Derlin-1 promotes ubiquitylation and degradation of the epithelial Na+ channel, ENaC

• DOI: 10.1242/jcs.198242
• Publication Date: 2017-01-31T01:40:33Z
• Authors: Hui You; Yamei Ge; Jian Zhang; Yizhi Cao; Jing Xing; Dongming Su; Yujie Huang; Min Li; Shen Qu; Fei Sun; Xiubin Liang
• Keywords: 0303 health sciences; Lysine; Tumor Suppressor Proteins; Ubiquitin-Protein Ligases; Cell Membrane; Ubiquitination; Membrane Proteins; Models, Biological; Mice; 03 medical and health sciences; HEK293 Cells; Protein Domains; Proteolysis; Animals; Humans; Epithelial Sodium Channels; Polyubiquitin; Protein Binding

ABSTRACT Ubiquitylation of the epithelial Na+ channel (ENaC) plays a critical role in cellular functions, including transmembrane transport of Na+, Na+ and water balance, and blood pressure stabilization. Published studies have suggested that ENaC subunits are targets of ER-related degradation (ERAD) in yeast systems. However, the molecular mechanism underlying proteasome-mediated degradation of ENaC subunits remains to be established. Derlin-1, an E3 ligase mediator, links recognized target proteins to ubiquitin-mediated proteasomal degradation in the cytosol. In the present study, we found that derlin-1 suppressed the expression of ENaC at the protein level and that the subunit α-ENaC (also known as SCNN1A) physically interacted with derlin-1 at the membrane-anchored domains or the loop regions, and that derlin-1 initiated α-ENaC retrotranslocation. In addition, HUWE1, an endoplasmic reticulum (ER)-resident E3 ubiquitin ligase, was recruited and promoted K11-linked polyubiquitylation of α-ENaC and, hence, formation of an α-ENaC ubiquitin-mediated degradation complex. These findings suggest that derlin-1 promotes ENaC ubiquitylation and enhances ENaC ubiquitin- mediated proteasome degradation. The derlin-1 pathway therefore may represent a significant early checkpoint in the recognition and degradation of ENaC in mammalian cells.