ABCMdb

ABCC8 p.Phe686Ser

Predicted by SNAP2:	A: D (85%), C: D (80%), D: D (95%), E: D (91%), G: D (91%), H: D (91%), I: D (85%), K: D (91%), L: D (85%), M: D (85%), N: D (91%), P: D (91%), Q: D (85%), R: D (95%), S: D (91%), T: D (85%), V: D (85%), W: D (91%), Y: D (91%),
Predicted by PROVEAN:	A: D, C: D, D: D, E: D, G: D, H: D, I: D, K: D, L: D, M: D, N: D, P: D, Q: D, R: D, S: D, T: D, V: D, W: D, Y: N,

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[hide] Congenital hyperinsulinism associated ABCC8 mutati... Diabetes. 2007 Sep;56(9):2339-48. Epub 2007 Jun 15. Yan FF, Lin YW, MacMullen C, Ganguly A, Stanley CA, Shyng SL
Congenital hyperinsulinism associated ABCC8 mutations that cause defective trafficking of ATP-sensitive K+ channels: identification and rescue.
Diabetes. 2007 Sep;56(9):2339-48. Epub 2007 Jun 15., [PMID:17575084]

Abstract [show]
Congenital hyperinsulinism (CHI) is a disease characterized by persistent insulin secretion despite severe hypoglycemia. Mutations in the pancreatic ATP-sensitive K(+) (K(ATP)) channel proteins sulfonylurea receptor 1 (SUR1) and Kir6.2, encoded by ABCC8 and KCNJ11, respectively, is the most common cause of the disease. Many mutations in SUR1 render the channel unable to traffic to the cell surface, thereby reducing channel function. Previous studies have shown that for some SUR1 trafficking mutants, the defects could be corrected by treating cells with sulfonylureas or diazoxide. The purpose of this study is to identify additional mutations that cause channel biogenesis/trafficking defects and those that are amenable to rescue by pharmacological chaperones. Fifteen previously uncharacterized CHI-associated missense SUR1 mutations were examined for their biogenesis/trafficking defects and responses to pharmacological chaperones, using a combination of immunological and functional assays. Twelve of the 15 mutations analyzed cause reduction in cell surface expression of K(ATP) channels by >50%. Sulfonylureas rescued a subset of the trafficking mutants. By contrast, diazoxide failed to rescue any of the mutants. Strikingly, the mutations rescued by sulfonylureas are all located in the first transmembrane domain of SUR1, designated as TMD0. All TMD0 mutants rescued to the cell surface by the sulfonylurea tolbutamide could be subsequently activated by metabolic inhibition on tolbutamide removal. Our study identifies a group of CHI-causing SUR1 mutations for which the resulting K(ATP) channel trafficking and expression defects may be corrected pharmacologically to restore channel function.

