ABCMdb

ABCC8 p.Val324Met

Predicted by SNAP2:	A: D (71%), C: D (59%), D: D (85%), E: D (85%), F: D (71%), G: D (75%), H: D (75%), I: N (87%), K: D (85%), L: D (59%), M: D (59%), N: D (80%), P: D (91%), Q: D (80%), R: D (85%), S: D (80%), T: N (53%), W: D (85%), Y: D (80%),
Predicted by PROVEAN:	A: D, C: D, D: D, E: D, F: D, G: D, H: D, I: N, K: D, L: N, M: N, N: D, P: D, Q: D, R: D, S: D, T: N, W: D, Y: D,

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[hide] Mutations in the ABCC8 gene encoding the SUR1 subu... Diabetes Obes Metab. 2007 Nov;9 Suppl 2:28-39. Patch AM, Flanagan SE, Boustred C, Hattersley AT, Ellard S
Mutations in the ABCC8 gene encoding the SUR1 subunit of the KATP channel cause transient neonatal diabetes, permanent neonatal diabetes or permanent diabetes diagnosed outside the neonatal period.
Diabetes Obes Metab. 2007 Nov;9 Suppl 2:28-39., [PMID:17919176]

Abstract [show]
AIM: Mutations in the ABCC8 gene encoding the SUR1 subunit of the pancreatic ATP-sensitive potassium channel cause permanent neonatal diabetes mellitus (PNDM) and transient neonatal diabetes mellitus (TNDM). We reviewed the existing literature, extended the number of cases and explored genotype-phenotype correlations. METHODS: Mutations were identified by sequencing in patients diagnosed with diabetes before 6 months without a KCNJ11 mutation. RESULTS: We identified ABCC8 mutations in an additional nine probands (including five novel mutations L135P, R306H, R1314H, L438F and M1290V), bringing the total of reported families to 48. Both dominant and recessive mutations were observed with recessive inheritance more common in PNDM than TNDM (9 vs. 1; p < 0.01). The remainder of the PNDM probands (n = 12) had de novo mutations. Seventeen of twenty-five children with TNDM inherited their heterozygous mutation from a parent. Nine of these parents had permanent diabetes (median age at diagnosis: 27.5 years, range: 13-35 years). Recurrent mutations of residues R1183 and R1380 were found only in TNDM probands and dominant mutations causing PNDM clustered within exons 2-5. CONCLUSIONS: ABCC8 mutations cause PNDM, TNDM or permanent diabetes diagnosed outside the neonatal period. There is some evidence that the location of the mutation is correlated with the clinical phenotype.

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161 Affected probands and family members can be separated into three distinct groups based T229I/T229I ABCC8 mutations Transient Neonatal Diabetes Mellitus Recessive homozygous mutations R826W (2) H1024Y R1183Q (2) R1183W (5) R1314H R1380C (3) R1380H R1380L (2) D209E D212I D212N R306H V324M C435R L451P L582V (2) Dominant heterozygous mutations Permanent Neonatal Diabetes Mellitus E382K/E382K A1185E/A1185E Mosaic N72S Recessive homozygous or mosaic mutations P45L/G1401R E208K/Y263D T229I/V1523L L438F/M1290V P207S/c.536del4 E1327K+V1523A/ c.1327ins10 Recessive compound heterozygous mutations 1K Dominant heterozygous mutations D209E Q21 L213R L225P(2) I1425V V86A V86G F132L (2) F132V L135P Fig. 2 A diagram illustrating the inheritance of ABCC8 mutations in probands with permanent and transient forms of neonatal diabetes. Login to comment
163 Permanent Neonatal Diabetes Mellitus Transient Neonatal Diabetes Mellitus 1 5 10 15 20 25 30 35 39 N72S V86A V86G F132L F132V L135PP45L P207S E208K D209E Q211K L213R L225P T229I Y263D D209E D212I D212N T229I R306H V324M L438F L451P E382K R826W R1183W R1183Q A1185E E1327K R1314H M1290V R1380C R1380H R1380L G1401R V1523A V1523L H1024YC435R L582V I1425V Fig. 3 The location of missense mutations causing neonatal diabetes within the coding sequence of ABCC8. Login to comment
176 No neurological features were reported in R1183W/Q A1185E E1327K G1401R V1523A/L NBD1 NBD2 outside membrane inside P45L N72S F132L/V L135P P207S E208K D209E Q211K D212I/N L213R L225P T229I Y263D E382K V86A/G L438F C435R R1380C/H/L L451P R826W TMD0 TMD1 TMD2 R306H V324M L582V H1024Y I1425V R1314H M1290V Fig. 4 A schematic of the membrane topologies of SUR1 showing the location of the ABCC8 missense mutations causing neonatal diabetes. Login to comment

[hide] Permanent neonatal diabetes due to activating muta... Rev Endocr Metab Disord. 2010 Sep;11(3):193-8. Edghill EL, Flanagan SE, Ellard S
Permanent neonatal diabetes due to activating mutations in ABCC8 and KCNJ11.
Rev Endocr Metab Disord. 2010 Sep;11(3):193-8., [PMID:20922570]

Abstract [show]
The ATP-sensitive potassium (K(ATP)) channel is composed of two subunits SUR1 and Kir6.2. The channel is key for glucose stimulated insulin release from the pancreatic beta cell. Activating mutations have been identified in the genes encoding these subunits, ABCC8 and KCNJ11, and account for approximately 40% of permanent neonatal diabetes cases. The majority of patients with a K(ATP) mutation present with isolated diabetes however some have presented with the Developmental delay, Epilepsy and Neonatal Diabetes syndrome. This review focuses on mutations in the K(ATP) channel which result in permanent neonatal diabetes, we review the clinical and functional effects as well as the implications for treatment.

