Proline oxidase controls proline, glutamate, and glutamine cellular concentrations in a U87 glioblastoma cell line

Proline Metabolism in WHO G4 Gliomas Is Altered as Compared to Unaffected Brain Tissue

Proline metabolism has been identified as a significant player in several neoplasms, but knowledge of its role in gliomas is limited despite it providing a promising line of pursuit. Data on proline metabolism in the brain are somewhat historical. This study aims to investigate alterations of proline metabolism in gliomas of WHO grade 4 (GG4) in the context of the brain. A total of 20 pairs of samples were studied, consisting of excised tumor and unaffected brain tissue, obtained when partial brain resection was required to reach deep-seated lesions. Levels of proline oxidase/proline dehydrogenase (POX/PRODH), Δ1-pyrroline-5-carboxylate reductases (PYCR1/2/3), prolidase (PEPD), and metalloproteinases (MMP-2, MMP-9) were assessed, along with the concentration of proline and proline-related metabolites. In comparison to normal brain tissue, POX/PRODH expression in GG4 was found to be suppressed, while PYCR1 expression and activity of PEPD, MMP-2, and -9 were upregulated. The GG4 proline concentration was 358% higher. Hence, rewiring of the proline metabolism in GG4 was confirmed for the first time, with a low-POX/PRODH/high-PYCR profile. High PEPD and MMPs activity is in keeping with GG4-increased collagen turnover and local aggressiveness. Further studies on the mechanisms of the interplay between altered proline metabolism and the GG4 microenvironment are warranted.

Metabolite profiling of peripheral blood plasma in pigs in early postnatal life fed whole bovine, caprine or ovine milk

Ruminants' milk is commonly used for supplying nutrients to infants when breast milk is unavailable or limited. Previous studies have highlighted the differences between ruminants' milk composition, digestion, absorption, and fermentation. However, whether consuming different ruminants' milk impact the appearance of the circulatory blood metabolites in the early postnatal life is not well understood. The analysis conducted here aimed to determine the effect of feeding exclusively whole milk from bovine, caprine or ovine species to pigs, approximately 7 days-old for 15 days, on circulatory blood plasma metabolites. Relative intensities of plasma metabolites were detected using a liquid chromatography-mass spectrometry based metabolomic approach. Seven polar and 83 non-polar (lipids) metabolites in plasma were significantly different (false discovery rate < 0.05) between milk treatments. These included polar metabolites involved in amino acid metabolism and lipids belonging to phosphatidylcholine, lysophosphatidylcholine, sphingomyelin, and triglycerides. Compared to the caprine or bovine milk group, the relative intensities of polar metabolites and unsaturated triglycerides were higher in the peripheral circulation of the ovine milk group. In contrast, relative intensities of saturated triglycerides and phosphatidylcholine were higher in the bovine milk group compared to the ovine or caprine milk group. In addition, correlations were identified between amino acid and lipid intake and their appearance in peripheral blood circulation. The results highlighted that consuming different ruminants' milk influences the plasma appearance of metabolites, especially lipids, that may contribute to early postnatal life development in pigs.

Prolidase-proline oxidase axis is engaged in apoptosis induction by birch buds flavonol santin in endometrial adenocarcinoma cell line

Cancer of the corpus uteri and cervix uteri, collectively ranks second among new cancer cases in women after breast cancer. Therefore, investigation of new anticancer agents and identifying new molecular targets presents a challenge to improve effectiveness of chemotherapy. In this study, antiproliferative activity of flavonoids derived from the buds of silver birch and downy birch was evaluated in endometrial cancer Ishikawa cells and cervical cancer HeLa cells. It was found that flavanol santin reduced viability of both cell lines better than other flavonoids, including apigenin and luteolin. Moreover, this activity was slightly higher than that induced by the chemotherapy drug, cisplatin. Santin promoted intrinsic and extrinsic apoptosis pathways in cancer cells, but it had low toxicity in normal fibroblasts. The mechanisms of impairing cancer cell viability included induction of oxidative proline catabolism, however in different ways in the cell lines used. In HeLa cells, increase of proline oxidation was due to activation of p53 leading to proline oxidase upregulation. In contrast, in Ishikawa cells, having basal proline oxidase level significantly higher than HeLa cells, santin treatment decreased its expression. Nevertheless, proline oxidation was induced in these cells since santin increased expression and activity of prolidase, an enzyme providing proline from protein degradation. In both cell lines, proline oxidation was associated with generation of reactive oxygen species leading to reduction in cell viability. Our findings reveal the involvement of proline oxidase in induction of apoptosis by santin and identify a role of prolidase in proline oxidase-dependent apoptosis.

