Identification of Accessory Proteins and Their Impact on the Expression of the Epithelial Sodium Channel (ENaC)
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The epithelial sodium channel (ENaC) plays a crucial role in ensuring proper Na+ balance in the body. In the nephron, ENaC regulates the final 3-5% reabsorption of Na+ and is a limiting factor for Na+ reabsorption in the kidneys. Because of its role in the kidneys, ENaC is thought to be a critical component in the control of blood pressure. Though there have been several accessory proteins known to regulate ENaC function, there are still questions to be answered about the role other proteins play in ENaC trafficking and assembly. Understanding the mechanisms behind ENaC regulation will potentially provide insight into certain defects in the trafficking or assembly of the channel, and identify possible therapeutic targets. Through survival dilution growth assays in yeast deletion strains, several genes were shown to effect ENaC function in a high salt growth media. A yeast deletion strain expressing α-ENaC but lacking ER degradation enhancing alpha-mannosidase like protein 3 (EDEM3) showed an increase in the growth of yeast cells compared to wildtype. Similarly, a yeast deletion strain lacking nuclear protein localization 4 (NPL4) showed an increase in the growth of yeast cells compared to wildtype. The lack of growth inhibition may indicate a possible loss in ENaC function. A Syntaxin 3 yeast deletion strain expressing αENaC resulted in decreased cell growth indicating a possible gain in ENaC function. Western blot and real time PCR analysis on the knockdowns of EDEM3, Syntaxin 3, and NPL4 using a CRISPR/Cas9 knockout plasmid in a Mpkccd mammalian cell line endogenously expressing αβγ ENaC, demonstrated a decrease of ENaC protein expression levels.