Vaithianathan Thirumalini, Wollmuth Lonnie P, Henry Diane, Zenisek David, Matthews Gary
Department of Neurobiology and Behavior, Stony Brook University, Stony Brook, NY 11794, USA.
Department of Neurobiology and Behavior, Stony Brook University, Stony Brook, NY 11794, USA; Center for Nervous System Disorders, Stony Brook University, Stony Brook, NY 11794, USA; Department of Biochemistry & Cell Biology, Stony Brook University, Stony Brook, NY 11794, USA.
iScience. 2019 Jul 26;17:10-23. doi: 10.1016/j.isci.2019.06.015. Epub 2019 Jun 13.
Clearance of synaptic vesicle proteins from active zones may be rate limiting for sustained neurotransmission. Issues of clearance are critical at ribbon synapses, which continually release neurotransmitters for prolonged periods of time. We used synaptophysin-pHluorin (SypHy) to visualize protein clearance from active zones in retinal bipolar cell ribbon synapses. Depolarizing voltage steps gave rise to small step-like changes in fluorescence likely indicating release of single SypHy molecules from fused synaptic vesicles near active zones. Temporal and spatial fluorescence profiles of individual responses were highly variable, but ensemble averages were well fit by clearance via free diffusion using Monte Carlo simulations. The rate of fluorescence decay of ensemble averages varied with the time and location of the fusion event, with clearance being most rapid at the onset of a stimulus when release rate is the highest.
从活性区清除突触小泡蛋白可能是持续神经传递的限速步骤。清除问题在带状突触中至关重要，因为带状突触会持续长时间释放神经递质。我们使用突触素-pH荧光蛋白（SypHy）来观察视网膜双极细胞带状突触中活性区的蛋白清除情况。去极化电压阶跃引起荧光的小阶梯状变化，这可能表明单个SypHy分子从活性区附近融合的突触小泡中释放出来。单个反应的时间和空间荧光分布高度可变，但通过蒙特卡罗模拟，总体平均值通过自由扩散清除得到了很好的拟合。总体平均值的荧光衰减速率随融合事件的时间和位置而变化，在刺激开始时释放速率最高时清除最快。
