Transcriptional Changes in Regulatory T Cells From Patients With Autoimmune Polyendocrine Syndrome Type 1 Suggest Functional Impairment of Lipid Metabolism and Gut Homing

Loss of VHL-mediated pRb regulation promotes clear cell renal cell carcinoma

The von Hippel-Lindau (VHL) tumor suppressor is a substrate-defining component of E3 ubiquitin ligase complexes that target cellular substrates for proteasome-mediated degradation. VHL inactivation by mutation or transcriptional silencing is observed in most sporadic cases of clear cell renal cell carcinoma (ccRCC). VHL loss in ccRCC leads to constitutive stabilization of E3 ligase substrates, including hypoxia inducible factor α (HIFα). HIFα stabilization upon VHL loss is known to contribute to ccRCC development through transactivation of hypoxia-responsive genes. HIF-independent VHL targets have been implicated in oncogenesis, although those mechanisms are less well-defined than for HIFα. Using proximity labeling to identify proteasomal-sensitive VHL interactors, we identified retinoblastoma protein (pRb) as a novel substrate of VHL. Mechanistically, VHL interacts with pRb in a proteasomal-sensitive manner, promoting its ubiquitin-mediated degradation. Concordantly, VHL-inactivation results in pRb hyperstabilization. Functionally, loss of pRb in ccRCC led to increased cell death, transcriptional changes, and loss of oncogenic properties in vitro and in vivo. We also show that downstream transcriptional changes induced by pRb hyperstabilization may contribute to ccRCC tumor development. Together, our findings reveal a novel VHL-related pathway which can be therapeutically targeted to inhibit ccRCC tumor development.

Longitudinal Immune Profiling in Autoimmune Polyendocrine Syndrome Type 1

Autoimmune polyendocrine syndrome Type-1 (APS-1) is a rare, but severe organ-specific autoimmune disease caused by mutations in the autoimmune regulator (AIRE) gene. Lack of AIRE causes autoreactive T cells to escape negative selection and alters the T regulatory cell subset. However, little is known about how the immune cell subsets vary across the lifespan in APS-1. Here we analysed the peripheral distribution of 13 immune cell subsets along the lifespan using epigenetic quantification. We found the largest discrepancy in immune cells to appear early in APS-1 patients' lives, coinciding with the time point they obtained most of their clinical symptoms. We further revealed longitudinal changes in cell compositions both within the adaptive and the innate arms of the immune system. We found that cell frequencies of B cells, T-cell subgroups, nonclassical monocytes, and Natural Killer cells to be reduced in young APS-1 patients. We also found B-cell frequencies to decrease with ageing in both patients and healthy controls. Our results suggest that Tregs, follicular helper T, and natural killer cells have opposing trends of cell frequencies during life, indicating the importance of considering the age profiles of cohorts which could otherwise lead to conflicting conclusions.

Mechanism of O-GlcNAcylation regulating liver lipid synthesis in mice through FASN

Nonalcoholic fatty liver disease (NAFLD) has become one of the most common chronic liver diseases. O-Linked attachment of beta-N-acetylglucosamine (O-GlcNAc) are ubiquitous post-translational modifications of proteins as "nutrient sensors" and "stress receptors" in the body that are involved in maintaining normal cellular physiological functions. Increased levels of O-GlcNAcylation have been found in the liver samples of patients with NAFLD and nonalcoholic steatohepatitis. However, the role of O-GlcNAcylation in the development and pathogenesis of NAFLD remains unclear. Here, we sought to determine the specific role of O-GlcNAcylation in NAFLD. In this study, the results demonstrated that inhibition of O-GlcNAc transferase (OGT) led to decreased expression of liver lipid synthesis genes and proteins in vitro. In addition, we showed that fatty acid synthase (FASN) expression was positively correlated with O-GlcNAcylation levels. Immunoprecipitation and pulldown assays confirmed the interaction between FASN and OGT at the serine 1483 of FASN, to inhibit K48-linked ubiquitination and degradation of FASN, thereby promoting hepatic lipid accumulation and the development of NAFLD. Administration of the OGT inhibitor OSMI-1 to ob/ob mice led to decreased liver lipid accumulation, further confirming our in vitro experimental results. Finally, we used liver-specific Ogt gene knockout mice fed a high-fat diet to elucidate the specific mechanism of O-GlcNAcylation on NAFLD and found that knockdown of the Ogt gene led to decreased liver lipid accumulation. In conclusion, our findings show that inhibiting the O-GlcNAcylation of FASN at the S1483 site promotes the K48-linked ubiquitination and degradation of FASN and leads to inhibition of lipid accumulation in the liver. Treatment with the OGT inhibitor OSMI-1 leads to decreased lipid accumulation in the liver, suggesting that targeting O-GlcNAcylation sites could be a potential therapeutic strategy for alleviating NAFLD.

