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TWIK1, a unique background channel with variable ion selectivity.

Franck C Chatelain1, Delphine Bichet, Dominique Douguet

  • 1Institut de Pharmacologie Moléculaire et Cellulaire, Centre National de la Recherche Scientifique, and Université de Nice Sophia Antipolis, 06560 Valbonne, France.

Proceedings of the National Academy of Sciences of the United States of America
|March 21, 2012
PubMed
Summary
This summary is machine-generated.

TWIK1 potassium channels change ion selectivity based on pH. They conduct sodium in acidic endosomes, influencing cell excitability and demonstrating pH-dependent channel function.

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Area of Science:

  • Physiology
  • Molecular Biology
  • Ion Channel Function

Background:

  • TWIK1 (Tweak-related inwardly-rectifying potassium channel 1) is a background potassium channel.
  • TWIK1 is primarily localized to recycling endosomes in cells.
  • Previous studies linked TWIK1 gene inactivation in kidney cells to altered cationic conductance, attributed to adaptive channel regulation.

Purpose of the Study:

  • To investigate the influence of extracellular pH on TWIK1 ion selectivity.
  • To explore the functional implications of pH-dependent selectivity in cellular processes.

Main Methods:

  • Utilized electrophysiological recordings to assess ion channel function.
  • Investigated TWIK1 behavior across different extracellular pH conditions, including acidic and neutral environments.
  • Examined TWIK1 activity in both native and transfected cells, as well as in genetically modified models (TWIK1-/-).

Main Results:

  • TWIK1 exhibits pH-dependent ion selectivity, being permeable to Na+ at acidic pH (endosomal conditions) but K+ selective at neutral pH.
  • The recovery of K+ selectivity after exposure to acidic pH is slow, indicating hysteresis.
  • TWIK1 knockout pancreatic β cells show increased polarization, supporting a depolarizing role for TWIK1 in kidney and pancreatic cells.

Conclusions:

  • TWIK1 functions as a pH-sensitive background channel whose ion selectivity is modulated by its cellular environment.
  • The observed hysteresis in selectivity suggests a role in regulating cell excitability based on its trafficking between acidic endosomes and the plasma membrane.
  • TWIK1 plays a significant role in modulating the excitability of kidney and pancreatic β cells through its pH-dependent properties.