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Proline oxidase-induced apoptosis. Abbreviations: ROS, reactive oxygen species; TRAIL, tumor necrosis factor related apoptosis-inducing ligand; DR5, death receptor 5 NFAT, nuclear factor of activated T cells; MEK, MAP kinase; ERK, extracellular-signal regulated kinase.
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Proline is metabolized by its own specialized enzymes with their own tissue and subcellular localizations and mechanisms of regulation. The central enzyme in this metabolic system is proline oxidase, a flavin adenine dinucleotide-containing enzyme which is tightly bound to mitochondrial inner membranes. The electrons from proline can be used to gen...
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Background/aims:
The effect of impaired intracellular proline availability for proline dehydrogenase/proline oxidase (PRODH/POX)-dependent apoptosis was studied.
Methods:
We generated a constitutively knocked-down PRODH/POX MCF-7 breast cancer cell line (MCF-7shPRODH/POX) as a model to analyze the functional consequences of impaired intracellula...
Like most microorganisms, the yeast Saccharomyces cerevisiae is prototrophic for riboflavin (vitamin B2). Riboflavin auxotrophic mutants with deletions in any of the RIB genes frequently segregate colonies with improved growth. We demonstrate by reporter assays and Western blots that these suppressor mutants overexpress the plasma-membrane riboflav...
Plants generally accumulate free proline under osmotic stress conditions. Upon removal of the osmotic stress, the proline levels return to normal. In order to understand the mechanisms involved in regulating the levels of proline, we cloned and characterized a proline dehydrogenase (PDH) cDNA from Arabidop-sis thaliana (AtPDH). The 1745 bp cDNA con...
Proline, the only proteinogenic secondary amino acid, is metabolized by its own family of enzymes responding to metabolic stress and participating in metabolic signaling. Collagen in extracellular matrix, connective tissue, and bone is an abundant reservoir for proline. Matrix metalloproteinases degrading collagen are activated during stress to mak...
Proline (Pro) accumulation is a widespread response of prokaryotic and eukaryotic cells subjected to osmotic stress or dehydration. When the cells are released from stress, Pro is degraded to glutamate by Pro-dehydrogenase (ProDH) and Pyrroline-5-carboxylate dehydrogenase (P5CDH), which are both mitochondrial enzymes in eukaryotes. While P5CDH is a...
Citations
... PRODH/POX initiates both intrinsic and extrinsic apoptotic pathways, possibly through NFAT and MEK/ERK signaling [6,45,46]. The gene encoding PRODH/POX, known as PRODH, is under the transcriptional control of p53 (a main regulator of apoptosis) [47][48][49] and peroxisome proliferator-activated receptor gamma (PPARγ) [50][51][52][53]. In addition, to induce apoptotic cell death, PRODH/POX inhibits tumor progression by down-regulating growth and differentiation of tumor cells, by inhibiting the cell cycle at the G2-M checkpoint [54]. ...
Studies of cancer metabolism have focused on the production of energy and the interconversion of carbons between cell cycles. More recently, amino acid metabolism, especially non-essential amino acids (NEAAs), has been investigated, underlining their regulatory role. One of the important mediators in energy production and interconversion of carbons in the cell is Δ1-pyrroline-5-carboxylate (P5C)—the physiological intracellular intermediate of the interconversion of proline, ornithine, and glutamate. As a central component of these conversions, it links the tricarboxylic acid cycle (TCA), urea cycle (UC), and proline cycle (PC). P5C has a cyclic structure containing a tertiary nitrogen atom (N) and is in tautomeric equilibrium with the open-chain form of L-glutamate-γ-semialdehyde (GSAL). P5C is produced by P5C synthase (P5CS) from glutamate, and ornithine via ornithine δ-amino acid transferase (δOAT). It can also be converted to glutamate by P5C dehydrogenase (P5CDH). P5C is both a direct precursor of proline and a product of its degradation. The conversion of P5C to proline is catalyzed by P5C reductase (PYCR), while proline to P5C by proline dehydrogenase/oxidase (PRODH/POX). P5C-proline-P5C interconversion forms a functional redox couple. Their transformations are accompanied by the transfer of a reducing-oxidizing potential, that affect the NADP+/NADPH ratio and a wide variety of processes, e.g., the synthesis of phosphoribosyl pyrophosphate (PRPP), and purine ribonucleotides, which are crucial for DNA synthesis. This review focuses on the metabolism of P5C in the cell as an interconversion mediator of proline, glutamate, and ornithine and its role in the regulation of survival and death with particular emphasis on the metabolic context.
