Guiot Y, Stevens M, Marhfour I, Stiernet P, Mikhailov M, Ashcroft S J H, Rahier J, Henquin J-C, Sempoux C
Department of Pathology, Faculty of Medicine, University of Louvain, B-1200, Brussels, Belgium.
Endocrinology Unit and Metabolism, Faculty of Medicine, University of Louvain, UCL5530, Brussels, Belgium.
Diabetologia. 2007 Sep;50(9):1889-1899. doi: 10.1007/s00125-007-0731-z. Epub 2007 Jun 26.
AIMS/HYPOTHESIS: Sulfonylurea receptor 1 (SUR1) is the regulatory subunit of ATP-sensitive K channels in beta cells. Morphological methods (immunohistochemistry and sulfonylurea binding) were used to establish the cellular and subcellular location of SUR1 in human and rodent islets.
In the human, mouse and rat pancreas, all endocrine cells of the islets were immunolabelled with an anti-SUR1 antibody, whereas tissues containing SUR2 were consistently negative, as were those from Sur1 (also known as Abcc8)(-/-) mice. In beta cells of the three species, the plasma membrane was distinctly stained, but SUR1 was mainly present over the cytoplasm, with an intensity that varied between cells. Electron microscopy showed that SUR1 was immunolocalised in insulin, glucagon and somatostatin granules. In rat beta cells degranulated by in vivo treatment with glibenclamide (known as glyburide in the USA and Canada), the insulin and SUR1 staining intensity was similarly decreased by approximately 45%, whereas SUR1 staining was not changed in non-beta cells. In all islet cells, binding of glibenclamide labelled with fluorescent dipyrromethane boron difluoride (BODIPY-FL) was punctate over the cytoplasm, compatible with the labelling of endocrine granules. A faint labelling persisted in Sur1 (-/-) mice, but it was not different from that obtained with BODIPY-FL alone used as negative control.
CONCLUSIONS/INTERPRETATION: Our study immunolocalised SUR1 in alpha, beta and delta cells of human, mouse and rat islets, and for the first time visualised it in the plasma membrane. We also show that SUR1 is abundant in endocrine granules, where its function remains to be established. No specific sulfonylurea-binding sites other than SUR1 are identified in islet cells by the glibenclamide-BODIPY-FL technique.
目的/假设：磺脲类受体1（SUR1）是β细胞中ATP敏感性钾通道的调节亚基。采用形态学方法（免疫组织化学和磺脲类结合）确定SUR1在人和啮齿动物胰岛中的细胞及亚细胞定位。
在人、小鼠和大鼠胰腺中，胰岛的所有内分泌细胞均用抗SUR1抗体进行免疫标记，而含有SUR2的组织始终呈阴性，Sur1（也称为Abcc8）基因敲除小鼠的组织也是如此。在这三个物种的β细胞中，质膜有明显染色，但SUR1主要存在于细胞质中，其强度在细胞间有所不同。电子显微镜显示，SUR1免疫定位于胰岛素、胰高血糖素和生长抑素颗粒中。在用格列本脲（在美国和加拿大称为优降糖）进行体内处理后脱颗粒的大鼠β细胞中，胰岛素和SUR1染色强度同样降低了约45%，而非β细胞中的SUR1染色没有变化。在所有胰岛细胞中，用荧光二吡咯甲烷二氟化硼（BODIPY-FL）标记的格列本脲在细胞质中的结合呈点状，与内分泌颗粒的标记相符。在Sur1基因敲除小鼠中仍有微弱标记，但与单独用作阴性对照的BODIPY-FL所获得的标记无差异。
结论/解读：我们的研究将SUR1免疫定位在人、小鼠和大鼠胰岛的α、β和δ细胞中，并首次在质膜中观察到它。我们还表明，SUR1在内分泌颗粒中含量丰富，其功能尚待确定。通过格列本脲-BODIPY-FL技术，在胰岛细胞中未发现除SUR1以外的特异性磺脲类结合位点。
