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Elementary functional properties of single HCN2 channels.
S Thon1, R Schmauder, K Benndorf
1Institute of Physiology II, University Hospital Jena, Jena, Germany.
Biophysical Journal
|October 8, 2013
Summary
Single Hyperpolarization-activated Cyclic-Nucleotide-Gated (HCN)2 channels exhibit low conductance. Voltage and cAMP exclusively control channel opening probability, with no observed interchannel cooperativity.
Area of Science:
- Biophysics
- Molecular Biology
- Neuroscience
Background:
- Hyperpolarization-activated cyclic-nucleotide-gated (HCN) channels are crucial for rhythmic electrical activity in neurons and cardiac cells.
- These channels are modulated by voltage and cAMP, but their fundamental properties remain poorly understood.
Purpose of the Study:
- To elucidate the elementary functional properties of single HCN2 channels.
- To investigate the roles of voltage and cAMP in HCN2 channel gating.
Main Methods:
- Single-channel patch-clamp recordings in Xenopus oocytes expressing homotetrameric HCN2 channels.
- Analysis of single-channel conductance, activation kinetics, and open probability.
Main Results:
- HCN2 channels possess a low single-channel conductance (1.67 pS).
- Channel activation is a one-step process governed by the first latency.
- Voltage and cAMP independently control the open probability, which can approach unity at maximum activation.
- No interchannel cooperativity was detected.
Conclusions:
- Single HCN2 channels operate with exceptionally low conductance.
- Voltage and cAMP exclusively regulate the open probability of HCN2 channels.
- Findings clarify fundamental HCN channel gating mechanisms.
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