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Role of the C‐terminus of SUR in the differential regulation of β‐cell and cardiac K(ATP) channels by MgADP and metabolism
KEY POINTS: β‐Cell K(ATP) channels are partially open in the absence of metabolic substrates, whereas cardiac K(ATP) channels are closed. Using cloned channels heterologously expressed in Xenopus oocytes we measured the effect of MgADP on the MgATP concentration–inhibition curve immediately after pa...
Autores principales: | , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
John Wiley and Sons Inc.
2018
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6292810/ https://www.ncbi.nlm.nih.gov/pubmed/30179258 http://dx.doi.org/10.1113/JP276708 |
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author | Vedovato, Natascia Rorsman, Olof Hennis, Konstantin Ashcroft, Frances M. Proks, Peter |
author_facet | Vedovato, Natascia Rorsman, Olof Hennis, Konstantin Ashcroft, Frances M. Proks, Peter |
author_sort | Vedovato, Natascia |
collection | PubMed |
description | KEY POINTS: β‐Cell K(ATP) channels are partially open in the absence of metabolic substrates, whereas cardiac K(ATP) channels are closed. Using cloned channels heterologously expressed in Xenopus oocytes we measured the effect of MgADP on the MgATP concentration–inhibition curve immediately after patch excision. MgADP caused a far more striking reduction in ATP inhibition of Kir6.2/SUR1 channels than Kir6.2/SUR2A channels; this effect declined rapidly after patch excision. Exchanging the final 42 amino acids of SUR was sufficient to switch the Mg‐nucleotide regulation of Kir6.2/SUR1 and Kir6.2/SUR2A channels, and partially switch their sensitivity to metabolic inhibition. Deletion of the C‐terminal 42 residues of SUR abolished MgADP activation of both Kir6.2/SUR1 and Kir6.2/SUR2A channels. We conclude that the different metabolic sensitivity of Kir6.2/SUR1 and Kir6.2/SUR2A channels is at least partially due to their different regulation by Mg‐nucleotides, which is determined by the final 42 amino acids. ABSTRACT: ATP‐sensitive potassium (K(ATP)) channels couple the metabolic state of a cell to its electrical activity and play important physiological roles in many tissues. In contrast to β‐cell (Kir6.2/SUR1) channels, which open when extracellular glucose levels fall, cardiac (Kir6.2/SUR2A) channels remain closed. This is due to differences in the SUR subunit rather than cell metabolism. As ATP inhibition and MgADP activation are similar for both types of channels, we investigated channel inhibition by MgATP in the presence of 100 μm MgADP immediately after patch excision [when the channel open probability (P (O)) is near maximal]. The results were strikingly different: 100 μm MgADP substantially reduced MgATP inhibition of Kir6.2/SUR1, but had no effect on MgATP inhibition of Kir6.2/SUR2A. Exchanging the final 42 residues of SUR2A with that of SUR1 switched the channel phenotype (and vice versa), and deleting this region abolished Mg‐nucleotide activation. This suggests the C‐terminal 42 residues are important for the ability of MgADP to influence ATP inhibition at Kir6.2. This region was also necessary, but not sufficient, for activation of the K(ATP) channel in intact cells by metabolic inhibition (azide). We conclude that the ability of MgADP to impair ATP inhibition at Kir6.2 accounts, in part, for the differential metabolic sensitivities of β‐cell and cardiac K(ATP) channels. |
format | Online Article Text |
id | pubmed-6292810 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2018 |
publisher | John Wiley and Sons Inc. |
record_format | MEDLINE/PubMed |
