Varying Assay of Proteins Vital to Regulation of the Epithelial Sodium Channel (ENaC)

Abstract

The epithelial sodium channel (ENaC) is a transmembrane heterotrimeric protein complex that transports sodium into epithelial cells. This channel plays a crucial role in sodium regulation, which is important for proper blood pressure and fluid balance. Located in the distal portion of nephrons within the kidney, the channel selectively regulates the reabsorption of sodium. Genetic mutations in ENaC have shown to cause disease states of hypertension in Liddle's syndrome and hypotension in pseudohypoaldosteronism type 1. Prior studies have focused on regulation of ENaC via protein‐protein interactions, such as an ubiquitin‐protein ligase Nedd4‐2, a ubiquitin transferase domain HECT, and serine/threonine‐protein kinases Sgk1, much is still unknown about ENaC. Our studies include expression of ENaC in yeast deletion strains to identify proteins necessary for ENaC function. A serial dilution pronging assay was performed for each separate deletion yeast strain. Results showed that although no tested strains had direct effect on ENaC functionality, the coated vesicle protein COPII, a Rubb1p (NEDD8) activator protein, and a p24 protein component involved in vesicle quality control all had negative effects on cell growth with and without salt present when particular ENaC subunits (β/γ) or all ENaC subunits (α/β/γ) were present. Further analysis of genes encoding proteins associated with ENaC will provide more insight into ENaC and its role in sodium homeostasis.