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 ubiquitinmediated proteasome degradation. The derlin-1 pathway therefore may represent a significant early checkpoint in the recognition and degradation of ENaC in mammalian cells.

The main functions of the epithelial sodium channel (ENaC) in the kidney distal nephron are mediation of sodium and water balance and stabilization of blood pressure. Estrogen has important effects on sodium and water balance and on premenopausal blood pressure, but its role in the regulation of ENaC function is not fully understood. Female Sprague–Dawley rats were treated with 17β-estradiol for 6 weeks following bilateral ovariectomy. Plasma estrogen, aldosterone, creatinine, and electrolytes were analyzed, and α-ENaC and derlin-1 protein expression in the kidney was determined by immunohistochemistry and western blotting. The expression levels of α-ENaC, derlin-1, AMPK, and related molecules were also examined by western blotting and real-time PCR in cultured mouse renal collecting duct (mpkCCDc14) epithelial cells following estrogen treatment. Immunofluorescence and coimmunoprecipitation were performed to detect α-ENaC binding with derlin-1 and α-ENaC ubiquitination. The results demonstrated that the loss of estrogen elevated systolic blood pressure in ovariectomized (OVX) rats. OVX rat kidneys showed increased α-ENaC expression but decreased derlin-1 expression. In contrast, estrogen treatment decreased α-ENaC expression but increased derlin-1 expression in mpkCCDc14 cells. Moreover, estrogen induced α-ENaC ubiquitination by promoting the interaction of α-ENaC with derlin-1 and evoked phosphorylation of AMPK in mpkCCDc14 cells. Our study indicates that estrogen reduces ENaC expression and blood pressure in OVX rats through derlin-1 upregulation and AMPK activation.

Objective: The incidence of ulcerative colitis (UC) is increasing year by year, which leads to increasing cost of medical resources investment, and the exact pathogenesis of the disease is still unclear, leading to difficulties in clinical diagnosis and treatment. This study is based on a bioinformatics approach to search for possible key genes leading to the development of this disease, hoping to provide clinicians with new biomarkers that can be used for reference, so that patients can receive timely diagnosis and treatment.Methods: Peripheral blood-related information was first obtained from the Gene Expression Omnibus (GEO) database for UC patients and non-UC populations. Then differentially expressed genes were identified using R language (based on "Limma" software). Functional enrichment analysis was then performed, followed by screening of central genes, and finally correlations between the central genes were investigated using Spearman correlation analysis.Results: Fifty-nine up-regulated and 39 down-regulated DEGs were screened. These genes were involved in pathways such as viral protein-cytokine receptor interaction, cytokine-cytokine receptor interaction, biosynthesis of pantothenic acid and coenzyme A, IL-17 signaling pathway and chemokine signaling pathway. And growth regulatory alpha protein, C-X-C chemokine receptor 1, C-C patterned chemokine 2, and trigger receptor 1 expressed in bone marrow cells were found to be the top ten hub genes. The final correlation analysis showed a positive correlation between these ten hub genes.Conclusion The present study identified 10 DEGs as possible biomarkers for the diagnosis of patients with ulcerative colitis. Experiments are needed to validate the present study.