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.
","abstract_html":"<p>The Ca<sup>2+</sup>-activated potassium channels K<sub>Ca</sub> channels are a unique family of potassium channels activated by intracellular calcium. K<sub>Ca </sub>channels are critical for maintaining K<sup>+</sup> homeostasis and modulate several physiological processes, from the firing properties of neurons to the control of the transmitter release. The Ca<sup>2+</sup> sensitivity of these channels allows intracellular Ca<sup>2+</sup> to regulate the electrical activity of the cell membrane. Increased Ca<sup>2+</sup> sensitivity of K<sub>Ca </sub>channels 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<sub>Ca</sub>2.3/K<sub>Ca</sub>3.1 channels on human health has not been well documented. In this dissertation, I used inside-out patch clamp recordings to measure the apparent Ca<sup>2+</sup> sensitivity of K<sub>Ca</sub>2.3 and K<sub>Ca</sub>3.1 heterologously expressed in HEK293 cells. Wild-type K<sub>Ca</sub>2.3 channels have a Ca<sup>2+</sup> EC<sub>50</sub> value of ∼0.3 μM, while the apparent Ca<sup>2+</sup> sensitivity of wild-type K<sub>Ca</sub>3.1 channels is ∼0.27 μM. The equivalent mutations related to the ZLS and INCPH in the S<sub>45</sub>A/S<sub>45</sub>B helices increased the apparent Ca<sup>2+</sup> sensitivity of both K<sub>Ca</sub>2.3 & K<sub>Ca</sub>3.1 channel subtypes. However, the equivalent mutations related to the HX in HA/HB helices of K<sub>Ca</sub>2.3 and K<sub>Ca</sub>3.1 affected their apparent Ca<sup>2+</sup> sensitivity differently. AP14145 reduced the apparent Ca<sup>2+ </sup>sensitivity of the hypersensitive mutant K<sub>Ca</sub>2.3 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>","abstract_has_math":false,"creators":["Orfali, Razan"],"institution":null,"degree_name":"Doctor of Philosophy (PhD)","degree_level":"Dissertation","degree_discipline":"Pharmaceutical Sciences","degree_department":null,"school":null,"contributors":["Miao Zhang, Ph.D., Chair","Kamaljit Kaur, Ph.D.","Meng Cui, Ph.D.","Sun Yang, Ph.D."],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2023,"date_issued":"2023-05-01T07:00:00Z","date_published":"2023-05-01T07:00:00Z","updated_at":"2026-07-24T01:38:31Z","subjects":["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"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://digitalcommons.chapman.edu/pharmaceutical_sciences_dissertations/26","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Miao Zhang, Ph.D., Chair","Kamaljit Kaur, Ph.D.","Meng Cui, Ph.D.","Sun Yang, Ph.D."]},{"key":"dc:creator","label":"Author","values":["Orfali, Razan"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"thesis:degree_discipline","label":"Discipline","values":["Pharmaceutical Sciences"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Doctor of Philosophy (PhD)"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["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"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://digitalcommons.chapman.edu/pharmaceutical_sciences_dissertations/26"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["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.
"]},{"key":"dc:source","label":"Dc Source","values":["Orfali, RS. Genetic Mutations of KCa2.3 and KCa3.1 Channels Affect Ca2+ Sensitivity. [dissertation]. Irvine, CA: Chapman University; 2023. https://doi.org/10.36837/chapman.000489"]},{"key":"dc:title","label":"Title","values":["Genetic Mutations of KCa2.3 and KCa3.1 Channels Affect Ca2+ Sensitivity"]}]}],"canonical_facts":{"dc:contributor":["Miao Zhang, Ph.D., Chair","Kamaljit Kaur, Ph.D.","Meng Cui, Ph.D.","Sun Yang, Ph.D."],"dc:creator":["Orfali, Razan"],"dc:description.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.
"],"dc:identifier":["https://digitalcommons.chapman.edu/pharmaceutical_sciences_dissertations/26"],"dc:source":["Orfali, RS. Genetic Mutations of KCa2.3 and KCa3.1 Channels Affect Ca2+ Sensitivity. [dissertation]. Irvine, CA: Chapman University; 2023. https://doi.org/10.36837/chapman.000489"],"dc:subject":["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"],"dc:title":["Genetic Mutations of KCa2.3 and KCa3.1 Channels Affect Ca2+ Sensitivity"],"thesis:degree_discipline":["Pharmaceutical Sciences"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Doctor of Philosophy (PhD)"]},"updated_at":"2026-07-24T01:38:31Z"}