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The tight junction protein claudin‐2 forms a paracellular water channel
Author(s) -
Rosenthal Rita,
Milatz Susanne,
Krug Susanne M.,
Günzel Dorothee,
Oelrich Beibei,
Amasheh Salah,
Fromm Michael
Publication year - 2009
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.23.1_supplement.796.5
Subject(s) - paracellular transport , claudin , tight junction , chemistry , ussing chamber , biophysics , water transport , water flow , mannitol , microbiology and biotechnology , biology , permeability (electromagnetism) , biochemistry , membrane , in vitro , environmental engineering , engineering
There is an ongoing dispute concerning the existence of significant water flow across tight junctions (TJ). Instead of distinguishing technically between the possible routes for water, we measured transepithelial water transport in a video‐equipped Ussing chamber before and after TJ perturbation. For this, kidney tubule cells (MDCK‐C7) which lack genuine AQP‐2, claudin‐2, and claudin‐10b were stably transfected with claudin‐2 (C7‐CLDN2) or claudin‐10b (C7‐Cldn10b). Claudin‐2 is typically expressed in leaky epithelia and both form paracellular cation channels. Claudin transfections did not alter the expression of endogenous claudins or of the membranal water channels AQP‐1, ‐3, and ‐4. In the presence of an osmotic gradient (100 mM mannitol) water flow was markedly higher in C7‐CLDN2 cells than in vector controls. Water flow induced by a Na + gradient (80 mM, high Na + basolateral) was zero in controls and was present in C7‐CLDN2 cells. The combination of both gradients had additive effects on water flux. Comparison of different clones revealed a correlation between claudin‐2 expression and water flux. In contrast, water fluxes of C7‐Cldn10b cells were not different from that of vector controls. We conclude that the paracellular cation channel claudin‐2, but not claudin‐10b, forms a paracellular water channel and by this mediates paracellular water transport in leaky epithelia. (Supported by DFG FOR 721)