Expression and role in glycolysis of human ADP-dependent glucokinase

Cortisol affects macrophage polarization by inducing miR-143/145 cluster to reprogram glucose metabolism and by promoting TCA cycle anaplerosis

Chronic stress can have adverse consequences on human health by disrupting the hormonal balance in our body. Earlier, we observed elevated levels of cortisol, a primary stress hormone, and some exosomal microRNAs in the serum of patients with breast cancer. Here, we investigated the role of cortisol in microRNA induction and its functional consequences. We found that cortisol induced the expression of miR-143/145 cluster in human monocyte (THP1 and U937)-derived macrophages but not in breast cancer cells. In silico analysis identified glucocorticoid-response element in the upstream CARMN promoter utilized by the miR-143/145 cluster. Enhanced binding of glucocorticoid-receptor (GR) upon cortisol exposure and its regulatory significance was confirmed by chromatin-immunoprecipitation and promoter-reporter assays. Further, cortisol inhibited IFNγ-induced M1 polarization and promoted M2 polarization, and these effects were suppressed by miR-143-3p and miR-145-5p inhibitors pretreatment. Cortisol-treated macrophages exhibited increased oxygen-consumption rate (OCR) to extracellular-acidification rate (ECAR) ratio, and this change was neutralized by functional inhibition of miR-143-3p and miR-145-5p. HK2 and ADPGK were confirmed as the direct targets of miR-143-3p and miR-145-5p, respectively. Interestingly, silencing of HK2 and ADPGK inhibited IFNγ-induced M1 polarization but failed to induce M2 polarization, since it suppressed both ECAR and OCR, while OCR was largely sustained in cortisol-treated M2-polarized macrophages. We found that cortisol treatment sustained OCR by enhancing fatty acid and glutamine metabolism through upregulation of CPT2 and GLS, respectively, to support M2 polarization. Thus, our findings unfold a novel mechanism of immune suppression by cortisol and open avenues for preventive and therapeutic interventions.

Current status and progress of research on the ADP-dependent glucokinase gene

ADP-dependent glucokinase (ADPGK) produces glucose-6-phosphate with adenosine diphosphate (ADP) as the phosphate group donor, in contrast to ATP-dependent hexokinases (HKs). Originally found in archaea, ADPGK is involved in glycolysis. However, its biological function in most eukaryotic organisms is still unclear, and the molecular mechanism of action requires further investigation. This paper provides a concise overview of ADPGK's origin, biological function and clinical application. It aims to furnish scientific information for the diagnosis and treatment of human metabolic diseases, neurological disorders, and malignant tumours, and to suggest new strategies for the development of targeted drugs.

ADP-dependent glucokinase controls metabolic fitness in prostate cancer progression

BACKGROUND

Cell metabolism plays a pivotal role in tumor progression, and targeting cancer metabolism might effectively kill cancer cells. We aimed to investigate the role of hexokinases in prostate cancer (PCa) and identify a crucial target for PCa treatment.

METHODS

The Cancer Genome Atlas (TCGA) database, online tools and clinical samples were used to assess the expression and prognostic role of ADP-dependent glucokinase (ADPGK) in PCa. The effect of ADPGK expression on PCa cell malignant phenotypes was validated in vitro and in vivo. Quantitative proteomics, metabolomics, and extracellular acidification rate (ECAR) and oxygen consumption rate (OCR) tests were performed to evaluate the impact of ADPGK on PCa metabolism. The underlying mechanisms were explored through ADPGK overexpression and knockdown, co-immunoprecipitation (Co-IP), ECAR analysis and cell counting kit-8 (CCK-8) assays.

RESULTS

ADPGK was the only glucokinase that was both upregulated and predicted worse overall survival (OS) in prostate adenocarcinoma (PRAD). Clinical sample analysis demonstrated that ADPGK was markedly upregulated in PCa tissues vs. non-PCa tissues. High ADPGK expression indicates worse survival outcomes, and ADPGK serves as an independent factor of biochemical recurrence. In vitro and in vivo experiments showed that ADPGK overexpression promoted PCa cell proliferation and migration, and ADPGK inhibition suppressed malignant phenotypes. Metabolomics, proteomics, and ECAR and OCR tests revealed that ADPGK significantly accelerated glycolysis in PCa. Mechanistically, ADPGK binds aldolase C (ALDOC) to promote glycolysis via AMP-activated protein kinase (AMPK) phosphorylation. ALDOC was positively correlated with ADPGK, and high ALDOC expression was associated with worse survival outcomes in PCa.

CONCLUSIONS

In summary, ADPGK is a driving factor in PCa progression, and its high expression contributes to a poor prognosis in PCa patients. ADPGK accelerates PCa glycolysis and progression by activating ALDOC-AMPK signaling, suggesting that ADPGK might be an effective target and marker for PCa treatment and prognosis evaluation.

