Experimental Validation and Bioinformatics Analysis Elucidate the Role of MTDH-Mediated PTEN Ubiquitination and Degradation in Podocyte Injury in Diabetic Kidney Disease

Abstract

Diabetic nephropathy (DN) stands as a primary contributor to end-stage renal disease. Podocyte injury is a key factor underlying proteinuria in DN. Metadherin (MTDH) participates in podocyte apoptosis and promotes renal tubular injury in DN. However, its role in podocyte damage and podocyte cytoskeleton remodeling requires further investigation. PTEN plays a crucial role in maintaining podocyte integrity; however, the mechanisms governing PTEN stability in DN remain poorly understood. This study is aimed at investigating the specific functional role of MTDH in PTEN regulation using db/db diabetic mice, human kidney biopsy samples from DN patients, and cultured mouse podocytes exposed to high glucose (HG). MTDH expression was markedly increased in DN kidneys and HG-stimulated podocytes. Elevated MTDH resulted in decreased PTEN protein expression levels without altering PTEN mRNA expression, suggesting a posttranscriptional regulatory mechanism. Further assays demonstrated that MTDH promoted PTEN degradation through the ubiquitin-proteasome pathway. Through bioinformatics analysis of the GSE96804 dataset from the Gene Expression Omnibus (GEO) database, obtaining 13,289 differentially expressed genes and comparing them with the known ubiquitin ligase-encoding genes obtained from the Genecards database, we identified candidate hub genes involved in PTEN ubiquitination-mediated degradation. RNA sequencing identified ubiquitin-conjugating enzyme E2N (UBE2N) as a critical downstream mediator positively regulated by MTDH. Subsequent coimmunoprecipitation experiments confirmed direct interactions between PTEN and UBE2N, enhancing PTEN ubiquitination. Knockdown of UBE2N attenuated MTDH-induced PTEN degradation and podocyte cytoskeletal remodeling. Collectively, our findings reveal a novel regulatory axis wherein MTDH accelerates PTEN ubiquitination and proteasomal degradation via UBE2N, contributing to podocyte injury in DN. Targeting MTDH-driven PTEN ubiquitination degradation presents a promising therapeutic strategy to protect podocytes and mitigate diabetic kidney injury.

Keywords: MTDH; PTEN; diabetic nephropathy; podocyte cytoskeletal remodeling; ubiquitin-conjugating enzyme E2N.