Low voltage activation of KCa1.1 current by Cav3-KCa1.1 complexes

PLoS One. 2013 Apr 23;8(4):e61844. doi: 10.1371/journal.pone.0061844. Print 2013.

Abstract

Calcium-activated potassium channels of the KCa1.1 class are known to regulate repolarization of action potential discharge through a molecular association with high voltage-activated calcium channels. The current study examined the potential for low voltage-activated Cav3 (T-type) calcium channels to interact with KCa1.1 when expressed in tsA-201 cells and in rat medial vestibular neurons (MVN) in vitro. Expression of the channel α-subunits alone in tsA-201 cells was sufficient to enable Cav3 activation of KCa1.1 current. Cav3 calcium influx induced a 50 mV negative shift in KCa1.1 voltage for activation, an interaction that was blocked by Cav3 or KCa1.1 channel blockers, or high internal EGTA. Cav3 and KCa1.1 channels coimmunoprecipitated from lysates of either tsA-201 cells or rat brain, with Cav3 channels associating with the transmembrane S0 segment of the KCa1.1 N-terminus. KCa1.1 channel activation was closely aligned with Cav3 calcium conductance in that KCa1.1 current shared the same low voltage dependence of Cav3 activation, and was blocked by voltage-dependent inactivation of Cav3 channels or by coexpressing a non calcium-conducting Cav3 channel pore mutant. The Cav3-KCa1.1 interaction was found to function highly effectively in a subset of MVN neurons by activating near -50 mV to contribute to spike repolarization and gain of firing. Modelling data indicate that multiple neighboring Cav3-KCa1.1 complexes must act cooperatively to raise calcium to sufficiently high levels to permit KCa1.1 activation. Together the results identify a novel Cav3-KCa1.1 signaling complex where Cav3-mediated calcium entry enables KCa1.1 activation over a wide range of membrane potentials according to the unique voltage profile of Cav3 calcium channels, greatly extending the roles for KCa1.1 potassium channels in controlling membrane excitability.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Action Potentials / physiology
  • Amino Acid Sequence
  • Animals
  • Calcium / metabolism*
  • Calcium Channel Blockers / pharmacology
  • Caveolin 3 / genetics
  • Caveolin 3 / metabolism*
  • Cell Line, Transformed
  • Gene Expression
  • Humans
  • Large-Conductance Calcium-Activated Potassium Channel alpha Subunits / genetics
  • Large-Conductance Calcium-Activated Potassium Channel alpha Subunits / metabolism*
  • Models, Molecular
  • Molecular Sequence Data
  • Mutation
  • Neurons / cytology
  • Neurons / drug effects
  • Neurons / metabolism*
  • Patch-Clamp Techniques
  • Protein Structure, Tertiary
  • Protein Subunits / genetics
  • Protein Subunits / metabolism*
  • Rats
  • Signal Transduction / physiology*
  • Vestibular Nuclei / cytology
  • Vestibular Nuclei / drug effects
  • Vestibular Nuclei / metabolism*

Substances

  • CAV3 protein, human
  • Calcium Channel Blockers
  • Caveolin 3
  • KCNMA1 protein, human
  • Large-Conductance Calcium-Activated Potassium Channel alpha Subunits
  • Protein Subunits
  • Calcium

Grant support

GWZ holds a Canada Research Chair. RR received studentship support from AIHS and the National Sciences and Engineering Research Council, with Postdoctoral Fellowships from AIHS (GB, TB) and CIHR (TB). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.