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Kir6.2 activation by sulfonylurea receptors: a different mechanism of action for SUR1 and SUR2A subunits via the same residues.
Principalli MA
,
Dupuis JP
,
Moreau CJ
,
Vivaudou M
,
Revilloud J
.
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ATP-sensitive potassium channels (K-ATP channels) play a key role in adjusting the membrane potential to the metabolic state of cells. They result from the unique combination of two proteins: the sulfonylurea receptor (SUR), an ATP-binding cassette (ABC) protein, and the inward rectifier K(+) channel Kir6.2. Both subunits associate to form a heterooctamer (4 SUR/4 Kir6.2). SUR modulates channel gating in response to the binding of nucleotides or drugs and Kir6.2 conducts potassium ions. The activity of K-ATP channels varies with their localization. In pancreatic β-cells, SUR1/Kir6.2 channels are partly active at rest while in cardiomyocytesSUR2A/Kir6.2 channels are mostly closed. This divergence of function could be related to differences in the interaction of SUR1 and SUR2A with Kir6.2. Three residues (E1305, I1310, L1313) located in the linker region between transmembrane domain 2 and nucleotide-binding domain 2 of SUR2A were previously found to be involved in the activation pathway linking binding of openers onto SUR2A and channel opening. To determine the role of the equivalent residues in the SUR1 isoform, we designed chimeras between SUR1 and the ABC transporter multidrug resistance-associated protein 1 (MRP1), and used patch clamp recordings on Xenopus oocytes to assess the functionality of SUR1/MRP1 chimeric K-ATP channels. Our results reveal that the same residues in SUR1 and SUR2A are involved in the functional association with Kir6.2, but they display unexpected side-chain specificities which could account for the contrasted properties of pancreatic and cardiac K-ATP channels.
Figure 1. SUR1 residues Q1342, I1347, and L1350 are essential for K-ATP channel activation by Diazoxide. (A) putative membrane topology of SUR1 (NBD, nucleotide-binding domain; WA, Walker A motif; WB, Walker B motif). The star indicates the region identified by Rainbow et al. (2004) and mutated to obtain the S1M chimera. (B) alignment of the amino acid sequences of human SUR1, rat SUR2A, and human MRP1. Three residues (boxed) are homologous in SURs and not in MRP1: Q1342, I1347, and L1350. Stars and squares indicate the MRP1 residues introduced in SUR1 to obtain SUR1S3M and SUR1S4M, respectively. (C) schematic representation of the chimeras. SUR1 and MRP1 elements are drawn in gray and black, respectively. For clarity, residues Q1342, I1347, and L1350 of SUR1 are indicated by white stripes. The amino acid composition of the constructs were as follows: SUR1S1M = SUR1(M1-V1313) + MRP1(V1261-F1341) + SUR1(R1394-K1582); SUR1S2M = SUR1(M1-P1336) + MRP1(P1284-L1300) + SUR1(V1352-K1582); SUR1S3M = SUR1 with mutations N1338S, I1345V, S1351C, and V1352L; SUR1S4M = SUR1 with mutations K1337S, D1341Q, K1344R, Q1346E, and Q1348R; SUR1(QIL/VFY) = SUR1 with mutations Q1342V, I1347F, and L1350Y, SUR1S2M(VFY/QIL) = SUR1S2M with mutations V1290Q, F1295I, and Y1298L. (D) Diazoxide responses were measured in inside-out patches excised from oocytes coexpressing Kir6.2 and wild type or chimeric SURs or MRP1 as indicated. Diazoxide (300 μmol/L) was applied in the presence of 100 μmol/L ATP, and currents were normalized to the current measured in the absence of nucleotides immediately before opener application. Application of 100 μmol/L ATP alone (black bars) was used as a control. Numbers at right of bars indicate the number of patches included in each average. (E) Representative patch-clamp recordings illustrating the responses of wild type and SUR1(QIL/VFY) channels to 300 μmol/L Diazoxide in the presence of 100 μmol/L ATP. SUR1, sulfonylurea receptor 1; MRP, multidrug-resistance associated protein.
