Date of Award

Spring 5-2023

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Pharmaceutical Sciences

First Advisor

Miao Zhang, Ph.D., Chair

Second Advisor

Kamaljit Kaur, Ph.D.

Third Advisor

Meng Cui, Ph.D.

Fourth Advisor

Sun Yang, Ph.D.

Abstract

The Ca2+-activated potassium channels KCa channels are a unique family of potassium channels activated by intracellular calcium. KCa channels are critical for maintaining K+ homeostasis and modulate several physiological processes, from the firing properties of neurons to the control of the transmitter release. The Ca2+ sensitivity of these channels allows intracellular Ca2+ to regulate the electrical activity of the cell membrane. Increased Ca2+ sensitivity of KCa channels caused by gain of function mutations (GOF) in the KCNN genes results in a broad spectrum of human channelopathies, including Zimmermann- Laband syndrome (ZLS), idiopathic non-cirrhotic portal hypertension (INCPH), and hereditary xerocytosis (HX). The impact of dysfunctional KCa2.3/KCa3.1 channels on human health has not been well documented. In this dissertation, I used inside-out patch clamp recordings to measure the apparent Ca2+ sensitivity of KCa2.3 and KCa3.1 heterologously expressed in HEK293 cells. Wild-type KCa2.3 channels have a Ca2+ EC50 value of ∼0.3 μM, while the apparent Ca2+ sensitivity of wild-type KCa3.1 channels is ∼0.27 μM. The equivalent mutations related to the ZLS and INCPH in the S45A/S45B helices increased the apparent Ca2+ sensitivity of both KCa2.3 & KCa3.1 channel subtypes. However, the equivalent mutations related to the HX in HA/HB helices of KCa2.3 and KCa3.1 affected their apparent Ca2+ sensitivity differently. AP14145 reduced the apparent Ca2+ sensitivity of the hypersensitive mutant KCa2.3 channels. The results of my Ph.D. project would suggest the potential therapeutic usefulness of negative gating modulators as a novel target in these channelopathy-causing mutations. At the same time would guide us to design more potent and subtype-selective positive modulators targeting these channels.

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Creative Commons License
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