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85 One of the most notable R1183W/Q A1185E E1327K G1401R V1523A/L V1524M R1531A NBD1 NBD2 outside membrane inside P45L N72S F132L/V L135P P207S E208K D209E Q211K D212I/N L213R L225P T229I Y263D A269D/N E382K V86A/G R1380C/H/L C435R L438F M1290V L451P R826W R1314H TMD0 TMD1 TMD2 R306H V324M L582V H1024Y I1425V A90V Y356C R521Q N1123D R1153G T1043TfsX74 Fig. 3 Schematic representation of 50 ABCC8 mutations which cause neonatal diabetes. Login to comment

[hide] Review. SUR1: a unique ATP-binding cassette protei... Philos Trans R Soc Lond B Biol Sci. 2009 Jan 27;364(1514):257-67. Aittoniemi J, Fotinou C, Craig TJ, de Wet H, Proks P, Ashcroft FM
Review. SUR1: a unique ATP-binding cassette protein that functions as an ion channel regulator.
Philos Trans R Soc Lond B Biol Sci. 2009 Jan 27;364(1514):257-67., [PMID:18990670]

Abstract [show]
SUR1 is an ATP-binding cassette (ABC) transporter with a novel function. In contrast to other ABC proteins, it serves as the regulatory subunit of an ion channel. The ATP-sensitive (KATP) channel is an octameric complex of four pore-forming Kir6.2 subunits and four regulatory SUR1 subunits, and it links cell metabolism to electrical activity in many cell types. ATPase activity at the nucleotide-binding domains of SUR results in an increase in KATP channel open probability. Conversely, ATP binding to Kir6.2 closes the channel. Metabolic regulation is achieved by the balance between these two opposing effects. Precisely how SUR1 talks to Kir6.2 remains unclear, but recent studies have identified some residues and domains that are involved in both physical and functional interactions between the two proteins. The importance of these interactions is exemplified by the fact that impaired regulation of Kir6.2 by SUR1 results in human disease, with loss-of-function SUR1 mutations causing congenital hyperinsulinism and gain-of-function SUR1 mutations leading to neonatal diabetes. This paper reviews recent data on the regulation of Kir6.2 by SUR1 and considers the molecular mechanisms by which SUR1 mutations produce disease.

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204 (a) (b) P45L N72S F132L NH2 A90V V86G COOHL135P exoplasmic cytoplasmic Walker A Walker A linker Walker B linker Walker B V324M E382K C435R L438F L582V R826W H1023Y N1122D R1183Q A1185E R1314H E1327K R1380 L I1425V V1524 L P207S E208K Q211K D212I/N L225P T229I Y263D A269D R306H D209E L213R TMD0 TMD1 TMD2 NBD1 NBD2 CL3 linker site 1 site 2 NBD1 NBD2 R826W R1380 L E1327K I1425V V1524 L Figure 5. Login to comment
207 (a) (b) P45L N72S F132L NH2 A90V V86G COOH L135P exoplasmic cytoplasmic Walker A Walker A linker Walker B linker Walker B V324M E382K C435R L438F L582V R826W H1023Y N1122D R1183Q A1185E R1314H E1327K R1380 L I1425V V1524 L P207S E208K Q211K D212I/N L225P T229I Y263D A269D R306H D209E L213R TMD0 TMD1 TMD2 NBD1 NBD2 CL3 linker site 1 site 2 NBD1 NBD2 R826W R1380 L E1327K I1425V V1524 L Figure 5. Login to comment

[hide] Permanent diabetes during the first year of life: ... Diabetologia. 2011 Jul;54(7):1693-701. Epub 2011 Mar 10. Russo L, Iafusco D, Brescianini S, Nocerino V, Bizzarri C, Toni S, Cerutti F, Monciotti C, Pesavento R, Iughetti L, Bernardini L, Bonfanti R, Gargantini L, Vanelli M, Aguilar-Bryan L, Stazi MA, Grasso V, Colombo C, Barbetti F
Permanent diabetes during the first year of life: multiple gene screening in 54 patients.
Diabetologia. 2011 Jul;54(7):1693-701. Epub 2011 Mar 10., [PMID:21544516]

Abstract [show]
AIMS/HYPOTHESIS: The aim of this study was to investigate the genetic aetiology of permanent diabetes mellitus with onset in the first 12 months of age. METHODS: We studied 46 probands with permanent, insulin-requiring diabetes with onset within the first 6 months of life (permanent neonatal diabetes mellitus [PNDM]/monogenic diabetes of infancy [MDI]) (group 1) and eight participants with diabetes diagnosed between 7 and 12 months of age (group 2). KCNJ11, INS and ABCC8 genes were sequentially sequenced in all patients. For those who were negative in the initial screening, we examined ERN1, CHGA, CHGB and NKX6-1 genes and, in selected probands, CACNA1C, GCK, FOXP3, NEUROG3 and CDK4. The incidence rate for PNDM/MDI was calculated using a database of Italian patients collected from 1995 to 2009. RESULTS: In group 1 we found mutations in KCNJ11, INS and ABCC8 genes in 23 (50%), 9 (19.5%) and 4 (8.6%) patients respectively, and a single homozygous mutation in GCK (2.1%). In group 2, we identified one incidence of a KCNJ11 mutation. No genetic defects were detected in other loci. The incidence rate of PNDM/MDI in Italy is estimated to be 1:210,287. CONCLUSIONS/INTERPRETATION: Genetic mutations were identified in ~75% of non-consanguineous probands with PNDM/MDI, using sequential screening of KCNJ11, INS and ABCC8 genes in infants diagnosed within the first 6 months of age. This percentage decreased to 12% in those with diabetes diagnosed between 7 and 12 months. Patients belonging to the latter group may either carry mutations in genes different from those commonly found in PNDM/MDI or have developed an early-onset form of autoimmune diabetes.

