129-OR: Glycolytic Enzymes and Creatine Kinase Locally Regulate KATP Channel Activity in Both ß- and a-Cells

Abstract

The ATP-sensitive potassium channel (KATP) is a key regulator of membrane potential and islet hormone secretion. In ß-cells, it has been previously showed that the local activity of pyruvate kinase (PK) can sufficiently raise ATP/ADP to induce KATP closure, thus providing a another route to trigger membrane depolarization parallel to mitochondrial oxidative phosphorylation. Here, using direct single-channel measurements of KATP in both ß-and the lesser studied α-cells, we provide evidence for a larger network of metabolic enzymes that operate in the vicinity of KATP channels to fine-tune their activity. We found that the phosphofructokinase product fructose-1,6-bisphosphate (FBP), which oscillates in ß-cells, can induce KATP closure by its metabolism through the glycolytic chain including aldolase, GAPDH, phosphoglycerate kinase, phosphoglycerate mutase, enolase and finally PK. Strikingly, while withholding the substrates at GAPDH, we observed that FBP can independently inhibit KATP channels by direct action. In addition, we further provide evidence that creatine kinase (CK) activity can either oppose or enhance KATP closure, depending on the reaction direction. Finally, we demonstrated that lactate has an activating effect on KATP. In summary, these data provide evidence for the direct regulation of KATP by two metabolites, FBP and lactate, and identify two local ATP/ADP controllers, the glycolytic complex and the creatine kinase system in both ß-cells and α-cells. Disclosure T. Ho: None. E. Potapenko: None. M. J. Merrins: None.