Claudin-21 has a paracellular channel role at tight junctions
H. Tanaka, Y. Yamamoto, H. Kashihara, Y. Yamazaki, K. Tani, Y. Fujiyoshi, K. Mineta, K. Takeuchi, A. Tamura, S. Tsukita
Mol Cell Biol, 36(6), pp. 954-964, (2016)
Claudin protein family members, of which there are at least 27 in human and mouse, polymerize to form tight junctions (TJs) between cells, in a tissue- and developmental stage-specific manner. Claudins have a paracellular barrier function. In addition, certain claudins function as paracellular channels for small ions and/or solutes by forming selective pores at the TJs, although the specific claudins involved and their functional mechanisms are still in question. Here we show for the first time that claudin-21, which is more highly expressed in the embryonic than postnatal stages, acts as a paracellular channel for small cations, such as Na+, similar to the typical channel-type claudins-2 and -15. Claudin-21 also allows the paracellular passage of larger solutes. Our findings suggest that claudin-21-based TJs allow the passage of small and larger solutes by both paracellular channel-based and some additional mechanisms.
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