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41 The other patient (group 2) Table 1 Clinical and genetic features of patients with diabetes onset within the first year of life studied in the present investigation Patient T1D autoantibodies tested Age at onset (days) Gene variant Other features SU treatment Group 1 nd-VI/1 ICA, GADA, IA-2A 1 KCNJ11/V59A DEND Yes nd-BR/1 None 2 - Diarrhoea nd-RM/4 IAA, GADA, IA-2A 2 KCNJ11/R201S Yes nd-MI/3 IAA, GADA, IA-2A, ZnT8A 2 KCNJ11/R201C Yes nd-PD/2 None 3 ABCC8/L213P DEND Yes nd-FI/1 None 15 ABCC8/V324M; ABCC8/W688R Yes nd-CT/2 None 27 - nd-MI/2 ICA, GADA, IA-2A 38 KCNJ11/K170R Yes nd-LE/2 ICA, IAA, GADA, IA-2A 39 - nd-PR/2 None 40 ABCC8/L213P iDEND Yes nd-NA/1 None 40 KCNJ11/R201C Yes + insulin nd-CT/1 none 60 KCNJ11/V59M iDEND Yes nd-NA/2 ICA, GADA, IA-2A 71 ABCC8/A355T Anaemia Yes + insulin nd-MO/3 ICA, IAA, GADA 73 KCNJ11/H46Y Yes nd-RM/4 IAA, GADA, IA-2A 80 - nd-TO/3 GADA, IA-2A 82 - nd-TS/2 None 120 KCNJ11/V59M iDEND Yes nd-RM/6 None 120 KCNJ11/R195Ha nd-RM/5 IAA, GADA, IA-2A 135 KCNJ11/E322K Yes nd-PI/1 ICA 141 - nd-BG/1 GADA 180 ABCC8/S1054Na nd-CES/3 None 190 - Group 2 mdi-RM/3 None 220 KCNJ11/V59M iDEND Yes mdi/NA-B/1 ICA 251 - mdi-PA/1 ICA, IAA, GADA, IA-2A 270 - mdi-RM-OBG/1 IAA, GADA 289 - Muscle hypotrophy mdi-CES/1 ICA, IAA 300 - mdi-RM-OBG/3 IAA, GADA, IA-2A 330 - mdi-RM-OBG/2 IAA, GADA, IA-2A 330 - mdi-NA/2 GADA, IA-2A 354 - SU treatment denotes complete withdrawal of insulin therapy unless specified. Login to comment
74 Of our patients, one proband was a compound heterozygote for the ABCC8/V324M mutation, previously described in patients with the transient form of the disease (TNDM) [36], who usually need insulin therapy for less than 1 year [4], and for the novel W688R (c.2062T>G) mutation (nd-FI/1). Login to comment
76 Because both of the patient`s parents were deceased, we analysed the grandparents` DNA and confirmed the ABCC8/V324M mutation in the maternal grandfather and the ABCC8/ W688R mutation in the paternal grandmother (Fig. 1). Login to comment
77 After identifying the mutations, an OGTT was done in both patients; the carrier for V324M was diagnosed with diabetes (2 h plasma glucose 14 mmol/l) and the carrier for W688R presented with impaired glucose tolerance (2 h plasma glucose 8.4 mmol/l). Login to comment
90 V324M T2D 74 years 74 years - W688R IGT 70 years 70 years - V324M/W688R PNDM/MDI 15 days 17 years INS Family nd-FI/1 I. II. III. Login to comment
92 For the two grandparents of proband nd-FI/1, OGTT tests were performed at 70 (W688R) and 74 (V324M) years of age. Login to comment
98 The latter was found in a patient who also carried the TNDM-causing ABCC8/V324M mutation [36]. Login to comment
100 In our case, however, we favour the hypothesis that both ABCC8/V324M and ABCC8/W688R are mildly activating, based on the fact that W688R is associated with impaired glucose tolerance in the paternal grandmother. Login to comment

[hide] Mechanism of KATP hyperactivity and sulfonylurea t... FEBS Lett. 2011 Nov 16;585(22):3555-9. Epub 2011 Oct 19. Babenko AP, Vaxillaire M
Mechanism of KATP hyperactivity and sulfonylurea tolerance due to a diabetogenic mutation in L0 helix of sulfonylurea receptor 1 (ABCC8).
FEBS Lett. 2011 Nov 16;585(22):3555-9. Epub 2011 Oct 19., [PMID:22020219]

Abstract [show]
Activating mutations in different domains of the ABCC8 gene-coded sulfonylurea receptor 1 (SUR1) cause neonatal diabetes. Here we show that a diabetogenic mutation in an unexplored helix preceding the ABC core of SUR1 dramatically increases open probability of (SUR1/Kir6.2)(4) channel (KATP) by reciprocally changing rates of its transitions to and from the long-lived, inhibitory ligand-stabilized closed state. This kinetic mechanism attenuates ATP and sulfonylurea inhibition, but not Mg-nucleotide stimulation, of SUR1/Kir6.2. The results suggest a key role for L0 helix in KATP gating and together with previous findings from mutant KATP clarify why many patients with neonatal diabetes require high doses of sulfonylureas.