Integrating Multi-Omics Analysis for Enhanced Diagnosis and Treatment of Glioblastoma: A Comprehensive Data-Driven Approach

The most aggressive primary malignant brain tumor in adults is glioblastoma (GBM), which has poor overall survival (OS). There is a high relapse rate among patients with GBM despite maximally safe surgery, radiation therapy, temozolomide (TMZ), and aggressive treatment. Hence, there is an urgent and unmet clinical need for new approaches to managing GBM. The current study identified modules (MYC, EGFR, PIK3CA, SUZ12, and SPRK2) involved in GBM disease through the NeDRex plugin. Furthermore, hub genes were identified in a comprehensive interaction network containing 7560 proteins related to GBM disease and 3860 proteins associated with signaling pathways involved in GBM. By integrating the results of the analyses mentioned above and again performing centrality analysis, eleven key genes involved in GBM disease were identified. ProteomicsDB and Gliovis databases were used for determining the gene expression in normal and tumor brain tissue. The NetworkAnalyst and the mGWAS-Explorer tools identified miRNAs, SNPs, and metabolites associated with these 11 genes. Moreover, a literature review of recent studies revealed other lists of metabolites related to GBM disease. The enrichment analysis of identified genes, miRNAs, and metabolites associated with GBM disease was performed using ExpressAnalyst, miEAA, and MetaboAnalyst tools. Further investigation of metabolite roles in GBM was performed using pathway, joint pathway, and network analyses. The results of this study allowed us to identify 11 genes (UBC, HDAC1, CTNNB1, TRIM28, CSNK2A1, RBBP4, TP53, APP, DAB1, PINK1, and RELN), five miRNAs (hsa-mir-221-3p, hsa-mir-30a-5p, hsa-mir-15a-5p, hsa-mir-130a-3p, and hsa-let-7b-5p), six metabolites (HDL, N6-acetyl-L-lysine, cholesterol, formate, N, N-dimethylglycine/xylose, and X2. piperidinone) and 15 distinct signaling pathways that play an indispensable role in GBM disease development. The identified top genes, miRNAs, and metabolite signatures can be targeted to establish early diagnostic methods and plan personalized GBM treatment strategies.

Glutamine, proline, and isoleucine support maturation and fertilisation of bovine oocytes

Successful in-vitro production of bovine embryos relies on meiotic maturation of oocytes in vitro (IVM) before they can be fertilised. High levels of IVM are currently achieved using a complex medium that contains all 20 common amino acids, namely TCM199, but can also be achieved using a simple inorganic salt solution containing non-essential amino acids, proline, and glutamine. Further simplification of the amino acid content of medium used for IVM could lead to a more defined medium that provides reproducible IVM. The aim of this study was, therefore, to determine the minimal amino acid requirements for bovine oocyte nuclear maturation, as measured by progression to metaphase II (MII) of meiosis. Supplementation of a simple medium composed of inorganic salts (M1 medium) with multiple amino-acid combinations showed that M1 containing glutamine, proline, and isoleucine resulted in nuclear maturation comparable to that of TCM199 (57.4 ± 3.4% vs 67% ± 1.7%, respectively) but was reduced when cystine (Cys2) to that seen with M1 alone (38.0 ± 2.2%). Viability of oocytes matured in this simplified medium was equal to those matured in TCM199 since the same proportion of zygotes with 2 pronuclei were observed following fertilisation in medium containing no amino acids (33.9 ± 6.5% vs 33.3 ± 3.6%, respectively). Addition of glutamine, proline and isoleucine to fertilisation medium also increased the proportion of zygotes but did not increase blastocyst development rates. Thus, a defined medium containing only glutamine, proline and isoleucine is sufficient for oocyte maturation and successful fertilisation.

Fetal Exposure to Maternal Smoking and Neonatal Metabolite Profiles

Fetal tobacco exposure has persistent effects on growth and metabolism. The underlying mechanisms of these relationships are yet unknown. We investigated the associations of fetal exposure to maternal smoking with neonatal metabolite profiles. In a population-based cohort study among 828 mother-infant pairs, we assessed maternal tobacco use by questionnaire. Metabolite concentrations of amino acids, non-esterified fatty acids, phospholipids and carnitines were determined by using LC-MS/MS in cord blood samples. Metabolite ratios reflecting metabolic pathways were computed. Compared to non-exposed neonates, those exposed to first trimester only tobacco smoking had lower neonatal mono-unsaturated acyl-alkyl-phosphatidylcholines (PC.ae) and alkyl-lysophosphatidylcholines (Lyso.PC.e) 18:0 concentrations. Neonates exposed to continued tobacco smoking during pregnancy had lower neonatal mono-unsaturated acyl-lysophosphatidylcholines (Lyso.PC.a), Lyso.PC.e.16:0 and Lyso.PC.e.18:1 concentration (False discovery rate (FDR) p-values < 0.05). Dose-response associations showed the strongest effect estimates in neonates whose mothers continued smoking ≥5 cigarettes per day (FDR p-values < 0.05). Furthermore, smoking during the first trimester only was associated with altered neonatal metabolite ratios involved in the Krebs cycle and oxidative stress, whereas continued smoking during pregnancy was associated with inflammatory, transsulfuration, and insulin resistance markers (p-value < 0.05). Thus, fetal tobacco exposure seems associated with neonatal metabolite profile adaptations. Whether these changes relate to later life metabolic health should be studied further.