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47 TABLE 1 Genetic and clinical information on patients carrying the CHI mutations Mutation Disease Haplotype Diazoxide response References G7R Focal G7R No 44 N24K Diffuse N24K/R1215W No Not reported F27S Focal F27S No 39 R74W Focal R74W/R1215Q No 39,45,46 E128K Diffuse E128K No Not reported R495Q Diffuse R495Q/R1215Q No 39 E501K Focal E501K No 39 L503P Focal L503P No 44 F686S Focal F686S No 39 G716V* Diffuse G716V/G716V No 47,48 K1337N Not done g3992-9a/K1337N Yes 39 L1350Q Focal L1350Q No 44 S1387F Diffuse S1387F/NA No 9,24 L1390P NA L1390P/NA No Not reported D1472H Diffuse ⌬F1388/D1472H No 39 *Patient was from consanguineous mating and therefore was homozygous for the G716V mutation (48). Login to comment
94 The first group, including G7R, N24K, F27S, R74W, and E128K, is located in the first transmembrane domain TMD0; the second group, including R495Q, E501K, L503P, F686S, and G716V, is located in the second transmembrane domain TMD1 extending through the first nucleotide binding domain; the third group, including K1337N, L1350Q, S1387F, L1390P, and D1472H, is clustered in the second nucleotide binding domain and the COOH terminus of the protein. Login to comment
118 Results from this assay showed that F27S, R74W, E128K, R495Q, E501K, L503P, F686S, G716V, L1350Q, and D1472H mutant channels had greatly reduced surface expression (Ͻ20% of wild-type level)-whereas G7R and N24K mutant channels displayed modestly decreased surface expression level (Ͼ30% but Ͻ50% of wild-type level) and K1337N, S1378F, and L1390P exhibited normal or mildly reduced expression (Ͼ60% of wild-type level; Fig. 3A). Login to comment
48 TABLE 1 Genetic and clinical information on patients carrying the CHI mutations Mutation Disease Haplotype Diazoxide response References G7R Focal G7R No 44 N24K Diffuse N24K/R1215W No Not reported F27S Focal F27S No 39 R74W Focal R74W/R1215Q No 39,45,46 E128K Diffuse E128K No Not reported R495Q Diffuse R495Q/R1215Q No 39 E501K Focal E501K No 39 L503P Focal L503P No 44 F686S Focal F686S No 39 G716V* Diffuse G716V/G716V No 47,48 K1337N Not done g3992-9a/K1337N Yes 39 L1350Q Focal L1350Q No 44 S1387F Diffuse S1387F/NA No 9,24 L1390P NA L1390P/NA No Not reported D1472H Diffuse èc;F1388/D1472H No 39 *Patient was from consanguineous mating and therefore was homozygous for the G716V mutation (48). Login to comment
95 The first group, including G7R, N24K, F27S, R74W, and E128K, is located in the first transmembrane domain TMD0; the second group, including R495Q, E501K, L503P, F686S, and G716V, is located in the second transmembrane domain TMD1 extending through the first nucleotide binding domain; the third group, including K1337N, L1350Q, S1387F, L1390P, and D1472H, is clustered in the second nucleotide binding domain and the COOH terminus of the protein. Login to comment
119 Results from this assay showed that F27S, R74W, E128K, R495Q, E501K, L503P, F686S, G716V, L1350Q, and D1472H mutant channels had greatly reduced surface expression (b0d;20% of wild-type level)-whereas G7R and N24K mutant channels displayed modestly decreased surface expression level (b0e;30% but b0d;50% of wild-type level) and K1337N, S1378F, and L1390P exhibited normal or mildly reduced expression (b0e;60% of wild-type level; Fig. 3A). Login to comment

[hide] Genotype-phenotype correlations in children with c... J Clin Endocrinol Metab. 2005 Feb;90(2):789-94. Epub 2004 Nov 23. Henwood MJ, Kelly A, Macmullen C, Bhatia P, Ganguly A, Thornton PS, Stanley CA
Genotype-phenotype correlations in children with congenital hyperinsulinism due to recessive mutations of the adenosine triphosphate-sensitive potassium channel genes.
J Clin Endocrinol Metab. 2005 Feb;90(2):789-94. Epub 2004 Nov 23., [PMID:15562009]

Abstract [show]
Congenital hyperinsulinism (HI) is most commonly caused by recessive mutations of the pancreatic beta-cell ATP-sensitive potassium channel (K(ATP)), encoded by two genes on chromosome 11p, SUR1 and Kir6.2. The two mutations that have been best studied, SUR1 g3992-9a and SUR1 delF1388, are null mutations yielding nonfunctional channels and are characterized by nonresponsiveness to diazoxide, a channel agonist, and absence of acute insulin responses (AIRs) to tolbutamide, a channel antagonist, or leucine. To examine phenotypes of other K(ATP) mutations, we measured AIRs to calcium, leucine, glucose, and tolbutamide in infants with recessive SUR1 or Kir6.2 mutations expressed as diffuse HI (n = 8) or focal HI (n = 14). Of the 24 total mutations, at least seven showed evidence of residual K(ATP) channel function. This included positive AIR to both tolbutamide and leucine in diffuse HI cases or positive AIR to leucine in focal HI cases. One patient with partial K(ATP) function also responded to treatment with the channel agonist, diazoxide. Six of the seven patients with partial defects had amino acid substitutions or insertions; whereas, the other patient was compound heterozygous for two premature stop codons. These results indicate that some K(ATP) mutations can yield partially functioning channels, including cases of hyperinsulinism that are fully responsive to diazoxide therapy.

