Molecular dynamics analyses of CLDN15 pore size and charge selectivity

Abstract

ABSTRACTThe Claudin-15 (CLDN15) channel is important for nutrient, electrolyte, and water transport in the gastrointestinal tract. We used cell culture studies and molecular dynamics simulations to elucidate its structure and permeability mechanisms. We provide a model that underscores the crucial role of the D55 residue in the CLDN15 selectivity filter, which interacts with permeating cations. Our studies demonstrated the mechanisms whereby the size and charge of the D55 residue influence paracellular permeability. By altering D55 to larger, negatively charged glutamic acid (E) or similarly sized neutral asparagine (N), we observed changes in pore size and selectivity, respectively. D55E mutation decreased pore size, favoring small ion permeability without affecting charge selectivity, while D55N mutation led to reduced charge selectivity without markedly altering size selectivity. These findings shed light on the complex interplay of size and charge selectivity of CLDN15 channels. This knowledge can inform the development of strategies to modulate the function of CLDN15 and similar channels, which has implications for tight junction modulation in health and disease.SUMMARYUsing cell culture and molecular dynamics simulations, we have clarified the role of amino acid D55 in the claudin-15 channel function. D55 is important for channel permeability and selectivity in both charge- and size-selective manners. This insight into the structural determinant of claudin cation channel function provides potential insight for designing approaches to alter the claudin channel function to benefit human health.