ENDOCYTOSIS OF SYNAPTIC VESICLE MEMBRANE AT THE FROG NEUROMUSCULAR-JUNCTION
ENDOCYTOSIS OF SYNAPTIC VESICLE MEMBRANE AT THE FROG NEUROMUSCULAR-JUNCTION
复制标题
DOI：
10.1083/jcb.98.2.685
复制
发表时间：
1984-01-01
影响因子：
7.8
通讯作者：
HEUSER, JE
中科院分区：
文献类型：
--
作者：
MILLER, TM;HEUSER, JE
蛙神经肌肉制备物在4-氨基吡啶（4-AP）的存在下，在单个电刺激后的不同时间进行速冻，之后通过冷冻断裂观察运动神经末梢。这样的刺激导致从每个神经末梢迅速释放3000-6000个突触囊泡，并在其质膜上添加大量的突触囊泡膜。在刺激后1 s和2 min之间的间隔期间，可观察到该囊泡膜回末端的内吞回收。观察到两种不同类型的内吞作用。第一次似乎是快速和非选择性的。在刺激后的前几秒内，相对大的空泡（约0.1μ m）从质膜夹断，靠近和远离活性区。这种液泡在其形成过程中的任何阶段都不被网格蛋白包被。第二个内吞过程较慢，似乎是选择性的，因为它内化了大的膜内颗粒。这一过程首先表现为形成相对较小的（约0.05μ m）的凹陷，其出现在除了活性区之外的任何地方。这些凹陷在1秒时首次出现，在刺激后30秒达到5.5/μ m2的峰值丰度，并且在90秒时几乎完全消失。显然，这些压痕对应于网格蛋白包被的凹坑。它们的总丰度与最初排出的囊泡数量相当。这些内吞结构可分为4种中间形式，其相对丰度随时间的变化表明，在这种类型的神经末梢，包被囊泡的内吞具有以下特点：相对于2 min的时间尺度，单个内吞事件持续时间短，早期形式持续时间长于晚期形式;并且单个事件在刺激之后不久在平坦配置中花费的其寿命的一部分比其稍后花费的少。
Frog nerve-muscle preparations were quick-frozen at various times after a single electrical stimulus in the presence of 4-aminopyridine (4-AP), after which motor nerve terminals were visualized by freeze-fracture. Such stimulation causes prompt discharge of 3000-6000 synaptic vesicles from each nerve terminal and adds a large amount of synaptic vesicle membrane to its plasmalemma. The endocytic retrieval of this vesicle membrane back into the terminal was visualized during the interval between 1 s and 2 min after stimulation. Two distinct types of endocytosis were observed. The 1st appeared to be rapid and nonselective. Within the 1st few seconds after stimulation, relatively large vacuoles (.apprx. 0.1 .mu.m) pinched off from the plasma membrane, both near to and far away from the active zones. Such vacuoles are not coated with clathrin at any stage during their formation. The 2nd endocytic process was slower and appeared to be selective, because it internalized large intramembrane particles. This process was manifest first by the formation of relatively small (.apprx. 0.05 .mu.m) indentations in the plasma membrane, which occurred everywhere except at the active zones. These indentations first appeared at 1 s, reached a peak abundance of 5.5/.mu.m2 by 30 s after the stimulus and disappeared almost completely by 90 s. Evidently, these indentations correspond to clathrin-coated pits. Their total abundance is comparable with the number of vesicles that were discharged initially. These endocytic structures could be classified into 4 intermediate forms, whose relative abundance over time suggests that, at this type of nerve terminal, endocytosis of coated vesicles has the following characteristics: the single endocytotic event is short lived relative to the time scale of 2 min; earlier forms last longer than later forms; and a single event spends a smaller portion of its lifetime in the flat configuration soon after the stimulus than it does later on.