... -PPARγ (peroxisome proliferator-activated receptor γ) is a ligand-activated transcription factor belonging to the superfamily of the nuclear hormone receptor. It plays an important role in regulating the process of apoptosis [27,28]. -HIF-1α (hypoxia-inducible factor 1-alpha) is a transcription factor specifically activated by low oxygen concentration in the cellular environment. ...
Background: Oral squamous cell carcinoma remains a significant worldwide public health challenge, associated with high morbidity and mortality. Treatment of this type of cancer lacks effective medication. Moreover, there are very few specific biomarkers that are useful in early diagnosis or treatment optimisation. Proline metabolism may prove to be of importance in the search for new treatment modalities. Methods: To evaluate the significance of proline metabolism in the development of oral cancer, proline concentration was assessed in oral cancer tissue and normal oral mucosa. The results were compared to the clinical stage and histological grade of the tumours. Moreover, the expression of proteins involved in proline metabolism via proline dehydrogenase/oxidase (PRODH/POX, PPARγ, HIF1-α) was determined. In the next stage of the study, conducted on cell lines of tongue cancer treated with celecoxib, the aforementioned factors involved in proline metabolism were evaluated. Cellular viability and cell proliferation, as well as apoptosis, were also assessed. Results: Our research results indicate that a high intracellular proline concentration and expression of factors involved in its metabolism correlate with the clinical stage and histological grade of oral cancer. Moreover, we are the first researchers to demonstrate that celecoxib can affect proline metabolism, causing an increase in pro-apoptotic factors (PRODH/POX, PPARγ), reducing the expression of HIF-1α and activating apoptosis. Conclusions: Proline metabolism, due to its involvement in the process of apoptosis, can be of great importance in anticancer therapy. It appears that celecoxib, which influences the PRODH/POX pathway, may be a promising therapeutic compound in oral cancer treatment.
... The selection of the processes included in this metabolic network was based on databases of human metabolism such as BIGG database (Schellenberger et al., 2010) (including the human genome scale network reconstruction, recon 1 (Duarte et al., 2007)), metacyc (Caspi et al., 2016), ExPASy (Artimo et al., 2012) and KEGG (Kanehisa et al., 2012). Generic (Nelson and Cox, 2008) and specific literature was used for proline Phang et al., 2015;Phang et al., 2008), glycine and serine metabolisms Fan et al., 2014;Jain et al., 2012;Tedeschi et al., 2013). 2. Rates for some reaction or transport processes were based on extracellular measurements and used as constraints in the fitting procedure. ...
... The selection of the processes included in this metabolic network was based on databases of human metabolism such as BIGG database (Schellenberger et al., 2010) (including the human genome scale network reconstruction, recon 1 (Duarte et al., 2007)), metacyc (Caspi et al., 2016), ExPASy (Artimo et al., 2012) and KEGG (Kanehisa et al., 2012). Generic (Nelson and Cox, 2008) and specific literature was used for proline Phang et al., 2015;Phang et al., 2008), glycine and serine metabolisms Fan et al., 2014;Jain et al., 2012;Tedeschi et al., 2013). 2. Rates for some reaction or transport processes were based on extracellular measurements and used as constraints in the fitting procedure. ...