Kinetic characterization and phylogenetic analysis of human ADP-dependent glucokinase reveal new insights into its regulatory properties

Although ADP-dependent sugar kinases were first described in archaea, at present, the presence of an ADP-dependent glucokinase (ADP-GK) in mammals is well documented. This enzyme is mainly expressed in hematopoietic lineages and tumor tissues, although its role has remained elusive. Here, we report a detailed kinetic characterization of the human ADP-dependent glucokinase (hADP-GK), addressing the influence of a putative signal peptide for endoplasmic reticulum (ER) destination by characterizing a truncated form. The truncated form revealed no significant impact on the kinetic parameters, showing only a slight increase in the Vmax value, higher metal promiscuity, and the same nucleotide specificity as the full-length enzyme. hADP-GK presents an ordered sequential kinetic mechanism in which MgADP is the first substrate to bind and AMP is the last product released, being the same mechanism described for archaeal ADP-dependent sugar kinases, in agreement with the protein topology. Substrate inhibition by glucose was observed due to sugar binding to nonproductive species. Although Mg²⁺ is an essential component for kinase activity, it also behaves as a partial mixed-type inhibitor for hADP-GK, mainly by decreasing the MgADP affinity. Regarding its distribution, phylogenetic analysis shows that ADP-GK´s are present in a wide diversity of eukaryotic organisms although it is not ubiquitous. Eukaryotic ADP-GKs sequences cluster into two main groups, showing differences in the highly conserved sugar-binding motif reported for archaeal enzymes [NX(N)XD] where a cysteine residue is found instead of asparagine in a significant number of enzymes. Site directed mutagenesis of the cysteine residue by asparagine produces a 6-fold decrease in V_max, suggesting a role for this residue in the catalytic process, probably by facilitating the proper orientation of the substrate to be phosphorylated.

Unravelling the Role of Kinases That Underpin Androgen Signalling in Prostate Cancer

The androgen receptor (AR) signalling pathway is the key driver in most prostate cancers (PCa), and is underpinned by several kinases both upstream and downstream of the AR. Many popular therapies for PCa that target the AR directly, however, have been circumvented by AR mutation, such as androgen receptor variants. Some upstream kinases promote AR signalling, including those which phosphorylate the AR and others that are AR-regulated, and androgen regulated kinase that can also form feed-forward activation circuits to promotes AR function. All of these kinases represent potentially druggable targets for PCa. There has generally been a divide in reviews reporting on pathways upstream of the AR and those reporting on AR-regulated genes despite the overlap that constitutes the promotion of AR signalling and PCa progression. In this review, we aim to elucidate which kinases—both upstream and AR-regulated—may be therapeutic targets and require future investigation and ongoing trials in developing kinase inhibitors for PCa.

Variants of ADPGK gene and its effect on the male reproductive organ parameters and sperm count in Hu sheep

ADP-dependent glucokinase (ADPGK) plays an important role instead of hexokinase in regulating energy metabolism via the Embden-Meyerhof-Parnas Pathway. And energy provided via glycolysis promotes testis development and spermatogenesis. In this study, 466 Hu sheep were screened for mutations in the ADPGK gene to examine the association of the ADPGK gene polymorphisms with the testis traits and spermatogenesis. The NC_056060.1: g.31295 C > T SNP was found in the 3'-UTR region, resulting in two genotypes CC and TC type with genotypic frequencies of 0.66 and 0.34, respectively. This mutation was significantly associated with testis weight, testis long circumference, testis short girth, epididymis weight, and sperm concentration (p < 0.05). Moreover, TC genotype individuals had an increased tendency in the expression of the ADPGK gene and had significant reproductive performance advantages compared with CC genotype individuals in the study. And compared with the small testes (<50 g), the ADPGK gene expression of big testes (>160 g) increased significantly. This indicates an association between the ADPGK gene and reproductive organ parameters and sperm count in selected Hu sheep breed, and this SNP may serve as an effective DNA molecular marker for marker-assisted selection in Hu sheep breeding programs.

Adipose Triglyceride Lipase Loss Promotes a Metabolic Switch in A549 Non-Small Cell Lung Cancer Cell Spheroids

Cancer cells undergo complex metabolic adaptations to survive and thrive in challenging environments. This is particularly prominent for solid tumors, where cells in the core of the tumor are under severe hypoxia and nutrient deprivation. However, such conditions are often not recapitulated in the typical 2D in vitro cancer models, where oxygen as well as nutrient exposure is quite uniform. The aim of this study was to investigate the role of a key neutral lipid hydrolase, namely adipose triglyceride lipase (ATGL), in cancer cells that are exposed to more tumor-like conditions. To that end, we cultured lung cancer cells lacking ATGL as multicellular spheroids in 3D and subjected them to comprehensive proteomics analysis and metabolic phenotyping. Proteomics data are available via ProteomeXchange with identifier PXD021105. As a result, we report that loss of ATGL enhanced growth of spheroids and facilitated their adaptation to hypoxia, by increasing the influx of glucose and endorsing a pro-Warburg effect. This was followed by changes in lipid metabolism and an increase in protein production. Interestingly, the observed phenotype was also recapitulated in an even more "in vivo like" setup, when cancer spheroids were grown on chick chorioallantoic membrane, but not when cells were cultured as a 2D monolayer. In addition, we demonstrate that according to the publicly available cancer databases, an inverse relation between ATGL expression and higher glucose dependence can be observed. In conclusion, we provide indications that ATGL is involved in regulation of glucose metabolism of cancer cells when grown in 3D (mimicking solid tumors) and as such could be an important factor of the treatment outcome for some cancer types. Finally, we also ratify the need for alternative cell culture models, as the majority of phenotypes observed in 3D and spheroids grown on chick chorioallantoic membrane were not observed in 2D cell culture.