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54 Gene Haplotype Calcium (␮U/ml) Leucine (␮U/ml) Glucose (␮U/ml) Tolbutamide (␮U/ml) Diazoxide responsive Diffuse HI 1 SUR1 delF1388/D1472H 6 2 13 -2 No 2 Kir6.2 G134A/P266L 20 3 36 -2 No 3 SUR1 g3992-9a/g1630ϩ1a 11 16 -2 No 4 SUR1 N188S/D1472N 7 1 7 7 No 5 SUR1 R598X/R999X 32 1 72 27 No 6 SUR1 R495Q/R1215Q -2 15 44 30 No 7 SUR1 R74W/R1215Q 52 28 20 98 No 8 SUR1 g3992-9a/K1337N 2 18 39 33 Yes Focal HI 9 SUR1 F27S 17 -1 16 29 No 10 SUR1 F686S 12 2 27 12 No 11 SUR1 E501K 6 3 9 10 No 12 SUR1 3576delg 9 6 9 12 No 13 SUR1 g3992-9a 5 8 25 9 No 14 SUR1 g3992-9a 3 8 40 21 No 15 SUR1 c2924-10a 4 8 67 29 No 16 Kir6.2 A101D 1 8 177 88 No 17 SUR1 R1215W 7 9 15 6 No 18 Kir6.2 R136L 8 10 115 21 No 19 SUR1 g3992-9a 40 15 35 -0.3 No 20 SUR1 6aa insertion in exon 5 6 16 22 15 No 21 SUR1 R1215W 38 47 58 15 No 22 Kir6.2 R301H 16 55 75 14 No Controls (␮U/ml, mean Ϯ SD) KATP HI (n ϭ 7) 28 Ϯ 16 5 Ϯ 8 12 Ϯ 9 4 Ϯ 6 No GDH-HI (n ϭ 7) 2.3 Ϯ 5.4 42 Ϯ 27 120 Ϯ 52 94 Ϯ 56 Yes Normal (n ϭ 6) 3 Ϯ 4 1.4 Ϯ 2.8 56 Ϯ 26 48 Ϯ 32 Yes a To convert insulin (␮U/ml to pmol/liter), multiply by 6.0. identified in other patients. Login to comment
107 Degree of residual channel function in KATP mutations Null Indeterminate Partial SUR1 g3992-9a g1630ϩ1a R598X/R999X delF1388 N188S/D1472N R495Q/R1215Q F27S 3576delg R74W/R1215Q F686S K1337N E501K 6 aa insertion in exon 5 c2924-10a R1215W Kir6.2 G134A/P266L R301H A101D R136L FIG. 1. Login to comment

[hide] Molecular and immunohistochemical analyses of the ... Mod Pathol. 2006 Jan;19(1):122-9. Suchi M, MacMullen CM, Thornton PS, Adzick NS, Ganguly A, Ruchelli ED, Stanley CA
Molecular and immunohistochemical analyses of the focal form of congenital hyperinsulinism.
Mod Pathol. 2006 Jan;19(1):122-9., [PMID:16357843]

Abstract [show]
Congenital hyperinsulinism is a rare pancreatic endocrine cell disorder that has been categorized histologically into diffuse and focal forms. In focal hyperinsulinism, the pancreas contains a focus of endocrine cell adenomatous hyperplasia, and the patients have been reported to possess paternally inherited mutations of the ABCC8 and KCNJ11 genes, which encode subunits of an ATP-sensitive potassium channel (K(ATP)). In addition, the hyperplastic endocrine cells show loss of maternal 11p15, where imprinted genes such as p57(kip2) reside. In order to evaluate whether all cases of focal hyperinsulinism are caused by this mechanism, 56 pancreatectomy specimens with focal hyperinsulinism were tested for the loss of maternal allele by two methods: immunohistochemistry for p57(kip2) (n=56) and microsatellite marker analysis (n=27). Additionally, 49 patients were analyzed for K(ATP) mutations. Out of 56 focal lesions, 48 demonstrated clear loss of p57(kip2) expression by immunohistochemistry. The other eight lesions similarly showed no nuclear labeling, but the available tissue was not ideal for definitive interpretation. Five of these eight patients had paternal K(ATP) mutations, of which four demonstrated loss of maternal 11p15 within the lesion by microsatellite marker analysis. All of the other three without a paternal K(ATP) mutation showed loss of maternal 11p15. K(ATP) mutation analysis identified 32/49 cases with paternal mutations. There were seven patients with nonmaternal mutations whose paternal DNA material was not available, and one patient with a mutation that was not present in either parent's DNA. These eight patients showed either loss of p57(kip2) expression or loss of maternal 11p15 region by microsatellite marker analysis, as did the remaining nine patients with no identifiable K(ATP) coding region mutations. The combined results from the immunohistochemical and molecular methods indicate that maternal 11p15 loss together with paternal K(ATP) mutation is the predominant causative mechanism of focal hyperinsulinism.

