has been observed following morphogenesis (36) or cell growth arrest (33) and in cells subjected to conditions that cause low intracellular potassium levels (45). Therefore, ROS could be generated in C. albicans cells as a result of Hst 5-induced ion loss and cell cycle arrest as well as from mitochondrial damage.…”