Insulin is a peptide hormone secreted from pancreatic beta cells to regulate blood glucose homeostasis. Maturation of active insulin occurs within insulin secretory granules (ISG) by acidification of the lumen and enzymatic cleavage of insulin before secretion. This process is dysregulated in diabetes, and many questions remain on how the cell controls insulin maturation. We address this gap in knowledge by designing two genetically encoded fluorescence pH sensors and a fluorescence lifetime imaging and analysis pipeline to monitor the pH of individual secretory ISGs within live cells at higher resolution and precision than previously possible. We observed different subpopulations of ISGs based on their pH and subcellular localization. Signals regulating metabolism vs membrane depolarization mobilize different subpopulations of ISGs for secretion, and we confirm that maturation signals acidify ISGs. We conclude that different signaling networks uniquely impact ISG mobilization and secretion. Future applications of these tools will be useful for exploring how these processes are dysregulated in diabetes and provide new paths for developing more effective treatments.

中文翻译：

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使用基因编码的 pH 传感器解码胰岛素分泌颗粒成熟


胰岛素是胰腺 β 细胞分泌的一种肽激素，用于调节血糖稳态。活性胰岛素的成熟发生在胰岛素分泌颗粒 （ISG） 内，通过肠腔的酸化和胰岛素的酶促裂解在分泌前发生。这个过程在糖尿病中失调，关于细胞如何控制胰岛素成熟仍然存在许多问题。我们通过设计两个基因编码的荧光 pH 传感器和一个荧光寿命成像和分析管道来解决这一知识空白，以比以前更高的分辨率和精度监测活细胞内单个分泌型 ISG 的 pH 值。我们根据 ISGs 的 pH 值和亚细胞定位观察了不同的 ISGs 亚群。调节代谢与膜去极化的信号动员 ISG 的不同亚群进行分泌，我们证实成熟信号使 ISG 酸化。我们得出结论，不同的信号转导网络独特地影响 ISG 动员和分泌。这些工具的未来应用将有助于探索糖尿病中这些过程如何失调，并为开发更有效的治疗方法提供新的途径。