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Spermine and spermidine as gating molecules for inward rectifier K+ channels
E Ficker1, M Taglialatela, B A Wible
1Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX 77030.
Science (New York, N.Y.)
|November 11, 1994
Summary
Inward rectifier K+ channels are blocked by intracellular Mg2+ and polyamines like spermine and spermidine. These polyamines may be responsible for the channels' intrinsic gating, influencing ion flow.
Area of Science:
- Biophysics
- Molecular Biology
- Ion Channel Physiology
Background:
- Inward rectifier K+ channels exhibit strong inward currents and blocked outward currents.
- Inward rectification is attributed to intracellular Mg2+ block and an intrinsic gating mechanism.
- Loss of gating in excised patches indicates involvement of cytoplasmic factors.
Purpose of the Study:
- To investigate the role of cytoplasmic factors in the intrinsic gating of inward rectifier K+ channels.
- To identify specific cytoplasmic molecules responsible for restoring intrinsic gating.
Main Methods:
- Patch-clamp electrophysiology on excised membrane patches.
- Application of polyamines (spermine, spermidine) to excised patches.
- Analysis of channel gating kinetics and current-voltage relationships.
Main Results:
- Intrinsic gating was lost in excised patches but could be restored by nanomolar concentrations of spermine and spermidine.
- Polyamines spermine and spermidine effectively mimicked the effects of endogenous cytoplasmic factors.
- Results suggest polyamines act as physiological blockers for inward rectifier K+ channels.
Conclusions:
- Spermine and spermidine are likely physiological blockers of inward rectifier K+ channels.
- The "intrinsic" gating of these channels may primarily result from voltage-dependent block by polyamines.
- Understanding polyamine interactions is crucial for comprehending K+ channel function.