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113 Previous studies showed that ND mutations in every major domain of the ABC core of SUR1 can increase KATP PO via A type mechanism (reviewed in [9,10]; see also [25] on V324M in TMD1). Login to comment

[hide] Neonatal diabetes caused by mutations in sulfonylu... J Clin Endocrinol Metab. 2010 Dec;95(12):E473-8. Epub 2010 Sep 1. Zhou Q, Garin I, Castano L, Argente J, Munoz-Calvo MT, Perez de Nanclares G, Shyng SL
Neonatal diabetes caused by mutations in sulfonylurea receptor 1: interplay between expression and Mg-nucleotide gating defects of ATP-sensitive potassium channels.
J Clin Endocrinol Metab. 2010 Dec;95(12):E473-8. Epub 2010 Sep 1., [PMID:20810569]

Abstract [show]
CONTEXT: ATP-sensitive potassium (KATP) channels regulate insulin secretion by coupling glucose metabolism to beta-cell membrane potential. Gain-of-function mutations in the sulfonylurea receptor 1 (SUR1) or Kir6.2 channel subunit underlie neonatal diabetes. OBJECTIVE: The objective of the study was to determine the mechanisms by which two SUR1 mutations, E208K and V324M, associated with transient neonatal diabetes affect KATP channel function. DESIGN: E208K or V324M mutant SUR1 was coexpressed with Kir6.2 in COS cells, and expression and gating properties of the resulting channels were assessed biochemically and electrophysiologically. RESULTS: Both E208K and V324M augment channel response to MgADP stimulation without altering sensitivity to ATP4- or sulfonylureas. Surprisingly, whereas E208K causes only a small increase in MgADP response consistent with the mild transient diabetes phenotype, V324M causes a severe activating gating defect. Unlike E208K, V324M also impairs channel expression at the cell surface, which is expected to dampen its functional impact on beta-cells. When either mutation was combined with a mutation in the second nucleotide binding domain of SUR1 previously shown to abolish Mg-nucleotide response, the activating effect of E208K and V324M was also abolished. Moreover, combination of E208K and V324M results in channels with Mg-nucleotide sensitivity greater than that seen in individual mutations alone. CONCLUSION: The results demonstrate that E208K and V324M, located in distinct domains of SUR1, enhance transduction of Mg-nucleotide stimulation from the SUR1 nucleotide binding folds to Kir6.2. Furthermore, they suggest that diabetes severity is determined by interplay between effects of a mutation on channel expression and channel gating.