Hypothesis: A Novel Neuroprotective Role for Glucose-6-phosphatase (G6PC3) in Brain-To Maintain Energy-Dependent Functions Including Cognitive Processes

The isoform of glucose-6-phosphatase in liver, G6PC1, has a major role in whole-body glucose homeostasis, whereas G6PC3 is widely distributed among organs but has poorly-understood functions. A recent, elegant analysis of neutrophil dysfunction in G6PC3-deficient patients revealed G6PC3 is a neutrophil metabolite repair enzyme that hydrolyzes 1,5-anhydroglucitol-6-phosphate, a toxic metabolite derived from a glucose analog present in food. These patients exhibit a spectrum of phenotypic characteristics and some have learning disabilities, revealing a potential linkage between cognitive processes and G6PC3 activity. Previously-debated and discounted functions for brain G6PC3 include causing an ATP-consuming futile cycle that interferes with metabolic brain imaging assays and a nutritional role involving astrocyte-neuron glucose-lactate trafficking. Detailed analysis of the anhydroglucitol literature reveals that it competes with glucose for transport into brain, is present in human cerebrospinal fluid, and is phosphorylated by hexokinase. Anhydroglucitol-6-phosphate is present in rodent brain and other organs where its accumulation can inhibit hexokinase by competition with ATP. Calculated hexokinase inhibition indicates that energetics of brain and erythrocytes would be more adversely affected by anhydroglucitol-6-phosphate accumulation than heart. These findings strongly support the paradigm-shifting hypothesis that brain G6PC3 removes a toxic metabolite, thereby maintaining brain glucose metabolism- and ATP-dependent functions, including cognitive processes.

ADP-dependent glucokinase as a novel onco-target for haematological malignancies

Warburg effect or aerobic glycolysis provides selective growth advantage to aggressive cancers. However, targeting oncogenic regulators of Warburg effect has always been challenging owing to the wide spectrum of roles of these molecules in multitude of cells. In this study, we present ADP-dependent glucokinase (ADPGK) as a novel glucose sensor and a potential onco-target in specifically high-proliferating cells in Burkitt’s lymphoma (BL). Previously, we had shown ADPGK to play a major role in T-cell activation and induction of Warburg effect. We now report ADPGK knock-out Ramos BL cells display abated in vitro and in vivo tumour aggressiveness, via tumour-macrophage co-culture, migration and Zebrafish xenograft studies. We observed perturbed glycolysis and visibly reduced markers of Warburg effect in ADPGK knock-out cells, finally leading to apoptosis. We found repression of MYC proto-oncogene, and up to four-fold reduction in accumulated mutations in translocated MYC in knock-out cells, signifying a successful targeting of the malignancy. Further, the activation induced differentiation capability of knock-out cells was impaired, owing to the inability to cope up with increased energy demands. The effects amplified greatly upon stimulation-based proliferation, thus providing a novel Burkitt’s lymphoma targeting mechanism originating from metabolic catastrophe induced in the cells by removal of ADPGK.

ADP-dependent glucokinase regulates energy metabolism via ER-localized glucose sensing

Modulation of energy metabolism to a highly glycolytic phenotype, i.e. Warburg effect, is a common phenotype of cancer and activated immune cells allowing increased biomass-production for proliferation and cell division. Endoplasmic reticulum (ER)-localized ADP-dependent glucokinase (ADPGK) has been shown to play a critical role in T cell receptor activation-induced remodeling of energy metabolism, however the underlying mechanisms remain unclear. Therefore, we established and characterized in vitro and in vivo models for ADPGK-deficiency using Jurkat T cells and zebrafish. Upon activation, ADPGK knockout Jurkat T cells displayed increased cell death and ER stress. The increase in cell death resulted from a metabolic catastrophe and knockout cells displayed severely disturbed energy metabolism hindering induction of Warburg phenotype. ADPGK knockdown in zebrafish embryos led to short, dorsalized body axis induced by elevated apoptosis. ADPGK hypomorphic zebrafish further displayed dysfunctional glucose metabolism. In both model systems loss of ADPGK function led to defective N- and O-glycosylation. Overall, our data illustrate that ADPGK is part of a glucose sensing system in the ER modulating metabolism via regulation of N- and O-glycosylation.

