Sulfonylurea receptor 1 mutations that cause opposite insulin secretion defects with chemical chaperone exposure

Emily B. Pratt, Fei Fei Yan, Joel W. Gay, Charles A. Stanley, Show Ling Shyng

Research output: Contribution to journalArticle

24 Scopus citations

Abstract

The α-cell ATP-sensitive potassium (KATP) channel composed of sulfonylurea receptor SUR1 and potassium channel Kir6.2 serves a key role in insulin secretion regulation by linking glucose metabolism to cell excitability. Mutations in SUR1 or Kir6.2 that decrease channel function are typically associated with congenital hyperinsulinism, whereas those that increase channel function are associated with neonatal diabetes. Here we report that two hyperinsulinism-associated SUR1 missense mutations, R74W and E128K, surprisingly reduce channel inhibition by intracellular ATP, a gating defect expected to yield the opposite disease phenotype neonatal diabetes. Under normal conditions, both mutant channels showed poor surface expression due to retention in the endoplasmic reticulum, accounting for the loss of channel function phenotype in the congenital hyperinsulinism patients. This trafficking defect, however, could be corrected by treating cells with the oral hypoglycemic drugs sulfonylureas, which we have shown previously to act as small molecule chemical chaperones for KATP channels. The R74W and E128K mutants thus rescued to the cell surface paradoxically exhibited ATP sensitivity 6-and 12-fold lower than wild-type channels, respectively. Further analyses revealed a nucleotide-independent decrease in mutant channel intrinsic open probability, suggesting the mutations may reduce ATP sensitivity by causing functional uncoupling between SUR1 and Kir6.2. In insulin-secreting cells, rescue of both mutant channels to the cell surface led to hyperpolarized membrane potentials and reduced insulin secretion upon glucose stimulation. Our results show that sulfonylureas, as chemical chaperones, can dictate manifestation of the two opposite insulin secretion defects by altering the expression levels of the disease mutants.

Original languageEnglish (US)
Pages (from-to)7951-7959
Number of pages9
JournalJournal of Biological Chemistry
Volume284
Issue number12
DOIs
StatePublished - Mar 20 2009

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ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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