National Institutes of Health/National Institute of Diabetes and Digestive and Kidney Disease (NIH/NIDDK)
United States
Citation
Journal: Elife / Year: 2019 Title: Mechanism of pharmacochaperoning in a mammalian K channel revealed by cryo-EM. Authors: Gregory M Martin / Min Woo Sung / Zhongying Yang / Laura M Innes / Balamurugan Kandasamy / Larry L David / Craig Yoshioka / Show-Ling Shyng / Abstract: ATP-sensitive potassium (K) channels composed of a pore-forming Kir6.2 potassium channel and a regulatory ABC transporter sulfonylurea receptor 1 (SUR1) regulate insulin secretion in pancreatic β- ...ATP-sensitive potassium (K) channels composed of a pore-forming Kir6.2 potassium channel and a regulatory ABC transporter sulfonylurea receptor 1 (SUR1) regulate insulin secretion in pancreatic β-cells to maintain glucose homeostasis. Mutations that impair channel folding or assembly prevent cell surface expression and cause congenital hyperinsulinism. Structurally diverse K inhibitors are known to act as pharmacochaperones to correct mutant channel expression, but the mechanism is unknown. Here, we compare cryoEM structures of a mammalian K channel bound to pharmacochaperones glibenclamide, repaglinide, and carbamazepine. We found all three drugs bind within a common pocket in SUR1. Further, we found the N-terminus of Kir6.2 inserted within the central cavity of the SUR1 ABC core, adjacent the drug binding pocket. The findings reveal a common mechanism by which diverse compounds stabilize the Kir6.2 N-terminus within SUR1's ABC core, allowing it to act as a firm 'handle' for the assembly of metastable mutant SUR1-Kir6.2 complexes.
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