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Transketolase in human Müller cells is critical to resist light stress through the pentose phosphate and NRF2 pathways

ABSTRACT: The Pentose Phosphate Pathway (PPP), a metabolic offshoot of the glycolytic pathway, provides protective metabolites and molecules essential for cell redox balance and survival. Transketolase (TKT) is the critical enzyme that controls the extent of “traffic flow” through the PPP. Here, we explored the role of TKT in maintaining the health of the human retina. We found that Müller cells were the primary retinal cell type expressing TKT in the human retina. We further explored the role of TKT in human Müller cells by knocking down its expression in primary cultured Müller cells (huPMCs), isolated from the human retina (11 human donors in total), under lightinduced oxidative stress. TKT knockdown and light stress reduced TKT enzymatic activities and the overall metabolic activities of huPMCs with no detectable cell death. TKT knockdown restrained the PPP traffic flow, reduced the expression of NAD(P)H Quinone Dehydrogenase 1 (NQO1) and impaired the antioxidative response of NRF2 to light stress. TKT knockdown also inhibited overall glucose intake, reduced expression of Dihydrolipoamide dehydrogenase (DLD) and impaired the energy supply of huPMCs. In summary, Müller cell-mediated TKT activity plays a critical protective role in the stressed retina. Knockdown of TKT disrupted the PPP and impaired overall glucose utilisation by huPMCs and rendered huPMCs more vulnerable to light stress by impairing energy supply and antioxidative NRF2 responses.

ORGANISM(S): Homo sapiens

PROVIDER: GSE198554 | GEO | 2022/06/26

REPOSITORIES: GEO

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Non-oxidative pentose phosphate pathway controls regulatory T cell function by integrating metabolism and epigenetics

Project description:Regulatory T cells (Tregs) are critical for maintaining immune homeostasis and preventing autoimmunity. Here, we show that the non-oxidative pentose phosphate pathway (PPP) regulates Treg function to prevent autoimmunity. Deletion of transketolase (TKT), an indispensable enzyme of non-oxidative PPP, in Tregs causes a fatal autoimmune disease in mice, with impaired Treg suppressive capability despite regular Treg numbers and normal Foxp3 expression levels. Mechanistically, reduced glycolysis and enhanced oxidative stress induced by TKT deficiency triggers excessive fatty acid and amino acid catabolism, resulting in uncontrolled oxidative phosphorylation and impaired mitochondrial fitness. Reduced -KG levels as a result of reductive TCA cycle activity leads to DNA hypermethylation, thereby limiting functional gene expression and suppressive activity of TKT-deficient Tregs. We also find that TKT levels are frequently downregulated in Tregs of patients with autoimmune disorders. Our study identifies the non-oxidative PPP as an integrator of metabolic and epigenetic processes that control Treg function.

2022-03-31 | GSE198995 | GEO

Control of regulatory T cell function by the non-oxidative pentose phosphate pathway [ATAC-seq]

Project description:Non-oxidative pentose phosphate pathway (PPP) is a crucial gatekeeper of glucose catabolism in metabolic tissues. However, its role in regulatory T cells (Tregs) remains unknown. Here we report deleting transketolase (TKT), an indispensable enzyme of non-oxidative PPP, in Tregs caused a fatal auto-immune disease in mice. TKT deletion impaired suppressive capability without disturbing Treg cell number. Mechanistically, TKT deficiency caused Treg metabolic remodeling with decreased glucose catabolism, activated fatty acid and amino acid catabolism and uncontrolled oxidative phosphorylation. Moreover, excessive ammonia from deregulated amino acid catabolism impaired mitochondrial fitness while reduced α-ketoglutarate/succinate ratio led to DNA hypermethylation, limiting functional gene expression and suppressive activity of TKT-deficient Tregs. Therefore, our study identifies non-oxidative PPP as a new pathway for controlling Treg function.

2022-03-31 | GSE172047 | GEO

Control of regulatory T cell function by the non-oxidative pentose phosphate pathway [RNA-Seq]

2022-03-31 | GSE171675 | GEO

The Rax homeoprotein in Müller glial cells is required for homeostasis maintenance of the postnatal mouse retina

Project description:To address the function of Rax in differentiated Müller glial cells, we generated Rax tamoxifen-induced conditional knock-out (Rax iCKO) mice, where Rax can be depleted in mTFP-labeled Müller glial cells upon tamoxifen treatment, by crossing Raxflox/flox mice with Rlbp1-CreERT2 mice and found histological characteristic of reactive gliosis and an enhanced gliosis of Müller glial cells in the Rax iCKO retina under normal and stress conditions, respectively. RNA sequencing using isolated Müller glial cells from the Rax iCKO retina by fluorescence-activated cell sorting demonstrated that reduced expression of suppressor of cytokine signaling-3 (Socs3), whose depletion leads to reactive gliosis in Müller glial cells. Reporter gene assays showed that Rax directly transactivates Socs3 and we observed decreased expression of Socs3 in Müller glial cells of the Rax iCKO retina by immunostaining. Taken together, these results suggest that the Rax homeoprotein suppresses reactive gliosis in Müller glial cells by transactivating Socs3 in vivo. Our results may shed light on the transcriptional regulatory mechanisms underlying Müller glial cell homeostasis.

