title: Mutations of the same conserved glutamate residue in NBD2 of the sulfonylurea receptor 1 subunit of the KATP channel can result in either hyperinsulinism or neonatal diabetes.
abstract: OBJECTIVE
  Two novel mutations (E1506D, E1506G) in the nucleotide-binding domain 2 (NBD2) of the ATP-sensitive K(+) channel (K(ATP) channel) sulfonylurea receptor 1 (SUR1) subunit were detected heterozygously in patients with neonatal diabetes. A mutation at the same residue (E1506K) was previously shown to cause congenital hyperinsulinemia. We sought to understand why mutations at the same residue can cause either neonatal diabetes or hyperinsulinemia.
  
  
  METHODS
  Neonatal diabetic patients were sequenced for mutations in ABCC8 (SUR1) and KCNJ11 (Kir6.2). Wild-type and mutant K(ATP) channels were expressed in Xenopus laevis oocytes and studied with electrophysiological methods.
  
  
  RESULTS
  Oocytes expressing neonatal diabetes mutant channels had larger resting whole-cell K(ATP) currents than wild-type, consistent with the patients' diabetes. Conversely, no E1506K currents were recorded at rest or after metabolic inhibition, as expected for a mutation causing hyperinsulinemia. K(ATP) channels are activated by Mg-nucleotides (via SUR1) and blocked by ATP (via Kir6.2). All mutations decreased channel activation by MgADP but had little effect on MgATP activation, as assessed using an ATP-insensitive Kir6.2 subunit. Importantly, using wild-type Kir6.2, a 30-s preconditioning exposure to physiological MgATP concentrations (>300 µmol/L) caused a marked reduction in the ATP sensitivity of neonatal diabetic channels, a small decrease in that of wild-type channels, and no change for E1506K channels. This difference in MgATP inhibition may explain the difference in resting whole-cell currents found for the neonatal diabetes and hyperinsulinemia mutations.
  
  
  CONCLUSIONS
  Mutations in the same residue can cause either hyperinsulinemia or neonatal diabetes. Differentially altered nucleotide regulation by NBD2 of SUR1 can explain the respective clinical phenotypes.
authors: Henry Wellcome Centre for Gene Function, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, U.K.
authors: Roope
authors: R
authors: Männikkö
authors: Sarah E
authors: SE
authors: Flanagan
authors: Xiuli
authors: X
authors: Sim
authors: David
authors: D
authors: Segal
authors: Khalid
authors: K
authors: Hussain
authors: Sian
authors: S
authors: Ellard
authors: Andrew T
authors: AT
authors: Hattersley
authors: Frances M
authors: FM
authors: Ashcroft
references: Neuron. 1997 May;18(5):827-38
references: 9182806
references: J Clin Invest. 2009 Jan;119(1):80-90
references: 19065048
references: Diabetes. 2005 Sep;54(9):2503-13
references: 16123337
references: Science. 1995 Apr 21;268(5209):423-6
references: 7716547
references: Lancet. 2003 Jan 25;361(9354):301-7
references: 12559865
references: Cell. 2000 Mar 17;100(6):645-54
references: 10761930
references: J Mol Cell Cardiol. 2005 Jun;38(6):917-25
references: 15910876
references: EMBO J. 1997 Mar 17;16(6):1145-52
references: 9135131
references: N Engl J Med. 2004 Apr 29;350(18):1838-49
references: 15115830
references: Diabetes. 2007 Jul;56(7):1930-7
references: 17446535
references: FEBS J. 2008 Jul;275(13):3312-24
references: 18489584
references: Philos Trans R Soc Lond B Biol Sci. 2009 Jan 27;364(1514):257-67
references: 18990670
references: Nat Clin Pract Endocrinol Metab. 2007 Jan;3(1):57-68
references: 17179930
references: J Biol Chem. 2004 Nov 5;279(45):46518-26
references: 15326176
references: Pflugers Arch. 1987 Feb;408(2):133-8
references: 2436138
references: Nature. 2006 Mar 23;440(7083):470-6
references: 16554807
references: EMBO Rep. 2008 Jul;9(7):648-54
references: 18497752
references: J Gen Physiol. 2010 Oct;136(4):389-405
references: 20876358
references: J Biol Chem. 2003 Oct 3;278(40):38537-47
references: 12882957
references: Proc Natl Acad Sci U S A. 1998 Nov 10;95(23):13953-8
references: 9811907
references: J Biol Chem. 2000 Sep 29;275(39):30046-9
references: 10866996
references: Diabetologia. 2003 Jul;46(7):875-91
references: 12819907
references: J Clin Endocrinol Metab. 2008 Mar;93(3):1054-61
references: 18073297
references: Science. 1996 Jun 21;272(5269):1785-7
references: 8650576
references: J Clin Invest. 2000 Oct;106(7):897-906
references: 11018078
references: J Biol Chem. 2000 Sep 15;275(37):28757-63
references: 10893240
references: Cell Metab. 2010 Mar 3;11(3):179-81
references: 20197050
references: Am J Physiol Endocrinol Metab. 2007 Oct;293(4):E880-9
references: 17652156
references: EMBO J. 2005 Dec 7;24(23):4166-75
references: 16308567
references: Proc Natl Acad Sci U S A. 1998 Jun 9;95(12):7185-90
references: 9618560
references: Hum Mol Genet. 2007 Aug 15;16(16):2011-9
references: 17584766
references: J Physiol. 1997 Jan 1;498 ( Pt 1):87-98
references: 9023770
references: N Engl J Med. 2006 Aug 3;355(5):467-77
references: 16885550
references: J Physiol. 2010 Sep 1;588(Pt 17):3201-9
references: 20519313
references: N Engl J Med. 2006 Aug 3;355(5):456-66
references: 16885549
references: Nature. 1984 Nov 29-Dec 5;312(5993):446-8
references: 6095103
references: J Gen Physiol. 1997 Dec;110(6):643-54
references: 9382893
references: Neuron. 2001 Aug 2;31(2):233-45
references: 11502255
references: J Clin Invest. 2008 Aug;118(8):2877-86
references: 18596924
references: EMBO Rep. 2003 Nov;4(11):1038-42
references: 14593442
references: Nature. 1997 May 8;387(6629):179-83
references: 9144288