Sulfonylurea receptor 1 subunit of ATP-sensitive potassium channel (SUR1)

The **sulfonylurea receptor 1** (**SUR1**) is a regulatory subunit integral to the function of ATP-sensitive potassium (K_ATP) channels. These channels are octameric complexes composed of four pore-forming Kir6.x-type inward rectifier potassium channels—most commonly Kir6.2—and four regulatory SUR subunits. The most prominent physiological role for the combination Kir6.2/SUR1 occurs in pancreatic beta cells where it couples glucose metabolism with membrane excitability, thereby regulating insulin secretion. When intracellular ATP levels rise following glucose uptake/metabolism, ATP binds directly to Kir6.2 causing closure of the K_ATP channel; this depolarizes the cell membrane and triggers calcium influx leading to insulin exocytosis. Conversely, MgADP binding at SUR1 stimulates opening under low-energy conditions. SUR1 belongs structurally and functionally to the ABC transporter family but does not transport substrates across membranes—instead it regulates ion flow through its interaction with nucleotides/drugs at distinct binding sites that modulate gating behavior via allosteric mechanisms between itself and Kir6.x partners[5]. Clinically important drugs such as sulfonylureas exploit these properties by binding specifically at sites within SUR1’s transmembrane domains—leading ultimately either toward enhanced or suppressed electrical activity depending on drug class. Mutations affecting either expression or function can result in disorders ranging from persistent hypoglycemic states (congenital hyperinsulinism) when overactive/overexpressed—to various forms of monogenic diabetes when underactive/lost-of-function mutations occur.[4] In addition, emerging evidence implicates roles for cardiac-expressed variants during ischemia/reperfusion injury responses.[3]

Other names

Sulfonylurea receptor 1SUR1ABCC8 (gene symbol)ATP-binding cassette transporter sub-family C member 8

For drugs targeting SUR1: - Sulfonylureas bind to SUR1, causing closure of the K_ATP channel by promoting Kir6.2 pore closure; this leads to depolarization and increased insulin release from pancreatic beta cells[6]. - Diazoxide binds SUR1 but stabilizes the open state of the K_ATP channel, leading to hyperpolarization and reduced insulin secretion. - Some drugs act as K_ATP channel openers or blockers depending on their interaction with SUR domains.