Figure 2. Characterization of the SUR1(QIL/VFY) mutant. (A) Diazoxide doseâresponse relationships for Kir6.2/SUR1 (circles) and Kir6.2/SUR1(QIL/VFY) (triangles). Currents were normalized to the current measured in 0 ATP. Hill equation fitting yielded K1/2 = 132 μmol/L (h = 1.65) for Kir6.2/SUR1. (B) Response to 100 μmol/L MgADP of SUR1 wt and SUR1(QIL/VFY). Currents were normalized to the current measured in the absence of nucleotides immediately before MgADP application. Numbers indicate the number of patches included in each average. (C) Representative patch-clamp recordings illustrating the responses of wild type and SUR1(QIL/VFY) channels to 100 μmol/L MgADP in the absence of ATP. (D) Current amplitudes in the absence of nucleotides of Kir6.2/SUR1, Kir6.2/SUR1(QIL/VFY), Kir6.2/SUR2A, and Kir6.2/SUR2A(EIL/VFY). (E) ATP doseâresponse relationships for Kir6.2/SUR1 (circles) and Kir6.2/SUR1(QIL/VFY) (triangles). Currents were normalized to the current measured in 0 ATP. Hill equation fitting yielded K1/2 = 20 μmol/L (h = 1.33) for Kir6.2/SUR1 and K1/2 = 17 μmol/L (h = 1.32) for Kir6.2/SUR1(QIL/VFY). SUR1, sulfonylurea receptor 1.
Figure 3. Openers response by sulfonylurea receptor 1 (SUR1) and SUR2A wt and relative mutants. Residues Q1342, I1347, and L1350 of SUR1, and the matching residues E1305, I1310, and L1313 of SUR2A were mutated into alanine, glycine, and isoleucine. (A) The effects of the application of 100 μmol/L MgADP were measured in inside-out patches excised from oocytes coexpressing Kir6.2 and the indicated SUR constructs. Currents were normalized to the current measured in the absence of nucleotides immediately before MgADP application. Numbers at right of bars indicate the number of patches included in each average. (B) The effects of 300 μmol/L Diazoxide or 10 μmol/L P1075 were measured in inside-out patches excised from oocytes. Diazoxide (300 μmol/L) was applied in the presence of 100 μmol/L ATP. P1075 (10 μmol/L) was applied in the presence of 100 μmol/L ATP. Control designates the current measured in 100 μmol/L ATP before application of the tested opener.
Figure 4. Sulfonylurea receptor 1 (SUR1) homology model based on multidrug resistance protein 1 (Bessadok et al. 2011). (A) Lateral view. The region identified by Rainbow et al. (2004) is highlighted in dark blue (SUR1S1M fragment). Residues Q1342, I1347, and L1350 are represented in ball-and-stick format and colored in red. (B) Close-up lateral view of the cytoplasmic domain. (C) axial view from the extracellular side.
Aguilar-Bryan,
Cloning of the beta cell high-affinity sulfonylurea receptor: a regulator of insulin secretion.
1995, Pubmed
Aguilar-Bryan,
Cloning of the beta cell high-affinity sulfonylurea receptor: a regulator of insulin secretion.
1995,
Pubmed
Ashcroft,
Properties of single potassium channels modulated by glucose in rat pancreatic beta-cells.
1988,
Pubmed
Bessadok,
Recognition of sulfonylurea receptor (ABCC8/9) ligands by the multidrug resistance transporter P-glycoprotein (ABCB1): functional similarities based on common structural features between two multispecific ABC proteins.
2011,
Pubmed
Cartier,
Defective trafficking and function of KATP channels caused by a sulfonylurea receptor 1 mutation associated with persistent hyperinsulinemic hypoglycemia of infancy.