Genome-scale metabolic modelling of the human gut microbiome reveals changes of the glyoxylate and dicarboxylate metabolism in metabolic disorders

The human gut microbiome has been associated with metabolic disorders including obesity, type 2 diabetes, and atherosclerosis. Understanding the contribution of microbiome metabolic changes is important for elucidating the role of gut bacteria in regulating metabolism. We used available metagenomics data from these metabolic disorders, together with genome-scale metabolic modeling of key bacteria in the individual and community-level to investigate the mechanistic role of the gut microbiome in metabolic diseases. Modeling predicted increased levels of glutamate consumption along with the production of ammonia, arginine, and proline in gut bacteria common across the disorders. Abundance profiles and network-dependent analysis identified the enrichment of tartrate dehydrogenase in the disorders. Moreover, independent plasma metabolite levels showed associations between metabolites including proline and tyrosine and an increased tartrate metabolism in healthy obese individuals. We, therefore, propose that an increased tartrate metabolism could be a significant mediator of the microbiome metabolic changes in metabolic disorders.

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Metagenomic analysis highlights key common bacterial species across metabolic diseases

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Metabolic models showed higher levels of acetate produced by disease enriched bacteria

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Reaction analysis revealed increases in the glyoxylate and dicarboxylate pathway

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Metabolomics and modeling analysis showed the potential role of tartrate metabolism

Proline Metabolism in Malignant Gliomas: A Systematic Literature Review

Simple Summary

Studies of various types of cancers have found proline metabolism to be a key player in tumor development, involved in basic metabolic pathways, regulating cell proliferation, survival, and signaling. Here, we systematically searched the literature to find data on proline metabolism in malignant glial tumors. Despite limited availability, existing studies have found several ways in which proline metabolism may affect the development of gliomas, involving the maintenance of redox balance, providing essential glutamate, and affecting major signaling pathways. Metabolomic profiling has revealed the importance of proline as a link to basic cell metabolic cycles and shown it to be correlated with overall survival. Emerging knowledge on the role of proline in general oncology encourages further studies on malignant gliomas.

Abstract

Background: Proline has attracted growing interest because of its diverse influence on tumor metabolism and the discovery of the regulatory mechanisms that appear to be involved. In contrast to general oncology, data on proline metabolism in central nervous system malignancies are limited. Materials and Methods: We performed a systematic literature review of the MEDLINE and EMBASE databases according to PRISMA guidelines, searching for articles concerning proline metabolism in malignant glial tumors. From 815 search results, we identified 14 studies pertaining to this topic. Results: The role of the proline cycle in maintaining redox balance in IDH-mutated gliomas has been convincingly demonstrated. Proline is involved in restoring levels of glutamate, the main glial excitatory neurotransmitter. Proline oxidase influences two major signaling pathways: p53 and NF- κB. In metabolomics studies, the metabolism of proline and its link to the urea cycle was found to be a prognostic factor for survival and a marker of malignancy. Data on the prolidase concentration in the serum of glioblastoma patients are contradictory. Conclusions: Despite a paucity of studies in the literature, the available data are interesting enough to encourage further research, especially in terms of extrapolating what we have learned of proline functions from other neoplasms to malignant gliomas.

NSAIDs Induce Proline Dehydrogenase/Proline Oxidase-Dependent and Independent Apoptosis in MCF7 Breast Cancer Cells

