Details

Autor(en) / Beteiligte

• Zhou, Xiaoming
• Yin, Wu
• Doi, Sonia Q
• Robinson, Shawn W
• Takeyasu, Kunio
• Fan, Xuetao

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.285 (2), p.C319-C326

Ort / Verlag

United States

Erscheinungsjahr

2003

Link zum Volltext

Quelle

Free E-Journal (出版社公開部分のみ）

Beschreibungen/Notizen

• 1 Department of Medicine, Uniformed Services University, Bethesda 20814; 2 Department of Medicine, University of Maryland, Baltimore, Maryland 21201; and 3 Department of Natural Environment Sciences, Kyoto University, Kyoto 606-01, Japan Submitted 19 November 2002 ; accepted in final form 2 April 2003 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 -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 1 - and 1 -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. Madin-Darby canine kidney cells; N -acetylcysteine; catalase Address for reprint requests and other correspondence: X. Zhou, Dept. of Medicine, Uniformed Services Univ., 4301 Jones Bridge Rd., Bethesda, MD 20814 (E-Mail: xiazhou{at}usuhs.mil ).