Molecular physiology of neuronal K-ATP channels (review).

ATP sensitive potassium (K-ATP) channels are widely expressed in many cell types including neurons. K-ATP channels are heteromeric membrane proteins that consist of two very different subunits: the pore-forming, two-transmembrane spanning potassium channel subunit (Kir6) and the regulatory, 17 transmembrane spanning sulphonylurea receptor (SUR). This ensemble--joined together in a 4:4 stoichiometry--endows this channel with a unique combination of functional properties. The open probability of K-ATP channels directly depends on the intracellular ATP/ADP levels allowing the channels to directly couple the metabolic state of a cell to its electrical activity. Here, recent progress on the molecular composition and functional diversity of neuronal K-ATP channels is reviewed. One is particular concerned with single-cell mRNA expression studies that give insight to the coexpression patterns of Kir6 and SUR isoforms in identified neurons. In addition, the physiological roles of neuronal K-ATP channels in glucose sensing and adapting neuronal activity to metabolic demands are discussed, as well as their emerging pathophysiological functions in acute brain ischemia and chronic neurodegenerative diseases.