Sørensen Jakob B, Nagy Gábor, Varoqueaux Frederique, Nehring Ralf B, Brose Nils, Wilson Michael C, Neher Erwin
Max-Planck-Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany.
Cell. 2003 Jul 11;114(1):75-86. doi: 10.1016/s0092-8674(03)00477-x.
The SNARE complex, consisting of synaptobrevin, syntaxin, and SNAP-25, is essential for calcium-triggered exocytosis in neurosecretory cells. Little is known, however, about how developmentally regulated isoforms and other cognate SNARE components regulate vesicular fusion. To address this question, we examined neuroexocytosis from chromaffin cells of Snap25 null mice rescued by the two splice variants SNAP-25a and SNAP-25b and the ubiquitously expressed homolog SNAP-23. In the absence of SNAP-25, vesicle docking persisted, but primed vesicle pools were empty and fast calcium-triggered release abolished. Single vesicular fusion events showed normal characteristics, except for a shorter duration of the fusion pore. Overexpression of SNAP-25a, SNAP-25b, and SNAP-23 resulted in three distinct phenotypes; SNAP-25b induced larger primed vesicle pools than SNAP-25a, whereas SNAP-23 did not support a standing pool of primed vesicles. We conclude that three alternative SNARE components support exocytosis, but they differ in their ability to stabilize vesicles in the primed state.
由突触小泡蛋白、 syntaxin和SNAP - 25组成的SNARE复合体对于神经分泌细胞中钙触发的胞吐作用至关重要。然而，关于发育调控的亚型和其他同源SNARE成分如何调节囊泡融合，我们知之甚少。为了解决这个问题，我们检测了由两种剪接变体SNAP - 25a和SNAP - 25b以及普遍表达的同源物SNAP - 23拯救的Snap25基因敲除小鼠的嗜铬细胞的神经胞吐作用。在没有SNAP - 25的情况下，囊泡对接持续存在，但引发的囊泡池为空，快速钙触发释放被消除。单个囊泡融合事件显示出正常特征，只是融合孔的持续时间较短。SNAP - 25a、SNAP - 25b和SNAP - 23的过表达导致三种不同的表型；与SNAP - 25a相比，SNAP - 25b诱导产生更大的引发囊泡池，而SNAP - 23不支持引发囊泡的稳定池。我们得出结论，三种替代的SNARE成分支持胞吐作用，但它们在稳定处于引发状态的囊泡的能力上有所不同。
