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

Abstract

The ATP-sensitive K+ channel (KATP) is a key regulator of hormone secretion from pancreatic islet endocrine cells. Using direct measurements of KATP channel activity in pancreatic {beta} cells and the lesser-studied cells, from both humans and mice, we demonstrate that a glycolytic metabolon locally controls KATP channels 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 abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=191 SRC="FIGDIR/small/511200v4_ufig1.gif" ALT="Figure 1"> View larger version (53K): org.highwire.dtl.DTLVardef@105da9aorg.highwire.dtl.DTLVardef@152d1b5org.highwire.dtl.DTLVardef@45da58org.highwire.dtl.DTLVardef@1fbdc_HPS_FORMAT_FIGEXP M_FIG Ho et 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 and cells from humans and mice. C_FIG HighlightsO_LIKATP channels are regulated by a glycolytic metabolon on the plasma membrane. C_LIO_LISubstrate channeling occurs between the consecutive enzymes of glycolysis. C_LIO_LIUpper glycolysis produces ADP that is used directly by lower glycolysis to make ATP. C_LIO_LILDH and GADPH facilitate a plasma membrane-associated NAD+/NADH redox cycle. C_LI