Date of Award

4-2023

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Program

Biomedical Sciences

Track

Molecular and Systems Pharmacology

Research Advisor

Alex M. Dopico, MD, PhD

Committee

Anna N. Bukiya, PhD; Kafait U. Malik, PhD; Valeria Vasquez, PhD; Fu-Ming Zhou, PhD

Keywords

BK channels, cholesterol, neurosteroids, potassium channels, pregnenolone, progesterone

Abstract

Voltage-gated and Ca2+ activated K+ channels of large conductance (BK) channels are essential for many key physiological processes, such as controlling the contraction of smooth muscle, including cerebrovascular smooth muscle. Importantly, BK channels are made up of a homotetramer of α subunits which associate with accessory β subunits. These β subunits alter the activity of the channel; this modulation is subunit-specific. Moreover, these accessory subunits have tissue-specific expression, such that the β1 subunit is highly expressed within cerebrovascular smooth muscle and greatly increases the open probability of BK channels. Increased BK channel open probability is linked to increased dilation of cerebral arterial smooth muscle. The tissue specificity and functional effects of the β1 subunit offer a unique opportunity for the identification of pharmacological activators to be developed with few off-target effects. While many steroids have been implicated to have vasoactive effects, including but not limited to, pregnenolone and progesterone, these effects have been mainly attributed to the actions produced by the activation of traditional steroid receptors. Importantly, both pregnenolone and progesterone are currently under investigation for clinical applications, including substance- and alcohol-use disorders, and treatments for ischemic-related brain injury, respectively. Additionally, cholesterol maintains clinical importance as the western diet maintains high levels of cholesterol which are known to increase the risk of heart disease and stroke through maladaptive vasoactive effects. Since the precursor to, and the neurosteroids all produce vasoactive effects, it is important to identify the molecular mediators modulating these effects. This body of work examines the cerebrovascular effects of and determines the mechanisms of action by which the neurosteroids pregnenolone, progesterone, and the precursor cholesterol, modulate the BK channel activity while investigating pre-clinical implications for the K+ channel activators. Through functional, biochemical, and molecular analysis we are able to determine: 1. the physiological implications of; 2. the subunit-specificity for; 3. binding site(s) of; and 4. the gating parameters affected by, the direct binding of neurosteroids to the BK channel complex.

Declaration of Authorship

Declaration of Authorship is included in the supplemental files.

ORCID

https://orcid.org/0000-0002-8745-7892

DOI

10.21007/etd.cghs.2023.0617

Additional Files
2023-004-North-DOA.pdf (189 kB)
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