Adventitial Cell Atlas of wt (Wild Type) and ApoE (Apolipoprotein E)-Deficient Mice Defined by Single-Cell RNA Sequencing

Objective- Vascular adventitia encompasses progenitors and is getting recognized as the major site of inflammation in early stage of atherosclerosis. However, the cellular atlas of the heterogeneous adventitial cells, the intercellular communication, the cellular response of adventitia to hyperlipidemia, and its contribution to atherosclerosis have been elusive. Approach and Results- Single-cell RNA sequencing was applied to wt (wild type) and ApoE (apolipoprotein E)-deficient aortic adventitia from 12-week-old C57BL/6J mice fed on normal laboratory diet with early stage of atherosclerosis. Unbiased clustering analysis revealed that the landscape of adventitial cells encompassed adventitial mesenchyme cells, immune cells (macrophages, T cells, and B cells), and some types of rare cells, for example, neuron, lymphatic endothelial cells, and innate lymphoid cells. Seurat clustering analysis singled out 6 nonimmune clusters with distinct transcriptomic profiles, in which there predominantly were stem/progenitor cell-like and proinflammatory population (Mesen II). In ApoE-deficient adventitia, resident macrophages were activated and related to increased myeloid cell infiltration in the adventitia. Cell communication analysis further elucidated enhanced interaction between a mesenchyme cluster and inflammatory macrophages in ApoE-deficient adventitia. In vitro transwell assay confirmed the proinflammatory role of SCA1+ (stem cell antigen 1 positive) Mesen II population with increased CCL2 (chemokine [C-C motif] ligand 2) secretion and thus increased capacity to attract immune cells in ApoE-deficient adventitia. Conclusions- Cell atlas defined by single-cell RNA sequencing depicted the heterogeneous cellular landscape of the adventitia and uncovered several types of cell populations. Furthermore, resident cell interaction with immune cells appears crucial at the early stage of atherosclerosis.

Redox Regulation of Hexokinases

SIGNIFICANCE

Hexokinases are key enzymes that are responsible for the first reaction of glycolysis, but they also moonlight other cellular processes, including mitochondrial redox signaling regulation. Modulation of hexokinase activity and spatiotemporal location by reactive oxygen and nitrogen species as well as other gasotransmitters serves as the basis for a unique, underexplored method of tight and flexible regulation of these fundamental enzymes. Recent Advances: Redox modifications of thiols serve as a molecular code that enables the precise and complex regulation of hexokinases. Redox regulation of hexokinases is also used by multiple parasites to cause widespread and severe diseases, including malaria, Chagas disease, and sleeping sickness. Redox-active molecules affect each other, and the moonlighting activity of hexokinases provides another feedback loop that affects the cellular redox status and is hijacked in malignantly transformed cells.

CRITICAL ISSUES

Several compounds affect the redox status of hexokinases in vivo. These include the dehydroascorbic acid (oxidized form of vitamin C), pyrrolidinium porrolidine-1-carbodithioate (contraceptive), peroxynitrite (product of ethanol metabolism), alloxan (a glucose analog), and isobenzothiazolinone ebselen. However, very limited information is available regarding which amino acid residues in hexokinases are affected by redox signaling. Except in cases of monogenic diabetes, direct evidence is absent for disease phenotypes that are associated with variations within motifs that are susceptible to redox signaling.

FUTURE DIRECTIONS

Further studies should address the propensity of hexokinases and their disease-associated variants to participate in redox regulation. Robust and straightforward proteomic methods are needed to understand the context and consequences of hexokinase-mediated redox regulation in health and disease.

De novo transcriptome sequencing and analysis revealed the molecular basis of rapid fat accumulation by black soldier fly (Hermetia illucens, L.) for development of insectival biodiesel

BACKGROUND

Black soldier fly (BSF, Hermetia illucens L.) can efficiently degrade organic wastes and transform into a high fat containing insect biomass that could be used as feedstock for biodiesel production. Meanwhile, the molecular regulatory basis of fat accumulation by BSF is still unclear; it is necessary to identify vital genes and regulators that are involved in fat accumulation.

RESULTS

This study analyzed the dynamic state of fat content and fatty-acid composition of BSF larvae in eight different stages. The late prepupa stage exhibited the highest crude fat, with lauric acid being the main component. Therefore, to provide insight into this unexplained phenomenon, the molecular regulation of rapid fat accumulation by BSF larvae was investigated. The twelve developmental stages of BSF were selected for transcriptome analysis, including the eight stages used for investigation of fat content and fatty-acid composition. By Illumina sequencing, 218,295,450,000 nt were generated. Through assembly by Trinity, 70,475 unigenes were obtained with an average length of 1064 nt and an N50 of 1749 nt. The differentially expressed unigenes were identified by DESeq, with 9159 of them being up-regulated and 10,101 of them were down-regulated. The several putative genes that are involved in the formation of pyruvate, acetyl-CoA biosynthesis, acetyl-CoA transcription, fatty-acid biosynthesis, and triacylglycerol biosynthesis were identified. The four vital metabolic genes that are associated with fat accumulation were validated by quantitative real-time PCR (qRT-PCR). The molecular mechanism of fat accumulation in BSF was clarified in this investigation through the construction of a detailed fat accumulation model from our results.

CONCLUSION

The study provides an unprecedented level of insight from transcriptome sequencing to reveal the crude fat accumulation mechanism in developing BSF. The finding holds considerable promise for insectival biodiesel production, and the fat content and fatty-acid composition can be altered by genetic engineering approaches in the future for the insect production industry.

