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Proline metabolic links in human body. Proline metabolism is closely related with TCA cycle, urea cycle, and pentose phosphate pathway (pentose shunt). Abbreviations: GSA, glutamic-gamma-semialdehyde; OAT, ornithine aminotransferase; P5C, Δ1-pyrroline-5-carboxylate; P5CDH, P5C dehydrogenase; P5CS, P5C Synthase; PRODH (POX), proline dehydrogenase (oxidase); PYCR, P5C reductase. The interconversion between P5C and GSA is spontaneous.
Source publication
Proline dehydrogenase (oxidase, PRODH/POX), the first enzyme in the proline degradative pathway, plays a special role in tumorigenesis and tumor development. Proline metabolism catalyzed by PRODH/POX is closely linked with the tricarboxylic acid (TCA) cycle and urea cycle. The proline cycle formed by the interconversion of proline and Δ(1) -pyrroli...
Citations
... Unraveling its intricate network of interactions within cellular metabolism holds promise for therapeutic interventions targeting a wide array of pathological conditions. Proline dehydrogenase (PRODH), the first enzyme in proline catabolism, has been reported to be the most crucial enzyme in regulating proline metabolism (17). PRODH catalyzes the conversion of proline to pyrroline-5-carboxylate, further converting to glutamate or ornithine (18). ...
... In line with this, PRODH activity was reduced in the hearts upon TAC (Fig. 1H). Previous studies has indicated that TAC surgery activates the mammalian target of rapamycin (mTOR) pathway (20,21), which is known to negatively regulate PRODH expression (15,17). To elucidate the mechanisms underlying the decreased expression of PRODH following TAC surgery, we collected cardiac tissue samples from mice treated with 4 weeks of rapamycin or saline after TAC surgery. ...
... However, we observed partial restoration of PRODH expression in mouse cardiac tissues treated with rapamycin after TAC surgery. Previous studies have identified mTOR as a inhibitory regulator of PRODH (15,17), and its activation during TACinduced myocardial remodeling to promote compensatory cardiomyocyte hypertrophy is well established (20,21). mTOR senses the cellular nutrient and energy status and enhances processes such as glycolysis, protein, lipid, and nucleotide biosynthesis, thereby systematically altering cardiomyocyte synthesis and degradation metabolism (27). ...
Metabolic reprogramming is critical in the onset of pressure overload–induced cardiac remodeling. Our study reveals that proline dehydrogenase (PRODH), the key enzyme in proline metabolism, reprograms cardiomyocyte metabolism to protect against cardiac remodeling. We induced cardiac remodeling using transverse aortic constriction (TAC) in both cardiac-specific PRODH knockout and overexpression mice. Our results indicate that PRODH expression is suppressed after TAC. Cardiac-specific PRODH knockout mice exhibited worsened cardiac dysfunction, while mice with PRODH overexpression demonstrated a protective effect. In addition, we simulated cardiomyocyte hypertrophy in vitro using neonatal rat ventricular myocytes treated with phenylephrine. Through RNA sequencing, metabolomics, and metabolic flux analysis, we elucidated that PRODH overexpression in cardiomyocytes redirects proline catabolism to replenish tricarboxylic acid cycle intermediates, enhance energy production, and restore glutathione redox balance. Our findings suggest PRODH as a modulator of cardiac bioenergetics and redox homeostasis during cardiac remodeling induced by pressure overload. This highlights the potential of PRODH as a therapeutic target for cardiac remodeling.
... We noticed the activation of the proline cycle (↑ PEPD, POX/PRODH and PYCR1) to indicate constant remodeling (synthesis and degradation) of matrix collagen, which in turn can contribute to tumor heterogeneity. High POX/PRODH activity can be considered as a tumor survival factor through ATP production or ROS-induced autophagy [36]. Patients age and tumor morphology were the most confounding factors. ...
