Jorgačevski Jernej, Zorec Robert
Laboratory of Neuroendocrinology-Molecular Cell Physiology, Faculty of Medicine, University of Ljubljana; Ljubljana, Slovenia.
Commun Integr Biol. 2012 Jan 1;5(1):74-7. doi: 10.4161/cib.18166.
The release of hormones and neurotransmitters from vesicles can be modified by the regulation of the fusion pore, an aqueous channel that forms upon the fusion of the vesicle membrane with the plasma membrane. However, the mechanisms are unclear. Munc18-1 protein interacts with Syntaxin1 (Synt 1), a member of the SNARE proteins, which plays an important role in exocytosis. It has been shown that Munc18-1 has multiple roles, both in pre- and post-fusion stages of exocytosis. It regulates the traffic of Synt1 to the plasma membrane. By inhibiting the tethering of the vesicle SNARE protein Synaptobrevin 2 (Syb2) solely to Synt1 at the plasma membrane, but favoring the vesicular tethering to the preformed binary cis SNARE complex of Synt1A-SNAP25B, Munc18-1 is tuning vesicle docking and the membrane merger process. Additionally, Munc18-1 affects exocytosis at the post-fusion stage by regulating the fusion pore properties (i.e., dwell-time and fusion pore diameter). Among many possible mechanisms that may regulate the fusion pore, but have never been considered previously, is the influence of Munc18-1 on the membrane anisotropy, which determines the local spontaneous membrane curvature and the architecture of the fusion pore. We here propose that Munc18-1 affects the fusion pore by modulating the dynamic local (re)arrangement of anisotropic membrane components within the highly curved fusion pore nanostructure, to which proteins, lipids or their complexes can participate.
囊泡中激素和神经递质的释放可通过融合孔的调节来改变,融合孔是囊泡膜与质膜融合时形成的水通道。然而,其机制尚不清楚。Munc18-1蛋白与SNARE蛋白成员Syntaxin1(Synt 1)相互作用,Synt 1在胞吐作用中起重要作用。研究表明,Munc18-1在胞吐作用的融合前和融合后阶段均具有多种作用。它调节Synt1向质膜的转运。通过仅抑制囊泡SNARE蛋白突触小泡蛋白2(Syb2)在质膜上与Synt1的拴系,但促进囊泡与预先形成的Synt1A-SNAP25B二元顺式SNARE复合体的拴系,Munc18-1正在调节囊泡对接和膜融合过程。此外,Munc18-1通过调节融合孔特性(即停留时间和融合孔直径)影响融合后阶段的胞吐作用。在许多可能调节融合孔但以前从未被考虑过的机制中,Munc18-1对膜各向异性的影响是其中之一,膜各向异性决定了局部自发膜曲率和融合孔的结构。我们在此提出,Munc18-1通过调节高度弯曲的融合孔纳米结构内各向异性膜成分的动态局部(重新)排列来影响融合孔,蛋白质、脂质或其复合物均可参与其中。