Instituto de Neurociencias, CSIC-UMH, San Juan de Alicante, Spain.
Departmento de Neurociencias (CIMA), Universidad de Navarra, Pamplona, Spain.
Brain Struct Funct. 2019 Dec;224(9):3263-3276. doi: 10.1007/s00429-019-01966-x. Epub 2019 Oct 30.
Most vesicles in the interior of synaptic terminals are clustered in clouds close to active zone regions of the plasma membrane where exocytosis occurs. Electron-dense structures, termed bridges, have been reported between a small minority of pairs of neighboring vesicles within the clouds. Synapsin proteins have been implicated previously, but the existence of the bridges as stable structures in vivo has been questioned. Here we use electron tomography to show that the bridges are present but less frequent in synapsin knockouts compared to wildtype. An analysis of distances between neighbors in wildtype tomograms indicated that the bridges are strong enough to resist centrifugal forces likely induced by fixation with aldehydes. The results confirm that the bridges are stable structures and that synapsin proteins are involved in formation or stabilization.
大多数神经末梢内部的囊泡聚集在靠近质膜活性区域的云状结构中，在该处囊泡发生胞吐作用。在云状结构内的一小部分相邻囊泡之间，曾报道存在电子致密结构，称为桥。先前曾提到突触结合蛋白（synapsin）的作用，但这些桥在体内作为稳定结构的存在一直受到质疑。在这里，我们使用电子断层扫描技术显示，与野生型相比，桥在突触结合蛋白敲除小鼠中出现的频率较低，但仍存在。对野生型断层扫描图像中相邻物之间距离的分析表明，这些桥足够坚固，可以抵抗醛固定过程中可能产生的离心力。结果证实，这些桥是稳定的结构，并且突触结合蛋白参与其形成或稳定。
