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Pull-down of Calmodulin-binding Proteins
07:51

Pull-down of Calmodulin-binding Proteins

Published on: January 23, 2012

Modulation of skeletal and cardiac voltage-gated sodium channels by calmodulin

Katharine A Young1, John H Caldwell

  • 1Campus Box 8315, Dept. of Cell/Devel Biology and the Neuroscience Program, UCHSC, PO Box 6511, Aurora, CO 80045, USA.

The Journal of Physiology
|March 5, 2005
PubMed

Insights

Calmodulin (CaM) directly interacts with muscle sodium channels (NaChs), modulating their voltage-dependent gating. This interaction, particularly involving the C-terminal domain and IQ domain, is crucial for regulating NaCh availability during muscle contraction.

Area of Science:

  • Molecular and Cellular Biology
  • Neuroscience
  • Physiology

Background:

  • Calmodulin (CaM) is a key calcium-binding protein that regulates numerous cellular processes.
  • Voltage-gated sodium channels (NaChs) are essential for electrical excitability in muscle and nerve cells.
  • CaM's role in modulating NaCh function, particularly in muscle, is an area of active investigation.

Purpose of the Study:

  • To investigate the interaction between Calmodulin (CaM) and skeletal (NaV1.4) and cardiac (NaV1.5) muscle sodium channels (NaChs).
  • To elucidate the specific domains of CaM and NaChs involved in their interaction.
  • To determine the functional consequences of CaM modulation on NaCh gating properties.

Main Methods:

  • Yeast two-hybrid assay to identify protein-protein interactions.
  • Transient expression of wild-type and mutant sodium channels in CHO cells.
  • Electrophysiological recordings to assess channel gating kinetics.
  • Site-directed mutagenesis of CaM and NaChs.

Main Results:

  • CaM directly interacts with the C-terminal domains of NaV1.4 and NaV1.5.
  • CaM coexpression induced hyperpolarizing shifts in NaV1.4 activation/inactivation and NaV1.5 activation.
  • Mutations in the NaCh IQ domain and specific CaM N-terminal lobe mutations disrupted CaM's effects.
  • CaM's action on NaV1.4 is direct, not mediated by CaM-kinase II.

Conclusions:

  • Calmodulin directly binds to and modulates the gating of muscle sodium channels.
  • The C-terminal domain of NaChs and the N-terminal lobe of CaM are critical for this interaction.
  • CaM-mediated regulation of NaChs is important for controlling muscle excitability during physiological events like contraction.

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