The Protein Kinase A Pathway Contributes to Hg2+-Induced Alterations in Phosphorylation and Subcellular Distribution of Occludin Associated with Increased Tight Junction Permeability of Salivary Epithelial Cell Monolayers
- 12 June 2008
- journal article
- research article
- Published by American Society for Pharmacology & Experimental Therapeutics (ASPET) in The Journal of pharmacology and experimental therapeutics
- Vol. 326 (3), 829-837
- https://doi.org/10.1124/jpet.107.135798
Abstract
Hg2+ is commonly used as an inhibitor of many aquaporins during measurements of transcellular water transport. To investigate whether it could also act on the paracellular water transport pathway, we asked whether addition of Hg2+ affected transport of radiolabeled probes through tight junctions of a salivary epithelial cell monolayer. Inclusion of 1 mM Hg2+ decreased transepithelial electrical resistance by 8-fold and augmented mannitol and raffinose flux by 13-fold, which translated into an estimated 44% increase in pore radius at the tight junction. These Hg2+-induced effects could be partially blocked by the protein kinase A (PKA) inhibitor N-[2-((p-bromocinnamyl) amino) ethyl]-5-isoquinolinesulfonamide, 2HCl (H89), suggesting that both-PKA dependent and PKA-independent mechanisms contribute to tight junction regulation. Western blot analyses showed a 2-fold decrease in tight junction-associated occludin after Hg2+ treatment and the presence of a novel hyperphosphorylated form of occludin in the cytoplasmic fraction. These findings were corroborated by confocal imaging. The results from this study reveal a novel contribution of the PKA pathway in Hg2+-induced regulation of tight junction permeability in the salivary epithelial barrier. Therapeutically, this could be explored for pharmacological intervention in the treatment of dry mouth, Sjögren's syndrome, and possibly other disorders of fluid transport.This publication has 44 references indexed in Scilit:
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