Computational Modeling of Claudin-15 Paracellular Channels

Tight junctions (TJs) regulate paracellular permeability in epithelial tissues through claudin protein assemblies, yet the molecular basis of strand flexibility, pore architecture, and ion selectivity for cation-selective claudin-15 (Cldn-15) remains incompletely defined at atomic resolution. This dissertation employs molecular dynamics (MD) simulations, reduced computational modeling, and cryo-electron tomography (cryo-ET) to address these gaps. Atomistic MD simulations of Cldn-15 strands in opposing plasma membranes demonstrated that lateral flexibility emerges from multiple modular cis interfaces, permitting curvature and branching while maintaining barrier integrity. A validated reduced pore model enabled extensive simulations across ionic conditions and voltages, establishing that octameric pores form via overlapping tetramers. Residue D55 functions as the core electrostatic selectivity filter for cations, with pore geometry modulating the passage of partially dehydrated cations through the pore. Targeted mutagenesis further confirmed these mechanisms and revealed how pore-lining residues such as D64 and E46 maintain ion selectivity. Cryo-ET provided the first in situ 3D visualization of linearly arranged Cldn-15 pores in bending TJ strands, corroborating the computational octameric model. These findings integrate strand mechanics, pore assembly, and selective transport into a unified structural framework, refining claudin polymerization models and paracellular transport principles. The reduced model introduces a scalable methodology for claudin isoform investigations, bridging atomistic and physiological scales. Limitations include constraints on timescale for MD simulations and resolution for cryo-ET imaging. Future work targets selectivity properties of other claudin isoforms, alongside heterotypic strand dynamics. This multiscale approach elucidates how nanoscale claudin organization governs epithelial barrier function, laying the groundwork for therapeutic modulation of TJ permeability in barrier dysfunction diseases.

Author dc:creator

• Sarah McGuinness (24399449)

• Engineering
• Biomedical

Statement dc:rights

• In Copyright

DOI dc:identifier

https://doi.org/10.25417/uic.32993879.v1

OAI identifier oai:identifier

oai:figshare.com:article/32993879