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Henke, Guido; Setiawan, Iwan; Böhmer, Christoph; Lang, Florian

Activation of Na+/K+-ATPase by the Serum and Glucocorticoid-Dependent Kinase Isoforms

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  • Medientyp: E-Artikel
  • Titel: Activation of Na+/K+-ATPase by the Serum and Glucocorticoid-Dependent Kinase Isoforms
  • Beteiligte: Henke, Guido; Setiawan, Iwan; Böhmer, Christoph; Lang, Florian
  • Erschienen: S. Karger AG, 2002
  • Erschienen in: Kidney and Blood Pressure Research
  • Sprache: Englisch
  • DOI: 10.1159/000068699
  • ISSN: 1420-4096; 1423-0143
  • Schlagwörter: Cardiology and Cardiovascular Medicine ; Nephrology ; Cardiology and Cardiovascular Medicine ; Nephrology
  • Entstehung:
  • Anmerkungen:
  • Beschreibung: <jats:p>&lt;i&gt;Background/Aim:&lt;/i&gt; Expression of the constitutively active form of serum and glucocorticoid-dependent kinase (&lt;sup&gt;S422D&lt;/sup&gt;SGK1) in &lt;i&gt;Xenopus&lt;/i&gt; oocytes has recently been shown to upregulate endogenous Na&lt;sup&gt;+&lt;/sup&gt;/K&lt;sup&gt;+&lt;/sup&gt;-ATPase activity, an effect presumably participating in the regulation of cellular K&lt;sup&gt;+&lt;/sup&gt; uptake and transepithelial Na&lt;sup&gt;+&lt;/sup&gt; transport. SGK1 and the two isoforms SGK2 and SGK3 are stimulated by insulin and insulin-like growth factor-1 (IGF-1), which have been shown to enhance Na&lt;sup&gt;+&lt;/sup&gt;/K&lt;sup&gt;+&lt;/sup&gt;-ATPase activity in a variety of cells. The present experiments have been performed to elucidate whether or not wild-type SGK1, SGK2 and SGK3 are similar to &lt;sup&gt;S422D&lt;/sup&gt;SGK1 in being effective regulators of Na&lt;sup&gt;+&lt;/sup&gt;/K&lt;sup&gt;+&lt;/sup&gt;-ATPase. &lt;i&gt;Methods:&lt;/i&gt; To this end, dual-electrode voltage clamp experiments were performed in &lt;i&gt;Xenopus&lt;/i&gt; oocytes injected either with water or with mRNA of constitutively active &lt;sup&gt;S422D&lt;/sup&gt;SGK1 and wild-type SGK1, SGK2 or SGK3. Na&lt;sup&gt;+&lt;/sup&gt;/K&lt;sup&gt;+&lt;/sup&gt;-ATPase activity was estimated from the outward-directed current created by readdition of extracellular K&lt;sup&gt;+&lt;/sup&gt; in the presence of K&lt;sup&gt;+&lt;/sup&gt; channel blocker Ba&lt;sup&gt;2+&lt;/sup&gt; following a 10-min exposure to K&lt;sup&gt;+&lt;/sup&gt;-free extracellular fluid. &lt;i&gt;Results:&lt;/i&gt; The outward-directed current was fully abolished by incubation with 1 m&lt;i&gt;M&lt;/i&gt; ouabain and was significantly larger in oocytes expressing &lt;sup&gt;S422D&lt;/sup&gt;SGK1, SGK1, SGK2 or SGK3, as compared to those injected with water. &lt;i&gt;Conclusion:&lt;/i&gt; The stimulating effect of SGK1 on the &lt;i&gt;Xenopus&lt;/i&gt; oocyte Na&lt;sup&gt;+&lt;/sup&gt;/K&lt;sup&gt;+&lt;/sup&gt;-ATPase is mimicked by the isoforms SGK2 and SGK3. Thus, all three kinases may participate in the regulation of Na&lt;sup&gt;+&lt;/sup&gt;/K&lt;sup&gt;+&lt;/sup&gt;-ATPase activity by hormones such as insulin and IGF-1.</jats:p>