Ovarian cancer (OC) has emerged as the leading cause of death due to gynecological malignancies among women. Oxidative stress and metalloproteinases (MMPs) have been shown to influence signaling pathways and afflict the progression of carcinogenesis. Therefore, the assessment of matrix-remodeling and oxidative stress intensity can determine the degree of cellular injury and often the severity of redox-mediated chemoresistance. The study group comprised 27 patients with serous OC of which 18% were classified as Federation of Gynecology and Obstetrics (FIGO) stages I/II, while the rest were diagnosed grades III/IV. The control group comprised of 15 ovarian tissue samples. The results were compared with genetic data from The Cancer Genome Atlas. Nitro-oxidative stress, inflammation and apoptosis biomarkers were measured colorimetrically/fluorometrically or via real-time PCR in the primary ovarian tumor and healthy tissue. Stratification of patients according to FIGO stages revealed that high-grade carcinoma exhibited substantial alterations in redox balance, including the accumulation of protein glycoxidation and lipid peroxidation products. TCGA data demonstrated only limited prognostic usefulness of the studied genes. In conclusion, high-grade serous OC is associated with enhanced tissue oxidative/nitrosative stress and macromolecule damage that could not be overridden by the simultaneously augmented measures of antioxidant defense. Therefore, it can be assumed that tumor cells acquire adaptive mechanisms that enable them to withstand the potential toxic effects of elevated reactive oxygen species.
... On the other hand, interesting results from Panosyan et al. have linked tumor aggressiveness with increased POX/PRODH activity; i.e., samples with high POX/PRODH transcription were associated with significantly shorter overall survival [29]. Indeed, studies on non-glial neoplasms have come to the conclusion that POX/PRODH might play an ambiguous, context-dependent role depending on factors that are yet to be established [16,32]. The best example for a dual POX/PRODH role is the influence exerted through ROS, a byproduct of POX/PRODH activity, that may be either pro-apoptotic or pro-survival, where the steering mechanism towards each path has not yet been finally established [17]. ...
Simple Summary
Proline metabolism has been found to play an important role in neoplasms, but little is known about proline in gliomas or in the normal brain. This work investigates how the metabolism of proline in the brain and in gliomas of WHO grade 4 (GG4) may differ. A total of 20 pairs of samples were studied, consisting of both tumor and unaffected brain tissue, partially removed to make a surgical corridor. The levels of proline oxidase/proline dehydrogenase (POX/PRODH), Δ¹-pyrroline-5-carboxylate reductases (PYCR1/2/3), prolidase (PEPD), and metalloproteinase-2 and -9 (MMP-2 and MMP-9) were measured. Proline concentration was evaluated. GG4 levels of POX/PRODH were found to be lower, while PYCR1, PEPD, and MMPs were significantly higher than in brain tissue. In GG4, proline concentration was 358% higher. The results confirm changes in proline metabolism in GG4, with a low-POX/PRODH/high-PYCR pattern like that in other neoplasms. High levels of PEPD and MMPs are in keeping with GG4 aggressiveness.
Abstract
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.
... The reduction of both mitochondrial activity and ROS by Pro has been seen in other cells, including vitrified oocytes [77], but is not fully understood [78]. In fact, the result is counter-intuitive: (a) Pro can be converted to P5C (by POX) and then to α-ketoglutarate (via glutamate), and, hence, enter the TCA cycle [59,79], which ultimately boosts ETC activity. (b) POX is coupled to succinate dehydrogenase of Complex II in the ETC [13], and the high-energy electrons generated by its catalysis of Pro can be donated to the ETC to promote ATP production [80]. ...
The culture of embryos in the non-essential amino acid L-proline (Pro) or its analogues pipecolic acid (PA) and L-4-thiazolidine carboxylic acid (L4T) improves embryo development, increasing the percentage that develop to the blastocyst stage and hatch. Staining of 2-cell and 4-cell embryos with tetramethylrhodamine methyl ester and 2′,7′-dichlorofluorescein diacetate showed that the culture of embryos in the presence of Pro, or either of these analogues, reduced mitochondrial activity and reactive oxygen species (ROS), respectively, indicating potential mechanisms by which embryo development is improved. Inhibition of the Pro metabolism enzyme, proline oxidase, by tetrahydro-2-furoic-acid prevented these reductions and concomitantly prevented the improved development. The ways in which Pro, PA and L4T reduce mitochondrial activity and ROS appear to differ, despite their structural similarity. Specifically, the results are consistent with Pro reducing ROS by reducing mitochondrial activity while PA and L4T may be acting as ROS scavengers. All three may work to reduce ROS by contributing to the GSH pool. Overall, our results indicate that reduction in mitochondrial activity and oxidative stress are potential mechanisms by which Pro and its analogues act to improve pre-implantation embryo development.
