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A view of sur/KIR6.X, KATP channels
A P Babenko1, L Aguilar-Bryan, J Bryan
1Department of Cell Biology, Baylor College of Medicine, Houston, Texas 77030, USA.
Annual Review of Physiology
|April 29, 1998
Summary
ATP-sensitive potassium channels (KATP channels) are crucial for cell metabolism and electrical activity. Mutations in these channels, specifically SUR1 and KIR6.2, cause familial hyperinsulinism, offering insights into channel function.
Area of Science:
- Molecular Biology
- Cell Physiology
- Biochemistry
Background:
- ATP-sensitive potassium channels (KATP channels) are vital membrane proteins that couple cellular energy status to electrical activity.
- These channels are heteromultimers composed of sulfonylurea receptor (SUR) and inward rectifier potassium channel (KIR6.X) subunits, forming a tetrameric structure with a 1:1 stoichiometry.
- KATP channel activity is regulated by intracellular ATP and ADP concentrations, with different SUR and KIR6.X subunit combinations conferring distinct properties.
Purpose of the Study:
- To elucidate the structural and functional diversity of KATP channels arising from various SUR and KIR6.X subunit assemblies.
- To investigate the molecular basis of familial hyperinsulinism caused by mutations in SUR1 and KIR6.2 subunits.
- To understand how KATP channel function is modulated by nucleotides, sulfonylureas, and potassium channel openers (KCOs).
Main Methods:
- Analysis of KATP channel subunit composition (SUR and KIR6.X subtypes).
- Characterization of channel properties, including unitary conductance and sensitivity to pharmacological agents (sulfonylureas, diazoxide, KCOs).
- Identification and study of mutations in SUR1 and KIR6.2 associated with familial hyperinsulinism.
Main Results:
- KIR6.1-based channels exhibit smaller unitary conductance compared to KIR6.2-based channels.
- SUR1- and SUR2-based channels display differential sensitivity to sulfonylureas, while SUR2A and SUR2B subtypes differ in their diazoxide sensitivity.
- Loss-of-function mutations in SUR1 and KIR6.2 are identified as causative for familial hyperinsulinism.
Conclusions:
- The diversity of KATP channels is determined by the specific combination of SUR and KIR6.X subunits, leading to distinct biophysical and pharmacological properties.
- Mutations in KATP channel subunits, particularly SUR1 and KIR6.2, disrupt channel function and lead to metabolic disorders like familial hyperinsulinism.
- Understanding these mutations provides critical insights into the regulation of KATP channels by cellular metabolites and therapeutic agents.