ABCMdb

PMID: 25926814

Ortiz D, Bryan J
Neonatal Diabetes and Congenital Hyperinsulinism Caused by Mutations in ABCC8/SUR1 are Associated with Altered and Opposite Affinities for ATP and ADP.
Front Endocrinol (Lausanne). 2015 Apr 15;6:48. doi: 10.3389/fendo.2015.00048. eCollection 2015., [PubMed]

Sentences

No. Mutations Sentence Comment

37 ABCC8 p.Glu1506Lys ABCC8 p.Glu1506Asp The E1506D substitution increases the affinity of SUR1 for MgATP while E1506K reduces affinity. Login to comment 38 ABCC8 p.Glu1506Lys In the absence of Mg2+, however, the E1506K substitution increases affinity for ATP4-, supporting the argument that the Mg2+ counterion normally shields the catalytic carboxylate, but is repelled by the substituted lysine. Login to comment 39 ABCC8 p.Glu1506Lys ABCC8 p.Glu1506Asp Both substitutions reduce affinity for MgADP, consistent with electrophysiological data indicating that E1506D and E1506K produce channels that are less sensitive to stimulation by MgADP. Login to comment 91 ABCC8 p.Glu1506Lys ABCC8 p.Glu1506Asp Two substitutions, E1506D and E1506K, causes of ND and CHI, respectively, have opposite effects on the affinity for MgATP Several ND mutations in SUR1 increase the apparent affinity for ATP (8, 9). Login to comment 92 ABCC8 p.Glu1506Lys ABCC8 p.Glu1506Asp To extend these observations two SUR1 substitutions, E1506D and E1506K, well studied at the electrophysiological level (15) and identified with ND and CHI, respectively, were analyzed. Login to comment 98 ABCC8 p.Glu1506Lys The substitution of lysine for glutamate at position 1506 replaces a negative with a positive charge. Login to comment 100 ABCC8 p.Glu1506Lys ABCC8 p.Glu1506Asp Wildtype SUR1 is potentially in a steady-state, slowly hydrolyzing MgATP, while the E1506D and E1506K substitutions are both expected to impair hydrolysis. Login to comment 102 ABCC8 p.Glu1506Lys ABCC8 p.Glu1506Asp Comparison of the approximate EC50 values, 50 mM, 900 &#b5;M and 10 &#b5;M for E1506K, WT and E1506D, respectively, suggests there is an ~5000-fold range in affinities. Login to comment 112 ABCC8 p.Glu1506Lys ABCC8 p.Ile1424Val Mutation Reference KG KT (+Mg2+) b2; KT (-Mg2+) b2; KD (+Mg2+) b2; nM &#b5;M &#b5;M &#b5;M E1506Qa (8) 0.6 &#b1; 0.2 0.9 &#b1; 0.2 40 &#b1; 20 94 &#b1; 9 40 &#b1; 11 211 &#b1; 34 7 .6 &#b1; 2.2 E1506Da (15) 0.4 &#b1; 0.04 3.2 &#b1; 1 8.6 &#b1; 1.5 5570 &#b1; 1200 7 .2 &#b1; 1.5 289 &#b1; 122 4.7 &#b1; 2.2 Q1178Rb (24) 1.0 &#b1; 0.1 9.2 &#b1; 1.3 10 &#b1; 1 1030 &#b1; 200 9.1 &#b1; 1.7 13.9 &#b1; 2.0 20.7 &#b1; 8.9 I1424V (24) 0.5 &#b1; 0.03 7 .1 &#b1; 2.2 5.6 &#b1; 0.7 2840 &#b1; 700 7 .6 &#b1; 1.5 12.1 &#b1; 3.7 14.8 &#b1; 6.5 R1182Qb (24) 0.5 &#b1; 0.15 13.1 &#b1; 2.3 10.3 &#b1; 1.4 11100 &#b1; 1600 4.1 &#b1; 0.4 13.1 &#b1; 2.2 16.4 &#b1; 4.6 WT 0.25 &#b1; 0.02 200 &#b1; 18 13 &#b1; 1 10900 &#b1; 3400 16 &#b1; 11 60 &#b1; 16 14 &#b1; 6.6 S1185Ac (9) 0.3 &#b1; 0.05 416 &#b1; 75 4.9 &#b1; 0.5 19100 &#b1; 3600 6.4 &#b1; 1.5 36.6 &#b1; 8 10.4 &#b1; 2.5 C1174Fc (9) 0.5 &#b1; 0.04 2690 &#b1; 725 5.9 &#b1; 2.3 >20000 13 &#b1; 6 66 &#b1; 13 7 .6 &#b1; 1.7 E1506K (25) 0.3 &#b1; 0.03 8450 &#b1; 1200 5.5 &#b1; 0.6 256 &#b1; 55 5.3 &#b1; 0.4 >1000 