BCAT1 activation reprograms branched-chain amino acids (BCAAs) metabolism and epigenetically promotes inflammation in diabetic retinopathy
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ABSTRACT:
ORGANISM(S): Mus musculus
PROVIDER: GSE282215 | GEO | 2025/06/25
REPOSITORIES: GEO
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Project description:BCAT1 activation reprograms branched-chain amino acids (BCAAs) metabolism and epigenetically promotes inflammation in diabetic retinopathy
| PRJNA1187598 | ENA
Project description:Müller cells are the main macroglial cells of the retina exerting a wealth of functions to maintain retinal homoeostasis. Upon pathological changes in the retina, they become gliotic with both protective and detrimental consequences. Accumulating data also provide evidence for a pivotal role of Müller cells in the pathogenesis of diabetic retinopathy (DR). While microglial cells, the resident immune cells of the retina are considered as main players in inflammatory processes associated with DR, the implication of activated Müller cells in chronic retinal inflammation remains to be elucidated. In order to assess the signaling capacity of Müller cells and their role in retinal inflammation, we performed in-depth proteomic analysis of Müller cell proteomes and secretomes after stimulation with INFγ, TNFα, IL-4, IL-6, IL-10, TGFβ1, TGFβ2 and TGFβ3. We used both, primary porcine Müller cells and the human Müller cell line MIO-M1 for our hypothesis generating approach. Our results point towards an intense signaling capacity of Müller cells, which reacted in a highly discriminating manner upon treatment with different cytokines. Stimulation of Müller cells results in a primarily pro-inflammatory phenotype with secretion of cytokines and components of the complement system. Furthermore, we observed evidence for mitochondrial dysfunction, implying oxidative stress after treatment with the various cytokines. Finally, both MIO-M1 cells and primary porcine Müller cells showed several characteristics of atypical antigen-presenting cells, as they are capable of inducing MHC class I and MHC class II with co-stimulatory molecules. In line with this, they express proteins associated with formation and maturation of phagosomes. Thus, our findings underline the importance of Müller cell signaling in the inflamed retina, indicating an active role in chronic retinal inflammation underlying the pathogenesis of diabetic retinopathy.
2022-02-16 | PXD028390 | Pride
Project description:Diabetic retinopathy (DR), the leading cause of blindness in working-age adults, is thought to be primarily a microvascular complication of diabetes. As a central element of the retinal neurovascular unit, Müller cells, the major macroglia of the retina, are important for maintaining a healthy and functional retina and play a critical role in several pathological events during DR disease progression. Here, we aim to improve our understanding of Müller cell-specific signalling pathways that are altered during DR disease progression in order to develop novel gene therapy strategies that target Müller cells. We used a multi-omics approach on purified Müller cells from 6-month-old control and diabetic db/db mice, including (i) RNA-seq followed by oPOSSUM-3 transcription factor (TF) binding site cluster analysis, (ii) glial chromatin landscape analysis by ATAC-seq, and (iii) Müller cell proteomics by MS/MS mass spectrometry. This led to the identification of the glucocorticoid receptor (GR, gene ID: Nr3c1) most highly expressed in Müller cells. In cells from diabetic mice, GR mRNA and protein expression is significantly reduced and its target gene cluster downregulated in Müller cells. Importantly, GR was identified as a potential master regulator not only by oPOSSUM analysis based on differentially expressed mRNA in Müller cells, but also validated by the ATAC-seq approach. In an in vitro cortisol-stimulated retinal explant model cortisol not only increased GR phosphorylation, but also induced changes in the expression of known downstream GR target genes. Finally, we evaluated whether AAV-mediated GR overexpression in Müller cells improves retinal functionality and we found moderate improvements indicated by electroretinography. While synthetic and topical glucocorticoids are widely used in ophthalmology with undeniable beneficial effects, our study provides valuable new insight into the role of GR signalling and glial alterations in the diabetic retina. This supports the therapeutic concept of locally enhancing the GR signaling axis. Our findings of reduced GR levels in Müller cells of the diabetic retina suggests that therapeutic approaches should aim at increasing the expression of the receptor rather than adding more ligand.
