Network-Based Expression Analyses and Experimental Verifications Reveal the Involvement of STUB1 in Acute Kidney Injury

STUB1 exacerbates calcium oxalate-induced kidney injury by modulating reactive oxygen species-mediated cellular autophagy via regulating CFTR ubiquitination

The formation of calcium oxalate (CaOx) crystals in the kidneys leads to renal epithelial damage and the progression of crystalline nephropathy. This study investigated the role of STIP1 homology and U-box protein 1 (STUB1), an E3 ubiquitin ligase, and cystic fibrosis transmembrane conductance regulator (CFTR), a chloride channel, in CaOx-related renal damage and autophagy regulation. HK-2 cells were treated with various doses of CaOx monohydrate (COM) to simulate kidney injury in vitro. Cell viability, reactive oxygen species (ROS) production, and apoptosis were assessed. The regulation of CFTR ubiquitination by STUB1 was confirmed by immunoprecipitation. An in vivo model was established by injecting mice with glyoxylate. COM treatment dose-dependently decreased cell viability, increased TNF-α and ROS production, and induced apoptotic cell death in HK-2 cells. COM-treated cells also showed decreased CFTR protein expression. CFTR overexpression improved cell viability and reduced ROS production in COM-stimulated HK-2 cells. Bioinformatics analysis predicted CFTR's ubiquitination binding site for STUB1. Further analysis confirmed the role of STUB1 as a ubiquitin ligase in CFTR degradation. Knockdown of STUB1 upregulated CFTR expression, while STUB1 overexpression had the opposite effect. Knockdown of CFTR reversed the impact of STUB1 deficiency on autophagy. The in vivo experiments showed that CFTR overexpression attenuated kidney tissue damage and CaOx deposition in mice. STUB1-mediated CFTR ubiquitination plays a crucial role in mitigating calcium oxalate-related renal damage by regulating autophagy. Targeting the STUB1/CFTR axis may hold therapeutic potential for treating kidney injury associated with calcium oxalate deposition.

CHIP protects against septic acute kidney injury by inhibiting NLRP3-mediated pyroptosis

Septic acute kidney injury (S-AKI), the most common type of acute kidney injury (AKI), is intimately related to pyroptosis and oxidative stress in its pathogenesis. Carboxy-terminus of Hsc70-interacting protein (CHIP), a U-box E3 ligase, modulates oxidative stress by degrading its targeted proteins. The role of CHIP in S-AKI and its relevance with pyroptosis have not been investigated. In this study, we showed that CHIP was downregulated in renal proximal tubular cells in lipopolysaccharide (LPS)-induced S-AKI. Besides, the extent of redox injuries in S-AKI was attenuated by CHIP overexpression or activation but accentuated by CHIP gene disruption. Mechanistically, our work demonstrated that CHIP interacted with and ubiquitinated NLRP3 to promote its proteasomal degradation, leading to the inhibition of NLRP3/ACS inflammasome-mediated pyroptosis. In summary, this study revealed that CHIP ubiquitinated NLRP3 to alleviate pyroptosis in septic renal injuries, suggesting that CHIP might be a potential therapeutic target for S-AKI.

STUB1/CHIP: New insights in cancer and immunity

The STUB1 gene (STIP1 homology and U-box-containing protein 1), located at 16q13.3, encodes the CHIP (carboxyl terminus of Hsc70-interacting protein), an essential E3 ligase involved in protein quality control. CHIP comprises three domains: an N-terminal tetratricopeptide repeat (TPR) domain, a middle coiled-coil domain, and a C-terminal U-box domain. It functions as a co-chaperone for heat shock protein (HSP) via the TPR domain and as an E3 ligase, ubiquitinating substrates through its U-box domain. Numerous studies suggest that STUB1 plays a crucial role in various physiological process, such as aging, autophagy, and bone remodeling. Moreover, emerging evidence has shown that STUB1 can degrade oncoproteins to exert tumor-suppressive functions, and it has recently emerged as a novel player in tumor immunity. This review provides a comprehensive overview of STUB1's role in cancer, including its clinical significance, impact on tumor progression, dual roles, tumor stem cell-like properties, angiogenesis, drug resistance, and DNA repair. In addition, we explore STUB1's functions in immune cell differentiation and maturation, inflammation, autoimmunity, antiviral immune response, and tumor immunity. Collectively, STUB1 represents a promising and valuable therapeutic target in cancer and immunology.

