Department of Endocrinology, Zhongnan Hospital of Wuhan University, Wuhan, Hubei 430071, P.R. China.
Department of Endocrinology, Xianning Central Hospital, Xianning, Hubei 437100, P.R. China.
Mol Med Rep. 2022 May;25(5). doi: 10.3892/mmr.2022.12686. Epub 2022 Mar 18.
Sigma‑1 receptor (Sig‑1R) is a class of orphan receptors, the potential role of which in pancreatic islet cells remains poorly understood. The present study aimed to investigate the role of Sig‑1R in islet β‑cell proliferation and examine the effects of Sig‑1R on islet β‑cell injury under lipotoxic conditions. Sig‑1R‑overexpressing MIN6 cells were generated by lentiviral vector transfection. The effect of Sig‑1R overexpression on cell proliferation detected by EdU staining, cell cycle progression by propidium iodide (PI), apoptosis by Annexin V‑APC/PI, mitochondrial membrane potential by Mitolite Red and cytoplasmic Ca levelsby Fura‑2/AM in islet β‑cells were measured by flow cytometry. Western blot analysis was used to measure protein expression levels of endoplasmic reticulum (ER) stress markers glucose‑regulated protein 78 and C/EBP homologous protein, mitochondrial apoptotic proteins Bcl‑2‑associated X and Bcl‑2 and cytochrome . In addition, ATP levels and insulin secretion were separately measured using ATP Assay and mouse insulin ELISA. Mitochondria‑associated ER membrane (MAM) structures in MIN6 cells were then detected using transmission electron microscopy. Protein disulfide isomerase expression and possible colocalization between inositol 1,4,5‑trisphosphate receptor and voltage‑dependent anion channel 1 were examined using immunofluorescence. Sig‑1R overexpression was found to promote β‑cell proliferation by accelerating cell cycle progression. Furthermore, Sig‑1R overexpression ameliorated the apoptosis rate whilst impairing insulin secretion induced by palmitic acid by relieving ER stress and mitochondrial dysfunction in MIN6 cells. Sig‑1R overexpression also promoted Ca transport between mitochondria and ER by increasing the quantity of ER adjacent to mitochondria in the 50‑nm range. It was concluded that Sig‑1R overexpression conferred protective effects on β‑cells against lipotoxicity as a result of the promotion of cell proliferation and inhibition of ER stress and oxidative stress, by regulating the structure of MAM.
Sigma-1 受体（Sig-1R）是一类孤儿受体，其在胰岛细胞中的潜在作用尚不清楚。本研究旨在探讨 Sig-1R 在胰岛β细胞增殖中的作用，并研究 Sig-1R 在脂毒性条件下对胰岛β细胞损伤的影响。通过慢病毒载体转染生成 Sig-1R 过表达 MIN6 细胞。通过 EdU 染色检测 Sig-1R 过表达对细胞增殖的影响，碘化丙啶（PI）检测细胞周期进程，Annexin V-APC/PI 检测细胞凋亡，Mitolite Red 检测线粒体膜电位，Fura-2/AM 检测细胞质 Ca 水平。采用 Western blot 分析测定内质网（ER）应激标志物葡萄糖调节蛋白 78 和 C/EBP 同源蛋白、线粒体凋亡蛋白 Bcl-2 相关 X 和 Bcl-2 以及细胞色素 c 的蛋白表达水平。此外，使用 ATP 测定试剂盒和小鼠胰岛素 ELISA 分别测定 ATP 水平和胰岛素分泌。然后使用透射电子显微镜检测 MIN6 细胞中的线粒体相关内质网膜（MAM）结构。通过免疫荧光法检测蛋白二硫键异构酶表达和肌醇 1,4,5-三磷酸受体与电压依赖性阴离子通道 1 之间的可能共定位。结果发现，Sig-1R 过表达通过加速细胞周期进程促进β细胞增殖。此外，Sig-1R 过表达减轻了 ER 应激和线粒体功能障碍，从而改善了棕榈酸诱导的 MIN6 细胞凋亡率和胰岛素分泌。Sig-1R 过表达还通过增加 50nm 范围内靠近线粒体的 ER 数量促进了线粒体和 ER 之间的 Ca 转运。结论：Sig-1R 过表达通过促进细胞增殖和抑制 ER 应激和氧化应激，调节 MAM 的结构，对胰岛β细胞发挥保护作用，从而减轻脂毒性。
