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Temporal Control of Ion Channel Activation


Shafaat, Oliver Syed (2016) Temporal Control of Ion Channel Activation. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Z98P5XGX.


Ion channels are a large class of integral membrane proteins that allow for the diffusion of ions across a cellular membrane and are found in all forms of life. Pentameric ligand-gated ion channels (pLGICs) comprise a large family of proteins that include the nicotinic acetylcholine receptor (nAChR) and the γ-aminobutyric acid (GABA) receptor. These ion channels are responsible for the fast synaptic transmission that occurs in humans and as a result are of fundamental biological importance. pLGICs bind ligands (neurotransmitters), and upon ligand-binding undergo activation. The activation event causes an ion channel to enter a new physical state that is able to conduct ions. Ion channels allow for the flux of ions across the membrane through a pore that is formed upon ion channel activation. For pLGICs to function properly both ligand-binding and ion channel activation must occur. The ligand-binding event has been studied extensively over the past few decades, and a detailed mechanism of binding has emerged. During activation the ion channel must undergo structural rearrangements that allow the protein to enter a conformation in which ions can flow through. Despite this great and ubiquitous importance, a fundamental understanding of the ion channel activation mechanism and kinetics, as well as concomitant structural arrangements, remains elusive.

This dissertation describes efforts that have been made to temporally control the activation of ligand-gated ion channels. Temporal control of ion channel activation provides a means by which to activate ion channels when desired. The majority of this work examines the use of light to activate ion channels. Several photocages were examined in this thesis; photocages are molecules that release a ligand under irradiation, and, for the work described here, the released ligand then activates the ion channel. First, a new water-soluble photoacid was developed for the activation of proton-sensitive ion channels. Activation of acid-sensing ion channels, ASIC2a and GLIC, was observed only upon irradiation. Next, a variety of Ru2+ photocages were also developed for the release of amine ligands. The Ru2+ systems interacted in a deleterious manner with a representative subset of biologically essential ion channels. The rapid mixing of ion channels with agonist was also examined. A detection system was built to monitor ion channels activation in the rapid mixing experiments. I have shown that liposomes, and functionally-reconstituted ELIC, are not destroyed during the mixing process. The work presented here provides the means to deliver agonist to ligand-gated ion channels in a controlled fashion.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Ion Channels, Photoactivation, Photocage
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Biochemistry and Molecular Biophysics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Gray, Harry B. (co-advisor)
  • Dougherty, Dennis A. (co-advisor)
Thesis Committee:
  • Rees, Douglas C. (chair)
  • Gray, Harry B.
  • Dougherty, Dennis A.
  • Shan, Shu-ou
  • Winkler, Jay Richmond
Defense Date:6 May 2016
Funding AgencyGrant Number
Arnold and Mabel Beckman FoundationUNSPECIFIED
Record Number:CaltechTHESIS:05122016-095434020
Persistent URL:
Shafaat, Oliver Syed0000-0002-3170-2553
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:9716
Deposited By: Oliver Shafaat
Deposited On:23 May 2016 23:02
Last Modified:04 Oct 2019 00:13

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