ABCMdb

PMID: 16613899

Proks P, Arnold AL, Bruining J, Girard C, Flanagan SE, Larkin B, Colclough K, Hattersley AT, Ashcroft FM, Ellard S
A heterozygous activating mutation in the sulphonylurea receptor SUR1 (ABCC8) causes neonatal diabetes.
Hum Mol Genet. 2006 Jun 1;15(11):1793-800. Epub 2006 Apr 13., [PubMed]

Sentences

No. Mutations Sentence Comment

4 ABCC8 p.Phe132Leu We identified a novel heterozygous mutation, F132L, in the ABCC8 gene of a patient with severe developmental delay, epilepsy and neonatal diabetes (DEND syndrome). Login to comment 7 ABCC8 p.Phe132Leu Functional studies of recombinant KATP channels demonstrated that F132L markedly reduces the sensitivity of the KATP channel to inhibition by MgATP and this increases the whole-cell KATP current. Login to comment 55 ABCC8 p.Phe132Leu One patient (ISPAD68) was heterozygous for a novel mutation (F132L) in the ABCC8 gene encoding SUR1. Login to comment 58 ABCC8 p.Phe132Leu ABCC8 p.Phe132Leu ABCC8 p.Phe132Leu The novel F132L mutation results in the substitution of leucine for phenylalanine at residue 132 (p.Phe132Leu) in exon 3 of the ABCC8 gene (c.394T.C; Fig. 1A). Login to comment 60 ABCC8 p.Phe132Leu The F132L mutation was not found in 150 normal chromosomes. Login to comment 66 ABCC8 p.Phe132Leu The region on either side of F132L is also highly conserved (Fig. 1B). Login to comment 68 ABCC8 p.Phe132Leu Clinical characteristics of patient with F132L SUR1 mutation ISPAD68 was a boy born in 1978 with a birth weight of 2200 g to a 29-year-old mother who had previously given birth to two healthy older children. Login to comment 74 ABCC8 p.Phe132Leu ABCC8 p.Phe132Leu F132L mutation, conservation of F132 across species and location of F132L in SUR1. Login to comment 75 ABCC8 p.Phe132Leu (A) Sequencing of ISPAD68 showing a heterozygous mutation (c.394T.C) resulting in the substitution of phenylalanine (TTC) by leucine (CTC) at residue 132 (F132L) of the ABCC8 gene (arrow). Login to comment 81 ABCC8 p.Phe132Leu (C) Schematic of the proposed membrane topologies of SUR1 and Kir6.2 showing the location of F132L (arrowed) in SUR1. Login to comment 104 ABCC8 p.Phe132Leu SUR1 mutant KATP channels are not closed by resting ATP levels To analyse the functional effects of the SUR1-F132L mutation, we studied recombinant KATP channels expressed in Xenopus oocytes. Login to comment 107 ABCC8 p.Phe132Leu ABCC8 p.Phe132Leu In contrast, significant whole-cell Kþ currents were present in the absence of metabolic inhibition (resting currents) in oocytes expressing either homomeric or heterozygous SUR1-F132L mutant channels (Fig. 2). Login to comment 112 ABCC8 p.Phe132Leu SUR1-F132L KATP channels have reduced ATP sensitivity To explore the molecular basis of the reduced metabolic sensitivity of mutant KATP channels, we tested the ability of ATP to block wild-type and mutant channels in inside-out patches. Login to comment 115 ABCC8 p.Phe132Leu ABCC8 p.Phe132Leu (A) Whole-cell currents recorded from Xenopus oocytes coexpressing Kir6.2 and either SUR1 (WT) or SUR1-F132L (homF132L) or both SUR1 and SUR1-F132L (hetF132L) in response to voltage steps of +20 mV from a holding potential of 210 mV. Login to comment 126 ABCC8 p.Phe132Leu These results indicate that the F132L mutation in SUR1 markedly reduces the ability of ATP to inhibit the KATP channel. Login to comment 127 ABCC8 p.Phe132Leu DISCUSSION We report a novel heterozygous mutation, F132L, in the ABCC8 gene encoding SUR1 in a patient with DEND syndrome. Login to comment 130 ABCC8 p.Phe132Leu Genetic evidence for the pathogenicity of the F132L mutation is strong; it is a spontaneous mutation, absent from 150 normal chromosomes and affects a residue that shows evolutionary conservation across species. Login to comment 131 ABCC8 p.Phe132Leu Functional studies also support the pathogenicity of the F132L mutation by revealing that the mutation dramatically reduces the inhibitory potency of MgATP. Login to comment 139 ABCC8 p.Phe132Leu Our results suggest that this physical interaction may be mediated, in part, via the second cytosolic loop of SUR1 and that the F132L mutation influences the interaction of SUR1 with Kir6.2. Login to comment 140 ABCC8 p.Val187Asp ABCC8 p.Ala116Pro Two mutations in TMD0 (A116P and V187D), which cause congenital hyperinsulinism, abrogate the association of SUR1 and Kir6.2 and lead to loss of KATP channel function (27,35). Login to comment 143 ABCC8 p.Phe132Leu ABCC8 p.Phe132Leu (A) KATP currents recorded in inside-out patches excised from oocytes coexpressing Kir6.2 and either SUR1 or SUR1-F132L (Kir6.2/SUR1-homF132L) or both SUR1 and SUR1-F132L (Kir6.2/SUR1-hetF132L). Login to comment 147 ABCC8 p.Phe132Leu ABCC8 p.Phe132Leu (B) Mean relationship between [ATP] and KATP conductance (G), expressed relative to the conductance in the absence of nucleotide (Gc) for Kir6.2/SUR1 (open circles, n ¼ 6), and heterozygous (solid circles, n ¼ 6) or homomeric (solid squares, n ¼ 7) Kir6.2/SUR1-F132L channels. Login to comment 154 ABCC8 p.Phe132Leu The F132L mutation causes a dramatic decrease in the ability of ATP to inhibit the activity of the KATP channel in both the homozygous and simulated heterozygous states. Login to comment 170 ABCC8 p.Phe132Leu Predicted response to sulphonylurea treatment In the presence of the sulphonylurea tolbutamide (0.5 mmol/l), heterozygous F132L SUR1 channels were blocked by 72%. Login to comment 178 ABCC8 p.Phe132Leu Given the location of residue F132 in TMD0, a region known to regulate KATP channel gating (26,27), it seems reasonable to speculate that the F132L mutation acts by stabilizing the channel open state, thus indirectly reducing its ATP sensitivity. Login to comment 186 ABCC8 p.Phe132Leu Functional analysis demonstrates that the F132L SUR1 mutation acts in a similar way to Kir6.2 mutations causing DEND syndrome by producing a marked reduction in the ability of ATP to block the KATP channel. Login to comment