ABCMdb

PMID: 22562119

Lin YW, Akrouh A, Hsu Y, Hughes N, Nichols CG, De Leon DD
Compound heterozygous mutations in the SUR1 (ABCC 8) subunit of pancreatic K(ATP) channels cause neonatal diabetes by perturbing the coupling between Kir6.2 and SUR1 subunits.
Channels (Austin). 2012 Mar-Apr;6(2):133-8. doi: 10.4161/chan.19980. Epub 2012 Mar 1., [PubMed]

Sentences

No. Mutations Sentence Comment

8 ABCC8 p.Gly296Arg ABCC8 p.Ala30Val Here, we report a case of diabetes in a 7-mo old child with compound heterozygous mutations in ABCC8 (SUR1[A30V] and SUR1[G296R]). Login to comment 11 ABCC8 p.Gly296Arg Experiments on excised inside-out patches also reveal a slight increase in activity, manifested as an enhancement in stimulation by MgADP in channels expressing the compound heterozygous mutations or homozygous G296R mutation. Login to comment 12 ABCC8 p.Gly296Arg ABCC8 p.Ala30Val ABCC8 p.Ala30Val ABCC8 p.Ala30Val In addition, the IC50 for ATP inhibition of homomeric A30V channels was increased ~6-fold, and was increased ~3-fold for both heteromeric A30V + WT channels or compound heterozygous (A30V + G296R) channels. Login to comment 32 ABCC8 p.Gly296Arg ABCC8 p.Ala30Val Direct sequencing of his DNA revealed two mutations in the ABCC8 gene c.886 G > A (G296R) and c.89 C > T (A30V), the first of which is maternally derived and the second is paternally derived. Login to comment 41 ABCC8 p.Gly296Arg ABCC8 p.Gly296Arg ABCC8 p.Ala30Val ABCC8 p.Ala30Val As shown in Figure 1A, neither heteromeric single mutant channels ([A30V + WT], referred to as hetA30V and [G296R + WT], referred to as hetG296R) nor compound heterozygous channels ([A30V + G296R]) exhibited significantly different maximum 86 Rb+ efflux rates in the presence of metabolic inhibitors. Login to comment 53 ABCC8 p.Gly296Arg ABCC8 p.Ala30Val ABCC8 p.Ala30Val k2,basal /k2,MI calculated from WT, het A30V, het G296R and SUR1[A30V + G296R] are 0.07 &#b1; 0.005, 0.08 &#b1; 0.01, 0.1 &#b1; 0.01 and 0.16 &#b1; 0.01 (n = 4-9). Login to comment 56 ABCC8 p.Gly296Arg ABCC8 p.Ala30Val Homozygous G296R channels exhibit a slightly right-shifted dose-response, but homozygous A30V channels exhibit a marked and significantly right-shifted ATP sensitivity (Fig. 4B). Login to comment 57 ABCC8 p.Gly296Arg ABCC8 p.Ala30Val In the heteromeric case, mimicking the disease condition, hetG296R channels are not markedly different from WT, but hetA30V and compound heterozygous A30V + G296R channels both exhibit a significant rightward shift when compared with WT channels (Fig. 4C). Login to comment 64 ABCC8 p.Gly296Arg ABCC8 p.Ala30Val A30V and G296R mutants are located at the TMD0 and the cytosolic linker region (L0) of SUR1 3 (Fig. 2). Login to comment 66 ABCC8 p.Gly296Arg ABCC8 p.Gly296Arg ABCC8 p.Ala30Val ABCC8 p.Ala30Val Here we characterized the sensitivity to MgADP activation, as well as inhibitory ATP sensitivity (without Mg2+ ), of homomeric A30V channels (labeled as homA30V), homomeric G296R channels (labeled as homG296R), hetA30V, hetG296R and compound heterozygous channels [A30V + G296R].8,18,19 Representative recordings of channel response to MgADP from WT and compound heterozygous mutants are shown in Figure 3A and summary results are shown in Figure 3B. Login to comment 67 ABCC8 p.Gly296Arg ABCC8 p.Ala30Val Homomeric G296R channels exhibit dramatically increased MgADP activity, while homomeric A30V channels show no significant enhancement (Fig. 3B). Login to comment 69 ABCC8 p.Ala30Val On the other hand, it is noticeable that A30V homomeric channels show significant increased current in 0.1 mM MgATP, reflecting an additive consequence of the two distinct mutant effects (Fig. 3B). Login to comment 71 ABCC8 p.Ala30Val Given that homomeric A30V channels showed greatly reduced ATP sensitivity