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Na,K-ATPase as a signal transducer
1Department of Woman and Child Health, Karolinska Institutet, Astrid Lindgren Children's Hospital, Stockholm, Sweden.
Annals of the New York Academy of Sciences
|May 24, 2003
Summary
The sodium-potassium pump (Na,K-ATPase) acts as a signal transducer, triggering calcium oscillations and NF-kappaB activation in rat kidney cells. This signaling pathway involves IP3 receptors, not phospholipase C.
Area of Science:
- Biochemistry
- Cell Biology
- Physiology
Background:
- Na,K-ATPase is crucial for maintaining ion homeostasis.
- The signaling role of Na,K-ATPase and its ligand ouabain is not fully understood.
- Ouabain's effects on intracellular calcium and downstream signaling pathways require elucidation.
Purpose of the Study:
- To investigate the role of Na,K-ATPase as a signal transducer.
- To elucidate the mechanism of ouabain-induced calcium signaling in rat proximal tubular cells (RPTC).
- To determine the downstream effects of ouabain-induced calcium signals, including NF-kappaB activation.
Main Methods:
- Exposure of RPTC to varying doses of ouabain.
- Measurement of intracellular calcium ([Ca(2+)](i)) oscillations.
- Inhibition studies using IP3 receptor blockers and phospholipase C inhibitors.
- Cellular depletion of IP3.
- Fluorescence resonance energy transfer (FRET) to assess proximity between Na,K-ATPase and IP3 receptors.
Main Results:
- Low doses of ouabain (10 nM - 500 micro M) induced intracellular calcium oscillations in RPTC.
- These calcium oscillations led to the activation of the transcription factor NF-kappaB.
- Ouabain-induced calcium oscillations were inhibited by IP3 receptor blockers but not by phospholipase C inhibitors or IP3 depletion.
- FRET studies indicated close proximity between Na,K-ATPase and IP3 receptors.
Conclusions:
- Na,K-ATPase functions as a signal transducer, initiating calcium signaling.
- Ouabain triggers calcium oscillations via IP3 receptors, independent of phospholipase C.
- A novel signaling pathway involving Na,K-ATPase and IP3 receptors in calcium regulation is demonstrated.
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