GLUD1 Research Articles

GDH1-dependent α-ketoglutarate promotes HBV transcription by modulating histone methylations on the cccDNA minichromosome.

Hepatitis B virus (HBV) hijacks host cell metabolism, especially host glutamine metabolism, to support its replication. Glutamate dehydrogenase 1 (GDH1), a mitochondrial enzyme crucial for glutamine metabolism, can interact with histone demethylases to regulate gene expression through histone methylation. However, the mechanisms underlying GDH1-mediated glutamine metabolism reprogramming and the roles of key metabolites during HBV infection remain unclear. Transcriptomic and metabolomic analyses of HBV-infected cell were performed. Both HBV-infected cells and humanized liver chimeric mice were used to elucidate the effect of glutamine metabolism on HBV. HBV infection leads to the abnormal activation of glutamine metabolism, including upregulation of key enzymes and metabolites involved in glutamine metabolism. The viral core protein (HBc) mediates the translocation of GDH1 into the nucleus, where GDH1 activates covalently closed circular DNA (cccDNA) transcription by converting glutamate to α-ketoglutarate (αKG). Mechanistically, the promoting effect of GDH1-derived αKG on cccDNA transcription is independent of its conventional role. Rather, αKG directly interacts with the lysine-specific demethylase KDM4A and enhances KDM4A demethylase activity to regulate αKG-dependent histone demethylation, controlling cccDNA transcription. Our findings highlight the importance of glutamine metabolism in HBV transcription and suggest that glutamine deprivation is a potential strategy for silencing cccDNA transcription.

Moxibustion Alleviates Inflammation via SIRT5-mediated Post-translational Modification and Macrophage Polarization.

Macrophage polarisation is influenced by Sirtuin5 (SIRT5), which is crucial for regulating anti-inflammatory processes. Moxibustion, a traditional Chinese medicine therapy, exerts anti-inflammatory effects by altering the succinate/α-ketoglutarate (α-KG) ratio, an indicator of the M1 to M2 macrophage shift. Glutamate dehydrogenase 1 (GLUD1), a key enzyme involved in α-KG production, is desuccinylated by SIRT5. Currently, the potential influence of moxibustion on SIRT5-GLUD1-α-KG-mediated macrophage polarization in inflammatory diseases remains unexplored. C57BL/6J and Sirt5 knockout mice were used as complete Freund's adjuvant (CFA)-induced adjuvant arthritis models. Moxibustion and acupoint injections of MC3482 were administered. Paw capacity asssays and ELISA were performed to quantify inflammatory effects and the expression of succinate, and α-KG expressions. Flow cytometry (FCM) and immunofluorescence were used to assesss the expression of M1- and M2-like macrophages. LC-MS/MS-based proteomic analysis was performed, and GLUD1 was identified desuccinylated protein associated with SIRT5. Western blotting and immunoprecipitation (IP) were used to detect SIRT5, GLUD1, and succinylated GLUD1expressions. Moxibustion and the SIRT5-mediated desuccinylation inhibitor MC3482 decreased inflammation by increasing the number of M2 macrophages and reducing the number of M1 macrophage in the CFA model. The potential mechanism may be related to the effects of moxibustion and SIRT5 inhibition, which inverted succinate and α-KG levels in the CFA group, resulting in low succinate, high α-KG, and increased GLUD1 succinylation after treatment. These findings suggest that the anti-inflammatory effects moxibustion are related to the impact of macrophage conversion after SIRT5-mediated post-translational modification.

