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Claudin‐17 forms a paracellular anion channel in proximal kidney tubules
Author(s) -
Krug Susanne Marlen,
Rosenthal Rita,
Günzel Dorothee,
Amasheh Salah,
Schulzke Jörg Dieter,
Fromm Michael
Publication year - 2011
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.25.1_supplement.1036.5
Subject(s) - claudin , paracellular transport , tight junction , nephron , chemistry , kidney , permeability (electromagnetism) , biophysics , ultrastructure , microbiology and biotechnology , renal function , biochemistry , biology , endocrinology , anatomy , membrane
Many of the 24 different claudins strenghten the barrier of the tight junction, while a few others, in contrast, form paracellelular channels for cations, anions, or water. One of the claudins with unknown function is claudin‐17 which is suggested to be expressed in kidney or skin tissue. Methods Expression and localization of claudin‐17 was analyzed in different tissues, and barrier function was examined in overexpression clones of MDCK C7 cells. Two‐path impedance spectroscopy, permeability measurements for ions and paracellular markers, confocal microscopy, and freeze fracture EM were performed to characterize claudin‐17 in detail. Results Claudin‐17 was detected sparsely in brain tissue, but primarily in kidney tissues. There it was found mainly in proximal nephron and was gradually decreased to more distal segments. Overexpression of claudin‐17 did not alter other claudins and resulted in a decrease of paracellular resistance. Dilution potential measurements revealed this decrease to be predominantly based on an increased anion permeability. Larger anionic solutes, e.g. fluorescein remained unaffected, as well as no changes of ultrastructure were observable in freeze fracture EMs. Conclusion Claudin‐17 was functionally characterized to be a channel‐forming TJ protein of the proximal segments of the kidney which exhibits preference for anions. (Supported by DFG FOR 721)