Related Experiment Video
Updated: May 7, 2026
10:08
Study of the Functions and Activities of Neuronal K-Cl Co-Transporter KCC2 Using Western Blotting
Published on: December 9, 2022
The relationship between functional inhibition and binding for K(Ca)2 channel blockers
David Charles Hammond Benton1, Monique Garbarg, Guy William John Moss
1Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom.
Plos One
|September 17, 2013
Summary
Apamin
Area of Science:
- Ion channel pharmacology
- Molecular biophysics
Background:
- Small conductance calcium-activated potassium channels (KCa2) are targets for peptide toxins like apamin and small molecule blockers.
- Discrepancies exist between apamin's binding affinity and its electrophysiological block of KCa2 subtypes.
Purpose of the Study:
- To investigate if differing ionic conditions explain the discrepancy between apamin binding and block data for KCa2 channels.
- To re-evaluate apamin's subtype selectivity under consistent experimental conditions.
Main Methods:
- (125)I-apamin binding assays and electrophysiological current block measurements were performed on HEK 293 cells expressing KCa2 channels.
- Experiments were conducted under both normal physiological ionic conditions and non-physiological Ca(2+)/Mg(2+)-free conditions.
Main Results:
- Apamin binding and block data for KCa2 channels showed good agreement under normal physiological ionic conditions.
- Apamin exhibited subtype selectivity in binding (K L values for KCa2.2 vs. KCa2.3) and block (IC50 values) when measured in physiological solutions.
- Under non-physiological conditions mimicking prior binding studies, apamin's IC50 for KCa2.2 block decreased significantly.
Conclusions:
- The apparent discrepancy in apamin's affinity and block potency for KCa2 subtypes is largely attributable to the use of non-physiological ionic conditions in previous binding studies.
- Apamin demonstrates subtype selectivity for KCa2 channels when assessed under physiologically relevant conditions.
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