Metabolic checkpoints in rheumatoid arthritis

Rheumatoid Arthritis is a systemic autoimmune disease affecting 0.5-1 % of the population. Despite a growing therapeutic armamentarium, RA remains incurable, and many patients suffer significant morbidity over time. The strongest genetic risk derives from HLA class II polymorphisms, implicating T cells as pathogenic drivers. Innate immune cells, e.g. monocytes and macrophages (Mⱷ) contribute to chronic tissue inflammation through an array of pro-inflammatory functions but also present antigen to autoreactive T cells. Differentiation, survival, and effector functions of both T cells and Mⱷ are ultimately controlled by their bioenergetic and biosynthetic programs, identifying cellular metabolism as a critical disease mechanism in RA. Summarize current knowledge about metabolic conditions in the RA joint and disease-relevant metabolic circuits shaping the effector repertoire of RA T cells and Mⱷ. The rheumatoid joint is a glucose deplete tissue environment, selecting for invading immune cells that can survive on non-glucose fuel sources. Inflamed synovium instead offers the amino acid glutamine and RA CD4+ T cells and RA Mⱷ rely on glutamine and glutamate to support their pathogenic functions. The metabolic hallmark of RA T cells is their low mitochondrial performance, resulting in low ATP production, low generation of reactive oxygen species (ROS) and low availability of tricarboxylic acid (TCA) cycle intermediates, all shifting RA T cells towards autoreactivity. The underlying defect stems from insufficient repair of mitochondrial DNA (mtDNA). Functional consequences include reversal of the TCA cycle, accumulation of citrate and lack of malate production. Excessive citrate promotes cytoskeletal hyperacetylation, creating hypermigratory and tissue-invasive T cells. Surplus acetyl-CoA supports lipid droplet formation and lipotoxicity. Lack of malate production disrupts the malate-aspartate shuttle, restricts recovery of cytosolic NAD and drives the endoplasmic reticulum (ER) into expansion. The bioenergetically stressed ER accumulates TNF mRNA and turns RA T cells into TNF superproducers. ATP low production renders RA T cells susceptible to cell death, depositing highly inflammatory mtDNA in the tissue. Mitochondrial deficiency leads to a slowdown in glycolysis and pyruvate processing, such that RA CD4+ T cells shunt glucose towards the pentose phosphate pathway to support nucleotide synthesis and clonal proliferation. Metabolically deprived CD4+ T cells partner with Mⱷ that have highly functional mitochondria. A hallmark of RA Mⱷ is the high expression of the DNA binding protein RFX5, which co-ordinates adaptations to metabolic needs with function. RFX5 upregulates HLA-DR expression and induces the glutaminolytic enzyme glutamate dehydrogenase 1 (GLUD1), providing bioenergetic resources for antigen presentation and survival in the tissue. In essence, RA CD4+ T cells and Mⱷ function in a metabolically challenging environment and rewire their cellular metabolism to survive. Metabolic adaptations promote immunostimulation and tissue inflammation, triggering and sustaining rheumatoid synovitis.

Deacetylation of GLUD1 maintains the survival of lung adenocarcinoma cells under glucose starvation by inhibiting autophagic cell death

Enhanced glutamine catabolism is one of the main metabolic features of cancer, providing energy and intermediate metabolites for cancer progression. However, the functions of glutamine catabolism in cancer under nutrient deprivation need to be further clarified. Here, we discovered that deacetylation of glutamate dehydrogenase 1 (GLUD1), one of the key enzymes in glutamine catabolism, maintains the survival of lung adenocarcinoma (LUAD) cells under glucose starvation by inhibiting autophagic cell death. We found that glucose starvation increased GLUD1 activity by reducing its acetylation on Lys84 and promoted its active hexamer formation. Besides, deacetylation of GLUD1 induced its cytoplasmic localization, where GLUD1 was ubiquitinated in K63-linkage by TRIM21, leading to the binding of GLUD1 with cytoplasmic glutaminase KGA. These two effects enhanced glutamine metabolism both in mitochondria and cytoplasm, increased the production of alpha-ketoglutarate (α-KG). Meanwhile, cytoplasmic GLUD1 also interacted with p62 and prevented its acetylation, leading to the inhibition of p62 body formation. All these effects blocked autophagic cell death of LUAD cells under glucose starvation. Taken together, our results reveal a novel function of GLUD1 under glucose deprivation in LUAD cells and provide new insights into the functions of glutamine catabolism during cancer progression.

BET inhibition induces GDH1-dependent glutamine metabolic remodeling and vulnerability in liver cancer.

