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- Title
Behavior of tricellulin during destruction and formation of tight junctions under various extracellular calcium conditions.
- Authors
Takasawa, Akira; Kojima, Takashi; Ninomiya, Takafumi; Tsujiwaki, Mitsuhiro; Murata, Masaki; Tanaka, Satoshi; Sawada, Norimasa
- Abstract
Tricellulin is an important component of tricellular tight junctions (TJs) and is involved in the formation of tricellular contacts. However, little is known about its regulation during the assembly and disassembly of tricellular TJs. By using the well-differentiated pancreatic cancer cell line HPAC, which highly expresses tricellulin at tricellular contacts, we have investigated changes in the localization, expression and phosphorylation of tricellulin and in its TJ functions as a barrier and fence during the destruction and formation of TJs induced by changes in the extracellular calcium concentration. During both extracellular Ca depletion caused by EGTA treatment and Ca repletion after Ca starvation, the expression of tricellulin increased in whole lysates and in Triton-X-100-insoluble fractions without any change in its mRNA. The increases in immunoreactivity revealed by Western blotting were prevented by alkaline phosphatase treatment. Immunoprecipitation assays showed that tricellulin was phosphorylated on threonine residues when it increased after Ca depletion and repletion. In the early stage after Ca repletion, tricellulin was expressed not only at tricellular contacts but also in the cytoplasm and at bicellular borders. In confocal laser microscopy, tricellulin was observed at the apical-most regions and basolateral membranes of tricellular contacts after Ca repletion. Knockdown of tricellulin delayed the recovery of the barrier and fence functions after Ca repletion. Thus, the dynamic behavior of tricellulin during the destruction and formation of TJs under various extracellular calcium conditions seems to be closely associated with the barrier and fence functions of TJs.
- Subjects
TIGHT junctions; CELLULIN; EXTRACELLULAR space; CALCIUM in the body; CELL differentiation; PANCREATIC cancer; CANCER cells; GENE expression
- Publication
Cell & Tissue Research, 2013, Vol 351, Issue 1, p73
- ISSN
0302-766X
- Publication type
Article
- DOI
10.1007/s00441-012-1512-7