Non-steroidal anti-inflammatory drugs (NSAIDs) are considered in cancer therapy for their inhibitory effect on cyclooxygenase-2 (COX-2), which is overexpressed in most cancers. However, we found that NSAIDs as ligands of peroxisome proliferator-activated receptor-γ (PPARγ)-induced apoptosis independent of the COX-2 inhibition, and the process was mediated through activation of proline dehydrogenase/proline oxidase (PRODH/POX)-dependent generation of reactive oxygen species (ROS). This mitochondrial enzyme converts proline to ∆1-pyrroline-5-carboxylate (P5C) during which ATP or ROS is generated. To confirm the role of PRODH/POX in the mechanism of NSAID-induced apoptosis we obtained an MCF7 CRISPR/Cas9 PRODH/POX knockout breast cancer cell model (MCF7^POK-KO). Interestingly, the studied NSAIDs (indomethacin and diclofenac) in MCF7^POK-KO cells contributed to a more pronounced pro-apoptotic phenotype of the cells than in PRODH/POX-expressing MCF7 cells. The observed effect was independent of ROS generation, but it was related to the energetic disturbances in the cells as shown by an increase in the expression of AMPKα (sensor of cell energy status), GLUD1/2 (proline producing enzyme from glutamate), prolidase (proline releasing enzyme), PPARδ (growth supporting transcription factor) and a decrease in the expression of proline cycle enzymes (PYCR1, PYCRL), mammalian target of rapamycin (mTOR), and collagen biosynthesis (the main proline utilizing process). The data provide evidence that the studied NSAIDs induce PRODH/POX-dependent and independent apoptosis in MCF7 breast cancer cells.

Recreating the natural evolutionary trend in key microdomains provides an effective strategy for engineering of a thermomicrobial N-demethylase

N-demethylases have been reported to remove the methyl groups on primary or secondary amines, which could further affect the properties and functions of biomacromolecules or chemical compounds; however, the substrate scope and the robustness of N-demethylases have not been systematically investigated. Here we report the recreation of natural evolution in key microdomains of the Thermomicrobium roseum sarcosine oxidase (TrSOX), an N-demethylase with marked stability (melting temperature over 100 °C) and enantioselectivity, for enhanced substrate scope and catalytic efficiency on -C-N- bonds. We obtained the structure of TrSOX by crystallization and X-ray diffraction (XRD) for the initial framework. The natural evolution in the nonconserved residues of key microdomains—including the catalytic loop, coenzyme pocket, substrate pocket, and entrance site—was then identified using ancestral sequence reconstruction (ASR), and the substitutions that accrued during natural evolution were recreated by site-directed mutagenesis. The single and double substitution variants catalyzed the N-demethylation of N-methyl-L-amino acids up to 1800- and 6000-fold faster than the wild type, respectively. Additionally, these single substitution variants catalyzed the terminal N-demethylation of non-amino-acid compounds and the oxidation of the main chain -C-N- bond to a -C=N- bond in the nitrogen-containing heterocycle. Notably, these variants retained the enantioselectivity and stability of the initial framework. We conclude that the variants of TrSOX are of great potential use in N-methyl enantiomer resolution, main-chain Schiff base synthesis, and alkaloid modification or degradation.

Metabolomics in High Grade Gliomas

Gliomas are central nervous system (CNS) cancers that are challenging to treat due to their high proliferation and mutation rates. High grade gliomas include grade 3 and grade 4 tumors, which characteristically have a poor prognosis despite advancements in diagnostic methods and therapeutic options. Advances in metabolomics are resulting in more insight as to how cancer modifies the metabolism of the cell and surrounding tissue. Hence, this avenue of research may also emerge as a way to precisely target metabolites unique to gliomas. These biomarkers may provide opportunities for glioma diagnosis, prognosis and future therapeutic intervention. In this review, we harvest the literature that highlights notable biomolecules in high grade gliomas and promising therapeutic targets and interventions.

The Multifaceted Roles of Proline in Cell Behavior

Herein, we review the multifaceted roles of proline in cell biology. This peculiar cyclic imino acid is: (i) A main precursor of extracellular collagens (the most abundant human proteins), antimicrobial peptides (involved in innate immunity), salivary proteins (astringency, teeth health) and cornifins (skin permeability); (ii) an energy source for pathogenic bacteria, protozoan parasites, and metastatic cancer cells, which engage in extracellular-protein degradation to invade their host; (iii) an antistress molecule (an osmolyte and chemical chaperone) helpful against various potential harms (UV radiation, drought/salinity, heavy metals, reactive oxygen species); (iv) a neural metabotoxin associated with schizophrenia; (v) a modulator of cell signaling pathways such as the amino acid stress response and extracellular signal-related kinase pathway; (vi) an epigenetic modifier able to promote DNA and histone hypermethylation; (vii) an inducer of proliferation of stem and tumor cells; and (viii) a modulator of cell morphology and migration/invasiveness. We highlight how proline metabolism impacts beneficial tissue regeneration, but also contributes to the progression of devastating pathologies such as fibrosis and metastatic cancer.

Hyperprolinemia type I caused by homozygous p.T466M mutation in PRODH

Hyperprolinemia type I (HPI) is an autosomal recessive metabolic disorder caused by defects in proline oxidase. We herein describe a case of a patient with HPI and harboring the NM_016335.4 (PRODH_v001):c.1397 C > T (p.T466M) mutation and polymorphisms in the PRODH gene, as detected by plasma amino acid analysis and Sanger sequencing. The patient presented with short stature, carbohydrate-rich dietary preferences, and mild intellectual disability that was suggestive of a neurodevelopmental or learning disorder.

