Differential role of the alpha1C subunit tails in regulation of the Cav1.2 channel by membrane potential, beta subunits, and Ca2+ ions

J Biol Chem. 2005 Apr 1;280(13):12474-85. doi: 10.1074/jbc.M412140200. Epub 2005 Jan 25.

Abstract

Voltage-gated Ca(v)1.2 channels are composed of the pore-forming alpha1C and auxiliary beta and alpha2delta subunits. Voltage-dependent conformational rearrangements of the alpha1C subunit C-tail have been implicated in Ca2+ signal transduction. In contrast, the alpha1C N-tail demonstrates limited voltage-gated mobility. We have asked whether these properties are critical for the channel function. Here we report that transient anchoring of the alpha1C subunit C-tail in the plasma membrane inhibits Ca2+-dependent and slow voltage-dependent inactivation. Both alpha2delta and beta subunits remain essential for the functional channel. In contrast, if alpha1C subunits with are expressed alpha2delta but in the absence of a beta subunit, plasma membrane anchoring of the alpha1C N terminus or its deletion inhibit both voltage- and Ca2+-dependent inactivation of the current. The following findings all corroborate the importance of the alpha1C N-tail/beta interaction: (i) co-expression of beta restores inactivation properties, (ii) release of the alpha1C N terminus inhibits the beta-deficient channel, and (iii) voltage-gated mobility of the alpha1C N-tail vis a vis the plasma membrane is increased in the beta-deficient (silent) channel. Together, these data argue that both the alpha1C N- and C-tails have important but different roles in the voltage- and Ca2+-dependent inactivation, as well as beta subunit modulation of the channel. The alpha1C N-tail may have a role in the channel trafficking and is a target of the beta subunit modulation. The beta subunit facilitates voltage gating by competing with the N-tail and constraining its voltage-dependent rearrangements. Thus, cross-talk between the alpha1C C and N termini, beta subunit, and the cytoplasmic pore region confers the multifactorial regulation of Ca(v)1.2 channels.

MeSH terms

  • Animals
  • COS Cells
  • Calcium / metabolism*
  • Calcium Channels, L-Type / chemistry*
  • Calcium Channels, L-Type / physiology*
  • Cell Membrane / metabolism
  • Cloning, Molecular
  • Cytoplasm / metabolism
  • Electrophysiology
  • Fluorescence Resonance Energy Transfer
  • Gene Deletion
  • Green Fluorescent Proteins / metabolism
  • Hippocampus / metabolism
  • Humans
  • Hydrolysis
  • Ions
  • Membrane Potentials*
  • Models, Biological
  • Nerve Tissue Proteins / chemistry*
  • Nerve Tissue Proteins / physiology*
  • Neurons / metabolism
  • Peptides / chemistry
  • Phenotype
  • Protein Binding
  • Protein Conformation
  • Protein Structure, Secondary
  • Protein Structure, Tertiary
  • Reverse Transcriptase Polymerase Chain Reaction
  • Signal Transduction
  • Time Factors

Substances

  • CACNA1C protein, human
  • Calcium Channels, L-Type
  • Ions
  • L-type calcium channel alpha(1C)
  • Nerve Tissue Proteins
  • Peptides
  • Green Fluorescent Proteins
  • Calcium