Glucose Deprivation Regulates KATP Channel Trafficking via AMPK in Pancreatic Beta-Cells

Abstract

AMP-activated protein kinase (AMPK) and ATP-sensitive K+ channel (KATP channel) are metabolic sensors that are activated during metabolic stress. The importance of AMPK has been appreciated by its role as a regulator of metabolism, whereas KATP channel is known as a regulator of cellular excitability. Cross-talks between two systems are not well understood. In pancreatic β-cells or INS-1 cells, we measured KATP currents by the patch clamp technique and examined distributions of KATP channel proteins (Kir6.2 and SUR1) using immunofluorescence imaging and surface biotinylation studies. When KATP channels were activated by washout of intracellular ATP using a ATP- and Mg2+-free internal solution, the increase in whole cell conductance was surprisingly small in cells incubated in 11.1 mM glucose medium, but the increase was significantly higher in cells pre-incubated in glucose-free medium for 2 hrs. We confirmed that KATP channel proteins were mostly internalized in 11.1 mM glucose, but recruited to the plasma membrane by glucose deprivation without changes in total levels. The effects of glucose deprivation on KATP channels were abolished by an AMPK inhibitor or a knockdown of AMPK using siRNA, but mimicked by an AMPK activator. These results suggest that regulation of KATP channel trafficking by AMPK is a prerequisite for KATP channel activation in pancreatic β-cells in response to glucose deprivation. The interplay between AMPK and KATP channels may play a key role in inhibiting cellular excitability and insulin secretion under low energy status.