Cyclin‐dependent kinases (CDK) are rational cancer therapeutic targets fraught with the development of acquired resistance by tumor cells. Through metabolic and transcriptomic analyses, we show that the inhibition of CDK4/6 leads to a metabolic reprogramming associated with gene networks orchestrated by the MYC transcription factor. Upon inhibition of CDK4/6, an accumulation of MYC protein ensues which explains an increased glutamine metabolism, activation of the mTOR pathway and blunting of HIF‐1α‐mediated responses to hypoxia. These MYC‐driven adaptations to CDK4/6 inhibition render cancer cells highly sensitive to inhibitors of MYC, glutaminase or mTOR and to hypoxia, demonstrating that metabolic adaptations to antiproliferative drugs unveil new vulnerabilities that can be exploited to overcome acquired drug tolerance and resistance by cancer cells.
... A hypothetical proline metabolic timeline in cancer was also proposed [61]. During the early stage of cancer progression like chronic inflammation and DNA damage, PRODH could be induced by PPARγ [62] and P53 [63], respectively. PRODH was reported as a tumor suppressor gene in 2009 [64]. ...
Background:
The 5-year overall survival rates for head and neck cancer (HNC) relies on distant metastasis. Importantly, the epithelial-mesenchymal transition (EMT) is believed to be an initial step of metastasis. However, the relationship of epigenetic with EMT formation is still unexplored in HNC. This study focuses on invasive subclones of HNC cell lines through the simulation of invasion in vitro; and underlying mechanisms were analyzed including DNA methylation and gene expression profile.
Methods:
Invasive subclones of NHC cell lines were successfully obtained using transwell coated with Matrixgel. Cells invaded through 8 μm pore several times were subcultured and examined with EMT features including morphology, EMT marker genes expression, and invasive ability. Moreover, compared the profile of genes expression in parental and invasive cells was analyzed using mRNA expression array.
Results:
DNA methyltransferase 3B (DNMT 3B) was upregulated in invasive subclones and might control the 5' region of E-cadherin (E-cad) methylation and further inhibited E-cad protein expression. Interference of DNMT 3B by siRNA or miRNA 29b could reduce EMT and cell invasion. Expression array analysis revealed the most possible involved pathways in cell invasion including arginine and proline metabolism, TGF-beta, and focal adhesion.
Conclusions:
DNMT 3B might control EMT by DNA methylation manner in invasive HNC cell lines. Moreover, miR-29b mimic downregulated DNMT 3B and inhibited EMT and cell invasion indicated the role of therapeutic agent for invasive HNC. Genes identified from array data and new molecules are involved in metastasis of HNC need further validation.
... The decrease in proline observed here, especially relative to the increase in most other amino acids, may reflect enhanced degradation to not only supply precursors for polyamine biosynthesis, but perhaps to also produce pro-adipogenic ROS, in addition to the ROS from complex III [35] and NADPH oxidase [36]. In fact, it has previously been observed that the transcription factor PPARγ, a driving and necessary force of adipocyte differentiation, induces the expression of proline oxidase [37], and it has been proposed that proline oxidase is an important mediator of PPARγ-stimulated ROS production [38]. ...
The differentiation of precursor cells into mature adipocytes (adipogenesis) has been an area of increased focus, spurred by a rise in obesity rates. Though our understanding of adipogenesis and its regulation at the cellular level is growing, many questions remain, especially regarding the regulation of the metabolome. The 3T3-L1 cell line is the most well characterized cellular model of adipogenesis. Using a time course metabolomics approach, we show that the 3T3-L1 preadipocyte metabolome is greatly altered during the first 48 hours of differentiation, where cells go through about two rounds of cell division, a process known as mitotic clonal expansion. Short-chain peptides were among several small molecules that were increased during mitotic clonal expansion. Additional indicators of protein turnover were also increased, including bilirubin, a degradation product of heme-containing proteins, and 3-methylhistidine, a post-translationally modified amino acid that is not reutilized for protein synthesis. To study the origin of the peptides, we treated differentiating preadipocytes with 18O labeled water and found that 18O was incorporated into the short chain peptides, confirming them, at least in part, as products of hydrolysis. Inhibitors of the proteasome or matrix metalloproteinases affected the peptide levels during differentiation, but inhibitors of autophagy or peptidases did not. 18O was also incorporated into several choline metabolites including cytidine 5'-diphosphocholine (CDP-choline), glycerophosphocholine, and several phosphatidylcholine species, indicative of phosphatidylcholine synthesis/degradation and of flux through the CDP-choline cycle, a hallmark of proliferating cells. 18O-Tracer metabolomics further showed metabolic labeling of glutamate, suggestive of glutaminolysis, also characteristic of proliferating cells. Together, these results highlight the utility of 18O isotope labeling in combination with metabolomics to uncover changes in cellular metabolism that are not detectable by time-resolved metabolomics.