2001,
Pubmed
Chan,
N-terminal transmembrane domain of the SUR controls trafficking and gating of Kir6 channel subunits.
2003,
Pubmed
,
Xenbase
Clement,
Association and stoichiometry of K(ATP) channel subunits.
1997,
Pubmed
de Wet,
The ATPase activities of sulfonylurea receptor 2A and sulfonylurea receptor 2B are influenced by the C-terminal 42 amino acids.
2010,
Pubmed
D'hahan,
Pharmacological plasticity of cardiac ATP-sensitive potassium channels toward diazoxide revealed by ADP.
1999,
Pubmed
,
Xenbase
Dupuis,
Three C-terminal residues from the sulphonylurea receptor contribute to the functional coupling between the K(ATP) channel subunits SUR2A and Kir6.2.
2008,
Pubmed
,
Xenbase
Fang,
The N-terminal transmembrane domain (TMD0) and a cytosolic linker (L0) of sulphonylurea receptor define the unique intrinsic gating of KATP channels.
2006,
Pubmed
,
Xenbase
Gribble,
Differential sensitivity of beta-cell and extrapancreatic K(ATP) channels to gliclazide.
1999,
Pubmed
,
Xenbase
Gribble,
The essential role of the Walker A motifs of SUR1 in K-ATP channel activation by Mg-ADP and diazoxide.
1997,
Pubmed
,
Xenbase
Hosy,
The unusual stoichiometry of ADP activation of the KATP channel.
2014,
Pubmed
,
Xenbase
Inagaki,
Cloning and functional characterization of a novel ATP-sensitive potassium channel ubiquitously expressed in rat tissues, including pancreatic islets, pituitary, skeletal muscle, and heart.
1995,
Pubmed
,
Xenbase
Inagaki,
Reconstitution of IKATP: an inward rectifier subunit plus the sulfonylurea receptor.
1995,
Pubmed
Kane,
Cardiac KATP channels in health and disease.
2005,
Pubmed
Liman,
Subunit stoichiometry of a mammalian K+ channel determined by construction of multimeric cDNAs.
1992,
Pubmed
,
Xenbase
Lodwick,
Sulfonylurea receptors regulate the channel pore in ATP-sensitive potassium channels via an intersubunit salt bridge.
2014,
Pubmed
Mikhailov,
3-D structural and functional characterization of the purified KATP channel complex Kir6.2-SUR1.
2005,
Pubmed
Moreau,
The size of a single residue of the sulfonylurea receptor dictates the effectiveness of K ATP channel openers.
2005,
Pubmed
Moreau,
SUR, ABC proteins targeted by KATP channel openers.
2005,
Pubmed
Moreau,
The molecular basis of the specificity of action of K(ATP) channel openers.
2000,
Pubmed
Nichols,
Adenosine diphosphate as an intracellular regulator of insulin secretion.
1996,
Pubmed
Noma,
ATP-regulated K+ channels in cardiac muscle.
,
Pubmed
Rainbow,
Proximal C-terminal domain of sulphonylurea receptor 2A interacts with pore-forming Kir6 subunits in KATP channels.
2004,
Pubmed
Schwanstecher,
Potassium channel openers require ATP to bind to and act through sulfonylurea receptors.
1998,
Pubmed
Seino,
Physiological and pathophysiological roles of ATP-sensitive K+ channels.
2003,
Pubmed
Vivaudou,
Modification by protons of frog skeletal muscle KATP channels: effects on ion conduction and nucleotide inhibition.
1995,
Pubmed
Yan,
Congenital hyperinsulinism associated ABCC8 mutations that cause defective trafficking of ATP-sensitive K+ channels: identification and rescue.
2007,
Pubmed
Zerangue,
A new ER trafficking signal regulates the subunit stoichiometry of plasma membrane K(ATP) channels.
1999,
Pubmed
,
Xenbase
