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Pull-down of Calmodulin-binding Proteins
07:51

Pull-down of Calmodulin-binding Proteins

Published on: January 23, 2012

Calmodulin-dependent activation and inactivation of anoctamin calcium-gated chloride channels

Kerstin Vocke1, Kristin Dauner, Anne Hahn

  • 1Department of Molecular Physiology, Centre for Organismal Studies, Heidelberg University, 69120 Heidelberg, Germany.

The Journal of General Physiology
|October 2, 2013
PubMed

Insights

Calcium-activated chloride channels ANO 1 and ANO 2 are regulated by calmodulin binding to a specific N-terminal domain. This interaction controls channel activation and, in ANO 2, calcium-dependent inactivation in neurons.

Area of Science:

  • Molecular biology
  • Cell physiology
  • Neuroscience

Background:

  • Calcium-dependent chloride channels are crucial for cellular functions.
  • The anoctamin (ANO) family, including ANO 1 (TMEM16A) and ANO 2 (TMEM16B), encodes key calcium-activated chloride channels.
  • Understanding the precise mechanisms of calcium-dependent regulation is vital for their physiological roles.

Purpose of the Study:

  • To investigate the interaction between ANO 1 and ANO 2 channels and Ca(2+)/calmodulin.
  • To identify the specific domains involved in this calcium-dependent regulation.
  • To elucidate the functional consequences of this interaction, including channel activation and inactivation.

Main Methods:

  • Nonstationary current analysis during channel activation.
  • Peptide binding studies to identify calmodulin-binding domains.
  • Functional, structural, and pharmacological analyses.
  • Site-directed mutagenesis to probe domain function.

Main Results:

  • A regulatory calmodulin-binding motif (RCBM) in the N-terminal region of ANO 1 and ANO 2 was identified.
  • The RCBM mediates two distinct modes of Ca(2+)/calmodulin interaction at different calcium concentrations.
  • Calmodulin acts as a stably associated calcium sensor regulating channel activation.
  • ANO 2 exhibits Ca(2+)/calmodulin-dependent inactivation, particularly in its brain splice variant, which is mediated by the RCBM.
  • Inactivation is suppressed in the retinal ANO 2 splice variant.

Conclusions:

  • Calmodulin is a key regulator of ANO 1 and ANO 2 channel activity through its interaction with the N-terminal RCBM.
  • The RCBM plays a dual role in channel activation and, for ANO 2, calcium-dependent inactivation.
  • ANO 2 inactivation may limit channel activity during sustained neuronal calcium signals.
  • These findings enhance the understanding of calcium signaling in anoctamin channel function in various cell types, including neurons.

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