Department of Biology, Institute of Molecular Biology & Biophysics, Eidgenössische Technische Hochschule Zürich, Otto-Stern-Weg 5, 8093 Zürich, Switzerland.
Interfaculty Institute of Microbiology and Infection Medicine Tübingen, Organismic Interactions, University of Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany.
Cell. 2019 Jul 11;178(2):374-384.e15. doi: 10.1016/j.cell.2019.05.055.
Multicellular lifestyle requires cell-cell connections. In multicellular cyanobacteria, septal junctions enable molecular exchange between sister cells and are required for cellular differentiation. The structure of septal junctions is poorly understood, and it is unknown whether they are capable of controlling intercellular communication. Here, we resolved the in situ architecture of septal junctions by electron cryotomography of cryo-focused ion beam-milled cyanobacterial filaments. Septal junctions consisted of a tube traversing the septal peptidoglycan. Each tube end comprised a FraD-containing plug, which was covered by a cytoplasmic cap. Fluorescence recovery after photobleaching showed that intercellular communication was blocked upon stress. Gating was accompanied by a reversible conformational change of the septal junction cap. We provide the mechanistic framework for a cell junction that predates eukaryotic gap junctions by a billion years. The conservation of a gated dynamic mechanism across different domains of life emphasizes the importance of controlling molecular exchange in multicellular organisms.
多细胞生物的生活方式需要细胞间的连接。在多细胞蓝细菌中，隔膜连接使姐妹细胞之间能够进行分子交换，并且对于细胞分化是必需的。隔膜连接的结构还不太清楚，也不知道它们是否能够控制细胞间的通讯。在这里，我们通过对冷冻聚焦离子束铣削的蓝细菌丝进行电子 cryotomography 解析了原位隔膜连接的结构。隔膜连接由穿过隔膜肽聚糖的管组成。每个管端包含一个含有 FraD 的塞子，该塞子被细胞质帽覆盖。光漂白后的荧光恢复表明，在受到胁迫时，细胞间的通讯被阻断。门控伴随着隔膜连接帽的可逆构象变化。我们为一个细胞连接提供了一个机制框架，这个连接比真核间隙连接早了 10 亿年。在不同生命领域中，门控动态机制的保守性强调了在多细胞生物中控制分子交换的重要性。
