Neonatal diabetes caused by mutations in sulfonylurea receptor 1: Interplay between expression and Mg-nucleotide gating defects of ATP-sensitive potassium channels

Qing Zhou, Intza Garin, Luis Castaño, Jesús Argente, Ma Teresa Muñoz-Calvo, Guiomar Perez De Nanclares, Show-Ling Shyng

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

Context: ATP-sensitive potassium (KATP) channels regulate insulin secretion by coupling glucose metabolism to β-cell membrane potential. Gain-of-function mutations in the sulfonylurea receptor 1 (SUR1) or Kir6.2 channel subunit underlie neonatal diabetes. Objective: The objective of the study was to determine the mechanisms by which two SUR1 mutations, E208K and V324M, associated with transient neonatal diabetes affect KATP channel function. Design: E208K or V324M mutant SUR1 was coexpressed with Kir6.2 in COS cells, and expression and gating properties of the resulting channels were assessed biochemically and electrophysiologically. Results: Both E208K and V324M augment channel response to MgADP stimulation without altering sensitivity to ATP4- or sulfonylureas. Surprisingly, whereas E208K causes only a small increase in MgADP response consistent with the mild transient diabetes phenotype, V324M causes a severe activating gating defect. Unlike E208K, V324M also impairs channel expression at the cell surface, which is expected to dampen its functional impact on β-cells. When either mutation was combined with a mutation in the second nucleotide binding domain of SUR1 previously shown to abolish Mg-nucleotide response, the activating effect of E208K and V324M was also abolished. Moreover, combination of E208K and V324M results in channels with Mg-nucleotide sensitivity greater than that seen in individual mutations alone. Conclusion: The results demonstrate that E208K and V324M, located in distinct domains of SUR1, enhance transduction of Mg-nucleotide stimulation from the SUR1 nucleotide binding folds to Kir6.2. Furthermore, they suggest that diabetes severity is determined by interplay between effects of a mutation on channel expression and channel gating.

Original languageEnglish (US)
JournalJournal of Clinical Endocrinology and Metabolism
Volume95
Issue number12
DOIs
StatePublished - Dec 2010

Fingerprint

Sulfonylurea Receptors
KATP Channels
Medical problems
Nucleotides
Defects
Mutation
Adenosine Diphosphate
COS Cells
Cell membranes
Metabolism
Membrane Potentials
Potassium
Adenosine Triphosphate
Cell Membrane
Insulin
Phenotype
Glucose

ASJC Scopus subject areas

  • Biochemistry
  • Clinical Biochemistry
  • Endocrinology
  • Biochemistry, medical
  • Endocrinology, Diabetes and Metabolism

Cite this

Neonatal diabetes caused by mutations in sulfonylurea receptor 1 : Interplay between expression and Mg-nucleotide gating defects of ATP-sensitive potassium channels. / Zhou, Qing; Garin, Intza; Castaño, Luis; Argente, Jesús; Muñoz-Calvo, Ma Teresa; De Nanclares, Guiomar Perez; Shyng, Show-Ling.

In: Journal of Clinical Endocrinology and Metabolism, Vol. 95, No. 12, 12.2010.

Research output: Contribution to journalArticle

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AB - Context: ATP-sensitive potassium (KATP) channels regulate insulin secretion by coupling glucose metabolism to β-cell membrane potential. Gain-of-function mutations in the sulfonylurea receptor 1 (SUR1) or Kir6.2 channel subunit underlie neonatal diabetes. Objective: The objective of the study was to determine the mechanisms by which two SUR1 mutations, E208K and V324M, associated with transient neonatal diabetes affect KATP channel function. Design: E208K or V324M mutant SUR1 was coexpressed with Kir6.2 in COS cells, and expression and gating properties of the resulting channels were assessed biochemically and electrophysiologically. Results: Both E208K and V324M augment channel response to MgADP stimulation without altering sensitivity to ATP4- or sulfonylureas. Surprisingly, whereas E208K causes only a small increase in MgADP response consistent with the mild transient diabetes phenotype, V324M causes a severe activating gating defect. Unlike E208K, V324M also impairs channel expression at the cell surface, which is expected to dampen its functional impact on β-cells. When either mutation was combined with a mutation in the second nucleotide binding domain of SUR1 previously shown to abolish Mg-nucleotide response, the activating effect of E208K and V324M was also abolished. Moreover, combination of E208K and V324M results in channels with Mg-nucleotide sensitivity greater than that seen in individual mutations alone. Conclusion: The results demonstrate that E208K and V324M, located in distinct domains of SUR1, enhance transduction of Mg-nucleotide stimulation from the SUR1 nucleotide binding folds to Kir6.2. Furthermore, they suggest that diabetes severity is determined by interplay between effects of a mutation on channel expression and channel gating.

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