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1 Objective: The objective of the study was to determine the mechanisms by which two SUR1 mutations, E208K and V324M, associated with transient neonatal diabetes affect KATP channel function. Login to comment
2 Design: E208K or V324M mutant SUR1 was coexpressed with Kir6.2 in COS cells, and expression and gatingpropertiesoftheresultingchannelswereassessedbiochemicallyandelectrophysiologically. Login to comment
3 Results: Both E208K and V324M augment channel response to MgADP stimulation without altering sensitivity to ATP4- or sulfonylureas. Login to comment
4 Surprisingly, whereas E208K causes only a small increase in MgADP response consistent with the mild transient diabetes phenotype, V324M causes a severe activating gating defect. Login to comment
5 Unlike E208K, V324M also impairs channel expression at the cell surface, which is expected to dampen its functional impact on beta-cells. Login to comment
6 When either mutation was combined with a mutation in the second nucleotide binding domain of SUR1 previously shown to abolish Mg-nucleotide response, the activating effect of E208K and V324M was also abolished. Login to comment
7 Moreover, combination of E208K and V324M results in channels with Mg-nucleotide sensitivity greater than that seen in individual mutations alone. Login to comment
8 Conclusion: The results demonstrate that E208K and V324M, located in distinct domains of SUR1, enhance transduction of Mg-nucleotide stimulation from the SUR1 nucleotide binding folds to Kir6.2. Login to comment
22 We conducted functional analyses of two SUR1 mutations, E208K and V324M, identified in transient ND (7, 8). Login to comment
23 E208K and V324M located in L0 and TMD1, respectively, cause channel overactivity by enhancing MgADP responsivity, establishing their causal role in ND. Login to comment
24 The enhancement effect on MgADP responsivity is greater in V324M than E208K; however, surface expression of the V324M mutant is significantly reduced, suggesting that the greater gain-of-function gating defect caused by V324M is offset by lower surface expression. Login to comment
25 When combined with a SUR1-NBF2 mutation known to abolish MgADP responsivity, effects of E208K and V324M were also abolished, indicating that these residues are involved in transducing the effect of Mg-nucleotides to channel gating. Login to comment
35 Results Mutations and clinical data E208K and V324M are SUR1 mutations identified in patients diagnosed with ND (7, 8, 12) (Supplemental Table 1). Login to comment
36 The most relevant data of the patient with a V324M mutation, not previously reported, is that at 1 month and 17 d of age she was admitted to the hospital due to general hypotonia with severe hyperglycemia (88.4 mmol/liter) and positive ketonemia. Login to comment
40 No functional studies have been conducted on either E208K or V324M. Login to comment
41 Functional analysis of mutant channels Because not all carriers are symptomatic (7, 8, 12), it is important to determine whether E208K and V324M affect KATP channel function. Login to comment
42 In 86 Rbϩ efflux assays, whereas WT channels exhibited the expected low activity due to inhibition by high intracellular ATP, both E208K and V324M channels yielded greater efflux, with V324M being the most active (Fig. 1A). Login to comment
46 Functional characterization of E208K- and V324M-SUR1 mutations. Login to comment
49 Both E208K and V324M exhibited higher efflux than WT, with the V324M mutant showing the highest activity, confirming that E208K- and V324M-SUR1 are activating KATP channel mutations. Login to comment
52 The mature form of SUR1 is clearly reduced in V324M compared with WT, E208K, or L225P. Login to comment
55 The expression level of V324M is significantly reduced compared with WT (n ϭ 3; *, P Ͻ 0.05 by Student`s t test). Login to comment
57 Representative recordings of WT, V324M, and L225P channels are shown. Login to comment
63 Shown are representative recordings of WT, E208K, and V324M channels in response to 10 or 100 nM glibenclamide. Login to comment
69 Because exit of SUR1 from the ER requires coassembly with Kir6.2, abundance of the upper band correlates with the amount of SUR1 at the cell surface that haspassedERqualitycontrol(9,14).Figure1Bshowsthat whereas in E208K-SUR1 both bands were similar in intensity to WT-SUR1, V324M-SUR1 had a clearly reduced upper band, suggesting that V324M may impair channel trafficking from ER to the plasma membrane. Login to comment
70 Immunofluorescence staining of surface channels showed that V324M is indeed expressed at a reduced level compared with WT or E208K, although staining of permeabilized cells indicated that total V324M SUR1 protein levels were not significantly reduced (Supplemental Fig. 2). Login to comment
71 Surface expression was further quantified by chemiluminescence assays that confirmed markedly reduced surface expression of V324M, in contrast to E208K (56.3 Ϯ 6.3 vs. 93.9 Ϯ 10.1% of WT channels, respectively; Fig. 1B). Login to comment
72 Unaltered or reduced surface expression of E208K or V324M suggests that overactivity results from abnormal channel gating. Login to comment
74 ATP dose-response studies showed that E208K and V324M do not affect channel ATP4- sensi- tivity (Supplemental Fig. 3). Login to comment
77 These experiments showed that V324M markedly increases the Mg-nucleotide response (most evident at the 0.5/0.1 mM ATP/ADP ratio; Fig. 1C), even more so than L225P, another SUR1 mutation reported to cause permanent ND by a similar gating abnormality (15). Login to comment
79 These results indicate that E208K and V324M cause ND by hypersensitizing channels to Mg-nucleotide stimulation. Login to comment
81 To determine whether E208K or V324M affects channel sensitivity to sulfonylureas, we tested channel response to 10 or 100 nM glibenclamide. Login to comment
82 E208K and V324M were inhibited by glibenclamide similar to WT channels at both concentrations (Fig. 1E). Login to comment
83 The effectiveness of glibenclamide in inhibiting V324M channels is consistent with the clinical observation reported previously that recurrent diabetes in a patient bearing this mutation was successfully treated with glibenclamide (8). Login to comment
84 E208K and V324M enhance transduction of MgADP stimulation Stimulation of KATP channels by Mg-nucleotides originates from Mg-nucleotide interactions with NBFs of SUR1. Login to comment
85 E208K and V324M are outside the NBFs, in the TMD0-L0 and TMD1 domains, respectively (Supplemental Fig. 1). Login to comment
88 Combining E208K or V324M with E1507K completely abrogated the enhancement effects of E208K or V324M on Mg-nucleotide responses (Fig. 2A). Login to comment
90 E208K and V324M enhance channel response to MgADP by affecting transduction of the MgADP effect to Kir6.2. Login to comment
93 A, The E1507K inactivating mutation in NBF2 completely abolished the activating effects of E208K or V324M. Login to comment
96 Each bar is the mean Ϯ SEM of 30 (WT), eight (E208K), six (L225P), five (V324M), nine (E208K/L225P), six (E208K/V324M), and six (L225P/V324M) patches. Login to comment
99 (#), P Ͻ 0.05 between E208K/V324M and E208K but the difference between E208K/V324M and V324M is not significant. Login to comment
100 To determine the relationship between the activating effect caused by V324M in TMD1 and that caused by E208K or L225P in TMD0-L0, we compared Mg-nucleotide responsivity in channels harboring a combination of these mutations. Login to comment
101 Currents measured in 0.1 mM ATP (free [Mg2ϩ ] ϳ1 mM) showed that channels harboring double mutations were more active than those with only one mutation such that the effects of E208K, L225P, or V324M are additive. Login to comment
104 Discussion We show that two heterozygous SUR1 mutations, E208K and V324M, identified in patients with transient ND cause KATP channel overactivity by enhancing channel responsivity to Mg-nucleotides without affecting ATP4- or glibenclamide sensitivity. Login to comment
106 Although V324M renders a marked increase in Mg-nucleotide response, even more so than L225P previously reported to cause permanent ND (15), the effect of E208K is subtle, only statistically significant at 0.1 mM ATP/0.1 mM ADP; yet both E208K and V324M are associated with transient ND. Login to comment
108 We previously proposed that in ND surface expression efficiency of a mutant modifies the extent of manifestation of the gating defect to determine diseaseoutcome(18,19).Supportingthis,whereasE208K (and also L225P; Fig. 1B) exhibited surface expression similar to WT, V324M was expressed at only approximately 50% that of WT (Fig. 1B). Login to comment
109 The severe gating defect caused by V324M is likely negated by low expression of the mutant on the beta-cell surface, resulting in a less severe diabetes phenotype than one would predict based solely on gating defects. Login to comment
112 What environmental and genetic factors underlie the wide variations in disease presentation for V324M is an important question to address in the future. Login to comment
113 The activating effects of E208K and V324M were abrogated by a NBF2 mutation that abolishes the MgADP response. Login to comment
117 That the effect of E208K or L225P and of V324M are additive suggests that there may be multiple transduction pathways to regulate Kir6.2 gating. Login to comment
118 Finally, V324M has normal glibenclamide sensitivity despite a markedly increased Mg-nucleotide response. Login to comment
120 Sulfonylureas may block the activating effect of V324M by preventing the initial steps in the NBFs. Login to comment
121 Alternatively, transduction of the glibenclamide blocking effect may employ a pathway separate from that affected by V324M, as suggested for the L225P mutation (15). Login to comment

