Hansen Ann Maria K, Christensen Inge T, Hansen John Bondo, Carr Richard D, Ashcroft Frances M, Wahl Philip
Discovery, Novo Nordisk A/S, Bagsvaerd, Denmark. University Laboratory of Physiology, Oxford University, Oxford, U.K.
Diabetes. 2002 Sep;51(9):2789-95. doi: 10.2337/diabetes.51.9.2789.
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.
瑞格列奈和那格列奈代表了一类新型的胰岛素促分泌剂，其结构与磺脲类药物无关，用于治疗2型糖尿病。研究了这些药物对在HEK293细胞中表达的重组野生型和突变型Kir6.2/SUR1通道的抑制作用。那格列奈和瑞格列奈剂量依赖性地抑制全细胞Kir6.2/SUR1电流，其半数最大抑制浓度（IC50）值分别为800和21 nmol/l。SUR1中丝氨酸1237突变为酪氨酸（S1237Y）消除了甲苯磺丁脲和那格列奈的阻断作用，表明这些药物在ATP敏感性钾通道的SUR1亚基上有共同的相互作用点。相比之下，瑞格列奈的抑制作用不受S1237Y突变的影响（IC50 = 23 nmol/l）。放射性配体结合研究显示，在表达野生型（平衡解离常数[KD] = 0.40 nmol/l）或突变型（KD = 0.31 nmol/l）Kir6.2/SUR1通道的HEK293细胞制备的膜上，[(3)H]瑞格列奈有一个单一的高亲和力结合位点。那格列奈和甲苯磺丁脲分别以0.7和26 μmol/l的IC50值取代[(3)H]瑞格列奈与野生型通道的结合，但对与突变型通道结合的[(3)H]瑞格列奈的取代率<10%。这与以下观点一致，即那格列奈和甲苯磺丁脲的结合，但不是瑞格列奈的结合，被SUR1[S1237Y]突变消除，并且瑞格列奈的结合位点与那格列奈/甲苯磺丁脲的结合位点不同。根据药物分子的构象分析对这些结果进行了讨论。