Bromodomain and extra-terminal domain (BET) proteins, which function partly through MYC proto-oncogene (MYC), are critical epigenetic readers and emerging therapeutic targets in cancer. Whether and how BET inhibition simultaneously induces metabolic remodeling in cancer cells remains unclear. Here we find that even transient BET inhibition by JQ-1 and other pan-BET inhibitors (pan-BETis) blunts liver cancer cell proliferation and tumor growth. BET inhibition decreases glycolytic gene expression but enhances mitochondrial glucose and glutamine oxidative metabolism revealed by metabolomics and isotope labeling analysis. Specifically, BET inhibition downregulates miR-30a to upregulate glutamate dehydrogenase 1 (GDH1) independent of MYC, which produces α-ketoglutarate for mitochondrial oxidative phosphorylation (OXPHOS). Targeting GDH1 or OXPHOS is synthetic lethal to BET inhibition, and combined BET and OXPHOS inhibition therapeutically prevents liver tumor growth in vitro and in vivo. Together, we uncover an important epigenetic-metabolic crosstalk whereby BET inhibition induces MYC-independent and GDH1-dependent glutamine metabolic remodeling that can be exploited for innovative combination therapy of liver cancer.

Functional synergy of a human-specific and an ape-specific metabolic regulator in human neocortex development

Metabolism has recently emerged as a major target of genes implicated in the evolutionary expansion of human neocortex. One such gene is the human-specific gene ARHGAP11B. During human neocortex development, ARHGAP11B increases the abundance of basal radial glia, key progenitors for neocortex expansion, by stimulating glutaminolysis (glutamine-to-glutamate-to-alpha-ketoglutarate) in mitochondria. Here we show that the ape-specific protein GLUD2 (glutamate dehydrogenase 2), which also operates in mitochondria and converts glutamate-to-αKG, enhances ARHGAP11B’s ability to increase basal radial glia abundance. ARHGAP11B + GLUD2 double-transgenic bRG show increased production of aspartate, a metabolite essential for cell proliferation, from glutamate via alpha-ketoglutarate and the TCA cycle. Hence, during human evolution, a human-specific gene exploited the existence of another gene that emerged during ape evolution, to increase, via concerted changes in metabolism, progenitor abundance and neocortex size.

Evolutionary Changes in Primate Glutamate Dehydrogenases 1 and 2 Influence the Protein Regulation by Ligands, Targeting and Posttranslational Modifications.

There are two paralogs of glutamate dehydrogenase (GDH) in humans encoded by the GLUD1 and GLUD2 genes as a result of a recent retroposition during the evolution of primates. The two human GDHs possess significantly different regulation by allosteric ligands, which is not fully characterized at the structural level. Recent advances in identification of the GDH ligand binding sites provide a deeper perspective on the significance of the accumulated substitutions within the two GDH paralogs. In this review, we describe the evolution of GLUD1 and GLUD2 after the duplication event in primates using the accumulated sequencing and structural data. A new gibbon GLUD2 sequence questions the indispensability of ancestral R496S and G509A mutations for GLUD2 irresponsiveness to GTP, providing an alternative with potentially similar regulatory features. The data of both GLUD1 and GLUD2 evolution not only confirm substitutions enhancing GLUD2 mitochondrial targeting, but also reveal a conserved mutation in ape GLUD1 mitochondrial targeting sequence that likely reduces its transport to mitochondria. Moreover, the information of GDH interactors, posttranslational modification and subcellular localization are provided for better understanding of the GDH mutations. Medically significant point mutations causing deregulation of GDH are considered from the structural and regulatory point of view.

Inhibition of GLUD1 mediated by LASP1 and SYVN1 contributes to hepatitis B virus X protein-induced hepatocarcinogenesis.