Peroxisome Proliferator-Activated Receptor-δ Supports the Metabolic Requirements of Cell Growth in TCRβ-Selected Thymocytes and Peripheral CD4+ T Cells

During T cell development, progenitor thymocytes undergo a large proliferative burst immediately following successful TCRβ rearrangement, and defects in genes that regulate this proliferation have a profound effect on thymus cellularity and output. Although the signaling pathways that initiate cell cycling and nutrient uptake after TCRβ selection are understood, less is known about the transcriptional programs that regulate the metabolic machinery to promote biomass accumulation during this process. In this article, we report that mice with whole body deficiency in the nuclear receptor peroxisome proliferator-activated receptor-δ (PPARδ^mut) exhibit a reduction in spleen and thymus cellularity, with a decrease in thymocyte cell number starting at the double-negative 4 stage of thymocyte development. Although in vivo DNA synthesis was normal in PPARδ^mut thymocytes, studies in the OP9-delta-like 4 in vitro system of differentiation revealed that PPARδ^mut double-negative 3 cells underwent fewer cell divisions. Naive CD4⁺ T cells from PPARδ^mut mice also exhibited reduced proliferation upon TCR and CD28 stimulation in vitro. Growth defects in PPAR-δ-deficient thymocytes and peripheral CD4⁺ T cells correlated with decreases in extracellular acidification rate, mitochondrial reserve, and expression of a host of genes involved in glycolysis, oxidative phosphorylation, and lipogenesis. By contrast, mice with T cell-restricted deficiency of Ppard starting at the double-positive stage of thymocyte development, although exhibiting defective CD4⁺ T cell growth, possessed a normal T cell compartment, pointing to developmental defects as a cause of peripheral T cell lymphopenia in PPARδ^mut mice. These findings implicate PPAR-δ as a regulator of the metabolic program during thymocyte and T cell growth.

Structural basis for ADP-dependent glucokinase inhibition by 8-bromo-substituted adenosine nucleotide

In higher eukaryotes, several ATP-utilizing enzymes known as hexokinases activate glucose in the glycolysis pathway by phosphorylation to glucose 6-phosphate. In contrast to canonical hexokinases, which use ATP, ADP-dependent glucokinase (ADPGK) catalyzes noncanonical phosphorylation of glucose to glucose 6-phosphate using ADP as a phosphate donor. Initially discovered in Archaea, the human homolog of ADPGK was described only recently. ADPGK's involvement in modified bioenergetics of activated T cells has been postulated, and elevated ADPGK expression has been reported in various cancer tissues. However, the physiological role of ADPGK is still poorly understood, and effective ADPGK inhibitors still await discovery. Here, we show that 8-bromo-substituted adenosine nucleotide inhibits human ADPGK. By solving the crystal structure of archaeal ADPGK in complex with 8-bromoadenosine phosphate (8-Br-AMP) at 1.81 Å resolution, we identified the mechanism of inhibition. We observed that 8-Br-AMP is a competitive inhibitor of ADPGK and that the bromine substitution induces marked structural changes within the protein's active site by engaging crucial catalytic residues. The results obtained using the Jurkat model of activated human T cells suggest its moderate activity in a cellular setting. We propose that our structural insights provide a critical basis for rational development of novel ADPGK inhibitors.

Crystal structure of ADP-dependent glucokinase from Methanocaldococcus jannaschii in complex with 5-iodotubercidin reveals phosphoryl transfer mechanism

ADP-dependent glucokinase (ADPGK) is an alternative novel glucose phosphorylating enzyme in a modified glycolysis pathway of hyperthermophilic Archaea. In contrast to classical ATP-dependent hexokinases, ADPGK utilizes ADP as a phosphoryl group donor. Here, we present a crystal structure of archaeal ADPGK from Methanocaldococcus jannaschii in complex with an inhibitor, 5-iodotubercidin, d-glucose, inorganic phosphate, and a magnesium ion. Detailed analysis of the architecture of the active site allowed for confirmation of the previously proposed phosphorylation mechanism and the crucial role of the invariant arginine residue (Arg197). The crystal structure shows how the phosphate ion, while mimicking a β-phosphate group, is positioned in the proximity of the glucose moiety by arginine and the magnesium ion, thus providing novel insights into the mechanism of catalysis. In addition, we demonstrate that 5-iodotubercidin inhibits human ADPGK-dependent T cell activation-induced reactive oxygen species (ROS) release and downstream gene expression, and as such it may serve as a model compound for further screening for hADPGK-specific inhibitors.

ADP-dependent phosphofructokinases from the archaeal order Methanosarcinales display redundant glucokinase activity

The genome of Methanosarcinales organisms presents both ADP-dependent glucokinase and phosphofructokinase genes. However, Methanococcoides burtonii has a truncate glucokinase gene with a large deletion at the C-terminal, where the catalytic GXGD motif is located. Characterization of its phosphofructokinase annotated protein shows that is a bifunctional enzyme able to supply the absence of the glucokinase activity. Moreover, kinetic analyses of the phosphofructokinase annotated enzyme from, Methanohalobium evestigatum demonstrated that this enzyme is also bifunctional. The high conservation of the active site residues of all the enzymes from the order Methanosarcinales suggest that they should be bifunctional, as was previously reported for the ADP-dependent kinases from Methanococcales, highlighting the redundancy of the glucokinase activity in this archaeal group. The presence of active glycolytic enzymes would be important when glycogen storage of these organisms needs to be degraded to be used as energy source. Kinetic and structural information allows us to establish a substrate specificity signature that identifies specific GK or PFK, and bifunctional enzymes in this family.