Proline dehydrogenase in cancer: apoptosis, autophagy, nutrient dependency and cancer therapy

L-proline catabolism is emerging as a key pathway that is critical to cellular metabolism, growth, survival, and death. Proline dehydrogenase (PRODH) enzyme, which catalyzes the first step of proline catabolism, has diverse functional roles in regulating many pathophysiological processes, including apoptosis, autophagy, cell senescence, and cancer metastasis. Notably, accumulated evidence demonstrated that PRODH plays complex role in many types of cancers. In this review, we briefly introduce the function of PRODH, then its expression in different types of cancer. We next discuss the regulation of PRODH in cancer, the downstream pathways of PRODH and the therapies that are under investigation. Finally, we propose novel insights for future perspectives on the modulation of PRODH.

Investigating the basis for the antidepressant effects of Gleditsiae spina using an integrated metabolomic strategy

OBJECTIVES

Gleditsiae spina (GS) is a natural antidepressant but its mechanisms of action remain unclear. In the present study, taxifolin (Tax) was selected to determine the role of flavonoids in the antidepressant effects of GS.

MATERIALS AND METHODS

Urine samples from C57BL/6 mice were analyzed based on ultra performance liquid chromatography-quadrupole time of flight mass spectrometry (UPLC-Q/TOF-MS). Then, we investigated the therapeutic effects of GS and Tax in depression models in vivo. An integrated metabolomic approach was used to examine the metabolic profiles of GS/Tax groups and corticosterone model groups (Cor). Metabolic networks in response to GS/Tax treatment were established for the comparison of antidepressant activities.

RESULTS

Corticosterone exposure significantly increased serum levels of corticosterone but decreased serum levels of 5-hydroxytryptamine and sucrose consumption (P<0.01). Treatment with GS and Tax improved all measured variables compared to those of the corticosterone-exposed group (P< 0.01). The antidepressant effects of GS and Tax involved the regulation of pentose and glucuronate interconversions, arginine and proline metabolism, phenylalanine metabolism, taurine and hypotaurine metabolism, and the citrate cycle.

CONCLUSION

These findings indicate that flavonoids form the pharmacodynamic basis of the antidepressant effects of GS. Moreover, our findings highlight that integrated metabolomics provides a powerful tool to study the mechanisms and material basis of Chinese herbs.

Promote the expression and corrected folding of an extremely stable N-demethylase by promoter reconstruction, native environment simulation and surface design

Thermomicrobium roseum sarcosine oxidase (TrSOX) was a N-demethylase with specific substrate chiral selectivity, outstanding thermostability and environmental resistance. To promote the expression of TrSOX in Bacillus subtilis W600, the HpaII promoter of pMA5 plasmid was replaced by constitutive or inducible promoters. Through orthogonal experiment, the expression process was optimized, B. subtilis W600 cells containing pMA5-Pxyl-trSOX plasmid were cultivated until OD_600nm reached 2.0 and were then induced with 1.6% xylose at 37 °C for 2 h, and the native environment of T. roseum was simulated by heating at 80 °C, with the productivity of TrSOX increased from ~8.3 to ~66.7 μg/g wet cells; and the simulated high temperature was the key switch for the final folding. To reduce the surface hydrophobicity, a S320R mutant was built to form a hydrophilic lid around the entrance of the substrate pocket, and the yield of TrSOX (S320R) was ~163.0 μg/g wet cells, approximately 20 folds as that in the initial expression system. This mutant revealed the similar secondary structure, stability, resistance, chiral substrate selectivity and optimal reaction environment with wild type TrSOX; however, the N-demethylation activities for amino acid derivative substrates were dramatically increased, while those for hydrophobic non-amino acid compounds were repressed.

Anti-depressant effect of Zhi-zi-chi decoction on CUMS mice and elucidation of its signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Zhi-zi-chi decoction (ZZCD) is used for treating depression as an effectively traditional Chinese medicine. Until now, studies on pharmacological research of ZZCD have mostly been centered in pharmacokinetic level. Little was known about its pharmacological mechanism of relieving depression.

AIM OF THE STUDY

This study was to evaluate the effect of ZZCD on relieving depression via behavioral tests, serum metabolomics and signaling target expression analysis on chronic unpredictable mild stress (CUMS) model mice.

MATERIALS AND METHODS

The CUMS exposure lasted 7 consecutive weeks. The mice were administrated with ZZCD for the last 3 weeks. Behavioral tests were applied and a serum metabolomics method based on UFLC/Q-TOF-MS with multivariate statistical and global metabolic network analysis was performed to identify relevant metabolites and pathways. Finally, the protein expressions in mouse hippocampi were determined by western blot to verify the metabolomics deduction.

