BACKGROUND
Chronic kidney disease (CKD) is characterized by proximal tubule (PT) stress, oxidative injury, and metabolic dysfunction. Human kidney single-nucleus RNA-sequencing (snRNA-seq) identified enrichment of ubiquitin-dependent protein catabolic processes in injured PT cells, suggesting activation of the ubiquitin-proteasome system during tubular stress. Because Cullin 3 (CUL3), scaffold of ubiquitin ligases, regulates oxidative stress signaling through the KEAP1-NRF2 axis, we investigated its role in PT injury and stress adaptation.
METHODS
Human CKD snRNA-seq data and kidney immunostaining were used to define PT cell states, CUL3-associated pathways, and CUL3 localization. Injury-associated CUL3 regulation was examined in wildtype mice after ischemia-reperfusion injury (IRI). Inducible PT-specific knockout mice (Slc34a1-CreER; Cul3flox/flox) were analyzed at baseline and after injury by histology, immunostaining, proteomics, and injury assessment. In addition, proteomic analysis of a whole-tubule epithelial knockout model (Pax8-rtTA/LC1; Cul3flox/flox) was performed. In immortalized human PT cells, CUL3 was suppressed or activated using CRISPR interference and CRISPR activation, followed by bulk RNA sequencing.
RESULTS
CUL3 transcript and protein expression was enriched in stressed PT states in human CKD. In mice, CUL3 protein abundance increased after injury, supporting injury-associated induction in vivo. PT-specific CUL3 deletion increased antioxidant NQO1 expression without causing overt baseline injury. Proteomic analysis of isolated CUL3-deficient PT cells revealed induction of antioxidant, detoxification, proteostasis, and lipid metabolic programs, together with suppression of mitochondrial oxidative metabolism. Similar changes were observed in whole-tubule Cul3 knockout model. In gene-edited human PT cells, CUL3 suppression recapitulated stress-associated and metabolic remodeling programs, whereas CUL3 activation induced reciprocal transcriptional changes. Despite induction of antioxidant pathways, PT-specific CUL3 deletion did not alter disease severity after IRI or aristolochic acid nephropathy.
CONCLUSION
CUL3 is an injury-induced regulator of PT metabolic and stress-associated states and modulates antioxidant defense and mitochondrial metabolism in PT cells.
Turgay Saritas, Lu Chen, Sadaf Ijaz et al.· Nephrology, Dialysis and Tra...· 0 citations
The function of many genes is still unknown, and conventional driver-discovery methods, which rely on how frequently a gene is mutated, cannot assess genes that are only rarely affected. Here we pair Evo~2-based genome analysis with routine clinical imaging to identify gene--phenotype associations at genome-wide scale. For every somatic mutation across three TCGA cohorts (cRCC=clear cell renal cell carcinoma, HCC=hepatocellular carcinoma, and BC=breast cancer; $n = 340$ total), Evo~2 predicts a severity score, with no task-specific training. Per-gene severity summaries are then correlated with radiomic features extracted from paired tumor segmentations, controlling for total mutation burden. In TCGA-cRCC ($n = 162$), this sweep recovers established renal-cancer drivers and identifies 46 additional genes reaching false discovery rate (FDR) significance absent from curated cancer-gene panels, several of which are Mendelian ciliopathy and cytoskeletal-disease genes. These results demonstrate that pairing a genomic language model with widely available clinical imaging can serve as a hypothesis-free discovery tool for gene--imaging associations invisible to conventional approaches.
Frederik Hauke, Jeremias Krause, P. Wienholt et al.· arXiv.org· 0 citations
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