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93 KATP mutationsa Nuclear labeling of p57kip2 Microsatellite marker analysis at 11p15 Remarks on histology Lesion Islets in normal area 1 g3992-9a/ + ND 2 R1494Q/ + ND 3 V21D/ + ND 4 g3992-9a/ + ND 5 3576 del g/ Small lesion + ND 6 R74W/ Small normal area and weak Loss of maternal allele 7 C717X/ + Loss of maternal allele 8 1874 del c/ + ND 9 Q954X/ + ND 10 g3992-9g/ + Loss of maternal allele 11 E501K/ + Loss of maternal allele 12 R136Lb / Weak Loss of maternal allele 13 c2924-9a/ + Loss of maternal allele Focal lesion occupies large area of pancreas 14 g3992-9a/ + ND 15 3084 del g/ + ND 16 R302Hb / + Loss of maternal allele 17 g3992-9a/ + ND 18 536-539 del atgg/ + ND 19 R1215W/ + Loss of maternal allele 20 R999X/ + ND 21 L1350Q/ + ND 22 G1401R/ Weak Loss of maternal allele 23 g2041-21a/ + Loss of maternal allele 24 G7R/ Weak Loss of maternal allele 25 g3992-9a/ + Loss of maternal allele Rare nonadjacent large islet cell nuclei 26 g3992-9a/ + ND 27 Q954X/ + ND 28 delF1388/ + ND 29 Q472X/ + ND 30 G40Db / + Loss of maternal allele 31 S116Pb / + ND 32 g3992-9a/ + ND 33 g2116+1t, nonmaternal + ND 34 A101Db , nonmaternal Small normal area Loss of maternal allele Focal lesion occupies large area of pancreas 35 F27S, nonmaternal Weak Loss of maternal allele 36 G1379R, nonmaternal + ND 37 1631 del t, nonmaternal + ND 38 R1215W, nonmaternal + Loss of maternal allele 39 L503P, nonmaternal + Loss of maternal allele 40 F686S, de novo + Loss of maternal allele 41 1332+4 del c, maternalc + Loss of maternal allele 42 / + Loss of maternal allele 43 / + ND 44 / Small lesion + Loss of maternal allele 45 / + Loss of maternal allele 46 / + Loss of maternal allele 47 / + ND 48 / + Loss of maternal allele 49 / + ND 50 ND + ND 51 ND + ND 52 ND + Loss of maternal allele Rare nonadjacent large islet cell nuclei 53 ND + Loss of maternal allele Focal lesion occupies large area of pancreas All 10 pancreatic specimens studied from patients with diffuse hyperinsulinism did not show loss of p57kip2 labeling of the islet cell nuclei (data not shown). Login to comment
103 One individual (no. 40) was found to have an F686S point mutation which was not identified in either parent. Login to comment

[hide] Engineered Kir6.2 mutations that correct the traff... Channels (Austin). 2013 Jul-Aug;7(4):313-7. Epub 2013 May 21. Zhou Q, Pratt EB, Shyng SL
Engineered Kir6.2 mutations that correct the trafficking defect of K(ATP) channels caused by specific SUR1 mutations.
Channels (Austin). 2013 Jul-Aug;7(4):313-7. Epub 2013 May 21., [PMID:23695995]