RESULTS

Behavioral parameters were visibly changed after modeling, while high and medium dosage groups showed status improvement compared to the model group. Seventy six metabolites were identified as potential biomarkers from the metabolomics profiles in C₁₈ and HILIC systems. In addition, 9 significant pathways related to changed biomarkers were conducted. The pathways were closely connected by some key targets, which were significantly reduced in the model group compared with those in control group, while ZZCD treated groups showed corrections after 3-week administration. The results revealed that the anti-depression efficacy of ZZCD might be associated with PKA-CREB-BDNF-TrkB-PSD-95 pathway influenced by metabolic changes, verifying the pathway annotation speculation.

CONCLUSION

This study demonstrated that ZZCD had a positive treatment effect on CUMS depression model mice. Metabolomics results revealed the holistic and interconnected metabolic changes of ZZCD in CUMS mice. The metabolic pathway annotation suggested that the anti-depression mechanism of ZZCD might be related to signaling pathway in brain. PKA-CREB-BDNF-TrkB-PSD-95 signaling expression was a verification and complement to the metabolomics results.

In crystallo screening for proline analog inhibitors of the proline cycle enzyme PYCR1

Pyrroline-5-carboxylate reductase 1 (PYCR1) catalyzes the biosynthetic half-reaction of the proline cycle by reducing Δ1-pyrroline-5-carboxylate (P5C) to proline through the oxidation of NAD(P)H. Many cancers alter their proline metabolism by up-regulating the proline cycle and proline biosynthesis, and knockdowns of PYCR1 lead to decreased cell proliferation. Thus, evidence is growing for PYCR1 as a potential cancer therapy target. Inhibitors of cancer targets are useful as chemical probes for studying cancer mechanisms and starting compounds for drug discovery; however, there is a notable lack of validated inhibitors for PYCR1. To fill this gap, we performed a small-scale focused screen of proline analogs using X-ray crystallography. Five inhibitors of human PYCR1 were discovered: l-tetrahydro-2-furoic acid, cyclopentanecarboxylate, l-thiazolidine-4-carboxylate, l-thiazolidine-2-carboxylate, and N-formyl l-proline (NFLP). The most potent inhibitor was NFLP, which had a competitive (with P5C) inhibition constant of 100 μm The structure of PYCR1 complexed with NFLP shows that inhibitor binding is accompanied by conformational changes in the active site, including the translation of an α-helix by 1 Å. These changes are unique to NFLP and enable additional hydrogen bonds with the enzyme. NFLP was also shown to phenocopy the PYCR1 knockdown in MCF10A H-RASV12 breast cancer cells by inhibiting de novo proline biosynthesis and impairing spheroidal growth. In summary, we generated the first validated chemical probe of PYCR1 and demonstrated proof-of-concept for screening proline analogs to discover inhibitors of the proline cycle.

Plasma amino acids profile in first-episode psychosis, unaffected siblings and community-based controls

Investigations of plasma amino acids in early psychosis and their unaffected siblings are rare. We measured plasma amino acids involved in the co-activation of dopaminergic, GABAergic, glutamatergic, and serotoninergic neurotransmitters in first-episode psychosis (FEP) patients (n = 166), unaffected siblings (n = 76), and community-based controls (n = 166) included in a cross-sectional study. Plasma levels of glutamic acid (GLU), glutamine, glycine, proline (PRO), tryptophan (TRP), tyrosine, serine and GABA were quantified by gas-chromatography-mass spectrometry. We used the generalized linear model adjusted by sex, age, and body mass index for group comparison and paired t-test for FEP-Sibling pairs. FEP had reduced GABA plasma levels compared to siblings and controls (p < 0.05 for both). Siblings had lower GLU, Glx and PRO (p < 0.05 for all) but increased TRP compared to patients and controls (p < 0.05 for both). FEP patients with longer duration of pharmacological treatment and medicated only with antipsychotics had increased GLU compared to FEP with shorter periods, or with those treated with a combination of medications (p < 0.05 for both). Finally, FEP patients treated only with antipsychotics presented higher Glx compared to those with mixed medications (p = 0.026). Our study suggests that FEP have low a GABA plasma profile. Unaffected siblings may be a possible risk group for metabolic abnormalities.

