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Kiss-and-run fusion
Kiss-and-run fusion is a type of synaptic vesicle release where the vesicle opens and closes transiently. In this form of exocytosis, the vesicle docks and transiently fuses at the presynaptic membrane and releases its neurotransmitters across the synapse, after which the vesicle can then be reused.
Kiss-and-run differs from full fusion, where the vesicle collapses fully into the plasma membrane and is then later retrieved by a clathrin-coat-dependent process. The idea of kiss-and-run fusion was first introduced by Bernard Katz and Jose del Castillo in 1955, who together hypothesized that synaptic vesicles fuse transiently with the plasma membrane.〔 The actual term, kiss-and-run, originated from Bruno Ceccarelli in 1973, when he saw similar results to Katz and del Castillo using an electron microscope examining a frog neuromuscular junction. Today, there is back and forth debate over full fusion and kiss-and-run fusion and which model portrays a more accurate picture of the mechanisms behind synaptic release. The increased accumulation of partially empty secretory vesicles following secretion, observed in electron micrographs are the most compelling evidence in favor of the kiss-and-run model. Accumulation of partially empty vesicles following secretion suggests that during the secretory process, only a portion of the vesicular contents are able to exit the cell, which could only be possible if secretory vesicles were to temporarily establish continuity with the cell plasma membrane, expel a portion of their contents, then detach and reseal.
==Discovery==
Kiss-and-run fusion was first observed by Katz and del Castillo in 1955. However, the first systematic studies were conducted by Ceccarelli et al. in 1973. Ceccarelli et al. studied frog neuromuscular junctions, stimulating them with markers such as horseradish peroxidase to identify endocytosed organelles.〔 Ceccarelli et al. stimulated nerve-muscle preparations at either low stimulation (2 Hz) or high stimulation (10 Hz) for periods ranging from 20 minutes to 4 hours. At low stimulation for a period of 4 hours, Ceccarelli et al. found that there was an increase in horseradish peroxidase labeled vesicles over time, and no increases in large organelles, indicative of the vesicles fusing quickly with the presynaptic membrane and then separating from it after releasing its neurotransmitters.〔 They hypothesized that at low frequencies of stimulation, most of the vesicles are quickly re-formed from the presynaptic membrane during and after stimulation.〔 This gave rise to the term kiss-and-run. The most compelling evidence for transient or kiss-and-run fusion has come from the discovery of the porosome, a permanent cup-shaped lipoprotein structure at the cell plasma membrane, where secretory vesicles transiently dock and fuse to release intra-vesicular contents from the cell.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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