Abstract [show]
KATP channels consisting of Kir6.2 and SUR1 couple cell metabolism to membrane excitability and regulate insulin secretion. The molecular interactions between SUR1 and Kir6.2 that govern channel gating and biogenesis are incompletely understood. In a recent study, we showed that a SUR1 and Kir6.2 mutation pair, E203K-SUR1 and Q52E-Kir6.2, at the SUR1/Kir6.2 interface near the plasma membrane increases the ATP-sensitivity of the channel by nearly 100-fold. Here, we report the finding that the same mutation pair also suppresses channel folding/trafficking defects caused by select SUR1 mutations in the first transmembrane domain of SUR1. Analysis of the contributions from individual mutations, however, revealed that the correction effect is attributed largely to Q52E-Kir6.2 alone. Moreover, the correction is dependent on the negative charge of the substituting amino acid at the Q52 position in Kir6.2. Our study demonstrates for the first time that engineered mutations in Kir6.2 can correct the biogenesis defect caused by specific mutations in the SUR1 subunit.

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16 Of the three TMD0 mutations tested, F27S and A116P showed a clear upper band in addition to the lower immature band in the E203K//Q52E background; by contrast, the same trafficking mutations placed in the background without the E203K//Q52E mutations only exhibited the lower band (Fig. 2), indicating the proteins were retained in the ER as reported previously.25,26 Another TMD0 mutation, E128K, as well as three other previously identified, congenital hyperinsulinism-causing SUR1 trafficking mutations outside of TMD0 (R495Q, F686S and L1350Q),25 however, showed no improvement in their processing efficiency when combined with E203K//Q52E (data not shown). Login to comment

[hide] Pharmacological rescue of trafficking-impaired ATP... Front Physiol. 2013 Dec 24;4:386. doi: 10.3389/fphys.2013.00386. Martin GM, Chen PC, Devaraneni P, Shyng SL
Pharmacological rescue of trafficking-impaired ATP-sensitive potassium channels.
Front Physiol. 2013 Dec 24;4:386. doi: 10.3389/fphys.2013.00386., [PMID:24399968]

Abstract [show]
ATP-sensitive potassium (KATP) channels link cell metabolism to membrane excitability and are involved in a wide range of physiological processes including hormone secretion, control of vascular tone, and protection of cardiac and neuronal cells against ischemic injuries. In pancreatic beta-cells, KATP channels play a key role in glucose-stimulated insulin secretion, and gain or loss of channel function results in neonatal diabetes or congenital hyperinsulinism, respectively. The beta-cell KATP channel is formed by co-assembly of four Kir6.2 inwardly rectifying potassium channel subunits encoded by KCNJ11 and four sulfonylurea receptor 1 subunits encoded by ABCC8. Many mutations in ABCC8 or KCNJ11 cause loss of channel function, thus, congenital hyperinsulinism by hampering channel biogenesis and hence trafficking to the cell surface. The trafficking defects caused by a subset of these mutations can be corrected by sulfonylureas, KATP channel antagonists that have long been used to treat type 2 diabetes. More recently, carbamazepine, an anticonvulsant that is thought to target primarily voltage-gated sodium channels has been shown to correct KATP channel trafficking defects. This article reviews studies to date aimed at understanding the mechanisms by which mutations impair channel biogenesis and trafficking and the mechanisms by which pharmacological ligands overcome channel trafficking defects. Insight into channel structure-function relationships and therapeutic implications from these studies are discussed.

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218 Mutation Domain Rescue Rescue Gating References by SU by CBZ property SUR1 G7R TMD0 Yes Yes Normal Yan et al., 2007 N24K TMD0 Yes Yes Normal Yan et al., 2007 F27S TMD0 Yes Yes Normal Yan et al., 2007 R74W TMD0 Yes Yes ATP-insensitive Yan et al., 2007 A116P TMD0 Yes Yes Normal Yan et al., 2004 E128K TMD0 Yes Yes ATP-insensitive Yan et al., 2007 V187D TMD0 Yes Yes Normal Yan et al., 2004 R495Q TMD1 Yes Yes Unknown Yan et al., 2007 E501K TMD1 Yes Yes Unknown Yan et al., 2007 L503P TMD1 No No Unknown Yan et al., 2007 F686S NBD1 No No Unknown Yan et al., 2007 G716V NBD1 No No Unknown Yan et al., 2007 E1324K TMD2 N.D.3 N.D. Login to comment