Properties of cloned ATP-sensitive K+ currents expressed in Xenopus oocytes. by Gribble, F, Ashfield, R, Ammälä, C, Ashcroft, F

“…We have studied the electrophysiological properties of cloned ATP-sensitive K+ channels (KATP channels) heterologously expressed in Xenopus oocytes. This channel comprises a sulphonylurea receptor subunit (SUR) and an inwardly rectifying K+ channel subunit (Kir). 2. …”

Expression of the cloned beta-cell ATP-sensitive potassium channel in Xenopus oocytes by Gribble, F, Ashfield, R, Ashcroft, F

The interaction of nucleotides with the tolbutamide block of cloned ATP-sensitive K+ channel currents expressed in Xenopus oocytes: a reinterpretation. by Gribble, F, Tucker, S, Ashcroft, F

“…We have examined the mechanism by which nucleotides modulate the tolbutamide block of the beta-cell ATP-sensitive K+ channel (KATP channel), using wild-type and mutant KATP channels heterologously expressed in Xenopus oocytes. This channel is composed of sulphonylurea receptor (SUR1) and pore-forming (Kir6.2) subunits. 2. …”

MgADP hydrolysis is required for MgADP activation of the cloned beta-cell K-ATP channel expressed in Xenopus oocytes by Gribble, F, Tucker, S, Ashcroft, F

Cloning and functional expression of the cDNA encoding an inwardly-rectifying potassium channel expressed in pancreatic beta-cells and in the brain. by Bond, C, Ammälä, C, Ashfield, R, Blair, T, Gribble, F, Khan, R, Lee, K, Proks, P, Rowe, I, Sakura, H

“…Heterologous expression in Xenopus oocytes produced currents which were K(+)-selective, time-independent and showed inward rectification. …”

Heteromeric channel formation and Ca(2+)-free media reduce the toxic effect of the weaver Kir 3.2 allele. by Tucker, S, Pessia, M, Moorhouse, A, Gribble, F, Ashcroft, F, Maylie, J, Adelman, J

“…Recent genetic studies of weaver mice have identified a mutation resulting in an amino acid substitution (G156S) in the pore of the inwardly rectifying potassium channel subunit Kir 3.2. When expressed in Xenopus oocytes the weaver mutation alters channel selectivity from a potassium-selective to a nonspecific cation-selective pore. …”

A novel method for measurement of submembrane ATP concentration. by Gribble, F, Loussouarn, G, Tucker, S, Zhao, C, Nichols, C, Ashcroft, F

“…We show here that mutant ATP-sensitive K(+) channels can be used to measure [ATP](sm) by comparing the increase in current amplitude on patch excision with the ATP dose-response curve. In Xenopus oocytes, [ATP](sm) was 4.6 +/- 0.3 mm (n = 29) under resting conditions, slightly higher than that measured for the bulk cytoplasm (2.3 mm). …”

The antimalarial agent mefloquine inhibits ATP-sensitive K-channels. by Gribble, F, Davis, T, Higham, C, Clark, A, Ashcroft, F

“…Macroscopic K(ATP) currents were studied in inside-out patches excised from Xenopus oocytes expressing cloned K(ATP) channels. …”

In vitro mechanism of action on insulin release of S-22068, a new putative antidiabetic compound. by Le Brigand, L, Virsolvy, A, Manechez, D, Godfroid, J, Guardiola-Lemaître, B, Gribble, F, Ashcroft, F, Bataille, D

“…Similarly to other imidazolines, S-22068 induced a closure of cloned K(ATP) channels injected to Xenopus oocytes by interacting with the pore-forming Kir6.2 moiety. 5. …”

Identification of the high-affinity tolbutamide site on the SUR1 subunit of the K(ATP) channel. by Ashfield, R, Gribble, F, Ashcroft, S, Ashcroft, F

“…Chimeric SURs were coexpressed with Kir6.2 in Xenopus oocytes, and macroscopic currents were measured in inside-out membrane patches. …”

Nucleotide modulation of pinacidil stimulation of the cloned K(ATP) channel Kir6.2/SUR2A. by Gribble, F, Reimann, F, Ashfield, R, Ashcroft, F

“…To determine the reason for this anomaly, we examined the functional interactions between pinacidil (or P1075) and nucleotides by expressing cloned Kir6. 2/SUR2A channels in Xenopus laevis oocytes. Both pinacidil and P1075 activated macroscopic Kir6.2/SUR2A currents in the absence of added nucleotide, but the presence of intracellular ATP or ADP slowed the off-rate of the response. …”