... Metabolism of the amino acid proline affects many cellular processes beyond protein synthesis, including stress responses, osmotic adjustment, protein chaperoning, reactive oxygen species (ROS) signalling, redox homeostasis, and energy metabolism (Szabados and Savouré, 2010;Liu and Phang, 2012;Silao et al., 2019;Alvarez et al., 2021;Zheng et al., 2021). For example, proline metabolism participates in both biotic (Cecchini et al., 2011) and abiotic (Hayat et al., 2012) stress responses in plants and is critical in cancer reprogramming in humans (Phang, 2019). ...
Proline dehydrogenase (ProDH) and pyrroline-5-carboxylate (P5C) dehydrogenase (P5CDH) catalyze the oxidation of proline into glutamate via the intermediates P5C and glutamate-semialdehyde (GSA), which spontaneously interconvert. P5C and GSA are also intermediates in the production of glutamate from ornithine and α-ketoglutarate catalyzed by ornithine δ-aminotransferase (OAT). ProDH and P5CDH form a fused bifunctional PutA enzyme in Gram-negative bacteria and are associated in a bifunctional substrate channelling complex in Thermus thermophilus, but the physical proximity of ProDH and P5CDH in eukaryotes has not been described. Here we report evidence of physical proximity and interactions between Arabidopsis ProDH, P5CDH and OAT in the mitochondria of plants during dark-induced leaf senescence when all three enzymes are expressed. Pairwise interactions and localization of the three enzymes were investigated using bimolecular fluorescence complementation (BiFC) with confocal microscopy in tobacco and sub-mitochondrial fractionation in Arabidopsis. Evidence for a complex composed of ProDH, P5CDH, and OAT was revealed by co-migration of the proteins in native conditions upon gel electrophoresis. Co-immunoprecipitation coupled with mass spectrometry analysis confirmed the presence of the P5C metabolism complex in Arabidopsis. Pull-down assays further demonstrated a direct interaction between ProDH1 and P5CDH. P5C metabolism complexes may channel P5C among the constituent enzymes and directly provide electrons to the respiratory electron chain via ProDH.
... In the network of nitrogen remobilization during senescence, proline is one of the amino acids whose oxidation is induced. Proline accumulation contributes to osmotic adjustment, protein chaperoning, reactive oxygen species (ROS) signalling, redox homoeostasis and, after oxidation, energy production (reviewed in Szabados & Savouré, 2010;and W. Liu & Phang, 2012;Silao et al., 2019). In flowering plants, proline metabolism participates physiologically in plant adaptation to abiotic and biotic stresses and developmentally, for instance, in the formation of reproductive organs and flower petal senescence (Cecchini et al., 2011;Mattioli et al., 2018;Szabados & Savouré, 2010;Zhang & Becker, 2015). ...
During leaf senescence, nitrogen is remobilized and carbon backbones are replenished by amino acid catabolism, with many of the key reactions occurring in mitochondria. The intermediate Δ1‐pyrroline‐5‐carboxylate (P5C) is common to some catabolic pathways, thus linking the metabolism of several amino acids, including proline and arginine. Specifically, mitochondrial proline catabolism involves sequential action of proline dehydrogenase (ProDH) and P5C dehydrogenase (P5CDH) to produce P5C and then glutamate. Arginine catabolism produces urea and ornithine, the latter in the presence of α‐ketoglutarate being converted by ornithine δ‐aminotransferase (OAT) into P5C and glutamate. Metabolic changes during dark‐induced leaf senescence (DIS) were studied in Arabidopsis thaliana leaves of Col‐0 and in prodh1prodh2, p5cdh, and oat mutants. Progression of DIS was followed by measuring chlorophyll and proline contents for 5 days. Metabolomic profiling of 116 compounds revealed similar profiles of Col‐0 and oat metabolism, distinct from prodh1prodh2 and p5cdh metabolism. Metabolic dynamics were accelerated in p5cdh by one day. Notably, more P5C and proline accumulated in p5cdh than in prodh1prodh2. ProDH1 enzymatic activity and protein amount were significantly down‐regulated in p5cdh mutant at day 4 of DIS. Mitochondrial P5C levels appeared critical in determining the flow through interconnected amino acid remobilisation pathways to sustain senescence. This article is protected by copyright. All rights reserved.