Glutamate dehydrogenase 1 (GLUD1) is implicated in oncogenesis. However, little is known about the relationship between GLUD1 and hepatocellular carcinoma (HCC). In the present study, we demonstrated that the expression levels of GLUD1 significantly decreased in tumors, which was relevant to the poor prognosis of HCC. Functionally, GLUD1 silencing enhanced the growth and migration of HCC cells. Mechanistically, the upregulation of interleukin-32 through AKT activation contributes to GLUD1 silencing-facilitated hepatocarcinogenesis. The interaction between GLUD1 and AKT, as well as α-ketoglutarate regulated by GLUD1, can suppress AKT activation. In addition, LIM and SH3 protein 1 (LASP1) interacts with GLUD1 and induces GLUD1 degradation via the ubiquitin-proteasome pathway, which relies on the E3 ubiquitin ligase synoviolin (SYVN1), whose interaction with GLUD1 is enhanced by LASP1. In hepatitis B virus (HBV)-related HCC, the HBV X protein (HBX) can suppress GLUD1 with the participation of LASP1 and SYVN1. Collectively, our data suggest that GLUD1 silencing is significantly associated with HCC development, and LASP1 and SYVN1 mediate the inhibition of GLUD1 in HCC, especially in HBV-related tumors.

Bioinformatics analysis identifies GLUD1 as a prognostic indicator for clear cell renal cell carcinoma

BackgroundRenal cell carcinoma (RCC) is a common primary tumor of the kidney and is divided into three major subtypes, of which clear cell renal cell carcinoma (ccRCC) has the highest incidence. Glutamate dehydrogenase 1 (GLUD1) encodes glutamate dehydrogenase 1, which catalyzes the oxidative deamination of glutamate.MethodsWe analyzed TCGA data using R language software and used multiple online databases to explore the relationship of GLUD1 with signaling pathways and drug sensitivity as well as GLUD1 protein expression and methylation.ResultsThe results showed that GLUD1 mRNA expression was reduced in tumor tissues and correlated with the progression of ccRCC. Univariate and multivariate Cox analysis showed that GLUD1 could be used as a prognostic marker for ccRCC. GLUD1 expression in ccRCC was associated with immune cells infiltration and multiple classical signaling pathways. In addition, GLUD1 mRNA expression was related to drug sensitivity.ConclusionsThese findings provide new ideas for finding new prognostic molecular markers and therapeutic targets for ccRCC.

GLUD1 inhibits hepatocellular carcinoma progression via ROS-mediated p38/JNK MAPK pathway activation and mitochondrial apoptosis

Glutamate dehydrogenase 1 (GLUD1) is an important enzyme in glutamine metabolism. Previously, we found GLUD1 was down-regulated in tumor tissues of hepatocellular carcinoma (HCC) patients by proteomics study. To explore its role in the progression of HCC, the expressional level of GLUD1 was firstly examined and presented as that both the protein and mRNA levels were down-regulated in tumor tissues compared to the normal liver tissues. GLUD1 overexpression significantly inhibited HCC cells proliferation, migration, invasion and tumor growth both in vitro and in vivo, while GLUD1 knocking-down promoted HCC progression. Metabolomics study of GLUD1 overexpressing and control HCC cells showed that 129 differentially expressed metabolites were identified, which mainly included amino acids, bases, and phospholipids. Moreover, metabolites in mitochondrial oxidative phosphorylation system (OXPHOS) were differentially expressed in GLUD1 overexpressing cells. Mechanistic studies showed that GLUD1 overexpression enhanced mitochondrial respiration activity and reactive oxygen species (ROS) production. Excessive ROS lead to mitochondrial apoptosis that was characterized by increased expression levels of p53, Cytochrome C, Bax, Caspase 3 and decreased expression level of Bcl-2. Furthermore, we found that the p38/JNK MAPK pathway was activated in GLUD1 overexpressing cells. N-acetylcysteine (NAC) treatment eliminated cellular ROS and blocked p38/JNK MAPK pathway activation, as well as cell apoptosis induced by GLUD1 overexpression. Taken together, our findings suggest that GLUD1 inhibits HCC progression through regulating cellular metabolism and oxidative stress state, and provide that ROS generation and p38/JNK MAPK pathway activation as promising methods for HCC treatment.

