The cardiac rapidly activating delayed rectifier potassium channel (IKr) is encoded by the human ether-a-go-go related gene (hERG), which is important for repolarization of the cardiac action potential. Reduction in hERG expression levels due to genetic mutations or drugs causes Long QT Syndrome (LQTS). Recently, we demonstrated that ubiquitination of hERG channels is involved in low K+ induced hERG endocytic degradation. Since homeostatic degradation is an important pathway in maintaining hERG membrane expression levels, we investigated the molecular mechanisms for hERG degradation by focusing on the role and consequence of overexpressing the ubiquitin (Ub) ligase, Nedd4-2 (Neural Precursor Cell- Expressed Developmentally Downregulated Gene 4- 2) (Yang & Kumar, 2010). Previous work in the lab demonstrated that Ub plays a role in the internalization of cell-surface hERG channels, and I hypothesized that ubiquitination of hERG channels is facilitated through Nedd4-2. To study the effects of Nedd4-2 on hERG channels, I overexpressed Nedd4-2 in human embryonic kidney (HEK) 293 cells that stably express the hERG channels. Electrophysiological recordings, Western blot, co-immunoprecipitation analysis, and confocal microscopy were performed to identify Nedd4-2’s role in hERG expression. The data from whole-cell patch clamp recordings demonstrated that, among hEAG, Kv1.5 and hERG, Nedd4-2 specifically eliminates the hERG channel current. Western blot and confocal imaging analyses showed that Nedd4-2 overexpression led to a significant reduction in mature hERG channels in the plasma membrane. Data obtained using co-immunoprecipitation indicated that Nedd4-2 significantly increases ubiquitinated hERG channels. These data indicate that Nedd4-2 may play a role in hERG homeostatic degradation. / Thesis (Master, Physiology) -- Queen's University, 2011-08-15 18:17:00.452
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:OKQ.1974/6649 |
| Date | 15 August 2011 |
| Creators | SHALLOW, HEIDI |
| Contributors | Queen's University (Kingston, Ont.). Theses (Queen's University (Kingston, Ont.)) |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English, English |
| Detected Language | English |
| Type | Thesis |
| Rights | This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner. |
| Relation | Canadian theses |
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