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Selective decrease in paracellular conductance of tight junctions: role of the first extracellular domain of
Huajie Wen1, Debbie D Watry, M Cecilia G Marcondes
1Department of Neuropharmacology, The Scripps Research Institute, La Jolla, CA 92037, USA.
Molecular and Cellular Biology
|September 16, 2004
Summary
Claudin-5 protein expression significantly enhances the barrier function of endothelial tight junctions, selectively reducing ion permeability. Mutations in claudin-5, particularly cysteines, disrupt this barrier and alter paracellular flux.
Area of Science:
- Cell biology
- Biochemistry
- Physiology
Background:
- Claudin-5 is a key protein in endothelial tight junctions.
- Tight junctions form the blood-brain barrier, controlling molecular exchange.
- The precise role of claudin-5 in barrier function requires further elucidation.
Purpose of the Study:
- To investigate the contribution of claudin-5 to tight junction barrier function.
- To determine how claudin-5 expression affects permeability to ions and molecules.
- To explore the impact of claudin-5 mutations on tight junction properties.
Main Methods:
- Expression of murine claudin-5 in Madin-Darby canine kidney II cells.
- Measurement of transepithelial electrical resistance and conductance.
- Assessment of paracellular flux for ions and monosaccharides.
- Site-directed mutagenesis of claudin-5 extracellular domain residues.
Main Results:
- Claudin-5 expression increased transepithelial resistance fivefold.
- Claudin-5 reduced monovalent cation conductance.
- Paracellular flux of monosaccharides remained unchanged.
- Mutations of conserved cysteines abolished the barrier-enhancing effect.
- Mutation of Cys(64) increased monosaccharide paracellular flux.
Conclusions:
- Claudin-5 expression selectively decreases tight junction permeability to ions.
- Conserved cysteines in claudin-5 are critical for its barrier function.
- Molecular insights into claudin-5 may explain blood-brain barrier selectivity.