... Proline could be converted from ornithine through the sequential activities of aminotransferase (OAT) and pyrroline-5-carboxylate(P5C) reductase (PYCR), and, in the last step of the reaction, PYCR used reduced nicotinamide adenine dinucleotide phosphate (NADPH) as a cofactor to catalyze P5C to produce proline. NADP + was produced at the same time and it conversely participated in the pentose phosphate pathway (PPP) to produce an amount of NADPH for cellular redox defense [29]. In the present study, the level of L-ornithine increased significantly in the AMR group, indicating that AMR might promote proline biosynthesis via the ornithine pathway, thereby improving the antioxidant ability of the body. ...
The effect of the Astragalus membranaceus root (AMR) on the serum metabolic profiles of preweaning calf were investigated in this study. Sixteen preweaning Holstein calves were randomly allocated into two groups with eight calves per group, and offered a control basal diet (CON group) or supplemented with 20 g superfine powder of AMR (AMR group) for 14 d. Serum samples were collected from calves on day 0, 7 and 14. Serum albumin, globulin, total protein, glucose, reduced glutathione and superoxide dismutase were evaluated. Serum metabolic profiling was analyzed using ultra-high-performance liquid chromatography-time-of-flight mass spectrometry. The results demonstrated that there were no significantly difference of total protein, glucose, reduced glu-tathione and superoxide dismutase between the CON group and AMR group (p > 0.05), while within the CON group and AMR group, serum glucose showed a continuous upward trend from 0 d to 14 d (p < 0.001). Untargeted metabolomics analysis found the metabolism of preweaning calf was considerably changed during growth, mainly including amino acid metabolism and carbohydrate metabolism and showed an increasing in protein synthesis and gluconeogenesis. 19 differential metabolites have been screened after supplementing AMR for 14 d, nine of which were up-regulated, including ornithine, L-pyroglutamic acid, L-proline and D-proline, and 10 down-regulated , containing L-kynurenine, 5-hydroxyindoleacetate, linoleic acid and 4-pyridoxic acid. Pathway analysis found these metabolites mainly participated in three primary pathways: arginine and proline metabolism, tryptophan metabolism and glutathione metabolism (p < 0.05), while linoleic acid metabolism and vitamin B6 metabolism were also enriched (0.1 < p < 0.05). Such metabolic changes reflected the enhancement of the antioxidant and anti-inflammatory capacity of prewean-ing calves.
... It has been demonstrated that the overexpression of EGFR variant III (EGFRvIII) leads to elevated ROS levels in GBM and facilitates further alterations in the genome of GBM cells [73]. Of note, POX/PRODH is inhibited by both the c-Myc oncogene and its product, miR23b* [74]. C-Myc levels are strictly correlated with the malignancy grade of gliomas, and about 60-80% of GBM display elevated c-Myc levels [75]. ...
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.
... (2S,3S)-3-Methylphenylalanine reacts with 2-oxoglutarate into L-glutamate and (3S)-2-oxo-3phenylbutanoate by 2-oxoglutarate aminotransferase in the process of glutamate providing 2-oxoglutarate for TCA cycle (68). For its correlated tissue metabolites, for instance, DL-stachydrine, as a derivative of proline, can not only be degraded to but also synthesized from glutamate (69,70). Increased transport of choline into cancer cells results in a high level of phosphocholine in tissues (a substance converted from choline via phosphorylation by choline kinase) thereby promoting cell growth and proliferation (71). ...
