Glucose Deprivation Regulates KATP Channel Trafficking via AMP-Activated Protein Kinase in Pancreatic β-Cells
0301 basic medicine
0303 health sciences
Blotting, Western
Fluorescent Antibody Technique
AMP-Activated Protein Kinases
Rats
Electrophysiology
Immunoenzyme Techniques
03 medical and health sciences
Glucose
KATP Channels
Insulin-Secreting Cells
Insulin Secretion
Animals
Insulin
Original Article
Biotinylation
DOI:
10.2337/db09-0600
Publication Date:
2009-09-01T01:06:51Z
AUTHORS (8)
ABSTRACT
OBJECTIVE
AMP-activated protein kinase (AMPK) and the ATP-sensitive K+ (KATP) channel are metabolic sensors that become activated during metabolic stress. AMPK is an important regulator of metabolism, whereas the KATP channel is a regulator of cellular excitability. Cross talk between these systems is poorly understood.
RESEARCH DESIGN AND METHODS
Rat pancreatic β-cells or INS-1 cells were pretreated for 2 h at various concentrations of glucose. Maximum KATP conductance (Gmax) was monitored by whole-cell measurements after intracellular ATP washout using ATP-free internal solutions. KATP channel activity (NPo) was monitored by inside-out patch recordings in the presence of diazoxide. Distributions of KATP 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
Gmax 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 Gmax and the surface level of Kir6.2 were inhibited by compound C, an AMPK inhibitor, and siAMPK transfection. The effects of glucose deprivation on KATP channels were mimicked by an AMPK activator. Glucose deprivation reduced insulin secretion, but this response was attenuated by compound C.
CONCLUSIONS
KATP 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.
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