... As a result, TZDs induced apoptosis through POX dependent ROS generation [1]. The apoptotic response to PPARγ ligands is inhibited by knocking down POX, which may indicate a crucial role of POX in the PPARγ anticancer signaling [3,27,39]. Metabolic results of POX induction by PPARγ ligands differ dependently on the specificity of the ligand. Oxidized low-density lipoproteins (oxLDLs) possess lipid components, like 7-ketocholesterol (7-KC), which are responsible for peroxisome proliferator-activated receptor gamma activation. ...
Proline dehydrogenase/proline oxidase (PRODH/POX) is an enzyme catalyzing the first step of proline degradation, during which ROS and/or ATP is generated. POX is widely distributed in living organisms and is responsible for a number of regulatory processes such as redox homeostasis, osmotic adaptation, cell signaling and oxidative stress. Recent data provided evidence that POX plays an important role in carcinogenesis and tumor growth. POX may induce apoptosis in both intrinsic and extrinsic way. Due to ROS generation, POX may induce caspase-9 activity, which mediates mitochondrial apoptosis (intrinsic apoptosis pathway). POX can also stimulate TRAIL (tumor necrosis factorrelated apoptosis inducing ligand) and DR5 (death receptor 5) expression, resulting in cleavage of procaspase-8 and thus extrinsic apoptotic pathway. However, this tumor suppressor in certain environmental conditions may act as a prosurvival factor. Genotoxic, inflammatory and metabolic stress may switch POX from tumor growth inhibiting to tumor growth supporting factor. The potential mechanisms which may regulate switching of POX mode are discussed in this review.
... The expression of proline oxidase responds to p53, 52 PPARc-activating ligands, 53 and rapamycin, 54 representing respective signaling due to genotoxic, inflammatory, and nutrient stress. 55,56 Doimo et al. 57 found that 5-aminoimidazole-4-carboxamide ribonucleoside markedly stimulates OAT expression, thus representing a possible treatment for a subset of GA patients with hypomorphic alleles. Overexpression of proline oxidase (POX) results not only in cell cycle blockade and apoptosis, 58 but also produces ATP for cell maintenance. ...
In humans, deficiency of ornithine-d-aminotransferase (OAT) results in progressive degeneration of the neural retina (gyrate atrophy) with blindness in the fourth decade. In this syudy, we used the Xenopus embryonic developmental model to study functions of the OAT gene on embryonic development, Methods:We cloned and sequenced full-length OAT cDNA from Xenopus oocytes (X-OAT) and determined X-OAT expression in various developmental stages of Xenopus embryos and in a variety of adult tissues. The phenotype, gene expression of neural developmental markers and the enzymatic activity were detected by gain-of-function and loss-of-function manipulations.
we showed that X-OAT is essential for Xenopus embryonic development, and overexpression of X-OAT produces a ventralized phenotype characterized by a small head, lack of axial structure and defective expression of neural developmental markers. Using X-OAT mutants based on mutations identified in humans, we found that substitution of both Arg180 and Leu402 abrogated both X-OAT enzymatic activity and ability to modulate the developmental phenotype. X-OAT inhibits neurogenesis during Xenopus embryonic development.
