Institute of Physical Chemistry, Georg-August-University, Göttingen, 37077, Germany.
Max-Planck-Institute for Dynamics and Self-Organization, Göttingen, 37077, Germany.
Sci Rep. 2017 Sep 21;7(1):12070. doi: 10.1038/s41598-017-12348-w.
The large gap in time scales between membrane fusion occurring in biological systems during neurotransmitter release and fusion observed between model membranes has provoked speculations over a large number of possible factors that might explain this discrepancy. One possible reason is an elevated lateral membrane tension present in the presynaptic membrane. We investigated the tension-dependency of fusion using model membranes equipped with a minimal fusion machinery consisting of syntaxin 1, synaptobrevin and SNAP 25. Two different strategies were realized; one based on supported bilayers and the other one employing sessile giant liposomes. In the first approach, isolated patches of planar bilayers derived from giant unilamellar vesicles containing syntaxin 1 and preassembled SNAP 25 (ΔN-complex) were deposited on a dilatable PDMS sheet. In a second approach, lateral membrane tension was controlled through the adhesion of intact giant unilamellar vesicles on a functionalized surface. In both approaches fusion efficiency increases considerably with lateral tension and we identified a threshold tension of 3.4 mN m, at which the number of fusion events is increased substantially.
在生物系统中神经递质释放时发生的膜融合与模型膜之间观察到的融合之间存在着巨大的时间尺度差距，这引发了对可能解释这种差异的大量因素的推测。一个可能的原因是在突触前膜中存在升高的侧向膜张力。我们使用配备了由突触融合蛋白 1、融合蛋白 synaptobrevin 和 SNAP 25 组成的最小融合机制的模型膜研究了融合的张力依赖性。实现了两种不同的策略；一种基于支撑双层膜，另一种采用贴壁的巨大脂质体。在第一种方法中，从含有突触融合蛋白 1 和预组装的 SNAP 25（ΔN 复合物）的巨大单层囊泡衍生的平面双层膜的分离斑块被沉积在可膨胀的 PDMS 片上。在第二种方法中，通过完整的巨大单层囊泡在功能化表面上的粘附来控制侧向膜张力。在这两种方法中，融合效率都随着侧向张力的增加而大大提高，我们确定了一个 3.4 mN m 的阈值张力，在这个张力下，融合事件的数量显著增加。
