Redox Regulation of Cell Contacts by Tricellulin and Occludin: Redox-Sensitive Cysteine Sites in Tricellulin Regulate Both Tri- and Bicellular Junctions in Tissue Barriers as Shown in Hypoxia and Ischemia.

Abstract

UNLABELLED:

Tight junctions (TJs) seal paracellular clefts in epithelia/endothelia and form tissue barriers for proper organ function. TJ-associated marvel proteins (TAMPs; tricellulin, occludin, marvelD3) are thought to be relevant to regulation. Under normal conditions, tricellulin tightens tricellular junctions against macromolecules. Traces of tricellulin occur in bicellular junctions.

AIMS:

As pathological disturbances have not been analyzed, the structure and function of human tricellulin, including potentially redox-sensitive Cys sites, were investigated under reducing/oxidizing conditions at 3- and 2-cell contacts.

RESULTS:

Ischemia, hypoxia, and reductants redistributed tricellulin from 3- to 2-cell contacts. The extracellular loop 2 (ECL2; conserved Cys321, Cys335) trans-oligomerized between three opposing cells. Substitutions of these residues caused bicellular localization. Cys362 in transmembrane domain 4 contributed to bicellular heterophilic cis-interactions along the cell membrane with claudin-1 and marvelD3, while Cys395 in the cytosolic C-terminal tail promoted homophilic tricellullar cis-interactions. The Cys sites included in homo-/heterophilic bi-/tricellular cis-/trans-interactions contributed to cell barrier tightness for small/large molecules.

INNOVATION:

Tricellulin forms TJs via trans- and cis-association in 3-cell contacts, as demonstrated electron and quantified fluorescence microscopically; it tightens 3- and 2-cell contacts. Tricellulin's ECL2 specifically seals 3-cell contacts redox dependently; a structural model is proposed.

CONCLUSIONS:

TAMP ECL2 and claudins' ECL1 share functionally and structurally similar features involved in homo-/heterophilic tightening of cell-cell contacts. Tricellulin is a specific redox sensor and sealing element at 3-cell contacts and may compensate as a redox mediator for occludin loss at 2-cell contacts in vivo and in vitro. Molecular interaction mechanisms were proposed that contribute to tricellulin's function. In conclusion, tricellulin is a junctional redox regulator for ischemia-related alterations.

• Authors: Jimmi Cording, Ramona Günther, Emilia Vigolo, Christian Tscheik, Lars Winkler, Isabella Schlattner, Dorothea Lorenz, Reiner F Haseloff, Kai M Schmidt-Ott, Hartwig Wolburg, Ingolf E Blasig
• Journal: Antioxidants & redox signaling (Antioxid Redox Signal) Vol. 23 Issue 13 Pg. 1035-49 (Nov 01 2015) ISSN: 1557-7716 [Electronic] United States
• PMID: 25919114 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• MARVEL Domain Containing 2 Protein
• Marveld2 protein, mouse
• Occludin
• Ocln protein, mouse
• Cysteine

Topics

• Animals
• Binding Sites
• Cell Hypoxia
• Cell Membrane Permeability
• Cysteine (metabolism)
• Dogs
• Epithelial Cells (physiology)
• HEK293 Cells
• Humans
• Ischemia (metabolism, pathology)
• Kidney (blood supply, metabolism, pathology)
• MARVEL Domain Containing 2 Protein (chemistry, metabolism)
• Madin Darby Canine Kidney Cells
• Male
• Mice, Inbred C57BL
• Occludin (metabolism)
• Oxidation-Reduction
• Oxidative Stress
• Protein Folding
• Protein Interaction Domains and Motifs
• Protein Transport
• Tight Junctions (metabolism)