Genetic Commonalities Between Metabolic Syndrome and Rheumatic Diseases Through Disease Interactome Modules

This study aims to elucidate the potential genetic commonalities between metabolic syndrome (MetS) and rheumatic diseases through a disease interactome network, according to publicly available large-scale genome-wide association studies (GWAS). The analysis included linkage disequilibrium score regression analysis, cross trait meta-analysis and colocalisation analysis to identify common genetic overlap. Using modular partitioning, the network-based association between the two disease proteins in the protein-protein interaction set was divided and quantified. Clinical samples from public databases were used to confirm the mapped genes. Mendelian randomisation analyses were conducted using genetic instrumental variables for causal inference. MetS and rheumatoid arthritis (RA), ankylosing spondylitis (AS), systemic lupus erythematosus (SLE), Sjogren's syndrome (SS) and their primary module networks shared topological overlap and genetic correlation. Functional analysis highlighted the significance of these shared targets in processes such as a diverse array of metabolic pathways involving glucose, lipids, energy, protein transport, inflammatory response, autophagy and cytokine regulation, elucidating the pathways through which MetS intersects with rheumatic diseases. Causal associations were determined between MetS phenotypes and rheumatic diseases. The persistence of MetS effects on rheumatic diseases remained evident even after adjusting for alcohol consumption and smoking. We have highlighted specific genetic associations between MetS and rheumatic diseases. Several genes (e.g., PRRC2A, PSMB8, BAG6, GPSM3, PBX2, etc.) have been identified with molecular commonalities in MetS and RA, AS, SLE and SS, which may serve as potential targets for shared treatments.

Single cell characterization of blood and expanded regulatory T cells in autoimmune polyendocrine syndrome type 1

Immune tolerance fails in autoimmune polyendocrine syndrome type 1 (APS-1) because of AIRE mutations. We have used single cell transcriptomics to characterize regulatory T cells (Tregs) sorted directly from blood and from in vitro expanded Tregs in APS-1 patients compared to healthy controls. We revealed only CD52 and LTB (down) and TXNIP (up) as consistently differentially expressed genes in the datasets. There were furthermore no large differences of the TCR-repertoire of expanded Tregs between the cohorts, but unique patients showed a more restricted use of specific clonotypes. We also found that in vitro expanded Tregs from APS-1 patients had similar suppressive capacity as controls in co-culture assays, despite expanding faster and having more exhausted cells. Our results suggest that APS-1 patients do not have intrinsic defects in their Treg functionality, and that their Tregs can be expanded ex vivo for potential therapeutic applications.

The implications of FASN in immune cell biology and related diseases

Fatty acid metabolism, particularly fatty acid synthesis, is a very important cellular physiological process in which nutrients are used for energy storage and biofilm synthesis. As a key enzyme in the fatty acid metabolism, fatty acid synthase (FASN) is receiving increasing attention. Although previous studies on FASN have mainly focused on various malignancies, many studies have recently reported that FASN regulates the survival, differentiation, and function of various immune cells, and subsequently participates in the occurrence and development of immune-related diseases. However, few studies to date systematically summarized the function and molecular mechanisms of FASN in immune cell biology and related diseases. In this review, we discuss the regulatory effect of FASN on immune cells, and the progress in research on the implications of FASN in immune-related diseases. Understanding the function of FASN in immune cell biology and related diseases can offer insights into novel treatment strategies for clinical diseases.

Rebooting Regulatory T Cell and Dendritic Cell Function in Immune-Mediated Inflammatory Diseases: Biomarker and Therapy Discovery under a Multi-Omics Lens

Immune-mediated inflammatory diseases (IMIDs) are a group of autoimmune and chronic inflammatory disorders with constantly increasing prevalence in the modern world. The vast majority of IMIDs develop as a consequence of complex mechanisms dependent on genetic, epigenetic, molecular, cellular, and environmental elements, that lead to defects in immune regulatory guardians of tolerance, such as dendritic (DCs) and regulatory T (Tregs) cells. As a result of this dysfunction, immune tolerance collapses and pathogenesis emerges. Deeper understanding of such disease driving mechanisms remains a major challenge for the prevention of inflammatory disorders. The recent renaissance in high throughput technologies has enabled the increase in the amount of data collected through multiple omics layers, while additionally narrowing the resolution down to the single cell level. In light of the aforementioned, this review focuses on DCs and Tregs and discusses how multi-omics approaches can be harnessed to create robust cell-based IMID biomarkers in hope of leading to more efficient and patient-tailored therapeutic interventions.