Reconstructed ancestral enzymes reveal that negative selection drove the evolution of substrate specificity in ADP-dependent kinases

One central goal in molecular evolution is to pinpoint the mechanisms and evolutionary forces that cause an enzyme to change its substrate specificity; however, these processes remain largely unexplored. Using the glycolytic ADP-dependent kinases of archaea, including the orders Thermococcales, Methanosarcinales, and Methanococcales, as a model and employing an approach involving paleoenzymology, evolutionary statistics, and protein structural analysis, we could track changes in substrate specificity during ADP-dependent kinase evolution along with the structural determinants of these changes. To do so, we studied five key resurrected ancestral enzymes as well as their extant counterparts. We found that a major shift in function from a bifunctional ancestor that could phosphorylate either glucose or fructose 6-phosphate (fructose-6-P) as a substrate to a fructose 6-P-specific enzyme was started by a single amino acid substitution resulting in negative selection with a ground-state mode against glucose and a subsequent 1,600-fold change in specificity of the ancestral protein. This change rendered the residual phosphorylation of glucose a promiscuous and physiologically irrelevant activity, highlighting how promiscuity may be an evolutionary vestige of ancestral enzyme activities, which have been eliminated over time. We also could reconstruct the evolutionary history of substrate utilization by using an evolutionary model of discrete binary characters, indicating that substrate uses can be discretely lost or acquired during enzyme evolution. These findings exemplify how negative selection and subtle enzyme changes can lead to major evolutionary shifts in function, which can subsequently generate important adaptive advantages, for example, in improving glycolytic efficiency in Thermococcales.

Chemoproteomic Profiling of Bile Acid Interacting Proteins

Bile acids (BAs) are a family of endogenous metabolites synthesized from cholesterol in liver and modified by microbiota in gut. Being amphipathic molecules, the major function of BAs is to help with dietary lipid digestion. In addition, they also act as signaling molecules to regulate lipid and glucose metabolism as well as gut microbiota composition in the host. Remarkably, recent discoveries of the dedicated receptors for BAs such as FXR and TGR5 have uncovered a number of novel actions of BAs as signaling hormones which play significant roles in both physiological and pathological conditions. Disorders in BAs' metabolism are closely related to metabolic syndrome and intestinal and neurodegenerative diseases. Though BA-based therapies have been clinically implemented for decades, the regulatory mechanism of BA is still poorly understood and a comprehensive characterization of BA-interacting proteins in proteome remains elusive. We herein describe a chemoproteomic strategy that uses a number of structurally diverse, clickable, and photoreactive BA-based probes in combination with quantitative mass spectrometry to globally profile BA-interacting proteins in mammalian cells. Over 600 BA-interacting protein targets were identified, including known endogenous receptors and transporters of BA. Analysis of these novel BA-interacting proteins revealed that they are mainly enriched in functional pathways such as endoplasmic reticulum (ER) stress response and lipid metabolism, and are predicted with strong implications with Alzheimer's disease, non-alcoholic fatty liver disease, and diarrhea. Our findings will significantly improve the current understanding of BAs' regulatory roles in human physiology and diseases.

Benserazide, a dopadecarboxylase inhibitor, suppresses tumor growth by targeting hexokinase 2

BACKGROUND

Hexokinase (HK) is the rate-limiting enzyme in the first reaction of glycolysis. And Hexokinase 2 (HK2) is most closely related to malignant tumor which expresses at higher level compared with normal cells. HK2 plays a pivotal role in tumor initiation and maintenance, which provides a new target for cancer therapy.

METHODS

Structure-based virtual ligand screening was used in hit identification from ZINC Drug Database. Microscale thermophoresis assay was performed to evaluate the binding affinity. Enzyme inhibition, cytotoxicity, apoptosis, intracellular ATP level, mitochondrial membrane potential (MMP), glucose uptake and lactate production experiments were undertaken in SW480 cells to identify Benz as a HK2 inhibitor. Western blot was used to test protein expression. SW480 cells xenograft mouse models were used for in vivo study. Nano-particles of Benz were prepared to improve the antitumor efficacy and tumor targeting of Benz. HPLC was used to measure the concentration of free Benz in tumor tissues.

RESULTS

Benserazide (Benz), was identified as a selective HK2 inhibitor, could specifically bind to HK2 and significantly inhibit HK2 enzymatic activity in vitro. In addition, Benz reduced glucose uptake, lactate production and intracellular ATP level, and could cause cell apoptosis and an increased loss of MMP as well. In vivo study indicated that intraperitoneal (ip) injection of Benz at 300 and 600 mg/Kg suppressed cancer growth in tumor-bearing mice and no toxicity shown. To further improve the antitumor efficacy and tumor targeting of Benz, nano-particles of Benz was prepared. Liposomal Benz at 100 and 200 mg/Kg performed potent inhibitory effects on tumor-bearing mice, showing reduced dose and better efficacy.

CONCLUSIONS

Our study provides a new direction for the development of Benz and its analogues as novel antitumor agents for cancer therapy.

