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Claudins of the Thick Ascending Limb of Henle's Loop – From Interaction to Function
Author(s) -
Milatz Susanne,
Wulfmeyer Vera Christine,
Plain Allein,
Drewell Hoora,
Mutig Kerim,
Breiderhoff Timan,
Fromm Michael,
Hou Jianghui,
Bleich Markus,
Günzel Dorothee,
Himmerkus Nina
Publication year - 2016
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.30.1_supplement.1223.28
Subject(s) - claudin , paracellular transport , loop of henle , chemistry , biophysics , extracellular , tight junction , microbiology and biotechnology , immunostaining , reabsorption , membrane , anatomy , biology , permeability (electromagnetism) , biochemistry , sodium , immunohistochemistry , organic chemistry , immunology
The thick ascending limb of Henle's loop (TAL) drives paracellular Na + , Ca 2+ and Mg 2+ reabsorption via the tight junction (TJ). The TJ is composed of claudins which seal the paracellular cleft or form size‐, charge‐ and water‐specific pores. This is achieved by a concerted interaction of different claudin proteins within the same plasma membrane ( cis ‐interaction) and of neighboring plasma membranes ( trans ‐interaction) resulting in the formation of a complex TJ strand meshwork. Claudins consist of four transmembrane segments, a small intracellular loop and two extracellular loops. Single TAL segments were obtained from cortex or medulla and microperfused. Electrophysiological measurements of single tubules were combined with claudin expression analyses by subsequent immunostaining and confocal laser‐scanning microscopy. In order to gain insight into the molecular composition of TAL TJ strands, claudin cis‐ and trans‐ interaction was examined by means of live cell imaging and Förster/fluorescence resonance energy transfer (FRET) in an overexpression system. A set of TAL claudin protein chimeras was created to reveal determinants of interaction properties. Cortical and medullary TAL differed regarding their paracellular permeability properties and their equipment with claudins 3, 10, 11, 16, and 19. A clear correlation between dominance of specific claudins within the TJ and ion selectivity was observed. Although most of these claudins were co‐expressed within the TJ, some of them failed to interact with each other in cis‐ or in trans ‐configuration. Interaction analyses of claudin chimeras suggested an involvement of the extracellular loops of TAL claudins in cis‐ and trans ‐interaction. In conclusion, a specific claudin expression pattern along the TAL corticomedullary axis is revealed. This special composition of claudins can be explained by their particular interaction capabilities. We suggest the existence of at least two spatially distinct types of paracellular pores with different preferences for Na + , Ca 2+ and Mg 2+ in the TAL. Support or Funding Information Supported by DFG FOR 721/2; National Institutes of Health Grant R01DK084059