Institute of Molecular Biology and Biochemistry, Center of Physiological Medicine, Medical University of Graz, 8010 Graz, Austria Institute of Physiological Chemistry, Center of Physiological Medicine, Medical University of Graz, 8010 Graz, Austria Precursory Research for Embryonic Science, Japan Science and Technology Agency, Tokyo 102-0075, Japan.
Mol Biol Cell. 2014 Feb;25(3):368-79. doi: 10.1091/mbc.E13-07-0433. Epub 2013 Dec 4.
Multiple functions of the endoplasmic reticulum (ER) essentially depend on ATP within this organelle. However, little is known about ER ATP dynamics and the regulation of ER ATP import. Here we describe real-time recordings of ER ATP fluxes in single cells using an ER-targeted, genetically encoded ATP sensor. In vitro experiments prove that the ATP sensor is both Ca(2+) and redox insensitive, which makes it possible to monitor Ca(2+)-coupled ER ATP dynamics specifically. The approach uncovers a cell type-specific regulation of ER ATP homeostasis in different cell types. Moreover, we show that intracellular Ca(2+) release is coupled to an increase of ATP within the ER. The Ca(2+)-coupled ER ATP increase is independent of the mode of Ca(2+) mobilization and controlled by the rate of ATP biosynthesis. Furthermore, the energy stress sensor, AMP-activated protein kinase, is essential for the ATP increase that occurs in response to Ca(2+) depletion of the organelle. Our data highlight a novel Ca(2+)-controlled process that supplies the ER with additional energy upon cell stimulation.
内质网（ER）的多种功能本质上依赖于该细胞器内的 ATP。然而，关于 ER ATP 动力学和 ER ATP 摄取的调节知之甚少。在这里，我们使用靶向 ER 的基因编码 ATP 传感器，对单个细胞中的 ER ATP 通量进行实时记录。体外实验证明，ATP 传感器既不受 Ca(2+)也不受氧化还原影响，这使得可以专门监测 Ca(2+)-偶联的 ER ATP 动力学。该方法揭示了不同细胞类型中 ER ATP 动态平衡的细胞类型特异性调节。此外，我们表明细胞内 Ca(2+)释放与 ER 内 ATP 的增加相关。Ca(2+)-偶联的 ER ATP 增加与 Ca(2+)动员的方式无关，而是由 ATP 生物合成的速率控制。此外，能量应激传感器 AMP 激活蛋白激酶对于细胞器 Ca(2+)耗竭时发生的 ATP 增加是必需的。我们的数据突出了一种新的 Ca(2+)-控制过程，该过程在细胞刺激时为 ER 提供额外的能量。