2024-05-23 | PXD045085 | Pride
Project description:We performed gene expression profiling of mRNA/cDNA isolated from N = 117 flow sorted CLL. We detected aberrant expression of the metabolic enzyme branched chain amino acid transferase (BCAT1) in CLL with del17p/TP53mut. Through extensive validation, we confirmed the highly preferential expression of BCAT1 in CLL with del17p/TP53mut (66%) or trisomy 12 (77%). BCAT1 was not expressed in B cells isolated from normal human lymph nodes. The products of the bidirectional BCAT1 reaction, including leucine, acetyl-CoA, and alpha-ketoglutarate are known activators of MTOR. We measured an ~two-fold higher MTOR activity via normalized p-S6K levels in primary CLL with BCAT1 high versus absent expression before and after sIgM crosslinking. Through steady state metabolomics and heavy isotope metabolic tracing in primary CLL cells, we demonstrate that CLL cells are avid consumers of branched chain amino acids (BCAAs) and that BCAT1 in CLL engages in bidirectional substrate reactions. Of additional interest, CLL with aberrant BCAT1 expression were less sensitive to Venetoclax-induced apoptosis. Biologically, three CLL-derived cell lines with disruption of BCAT1 had substantially reduced growth ex vivo. Clinically, the expression of any detectable BCAT1 protein in CLL independently associated with shorter median survival (125 months versus 296 months; p < 0.0001), even after exclusion of del17p/TP53mut cases.
2024-12-23 | GSE239832 | GEO
Project description:Müller cells are the principal glial cells in the retina. Alterations in Müller cell behaviour are observed in retinal tissue from patients with proliferative diabetic retinopathy. The purpose of this study was to compare gene and protein expression profile of normal human Müller cells (NHMC) with two spontaneously human Müller cell lines generated from type 1 (HMCL-I) and type 2 (HMCL-II) diabetic donors using Serial Analysis Gene Expression (SAGE). Approximatively 50 000 tags were sequenced for each of the three SAGE libraries. Identification of the transcripts was obtained by matching the 15bp (CATG + 11bp) with the UniGene and GenBank databases. Classification of the genes was based upon the updated information of the genome directory found at the NCBI website. SAGE allowed us to characterize the entire transcriptome of human Müller cells and to compare these data with those from Müller cells of type 1 and 2 diabetic donors. Keywords: Müller cells, SAGE, HMCL-I, HMCL-II, expression profile comparison
2006-08-12 | GSE3118 | GEO
Project description:The branched-chain amino acid (BCAA) metabolism plays pleiotropic roles in homeostasis. Here we show that human acute leukemia-initiating cells (LICs), but not normal hematopoietic stem cells, are heavily addicted to the BCAA metabolism, irrespective of myeloid or lymphoid types. Human acute leukemia cells had a high level of BCAAs, transporting free BCAAs into the cytoplasm. Functional inhibition of BCAA transaminase-1 (BCAT1), a catalytic enzyme for BCAAs, induced apoptosis of human LICs, and suppressed reconstitution of human leukemia in xenograft models. Furthermore, deprivation of BCAAs from daily diet in mice transplanted with human LICs strongly inhibited their expansion and self-renewal in vivo. The BCAT1 inhibition inactivates the PRC2 function for epigenetic maintenance of stem cell signatures via downregulation of EZH2 and EED, critical PRC2 components, and inhibited the mTORC1 signaling for leukemia propagation. Thus, targeting the BCAA metabolism should be a powerful approach to erase cancer stemness in human acute leukemias.
