Metadherin orchestrates PKA and PKM2 to activate ß-catenin signaling in podocytes during proteinuric chronic kidney disease.

Podocyte damage is the major cause of glomerular injury and proteinuria in multiple chronic kidney diseases. Metadherin (MTDH) is involved in podocyte apoptosis and promotes renal tubular injury in mouse models of diabetic nephropathy and renal fibrosis; however, its role in podocyte injury and proteinuria needs further exploration. Here, we show that MTDH was induced in the glomerular podocytes of patients with proteinuric chronic kidney disease and correlated with proteinuria. Podocyte-specific knockout of MTDH in mice reversed proteinuria, attenuated podocyte injury, and prevented glomerulosclerosis after advanced oxidation protein products challenge or adriamycin injury. Furthermore, specific knockout of MTDH in podocytes repressed ß-catenin phosphorylation at the Ser675 site and inhibited its downstream target gene transcription. Mechanistically, on the one hand, MTDH increased cAMP and then activated protein kinase A (PKA) to induce ß-catenin phosphorylation at the Ser675 site, facilitating the nuclear translocation of MTDH and ß-catenin; on the other hand, MTDH induced the deaggregation of pyruvate kinase M2 (PKM2) tetramers and promoted PKM2 monomers to enter the nucleus. This cascade of events leads to the formation of the MTDH/PKM2/ß-catenin/CBP/TCF4 transcription complex, thus triggering TCF4-dependent gene transcription. Inhibition of PKA activity by H-89 or blockade of PKM2 deaggregation by TEPP-46 abolished this cascade of events and disrupted transcription complex formation. These results suggest that MTDH induces podocyte injury and proteinuria by assembling the ß-catenin-mediated transcription complex by regulating PKA and PKM2 function.

Serum exosomal microRNA-766-3p expression is associated with poor prognosis of esophageal squamous cell carcinoma.

The aim was to analyze the association between exosomal microRNA (miR)-766-3p expression levels in serum and the prognosis of esophageal squamous cell carcinoma (ESCC). The serum global exosomal miRNA expression of ESCC patients was measured by microRNA microarray. Quantitative real-time PCR was used to analyze the expression levels of candidate miRNAs in both serum and tissues from ESCC patients. Wilcoxon tests were applied to evaluate clinical characteristics and their association with serum levels of exosomal miR-766-3p. A Cox regression model was used to identify prognostic factors. The effects of miR-766-3p expression on cell migration and invasion were examined using Transwell assays, and CCK-8 assays were carried out to measure cell proliferation. The TNM stage was associated with high serum exosomal miR-766-3p levels of ESCC patients (P = .030). Higher serum exosomal miR-766-3p expression levels were associated with poor prognosis (for overall survival, hazard ratio [HR] [95% confidence interval (CI)], 2.21 [1.00, 4.87]; for disease-free survival, HR [95% CI], 2.15 [1.01, 4.59]). However, we found no association between the expression of miR-766-3p in tissue and ESCC prognosis. In vitro results showed that miR-766-3p promotes cell migration and invasion, but not cell proliferation. By using dual-luciferase reporter assay, HOXA13 was confirmed as a direct target gene of miR-766-3p. The ESCC patients with highly expressed serum exosomal miR-766-3p had a significantly worse survival. Therefore, serum exosomal miR-766-3p could serve as a prognostic marker for the assessment of ESCC.