ATP Sensitivity of the ATP-Sensitive K+ Channel in Intact and Permeabilized Pancreatic β-Cells
- Address correspondence and reprint requests to Prof. F.M. Ashcroft, University Laboratory of Physiology, Parks Road, Oxford, OX1 3PT, U.K. E-mail: frances.ashcroft{at}physiol.ox.ac.uk
Abstract
ATP-sensitive K+ channels (KATP channels) couple cell metabolism to electrical activity and thereby to physiological processes such as hormone secretion, muscle contraction, and neuronal activity. However, the mechanism by which metabolism regulates KATP channel activity, and the channel sensitivity to inhibition by ATP in its native environment, remain controversial. Here, we used α-toxin to permeabilize single pancreatic β-cells and measure KATP channel ATP sensitivity. We show that the channel ATP sensitivity is approximately sevenfold lower in the permeabilized cell than in the inside-out patch and that this is caused by interaction of Mg-nucleotides with the nucleotide-binding domains of the SUR1 subunit of the channel. The ATP sensitivity observed in permeabilized cells accounts quantitatively for KATP channel activity in intact cells. Thus, our results show that the principal metabolic regulators of KATP channel activity are MgATP and MgADP.
- [ATP]i, intracellular concentration of ATP
- [ATP]sm, submembrane ATP concentration
- KATP channel, ATP-sensitive K+ channel
- LC-CoA, long-chain acyl-CoA
- NBD, nucleotide-binding domain
- PIP2, phosphatidylinositol 4,5-bisphosphate
- SUR, sulfonylurea receptor
Footnotes
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Additional information for this article can be found in an online appendix at http://diabetes.diabetesjournals.org.
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- Accepted June 5, 2006.
- Received March 19, 2006.
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