KCNE peptides are a class of type I transmembrane ß-subunits that assemble with and modulate the gating and ion conducting properties of a variety of voltage-gated K+ channels. Accordingly, mutations that affect the assembly and trafficking of K+ channel/KCNE complexes give rise to disease. The cellular mechanisms that oversee KCNE peptide assembly with voltage-gated K+ channels have yet to be elucidated. In Chapter II, we show that KCNE1 peptides are retained in the early stages of the secretory pathway until they co-assemble with KCNQ1 K+ channel subunits. Co-assembly with KCNQ1 channel subunits mediates efficient forward trafficking of KCNE1 peptides through the biosynthetic pathway and results in cell surface expression.
KCNE1 peptides possess two N-linked glycosylation sites on their extracellular N-termini. Progression of KCNE1 peptides through the secretory pathway can be visualized through maturation of N-glycans attached to KCNE1. In Chapter III, we examine the kinetics and efficiency of N-linked glycan addition to KCNE1 peptides. Mutations that prevent glycosylation of KCNE1 give rise to the disorders of arrhythmia and deafness. We show that KCNE1 acquires N-glycans co- and post-translationally. Mutations that prevent N-glycosylation at the co-translational site have a long range effect on the disruption of post-translational glycosylation and suggest a novel biogenic mechanism for disease.
In Chapter IV, we determine the presence of an additional post-translational modification on KCNE1 peptides. We define specific residues as sites of attachment of this modification identified as sialylated O-glycans and show that it occurs in native cardiac tissues where KCNE1 plays a role in the maintenance of cardiac rhythm.
Taken together, these observations demonstrate the importance of having correctly assembled K+ channel/KCNE complexes at the cell surface for their proper physiological function and define a role for the posttranslational modifications of KCNE peptides in the proper assembly and trafficking of K+ channel/KCNE complexes.
| Identifer | oai:union.ndltd.org:umassmed.edu/oai:escholarship.umassmed.edu:gsbs_diss-1487 |
| Date | 07 May 2010 |
| Creators | Chandrasekhar, Kshama D. |
| Publisher | eScholarship@UMassChan |
| Source Sets | University of Massachusetts Medical School |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Morningside Graduate School of Biomedical Sciences Dissertations and Theses |
| Rights | Copyright is held by the author, with all rights reserved., select |
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