Date of Award
5-1-2026
Document Type
Dissertation
Degree Name
Ph.D. in Pharmaceutical Sciences
First Advisor
Jing Li
Second Advisor
John M. Rimoldi
Third Advisor
Robert J. Doerksen
School
University of Mississippi
Relational Format
dissertation/thesis
Abstract
Voltage-gated ion channels (VGICs) are core determinants of electrical excitability. Here I investigate how disease-associated mutations in their voltage-sensing domains (VSDs) remodel structure, dynamics, and ion permeation to produce human channelopathies. Using long timescale molecular dynamics simulations, sequence alignment and structural bioinformatics, I show that homologous mutations at conserved electrostatic and aromatic motifs generate domain-specific gating and gating-pore phenotypes in Nav and Kv channels. In the second chapter, I systematically compare R?Q substitutions at three sequential S4 gating charges (R1 R3) in VSD I and II of Nav1.5. VSD-targeted simulations under external fields (~120 ?s total) combined with electrophysiology reveal that nominally equivalent mutations differentially reorganize state-dependent salt-bridge and lipid interaction networks. These domain-specific changes alter VSD transition kinetics, promote distinct patterns of transient aqueous leaks, and modulate gating-pore current during up-to-down transitions. In the third chapter, we examine three Nav1.2 Domain I variants (R220G, R223I, R223Q) associated with divergent neurodevelopmental phenotypes. Electrophysiological recordings demonstrate mutation-specific inward gating-pore currents with distinct voltage dependence and altered activation, inactivation, and recovery, while atomistic simulations link these effects to disrupted cation–? and salt-bridge interactions that stabilize leak-permissive VSD conformations. The the fourth chapter, we generalize these insights across VGIC families by combining large-scale sequence alignments, structural mining of hundreds of cryo-EM and X-ray structures, mutagenesis, electrophysiology, and microsecond simulations. These studies support a unifying model in which evolutionarily conserved cation–? interactions between S4 gating charges and the S2 aromatic at the hydrophobic constriction site act as a primary “gatekeeper” of VSD insulation, with state dependent salt bridges and hydrophobic packing providing additional barriers to pathological gating-pore formation. Overall, this work shows that VSD mutational consequences are determined not simply by sequence position but by local electrostatic topology, aromatic environment, and domain-specific interaction networks. The dissertation provides an atomistic framework that connects individual variants to altered VSD energetics, gating trajectories, and leak pathways, improving mechanistic understanding of Nav- and Kv-mediated channelopathies and informing prediction and targeting of pathogenic VSD mutations.
Recommended Citation
Elhanafy, Eslam, "Molecular and Structural Mechanisms of Disease-Associated Mutations in Voltage-Gated Ion Channels" (2026). Electronic Theses and Dissertations. 8814.
https://egrove.olemiss.edu/etd/8814