Voltage-gated K+ channels contain multiple intersubunit association sites

Area of Science:

• Molecular Biology
• Neuroscience
• Biophysics

Background:

• Voltage-gated K+ channels assemble into tetramers for proper function.
• A known tetramerization domain (T1) is located in the cytoplasmic NH2 terminus.
• Kv1.3 channels lacking the T1 domain can still form functional channels, suggesting other oligomerization sites exist.

Purpose of the Study:

• To identify and characterize additional subunit association sites in the central core of Kv1.3 channels.
• To investigate the role of these sites in channel oligomerization and function.

Main Methods:

• Co-injection of cRNA encoding Kv1.3 (T1(-)) deletion mutants and fragments into Xenopus oocytes.
• Electrophysiological recordings to measure K+ channel current suppression.
• In vivo immunoprecipitation and pulse-chase experiments to validate fragment effects and assess translation/degradation.
• Co-immunoprecipitation to confirm direct fragment-channel interactions.

Main Results:

• Specific Kv1.3 (T1(-)) fragments (S1-S2-S3, S3-S4-S5, S2-COOH, S3-COOH) significantly suppressed Kv1.3 (T1(-)) current.
• Suppression was due to direct association of fragments with Kv1.3 (T1(-)), not altered translation or degradation.
• These suppressive fragments also inhibited an analogous mutant Kv2.1 channel (Kv2.1 (DeltaN139)).

Conclusions:

• Kv1.3 channels possess subunit association sites within their central core, independent of the T1 domain.
• These central core sites mediate inter-subunit association and function as suppressors of channel activity.
• The identified suppression sites are promiscuous, affecting different subfamilies of voltage-gated K+ channels.