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Trafficking and Quality Control of Inward-Rectifying Potassium Channels in the Model Eukaryote Saccharomyces cerevisiae

Mackie, Timothy (2018) Trafficking and Quality Control of Inward-Rectifying Potassium Channels in the Model Eukaryote Saccharomyces cerevisiae. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Humans express 15 different inward-rectifying potassium (Kir) channels that play a variety of roles in epithelial transport, nerve conduction, and muscle contraction. Polymorphisms in Kir channels underlie numerous genetic diseases. In order to investigate the function and regulation of Kir channels, researchers have long recognized the potential of expressing them in strains of Saccharomyces cerevisiae (Bakers’ yeast) engineered for sensitivity to growth in a low potassium medium. These studies capitalize on the wide variety of genetic and biochemical tools available in yeast, namely the ease of transforming large quantities of cells with recombinant DNA and the availability of comprehensive mutant libraries for high-throughput screening. Due to the longstanding popularity of yeast as model eukaryotes, the mechanisms underlying cellular phenomena are relatively well-documented and are also conserved in multicellular organisms. In this document, I will first review the history and diversity of techniques for studying potassium channels in potassium-sensitized yeast. Next, I will describe the results of a genetic screen to identify the key regulatory factors for a particular Kir channel: the renal outer medullary potassium (ROMK) channel. ROMK, also known as Kir1.1, is the major route for potassium secretion into the pro-urine and plays an indispensable role in regulating serum potassium. However, the cellular machinery that regulates ROMK trafficking has not been fully defined. I used a synthetic genetic array to identify nonessential genes that reduce the plasma membrane pool of ROMK in potassium uptake-deficient yeast. Through this screen, I identified several members of the endosomal complexes required for transport (ESCRT) and the class-C core vacuole/endosome tethering (CORVET) complexes. Moreover, silencing of ESCRT and CORVET components increased ROMK levels at the plasma membrane in a mammalian cell line, therefore establishing that post-endocytic sorting influences the cell-surface density of ROMK and modulates its activity. Finally, I will briefly delineate potential future studies in yeast with ROMK and other Kir channels and will describe several investigations into various aspects of Kir channel biology to which I have contributed through collaboration.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Mackie, Timothytdm29@pitt.edutdm29
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairBrodsky, Jeffrey L.jbrodsky@pitt.edujbrodsky
Committee MemberArndt, Karen M.arndt@pitt.eduarndt
Committee MemberHildebrand, Jeffrey D.jeffh@pitt.edujeffh
Committee MemberSubramanya, Arohan R.ars129@pitt.eduars129
Committee MemberVanDemark, Andrew P.andyv@pitt.eduandyv
Date: 27 September 2018
Date Type: Publication
Defense Date: 18 April 2018
Approval Date: 27 September 2018
Submission Date: 7 May 2018
Access Restriction: 1 year -- Restrict access to University of Pittsburgh for a period of 1 year.
Number of Pages: 171
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Biological Sciences
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: ROMK, channel, potassium, trafficking, protein quality control
Date Deposited: 27 Sep 2018 19:50
Last Modified: 27 Sep 2019 05:15


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