National Institute of Neurological Disorders and Stroke, 35 Convent Drive, Building 35, Room 2B-1012, Bethesda, MD 20892, USA.
Cell Rep. 2013 May 30;3(5):1414-21. doi: 10.1016/j.celrep.2013.03.010. Epub 2013 May 2.
Rapid endocytosis, which takes only a few seconds, is widely observed in secretory cells. Although it is more efficient in recycling vesicles than in slow clathrin-mediated endocytosis, its underlying mechanism, thought to be clathrin independent, is largely unclear. Here, we report that cleavage of three SNARE proteins essential for exocytosis, including synaptobrevin, SNAP-25, and syntaxin, inhibited rapid endocytosis at the calyx of Held nerve terminal, suggesting the involvement of the three SNARE proteins in rapid endocytosis. These SNARE proteins were also involved in slow endocytosis. In addition, SNAP-25 and syntaxin facilitated vesicle mobilization to the readily releasable pool, most likely via their roles in endocytosis and/or exocytosis. We conclude that both rapid and slow endocytosis share the involvement of SNARE proteins. The dual role of three SNARE proteins in exo- and endocytosis suggests that SNARE proteins may be molecular substrates contributing to the exocytosis-endocytosis coupling, which maintains exocytosis in secretory cells.
快速内吞作用只需几秒钟，在分泌细胞中广泛观察到。虽然它在回收小泡方面比慢的网格蛋白介导的内吞作用更有效，但它的潜在机制，被认为与网格蛋白无关，在很大程度上尚不清楚。在这里，我们报告说，三种对于胞吐作用至关重要的 SNARE 蛋白（包括突触融合蛋白、SNAP-25 和突触素）的切割抑制了 Held 神经末梢的大囊泡快速内吞作用，这表明这三种 SNARE 蛋白参与了快速内吞作用。这些 SNARE 蛋白也参与了慢的内吞作用。此外，SNAP-25 和突触素促进了囊泡向易释放池的动员，这很可能是通过它们在内吞作用和/或胞吐作用中的作用。我们的结论是，快速和慢的内吞作用都涉及 SNARE 蛋白。三种 SNARE 蛋白在胞吐和内吞作用中的双重作用表明，SNARE 蛋白可能是分子底物，有助于维持分泌细胞中胞吐作用的外排-内吞偶联。
