Genetic Mutations of K_Ca2.3 and K_Ca3.1 Channels Affect Ca2+ Sensitivity

<p>The Ca²⁺-activated potassium channels K_Ca channels are a unique family of potassium channels activated by intracellular calcium. K_Cachannels 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 K_Cachannels caused by gain of function mutations (GOF) in the <em>KCNN</em> 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 K_Ca2.3/K_Ca3.1 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 K_Ca2.3 and K_Ca3.1 heterologously expressed in HEK293 cells. Wild-type K_Ca2.3 channels have a Ca²⁺ EC₅₀ value of ∼0.3 μM, while the apparent Ca²⁺ sensitivity of wild-type K_Ca3.1 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 K_Ca2.3 & K_Ca3.1 channel subtypes. However, the equivalent mutations related to the HX in HA/HB helices of K_Ca2.3 and K_Ca3.1 affected their apparent Ca²⁺ sensitivity differently. AP14145 reduced the apparent Ca²⁺sensitivity of the hypersensitive mutant K_Ca2.3 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.</p>

Name thesis:degree_name

Doctor of Philosophy (PhD)

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Pharmaceutical Sciences

Year

2023

Author dc:creator

• Orfali, Razan

Contributors dc:contributor

• Miao Zhang, Ph.D., Chair
• Kamaljit Kaur, Ph.D.
• Meng Cui, Ph.D.
• Sun Yang, Ph.D.

• HA/HB helices; K(Ca)2.3 and K(Ca)3.1 channels; Negative gating modulator; S(45)A/S(45)B (helices).
• Medicinal and Pharmaceutical Chemistry
• Other Pharmacy and Pharmaceutical Sciences
• Pharmaceutics and Drug Design

Repository record dc:identifier

https://digitalcommons.chapman.edu/pharmaceutical_sciences_dissertations/26

OAI identifier oai:identifier

oai:digitalcommons.chapman.edu:pharmaceutical_sciences_dissertations-1027