in 0.1 mM ATP (with 0.5 mM free Mg2+ ), we characterized the sensitivity to inhibitory ATP, without any confounding effects of Mg-nucleotides. Login to comment 74 ABCC8 p.Ala30Val Membrane topology of SUR1 and the predicted locations of A30V and 296R. Login to comment 75 ABCC8 p.Gly296Arg ABCC8 p.Ala30Val The red filled circles indicate the predicted positions for A30V at the N terminus of its 1st transmembrane domain (TMD0) and G296R at the L0 linker region before TMD1 domain. Login to comment 79 ABCC8 p.Gly296Arg ABCC8 p.Ala30Val Representative inside-out patch clamp recordings of WT and A30V + G296R in different MgATP and MgADP concentrations (A). Login to comment 81 ABCC8 p.Gly296Arg ABCC8 p.Ala30Val (B) Relative channel currents in 0.1 mM MgATP and plus 0.5 mM MgADP for WT, homA30V, homG296R, hetA30V, hetG296R and compound heterozygous [A30V + G296R] channels as indicated. Login to comment 85 ABCC8 p.Gly296Arg Interestingly, the G296R variant was identified as a rare variant in whole exome sequencing of over 1,000 individuals (http://evs. Login to comment 90 ABCC8 p.Gly296Arg Although the standard definition of neonatal diabetes refers to diabetes presenting in the first 6 mo of life,20 not uncommonly, like in our case, presentation is beyond this age, prompting some to propose to replace the term "neonatal diabetes mellitus" with "diabetes mellitus of infancy".21 Each ABCC8 mutation carried by this child makes a unique contribution to enhancement of channel activity, resulting in marked stimulation of basal Rb efflux only in the compound heterozygous case (Fig. 1B and C), and explaining the presentation of the disease in the proband, as well as the responsivity to sulfonylureas.22,23 The G296R mutation is inherited from the Figure 4. Login to comment 92 ABCC8 p.Gly296Arg ABCC8 p.Ala30Val (A) Representative currents recorded by inside-out excised patch-clamp technique from COSm6 cells expressing WT, homA30V, homG296R and [A30V + G296R] at +50 mV pipette potential. Patches were exposed to different concentrations of Mg-free ATP as indicated. Login to comment 96 ABCC8 p.Gly296Arg ABCC8 p.Ala30Val Fitted K1/2 for WT, homA30V and homG296R channels are 9.65, 53.31 and 28.11 (in bc;M) and the Hill coefficients are 1.22, 1.04 and 1.19, respectively. (C) The fitted K1/2 for WT, hetA30V, hetG296R and [A30V + G296R] are 9.65, 25.75, 12.75 and 25.45 (in bc;M) and the Hill coefficients are 1.22, 1.28, 1.29 and 1.23, respectively. from the child and both parents. Login to comment 98 ABCC8 p.Gly296Arg ABCC8 p.Ala30Val Two mutations were found in ABCC8 in the proband: c.886 G > A, predicted to cause a G296R amino acid change, was maternally transmitted, and c.89 C > T, predicted to cause A30V amino acid change, was paternally transmitted. Login to comment 117 ABCC8 p.Leu213Arg The cytosolic linker L0 domain has also been proposed to directly transduce the Mg-nucleotide stimulatory action from the SUR1 core to the Kir6.2 pore14 and a previous study demonstrated that another NDM mutation (L213R) in the L0 region also shifts intrinsic ATP sensitivity.13 The present study thus provides further evidence that mutations in the TMD0-L0 region alter the KATP channel activity and further supports the hypothesis that TMD0-L0 is closely associated with Kir6.2. Login to comment 125 ABCC8 p.Gly296Arg ABCC8 p.Ala30Val (A) Representative currents recorded by inside-out excised patch-clamp technique from COSm6 cells expressing WT and [A30V + G296R] at +50 mV pipette potential. Patches were exposed to different concentrations of glibenclamide as indicated (free Mg-nucleotide). Login to comment 170 ABCC8 p.Leu225Pro A mutation in the TMD0-L0 region of sulfonylurea receptor-1 (L225P) causes permanent neonatal diabetes mellitus (PNDM). Login to comment