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Dominant-negative suppression of Cav2.1 currents by alpha(1)2.1 truncations requires the conserved interaction domain

Robert S Raike1, Holly B Kordasiewicz, Randall M Thompson

  • 1Department of Neurology, University of Minnesota, Minneapolis, MN 55455, USA.

Molecular and Cellular Neurosciences
|December 13, 2006
PubMed

Insights

Mutations in CACNA1A cause episodic ataxia type 2 (EA2) by producing truncated Ca(v)2.1 channel subunits. These truncations impair channel function, suggesting Ca(v) beta subunits are key in EA2.

Area of Science:

  • Neuroscience
  • Molecular Biology
  • Genetics

Background:

  • Episodic ataxia type 2 (EA2) is an inherited neurological disorder.
  • It results from mutations in the CACNA1A gene, leading to abnormal Ca(v)2.1 calcium channels.

Purpose of the Study:

  • To investigate the hypothesis that truncated alpha(1)2.1 subunits in EA2 exert dominant-negative effects on wild-type subunits.
  • To elucidate the role of Ca(v) beta subunits in EA2 pathogenesis.

Main Methods:

  • Co-expression of wild-type and truncated alpha(1)2.1 subunits with fluorescent tags in cells expressing Ca(v) auxiliary beta subunits.
  • Measurement of whole-cell currents using electrophysiology.
  • Cellular image analyses and co-immunoprecipitation to assess protein expression and interactions.

Main Results:

  • Co-expression of truncated subunits with wild-type subunits significantly reduced whole-cell currents.
  • Current suppression was linked to truncations distal to the alpha interaction domain (AID), not reduced wild-type expression.
  • Ca(v) beta subunits co-immunoprecipitated only with AID-bearing alpha(1)2.1 proteins.

Conclusions:

  • Truncated alpha(1)2.1 subunits in EA2 impair Ca(v)2.1 channel function through a dominant-negative mechanism.
  • The interaction between alpha(1)2.1 subunits and Ca(v) beta subunits, particularly via the AID, is critical for channel function.
  • Ca(v) beta subunits likely play a significant role in the pathogenesis of EA2.

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