IDH2 and GLUD1 depletion arrests embryonic development through an H4K20me3 epigenetic barrier in porcine parthenogenetic embryos.

Isocitrate dehydrogenase 2 (IDH2) and glutamate dehydrogenase 1 (GLUD1) are key enzymes involved in the production of α-ketoglutarate (α-KG), a metabolite central to the tricarboxylic acid cycle and glutamine metabolism. In this study, we investigated the impact of IDH2 and GLUD1 on early porcine embryonic development following IDH2 and GLUD1 knockdown (KD) via double-stranded RNA (dsRNA) microinjection. Results showed that KD reduced α-KG levels, leading to delayed embryonic development, decreased blastocyst formation, increased apoptosis, reduced blastomere proliferation, and pluripotency. Additionally, IDH2 and GLUD1 KD induced abnormally high levels of trimethylation of lysine 20 of histone H4 (H4K20me3) at the 4-cell stage, likely resulting in transcriptional repression of embryonic genome activation (EGA)-related genes. Notably, KD of lysine methyltransferase 5C ( KMT5C) and supplementation with exogenous α-KG reduced H4K20me3 expression and partially rescued these defects, suggesting a critical role of IDH2 and GLUD1 in the epigenetic regulation and proper development of porcine embryos. Overall, this study highlights the significance of IDH2 and GLUD1 in maintaining normal embryonic development through their influence on α-KG production and subsequent epigenetic modifications.

Non‐surgical Treatment May be Appropriate for Most Chinese Children With Monogenic Congenital Hyperinsulinism Based on a Retrospective Study of 121 Patients

Objective: There is a notable absence of extensive Chinese studies involving monogenic congenital hyperinsulinism (CHI). The purpose of this large retrospective Chinese cohort with monogenic CHI from a national children’s medical center was to analyze the genetic and clinical characteristics.Methods: We compared clinical characteristics grouped by genotypes based on CHI‐targeted next‐generation sequencing (tNGS) and performed subgroup analyses by onset time.Results: Totally, 121 non‐consanguineous patients were enrolled. Among them, 79 patients (65.3%) had variants in ATP‐sensitive potassium channel (KATP) genes (62 heterozygotes and 17 compound heterozygotes), 35 (28.9%) in glutamate dehydrogenase 1 (GLUD1), and 7 (5.8%) in rare genes (hydroxyacyl‐CoA dehydrogenase [HADH], glucokinase [GCK], and hepatocyte nuclear factor 4 alpha [HNF4A]). Ten patients had ATP binding cassette subfamily C member 8 (ABCC8) variants (p.G111R), and 12 had GLUD1 variants (p.S498L), suggesting two potential founder variants. Three ABCC8 variants (p.G1478R, p.L580_S581insFASL, and p.S986 ∗) and two HNF4A variants (p.R63W and p.V382I) were previously reported to be associated with diabetes. Non‐surgical treatment was effective in 65.9% of patients with KATP variants, while in 100% of those with non‐KATP variants. For the subgroup of KATP variants, neonatal‐onset patients tended to present with mild symptoms (67.9% versus 19.3%), had a higher proportion of surgical intervention (24.5% versus 3.8%), and displayed higher levels of serum insulin and C‐peptide than non‐neonatal onset ones (p < 0.001).Conclusion: The absence of homozygous variants in KATP genes and a quite higher proportion of GLUD1 variants than previous cohorts, may explain a high response rate of non‐surgical treatment in this study. Surgery might be considered for neonatal‐onset children, especially when KATP variants were discovered but not for those carried variants reported to cause diabetes in later life. While expanding the genotypic spectrum, we also highlight the clinical significance of genetic screening.

Structural Evolution of Primate Glutamate Dehydrogenase 2 as Revealed by In Silico Predictions and Experimentally Determined Structures.

