title: Role of C-terminal regions of the C-terminal fragment of Clostridium perfringens enterotoxin in its interaction with claudin-4.
abstract: Claudin family proteins, which contain 4 transmembrane domains, play a pivotal role in the barrier function of tight junctions (TJs) in epithelial sheets. We previously found that a modulator of claudin-4, the C-terminal fragment of Clostridium perfringens enterotoxin (C-CPE), is a potent enhancer of jejunal drug absorption in rats. But the effects of C-CPE on the barrier function of TJs have never been fully understood. In the present study, we investigated the effects of C-CPE on the barrier function of TJs in Caco-2 monolayer and characterized the functional domain of C-CPE that is responsible for interaction with claudin-4. To evaluate the effects of C-CPE on the barrier function of TJs, we measured transepithelial electric resistance (TER) in Caco-2 monolayer cells seeded onto polycarbonate filters. Treatment of Caco-2 cells with C-CPE resulted in a decrease in TER. But, deletion of the 30 C-terminal amino acids of C-CPE, which is the putative binding domain for claudin, attenuated the decrease in TER values. Moreover, ablation of the 16 C-terminal amino acids of C-CPE also resulted in attenuation of the decrease in TER values. The C-terminal-deleted C-CPEs did not interact with claudin-4 or the extracellular domain 2 of claudin-4, which is the C-CPE binding site. These results suggest that the 16 C-terminal amino acids of C-CPE are responsible for the interaction of C-CPE and claudin-4 following the disruption of TJ barrier function.
authors.affiliation: Department of Pharmaceutics and Biopharmaceutics, Showa Pharmaceutical University, Machida, Tokyo 194-8543, Japan.
authors.forename: Azusa
authors.initials: A
authors.lastname: Takahashi
authors.forename: Masuo
authors.initials: M
authors.lastname: Kondoh
authors.forename: Akane
authors.initials: A
authors.lastname: Masuyama
authors.forename: Makiko
authors.initials: M
authors.lastname: Fujii
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Mizuguchi
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Horiguchi
authors.forename: Yoshiteru
authors.initials: Y
authors.lastname: Watanabe
mesh_terms: D018938:Caco-2 Cells; D062506:Claudin-4; D003001:Cloning, Molecular; D004768:Enterotoxins / Q000494:pharmacology*; D004926:Escherichia coli / Q000235:genetics; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010446:Peptide Fragments / Q000494:pharmacology*; D011485:Protein Binding; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D019108:Tight Junctions / Q000187:drug effects* / Q000378:metabolism
chemical_list: C568157:CLDN4 protein, human; D062506:Claudin-4; D004768:Enterotoxins; D008565:Membrane Proteins; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; C035598:enterotoxin, Clostridium