Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109, USA.
Mol Biol Cell. 2011 Jun 1;22(11):1907-18. doi: 10.1091/mbc.E11-02-0101. Epub 2011 Apr 1.
Dynamin is a master regulator of membrane fission in endocytosis. However, a function for dynamin immediately upon fusion has also been suspected from a variety of experiments that measured release of granule contents. The role of dynamin guanosine triphosphate hydrolase (GTPase) activity in controlling fusion pore expansion and postfusion granule membrane topology was investigated using polarization optics and total internal reflection fluorescence microscopy (pTIRFM) and amperometry. A dynamin-1 (Dyn1) mutant with increased GTPase activity resulted in transient deformations consistent with rapid fusion pore widening after exocytosis; a Dyn1 mutant with decreased activity slowed fusion pore widening by stabilizing postfusion granule membrane deformations. The experiments indicate that, in addition to its role in endocytosis, GTPase activity of dynamin regulates the rapidity of fusion pore expansion from tens of milliseconds to seconds after fusion. These findings expand the membrane-sculpting repertoire of dynamin to include the regulation of immediate postfusion events in exocytosis that control the rate of release of soluble granule contents.
动力蛋白是胞吞作用中膜裂变的主要调节因子。然而，从各种测量颗粒内容物释放的实验中，也怀疑动力蛋白在融合后立即发挥作用。使用偏光光学和全内反射荧光显微镜（pTIRFM）和安培法研究了动力蛋白鸟苷三磷酸水解酶（GTPase）活性在控制融合孔扩张和融合后颗粒膜拓扑结构中的作用。具有增加的 GTPase 活性的动力蛋白-1（Dyn1）突变体导致与胞吐作用后快速融合孔变宽一致的短暂变形；活性降低的 Dyn1 突变体通过稳定融合后颗粒膜变形来减缓融合孔变宽。这些实验表明，除了在胞吞作用中的作用外，动力蛋白的 GTPase 活性还调节融合后数十毫秒至数秒内融合孔扩张的速度。这些发现扩展了动力蛋白的膜塑造范围，包括调节胞吐作用中融合后立即发生的事件，以控制可溶性颗粒内容物释放的速度。