Glutamate dehydrogenase (GDH) interconverts glutamate to a-ketoglutarate and ammonia, interconnecting amino acid and carbohydrate metabolism. In humans, two functional GDH genes, GLUD1 and GLUD2, encode for hGDH1 and hGDH2, respectively. GLUD2 evolved from retrotransposition of the GLUD1 gene in the common ancestor of modern apes. These two isoenzymes are involved in the pathophysiology of human metabolic, neoplastic, and neurodegenerative disorders. The 3D structures of hGDH1 and hGDH2 have been experimentally determined; however, no information is available about the path of GDH2 structure changes during primate evolution. Here, we compare the structures predicted by the AlphaFold Colab method for the GDH2 enzyme of modern apes and their extinct primate ancestors. Also, we analyze the individual effect of amino acid substitutions emerging during primate evolution. Our most important finding is that the predicted structure of GDH2 in the common ancestor of apes was the steppingstone for the structural evolution of primate GDH2s. Two changes with a strong functional impact occurring at the first evolutionary step, Arg443Ser and Gly456Ala, had a destabilizing and stabilizing effect, respectively, making this step the most important one. Subsequently, GDH2 underwent additional modifications that fine-tuned its enzymatic properties to adapt to the functional needs of modern-day primate tissues.

Polymorphism and expression of GLUD1 in relation to reproductive performance in Jining Grey goats.

Understanding the molecular mechanism of mammalian reproduction (puberty and prolificacy) will play a part in improving animal reproductive performance. GLUD1 (glutamate dehydrogenase1) is important for mammalian reproduction, as shown in previous studies; however, its roles in puberty and prolificacy have rarely been reported. In this study, we designed seven pairs of primers (P1 to P7) for cloning and sequencing genomic DNA of Jining Grey goats and Liaoning Cashmere goats. Primer8 (P8) was designed to detect single nucleotide polymorphism (SNP) of the GLUD1 in both sexually precocious and high-fecundity breeds (Jining Grey, Nanjiang Brown and Matou goats) and sexually late-maturing and low-fecundity breeds (Liaoning Cashmere, Inner Mongolia Cashmere and Taihang goats) by PCR-RFLP (restriction fragment length polymorphism). The real-time quantitative polymerase chain reaction (RT-qPCR) technique was used to detect the expression of GLUD1 in a variety of tissues. The results showed that the A197C mutation was only found in the amplification product of P6. For this SNP locus, only two genotypes (AA and AC) were detected in Nanjiang Brown goats, while three genotypes (AA, AC and CC) were detected in the other five breeds. In Jining Grey goats, the frequency of genotypes AA, AC and CC was 0.69, 0.26 and 0.05, respectively. In Jining Grey goats, AA genotype had 0.54 () and 0.3 () more kids than the CC and AC genotype, respectively, and no significant difference () was found in kidding number between the AC and CC genotype. GLUD1 was expressed in five tissues of different developmental stages. The expression level of GLUD1 in the hypothalamus was higher than that in the other four tissues except during puberty of Liaoning Cashmere goats. In puberty in goats, GLUD1 expression was significantly higher in ovaries than that in the juvenile period (). RT-qPCR results showed that the expression of GLUD1 in ovaries may relate to the puberty of goats. The present study preliminarily indicated that there might be an association between the 197 locus of GLUD1 and sexual precocity in goats, and allele A of GLUD1 was a potential DNA marker for improving kidding number in Jining Grey goats.

Genetic polymorphism of high-molecular-weight glutenin subunit loci in bread wheat varieties in the Pre-Ural steppe zone.

