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Competitive modulation of KV1.2 gating by LMAN2 and Slc7a5
Damayantee Das1, Shawn M Lamothe1, Anson A Wong1
1Department of Pharmacology, Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada.
Summary
The neutral amino acid transporter Slc7a5 and transmembrane lectin LMAN2 regulate KV1.2 channels. They compete for interaction with the voltage sensor, creating complex gating when co-expressed.
Area of Science:
- Neuroscience
- Molecular Biology
- Ion Channel Physiology
Background:
- Potassium channels, specifically KV1.2, are crucial for regulating neuronal excitability in the central nervous system (CNS).
- While KV1.2 structure and function are understood, mechanisms of regulation by auxiliary proteins like Slc7a5 and LMAN2 are less clear.
- Previous work identified Slc7a5 as a hyperpolarizing regulator and LMAN2 as a depolarizing regulator of KV1.2.
Purpose of the Study:
- To investigate the functional interaction between LMAN2 and Slc7a5 in modulating KV1.2 channel gating.
- To identify the specific structural regions of KV1.2 responsible for sensitivity to Slc7a5 and LMAN2.
- To elucidate the competitive interaction between these regulators on KV1.2 voltage dependence.
Main Methods:
- Co-expression of KV1.2 with either Slc7a5 or LMAN2 to assess gating properties.
- Utilizing a KV1.2:1.5 chimeric approach to map regulatory interaction sites.
- Site-directed mutagenesis by replacing specific segments within the KV1.2 voltage-sensing domain with homologous regions from KV1.5.
Main Results:
- Co-expression of LMAN2 and Slc7a5 with KV1.2 resulted in bi-modal voltage-dependence, indicating distinct channel populations.
- Specific regions within the S1 to S3 segments of the KV1.2 voltage-sensing domain were identified as critical for Slc7a5 and LMAN2 sensitivity.
- Selective abolition of regulator sensitivity was achieved by replacing these segments with KV1.5 sequences.
Conclusions:
- Slc7a5 and LMAN2 exhibit a competitive interaction for binding to the KV1.2 voltage sensor.
- This competition leads to complex, bi-modal voltage-dependence of KV1.2 channel activity when both regulators are present.
- The S1-S3 segments of the voltage-sensing domain are key determinants of differential regulation by Slc7a5 and LMAN2.
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