Date of Award
8-14-2024
Degree Name
Doctor of Philosophy (PhD)
Degree Type
Dissertation
Abstract
Ion channels are found in all domains of life and play fundamental roles in cellular signaling and response to environmental cues. The ability to accommodate the selective and rapid passage of ions across a cell membrane is conferrable by a myriad of protein folds with no singular one-size-fits-all approach. With the advent of the cryo-EM resolution revolution, substantial interest has developed for determining the molecular structures of conformational states that correspond to conductive and nonconductive forms of ion channels. By gaining insight into the structural mechanisms for ion channel gating, we can potentially reveal binding pockets for targeted small molecule therapeutics that would influence their activity. Here, I report a structural analysis of the open conformations of three diverse ion channels: EcMscK, hTRPV4, and hHCN1. First, I utilize an engineered gain-of-function mutation to reveal the gating mechanism of Escherichia coli MscK—a heptameric dome-shaped bacterial ion channel with 77 transmembrane helices that opens through flattening-and-expansion of its bent transmembrane domain. Next, I investigate the structural basis for RhoA-independent activation of the human TRPV4 channel by leveraging point mutations that enhance its sensitivity to the agonist 2-APB. Finally, I report cryo-EM structures of Closed, Intermediate and Open conformations of hHCN1 that shed light on the molecular mechanisms underpinning its electromechanical coupling. Leveraging single-particle cryo-EM, electrophysiology, and functional assays, I have obtained and characterized structural snapshots for putative open conformations of these three diverse ion channels that provide critical insights into their gating mechanisms and reveal unexpected commonalities between them.
Language
English (en)
Chair and Committee
Colin Nichols
Committee Members
Peng Yuan; Baron Chanda; Hongzhen Hu; Janice Robertson; Timothy Lohman
Recommended Citation
Mount, Jonathan, "Insights from open conformations of EcMscK, hTRPV4, and hHCN1 into the structural basis of ligand-regulated ion channel gating" (2024). Arts & Sciences Electronic Theses and Dissertations. 3313.
https://openscholarship.wustl.edu/art_sci_etds/3313