2023-12-20 | GSE237650 | GEO

A comparative analysis of reactive Müller glia gene expression after light damage and microRNA-depleted Müller glia – focus on microRNAs [NanoString]

Project description:In order to identify the miRNAs in adult light damaged Muller glia of the the neural retina, we isolated the Müller glia from Rlbp-CreER: Stopf/f-tdTomato by means of fluorescent activated cell sorting and analyzed their miRNAs using NanoStrings Technologies®. We compared the data to that from and Dicer1-CKO Müller glia and wild type glia Müller glia (GSE103098). We found three miRNAs potentially regulating genes involved in stress response in both data sets.

2020-12-24 | GSE162993 | GEO

Proteomic phenotyping of stimulated Müller cells uncovers profound pro-inflammatory signaling and antigen-presenting capacity

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

Single cell RNA sequencing unravels the transcriptional network underlying zebrafish retina regeneration

Project description:In the lesioned zebrafish retina, Müller glia produce multipotent retinal progenitors that generate all retinal neurons, replacing lost cell types. To study the molecular mechanisms linking Müller glia reactivity to progenitor production and neuronal differentiation, we used single cell RNA sequencing of Müller glia, progenitors and regenerated progeny from uninjured and light-lesioned retinae. We discover an injury-induced Müller glia differentiation trajectory that leads into a cell population with a hybrid identity expressing marker genes of Müller glia and progenitors. A glial self-renewal and a neurogenic trajectory depart from the hybrid cell population. We further observe that neurogenic progenitors progressively differentiate to generate retinal ganglion cells first and bipolar cells last, similar to the events observed during retinal development. Our work provides a comprehensive description of Müller glia and progenitor transcriptional changes and fate decisions in the regenerating retina, which are key to tailor cell differentiation and replacement therapies for retinal dystrophies in humans.

2023-03-03 | GSE226373 | GEO

ER-stress response in retinal Müller glia occurs significantly earlier than amyloid pathology in in the Alzheimer’s mouse brain and retina

Project description:Alzheimer’s Disease (AD) pathogenesis is thought to begin up to 20 years before cognitive symptoms appear, suggesting the need for more sensitive diagnostic biomarkers of AD. In this report, we demonstrated pathological changes in retinal Müller glia significantly earlier than amyloid pathology in AD mouse models. By utilizing the knock-in NLGF mouse model, we surprisingly discovered an increase in reticulon 3 (RTN3) protein levels in the NLGF retina as early as postnatal day 30 (P30). Despite RTN3 being a canonically neuronal protein, this increase was noted in the retinal Müller glia, confirmed by immunohistochemical characterization. Further unbiased transcriptomic assays of the P30 NLGF retina revealed that retinal Müller glia were the most sensitive responding cells in this mouse retina, compared to other cell types including photoreceptor cells and ganglion neurons. Pathway analyses of differentially expressed genes in glia cells showed activation of ER stress response via the upregulation of unfolded protein response (UPR) proteins such as ATF4 and CHOP. Early elevation of RTN3 in response to challenges by toxic Aβ likely facilitated UPR. Altogether, these findings suggest that Müller glia act as a sentinel for AD pathology in the retina and should aid for both intervention and diagnosis.

2024-04-17 | GSE254524 | GEO

Transcriptome and DNA methylome of mouse Müller glia

Project description:Müller cells are the primary glia of the neural retina and play crucial roles in maintaining the structural and functional homeostasis of the retina. Müller cells also possess certain levels of retinal regeneration capacity, especially in lower vertebrates. In this study, we deep sequenced the transcriptomes and methylomes of mouse Müller cells and early retinal progenitor cells (RPCs), as well as Müller cells from injured retinas and aged retinas, which will help to reveal molecular mechanisms governing Müller cells development, physiological functions and regeneration activities.

2019-11-12 | GSE124532 | GEO

The role of retinol dehydrogenase 10 in the retina visual cycle

Project description:Pigment regeneration is critical for the function of cone photoreceptors in bright and rapidly-changing light conditions. This process is facilitated by the recently-characterized retina visual cycle, in which Müller cells recycle spent all-trans-retinol visual chromophore back to 11-cis-retinol. This 11-cis-retinol is oxidized selectively in cones to the 11-cis-retinal used for pigment regeneration. However, the enzyme responsible for the oxidation of 11-cis-retinol remains unknown. Here, we sought to determine whether retinol dehydrogenase 10 (RDH10), upregulated in rod/cone hybrid retinas and expressed abundantly in Müller cells, is the enzyme that drives this reaction. We created mice lacking RDH10 either in cone photoreceptors, Müller cells, or the entire retina. In vivo electroretinography and transretinal recordings revealed normal cone photoresponses in all RDH10-deficient mouse lines. Notably, their cone-driven dark adaptation both in vivo and in isolated retina was unaffected, indicating that RDH10 is not required for the function of the retina visual cycle. We also generated transgenic mice expressing RDH10 ectopically in rod cells. However, rod dark adaptation was unaffected by the expression of RDH10 and transgenic rods were unable to use cis-retinol for pigment regeneration. We conclude that RDH10 is not the dominant retina 11-cis-RDH, leaving its primary function in the retina unknown.

2017-03-07 | GSE86442 | GEO

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