X-OAT inhibits neurogenesis during Xenopus embryonic development , but it is essential for Xenopus embryonic development. The Arg 180 and Leu 402 are crucial for these effects of the OAT molecule in development.
Copyright © 2015 by Association for Research in Vision and Ophthalmology.
... Dans certaines conditions, le catabolisme de la proline peut produire l'accumulation des de la réaction de Pro-1 -pyrroline -5-pour conséquence une oxydation incomplète et donc l'accumulation de P5C dans les mitochondries.P5C est par la suite exporté vers le cytosol et convertit en proline. Cet acide aminé synthétisé est incorporé par la suite dans les mitochondries et initie le cycle (Phang et al., 2008).La génération du ROS par le cycle de Pro-P5C est initialement démontrée chez les cellules animales (Hagedorn et Phang, 1983), où la surexpression de ProDH (proline oxydase) génère l'accumulation de ROS au niveau de la mitochondrie (Donald et al., 2001;Lui et al., 2005) et de l'apoptose (Maxwell et Davis, 2000;Maxwell et Rivera, 2003;Phang et al., 2008) d'une façon dépendante de la proline. ...
... Dans certaines conditions, le catabolisme de la proline peut produire l'accumulation des de la réaction de Pro-1 -pyrroline -5-pour conséquence une oxydation incomplète et donc l'accumulation de P5C dans les mitochondries.P5C est par la suite exporté vers le cytosol et convertit en proline. Cet acide aminé synthétisé est incorporé par la suite dans les mitochondries et initie le cycle (Phang et al., 2008).La génération du ROS par le cycle de Pro-P5C est initialement démontrée chez les cellules animales (Hagedorn et Phang, 1983), où la surexpression de ProDH (proline oxydase) génère l'accumulation de ROS au niveau de la mitochondrie (Donald et al., 2001;Lui et al., 2005) et de l'apoptose (Maxwell et Davis, 2000;Maxwell et Rivera, 2003;Phang et al., 2008) d'une façon dépendante de la proline. ...
... 4,5 Seminal work from Phang's group has established that human PRODH (aka proline oxidase or POX) is a tumor suppressor protein. [5][6][7][8][9][10][11][12][13] POX expression is induced by the tumor suppressor p53, and POX itself activates intrinsic and extrinsic apoptotic pathways. 8 Crucial to the role of POX as a tumor suppressor is its ability to generate superoxide. ...
Proline dehydrogenase catalyzes the FAD-dependent oxidation of proline to Δ1- pyrroline-5-carboxylate, which is the first step of proline catabolism. Here, we report the structures of proline dehydrogenase from Deinococcus radiodurans in the oxidized state complexed with the proline analog L-tetrahydrofuroic acid and in the reduced state with the proline site vacant. The analog binds against the si face of the FAD isoalloxazine and is protected from bulk solvent by the α8 helix and the β1-α1 loop. The FAD ribityl chain adopts two conformations in the E-S complex, which is unprecedented for flavoenzymes. One of the conformations is novel for the PRODH superfamily and may contribute to the low substrate affinity of Deinococcus PRODH. Reduction of the crystalline enzyme-inhibitor complex causes profound structural changes, including 20° butterfly bending of the isoalloxazine, crankshaft rotation of the ribityl, shifting of α8 by 1.7 Å, reconfiguration of the β1-α1 loop, and rupture of the Arg291-Glu64 ion pair. These changes dramatically open the active site to facilitate product release and allow electron acceptors access to the reduced flavin. The structures suggest that the ion pair, which is conserved in the PRODH superfamily, functions as the active site gate. Mutagenesis of Glu64 to Ala decreases catalytic efficiency 27-fold, which demonstrates the importance of the gate. Mutation of Gly63 decreases efficiency 140-fold, which suggests that flexibility of the β1-α1 loop is essential for optimal catalysis. The large conformational changes that are required to form the E-S complex suggest that conformational selection plays a role in substrate recognition.
