Role of Glutamine in Protection of Intestinal Epithelial Tight Junctions

The mechanisms responsible for microbially induced epithelial apoptosis and increased intestinal permeability remain unclear. This study assessed whether purified bacterial lipopolysaccharide (LPS) increases epithelial apoptosis and permeability and whether these changes are dependent on caspase-3 activation. In nontumorigenic epithelial monolayers, Escherichia coli O26:B6 LPS increased apoptosis, as shown by nuclear breakdown, caspase-3 activation, and PARP cleavage, and induced disruption of tight junctional ZO-1. Apical, but not basolateral, exposure to LPS increased epithelial permeability. Addition of a caspase-3 inhibitor abolished the effects of LPS. The findings describe a novel mechanism whereby apical LPS may disrupt epithelial tight junctional ZO-1 and barrier function in a caspase-3-dependent fashion.

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Intestinal epithelial tight junctions and permeability can be rescued through the regulation of endoplasmic reticulum stress by amniotic fluid stem cells during necrotizing enterocolitis

The FASEB Journal ◽

10.1096/fj.202001426r ◽

2020 ◽

Vol 35 (1) ◽

Author(s):

Bo Li ◽

Carol Lee ◽

Sinobol Chuslip ◽

Dorothy Lee ◽

George Biouss ◽

...

Keyword(s):

Stem Cells ◽

Endoplasmic Reticulum ◽

Endoplasmic Reticulum Stress ◽

Amniotic Fluid ◽

Tight Junctions ◽

Necrotizing Enterocolitis ◽

Intestinal Epithelial ◽

Amniotic Fluid Stem Cells ◽

Epithelial Tight Junctions

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Protein kinase Cζ phosphorylates occludin and promotes assembly of epithelial tight junctions

Biochemical Journal ◽

10.1042/bj20110587 ◽

2011 ◽

Vol 437 (2) ◽

pp. 289-299 ◽

Cited By ~ 54

Author(s):

Suneet Jain ◽

Takuya Suzuki ◽

Ankur Seth ◽

Geetha Samak ◽

Radhakrishna Rao

Keyword(s):

Protein Kinase ◽

Tight Junction ◽

Tight Junctions ◽

Intercellular Junctions ◽

Cell Monolayers ◽

Terminal Domain ◽

Tight Junction Regulation ◽

Epithelial Tight Junctions ◽

Zona Occludens

Protein kinases play an important role in the regulation of epithelial tight junctions. In the present study, we investigated the role of PKCζ (protein kinase Cζ) in tight junction regulation in Caco-2 and MDCK (Madin–Darby canine kidney) cell monolayers. Inhibition of PKCζ by a specific PKCζ pseudosubstrate peptide results in redistribution of occludin and ZO-1 (zona occludens 1) from the intercellular junctions and disruption of barrier function without affecting cell viability. Reduced expression of PKCζ by antisense oligonucleotide or shRNA (short hairpin RNA) also results in compromised tight junction integrity. Inhibition or knockdown of PKCζ delays calcium-induced assembly of tight junctions. Tight junction disruption by PKCζ pseudosubstrate is associated with the dephosphorylation of occludin and ZO-1 on serine and threonine residues. PKCζ directly binds to the C-terminal domain of occludin and phosphorylates it on threonine residues. Thr403, Thr404, Thr424 and Thr438 in the occludin C-terminal domain are the predominant sites of PKCζ-dependent phosphorylation. A T424A or T438A mutation in full-length occludin delays its assembly into the tight junctions. Inhibition of PKCζ also induces redistribution of occludin and ZO-1 from the tight junctions and dissociates these proteins from the detergent-insoluble fractions in mouse ileum. The present study demonstrates that PKCζ phosphorylates occludin on specific threonine residues and promotes assembly of epithelial tight junctions.

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