Effects of TAMP family on the tight junction strand network and barrier function in epithelial cells

• Published in: Annals of the New York Academy of Sciences Vol. 1517; no. 1; pp. 234 - 250
• Main Authors: Saito, Akira C., Endo, Chisato, Fukazawa, Yugo, Higashi, Tomohito, Chiba, Hideki
• Format: Journal Article
• Language: English
• Published: New York Wiley Subscription Services, Inc 01.11.2022
• Subjects: Complexity; Cytology; Epithelial cells; Epithelium; marvelD3; Mathematical models; Morphology; occludin; Structure-function relationships; TAMP; tight junctions; Tightness; TJ strand; tricellulin
• ISSN: 0077-8923; 1749-6632; 1749-6632
• DOI: 10.1111/nyas.14889

Occludin, tricellulin, and marvelD3 belong to the tight junction (TJ)‐associated MARVEL protein family. Occludin and tricellulin jointly contribute to TJ strand branching point formation and epithelial barrier maintenance. However, whether marvelD3 has the same function remains unclear. Furthermore, the roles of the carboxy‐terminal cytoplasmic tail, which is conserved in occludin and tricellulin, on the regulation of TJ strand morphology have not yet been explored in epithelial cells. We established tricellulin/occludin/marveld3 triple‐gene knockout (tKO) MDCK II cells and evaluated the roles of marvelD3 in the TJ strand structure and barrier function using MDCK II cells and a mathematical model. The complexity of TJ strand networks and paracellular barrier did not change in tKO cells compared to that in tricellulin/occludin double‐gene knockout (dKO) cells. Exogenous marvelD3 expression in dKO cells did not increase the complexity of TJ strand networks and epithelial barrier tightness. The expression of the carboxy‐terminal truncation mutant of tricellulin restored the barrier function in the dKO cells, whereas occludin lacking the carboxy‐terminal cytoplasmic tail was not expressed on the plasma membrane. These data suggest that marvelD3 does not affect the morphology of TJ strands and barrier function in MDCK II cells and that the carboxy‐terminal cytoplasmic tail of tricellulin is dispensable for barrier improvement. We have elucidated whether individual TAMP proteins are required for the regulation of tight junction (TJ) strand network complexity, and the necessity of their domains. These results provide a basis for a better understanding of the molecular mechanisms underlying the construction of ultrastructures in TJ.