[hide] New ABCC8 mutations in relapsing neonatal diabetes... Diabetes. 2007 Jun;56(6):1737-41. Epub 2007 Mar 27. Vaxillaire M, Dechaume A, Busiah K, Cave H, Pereira S, Scharfmann R, de Nanclares GP, Castano L, Froguel P, Polak M
New ABCC8 mutations in relapsing neonatal diabetes and clinical features.
Diabetes. 2007 Jun;56(6):1737-41. Epub 2007 Mar 27., [PMID:17389331]

Abstract [show]
Activating mutations in the ABCC8 gene that encodes the sulfonylurea receptor 1 (SUR1) regulatory subunit of the pancreatic islet ATP-sensitive K(+) channel (K(ATP) channel) cause both permanent and transient neonatal diabetes. Recently, we have described the novel mechanism where basal Mg-nucleotide-dependent stimulatory action of SUR1 on the Kir6.2 pore is increased. In our present study, we identified six new heterozygous ABCC8 mutations, mainly in patients presenting the transient form of neonatal diabetes (six of eight), with a median duration of initial insulin therapy of 17 months (range 0.5-38.0). Most of these mutations map to key functional domains of SUR1. Whereas Kir6.2 mutations are a common cause of permanent neonatal diabetes and in a few cases associate with the DEND (developmental delay, epilepsy, and neonatal diabetes) syndrome, SUR1 mutations are more frequent in transient (52%) compared with permanent (14%) neonatal diabetes cases screened for ABCC8 in our series. Although ketoacidosis is frequent at presentation, SUR1 mutations associate mainly with transient hyperglycemia, with possible recurrence later in life. One-half of the SUR1 neonatal diabetic patients presented with de novo mutations. In some familial cases, diabetes is not always present in the adult carriers of SUR1 mutations, supporting variability in their clinical expressivity that remains to be fully explained.

