Synaptic vesicle recycling and changes in synaptic efficacy

我们希望阐明果蝇神经肌肉接头突触囊泡的内吞机制及其在突触传递中的作用。突触囊泡的胞吐和胞吞被认为是由相同的Ca 2+内流控制的，因为胞吞总是在胞吐之后，并且这两个过程都需要外部Ca 2+。我们发现，La ~（3+）和fulunarizine，Ca ~（2+）通道阻滞剂，抑制内吞作用而不影响胞吐作用，而PLTXII，蜘蛛毒素的Ca ~（2+）通道阻滞剂，抑制主要是胞吐作用。这些结果表明，Ca 2+内流通过不同的途径控制胞吐和胞吞.使用Ca 2+通道阻断剂，我们发现两种不同的内吞作用;活性区内吞作用和非活性区内吞作用。活性区内吞作用不依赖于网格蛋白，在高活性的早期进行，而非活性区内吞作用依赖于网格蛋白，在高活性的晚期进行。这些结果表明，高活性的突触传递是由两种类型的内吞协调维持的。

We wish to clarify mechanisms of endocytosis of synaptic vesicles and roles of endocytosis in synaptic transmission at Drosophila Neuromuscular junction.1. It has been believed that exocytosis and endocytosis of synaptic vesicles are controlled by the same Ca2+ influx, because endocytosis always follows exocytosis and both process require external Ca2+. We found that La3+ and fulunarizine, Ca2+ channel blocker, depressed endocytosis without affecting exocytosis, while PLTXII, Ca2+ channel blocker from spider toxin, depressed predominantly exocytosis. These results suggest that Ca2+ influx through distinct routes controls exocytosis and endocytosis.2. Using Ca2+ channel blockers, we revealed two distinct endocytosis; active-zone endocytosis and non-active-zone endocytosis. Active-zone endocytosis is clathrin-independent and operate early phase of high activity, whereas non-active-zone endocytosis is clathrin-dependent and works in late phase of high activity. These results suggest that synaptic transmission at high activity is maintained coordinately by two types of endocytosis.