Date of Award

Spring 1-27-2022

Level of Access Assigned by Author

Open-Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Advisor

Michael A Kienzler

Second Committee Member

Matthew P Brichacek

Third Committee Member

William M Gramlich

Additional Committee Members

Carl P Tripp

Joshua B Kelley

Abstract

More than 50% of the drugs that are approved by the FDA target transmembrane proteins, as they are involved in the control of physiological functions in the human body. Despite that, they are less studied than globular proteins because they are embedded in lipid membranes which impedes their experimental characterization. Hence, it is crucial to develop molecular tools and drugs to better understand and control their function. We have worked on the development of target specific photoswitchable molecules to modulate transmembrane proteins in the central nervous system including the serotonin receptors and two-pore domain potassium channels. These photoswitches can be isomerized between their cis and trans conformations to activate and deactivate the ligand.

Serotonin or 5-hydroxytryptamine (5HT) is a monoamine neurotransmitter which is used as a signaling molecule in the body to carry out a diverse set of bodily functions, including anxiety, mood, memory, addiction, appetite, digestion, sleep, and vasoconstriction. There are 18 types of serotonin receptors present in the body; 5 of which are ion channels, the remaining are G-protein coupled receptors (GPCRs). Research in the identification of functions of individual receptors and the development of target specific drugs for each receptor is a topic of active research, but similarities between the binding sites of these receptors make it difficult. Even the few selective drugs that have been developed tend to cause severe side effects since the serotonin receptors are expressed all across the body. We are developing azobenzene-based photoswitches with a serotonin moiety that can help us achieve spatiotemporal control of 5HT receptors.

Two-pore domain potassium (K2P) channels are a family of potassium selective ion channels that contribute to the background potassium leak current in most excitable cells in the human body, helping to restore and maintain a healthy resting membrane potential. Generally, inhibition of K2P channels increases cell excitability whereas potentiation results in dampening the excitability. Our work currently focuses on three of subtypes of K2P channels; TREK, TRESK, and TASK channels, which are of practical interest as therapeutic targets for pain management because they play a key role in perceiving neuropathic pain, inflammatory pain, and migraine. Using the principles of photopharmacology, incorporation of an azobenzene into the structure of ML365 (a known selective potent inhibitor for TASK1 channels), we synthesized and characterized two new photoswitchable light activated potassium channel inhibitors (LAKI). Interestingly, LAKI-1 is selective towards the members of the TREK and TRESK families instead of TASK1. Here we discuss the in-vitro and computational studies performed to elucidate this unexpected interaction.

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