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A sensory neuron-specific, proton-gated ion channel
C C Chen1, S England, A N Akopian
1Molecular Nociception Group, Department of Biology, Medawar Building, University College, Gower Street, London WC1E 6BN, United Kingdom.
Summary
Researchers identified a novel acid-sensing ionic channel splice variant, ASIC-beta, in sensory neurons. This distinct channel, ASIC-beta, may play a specialized role in pain signaling due to its unique properties and distribution.
Area of Science:
- Neuroscience
- Molecular Biology
- Ion Channel Physiology
Background:
- Proton-gated channels in sensory neurons are implicated in pain perception, particularly under low pH conditions.
- Acid-sensing ionic channels (ASICs) and dorsal root ASICs (DRASICs) are known members of the amiloride-sensitive ENaC/Degenerin family expressed in sensory neurons.
Purpose of the Study:
- To clone and characterize a novel splice variant of acid-sensing ionic channels, designated ASIC-beta.
- To investigate the unique molecular, expression, and functional properties of ASIC-beta in sensory neurons.
Main Methods:
- Cloning and sequencing of the ASIC-beta splice variant.
- Analysis of ASIC-beta transcript distribution in rat dorsal root ganglion neurons.
- Heterologous expression of ASIC-beta in COS-7 cells and characterization of its electrophysiological properties, including pH dependency, amiloride sensitivity, and ion permeability.
Main Results:
- ASIC-beta possesses unique N-terminal and untranslated sequences compared to ASIC and DRASIC.
- ASIC-beta expression is restricted to a subset of sensory neurons and absent from sympathetic neurons and the central nervous system.
- Functional ASIC-beta channels exhibit distinct electrophysiological properties, including calcium impermeability and lack of inhibition by extracellular calcium, despite similar pH sensitivity and amiloride response to ASIC.
Conclusions:
- ASIC-beta represents a novel functional splice variant of proton-gated channels in sensory neurons.
- The unique expression pattern and functional characteristics of ASIC-beta suggest a specialized role in sensory neuron function, potentially distinct from ASIC and DRASIC.