Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, Australia.
PLoS One. 2011;6(11):e27820. doi: 10.1371/journal.pone.0027820. Epub 2011 Nov 18.
How fusion pore formation during exocytosis affects the subsequent release of vesicle contents remains incompletely understood. It is unclear if the amount released per vesicle is dependent upon the nature of the developing fusion pore and whether full fusion and transient kiss and run exocytosis are regulated by similar mechanisms. We hypothesise that if consistent relationships exist between these aspects of exocytosis then they will remain constant across any age. Using amperometry in mouse chromaffin cells we measured catecholamine efflux during single exocytotic events at P0, 1 month and 6 months. At all ages we observed full fusion (amperometric spike only), full fusion preceded by fusion pore flickering (pre-spike foot (PSF) signal followed by a spike) and pure "kiss and run" exocytosis (represented by stand alone foot (SAF) signals). We observe age-associated increases in the size of all 3 modes of fusion but these increases occur at different ages. The release probability of PSF signals or full spikes alone doesn't alter across any age in comparison with an age-dependent increase in the incidence of "kiss and run" type events. However, the most striking changes we observe are age-associated changes in the relationship between vesicle size and the membrane bending energy required for exocytosis. Our data illustrates that vesicle size does not regulate release probability, as has been suggested, that membrane elasticity or flexural rigidity change with age and that the mechanisms controlling full fusion may differ from those controlling "kiss and run" fusion.
融合孔在胞吐作用期间的形成如何影响随后的囊泡内容物的释放仍不完全清楚。尚不清楚每个囊泡释放的量是否取决于正在形成的融合孔的性质，以及完全融合和短暂的吻合并跑胞吐作用是否受类似机制的调节。我们假设，如果胞吐作用的这些方面之间存在一致的关系，那么它们将在任何年龄段保持不变。我们使用微电极安培法在 P0、1 个月和 6 个月的小鼠嗜铬细胞中测量单胞吐事件期间儿茶酚胺的外排。在所有年龄段，我们都观察到了完全融合（仅安培测量尖峰）、融合孔闪烁（尖峰前足（PSF）信号随后是尖峰）和纯“吻合并跑”胞吐作用（由独立的足（SAF）信号表示）。我们观察到所有 3 种融合模式的大小都随年龄增加，但这些增加发生在不同的年龄。与“吻合并跑”类型事件的发生率随年龄增加相比，PSF 信号或仅完全尖峰的释放概率在任何年龄段都没有改变。然而，我们观察到的最显著变化是与囊泡大小和胞吐作用所需的膜弯曲能之间的关系随年龄而变化。我们的数据表明，囊泡大小不调节释放概率，正如先前提出的那样，膜弹性或弯曲刚度随年龄而变化，并且控制完全融合的机制可能与控制“吻合并跑”融合的机制不同。
