GDPD5 is a glycerophosphocholine phosphodiesterase that osmotically regulates the osmoprotective organic osmolyte GPC

Neurotransmitter acetylcholine mediates the mummification of Ophiocordyceps sinensis-infected Thitarodes xiaojinensis larvae

Parasites can manipulate host behavior to facilitate parasite transmission. One such host-pathogen interaction occurs between the fungus Ophiocordyceps sinensis and the ghost moth Thitarodes xiaojinensis. O. sinensis is involved in the mummification process of infected host larvae. However, the underlying molecular and chemical mechanism for this phenomenon is unknown. We characterized the small molecules regulating host behaviors and the altered metabolites in infected and mummified host larvae. Lipid-related metabolites, such as phosphatidylcholine, were identified in infected and mummified larvae. Decreased levels of the neurotransmitter acetylcholine (ACh) and elevated choline levels were observed in the brains of both the infected and mummified larvae. The aberrant activity of acetylcholinesterase (AChE) and relative mRNA expression of ACE2 (acetylcholinesterase) may mediate the altered transformation between ACh and choline, leading to the brain dysfunction of mummified larvae. Caspofungin treatment inhibited the mummification of infected larvae and the activity of AChE. These findings indicate the importance of ACh in the mummification of host larvae after O. sinensis infection.IMPORTANCEOphiocordyceps sinensis-infected ghost moth larvae are manipulated to move to the soil surface with their heads up in death. A fruiting body then grows from the caterpillar's head, eventually producing conidia for dispersal. However, the underlying molecular and chemical mechanism has not been characterized. In this study, we describe the metabolic profile of Thitarodes xiaojinensis host larvae after O. sinensis infection. Altered metabolites, particularly lipid-related metabolites, were identified in infected and mummified larvae, suggesting that lipids are important in O. sinensis-mediated behavioral manipulation of host larvae. Decreased levels of the neurotransmitter acetylcholine were observed in both infected and mummified larvae brains. This suggests that altered or reduced acetylcholine can mediate brain dysfunction and lead to aberrant behavior. These results reveal the critical role of acetylcholine in the mummification process of infected host larvae.

Study on the mechanisms by which pumpkin polysaccharides regulate abnormal glucose and lipid metabolism in diabetic mice under oxidative stress

Pumpkin polysaccharide (PPe-H) can perform physiological functions through its antioxidative and hypoglycemic effects; however, the mechanisms through which PPe-H regulates abnormal glucose and lipid metabolism caused by oxidative stress injury remain unclear. In the present study, streptozotocin was used to generate an acute diabetic mouse model, and the effects of PPe-H on glucose and lipid metabolism impaired by oxidative stress in diabetic mice were studied. PPe-H significantly reduced blood glucose levels and enhanced the oral glucose tolerance of diabetic mice under stress injury (p < 0.05). The analysis of liver antioxidant enzymes showed that PPe-H significantly enhanced the activities of SOD and CAT (p < 0.05), increased the GSH level, and decreased the level of MDA (p < 0.05). Transcriptomic and metabolomic analyses of the liver tissues of mice revealed characteristic differences in the genetic and metabolic levels of the samples, which showed that PPe-H treatment may play a positive role in regulating the metabolism of methionine, cysteine, glycerol phospholipid, and linoleic acid. These results indicated that PPe-H alleviated the symptoms of hyperglycemia by regulating metabolites related to oxidative stress and glycolipid metabolism in diabetic mice.

GDE5/Gpcpd1 activity determines phosphatidylcholine composition in skeletal muscle and regulates contractile force in mice

