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Related Experiment Videos

Revisiting the role of Ca2+ in Shaker K+ channel gating.

K H Hong1, C M Armstrong, C Miller

  • 1Department of Biochemistry, Howard Hughes Medical Institute, Brandeis University, Waltham, Massachusetts 02454, USA.

Biophysical Journal
|April 28, 2001
PubMed
Summary

Extracellular calcium (Ca2+) is not essential for maintaining the function of Shaker K+ channels. Its removal causes minor shifts and leaks, which are patch-seal artifacts, not channel disruptions.

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Area of Science:

  • Molecular Biology
  • Neuroscience
  • Biophysics

Background:

  • Potassium (K+) channels are crucial for cellular electrical signaling.
  • Extracellular divalent cations, particularly calcium (Ca2+), are thought to stabilize ion channel function.
  • The specific role of Ca2+ in the gating and ion selectivity of Kv channels remains debated.

Purpose of the Study:

  • To investigate the necessity of extracellular Ca2+ for the proper gating and ion selectivity of Shaker K+ channels.
  • To determine if Ca2+ removal disrupts Kv channel function.

Main Methods:

  • Expression of Shaker K+ channels in Xenopus oocytes.
  • Recording from outside-out macropatches excised from these oocytes.
  • Systematic removal of extracellular Ca2+ using EDTA-containing solutions in the absence of intracellular divalent cations.

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Main Results:

  • Removal of extracellular Ca2+ induced a minor negative shift in the voltage-activation curve of Shaker K+ channels.
  • A significant nonselective leak current was observed under Ca2+-free conditions.
  • This leak was identified as a patch-seal artifact related to fluoride ions, not an intrinsic channel property.
  • The core gating and ion selectivity of the channels remained largely unaffected.

Conclusions:

  • Extracellular Ca2+ is not essential for maintaining the ion selectivity and proper gating of Shaker K+ channels.
  • Observed disruptions in channel function in Ca2+-free conditions are attributable to experimental artifacts.
  • These findings challenge previous hypotheses regarding the indispensable role of extracellular Ca2+ in Kv channel stability.