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Remodeling of tight junction protein zonula occludens (ZO)‐1 by glutamine under glucose deprivation in colorectal cancer cells
Author(s) -
Huang Ching-Ying,
Chen Ji-Kai
Publication year - 2020
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.2020.34.s1.02192
Subject(s) - tight junction , glutamine , cancer cell , occludin , microbiology and biotechnology , chemistry , caco 2 , glucose transporter , biology , cell , biochemistry , cancer , endocrinology , amino acid , insulin , genetics
Malignant cells exhibit significant metabolic alteration in nutrients to meet the energetic and biosynthetic demands. Dual routes of nutrients uptake (blood supply and luminal source) are unique characteristics of the cancerous colonic cells. Recently, several lines of evidence have suggested that glutamine can support primary cancer cell growth and serve as an alternate energy fuel during distant metastasis when available glucose concentrations are limited. Tight junctions are specialized epithelial structures for the cell‐cell adhesion and interaction. Tumor dissociation and subsequent metastasis in the tumor microenvironment may occur due to the tight junction remodeling. The current study aims to investigate the role of glutamine in colorectal cancer cells under glucose deprivation. Human colorectal cancer Caco‐2 cells were grown in the transwells to confluency and cultured in DMEM with various glutamine concentration (0 – 50 mM) in the absence of glucose. Apical administration of glutamine in Caco‐2 cells displayed a dose‐dependent drop of TER at 24 hours with no changes of the apical‐to‐basolateral FITC‐labeled dextran 4000 flux. Immunofluorescence staining of tight junction protein zonula occludens (ZO)‐1 and claudin‐1 showed lateral undulations and punctate of the structure accompanied with enlargement of cellular and nuclear size in Caco‐2 cells treated with glutamine (50 mM). Quantification of undulations and cell size revealed significant changes of tight junctional morphological after glutamine treatment in Caco‐2 cells. Decreased protein levels of ZO‐1, but not claudin‐1, were found in detergent‐insoluble fractions of cell preparation of Western blotting. The decline of TER and alteration of the tight junctional structure was not influencing the cell viability. However, the addition of glutamate, which is the amino acid produced during the first step in glutamine catabolism, has no impact on TER. In conclusion, these results suggested that the enteral administration of glutamine may play a role in the modulation of tight junction dynamics in colorectal cancer cells.