title: Molecular Architecture of the Blood Brain Barrier Tight Junction Proteins--A Synergistic Computational and In Vitro Approach.
abstract: The blood-brain barrier (BBB) constituted by claudin-5 tight junctions is critical in maintaining the homeostasis of the central nervous system, but this highly selective molecular interface is an impediment for therapeutic interventions in neurodegenerative and neurological diseases. Therapeutic strategies that can exploit the paracellular transport remain elusive due to lack of molecular insights of the tight junction assembly. This study focuses on analyzing the membrane driven cis interactions of claudin-5 proteins in the formation of the BBB tight junctions. We have adopted a synergistic approach employing in silico multiscale dynamics and in vitro cross-linking experiments to study the claudin-5 interactions. Long time scale simulations of claudin-5 monomers, in seven different lipid compositions, show formation of cis dimers that subsequently aggregate into strands. In vitro formaldehyde cross-linking studies also conclusively show that cis-interacting claudin-5 dimers cross-link with short methylene spacers. Using this synergistic approach, we have identified five unique dimer interfaces in our simulations that correlate with the cross-linking experiments, four of which are mediated by transmembrane (TM) helices and the other mediated by extracellular loops (ECL). Potential of mean force calculations of these five dimers revealed that the TM mediated interfaces, which can have distinctive leucine zipper interactions in some cases, are more stable than the ECL mediated interface. Additionally, simulations show that claudin-5 dimerization is significantly influenced by the lipid microenvironment. This study captures the fundamental interactions responsible for the BBB tight junction assembly and offers a framework for extending this work to other tight junctions found in the body.
authors.affiliation: Department of Biomedical and Chemical Engineering, Syracuse University , Syracuse New York 13244, United States.
authors.forename: Flaviyan Jerome
authors.initials: FJ
authors.lastname: Irudayanathan
authors.affiliation: Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute , Troy, New York 12180, United States.
authors.forename: John P
authors.initials: JP
authors.lastname: Trasatti
authors.affiliation: Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute , Troy, New York 12180, United States.
authors.forename: Pankaj
authors.initials: P
authors.lastname: Karande
authors.affiliation: Department of Biomedical and Chemical Engineering, Syracuse University , Syracuse New York 13244, United States.
authors.forename: Shikha
authors.initials: S
authors.lastname: Nangia
mesh_terms: D001812:Blood-Brain Barrier / Q000737:chemistry*; D062507:Claudin-5 / Q000737:chemistry*; D019295:Computational Biology; D003432:Cross-Linking Reagents / Q000737:chemistry; D019281:Dimerization; D005557:Formaldehyde / Q000737:chemistry; D006367:HeLa Cells; D006801:Humans; D056004:Molecular Dynamics Simulation; D019108:Tight Junctions / Q000737:chemistry*; D014407:Tumor Cells, Cultured
chemical_list: D062507:Claudin-5; D003432:Cross-Linking Reagents; D005557:Formaldehyde