Genetic Dissection of a QTL Affecting Bone Geometry

Parameters of bone geometry such as width, length, and cross-sectional area are major determinants of bone strength. Although these traits are highly heritable, few genes influencing bone geometry have been identified. Here, we dissect a major quantitative trait locus (QTL) influencing femur size. This QTL was originally identified in an F2 cross between the C57BL/6J-hg/hg (HG) and CAST/EiJ strains and was referred to as femur length in high growth mice 2 (Feml2). Feml2 was located on chromosome (Chr.) 9 at ∼20 cM. Here, we show that the HG.CAST-(D9Mit249-D9Mit133)/Ucd congenic strain captures Feml2. In an F2 congenic cross, we fine-mapped the location of Feml2 to an ∼6 Mbp region extending from 57.3 to 63.3 Mbp on Chr. 9. We have identified candidates by mining the complete genome sequence of CAST/EiJ and through allele-specific expression (ASE) analysis of growth plates in C57BL/6J × CAST/EiJ F1 hybrids. Interestingly, we also find that the refined location of Feml2 overlaps a cluster of six independent genome-wide associations for human height. This work provides the foundation for the identification of novel genes affecting bone geometry.

Immunometabolism in Tuberculosis

Immunometabolism, the study of the relationship between bioenergetic pathways and specific functions of immune cells, has recently gained increasing appreciation. In response to infection, activation of the host innate and adaptive immune cells is accompanied by a switch in the bioenergetic pathway from oxidative phosphorylation to glycolysis, a metabolic remodeling known as the Warburg effect, which is required for the production of antimicrobial and pro-inflammatory effector molecules. In this review, we summarize the current understanding of the Warburg effect and discuss its association with the expression of host immune responses in tuberculosis (TB), an infectious disease caused by Mycobacterium tuberculosis (Mtb). We also discuss potential mechanisms underlying the Warburg effect with a focus on the expression and regulation of hypoxia-inducible factor 1 alpha (HIF-1α), the regulatory subunit of HIF-1, a major transcription regulator involved in cellular stress adaptation processes, including energy metabolism and antimicrobial responses. We also propose a novel hypothesis that Mtb perturbs the Warburg effect of immune cells to facilitate its survival and persistence in the host. A better understanding of the dynamics of metabolic states of immune cells and their specific functions during TB pathogenesis can lead to the development of immunotherapies capable of promoting Mtb clearance and reducing Mtb persistence and the emergence of drug resistant strains.

The Structural and Functional Characterization of Mammalian ADP-dependent Glucokinase

The enzyme-catalyzed phosphorylation of glucose to glucose-6-phosphate is a reaction central to the metabolism of all life. ADP-dependent glucokinase (ADPGK) catalyzes glucose-6-phosphate production, utilizing ADP as a phosphoryl donor in contrast to the more well characterized ATP-requiring hexokinases. ADPGK is found in Archaea and metazoa; in Archaea, ADPGK participates in a glycolytic role, but a function in most eukaryotic cell types remains unknown. We have determined structures of the eukaryotic ADPGK revealing a ribokinase-like tertiary fold similar to archaeal orthologues but with significant differences in some secondary structural elements. Both the unliganded and the AMP-bound ADPGK structures are in the "open" conformation. The structures reveal the presence of a disulfide bond between conserved cysteines that is positioned at the nucleotide-binding loop of eukaryotic ADPGK. The AMP-bound ADPGK structure defines the nucleotide-binding site with one of the disulfide bond cysteines coordinating the AMP with its main chain atoms, a nucleotide-binding motif that appears unique to eukaryotic ADPGKs. Key amino acids at the active site are structurally conserved between mammalian and archaeal ADPGK, and site-directed mutagenesis has confirmed residues essential for enzymatic activity. ADPGK is substrate inhibited by high glucose concentration and shows high specificity for glucose, with no activity for other sugars, as determined by NMR spectroscopy, including 2-deoxyglucose, the glucose analogue used for tumor detection by positron emission tomography.

Metabolism of activated T lymphocytes

Activated T cells undergo metabolic reprogramming which promotes glycolytic flux and lactate production as well as elevated production of lipids, proteins, nucleic acids and other carbohydrates (i.e. induction of biomass) even in the presence of oxygen. Activated T cells show induced expression of, among other things, Glucose Transporter 1 and several glycolytic enzymes, including ADP-Dependent Glucokinase and the low affinity isoform Pyruvate Kinase-M2 (which promote glycolytic flux), as well Glutamine Transporters and Glycerol-3-phosphate Dehydrogenase 2 which make available glutamate and glycerol-3-phosphate as mitochondrial energy sources. Intracellular leucine concentrations critically regulate mammalian target of rapamycin (mTOR) signaling to promote Th1, Th2, and Th17 CD4(+) T effector cell differentiation. In contrast, T regulatory (Treg) cells are generated when AMP-Activating Protein Kinase signaling is activated and mTOR activation is suppressed. Unlike effector CD4(+) and CD8(+) T cells, Tregs and memory T cells oxidize fatty acids for fuel. Effector and memory T cells perform different functions and thus show distinct metabolic profiles which are exquisitely controlled by cellular signaling. Upon activation, T cells express the insulin and leptin receptors on their surface and become sensitive to insulin signaling and nutrient availability and show changes in differentiation. Thus, metabolism and nutrient availability influence T cell activation and function.

