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Extracellular K+ and intracellular pH allosterically regulate renal Kir1.1 channels
1Department of Sensory Biophysics, Ear-Nose-and-Throat Hospital of the University of Tübingen, Germany.
The Journal of Biological Chemistry
|July 19, 1996
Summary
Renal potassium (K+) channels (ROMK1) are directly regulated by extracellular K+ and intracellular pH. This novel allosteric regulation by ROMK1 channels links K+ homeostasis and pH control.
Area of Science:
- Physiology
- Molecular Biology
- Renal Physiology
Background:
- Renal tubular cells secrete potassium (K+) via apical channels, crucial for K+ homeostasis.
- Native apical K+ channels are indirectly regulated by basolateral K+ concentration via intracellular messengers.
- ROMK1, ROMK2, and ROMK3 are cloned renal apical K+ channel subtypes.
Purpose of the Study:
- To investigate direct regulation of ROMK1 (Kir1.1) channels by extracellular K+ concentration.
- To explore the coupling between extracellular K+ regulation and intracellular pH.
- To identify structural domains responsible for K+ regulation and pH coupling.
Main Methods:
- Site-directed mutagenesis of ROMK1 channels.
- Expression of wild-type and mutant ROMK1 channels in Xenopus oocytes.
- Electrophysiological recordings to assess channel activity.
- Chimeric channel construction by exchanging ROMK1 N terminus with IRK1 N terminus.
Main Results:
- ROMK1 channels are directly regulated by extracellular K+ concentration.
- This K+ regulation is coupled to intracellular pH.
- K+ regulation is mediated by the channel's core region (M1, M2, P region).
- Decoupling of K+ regulation from pH was achieved by replacing the ROMK1 N terminus with that of IRK1.
Conclusions:
- ROMK1 channels exhibit allosteric regulation by extracellular K+ and intracellular pH.
- Structural domains within ROMK1 mediate distinct regulatory functions.
- This finding suggests a novel mechanism linking renal K+ homeostasis and pH balance.