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38 We identified eight heterozygous missense ABCC8 mutations in 8 of the 16 patients with neonatal diabetes, six of which have not yet been reported: E208K (c.622GϾA), A269D (c.806CϾA), V324M (c.970GϾA), R825W (c.2473CϾT), R1379H (c.4136GϾA), and V1523M (c.4567GϾA) (Fig. 1). Login to comment
39 The two other mutations, L582V (c.1744CϾG) and R1182Q (c.3545GϾA), had been previously described by our group in three independent families with TND cases (13). Login to comment
44 V324M is located in the transmembrane domain (TMD)6 of TMD1, and R1379H and V1523M are in the nucleotide-binding domain 2, the domain argued to hydrolyze MgATP. Login to comment
45 A269D and R825W lie in the helical intracellular coupling domains (4). Login to comment
48 We have sequenced both parents of the patients (those carrying an ABCC8 mutation, except in two families of probands CD-R1379H and GK-V324M [only the mother sample was available for genetic testing; see Table 1]). Login to comment
52 The V324M and R1379H mutations tested negative in the mothers, and the two fathers were not available for genetic testing. Login to comment
59 Three TND patients (NJ-A269D, LM-R825W, and GK-V324M) were small for gestational age (Ͻ3rd percentile). Login to comment
61 In patient GK-V324M, recurrence of diabetes occurred at 9 years of age and was treated with insulin injections. Login to comment
62 After ABCC8 sequencing had been performed and after the agreement of the French health authorities had been granted for sulfonylureas treatment in children with a SUR1 mutation, the patient GK-V324M was successfully transferred to glibenclamide (Table 1). Login to comment
63 One patient (CD-R1379H) has a hyperactivity disorder with attention deficit disorder associated with speech developmental delay and feeding behavior anomalies. Login to comment
77 In the ND-SUR1 patients, an apparently mild phenotype, i.e., without neurological features, is observed in the TND families, except in a few cases presenting with PND (13) TABLE1 ClinicalfeaturesinneonataldiabeticpatientsscreenedpositiveforABCC8mutations Patient SGMGKKSLMCNCDDLNJ MutationE208KV324ML582VR825WR1182QR1379HV1523MA269D SexFemaleMaleMaleFemaleFemaleMaleMaleFemale TypeofdiabetesTNDTNDTNDTNDTNDTNDPND Notyet known Atbirth Weight(g/percentile)1,790/321,660/Ͻ33,250/282,300/Ͻ32,930/103,150/432,710/312,390/Ͻ3 Gestationweek33.53739394138.53739 Atpresentation Age(days)1112361013426766 Weight(g)1,7904,2904,3002,5203,0003,6903,6605,100 PresentationGlucose monitoring KetoacidosisKetoacidosisGlucose monitoring WeightlossKetoacidosisKetoacidosisKetoaciduria Glucose(mmol/l)12.424.160.516.824.164.23627.5 Autoantibodies00000000 Insulindose(units⅐kg-1 ⅐day-1 )0.1012.400.300.720.502.500.72 PancreasultrasonographyNANANNNNNN Currentstatus Age(months)712728134833188.7 Height(cm/SD)63/-1.6134.5/-0.790.2/0.672.5/-0.4101.2/0.296/184/1.370/0.8 Weight(kg/percentile)6.15/323.6/Ͻ313.5/759.62/5614.9/5017.5/Ͼ9711/318.52/50 Diabetes(yes[ϩ],no[-])-ϩ(9)*----ϩϩ Insulindose(units⅐kg-1 ⅐day-1 )00†00000.600.62 A1Catlastexamination(%)4.56.05.15.05.45.05.58.9 Neurologicalfeatures MuscleweaknessNoNoNoNoNoNoNoNo MotordevelopmentaldelayNoNoNoNoNoNoNoNo EpilepsyNoNoNoNoNoNoNoNo MentaldevelopmentaldelayNoNoNoNoNoNoNoNo SpeechdevelopmentaldelayNoYesNoNoNoYesNoNo DysmorphicfeaturesNoNoNoNoNoNoNoNo OtherfeaturesNoNoNoNoNoHyperkinesia, troubleof feeding behavior NoHypotonia ParentwithamutationFatherNone‡FatherFatherNoneNone‡NoneMother Glucosetolerance§IGT-NN---N Ageatexamination(year)41-3129---25 A1Catlastexamination(%)¶5.4-6.1NA---5.2 BMIatlastexamination(kg/m2 )27-2422---NA *Ageatrelapse,inyear.†PatientGK-V324Mwassuccessfullyswitchedtoglibenclamide(gliburide)attheageof9.5years(currentdose2.5mg/day;weight25kg).‡Onlythemotherwas screenedforthemutation;thefatherofGK-V324Mdied,andnoinformationisavailableonthebiologicalfatherofCD-R1379H.§Assessedbyanoralglucosetolerancetest.¶Upperlimit ofnormalvaluesforA1C:5.6%.IGT,impairedglucosetolerance;N,normal;NA,notavailable. Login to comment
78 and in one patient previously reported with a SUR1 mutation (F132L) and severe DEND (developmental delay, epilepsy, and neonatal diabetes) syndrome (21). Login to comment
49 We have sequenced both parents of the patients (those carrying an ABCC8 mutation, except in two families of probands CD-R1379H and GK-V324M [only the mother sample was available for genetic testing; see Table 1]). Login to comment
53 The V324M and R1379H mutations tested negative in the mothers, and the two fathers were not available for genetic testing. Login to comment
60 Three TND patients (NJ-A269D, LM-R825W, and GK-V324M) were small for gestational age (b0d;3rd percentile). Login to comment
79 ߥOnly the mother was screened for the mutation; the father of GK-V324M died, and no information is available on the biological father of CD-R1379H. Login to comment

[hide] Mutations in ATP-sensitive K+ channel genes cause ... Diabetes. 2007 Jul;56(7):1930-7. Epub 2007 Apr 19. Flanagan SE, Patch AM, Mackay DJ, Edghill EL, Gloyn AL, Robinson D, Shield JP, Temple K, Ellard S, Hattersley AT
Mutations in ATP-sensitive K+ channel genes cause transient neonatal diabetes and permanent diabetes in childhood or adulthood.
Diabetes. 2007 Jul;56(7):1930-7. Epub 2007 Apr 19., [PMID:17446535]

Abstract [show]
Transient neonatal diabetes mellitus (TNDM) is diagnosed in the first 6 months of life, with remission in infancy or early childhood. For approximately 50% of patients, their diabetes will relapse in later life. The majority of cases result from anomalies of the imprinted region on chromosome 6q24, and 14 patients with ATP-sensitive K+ channel (K(ATP) channel) gene mutations have been reported. We determined the 6q24 status in 97 patients with TNDM. In patients in whom no abnormality was identified, the KCNJ11 gene and/or ABCC8 gene, which encode the Kir6.2 and SUR1 subunits of the pancreatic beta-cell K(ATP) channel, were sequenced. K(ATP) channel mutations were found in 25 of 97 (26%) TNDM probands (12 KCNJ11 and 13 ABCC8), while 69 of 97 (71%) had chromosome 6q24 abnormalities. The phenotype associated with KCNJ11 and ABCC8 mutations was similar but markedly different from 6q24 patients who had a lower birth weight and who were diagnosed and remitted earlier (all P < 0.001). K(ATP) channel mutations were identified in 26 additional family members, 17 of whom had diabetes. Of 42 diabetic patients, 91% diagnosed before 6 months remitted, but those diagnosed after 6 months had permanent diabetes (P < 0.0001). K(ATP) channel mutations account for 89% of patients with non-6q24 TNDM and result in a discrete clinical subtype that includes biphasic diabetes that can be treated with sulfonylureas. Remitting neonatal diabetes was observed in two of three mutation carriers, and permanent diabetes occurred after 6 months of age in subjects without an initial diagnosis of neonatal diabetes.

