A plasma membrane-associated glycolytic metabolon is functionally coupled to KATPchannels in pancreatic α and β cells from humans and mice

Abstract

SummaryThe ATP-sensitive K+channel (KATP) is a key regulator of hormone secretion from pancreatic islet endocrine cells. Using direct measurements of KATPchannel activity in pancreatic β cells and the lesser-studied α cells, from both humans and mice, we demonstrate that a glycolytic metabolon locally controls KATPchannels on the plasma membrane. The two ATP-consuming enzymes of upper glycolysis, glucokinase and phosphofructokinase, generate ADP that activates KATP. Substrate channeling of fructose 1,6-bisphosphate through the enzymes of lower glycolysis fuels pyruvate kinase, which directly consumes the ADP made by phosphofructokinase to raise ATP/ADP and close the channel. We further demonstrate the presence of a plasma membrane NAD+/NADH cycle, whereby lactate dehydrogenase is functionally coupled to glyceraldehyde-3-phosphate dehydrogenase. These studies provide direct electrophysiological evidence of a KATP-controlling glycolytic signaling complex and demonstrate its relevance to islet glucose sensing and excitability.Graphical abstractHoet al. demonstrate that the enzymes of glycolysis, as well as lactate dehydrogenase, form a plasma membrane-associated metabolon with intrinsic ATP/ADP and NAD+/NADH cycles. The subcellular location of this signaling complex allows both ATP-consuming and ATP-producing enzymes to locally control the activity of ATP-sensitive K+channels in pancreatic α and β cells from humans and mice.HighlightsKATPchannels are regulated by a glycolytic metabolon on the plasma membrane.Substrate channeling occurs between the consecutive enzymes of glycolysis.Upper glycolysis produces ADP that is used directly by lower glycolysis to make ATP.LDH and GADPH facilitate a plasma membrane-associated NAD+/NADH redox cycle.