Details

Autor(en) / Beteiligte

• XIAOMING ZHOU
• WU YIN
• DOI, Sonia Q
• ROBINSON, Shawn W
• TAKEYASU, Kunio
• XUETAO FAN

Titel

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

Ist Teil von

• American Journal of Physiology: Cell Physiology, 2003-08, Vol.54 (2), p.C319-C326

Ort / Verlag

Bethesda, MD: American Physiological Society

Erscheinungsjahr

2003

Link zum Volltext

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• 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. [PUBLICATION ABSTRACT]