2019-08-01 | GSE132512 | GEO
Project description:Diabetic retinopathy (DR), the leading cause of blindness in working-age adults, is thought to be primarily a microvascular complication of diabetes. Müller cells, the major macroglia of the retina, are important for maintaining a healthy and functional retina and play a critical role in several pathological events during DR disease progression as they are a central element of the retinal neurovascular unit. Here, we aim to improve our understanding of Müller cell-specific signaling pathways that are altered during disease progression in order to develop novel gene therapy strategies targeting Müller cells in DR. To achieve this, we used a multi-omics approach on purified Müller cells from 6-month-old control and diabetic db/db mice, including (i) RNA-seq followed by oPOSSUM-3 transcription factor (TF) binding site cluster analysis, (ii) glial chromatin landscape analysis by ATAC-seq, and (iii) Müller cell proteomics by MS/MS mass spectrometry. This led to the identification of the glucocorticoid receptor (GR, gene ID: Nr3c1) as the most promising candidate. Its transcripts and protein were most highly expressed in Müller cells and significantly reduced in cells from diabetic mice, its target gene cluster was downregulated in Müller cells from diabetic animals, and importantly, it was identified as a potential master regulator not only by oPOSSUM analysis based on differentially expressed mRNA in Müller cells, but also validated by the ATAC-seq approach. Next, we investigated the effect of GR modulation in an in vitro cortisol-stimulated retinal explant model. Cortisol not only increased GR phosphorylation levels, but also induced changes in the expression of known downstream GR target genes. Finally, we evaluated whether AAV-mediated GR overexpression in Müller cells improves retinal functionality and found moderate functional improvements in electroretinogram recordings. Although synthetic and topical glucocorticoids are widely used in ophthalmology with undeniable beneficial effects, our study provides valuable new insights into the role of GR signaling and glial alterations in the diabetic retina and thus supports the therapeutic concept of locally enhancing the GR signaling axis. However, our finding of reduced GR levels in Müller cells of the diabetic retina suggests that therapeutic approaches should aim at increasing the expression of the receptor rather than adding more ligands. This may result in optimized local efficacy with fewer systemic unwarranted side effects.
2024-01-25 | GSE236627 | GEO
Project description:The branched-chain amino acid (BCAA) pathway and high levels of BCAA transaminase 1 (BCAT1) have recently been associated with aggressiveness in several cancer entities. However, the mechanistic role of BCAT1 in this process remains largely uncertain. Here, by performing high-resolution proteomic analysis of human acute myeloid leukaemia (AML) stem-cell and non-stem-cell populations, we find the BCAA pathway enriched and BCAT1 protein and transcripts overexpressed in leukaemia stem cells. We show that BCAT1, which transfers α-amino groups from BCAAs to α-ketoglutarate (αKG), is a critical regulator of intracellular αKG homeostasis. Further to its role in the tricarboxylic acid cycle, αKG is an essential cofactor for αKG-dependent dioxygenases such as Egl-9 family hypoxia inducible factor 1 (EGLN1) and the ten-eleven translocation (TET) family of DNA demethylases. Knockdown of BCAT1 in leukaemia cells caused accumulation of αKG, leading to EGLN1-mediated HIF1α protein degradation. This resulted in a growth and survival defect and abrogated leukaemia-initiating potential. By contrast, overexpression of BCAT1 in leukaemia cells decreased intracellular αKG levels and caused DNA hypermethylation through altered TET activity. AML with high levels of BCAT1 (BCAT1high) displayed a DNA hypermethylation phenotype similar to cases carrying a mutant isocitrate dehydrogenase (IDHmut), in which TET2 is inhibited by the oncometabolite 2-hydroxyglutarate11,12. High levels of BCAT1 strongly correlate with shorter overall survival in IDHWTTET2WT, but not IDHmut or TET2mutAML. Gene sets characteristic for IDHmut AML13 were enriched in samples from patients with an IDHWTTET2WTBCAT1high status. BCAT1highAML showed robust enrichment for leukaemia stem-cell signatures14,15, and paired sample analysis showed a significant increase in BCAT1 levels upon disease relapse. In summary, by limiting intracellular αKG, BCAT1 links BCAA catabolism to HIF1α stability and regulation of the epigenomic landscape, mimicking the effects of IDH mutations. Our results suggest the BCAA–BCAT1–αKG pathway as a therapeutic target to compromise leukaemia stem-cell function in patients with IDHWTTET2WT AML.