n.d. G1479R (26) 0.5 &#b1; 0.04 >10000 n.d. >20000 n.d. >1000 n.d. a Includes data from Ref. (8). Login to comment 118 ABCC8 p.Glu1506Lys Patients with E1506K (27) and G1479R (26, 28) mutations are responsive to diazoxide. Login to comment 119 ABCC8 p.Glu1506Lys ABCC8 p.Glu1506Lys ABCC8 p.Glu1506Asp ABCC8 p.Glu1506Asp ABCC8 p.Glu1506Gln ABCC8 p.Glu1506Gln 10-2 10-1 100 101 102 103 104 105 0.0 0.2 0.4 0.6 0.8 1.0 WT E1506D E1506K E1506Q Specific Bound GBC [MgATP] (&#b5;M) 10 -1 10 0 10 1 10 2 10 3 10 4 10 5 0.0 0.2 0.4 0.6 0.8 1.0 WT E1506K E1506D E1506Q Specific Bound GBC [ATP 4- ] (&#b5;M) B A C FIGURE 2 | (A) Representation of NBD2 based on Sav1866. Login to comment 122 ABCC8 p.Glu1506Lys ABCC8 p.Glu1506Lys ABCC8 p.Ile1424Val ABCC8 p.Ile1424Val ABCC8 p.Gln1178Arg ABCC8 p.Gln1178Arg ABCC8 p.Arg1182Gln ABCC8 p.Arg1182Gln ABCC8 p.Cys1174Phe ABCC8 p.Cys1174Phe ABCC8 p.Glu1506Asp ABCC8 p.Glu1506Asp ABCC8 p.Ser1185Ala ABCC8 p.Ser1185Ala ABCC8 p.Glu1506Gln ABCC8 p.Glu1506Gln to the current regulatory model, both E1506 substitutions have reduced affinity for MgADP (Figure 4), consistent with electrophysiological data demonstrating that SUR1E1506D/Kir6.2 and 10 -1 10 0 10 1 10 2 10 3 10 4 10 5 0.0 0.2 0.4 0.6 0.8 1.0 E1506Q Q1178R E1506D R1182Q I1424V WT S1185A C1174F E1506K G1479R Specific Bound GBC [MgATP] (&#b5;M) 10 -1 10 0 10 1 10 2 10 3 10 4 10 5 0.0 0.2 0.4 0.6 0.8 1.0 E1506Q E1506K Q1178R I1424V E1506D R1182Q WT S1185A C1174F G1479R Specific Bound GBC [ATP 4- ] (&#b5;M) B A FIGURE 3 | Comparison of nucleotide-induced conformational switching in WT and SUR1 mutants. Login to comment 126 ABCC8 p.Glu1506Gln The neutral E1506Q substitution leads to a similar reduction in MgADP affinity (8). Login to comment 128 ABCC8 p.Ile1424Val ABCC8 p.Gln1178Arg ABCC8 p.Arg1182Gln ABCC8 p.Cys1174Phe ABCC8 p.Ser1185Ala To support this hypothesis we analyzed additional mutations including I1424V (ND) and G1479R (CHI) in NBD2 and a cluster of disease causing mutations in TMD2: C1174F (CHI), S1185A (CHI), Q1178R (ND), and R1182Q (ND). Login to comment 151 ABCC8 p.Glu1506Lys ABCC8 p.Ile1424Val ABCC8 p.Gln1178Arg ABCC8 p.Arg1182Gln ABCC8 p.Cys1174Phe ABCC8 p.Glu1506Asp ABCC8 p.Ser1185Ala ABCC8 p.Glu1506Gln Figure 5 shows that diazoxide potentiates the 1 10 100 1000 0.0 0.2 0.4 0.6 0.8 1.0 Q1178R I1424V R1182Q S1185A C1174F WT E1506Q E1506D G1479R E1506K Specific Bound GBC [MgADP] (&#b5;M) FIGURE 4 | MgADP-induced conformational switching in WT and SUR1 mutants. Login to comment 152 ABCC8 p.Cys1174Phe ABCC8 p.Ser1185Ala 10 100 1 0.0 0.2 0.4 0.6 0.8 1.0 1 10 100 0.0 0.2 0.4 0.6 0.8 1.0 WT S1185A C1174F G1479R Specific Bound GBC [Diazoxide] (&#b5;M) Specific Bound GBC [Diazoxide] (&#b5;'c;) FIGURE 5 | Diazoxide potentiates conformational switching in WT and CHI SUR1 mutants. Login to comment 157 ABCC8 p.Glu1506Lys Patients with the G1479R and E1506K substitutions, as dominant mutations, were responsive to diazoxide (26-29). Login to comment 170 ABCC8 p.Glu1506Asp ABCC8 p.Glu1506Gln It is notable that the E1506D, and particularly the E1506Q, substitutions with higher affinities for ATP are not switched appropriately by endogenously generated ATP. Login to comment