Techniques to monitor glycolysis

An increased flux through glycolysis supports the proliferation of cancer cells by providing additional energy in the form of ATP as well as glucose-derived metabolic intermediates for nucleotide, lipid, and protein biosynthesis. Thus, glycolysis and other metabolic pathways that control cell proliferation may represent valuable targets for therapeutic interventions and diagnostic procedures. In this context, the measurement of glucose uptake and lactate excretion by malignant cells may be useful to detect shifts in glucose catabolism, while determining the activity of rate-limiting glycolytic enzymes can provide insights into points of metabolic regulation. Moreover, metabolomic studies can be used to generate large, integrated datasets to track changes in carbon flux through glycolysis and its collateral anabolic pathways. As discussed here, these approaches can reveal and quantify the metabolic alterations that underlie malignant cell proliferation.

Zinc finger nuclease mediated knockout of ADP-dependent glucokinase in cancer cell lines: effects on cell survival and mitochondrial oxidative metabolism

Zinc finger nucleases (ZFN) are powerful tools for editing genes in cells. Here we use ZFNs to interrogate the biological function of ADPGK, which encodes an ADP-dependent glucokinase (ADPGK), in human tumour cell lines. The hypothesis we tested is that ADPGK utilises ADP to phosphorylate glucose under conditions where ATP becomes limiting, such as hypoxia. We characterised two ZFN knockout clones in each of two lines (H460 and HCT116). All four clones had frameshift mutations in all alleles at the target site in exon 1 of ADPGK, and were ADPGK-null by immunoblotting. ADPGK knockout had little or no effect on cell proliferation, but compromised the ability of H460 cells to survive siRNA silencing of hexokinase-2 under oxic conditions, with clonogenic survival falling from 21±3% for the parental line to 6.4±0.8% (p = 0.002) and 4.3±0.8% (p = 0.001) for the two knockouts. A similar increased sensitivity to clonogenic cell killing was observed under anoxia. No such changes were found when ADPGK was knocked out in HCT116 cells, for which the parental line was less sensitive than H460 to anoxia and to hexokinase-2 silencing. While knockout of ADPGK in HCT116 cells caused few changes in global gene expression, knockout of ADPGK in H460 cells caused notable up-regulation of mRNAs encoding cell adhesion proteins. Surprisingly, we could discern no consistent effect on glycolysis as measured by glucose consumption or lactate formation under anoxia, or extracellular acidification rate (Seahorse XF analyser) under oxic conditions in a variety of media. However, oxygen consumption rates were generally lower in the ADPGK knockouts, in some cases markedly so. Collectively, the results demonstrate that ADPGK can contribute to tumour cell survival under conditions of high glycolytic dependence, but the phenotype resulting from knockout of ADPGK is cell line dependent and appears to be unrelated to priming of glycolysis in these lines.

Mitochondria as oxidative signaling organelles in T-cell activation: physiological role and pathological implications

Early scientific reports limited the cell biological role of reactive oxygen species (ROS) to the cause of pathological damage. However, extensive research performed over the last decade led to a wide recognition of intracellular oxidative/redox signaling as a crucial mechanism of homeostatic regulation. Amongst different cellular processes known to be influenced by redox signaling, T-cell activation is one of the most established. Numerous studies reported an indispensible role for ROS as modulators of T-cell receptor-induced transcription. Nevertheless, mechanistic details regarding signaling pathways triggered by ROS are far from being delineated. The nature and interplay between enzymatic sources involved in the generation of "oxidative signals" are also a matter of ongoing research. In particular, active participation of the mitochondrial respiratory chain as ROS producer constitutes an intriguing issue with various implications for bioenergetics of activated T cells as well as for T-cell-mediated pathologies. The aim of the current review is to address these interesting concepts.

T cell activation is driven by an ADP-dependent glucokinase linking enhanced glycolysis with mitochondrial reactive oxygen species generation

Mitochondria-originating reactive oxygen species (ROS) control T cell receptor (TCR)-induced gene expression. Here, we show that TCR-triggered activation of ADP-dependent glucokinase (ADPGK), an alternative, glycolytic enzyme typical for Archaea, mediates generation of the oxidative signal. We also show that ADPGK is localized in the endoplasmic reticulum and suggest that its active site protrudes toward the cytosol. The ADPGK-driven increase in glycolytic metabolism coincides with TCR-induced glucose uptake, downregulation of mitochondrial respiration, and deviation of glycolysis toward mitochondrial glycerol-3-phosphate dehydrogenase(GPD) shuttle; i.e., a metabolic shift to aerobic glycolysis similar to the Warburg effect. The activation of respiratory-chain-associated GPD2 results in hyperreduction of ubiquinone and ROS release from mitochondria. In parallel, mitochondrial bioenergetics and ultrastructure are altered. Downregulation of ADPGK or GPD2 abundance inhibits oxidative signal generation and induction of NF-κB-dependent gene expression, whereas overexpression of ADPGK potentiates them.