Cárdenas-García Sandra P, Ijaz Sundas, Pereda Alberto E
Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
bioRxiv. 2023 Jul 28:2023.07.25.550347. doi: 10.1101/2023.07.25.550347.
Most nervous systems combine both transmitter-mediated and direct cell-cell communication, known as 'chemical' and 'electrical' synapses, respectively. Chemical synapses can be identified by their multiple structural components. Electrical synapses are, on the other hand, generally defined by the presence of a 'gap junction' (a cluster of intercellular channels) between two neuronal processes. However, while gap junctions provide the communicating mechanism, it is unknown whether electrical transmission requires the contribution of additional cellular structures. We investigated this question at identifiable single synaptic contacts on the zebrafish Mauthner cells, at which gap junctions coexist with specializations for neurotransmitter release and where the contact defines the anatomical limits of a synapse. Expansion microscopy of these contacts revealed a detailed map of the incidence and spatial distribution of proteins pertaining to various synaptic structures. Multiple gap junctions of variable size were identified by the presence of their molecular components. Remarkably, most of the synaptic contact's surface was occupied by interleaving gap junctions and components of adherens junctions, suggesting a close functional association between these two structures. In contrast, glutamate receptors were confined to small peripheral portions of the contact, indicating that most of the synaptic area works as an electrical synapse. Thus, our results revealed the overarching organization of an electrical synapse that operates with not one, but multiple gap junctions, in close association with structural and signaling molecules known to be components of AJs. The relationship between these intercellular structures will aid in establishing the boundaries of electrical synapses found throughout animal connectomes and provide insight into the structural organization and functional diversity of electrical synapses.
大多数神经系统结合了递质介导和直接的细胞间通讯，分别被称为“化学”和“电”突触。化学突触可通过其多个结构成分来识别。另一方面，电突触通常由两个神经元突起之间存在的“缝隙连接”（一组细胞间通道）来定义。然而，虽然缝隙连接提供了通讯机制，但电传递是否需要额外细胞结构的参与尚不清楚。我们在斑马鱼Mauthner细胞上可识别的单个突触接触点研究了这个问题，在这些接触点，缝隙连接与神经递质释放特化结构共存，且该接触点定义了突触的解剖学界限。对这些接触点进行扩展显微镜检查揭示了与各种突触结构相关的蛋白质的发生率和空间分布的详细图谱。通过其分子成分的存在鉴定出了多个大小可变的缝隙连接。值得注意的是，突触接触的大部分表面被交错的缝隙连接和黏着连接成分占据，这表明这两种结构之间存在密切的功能关联。相比之下，谷氨酸受体局限于接触点的小周边部分，这表明大部分突触区域起着电突触的作用。因此，我们的结果揭示了一种电突触的总体组织，它不是通过一个而是多个缝隙连接来运作，并且与已知为黏着连接成分的结构和信号分子密切相关。这些细胞间结构之间的关系将有助于确定在整个动物连接组中发现的电突触的界限，并深入了解电突触的结构组织和功能多样性。
