A novel calmodulin site in the Cav1.2 N-terminus regulates calcium-dependent inactivation

Pflugers Arch. 2014 Sep;466(9):1793-803. doi: 10.1007/s00424-013-1423-9. Epub 2013 Dec 19.

Abstract

The L-type voltage-gated calcium channel Cav1.2 is important for excitation-contraction coupling in the heart, as well as CREB-mediated transcription in the brain. The ubiquitous calcium-binding protein calmodulin (CaM) is known to modulate calcium-dependent inactivation (CDI) of these channels, thus limiting the amount of calcium entering via Cav1.2 during prolonged or repetitive membrane depolarizations. The proximal N-terminus of Cav1.2 contains a CaM-binding site at residue W52 that is critical for a type of CDI that is mediated by the N-terminal lobe of CaM. Here, we identify a second CaM interaction site in the Cav1.2 N-terminus downstream of the W52 site that is formed by residue C106. We show by site-directed mutagenesis coupled with electrophysiological measurements that this region of the channel functionally partakes in N-lobe CDI, likely by acting as a gating transduction motif. Thus, our data indicate that calcium regulation of Cav1.2 channels is more complex than previously thought, and involves more than one region within the channel's N-terminal domain.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Binding Sites / physiology
  • Calcium / metabolism*
  • Calcium Channels, L-Type / metabolism*
  • Calmodulin / metabolism*
  • Cell Line
  • Humans
  • Immunoblotting
  • Microscopy, Confocal
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Patch-Clamp Techniques
  • Protein Structure, Tertiary
  • Rats
  • Transfection

Substances

  • Cacna1c protein, rat
  • Calcium Channels, L-Type
  • Calmodulin
  • Calcium