Department of Chemistry, Bridge Institute, USC Michelson Center for Convergent Bioscience, University of Southern California, Los Angeles, California 90089, United States.
Department of Biological Sciences, Bridge Institute, USC Michelson Center for Convergent Bioscience, Translational Imaging Center, University of Southern California, 1002 Childs Way, Los Angeles, California 90089, United States.
ACS Sens. 2024 Nov 22;9(11):6032-6039. doi: 10.1021/acssensors.4c01885. Epub 2024 Nov 6.
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.
胰岛素是一种由胰岛β细胞分泌的肽类激素，用于调节血糖稳态。在分泌前，通过腔内酸化和胰岛素酶切，胰岛素在胰岛素分泌颗粒（ISG）内成熟为有活性的形式。这一过程在糖尿病中失调，关于细胞如何控制胰岛素成熟，仍有许多问题尚未解决。我们通过设计两种遗传编码的荧光 pH 传感器和荧光寿命成像和分析流水线，来监测活细胞中单个分泌 ISG 的 pH 值，从而在更高的分辨率和精度上填补了这一知识空白。我们根据 pH 值和亚细胞定位观察到 ISG 的不同亚群。调节代谢与膜去极化的信号动员不同的 ISG 亚群进行分泌，并且我们证实成熟信号会使 ISG 酸化。我们得出结论，不同的信号网络会对 ISG 的动员和分泌产生独特的影响。这些工具的未来应用将有助于探索这些过程在糖尿病中的失调情况，并为开发更有效的治疗方法提供新途径。
