Takahashi N, Kadowaki T, Yazaki Y, Ellis-Davies G C, Miyashita Y, Kasai H
Third Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.
Proc Natl Acad Sci U S A. 1999 Jan 19;96(2):760-5. doi: 10.1073/pnas.96.2.760.
The role of cytosolic ATP in exocytosis was investigated by using amperometric measurement of insulin exocytosis in pancreatic beta cells, which were stimulated with photolysis of caged Ca2+ compounds. Insulin exocytosis occurred with two rates. We found that ATP hastened and augmented the exocytosis via selective enhancement of the exocytosis with the faster rate. A nonhydrolysable analog of ATP, adenosine 5'-O-(3-thiotriphosphate), which blocks ATPase, was even more effective than ATP, indicating that the phosphorylation event occurred downstream of ATP-dependent vesicle transportation and priming. The action of ATP was eliminated by a competitive antagonist of cAMP, and by an inhibitor of adenylate cyclase. These data characterize an ATP sensing mechanism for the Ca2+-dependent exocytosis involving adenylate-cyclase, cAMP-dependent protein kinase, and, possibly, the fusion machinery itself. Thus, the fast exocytotic machinery requires both phosphorylation and Ca2+ for the final triggering and likely constitutes a distal ATP sensor for insulin exocytosis that acts in concert with ATP-sensitive K+ channels.
通过使用安培法测量胰岛β细胞中的胰岛素胞吐作用来研究胞质ATP在胞吐作用中的作用，胰岛β细胞通过笼锁Ca2+化合物的光解进行刺激。胰岛素胞吐作用以两种速率发生。我们发现ATP通过选择性增强较快速率的胞吐作用来加速和增强胞吐作用。一种不可水解的ATP类似物，腺苷5'-O-(3-硫代三磷酸)，它能阻断ATP酶，比ATP甚至更有效，这表明磷酸化事件发生在ATP依赖的囊泡运输和引发的下游。ATP的作用被cAMP的竞争性拮抗剂和腺苷酸环化酶的抑制剂消除。这些数据表征了一种涉及腺苷酸环化酶、cAMP依赖蛋白激酶以及可能的融合机制本身的Ca2+依赖胞吐作用的ATP传感机制。因此，快速胞吐机制需要磷酸化和Ca2+来进行最终触发，并且可能构成胰岛素胞吐作用的远端ATP传感器，它与ATP敏感钾通道协同作用。