spelling | pubmed-62928102018-12-18 Role of the C‐terminus of SUR in the differential regulation of β‐cell and cardiac K(ATP) channels by MgADP and metabolism Vedovato, Natascia Rorsman, Olof Hennis, Konstantin Ashcroft, Frances M. Proks, Peter J Physiol Molecular and cellular KEY POINTS: β‐Cell K(ATP) channels are partially open in the absence of metabolic substrates, whereas cardiac K(ATP) channels are closed. Using cloned channels heterologously expressed in Xenopus oocytes we measured the effect of MgADP on the MgATP concentration–inhibition curve immediately after patch excision. MgADP caused a far more striking reduction in ATP inhibition of Kir6.2/SUR1 channels than Kir6.2/SUR2A channels; this effect declined rapidly after patch excision. Exchanging the final 42 amino acids of SUR was sufficient to switch the Mg‐nucleotide regulation of Kir6.2/SUR1 and Kir6.2/SUR2A channels, and partially switch their sensitivity to metabolic inhibition. Deletion of the C‐terminal 42 residues of SUR abolished MgADP activation of both Kir6.2/SUR1 and Kir6.2/SUR2A channels. We conclude that the different metabolic sensitivity of Kir6.2/SUR1 and Kir6.2/SUR2A channels is at least partially due to their different regulation by Mg‐nucleotides, which is determined by the final 42 amino acids. ABSTRACT: ATP‐sensitive potassium (K(ATP)) channels couple the metabolic state of a cell to its electrical activity and play important physiological roles in many tissues. In contrast to β‐cell (Kir6.2/SUR1) channels, which open when extracellular glucose levels fall, cardiac (Kir6.2/SUR2A) channels remain closed. This is due to differences in the SUR subunit rather than cell metabolism. As ATP inhibition and MgADP activation are similar for both types of channels, we investigated channel inhibition by MgATP in the presence of 100 μm MgADP immediately after patch excision [when the channel open probability (P (O)) is near maximal]. The results were strikingly different: 100 μm MgADP substantially reduced MgATP inhibition of Kir6.2/SUR1, but had no effect on MgATP inhibition of Kir6.2/SUR2A. Exchanging the final 42 residues of SUR2A with that of SUR1 switched the channel phenotype (and vice versa), and deleting this region abolished Mg‐nucleotide activation. This suggests the C‐terminal 42 residues are important for the ability of MgADP to influence ATP inhibition at Kir6.2. This region was also necessary, but not sufficient, for activation of the K(ATP) channel in intact cells by metabolic inhibition (azide). We conclude that the ability of MgADP to impair ATP inhibition at Kir6.2 accounts, in part, for the differential metabolic sensitivities of β‐cell and cardiac K(ATP) channels. John Wiley and Sons Inc. 2018-10-14 2018-12-15 /pmc/articles/PMC6292810/ /pubmed/30179258 http://dx.doi.org/10.1113/JP276708 Text en © 2018 The Authors. The Journal of Physiology published by John Wiley & Sons Ltd on behalf of The Physiological Society This is an open access article under the terms of the http://creativecommons.org/licenses/by/4.0/ License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. |
spellingShingle | Molecular and cellular Vedovato, Natascia Rorsman, Olof Hennis, Konstantin Ashcroft, Frances M. Proks, Peter Role of the C‐terminus of SUR in the differential regulation of β‐cell and cardiac K(ATP) channels by MgADP and metabolism |
title | Role of the C‐terminus of SUR in the differential regulation of β‐cell and cardiac K(ATP) channels by MgADP and metabolism |
title_full | Role of the C‐terminus of SUR in the differential regulation of β‐cell and cardiac K(ATP) channels by MgADP and metabolism |
title_fullStr | Role of the C‐terminus of SUR in the differential regulation of β‐cell and cardiac K(ATP) channels by MgADP and metabolism |
title_full_unstemmed | Role of the C‐terminus of SUR in the differential regulation of β‐cell and cardiac K(ATP) channels by MgADP and metabolism |
title_short | Role of the C‐terminus of SUR in the differential regulation of β‐cell and cardiac K(ATP) channels by MgADP and metabolism |
title_sort | role of the c‐terminus of sur in the differential regulation of β‐cell and cardiac k(atp) channels by mgadp and metabolism |
topic | Molecular and cellular |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6292810/ https://www.ncbi.nlm.nih.gov/pubmed/30179258 http://dx.doi.org/10.1113/JP276708 |
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