The Cyclic Nucleotide Binding Domain (CNBD) is conserved in a number of ion channels that belong to three distinct families, the Ether-A-Go-go (EAG); the Cyclic Nucleotide Gated (CNG) and the Hyperpolarization activated Cyclic Nucleotide modulated (HCN) channel families. Extensive biophysical characterizations have established that the function of these channels is directly modulated by cyclic nucleotides in a manner independent of kinase activity and channel phosphorylation. However, the role for this domain in the EAG family is unclear. In addition, although the biophysical properties of CNBD-containing channels are well understood, little is known about the biogenesis of these channels. The original goal of this thesis was to identify trafficking signals in the C-terminus of the Human Ether-a-go-go Related Gene (HERG) potassium channel with the aim of understanding the underlying mechanisms associated with mutations in this gene that cause the Long Q-T Syndrome (LQTS) and associated cardiac arrhythmia. By exploiting the unique biochemical properties of HERG, we identify a discrete C-terminal segment between residues 860-899 that is critical for the exit of the ion channel from the Endoplasmic Reticulum (ER). To substantiate the role of residues 860-899 in trafficking of HERG, we show defective biogenesis associated with a number of LQTS-causing mutations that interfere with this segment. Subsequent functional, biochemical and immunolocalization experiments identify the CNBD of HERG as the trafficking critical segment. Deletions of any of the structural motifs of the CNBD cause retention of the ion channel inside the ER. Likewise, removal of the entire CNBD prevents Golgi transit and cell surface localization of tetrameric channels. We show that all known arrhythmogenic mutations in this domain render HERG channel nonfunctional as a result of ER retention. Subsequent analyses indicate that the CNBD is indispensable for ER exit of a relat
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.84980 |
| Date | January 2004 |
| Creators | Akhavan, Armin |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Physiology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 002166465, proquestno: AAINR06265, Theses scanned by UMI/ProQuest. |
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