Glucose deprivation regulates KATP channel trafficking via AMP-activated protein kinase in pancreatic beta-cells.
OBJECTIVE
AMP-activated protein kinase (AMPK) and the ATP-sensitive K(+) (K(ATP)) channel are metabolic sensors that become activated during metabolic stress. AMPK is an important regulator of metabolism, whereas the K(ATP) channel is a regulator of cellular excitability. Cross talk between these systems is poorly understood.


METHODS
Rat pancreatic beta-cells or INS-1 cells were pretreated for 2 h at various concentrations of glucose. Maximum K(ATP) conductance (G(max)) was monitored by whole-cell measurements after intracellular ATP washout using ATP-free internal solutions. K(ATP) channel activity (NPo) was monitored by inside-out patch recordings in the presence of diazoxide. Distributions of K(ATP) channel proteins (Kir6.2 and SUR1) were examined using immunofluorescence imaging and surface biotinylation studies. Insulin secretion from rat pancreatic islets was measured using an enzyme immunoassay.


RESULTS
G(max) and NPo in cells pretreated with glucose-free or 3 mmol/l glucose solutions were significantly higher than in cells pretreated in 11.1 mmol/l glucose solutions. Immunofluorescence imaging and biotinylation studies revealed that glucose deprivation induced an increase in the surface level of Kir6.2 without affecting the total cellular amount. Increases in G(max) and the surface level of Kir6.2 were inhibited by compound C, an AMPK inhibitor, and siAMPK transfection. The effects of glucose deprivation on K(ATP) channels were mimicked by an AMPK activator. Glucose deprivation reduced insulin secretion, but this response was attenuated by compound C.


CONCLUSIONS
K(ATP) channel trafficking is regulated by energy status via AMPK, and this mechanism may play a key role in inhibiting insulin secretion under low energy status.
Lim
Ajin
A
National Research Laboratory for Cell Physiology, Seoul National University College of Medicine, Seoul, Korea.
Park
Sun-Hyun
SH
Sohn
Jong-Woo
JW
Jeon
Ju-Hong
JH
Park
Jae-Hyung
JH
Song
Dae-Kyu
DK
Lee
Suk-Ho
SH
Ho
Won-Kyung
WK
D055372:AMP-Activated Protein Kinases / Q000378:metabolism*; D000818:Animals; D019921:Biotinylation; D015153:Blotting, Western; D004594:Electrophysiology; D005455:Fluorescent Antibody Technique; D005947:Glucose / Q000172:deficiency* / Q000378:metabolism; D007124:Immunoenzyme Techniques; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000201:enzymology / Q000378:metabolism*; D054086:KATP Channels / Q000378:metabolism*; D051381:Rats
D007328:Insulin; D054086:KATP Channels; D055372:AMP-Activated Protein Kinases; D005947:Glucose