High-molecular-weight glutenins play an important role in providing high baking qualities of bread wheat grain. However, breeding bread wheat for this trait is very laborious and, therefore, the genotyping of variety samples according to the allelic composition of high-molecular-weight glutenin genes is of great interest. The aim of the study was to determine the composition of high-molecular-weight glutenin subunits based on the identification of the allelic composition of the Glu-1 genes, as well as to identify the frequency of the Glu-1 alleles in bread wheat cultivars that are in breeding work under the conditions of the Pre-Ural steppe zone (PSZ). We analyzed 26 winter and 22 spring bread wheat varieties from the PSZ and 27 winter and 20 spring varieties from the VIR collection. Genotyping at the Glu-A1 locus showed that the Ax1 subunits are most common in winter varieties, while the predominance of the Ax2* subunits was typical of spring varieties and lines. In the Glu-B1 locus, the predominance of alleles associated with the production of the Bx7 and By9 subunits was revealed for both winter and spring varieties. In the case of the Glu-D1 gene, for all the wheat groups studied, the composition of the Dx5+Dy10 subunits was the most common: in 92.3 % of winter and 68.2 % of spring PSZ accessions and in 80 % of winter and 55 % of spring VIR accessions. The analysis of genotypes showed the presence of 13 different allelic combinations of the Glu-A1, Glu-B1, Glu-D1 genes in the PSZ varieties, and 19 combinations in the VIR varieties. The b b/al/с d allelic combination (Ax2* Вх7+Ву8/8*/9 Dx5+Dy10) turned out to be the most common for the PSZ spring varieties and lines, while for the PSZ winter accessions it was a с d (Ax1 Вх7+By9 Dx5+Dy10); the b с a and b с d genotypes (Ax2* Вх7+Ву9 Dx2+Dy12 and Ax2* Вх7+Ву9 Dx5+Dy10, respectively) occur with equal frequency among the VIR spring accessions; in the group of VIR winter varieties, the combination of the a b/ al d alleles (Ax1 Вх7+Ву8/8* Dx5+Dy10) prevails. The most preferred combination of alleles for baking qualities was found in the spring variety 'Ekaterina' and winter varieties 'Tarasovskaya 97', 'Volzhskaya S3', as well as in lines k-58164, L43510, L43709, L-67, L-83, which are recommended for further breeding programs to improve and preserve baking qualities in the conditions of the Pre-Ural steppe zone.

The Key Role of Glutamate Dehydrogenase 2 (GDH2) in the Control of Kernel Production in Maize (Zea mays L.).

The agronomic potential of glutamate dehydrogenase 2 (GDH2) in maize kernel production was investigated by examining the impact of a mutation on the corresponding gene. Mu-insertion homozygous and heterozygous mutant lines lacking GDH2 activity were isolated and characterized at the biochemical, physiological and agronomic levels. In comparison to the wild type and to the homozygous ghd2 mutants, the heterozygous gdh2 mutant plants were characterized by a decrease in the root amino acid content, whereas in the leaves an increase of a number of phenolic compounds was observed. On average, a 30 to 40% increase in kernel yield was obtained only in the heterozygous gdh2 mutant lines when plants were grown in the field over two years. The importance of GDH2 in the control of plant productivity is discussed in relation to the physiological impact of the mutation on amino acid content, with primary carbon metabolism mostly occurring in the roots and secondary metabolism occurring in the leaves.

STUB1-mediated ubiquitination regulates the stability of GLUD1 in lung adenocarcinoma

The dysregulation of glutamine metabolism provides survival advantages for tumors by supplementing tricarboxylic acid cycle. Glutamate dehydrogenase 1 (GLUD1) is one of the key enzymes in glutamine catabolism. Here, we found that enhanced protein stability was the key factor for the upregulation of GLUD1 in lung adenocarcinoma. We discovered that GLUD1 showed a high protein expression in lung adenocarcinoma cells or tissues. We elucidated that STIP1 homology and U-box-containing protein 1 (STUB1) was the key E3 ligase responsible for ubiquitin-mediated proteasomal degradation of GLUD1. We further showed that lysine 503 (K503) was the main ubiquitination site of GLUD1, inhibiting the ubiquitination at this site promoted the proliferation and tumor growth of lung adenocarcinoma cells. Taken together, this study clarifies the molecular mechanism of GLUD1 in maintaining protein homeostasis in lung adenocarcinoma, which provides a theoretical basis for the development of anti-cancer drugs targeting GLUD1.

Glutamate dehydrogenase 1: A novel metabolic target in inhibiting acute myeloid leukaemia progression.