Inference of Subpathway Activity Profiles Reveals Metabolism Abnormal Subpathway Regions in Glioblastoma Multiforme

Glioblastoma, also known as glioblastoma multiforme (GBM), is the most malignant form of glioma and represents 81% of malignant brain and central nervous system (CNS) tumors. Like most cancers, GBM causes metabolic recombination to promote cell survival, proliferation, and invasion of cancer cells. In this study, we propose a method for constructing the metabolic subpathway activity score matrix to accurately identify abnormal targets of GBM metabolism. By integrating gene expression data from different sequencing methods, our method identified 25 metabolic subpathways that were significantly abnormal in the GBM patient population, and most of these subpathways have been reported to have an effect on GBM. Through the analysis of 25 GBM-related metabolic subpathways, we found that (S)-2,3-Epoxysqualene, which was at the central region of the sterol biosynthesis subpathway, may have a greater impact on the entire pathway, suggesting a potential high association with GBM. Analysis of CCK8 cell activity indicated that (S)-2,3-Epoxysqualene can indeed inhibit the activity of U87-MG cells. By flow cytometry, we demonstrated that (S)-2,3-Epoxysqualene not only arrested the U87-MG cell cycle in the G0/G1 phase but also induced cell apoptosis. These results confirm the reliability of our proposed metabolic subpathway identification method and suggest that (S)-2,3-Epoxysqualene has potential therapeutic value for GBM. In order to make the method more broadly applicable, we have developed an R system package crmSubpathway to perform disease-related metabolic subpathway identification and it is freely available on the GitHub (https://github.com/hanjunwei-lab/crmSubpathway).

A novel plausible mechanism of NSAIDs-induced apoptosis in cancer cells: the implication of proline oxidase and peroxisome proliferator-activated receptor

Although pharmaco-epidemiological studies provided evidence for the anticancer potential of non-steroidal anti-inflammatory drugs (NSAIDs), the mechanism of their anti-cancer activity is not known. Several lines of evidence suggest that proline dehydrogenase/proline oxidase (PRODH/POX) may represent a target for NSAIDs-dependent anti-cancer activity. PRODH/POX catalyzes conversion of proline into Δ1-pyrroline-5-carboxylate releasing ATP or reactive oxygen species for autophagy/apoptosis. Since NSAIDs are ligands of peroxisome proliferator-activated receptor (PPARs) and PPARs are implicated in PRODH/POX-dependent apoptosis we provided a hypothesis on the mechanism of NSAIDs-induced apoptosis in cancer cells.

MicroRNA-15a, microRNA-15b and microRNA-16 inhibit the human dopamine D1 receptor expression in four cell lines by targeting 3'UTR -12 bp to + 154 bp

Background: The abnormal expression Dopamine D1 receptor (DRD1) gives rise to the dysfunction of dopaminergic neurotransmitter and may be associated with the occurrence of schizophrenia. MicroRNAs (miRNAs) can regulate the DRD1 expression by binding 3'UTR and be involved in the post-transcriptional regulation.Methods: We first constructed the pmirGLO-recombined vectors of series of DRD1 gene 3'UTR-truncated fragments and performed the luciferase receptor assay to screen the underlying 3'UTR sequence targeted by miRNAs. Then, we predicted the potential miRNAs binding the target sequence and confirmed their effects using luciferase receptor assay after transfection of the miRNA mimics/inhibitors. We also examined the effects of the miRNA on the endogenous DRD1 expression.Results: We found that the DRD1 3'UTR ranging from -12 to +1135 bp was essential for the post-transcriptional regulation of miRNAs. The deletion of -12 to +154 bp fragment significantly increased the luciferase expression but not the mRNA expression. The miRNA-15a, miRNA-15b and miRNA 16 affected DRD1 expression in HEK293, U87, SK-N-SH and SH-SY5Y cell lines.Conclusion: The miRNA-15a, miRNA-15b and miRNA-16 inhibit the human dopamine D1 receptor expression by targeting 3'UTR -12 to +154 bp.HighlightsDRD1 3'UTR ranging from -12 to +1135 bp was essential for the post-transcriptional regulation of miRNAs.The deletion of -12 to +154 bp fragment significantly increased the luciferase expression but not the mRNA expression.The miRNA-15a, miRNA-15b and miRNA 16 affected DRD1 expression in different cell lines, respectively.