Glycerophosphocholine (GPC) is an important precursor for intracellular choline supply in phosphatidylcholine (PC) metabolism. GDE5/Gpcpd1 hydrolyzes GPC into choline and glycerol 3-phosphate; this study aimed to elucidate its physiological function in vivo. Heterozygous whole-body GDE5-deficient mice reveal a significant GPC accumulation across tissues, while homozygous whole-body knockout results in embryonic lethality. Skeletal muscle-specific GDE5 deletion (Gde5 skKO) exhibits reduced passive force and improved fatigue resistance in electrically stimulated gastrocnemius muscles in vivo. GDE5 deficiency also results in higher glycolytic metabolites and glycogen levels, and glycerophospholipids alteration, including reduced levels of phospholipids that bind polyunsaturated fatty acids (PUFAs), such as DHA. Interestingly, this PC fatty acid compositional change is similar to that observed in skeletal muscles of denervated and Duchenne muscular dystrophy mouse models. These are accompanied by decrease of GDE5 expression, suggesting a regulatory role of GDE5 activity for glycerophospholipid profiles. Furthermore, a DHA-rich diet enhances contractile force and lowers fatigue resistance, suggesting a functional relationship between PC fatty acid composition and muscle function. Finally, skinned fiber experiments show that GDE5 loss increases the probability of the ryanodine receptor opening and lowers the maximum Ca2+-activated force. Collectively, GDE5 activity plays roles in PC and glucose/glycogen metabolism in skeletal muscle.

Glutathione and a Pool of Metabolites Partly Related to Oxidative Stress Are Associated with Low and High Myopia in an Altered Bioenergetic Environment

Oxidative stress forms part of the molecular basis contributing to the development and manifestation of myopia, a refractive error with associated pathology that is increasingly prevalent worldwide and that subsequently leads to an upsurge in degenerative visual impairment due to conditions that are especially associated with high myopia. The purpose of our study was to examine the interrelation of potential oxidative-stress-related metabolites found in the aqueous humor of high-myopic, low-myopic, and non-myopic patients within a clinical study. We conducted a cross-sectional study, selecting two sets of patients undergoing cataract surgery. The first set, which was used to analyze metabolites through an NMR assay, comprised 116 patients. A total of 59 metabolites were assigned and quantified. The PLS-DA score plot clearly showed a separation with minimal overlap between the HM and control samples. The PLS-DA model allowed us to determine 31 major metabolite differences in the aqueous humor of the study groups. Complementary statistical analysis of the data allowed us to determine six metabolites that presented significant differences among the experimental groups (p < 005). A significant number of these metabolites were discovered to have a direct or indirect connection to oxidative stress linked with conditions of myopic eyes. Notably, we identified metabolites associated with bioenergetic pathways and metabolites that have undergone methylation, along with choline and its derivatives. The second set consisted of 73 patients who underwent a glutathione assay. Here, we showed significant variations in both reduced and oxidized glutathione in aqueous humor among all patient groups (p < 0.01) for the first time. Axial length, refractive status, and complete ophthalmologic examination were also recorded, and interrelations among metabolic and clinical parameters were evaluated.

An update on Glycerophosphodiester Phosphodiesterases; From Bacteria to Human

The hydrolysis of deacylated glycerophospholipids into sn-glycerol 3-phosphate and alcohol is facilitated by evolutionarily conserved proteins known as glycerophosphodiester phosphodiesterases (GDPDs). These proteins are crucial for the pathogenicity of bacteria and for bioremediation processes aimed at degrading organophosphorus esters that pose a hazard to both humans and the environment. Additionally, GDPDs are enzymes that respond to multiple nutrients and could potentially serve as candidate genes for addressing deficiencies in zinc, iron, potassium, and especially phosphate in important plants like rice. In mammals, glycerophosphodiesterases (GDEs) play a role in regulating osmolytes, facilitating the biosynthesis of anandamine, contributing to the development of skeletal muscle, promoting the differentiation of neurons and osteoblasts, and influencing pathological states. Due to their capacity to enhance a plant's ability to tolerate various nutrient deficiencies and their potential as pharmaceutical targets in humans, GDPDs have received increased attention in recent times. This review provides an overview of the functions of GDPD families as vital and resilient enzymes that regulate various pathways in bacteria, plants, and humans.

