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The CFTR chloride channel: nucleotide interactions and temperature-dependent gating
C J Mathews1, J A Tabcharani, J W Hanrahan
1Department of Physiology, McGill University, Montréal, Québec, Canada.
The Journal of Membrane Biology
|May 7, 1998
Summary
The study reveals how AMP-PNP affects Cystic Fibrosis Transmembrane conductance Regulator (CFTR) channel gating, indicating a second binding site and temperature-dependent mechanisms influencing channel function.
Area of Science:
- Molecular Biology
- Ion Channel Physiology
- Biochemistry
Background:
- The gating cycle of CFTR chloride channels is ATP-dependent.
- Non-hydrolyzable nucleotides like AMP-PNP can interrupt this cycle.
Purpose of the Study:
- To investigate the effects of AMP-PNP, PKC phosphorylation, and temperature on CFTR gating kinetics.
- To further characterize nucleotide interactions and their impact on CFTR channel gating.
Main Methods:
- Studied CFTR gating kinetics under varying AMP-PNP concentrations, in the presence of MgATP and PKA.
- Analyzed channel locking rates and open probability (Po) at different temperatures.
- Investigated the influence of protein kinase C (PKC) phosphorylation.
Main Results:
- AMP-PNP significantly increased channel locking rates, suggesting a second binding site.
- Strong PKA phosphorylation induced locking, but PKC alone did not.
- AMP-PNP increased Po above 30°C without causing locking, indicating weak domain interactions.
- CFTR gating by ATP showed asymmetric temperature dependence (opening rate Q10=9.6, closing rate Q10=3.6).
Conclusions:
- Results support a cyclic model for phosphorylated CFTR gating.
- AMP-PNP interactions at a second site influence CFTR gating kinetics.
- Temperature and phosphorylation state critically modulate CFTR channel activity.