An evolutionarily conserved AnkyrinG-dependent motif clusters axonal K2P K+ channels

Area of Science:

• Neuroscience
• Molecular Biology
• Evolutionary Biology

Background:

• Ion channel clustering at nodes of Ranvier is crucial for vertebrate nervous system complexity.
• K+ leak channels TRAAK and TREK-1 are key for membrane repolarization at mammalian nodes.
• TRAAK and TREK-1 were thought to be node-specific, implying unique clustering mechanisms.

Purpose of the Study:

• To investigate the clustering mechanisms of TRAAK and TREK-1 at the axon initial segment (AIS) and nodes of Ranvier.
• To determine if a common mechanism underlies the localization of these channels at both neuronal domains.
• To elucidate the role of AnkyrinG in the clustering of TRAAK and TREK-1.

Main Methods:

• Utilized AnkyrinG (AnkG) conditional knockout mice.
• Employed CRISPR/Cas9 to disrupt AnkG.
• Performed co-immunoprecipitation and surface recruitment assays.

Main Results:

• TRAAK and TREK-1 are enriched at both AIS and nodes through a shared mechanism.
• A specific C-terminal motif in TRAAK is essential and sufficient for its clustering.
• AnkG is necessary for TRAAK's clustering at AIS and nodes, forming a complex with TRAAK.
• TREK-1 clustering depends on the presence of TRAAK.

Conclusions:

• AnkyrinG plays a central role in assembling excitable domains by clustering TRAAK and TREK-1.
• The findings expand the known mechanisms of ion channel clustering at AIS and nodes.
• The identified clustering mechanism involving AnkG evolved early, appearing in cartilaginous fish.