Journal
EXPERIMENTAL CELL RESEARCH
Volume 314, Issue 14, Pages 2643-2651Publisher
ELSEVIER INC
DOI: 10.1016/j.yexcr.2008.05.015
Keywords
claudin; tight junction; cell-cell adhesion; molecular force spectroscopy; atomic force microscopy; pH
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Funding
- Biomedical Research Council (BMRC)
- Agency for Science, Technology & Research (A'STAR), singapore
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Claudins belong to a large family of transmembrane proteins that localize at tight junctions (TJs) where they play a central role in regulating paracellular transport of solutes and nutrients across epithelial monolayers. Their ability to regulate the paracellular pathway is highly influenced by changes in extracellular pH. However, the effect of changes in pH on the strength and kinetics of claudin mediated adhesion is poorly understood. Using atomic force microscopy, we characterized the kinetic properties of homophilic trans-interactions between full length recombinant CST tagged Claudin-2 (Cldn2) under different pH conditions. In measurements covering three orders of magnitude change in force loading rate of 10(2)-10(4) pN/s, the Cldn2/Cldn2 force spectrum (i.e., unbinding force versus loading rate) revealed a fast and a slow loading regime that characterized a steep inner activation barrier and a wide outer activation barrier throughout pH range of 4.5-8. Comparing to the neutral condition (pH 6.9), differences in the inner energy barriers for the dissociation of Cldn2/Cldn2 mediated interactions at acidic and alkaline environments were found to be <0.65 k(B)T, which is much lower than the outer dissociation energy barrier (>1.37 kBT). The relatively stable interaction of Cldn2/Cldn2 in neutral environment suggests that electrostatic interactions may contribute to the overall adhesion strength of Cldn2 interactions. our results provide an insight into the changes in the inter-molecular forces and adhesion kinetics of Cldn2 mediated interactions in acidic, neutral and alkaline environments. (C) 2008 Elsevier Inc. All rights reserved.
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