Mechanism of cloned ATP-sensitive potassium channel activation by oleoyl-CoA. by Gribble, F, Proks, P, Corkey, B, Ashcroft, F

“…We recorded macroscopic and single-channel currents from Xenopus oocytes expressing either Kir6.2/SUR1 or Kir6. 2DeltaC36 (which forms channels in the absence of SUR1). …”

Relapsing diabetes can result from moderately activating mutations in KCNJ11. by Gloyn, A, Reimann, F, Girard, C, Edghill, E, Proks, P, Pearson, E, Temple, I, Mackay, D, Shield, J, Freedenberg, D, Noyes, K, Ellard, S, Ashcroft, F, Gribble, F, Hattersley, A

“…Functional characterization of the TNDM associated mutations was performed by expressing the mutated Kir6.2 with SUR1 in Xenopus laevis oocytes. All three heterozygous mutations resulted in a reduction in the sensitivity to ATP when compared with wild-type (IC(50) approximately 30 versus approximately 7 microM, P-value for is all <0.01); however, this was less profoundly reduced than with the PNDM associated mutations. …”

Characterisation of new KATP-channel mutations associated with congenital hyperinsulinism in the Finnish population. by Reimann, F, Huopio, H, Dabrowski, M, Proks, P, Gribble, F, Laakso, M, Otonkoski, T, Ashcroft, F

“…METHODS: Wild type or mutant Kir6.2 and SUR1 subunits were coexpressed in Xenopus oocytes. The functional properties of the channels were examined by measuring currents in intact oocytes or giant inside-out membrane patches. …”

Analysis of the differential modulation of sulphonylurea block of beta-cell and cardiac ATP-sensitive K+ (K(ATP)) channels by Mg-nucleotides. by Reimann, F, Dabrowski, M, Jones, P, Gribble, F, Ashcroft, F

“…We examined the molecular basis of the different response of channels containing SUR1 and SUR2A, by recording currents from inside-out patches excised from Xenopus oocytes heterologously expressing wild-type or chimeric channels. …”

Structural basis for the interference between nicorandil and sulfonylurea action. by Reimann, F, Ashcroft, F, Gribble, F

“…We expressed recombinant K(ATP) channels in Xenopus oocytes and measured the effects of drugs and nucleotides by recording macroscopic currents in excised membrane patches. …”

Differential sensitivity of beta-cell and extrapancreatic K(ATP) channels to gliclazide. by Gribble, F, Ashcroft, F

“…METHODS: Kir6.2 was coexpressed with SUR1, SUR2A or SUR2B in Xenopus oocytes, and channel activity was measured by recording macroscopic currents in giant inside-out membrane patches. …”

Tissue specificity of sulfonylureas: studies on cloned cardiac and beta-cell K(ATP) channels. by Gribble, F, Tucker, S, Seino, S, Ashcroft, F

“…We examined the mechanism underlying the tissue specificity of the sulfonylureas tolbutamide and glibenclamide, and the benzamido-derivative meglitinide, using cloned beta-cell (Kir6.2/SUR1) and cardiac (Kir6.2/SUR2A) K(ATP) channels expressed in Xenopus oocytes. Tolbutamide inhibited Kir6.2/SUR1 (Ki approximately 5 micromol/l), but not Kir6.2/SUR2A, currents with high affinity. …”

Involvement of the N-terminus of Kir6.2 in the inhibition of the KATP channel by ATP. by Proks, P, Gribble, F, Adhikari, R, Tucker, S, Ashcroft, F

“…We examined the effect on the channel ATP sensitivity of mutating the arginine residue at position 50 (R50) in the N-terminus of Kir6.2, by recording macroscopic currents in membrane patches excised from Xenopus oocytes expressing wild-type or mutant Kir6.2DeltaC26. 3. …”

Differential response of K(ATP) channels containing SUR2A or SUR2B subunits to nucleotides and pinacidil. by Reimann, F, Gribble, F, Ashcroft, F

“…We explored the basis for this difference by expressing Kir6.2/SUR2A and Kir6.2/SUR2B currents in Xenopus laevis oocytes. Kir6.2/SUR2B but not Kir6.2/SUR2A currents were activated by the Mg-nucleoside triphosphates MgATP and MgGTP, whereas both channel types responded to the diphosphates MgADP and MgGDP. …”