Biology subjects

Schaeffer, C.

Publications and source records attributed to Schaeffer, C..

4 recordsLinked to original sources

bioRxiv2025

Calorie restriction leads to degradation of mutant uromodulin and ameliorates inflammation and fibrosis in UMOD-related kidney disease

BackgroundMutations in UMOD, encoding uromodulin, lead to Autosomal Dominant Tubulointerstitial Kidney Disease (ADTKD), a genetic cause of kidney failure. UMOD mutations have a common gain-of-toxic-function effect, causing mutant uromodulin retention in the endoplasmic reticulum (ER). This leads to ER stress, alteration of protein homeostasis and mitochondrial dynamics, defective autophagy and increased cell death. Calorie restriction (CR) exerts a beneficial role in diseases characterized by accumulation of pathogenic protein and inflammation, by modulating several pathways, including autophagy induction and suppression of inflammation and fibrosis. Given the relevance of these features in ADTKD, we investigated the effect of CR on disease onset and progression. MethodsTransgenic mice expressing C147W uromodulin (TgUmodC147W) were subjected to a moderate (30%) CR regimen for 15 or 24 weeks, starting at different stages of disease progression. ResultsCR restored autophagy, as shown by decreased P62 punctae and quenched mTOR activation specifically in mutant uromodulin expressing cells, it recovered expression of key ER-phagy receptor genes, with a concomitant, striking reduction of mutant uromodulin ER retention. In pre-symptomatic TgUmodC147W mice, CR alleviates epithelial cell stress. This, likely along with a direct anti-inflammatory effect of CR, prevents inflammation and progressive decline of kidney function. At this early disease stage, CR ameliorates the already established kidney damage and reduces fibrosis, suggesting reversal of ADTKD phenotype. CR was also effective in significantly delaying disease progression in TgUmodC147W mice with advanced disease and already compromised kidney function. ConclusionOur findings establish the proof-of-principle that counteracting the primary effect of UMOD mutations by stimulating autophagy and quenching inflammation prevents disease onset and progression. This study uncovers the potential of CR as a valuable therapeutic option in the context of ADTKD-UMOD, and possibly other proteinopathies. Key pointsO_LICalorie restriction (CR) stimulates autophagy to degrade mutant uromodulin leading to amelioration of cell stress and tubular damage. C_LIO_LIAt early disease stage CR reverts ADTKD-UMOD phenotype, by preventing inflammation and progressive decline of kidney function and rescuing fibrosis. C_LIO_LIAt advanced disease stage, CR significantly delays disease progression and worsening of kidney function. C_LI

genetics↗

bioRxiv2025

Uromodulin velcro sheets and their interaction with uropathogenic E. coli

Homopolymeric uromodulin (UMOD), the most abundant protein in human urine, protects against urinary tract infections (UTI) by acting as a decoy for uropathogenic E. coli (UPEC). Using cryo-electron tomography (ET), we show that urinary UMOD filaments naturally form sheets that interact with UPEC type I pili. Sheet formation is salt-dependent, and we resolve their high-resolution structure using single-particle cryo-electron microscopy (EM). This reveals a lateral interface between polymers, whose mutation disrupts UMOD filament bundle formation in mammalian cells. Branchless egg coat protein ZPD also forms sheets, and cryo-ET of elastase-treated UMOD indicates that absence of N-terminal branches promotes the stacking of UMOD-like protein sheets into thick 3D matrices. These results rationalize early observations of salt-dependent aggregation of UMOD, explain how UMOD can assemble into extended velcro-like structures that efficiently inactivate a multitude of adhesive UPEC pili, and suggest how UMOD-like molecules can generally organize into supramolecular structures of variable thickness.

biophysics↗

bioRxiv2022

Allelic and Gene Dosage Effects Involving Uromodulin Aggregates Drive Autosomal Dominant Tubulointerstitial Kidney Disease

Missense mutations in the UMOD gene encoding uromodulin cause autosomal dominant tubulointerstitial kidney disease (ADTKD), one of the most common monogenic kidney diseases. A pressing need for ADTKD is to bridge the gap between postulated gain-of-function mutations and organ damage - a prerequisite for therapeutic development. Based on two missense UMOD mutations associated with divergent progression of ADTKD, we generated UmodC171Y and UmodR186S knock-in mice that showed strong allelic and gene dosage effects, with distinct dynamic pathways impacting on uromodulin trafficking, formation of intracellular aggregates, activation of ER stress, unfolded protein and immune responses, kidney damage and progression to kidney failure. Deletion of the wild-type Umod allele in heterozygous UmodR186S mice increased the formation of uromodulin aggregates and ER stress, indicating a protective role of wild-type uromodulin. Studies in kidney tubular cells confirmed biochemical differences between distinct uromodulin aggregates, with activation of specific quality control and clearance mechanisms. Enhancement of autophagy by starvation and mTORC1 inhibition decreased the uromodulin aggregates, suggesting a therapeutic strategy. These studies substantiate a model for allelic effects and the role of toxic aggregates in the progression of ADTKD-UMOD, with relevance for toxic gain-of-function mechanisms and for strategies to improve clearance of mutant uromodulin.

genetics↗

bioRxiv2020

Cryo-EM Structure of Native Human Uromodulin, a Zona Pellucida Module Polymer

Assembly of extracellular filaments and matrices mediating fundamental biological processes such as morphogenesis, hearing, fertilization and antibacterial defense is driven by a ubiquitous polymerization module known as zona pellucida (ZP) "domain". Despite the conservation of this element from hydra to human, no information is available on the filamentous conformation of any ZP module protein. Here we report the cryo-electron microscopy structure of uromodulin (UMOD)/Tamm-Horsfall protein, the most abundant protein in human urine and an archetypal ZP module-containing molecule, in its mature homopolymeric state. UMOD forms a one-start helix with an unprecedented 180-degree twist between subunits enfolded by interdomain linkers that have completely reorganized as a result of propeptide dissociation. Lateral interaction between filaments in the urine generates sheets exposing a checkerboard of binding sites to capture uropathogenic bacteria, and UMOD-based models of mammalian and avian heteromeric egg coat filaments identify a common sperm-binding region at the interface between subunits.

biophysics↗