TY - JOUR T1 - Role of N-Terminal Amino Acids in the Absorption-Enhancing Effects of the C-Terminal Fragment of <em>Clostridium perfringens</em> Enterotoxin JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 789 LP - 795 DO - 10.1124/jpet.105.085399 VL - 314 IS - 2 AU - Akane Masuyama AU - Masuo Kondoh AU - Hirotoshi Seguchi AU - Azusa Takahashi AU - Motoki Harada AU - Makiko Fujii AU - Hiroyuki Mizuguchi AU - Yasuhiko Horiguchi AU - Yoshiteru Watanabe Y1 - 2005/08/01 UR - http://jpet.aspetjournals.org/content/314/2/789.abstract N2 - We recently found that a polypeptide, the C-terminal of Clostridium perfringens enterotoxin (C-CPE), was a novel type of drug absorption enhancer. The C-terminal of C-CPE is thought to play a role in the binding of C-CPE to its receptor, claudin-4; however, the function of the N-terminal of C-CPE is unclear. In the present study, we evaluated the role of the N-terminal domain of C-CPE in jejunal absorption and claudin-4 binding. The treatment of rat jejunum with C-CPE resulted in enhanced absorption of dextran, with a molecular weight of 4000 Da. However, treatment with C-CPE220, which lacks the 36 N-terminal amino acids of C-CPE, did not enhance jejunal absorption. C-CPE had affinity for claudin-4 in rat jejunum lysates and Caco-2 lysates, but C-CPE220 did not. Interaction of C-CPE with the recombinant extracellular domain 2 of human claudin-4 (EC2hCld-4), which is the putative binding site for C-CPE, was observed, but C-CPE220 had no affinity for EC2hCld-4. To investigate the effect of C-CPE220 on the barrier function of tight junctions, we measured transepithelial electric resistance (TER) in C-CPE- or C-CPE220-treated Caco-2 monolayer cells. Although C-CPE decreased TER in Caco-2 monolayer cells, C-CPE220 did not disrupt the barrier function of tight junctions. Together, these results indicate that the 36 N-terminal amino acids of C-CPE may be necessary for the enhanced absorption mediated by C-CPE and play a partial role in binding to claudin-4. The American Society for Pharmacology and Experimental Therapeutics ER -