Synaptic vesicle endocytosis at a CNS nerve terminal: Faster kinetics at physiological temperatures and increased endocytotic capacity during maturation
Synaptic vesicle endocytosis at a CNS nerve terminal: Faster kinetics at physiological temperatures and increased endocytotic capacity during maturation
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DOI：
10.1152/jn.00898.2007
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发表时间：
2007-12-01
影响因子：
2.5
通讯作者：
von Gersdorff, Henrique
中科院分区：
文献类型：
--
作者：
Renden, Robert;von Gersdorff, Henrique
CNS神经末梢的突触囊泡内吞作用：在生理温度下更快的动力学和成熟过程中增加的内吞能力。J Neurophysiol 98：3349-3359，2007.首次发表于2007年10月17日; doi：10.1152/jn.00898.2007。突触囊泡膜必须在大量胞吐后快速回收和再循环，以限制囊泡池的消耗。在室温（RT：23-24 ℃）下，使用来自出生后P7-P10天的未成熟大鼠幼崽的膜电容测量直接测量Held神经末梢的萼处的内吞速率。该速率具有数十秒的平均时间常数，并且当胞吐量（测量为电容跳跃）增加时变得更慢。对于一个可以在高输入频率下连续工作的突触来说，这样慢的速度似乎是矛盾的。在这里，我们进行时间分辨的膜电容测量从小鼠杯举行的脑干切片在生理温度（PT：35-37摄氏度），也从更成熟的肾盏后的听力发作（P14-P18）。我们的研究结果表明，内吞率是强烈的温度依赖性，而神经末梢的内吞能力是依赖于发育阶段。在PT，我们发现，内吞作用加速由于增加了一个动力学快速组件（时间常数：τ = 1-2秒）后立即胞吐。令人惊讶的是，我们发现在RT下，P14-P18小鼠中由短（1- 5-ms）或长（>= 10-ms）去极化脉冲触发的内吞速率是相似的（τ约为15 s）。此外，该速率在PT处大大加速（τ约为2s）。因此，在突触成熟过程中，内吞作用变得更快，饱和度更低，使得萼末端更有能力维持长时间的高频递质释放。
Synaptic vesicle endocytosis at a CNS nerve terminal: faster kinetics at physiological temperatures and increased endocytotic capacity during maturation. J Neurophysiol 98: 3349-3359, 2007. First published October 17, 2007; doi:10.1152/jn.00898.2007. Synaptic vesicle membrane must be quickly retrieved and recycled after copious exocytosis to limit the depletion of vesicle pools. The rate of endocytosis at the calyx of Held nerve terminal has been measured directly using membrane capacitance measurements from immature postnatal day P7-P10 rat pups at room temperature (RT: 23-24 degrees C). This rate has an average time constant of tens of seconds and becomes slower when the amount of exocytosis (measured as capacitance jump) increases. Such slow rates seem paradoxical for a synapse that can operate continuously at high-input frequencies. Here we perform time-resolved membrane capacitance measurements from the mouse calyx of Held in brain stem slices at physiological temperature (PT: 35-37 degrees C), and also from more mature calyces after the onset of hearing (P14-P18). Our results show that the rate of endocytosis is strongly temperature dependent, whereas the endocytotic capacity of a nerve terminal is dependent on developmental stage. At PT we find that endocytosis accelerates due to the addition of a kinetically fast component (time constant: tau = 1-2 s) immediately after exocytosis. Surprisingly, we find that at RT the rate of endocytosis triggered by short (1- to 5-ms) or long (>= 10-ms) depolarizing pulses in P14-P18 mice are similar (tau approximate to 15 s). Furthermore, this rate is greatly accelerated at PT (tau approximate to 2 s). Thus endocytosis becomes faster and less saturable during synaptic maturation, making the calyceal terminal more capable of sustaining prolonged high-frequency transmitter release.