The glycerophosphocholine acyltransferase Gpc1 contributes to phosphatidylcholine biosynthesis, long-term viability, and embedded hyphal growth in Candida albicans

Candida albicans is a commensal fungus, opportunistic pathogen, and the most common cause of fungal infection in humans. The biosynthesis of phosphatidylcholine (PC), a major eukaryotic glycerophospholipid, occurs through two primary pathways. In Saccharomyces cerevisiae and some plants, a third PC synthesis pathway, the PC deacylation/reacylation pathway (PC-DRP), has been characterized. PC-DRP begins with the acylation of the lipid turnover product, glycerophosphocholine (GPC), by the GPC acyltransferase, Gpc1, to form Lyso-PC. Lyso-PC is then acylated by lysolipid acyltransferase, Lpt1, to produce PC. Importantly, GPC, the substrate for Gpc1, is a ubiquitous metabolite available within the host. GPC is imported by C. albicans, and deletion of the major GPC transporter, Git3, leads to decreased virulence in a murine model. Here we report that GPC can be directly acylated in C. albicans by the protein product of orf19.988, a homolog of ScGpc1. Through lipidomic studies, we show loss of Gpc1 leads to a decrease in PC levels. This decrease occurs in the absence of exogenous GPC, indicating that the impact on PC levels may be greater in the human host where GPC is available. A gpc1Δ/Δ strain exhibits several sensitivities to antifungals that target lipid metabolism. Furthermore, loss of Gpc1 results in both a hyphal growth defect in embedded conditions and a decrease in long-term cell viability. These results demonstrate for the first time the importance of Gpc1 and this alternative PC biosynthesis route (PC-DRP) to the physiology of a pathogenic fungus.

Gpcpd1-GPC metabolic pathway is dysfunctional in aging and its deficiency severely perturbs glucose metabolism

Skeletal muscle plays a central role in the regulation of systemic metabolism during lifespan. With aging, this function is perturbed, initiating multiple chronic diseases. Our knowledge of mechanisms responsible for this decline is limited. Glycerophosphocholine phosphodiesterase 1 (Gpcpd1) is a highly abundant muscle enzyme that hydrolyzes glycerophosphocholine (GPC). The physiological functions of Gpcpd1 remain largely unknown. Here we show, in mice, that the Gpcpd1-GPC metabolic pathway is perturbed in aged muscles. Further, muscle-specific, but not liver- or fat-specific, inactivation of Gpcpd1 resulted in severely impaired glucose metabolism. Western-type diets markedly worsened this condition. Mechanistically, Gpcpd1 muscle deficiency resulted in accumulation of GPC, causing an 'aged-like' transcriptomic signature and impaired insulin signaling in young Gpcpd1-deficient muscles. Finally, we report that the muscle GPC levels are markedly altered in both aged humans and patients with type 2 diabetes, displaying a high positive correlation between GPC levels and chronological age. Our findings reveal that the muscle GPCPD1-GPC metabolic pathway has an important role in the regulation of glucose homeostasis and that it is impaired during aging, which may contribute to glucose intolerance in aging.

Elusive physiological role of prostatic acid phosphatase (PAP): generation of choline for sperm motility via auto-and paracrine cholinergic signaling

Prostatic acid phosphatase (PAP) exists as two splice variants, secreted PAP and transmembrane PAP, the latter of which is implicated in antinociceptive signaling in dorsal root ganglia. However, PAP is predominantly expressed in the prostate gland and the physiological role of seminal PAP, first identified in 1938, is largely unknown. Here, the author proposes that PAP, following ejaculation, functions to hydrolyze phosphocholine (PC) in seminal fluid and generate choline, which is imported by sperm via a choline transporter and converted to acetylcholine (ACh) by choline acetyltransferase. Auto- and paracrine cholinergic signaling, or choline directly, may subsequently stimulate sperm motility via α7 nicotinic ACh receptors (nAChRs) and contractility of the female reproductive tract through muscarinic ACh receptors (mAChRs). Consistent with a role of PAP in cholinergic signaling, 1) seminal vesicles secrete PC, 2) the prostate gland secretes PAP, 3) PAP specifically catalyzes the hydrolysis of PC into inorganic phosphate and choline, 4) seminal choline levels increase post-ejaculation, 5) pharmacological inhibition of choline acetyltransferase inhibits sperm motility, 6) inhibition or genetic deletion of α7 nAChRs impairs sperm motility, and 7) mAChRs are expressed in the uterus and oviduct (fallopian tube). Notably, PAP does not degrade glycerophosphocholine (GPC), the predominant choline source in the semen of rats and other mammals. Instead, uterine GPC phosphodiesterases may liberate choline from seminal GPC. In summary, the author deduces that PAP in humans, and uterine GPC phosphodiesterases in other mammals, function to generate choline for sperm cholinergic signaling, which promotes sperm motility and possibly contractility of the female reproductive tract.