Glutamine metabolic reprogramming in acute myeloid leukaemia (AML) cells contributes to the decreased sensitivity to antileukemic drugs. Leukaemic cells, but not their myeloid counterparts, largely depend on glutamine. Glutamate dehydrogenase 1 (GDH1) is a regulation enzyme in glutaminolysis. However, its role in AML remains unknown. Here, we reported that GDH1 was highly expressed in AML: high GDH1 was one of the independent negative prognostic factors in AML cohort. The dependence of leukaemic cells on GDH1 was proved both in vitro and in vivo. High GDH1 promoted cell proliferation and reduced survival time of leukaemic mice. Targeting GDH1 eliminated the blast cells and delayed AML progression. Mechanistically, GDH1 knockdown inhibited glutamine uptake by downregulating SLC1A5. Moreover, GDH1 invalidation also inhibited SLC3A2 and abrogated the cystine-glutamate antiporter system Xc- . The reduced cystine and glutamine disrupted the synthesis of glutathione (GSH) and led to the dysfunction of glutathione peroxidase-4 (GPX4), which maintains the lipid peroxidation homeostasis by using GSH as a co-factor. Collectively, triggering ferroptosis in AML cells in a GSH depletion manner, GDH1 inhibition was synthetically lethal with the chemotherapy drug cytarabine. Ferroptosis induced by inhibiting GDH1 provides an actionable therapeutic opportunity and a unique target for synthetic lethality to facilitate the elimination of malignant AML cells.

Identification of dual-purpose therapeutic targets implicated in aging and glioblastoma multiforme using PandaOmics - an AI-enabled biological target discovery platform

Glioblastoma Multiforme (GBM) is the most aggressive and most common primary malignant brain tumor. The age of GBM patients is considered as one of the disease's negative prognostic factors and the mean age of diagnosis is 62 years. A promising approach to preventing both GBM and aging is to identify new potential therapeutic targets that are associated with both conditions as concurrent drivers. In this work, we present a multi-angled approach of identifying targets, which takes into account not only the disease-related genes but also the ones important in aging. For this purpose, we developed three strategies of target identification using the results of correlation analysis augmented with survival data, differences in expression levels and previously published information of aging-related genes. Several studies have recently validated the robustness and applicability of AI-driven computational methods for target identification in both cancer and aging-related diseases. Therefore, we leveraged the AI predictive power of the PandaOmics TargetID engine in order to rank the resulting target hypotheses and prioritize the most promising therapeutic gene targets. We propose cyclic nucleotide gated channel subunit alpha 3 (CNGA3), glutamate dehydrogenase 1 (GLUD1) and sirtuin 1 (SIRT1) as potential novel dual-purpose therapeutic targets to treat aging and GBM.

Glutamate dehydrogenase1 supports HIF-1α stability to promote colorectal tumorigenesis under hypoxia.

Tumor cells surviving hypoxic stress acquire the ability to drive cancer progression. To explore the contribution of dehydrogenases to the low oxygen concentration response, we used siRNAs targeting 163 dehydrogenase-coding genes and discovered that glutamate dehydrogenase 1 (GDH1) plays a critical role in regulating colorectal cancer (CRC) cell survival under hypoxia. We observed that GDH1 deficiency had an inhibitory effect on CRC occurrence and impaired hypoxia-inducible factor 1-alpha (HIF-1α) stability even under hypoxia. Mechanistically, hypoxia triggered p300 recruitment to GDH1, promoting its acetylation at K503 and K527. GDH1 acetylation at K527 induced the formation of a GDH1 complex with EGLN1/HIF-1α; in contrast, GDH1 acetylation at K503 reinforced its affinity for α-ketoglutarate (αKG), and glutamate production. In line with this view, αKG is a product of GDH1 under normoxia, but hypoxia stimulation reversed GDH1 enzyme activity and αKG consumption by the EGLN1/HIF-1α complex, increasing HIF-1α stability and promoting CRC progression. Clinically, hypoxia-modulated GDH1 AcK503/527 can be used as a biomarker of CRC progression and is a potential target for CRC treatment.