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Modeling interactions between voltage-gated Ca (2+) channels and KCa1.1 channels.
Jordan Dt Engbers1, Gerald W Zamponi2, Ray W Turner3
1Department of Cell Biology & Anatomy; Hotchkiss Brain Institute; University of Calgary; Calgary, Canada.
Channels (Austin, Tex.)
|August 10, 2013
Summary
Low voltage-activated calcium channels (Cav3) require multiple complexes to activate KCa1.1 channels, unlike high voltage-activated channels. This suggests cooperative microdomain interactions are key for Cav3-mediated KCa1.1 regulation.
Area of Science:
- Ion channel biophysics
- Molecular and cellular physiology
- Computational neuroscience
Background:
- High voltage-activated (HVA) Cav channels form nanodomain complexes with KCa1.1 channels for activation.
- Low voltage-activated (LVA) Cav3 channels also associate with KCa1.1 channels, but their interaction dynamics differ.
- Previous studies suggested nanodomain interaction for KCa1.1-Cav3 complexes, yet calcium chelator sensitivity indicated microdomain interaction.
Purpose of the Study:
- To computationally model and compare KCa1.1 channel activation by Cav3 versus Cav2.2 calcium channels.
- To investigate the role of calcium channel conductance and kinetics in KCa1.1 activation within these complexes.
- To elucidate the spatial and cooperative requirements for KCa1.1 activation by LVA Cav3 channels.
Main Methods:
- Expanded computational models of KCa1.1-Cav3 complexes.
- Developed and analyzed a computational model for KCa1.1-Cav2.2 complexes.
- Compared voltage-dependence, kinetics, and calcium domain requirements for KCa1.1 activation by different Cav channel subtypes.
Main Results:
- Cav3 channel properties, including transient activation at lower voltages, influenced KCa1.1 current activation.
- Multiple Cav3.2 channels were necessary for substantial KCa1.1 activation, consistent with microdomain interactions.
- Single Cav2.2 channels were sufficient for KCa1.1 activation, demonstrating efficient nanodomain interaction.
Conclusions:
- KCa1.1-Cav3 complexes require cooperation among multiple Cav3 channels via microdomain interactions for sufficient calcium signaling.
- Cav2.2 channels activate KCa1.1 channels more effectively through self-sufficient nanodomain interactions.
- Regulation of KCa1.1 by Cav3 channels is feasible through cooperative microdomain interactions, despite transient and localized calcium currents.
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