Kir6.2 mutations associated with neonatal diabetes reduce expression of ATP-sensitive K+ channels: Implications in disease mechanism and sulfonylurea therapy

Chia Wei Lin, Yu Wen Lin, Fei Fei Yan, Jillene Casey, Malini Kochhar, Emily B. Pratt, Show Ling Shyng

Research output: Contribution to journalArticle

28 Scopus citations

Abstract

Heterozygous missense mutations in the pore-forming subunit Kir6.2 of ATP-sensitive K+ channels (KATP channels) have recently been shown to cause permanent neonatal diabetes mellitus (PNDM). Functional studies demonstrated that PNDM mutations reduce KATP channel sensitivity to ATP inhibition, resulting in gain of channel function. However, the impact of these mutations on channel expression has not been examined. Here, we show that PNDM mutations, including Q52R, V59G, V59M, R201C, R201H, and I296L, not only reduce channel ATP sensitivity but also impair channel expression at the cell surface to varying degrees. By tagging the PNDM Kir6.2 mutant V59G or R201H with an additional mutation, N160D, that confers voltage-dependent polyamine block of KATP channels, we demonstrate that in simulated heterozygous state, all surface channels are either wild-type or heteromeric channels containing both wild-type and mutant Kir6.2 subunits. Comparison of the various PNDM mutations in their effects on channel nucleotide sensitivity and expression, as well as disease phenotype, suggests that both channel-gating defect and expression level may play a role in determining disease severity. Interestingly, sulfonylureas significantly increase surface expression of certain PNDM mutants, suggesting that the efficacy of sulfonylurea therapy may be compromised by the effect of these drugs on channel expression.

Original languageEnglish (US)
Pages (from-to)1738-1746
Number of pages9
JournalDiabetes
Volume55
Issue number6
DOIs
StatePublished - Sep 11 2006

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Keywords

  • CHOP, CIEBP homolog protein
  • DEND, developmental delay, epilepsy, and neonatal diabetes
  • K channel, ATP-sensitive K channel
  • PNDM, permanent neonatal diabetes mellitus
  • SUR1, sulfonylurea receptor one

ASJC Scopus subject areas

  • Internal Medicine
  • Endocrinology, Diabetes and Metabolism

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