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Trafficking Patterns of KCNQ1 and KCNE1 and Assembly into the Slow Delayed Rectifier (Iks) Channel
Sukhleen Kaur, Depts. of Bioinformatics and Chemistry, with Dr. Gea-Ny Tseng, Dept. of Physiology and Biophysics
KCNQ1 and KCNE1 are both proteins that are essential in maintaining cardiac electrical stability. The assembly of the two units forms the slow delayed rectifier channel (Iks) which plays a role in repolarization of the action potential in adult ventricular myocytes when a shorter action potential is required. Iks remains unassembled under basal conditions as KCNQ1 and KCNE1 are segregated. While KCNQ1 is a pore-forming subunit, KCNE1 is a smaller, auxiliary subunit. The assembly of both subunits is essential in forming Iks, for they do not function when they are present as separate, individual units. In other words, the two units are mutually inclusive, yet they both have very different properties, especially in reference to the trafficking phenomenon of each protein following translation. The question being addressed, therefore, was “how do KCNQ1 and KCNE1 assemble to form Iks channels in COS-7 cells and adult ventricular myocytes?” Confocal imaging experiments were conducted to visualize the movement of fluorescent protein-tagged KCNQ1 and KCNE1 COS-7 cells at fixed time points. The RUSH (retention using selective hooks) construct was utilized to analyze the proteins after they had exited the endoplasmic reticulum (ER). Biotinylation experiments were furthermore conducted in order to quantify cell surface KCNQ1 and KCNE1. Lastly, more imaging experiments were conducted, this time using adenovirus-mediated expression in cardiomyocytes, to address the research question. The results of the experiments showed KCNQ1-GFP traveled largely in the ER network and budded out into vesicles which then fused with the cell membrane. On the other hand, KCNE1-dsRed traveled largely in vesicles throughout the cytoplasm. Through the limited results of the experiments, it was concluded that KCNQ1 and KCNE1 traffic separately and in different manners to the plasma membrane and assemble into the slow-delayed rectifier channel on the cell surface.
Gea-Ny Tseng, Ph.D.
Virginia Commonwealth University. Undergraduate Research Opportunities Program
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