Is the primate-specific protein pLG72 affecting SOD1 functionality and superoxide formation?

pLG72 is a primate-specific protein of enigmatic function that was proposed to modulate mitochondria fragmentation and the activity of the peroxisomal enzyme D-amino acid oxidase (DAAO). DAAO is deputed to degradation of the NMDA receptor co-agonist D-serine in human brain and the R199W substitution in DAAO was identified in a familial case of amyotrophic lateral sclerosis (ALS). A recent work reported that U87 glioblastoma cells ectopically expressing pLG72 showed a lower proliferation, produced superoxide radicals, induced SOD1 aggregation and decreased its activity. Because of the role of SOD1 in eliminating ROS species and its relevance in ALS we evaluated the link between pLG72 and SOD1 using both wild-type pLG72 and its R30K variant related to schizophrenia susceptibility. In vitro studies on recombinant proteins excluded the establishment of a stable complex and that pLG72 could affect SOD1 activity and stability. At cellular level, ectopic expression of pLG72 in glioblastoma U87 cells did not affect cell viability and ROS/superoxide production: only caspase activity (a marker of apoptosis) was slightly increased in cells expressing the R30K pLG72 variant. SOD1 and pLG72 did not colocalize in transfected U87 glioblastoma cells: pLG72 largely localised to mitochondria and SOD1 was largely cytosolic. Moreover, the ectopic expression of pLG72 appeared not to alter the expression of SOD1 and its aggregation. Altogether, the combination of biochemical and cellular studies allow to exclude that pLG72 modulates SOD1 function and aggregation, thus that it could play a role in ALS susceptibility.

Targeting Glutamine Addiction in Gliomas

The most common malignant brain tumors are those of astrocytic origin, gliomas, with the most aggressive glioblastoma (WHO grade IV) among them. Despite efforts, medicine has not made progress in terms of the prognosis and life expectancy of glioma patients. Behind the malignant phenotype of gliomas lies multiple genetic mutations leading to reprogramming of their metabolism, which gives those highly proliferating cells an advantage over healthy ones. The so-called glutamine addiction is a metabolic adaptation that supplements oxidative glycolysis in order to secure neoplastic cells with nutrients and energy in unfavorable conditions of hypoxia. The present review aims at presenting the research and clinical attempts targeting the different metabolic pathways involved in glutamine metabolism in gliomas. A brief description of the biochemistry of glutamine transport, synthesis, and glutaminolysis, etc. will forego a detailed comparison of the therapeutic strategies undertaken to inhibit glutamine utilization by gliomas.

Understanding the role of key amino acids in regulation of proline dehydrogenase/proline oxidase (prodh/pox)-dependent apoptosis/autophagy as an approach to targeted cancer therapy

In stress conditions, as neoplastic transformation, amino acids serve not only as nutrients to maintain the cell survival but also as mediators of several regulatory pathways which are involved in apoptosis and autophagy. Especially, under glucose deprivation, in order to maintain the cell survival, proline and glutamine together with other glutamine-derived products such as glutamate, alpha-ketoglutarate, and ornithine serve as alternative sources of energy. They are substrates for production of pyrroline-5-carboxylate which is the product of conversion of proline by proline dehydrogenase/ proline oxidase (PRODH/POX) to produce ATP for protective autophagy or reactive oxygen species for apoptosis. Interconversion of proline, ornithine, and glutamate may therefore regulate PRODH/POX-dependent apoptosis/autophagy. The key amino acid is proline, circulating between mitochondria and cytoplasm in the proline cycle. This shuttle is known as proline cycle. It is coupled to pentose phosphate pathway producing nucleotides for DNA biosynthesis. PRODH/POX is also linked to p53 and AMP-activated protein kinase (AMPK)-dependent pathways. Proline availability for PRODH/POX-dependent apoptosis/autophagy is regulated at the level of collagen biosynthesis (proline utilizing process) and prolidase activity (proline supporting process). In this review, we suggest that amino acid metabolism linking TCA and Urea cycles affect PRODH/POX-dependent apoptosis/autophagy and the knowledge might be useful to targeted cancer therapy.

Results supporting the concept of the oxidant-mediated protein amino acid conversion, a naturally occurring protein engineering process, in human cells

Reactive oxygen species (ROS) play an important role in the development of various pathological conditions as well as aging. ROS oxidize DNA, proteins, lipids, and small molecules. Carbonylation is one mode of protein oxidation that occurs in response to the iron-catalyzed, hydrogen peroxide-dependent oxidation of amino acid side chains. Although carbonylated proteins are generally believed to be eliminated through degradation, we previously discovered the protein de-carbonylation mechanism, in which the formed carbonyl groups are chemically eliminated without proteins being degraded. Major amino acid residues that are susceptible to carbonylation include proline and arginine, both of which are oxidized to become glutamyl semialdehyde, which contains a carbonyl group. The further oxidation of glutamyl semialdehyde produces glutamic acid. Thus, we hypothesize that through the ROS-mediated formation of glutamyl semialdehyde, the proline, arginine, and glutamic acid residues within the protein structure can be converted to each other. Mass spectrometry provided results supporting that proline 45 (a well-conserved residue within the catalytic sequence) of the peroxiredoxin 6 molecule may be converted into glutamic acid in cultured human cells, opening up a revolutionizing concept that biological oxidation elicits the naturally occurring protein engineering process.