Assessing Kidney Injury Induced by Mercuric Chloride in Guinea Pigs with In Vivo and In Vitro Experiments

Acute kidney injury, which is associated with high levels of morbidity and mortality, affects a significant number of individuals, and can be triggered by multiple factors, such as medications, exposure to toxic chemicals or other substances, disease, and trauma. Because the kidney is a critical organ, understanding and identifying early cellular or gene-level changes can provide a foundation for designing medical interventions. In our earlier work, we identified gene modules anchored to histopathology phenotypes associated with toxicant-induced liver and kidney injuries. Here, using in vivo and in vitro experiments, we assessed and validated these kidney injury-associated modules by analyzing gene expression data from the kidneys of male Hartley guinea pigs exposed to mercuric chloride. Using plasma creatinine levels and cell-viability assays as measures of the extent of renal dysfunction under in vivo and in vitro conditions, we performed an initial range-finding study to identify the appropriate doses and exposure times associated with mild and severe kidney injuries. We then monitored changes in kidney gene expression at the selected doses and time points post-toxicant exposure to characterize the mechanisms of kidney injury. Our injury module-based analysis revealed a dose-dependent activation of several phenotypic cellular processes associated with dilatation, necrosis, and fibrogenesis that were common across the experimental platforms and indicative of processes that initiate kidney damage. Furthermore, a comparison of activated injury modules between guinea pigs and rats indicated a strong correlation between the modules, highlighting their potential for cross-species translational studies.

Treatment of Gout with TCM Using Turmeric and Corn Silk: A Concise Review Article and Pharmacology Network Analysis

OBJECTIVE

This work aimed to study the compounds, targets, and pathways of turmeric and corn silk for gout and to explore the mechanism of "the same disease with different treatments" based on network pharmacology and molecular docking.

METHODS

We used the TCMSP, PubChem, and SEA databases to screen the compounds and targets of turmeric and corn silk, gout-related proteins through TTD, Drugbank, DisGeNET, GeneCards, OMIM, and PharmGkb, and used Cytoscape to construct a "compound-target-disease" network. Then, we constructed a protein-protein interaction network (PPI) and used Metascape to perform GO and KEGG analysis. Finally, molecular docking (SYBYL) was used to verify the degree of binding between key targets and compounds.

RESULTS

We found bisacumol, campesterol, and stigmasterol to be the main turmeric compounds that exerted a marked effect on gout treatment by targeting protein processing in the endoplasmic reticulum through the HSPA1B, HSP90AB1, and STUB1 proteins. The main corn silk compound, Mandenol, treated gout by targeting the Hippo signaling pathway through the CTNNB1, YWHAG, and YWHAZ proteins.

CONCLUSION

Turmeric and corn silk can treat the same disease, gout, through different pathways and targets. The scientific connotation of "same disease with different treatments" can be preliminarily clarified by analyzing targets and pathways.

Identification of RPS7 as the Biomarker of Ferroptosis in Acute Kidney Injury

Objective

This paper aims to explore novel ferroptosis-related biomarkers for acute kidney injury (AKI).

Methods

Various bioinformatic methods, such as differential expression analysis, functional annotation analysis, machine learning, and chemical-gene network analysis, were used in this study. Furthermore, the expression and proferroptotic role of RPS7 were validated with further bioinformatics analysis and biochemical experiments.

Results

GSE30718 dataset and GSE139061 dataset were used, and the differentially expressed genes (DEGs) were screened. The DEGs were overlapped with ferroptosis-related genes and genes associated with AKI, which led to the identification of four candidate genes. Machine learning and ROC curve analysis were conducted, and RPS7 and TRIB3 were selected for diagnostic model analysis and functional analysis. Finally, the upregulation of RSP7 in cisplatin-induced AKI was validated in cisplatin-induced AKI, and its proferroptotic role was confirmed in cisplatin-treated proximal tubular cells.

Conclusion

Our results indicated that RPS7 might present as a novel ferroptosis-related biomarker for AKI, and it derived ferroptosis to accentuate cisplatin-induced AKI.