Marshall William S, Breves Jason P, Doohan Ellen M, Tipsmark Christian K, Kelly Scott P, Robertson George N, Schulte Patricia M
Department of Biology, St Francis Xavier University, Antigonish, NS, Canada B2G 2W5
Department of Biology, Skidmore College, Saratoga Springs, NY 12866, USA.
J Exp Biol. 2018 Jan 11;221(Pt 1):jeb168906. doi: 10.1242/jeb.168906.
To provide insight into claudin (Cldn) tight junction (TJ) protein contributions to branchial salt secretion in marine teleost fishes, this study examined TJ protein isoforms of a euryhaline teleost (mummichog; ) in association with salinity change and measurements of transepithelial cation selectivity. Mummichogs were transferred from freshwater (FW) to seawater (SW, 35‰) and from SW to hypersaline SW (2SW, 60‰) in a time course with transfer control groups (FW to FW, and SW to SW). FW to SW transfer increased mRNA abundance of and twofold, whilst and transcripts were unchanged. Transfer from SW to 2SW did not alter , and transiently altered abundance, but increased and fourfold. This was coincident with an increased number of single-stranded junctions (observed by transmission electron microscopy). For both salinity transfers, (1) mRNA was acutely responsive (i.e. after 24 h), (2) other responsive isoforms increased later (3-7 days), and (3) cystic fibrosis transmembrane conductance regulator () mRNA was elevated in accordance with established changes in transcellular Cl movement. Changes in mRNA encoding and appeared linked, consistent with the tandem repeat locus in the genome, whereas mRNA for tandem and seemed independent of each other. Cation selectivity sequence measured by voltage and conductance responses to artificial SW revealed Eisenman sequence VII: Na>K>Rb∼Cs>Li Collectively, these data support the idea that Cldn-10 TJ proteins create and maintain cation-selective pore junctions in salt-secreting tissues of teleost fishes.
为深入了解紧密连接蛋白（Cldn）在硬骨海鱼鳃部盐分分泌中的作用，本研究检测了广盐性硬骨鱼（食蚊鱼； ）紧密连接蛋白亚型与盐度变化以及跨上皮阳离子选择性测量之间的关系。食蚊鱼在一段时间内从淡水（FW）转移到海水（SW，35‰），再从海水转移到高盐海水（2SW，60‰），同时设置转移对照组（FW到FW，SW到SW）。从FW转移到SW使 和 的mRNA丰度增加了两倍，而 和 的转录本没有变化。从SW转移到2SW并没有改变 ，短暂改变了 的丰度，但使 和 增加了四倍。这与单链连接数量的增加相一致（通过透射电子显微镜观察）。对于这两种盐度转移，（1） 的mRNA反应迅速（即24小时后），（2）其他有反应的亚型稍后增加（3 - 7天），（3）囊性纤维化跨膜传导调节因子（ ）的mRNA根据跨细胞Cl运动的既定变化而升高。编码 和 的mRNA变化似乎有关联，这与 基因组中的串联重复位点一致，而串联 和 的mRNA似乎相互独立。通过对人工海水的电压和电导反应测量的阳离子选择性序列显示为艾森曼序列VII：Na>K>Rb∼Cs>Li。总的来说，这些数据支持这样一种观点，即紧密连接蛋白Cldn - 10在硬骨鱼的盐分分泌组织中形成并维持阳离子选择性孔道连接。