2020-02-21 | PXD008307 | Pride
Project description:The branched chain amino acid (BCAA) pathway and high levels of BCAA transaminase 1 (BCAT1) have recently been associated with aggressiveness in several cancer entities. However, the mechanistic role of BCAT1 in this process remains largely uncertain. By performing high-resolution proteomic analysis of human acute myeloid leukaemia (AML) stem cell (LSC) and non-LSC populations, we found the BCAA pathway enriched and BCAT1 overexpressed in LSCs. We show that BCAT1, which transfers α-amino groups from BCAAs to α-ketoglutarate (αKG), is a critical regulator of intracellular αKG homeostasis. Next to its role in the tricarboxylic acid (TCA) cycle αKG is an essential co-factor for αKG-dependent dioxygenases such as EGLN1 and the TET family of DNA demethylases. Knockdown of BCAT1 in leukaemia cells caused accumulation of αKG leading to HIF1a protein degradation mediated by EGLN1. This resulted in a growth and survival defect and abrogated leukaemia-initiating potential. In contrast, overexpression (OE) of BCAT1 in leukaemia cells decreased intracellular αKG levels and caused DNA hypermethylation via altered TET activity. BCAT1high AMLs displayed a DNA hypermethylation phenotype similar to cases carrying mutant isocitrate dehydrogenase (IDHmut), in which TET2 is inhibited by the oncometabolite 2-hydroxyglutarate. High levels of BCAT1 strongly correlate with shorter overall survival in IDHwtTET2wt, but not IDHmut or TET2mut AMLs. Gene sets characteristic for IDHmut AMLs were enriched in IDHwtTETwtBCAT1high patient samples. BCAT1high AMLs showed robust enrichment for LSC signatures and paired sample analysis revealed a significant increase of BCAT1 levels upon disease relapse. In summary, by limiting intracellular αKG, BCAT1 links BCAA catabolism to HIF1a stability and regulation of the epigenomic landscape. Our results suggest the BCAA-BCAT1-αKG pathway as a therapeutic target to compromise LSC function in IDHwtTET2wt AML patients.
2017-11-08 | GSE103960 | GEO
Project description:The branched chain amino acid (BCAA) pathway and high levels of BCAA transaminase 1 (BCAT1) have recently been associated with aggressiveness in several cancer entities. However, the mechanistic role of BCAT1 in this process remains largely uncertain. By performing high-resolution proteomic analysis of human acute myeloid leukaemia (AML) stem cell (LSC) and non-LSC populations, we found the BCAA pathway enriched and BCAT1 overexpressed in LSCs. We show that BCAT1, which transfers α-amino groups from BCAAs to α-ketoglutarate (αKG), is a critical regulator of intracellular αKG homeostasis. Next to its role in the tricarboxylic acid (TCA) cycle αKG is an essential co-factor for αKG-dependent dioxygenases such as EGLN1 and the TET family of DNA demethylases. Knockdown of BCAT1 in leukaemia cells caused accumulation of αKG leading to HIF1a protein degradation mediated by EGLN1. This resulted in a growth and survival defect and abrogated leukaemia-initiating potential. In contrast, overexpression (OE) of BCAT1 in leukaemia cells decreased intracellular αKG levels and caused DNA hypermethylation via altered TET activity. BCAT1high AMLs displayed a DNA hypermethylation phenotype similar to cases carrying mutant isocitrate dehydrogenase (IDHmut), in which TET2 is inhibited by the oncometabolite 2-hydroxyglutarate. High levels of BCAT1 strongly correlate with shorter overall survival in IDHwtTET2wt, but not IDHmut or TET2mut AMLs. Gene sets characteristic for IDHmut AMLs were enriched in IDHwtTETwtBCAT1high patient samples. BCAT1high AMLs showed robust enrichment for LSC signatures and paired sample analysis revealed a significant increase of BCAT1 levels upon disease relapse. In summary, by limiting intracellular αKG, BCAT1 links BCAA catabolism to HIF1a stability and regulation of the epigenomic landscape. Our results suggest the BCAA-BCAT1-αKG pathway as a therapeutic target to compromise LSC function in IDHwtTET2wt AML patients.
2017-11-08 | GSE100778 | GEO