Differential interactions of nateglinide and repaglinide on the human beta-cell sulphonylurea receptor 1.
Repaglinide and nateglinide represent a new class of insulin secretagogues, structurally unrelated to sulphonylureas, that were developed for the treatment of type 2 diabetes. The inhibitory effect of these drugs was investigated on recombinant wild-type and mutant Kir6.2/SUR1 channels expressed in HEK293 cells. Nateglinide and repaglinide dose-dependently inhibited whole-cell Kir6.2/SUR1 currents with half-maximal inhibitory concentration (IC(50)) values of 800 and 21 nmol/l, respectively. Mutation of serine 1237 in SUR1 to tyrosine (S1237Y) abolished tolbutamide and nateglinide block, suggesting that these drugs share a common point of interaction on the SUR1 subunit of the ATP-sensitive K(+) channel. In contrast, repaglinide inhibition was unaffected by the S1237Y mutation (IC(50) = 23 nmol/l). Radioligand binding studies revealed a single high-affinity binding site for [(3)H]repaglinide on membranes prepared from HEK293 cells expressing wild-type (equilibrium dissociation constant [K(D)] = 0.40 nmol/l) or mutant (K(D) = 0.31 nmol/l) Kir6.2/SUR1 channels. Nateglinide and tolbutamide displaced [(3)H]repaglinide binding to wild-type channels with IC(50) values of 0.7 and 26 micro mol/l, respectively, but produced <10% displacement of [(3)H]repaglinide bound to mutant channels. This is consistent with the idea that binding of nateglinide and tolbutamide, but not repaglinide, is abolished by the SUR1[S1237Y] mutation and that the binding site for repaglinide is not identical to that of nateglinde/tolbutamide. These results are discussed in terms of a conformational analysis of the drug molecules.
Hansen
Ann Maria K
AM
Discovery, Novo Nordisk A/S, Bagsvaerd, Denmark. University Laboratory of Physiology, Oxford University, Oxford, U.K.
Christensen
Inge T
IT
Hansen
John Bondo
JB
Carr
Richard D
RD
Ashcroft
Frances M
FM
Wahl
Philip
P
D018528:ATP-Binding Cassette Transporters; D001667:Binding, Competitive; D002219:Carbamates / Q000737:chemistry / Q000494:pharmacology*; D002460:Cell Line; D003510:Cyclohexanes / Q000737:chemistry / Q000494:pharmacology*; D004347:Drug Interactions; D004594:Electrophysiology; D006801:Humans; D007515:Islets of Langerhans / Q000378:metabolism*; D000077715:Nateglinide; D010649:Phenylalanine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology*; D010880:Piperidines / Q000737:chemistry / Q000494:pharmacology*; D015221:Potassium Channels / Q000187:drug effects* / Q000502:physiology; D024661:Potassium Channels, Inwardly Rectifying / Q000187:drug effects* / Q000502:physiology; D011955:Receptors, Drug / Q000187:drug effects*; D064233:Sulfonylurea Receptors; D014044:Tolbutamide / Q000378:metabolism
C577507:ABCC8 protein, human; D018528:ATP-Binding Cassette Transporters; D002219:Carbamates; D003510:Cyclohexanes; D010880:Piperidines; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D011955:Receptors, Drug; D064233:Sulfonylurea Receptors; D000077715:Nateglinide; D010649:Phenylalanine; C072379:repaglinide; D014044:Tolbutamide