Glycerophosphocholine provision rescues Candida albicans growth and signaling phenotypes associated with phosphate limitation

IMPORTANCE

Candida albicans is the most commonly isolated species from patients suffering from invasive fungal disease. C. albicans is most commonly a commensal organism colonizing a variety of niches in the human host. The fungus must compete for resources with the host flora to acquire essential nutrients such as phosphate. Phosphate acquisition and homeostasis have been shown to play a key role in C. albicans virulence, with several genes involved in these processes being required for normal virulence and several being upregulated during infection. In addition to inorganic phosphate (Pi), C. albicans can utilize the lipid-derived metabolite glycerophosphocholine (GPC) as a phosphate source. As GPC is available within the human host, we examined the role of GPC in phosphate homeostasis in C. albicans. We find that GPC can substitute for Pi by many though not all criteria and is likely a relevant physiological phosphate source for C. albicans.

An epigenetic modulator with promising therapeutic impacts against gastrointestinal cancers: A mechanistic review on microRNA-195

Due to their high prevalence, gastrointestinal cancers are one of the key causes of cancer-related death globally. The development of drug-resistant cancer cell populations is a major factor in the high mortality rate, and it affects about half of all cancer patients. Because of advances in our understanding of cancer molecular biology, non-coding RNAs (ncRNAs) have emerged as critical factors in the initiation and development of gastrointestinal cancers. Gene expression can be controlled in several ways by ncRNAs, including through epigenetic changes, interactions between microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) and proteins, and the function of lncRNAs as miRNA precursors or pseudogenes. As lncRNAs may be detected in the blood, circulating ncRNAs have emerged as a promising new class of non-invasive cancer biomarkers for use in the detection, staging, and prognosis of gastrointestinal cancers, as well as in the prediction of therapy efficacy. In this review, we assessed the role lncRNAs play in the progression, and maintenance of colorectal cancer, and how they might be used as therapeutic targets in the future.

Osmolytes: Wonder molecules to combat protein misfolding against stress conditions

The proper functioning of any protein depends on its three dimensional conformation which is achieved by the accurate folding mechanism. Keeping away from the exposed stress conditions leads to cooperative unfolding and sometimes partial folding, forming the structures like protofibrils, fibrils, aggregates, oligomers, etc. leading to several neurodegenerative diseases like Parkinson's disease, Alzheimer's, Cystic fibrosis, Huntington, Marfan syndrome, and also cancers in some cases, too. Hydration of proteins is necessary, which may be achieved by the presence of organic solutes called osmolytes within the cell. Osmolytes belong to different classes in different organisms and play their role by preferential exclusion of osmolytes and preferential hydration of water molecules and achieves the osmotic balance in the cell otherwise it may cause problems like cellular infection, cell shrinkage leading to apoptosis and cell swelling which is also the major injury to the cell. Osmolyte interacts with protein, nucleic acids, intrinsically disordered proteins by non-covalent forces. Stabilizing osmolytes increases the Gibbs free energy of the unfolded protein and decreases that of folded protein and vice versa with denaturants (urea and guanidinium hydrochloride). The efficacy of each osmolyte with the protein is determined by the calculation of m value which reflects its efficiency with protein. Hence osmolytes can be therapeutically considered and used in drugs.

