Roles of ATP in depletion and replenishment of the releasable pool of synaptic vesicles
Roles of ATP in depletion and replenishment of the releasable pool of synaptic vesicles
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DOI：
10.1152/jn.2002.88.1.98
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发表时间：
2002-07-01
影响因子：
2.5
通讯作者：
Matthews, G
中科院分区：
文献类型：
--
作者：
Heidelberger, R;Sterling, P;Matthews, G
视网膜双极神经元的突触终末包含一组容易释放的突触小泡，这些囊泡经历快速的钙依赖释放。这个囊泡池的功能补充需要三磷酸腺苷的水解。然而，目前尚不清楚哪些步骤需要ATP水解：将小泡输送到其解剖释放部位，或者准备突触小泡和/或分泌装置进行融合。为了解决这个问题，我们用ATP或难于水解的类似物ATP-伽玛斯透析单个突触终末，并检查可释放池的大小、可释放池的再充盈以及解剖活动区的小泡数量。使用ATP-Gamma透析数分钟后，可释放池中已有的囊泡仍可排出。尽管这个池的解剖关系，即连接到活动区突触带的突触小泡的数量是完全正常的，但这个池并没有从功能上重新充盈。我们得出的结论是：1)由于现有的可释放池在长期抑制ATP水解的过程中是稳定的，而进入功能池的过程被阻止，进入池中的囊泡往往保持在那里直到融合；2)因为解剖池不受抑制ATP水解的影响，所以不会因为囊泡运动失败而导致功能池无法再填充；3)对于池的填充和融合至关重要的局部囊泡运动不依赖于传统的依赖于ATP的马达蛋白；以及4)需要ATP水解来将囊泡和/或释放位置的生化转换到融合能力状态。
Synaptic terminals of retinal bipolar neurons contain a pool of readily releasable synaptic vesicles that undergo rapid calcium-dependent release. ATP hydrolysis is required for the functional refilling of this vesicle pool. However, it was unclear which steps required ATP hydrolysis: delivery of vesicles to their anatomical release sites or preparation of synaptic vesicles and/or the secretory apparatus for fusion. To address this, we dialyzed single synaptic terminals with ATP or the poorly hydrolyzable analogue ATP-gammaS and examined the size of the releasable pool, refilling of the releasable pool, and the number of vesicles at anatomical active zones. After minutes of dialysis with ATP-gammaS, vesicles already in the releasable pool could still be discharged. This pool was not functionally refilled despite the fact that its anatomical correlate, the number of synaptic vesicles tethered to active zone synaptic ribbons, was completely normal. We conclude 1) because the existing releasable pool is stable during prolonged inhibition of ATP hydrolysis, whereas entry into the functional pool is blocked, a vesicle on entering the pool will tend to remain there until it fuses; 2) because the anatomical pool is unaffected by inhibition of ATP hydrolysis, failure to refill the functional pool is not caused by failure of vesicle movement; 3) local vesicle movements important for pool refilling and fusion are independent of conventional ATP-dependent motor proteins; and 4) ATP hydrolysis is required for the biochemical transition of vesicles and/or release sites to fusion-competent status.