Tight junction proteins at the blood-brain barrier: far more than claudin-5
Tight junction proteins at the blood-brain barrier: far more than claudin-5
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DOI：
10.1007/s00018-019-03030-7
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发表时间：
2019-05-01
影响因子：
8
通讯作者：
Haseloff, Reiner F.
中科院分区：
文献类型：
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作者：
Berndt, Philipp;Winkler, Lars;Haseloff, Reiner F.
在血脑屏障（BBB）， claudin (Cldn)-5被认为是主要的紧密连接（TJ）蛋白，Cldn3和-12以及occludin也有少量贡献。然而，在Cldn5敲除小鼠中，血脑屏障在超微结构上表现正常，这表明进一步的Cldn5和/或tj相关的奇迹蛋白（TAMPs）参与其中。显微解剖的人和鼠脑毛细血管，快速冷冻以重现体内情况，显示Cldn5， -11, -12， -25和occludin的高转录表达，但在人体内也有丰富的Cldn1和-27水平。蛋白水平通过一种新的表位稀释试验进行量化，并确认各自的mRNA数据。与体内情况相反，Cldn5在体外主导BBB表达，因为所有其他TJ蛋白水平相对较低或不表达。Cldn11在体内非常丰富，并通过亲同寡聚化参与细胞旁紧密性，但在体外几乎消失。高水平的Cldn25既不加强细胞旁屏障，也不相互连接对立的细胞，但有助于正确的TJ链形态。病理条件下（体内缺血和体外缺氧）脑毛细血管Cldn1、-3、-12和occludin下调，与大鼠大脑中动脉闭塞后Cldn5上调平行。Cldn5敲除后，Cldn1表达增加。总之，这个完整的Cldn/TAMP图谱表明，在脑毛细血管中存在多达12种TJ蛋白。小鼠和人类在体内具有相似而复杂的TJ结构，但这种复杂性在体外条件下广泛消失。
At the blood-brain barrier (BBB), claudin (Cldn)-5 is thought to be the dominant tight junction (TJ) protein, with minor contributions from Cldn3 and -12, and occludin. However, the BBB appears ultrastructurally normal in Cldn5 knock-out mice, suggesting that further Cldns and/or TJ-associated marvel proteins (TAMPs) are involved. Microdissected human and murine brain capillaries, quickly frozen to recapitulate the in vivo situation, showed high transcript expression of Cldn5, -11, -12, and -25, and occludin, but also abundant levels of Cldn1 and -27 in man. Protein levels were quantified by a novel epitope dilution assay and confirmed the respective mRNA data. In contrast to the in vivo situation, Cldn5 dominates BBB expression in vitro, since all other TJ proteins are at comparably low levels or are not expressed. Cldn11 was highly abundant in vivo and contributed to paracellular tightness by homophilic oligomerization, but almost disappeared in vitro. Cldn25, also found at high levels, neither tightened the paracellular barrier nor interconnected opposing cells, but contributed to proper TJ strand morphology. Pathological conditions (in vivo ischemia and in vitro hypoxia) down-regulated Cldn1, -3, and -12, and occludin in cerebral capillaries, which was paralleled by up-regulation of Cldn5 after middle cerebral artery occlusion in rats. Cldn1 expression increased after Cldn5 knock-down. In conclusion, this complete Cldn/TAMP profile demonstrates the presence of up to a dozen TJ proteins in brain capillaries. Mouse and human share a similar and complex TJ profile in vivo, but this complexity is widely lost under in vitro conditions.