KATP channels, comprised of the pore-forming protein Kir6.x and the sulfonylurea receptor SURx, are regulated in an interdependent manner by adenine nucleotides, PIP2, and sulfonylureas. To gain insight into these interactions, we investigated the effects of mutating positively charged residues in Kir6.2, previously implicated in the response to PIP2, on channel regulation by adenine nucleotides and the sulfonylurea glyburide. Our data show that the Kir6.2 “PIP2-insensitive” mutants R176C and R177C are not reactivated by MgADP after ATP-induced inhibition and are also insensitive to glyburide. These results suggest that R176 and R177 are required for functional coupling to SUR1, which confers MgADP and sulfonylurea sensitivity to the KATP channel. In contrast, the R301C and R314C mutants, which are also “PIP2-insensitive,” remained sensitive to stimulation by MgADP in the absence of ATP and were inhibited by glyburide. Based on these findings, as well as previous data, we propose a model of the KATP channel whereby in the presence of ATP, the R176 and R177 residues on Kir6.2 form a specific site that interacts with NBF1 bound to ATP on SUR1, promoting channel opening by counteracting the inhibition by ATP. This interaction is facilitated by binding of MgADP to NBF2 and blocked by binding of sulfonylureas to SUR1. In the absence of ATP, since KATP channels are not blocked by ATP, they do not require the counteracting effect of NBF1 interacting with R176 and R177 to open. Nevertheless, channels in this state remain activated by MgADP. This effect may be explained by a direct stimulatory interaction of NBF2/MgADP moiety with another region of Kir6.2 (perhaps the NH2 terminus), or by NBF2/MgADP still promoting a weak interaction between NBF1 and Kir6.2 in the absence of ATP. The region delimited by R301 and R314 is not involved in the interaction with NBF1 or NBF2, but confers additional PIP2 sensitivity.
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1 October 2001
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October 03 2001
Regulation of Cloned Atp-Sensitive K Channels by Adenine Nucleotides and Sulfonylureas: Interactions between Sur1 and Positively Charged Domains on Kir6.2
Scott A. John,
Scott A. John
aUCLA Cardiovascular Research Laboratory, Division of Cardiology, University of California Los Angeles School of Medicine, Los Angeles, CA 90095
cDepartment of Medicine, Division of Cardiology, University of California Los Angeles School of Medicine, Los Angeles, CA 90095
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James N. Weiss,
James N. Weiss
aUCLA Cardiovascular Research Laboratory, Division of Cardiology, University of California Los Angeles School of Medicine, Los Angeles, CA 90095
bDepartment of Physiology, Division of Cardiology, University of California Los Angeles School of Medicine, Los Angeles, CA 90095
cDepartment of Medicine, Division of Cardiology, University of California Los Angeles School of Medicine, Los Angeles, CA 90095
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Bernard Ribalet
Bernard Ribalet
aUCLA Cardiovascular Research Laboratory, Division of Cardiology, University of California Los Angeles School of Medicine, Los Angeles, CA 90095
bDepartment of Physiology, Division of Cardiology, University of California Los Angeles School of Medicine, Los Angeles, CA 90095
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Scott A. John
aUCLA Cardiovascular Research Laboratory, Division of Cardiology, University of California Los Angeles School of Medicine, Los Angeles, CA 90095
cDepartment of Medicine, Division of Cardiology, University of California Los Angeles School of Medicine, Los Angeles, CA 90095
James N. Weiss
aUCLA Cardiovascular Research Laboratory, Division of Cardiology, University of California Los Angeles School of Medicine, Los Angeles, CA 90095
bDepartment of Physiology, Division of Cardiology, University of California Los Angeles School of Medicine, Los Angeles, CA 90095
cDepartment of Medicine, Division of Cardiology, University of California Los Angeles School of Medicine, Los Angeles, CA 90095
Bernard Ribalet
aUCLA Cardiovascular Research Laboratory, Division of Cardiology, University of California Los Angeles School of Medicine, Los Angeles, CA 90095
bDepartment of Physiology, Division of Cardiology, University of California Los Angeles School of Medicine, Los Angeles, CA 90095
Abbreviations used in this paper: KATP, ATP-sensitive K; PIP2, phosphatidylinositol bisphosphate.
Received:
April 21 2001
Revision Requested:
August 24 2001
Accepted:
August 27 2001
Online ISSN: 1540-7748
Print ISSN: 0022-1295
© 2001 The Rockefeller University Press
2001
The Rockefeller University Press
J Gen Physiol (2001) 118 (4): 391–406.
Article history
Received:
April 21 2001
Revision Requested:
August 24 2001
Accepted:
August 27 2001
Citation
Scott A. John, James N. Weiss, Bernard Ribalet; Regulation of Cloned Atp-Sensitive K Channels by Adenine Nucleotides and Sulfonylureas: Interactions between Sur1 and Positively Charged Domains on Kir6.2. J Gen Physiol 1 October 2001; 118 (4): 391–406. doi: https://doi.org/10.1085/jgp.118.4.391
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