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71 Ten different ABCC8 gene mutations were identified in 13 probands: D209E (c.627CϾA), D212N (c.634GϾA), D212I (c.634 GϾA 635AϾT), V324M (c.970GϾA), L451P (c.1352TϾC), R826W (c.2476CϾT), R1183W (c.3547CϾT), R1183Q (c.3548GϾA), R1380C (c.4138CϾT), and R1380H (c.4139GϾA). Login to comment
138 TABLE 3 Comparison of clinical and biochemical characteristics of patients with a KATP channel mutation diagnosed before 6 months of age with patients whose diabetes was not diagnosed before age 6 months and the number of each mutation identified within each group Characteristic Mutation carriers diagnosed with diabetes within 6 months Mutation carriers who did not have diabetes diagnosed within the first 6 months P value n (% male) 35 (51) 16 (44) 0.75 Probands (n) 25 0 Age when entering study (years) 6 (0.8-43) 42 (5-56) - Ever diagnosed with diabetes (n) 35 7 1*10-6 Age at diagnosis (weeks) 4 (0-17) 1196 (260 to Ͼ2496) 3.7*10-5 Diabetes remitted (n) 32 0/7 3.7*10-10 Age at remission (weeks) 35 (2-208) - - Diabetes relapsed (n) 7 - - Age at relapse (years) 13 (3-25.5) - - Birth weight (g) 2,695 (1,360-3,570) 2,810 (907-3,090) 0.9 Gestation (weeks) 39 (30-42) 38 (34-40) 0.74 Centile birth weight 18 (Ͻ1st to 89th) 15 (Ͻ1st to 79th) 0.94 KCNJ11 mutations R34C 1 2 G53R 2 0 G53S 2 1 E179A 1 0 I182V 1 0 E227K 4 2 E229K 5 3 R365H 1 1 ABCC8 mutations D209E 1 1 D212N 2 1 D212I 4 0 V324M 1 1 L451P 2 1 R826W 1 0 R1183W 4 2 R1183Q 1 0 R1380C 1 0 R1380H 1 1 Data are median (range), unless otherwise indicated. Login to comment
72 Ten different ABCC8 gene mutations were identified in 13 probands: D209E (c.627Cb0e;A), D212N (c.634Gb0e;A), D212I (c.634 Gb0e;A 635Ab0e;T), V324M (c.970Gb0e;A), L451P (c.1352Tb0e;C), R826W (c.2476Cb0e;T), R1183W (c.3547Cb0e;T), R1183Q (c.3548Gb0e;A), R1380C (c.4138Cb0e;T), and R1380H (c.4139Gb0e;A). Login to comment
139 TABLE 3 Comparison of clinical and biochemical characteristics of patients with a KATP channel mutation diagnosed before 6 months of age with patients whose diabetes was not diagnosed before age 6 months and the number of each mutation identified within each group Characteristic Mutation carriers diagnosed with diabetes within 6 months Mutation carriers who did not have diabetes diagnosed within the first 6 months P value n (% male) 35 (51) 16 (44) 0.75 Probands (n) 25 0 Age when entering study (years) 6 (0.8-43) 42 (5-56) - Ever diagnosed with diabetes (n) 35 7 1*10afa;6 Age at diagnosis (weeks) 4 (0-17) 1196 (260 to b0e;2496) 3.7*10afa;5 Diabetes remitted (n) 32 0/7 3.7*10afa;10 Age at remission (weeks) 35 (2-208) - - Diabetes relapsed (n) 7 - - Age at relapse (years) 13 (3-25.5) - - Birth weight (g) 2,695 (1,360-3,570) 2,810 (907-3,090) 0.9 Gestation (weeks) 39 (30-42) 38 (34-40) 0.74 Centile birth weight 18 (b0d;1st to 89th) 15 (b0d;1st to 79th) 0.94 KCNJ11 mutations R34C 1 2 G53R 2 0 G53S 2 1 E179A 1 0 I182V 1 0 E227K 4 2 E229K 5 3 R365H 1 1 ABCC8 mutations D209E 1 1 D212N 2 1 D212I 4 0 V324M 1 1 L451P 2 1 R826W 1 0 R1183W 4 2 R1183Q 1 0 R1380C 1 0 R1380H 1 1 Data are median (range), unless otherwise indicated. 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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352 In this scenario, the extent of expression of mutant subunit in the cell surface channel population may determine the extent of overall channel gating defect and thus, disease severity as has been proposed for several PNDM mutations, including V324M in SUR1 (Zhou et al., 2010) as well as C42R and Pro226-Pro232 deletion mutation in Kir6.2 (Yorifuji et al., 2005; Lin et al., 2013). Login to comment
356 Mutation Surface expression Gating References increased by SU property SUR1 F132L Yes Increased Po Pratt et al., 2009 V324M N.D. Increased MgADP sensitivity Zhou et al., 2010 Kir6.2 C42R N.D. Increased Po Yorifuji et al., 2005 Q52R Yes Increased Po Proks et al., 2004; Lin et al., 2006a V59G Yes Increased Po Proks et al., 2004; Lin et al., 2006a V59M Yes Increased Po Koster et al., 2005; Lin et al., 2006a R201C Yes Decreased ATP inhibition Proks et al., 2004; Lin et al., 2006a R201H Yes Decreased ATP inhibition Proks et al., 2004; Lin et al., 2006a Pro226_ Pro232del N.D. Increased Po Lin et al., 2013 I296L Yes Increased Po Proks et al., 2005; Lin et al., 2006a CONCLUSIONS AND PERSPECTIVES Pharmacological chaperones have emerged as promising therapeutic tools for treating diseases resulting from defective protein folding and/or trafficking. Login to comment