Esophageal squamous cell carcinoma (ESCC) is one of the most common aggressive malignancies worldwide, particularly in northern China. The absence of specific early symptoms and biomarkers leads to late-stage diagnosis, while early diagnosis and risk stratification are crucial for improving overall prognosis. We performed UPLC-MS/MS on 450 ESCC patients and 588 controls consisting of a discovery group and two validation groups to identify biomarkers for early detection and prognosis. Bioinformatics and clinical statistical methods were used for profiling metabolites and evaluating potential biomarkers. A total of 105 differential metabolites were identified as reliable biomarker candidates for ESCC with the same tendency in three cohorts, mainly including amino acids and fatty acyls. A predictive model of 15 metabolites [all-trans-13,14-dihydroretinol, (±)-myristylcarnitine, (2S,3S)-3-methylphenylalanine, 3-(pyrazol-1-yl)-L-alanine, carnitine C10:1, carnitine C10:1 isomer1, carnitine C14-OH, carnitine C16:2-OH, carnitine C9:1, formononetin, hyodeoxycholic acid, indole-3-carboxylic acid, PysoPE 20:3, PysoPE 20:3(2n isomer1), and resolvin E1] was developed by logistic regression after LASSO and random forest analysis. This model held high predictive accuracies on distinguishing ESCC from controls in the discovery and validation groups (accuracies > 89%). In addition, the levels of four downregulated metabolites [hyodeoxycholic acid, (2S,3S)-3-methylphenylalanine, carnitine C9:1, and indole-3-carboxylic acid] were significantly higher in early cancer than advanced cancer. Furthermore, three independent prognostic markers were identified by multivariate Cox regression analyses with and without clinical indicators: a high level of MG(20:4)isomer and low levels of 9,12-octadecadienoic acid and L-isoleucine correlated with an unfavorable prognosis; the risk score based on these three metabolites was able to stratify patients into low or high risk. Moreover, pathway analysis indicated that retinol metabolism and linoleic acid metabolism were prominent perturbed pathways in ESCC. In conclusion, metabolic profiling revealed that perturbed amino acids and lipid metabolism were crucial metabolic signatures of ESCC. Both panels of diagnostic and prognostic markers showed excellent predictive performances. Targeting retinol and linoleic acid metabolism pathways may be new promising mechanism-based therapeutic approaches. Thus, this study would provide novel insights for the early detection and risk stratification for the clinical management of ESCC and potentially improve the outcomes of ESCC.
... Another correlation between estrogens, collagen, and PRODH/POX was found at the level of PPAR-γ. Activation of this transcription factor is known to upregulate PRODH/POX [91]. Telmisartan, PPAR-γ ligand was found to inhibit collagen biosynthesis in breast cancer cells [92], supporting free proline for PRODH/POX-dependent functions. ...
It has been suggested that activation of estrogen receptor α (ER α) stimulates cell proliferation. In contrast, estrogen receptor β (ER β) has anti-proliferative and pro-apoptotic activity. Although the role of estrogens in estrogen receptor-positive breast cancer progression has been well established, the mechanism of their effect on apoptosis is not fully understood. It has been considered that ER status of breast cancer cells and estrogen availability might determine proline dehydrogenase/proline oxidase (PRODH/POX)-dependent apoptosis. PRODH/POX is a mitochondrial enzyme that converts proline into pyrroline-5-carboxylate (P5C). During this process, ATP (adenosine triphosphate) or ROS (reactive oxygen species) are produced, facilitating cell survival or death, respectively. However, the critical factor in driving PRODH/POX-dependent functions is proline availability. The amount of this amino acid is regulated at the level of prolidase (proline releasing enzyme), collagen biosynthesis (proline utilizing process), and glutamine, glutamate, α-ketoglutarate, and ornithine metabolism. Estrogens were found to upregulate prolidase activity and collagen biosynthesis. It seems that in estrogen receptor-positive breast cancer cells, prolidase supports proline for collagen biosynthesis, limiting its availability for PRODH/POX-dependent apoptosis. Moreover, lack of free proline (known to upregulate the transcriptional activity of hypoxia-inducible factor 1, HIF-1) contributes to downregulation of HIF-1-dependent pro-survival activity. The complex regulatory mechanism also involves PRODH/POX expression and activity. It is induced transcriptionally by p53 and post-transcriptionally by AMPK (AMP-activated protein kinase), which is regulated by ERs. The review also discusses the role of interconversion of proline/glutamate/ornithine in supporting proline to PRODH/POX-dependent functions. The data suggest that PRODH/POX-induced apoptosis is dependent on ER status in breast cancer cells.
