Department of Physiology and Institute of Lifestyle Medicine, Yonsei University Wonju College of Medicine, Wonju, Republic of Korea.
Mol Cell Endocrinol. 2013 Dec 5;381(1-2):198-209. doi: 10.1016/j.mce.2013.08.003. Epub 2013 Aug 9.
Here, we have investigated the role of inorganic phosphate (Pi) transport in mitochondria of rat clonal β-cells. In α-toxin-permeabilized INS-1E cells, succinate and glycerol-3-phosphate increased mitochondrial ATP release which depends on exogenous ADP and Pi. In the presence of substrates, addition of Pi caused mitochondrial matrix acidification and hyperpolarisation which promoted ATP export. Dissipation of the mitochondrial pH gradient or pharmacological inhibition of Pi transport blocked the effects of Pi on electrochemical gradient and ATP export. Knock-down of the phosphate transporter PiC, however, neither prevented Pi-induced mitochondrial activation nor glucose-induced insulin secretion. Using (31)P NMR we observed reduction of Pi pools during nutrient stimulation of INS-1E cells. Interestingly, Pi loss was less pronounced in mitochondria than in the cytosol. We conclude that matrix alkalinisation is necessary to maintain a mitochondrial Pi pool, at levels sufficient to stimulate energy metabolism in insulin-secreting cells beyond its role as a substrate for ATP synthesis.
在这里，我们研究了无机磷酸盐 (Pi) 转运在大鼠克隆β细胞线粒体中的作用。在α-毒素通透的 INS-1E 细胞中，琥珀酸和甘油-3-磷酸增加了依赖于外源性 ADP 和 Pi 的线粒体 ATP 释放。在存在底物的情况下，添加 Pi 导致线粒体基质酸化和超极化，从而促进 ATP 输出。线粒体 pH 梯度的耗散或 Pi 转运的药理学抑制阻断了 Pi 对电化学梯度和 ATP 输出的影响。然而，磷酸转运蛋白 PiC 的敲低既不能防止 Pi 诱导的线粒体激活，也不能防止葡萄糖诱导的胰岛素分泌。使用 (31)P NMR，我们观察到在 INS-1E 细胞的营养刺激期间 Pi 池减少。有趣的是，Pi 的损失在基质中比在细胞质中不那么明显。我们得出的结论是，基质碱化对于维持线粒体 Pi 池是必要的，使其水平足以刺激胰岛素分泌细胞的能量代谢，超出其作为 ATP 合成底物的作用。
