The endoplasmic reticulum (ER) acts as the major storage site for calcium ions, which are messenger ions for intracellular signaling. Disruption of calcium ion homeostasis can significantly affect the viscosity, polarity and pH of the ER. However, it is still unclear the relationship between the viscosity changes in ER and the imbalance of calcium ion homeostasis. Herein, we developed a novel fluorescent probe, named TPA, for monitoring viscosity changes that specifically targets the endoplasmic reticulum rather than mitochondria or lysosomes. TPA probe displayed good stability, as well as high responsiveness and selectivity to viscosity. The fluorescence intensity of TPA was significantly enhanced with the increased concentration or incubation time of the stimulating agents(i.e., tunicamycin), showing high responsiveness to the viscosity changes in ER. Furthermore, the TPA probe successfully demonstrated that an increase in intracellular calcium ion concentration leads to an increase in ER viscosity, whereas a decrease in calcium ion concentration leads to a decrease viscosity in ER. Both and experiments demonstrated that TPA probe successfully detected the viscosity changes in ER, especially the effects of calcium ion homeostasis disruption on ER. Overall, the TPA probe represents an efficient method for studying the relationship between calcium ion homeostasis and ER viscosity.

中文翻译：

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内质网靶向荧光探针实时监测钙稳态破坏引起的粘度变化


内质网 (ER) 是钙离子的主要储存位点，钙离子是细胞内信号传导的信使离子。钙离子稳态的破坏会显着影响 ER 的粘度、极性和 pH 值。然而，内质网粘度变化与钙离子稳态失衡之间的关系尚不清楚。在此，我们开发了一种新型荧光探针，名为 TPA，用于监测粘度变化，该探针专门针对内质网而不是线粒体或溶酶体。 TPA 探针表现出良好的稳定性以及对粘度的高响应性和选择性。 TPA 的荧光强度随着刺激剂（即衣霉素）浓度或孵育时间的增加而显着增强，显示出对 ER 粘度变化的高响应性。此外，TPA 探针成功证明细胞内钙离子浓度的增加会导致 ER 粘度的增加，而钙离子浓度的降低会导致 ER 粘度的降低。实验均表明，TPA 探针成功检测了 ER 的粘度变化，特别是钙离子稳态破坏对 ER 的影响。总体而言，TPA 探针代表了研究钙离子稳态和 ER 粘度之间关系的有效方法。