MA026, an anti-hepatitis C virus compound, opens tight junctions of the epithelial cell membrane

Abstract

MA026 is an antiviral natural compound against hepatitis C virus (HCV). It was recently reported that MA026 binds claudin-1 (CLDN1) and inhibits HCV infection. Although CLDN1 is an important component of tight junctions (TJ) in the epithelial cell layer, the effects of MA026 on the TJ barrier function remained to be revealed. Here we report that MA026 irreversibly opens the TJ. MA026 irreversibly increased FD4 permeability and decreased transepithelial electrical resistance (TER) for at least 5 h. Although MA026 increased Ca 2+ influx in layered MDCKII cells, the Ca 2+ influx was less than that of capsaicin, a reversible TJ opener. Moreover, MA026 did not induce the dephosphorylation of cofilin and reorganization of F-actin structure. Although the mechanism is left to be disclosed, these results suggest that MA026 is a novel irreversible TJ opener probably by targeting CLDN1.

Structural Revision of Natural Cyclic Depsipeptide MA026 Established by Total Synthesis and Biosynthetic Gene Cluster Analysis

“…Finally, we evaluated the TJ opening activity of revised MA026 (2) with transport assay using FD4 (FITC-dextran 4 kDa). [10,13] In this assay, the fluorescence intensity from FITC is measured in the transmembrane part and recognized as the TJ opening activity. As shown in Figure 5, revised MA026 (2) efficiently transports FD4 similarly to natural MA026, but the reported MA026 (1) and its epimer at C3 position of N-terminal acyl tail (1' in the Supporting Information, Figures S5 and S14) failed to do so.…”

“…Finally, we evaluated the TJ opening activity of revised MA026 ( 2 ) with transport assay using FD4 (FITC‐dextran 4 kDa) [10, 13] . In this assay, the fluorescence intensity from FITC is measured in the transmembrane part and recognized as the TJ opening activity.…”

“…A total solution-phase synthesis of MA026 and analysis of its anti-hepatitis C viral activity by binding to the TJ membrane protein claudin-1 were reported in 2013 by Shimura et al [9] Kanda et al reported in 2017 that natural MA026 has a tight junction (TJ) opening activity. [10] The TJ is a continuous intercellular barrier between epithelial cells that separates the internal and external environments of cellular sheets, and controls invasion of foreign substances and a diffusion of solutes and water across the epithelium. [11] The TJ is composed of a multi-protein complex including several transmembrane proteins, such as claudins, occludin and several junctional adhesion molecules.…”

X-Ray Conformation and Structure–Activity Relationships of MA026, a Reversible Tight Junction Opener

“…6 Moreover, it has been reported that MA026 opens the TJ and causes increased permeability of the epithelial barrier. 17 Recently, we also demonstrated that the previously reported structure of MA026 is different from the natural structure, and as a result, two amino acid residues were revised. 18 When MA026 was synthesized based on the revised structure, it showed TJopening activity comparable to that of the natural product, although the detailed mechanism of action has remained to be clarified.…”

“…Claudin-1 is a protein belonging to the claudin family and plays an important role in the tight junction barrier of epithelial cells . Moreover, it has been reported that MA026 opens the TJ and causes increased permeability of the epithelial barrier . Recently, we also demonstrated that the previously reported structure of MA026 is different from the natural structure, and as a result, two amino acid residues were revised .…”