GDPD5 Related to Lipid Metabolism Is a Potential Prognostic Biomarker in Neuroblastoma

Neuroblastoma (NB) is an extracranial solid tumor in children with poor prognosis in high-risk patients and its pathogenesis and prognostic markers urgently need to be explored. This study aimed to explore potential biomarkers related to NB from the aspect of lipid metabolism. Fifty-eight lipid metabolism-related differentially expressed genes between high-risk NB and non-high-risk NB in the GSE49710 dataset were analyzed using bioinformatics, including 45 down-regulated genes and 13 up-regulated genes. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis identified steroid hormone biosynthesis as an abnormal metabolic pathway in high-risk NB. Survival analysis established a three-gene prognostic model, including ACHE, GDPD5 and PIK3R1. In the test data, the AUCs of the established prognostic models used to predict patient survival at 1, 3 and 5 years were 0.84, 0.90 and 0.91, respectively. Finally, in the SH-SY5Y cell line, it was verified that overexpression of GDPD5 can inhibit cell proliferation and migration, as well as affect the lipid metabolism of SH-SY5Y, but not the sugar metabolism. hsa-miR-592 was predicted to be a potential target miRNA of GDPD5 by bioinformatics. In conclusion, this study develops a lipid-metabolism-related gene-based prognostic model for NB and demonstrates that GDPD5 inhibits SH-SY5Y proliferation and migration and may be targeted by hsa-miR-592 and inhibit SH-SY5Y fat synthesis.

The distribution and function of GDE2, a regulator of spinal motor neuron survival, are disrupted in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that affects the viability of upper and lower motor neurons. Current options for treatment are limited, necessitating deeper understanding of the mechanisms underlying ALS pathogenesis. Glycerophosphodiester phosphodiesterase 2 (GDE2 or GDPD5) is a six-transmembrane protein that acts on the cell surface to cleave the glycosylphosphatidylinositol (GPI)-anchor that tethers some proteins to the membrane. GDE2 is required for the survival of spinal motor neurons but whether GDE2 neuroprotective activity is disrupted in ALS is not known. We utilized a combination of mouse models and patient post-mortem samples to evaluate GDE2 functionality in ALS. Haplogenetic reduction of GDE2 exacerbated motor neuron degeneration and loss in SOD1G93A mice but not in control SOD1WT transgenic animals, indicating that GDE2 neuroprotective function is diminished in the context of SOD1G93A. In tissue samples from patients with ALS, total levels of GDE2 protein were equivalent to healthy controls; however, membrane levels of GDE2 were substantially reduced. Indeed, GDE2 was found to aberrantly accumulate in intracellular compartments of ALS motor cortex, consistent with a disruption of GDE2 function at the cell surface. Supporting the impairment of GDE2 activity in ALS, tandem-mass-tag mass spectrometry revealed a pronounced reduction of GPI-anchored proteins released into the CSF of patients with ALS compared with control patients. Taken together, this study provides cellular and biochemical evidence that GDE2 distribution and activity is disrupted in ALS, supporting the notion that the failure of GDE2-dependent neuroprotective pathways contributes to neurodegeneration and motor neuron loss in disease. These observations highlight the dysregulation of GPI-anchored protein pathways as candidate mediators of disease onset and progression and accordingly, provide new insight into the mechanisms underlying ALS pathogenesis.

Metabolomics study on the periplocin-induced cardiotoxicity and the compatibility of periplocin and Panax notoginseng saponins in reducing cardiotoxicity in rats by GC-MS

Periplocin, as one of the components of cardiac glycosides in Cortex periplocae, exhibited cardiotonic effects. Orally ingesting periplocin in high doses or over prolonged periods would cause serious adverse reactions, especially cardiotoxicity, which limits the applications of periplocin in clinical therapy. It has been reported that Panax notoginseng saponins could be used in compatibility with periplocin to reduce the cardiotoxicity of periplocin. To clarify the mechanisms of periplocin-induced cardiotoxicity and compatibility-pairing in reducing cardiotoxicity, the gas chromatography-mass spectrometry method was used to detect and analyze the metabolic profiles of rat plasma and urine samples after oral administration of periplocin, Panax notoginseng saponins, and the different compatibility ratios of periplocin and Panax notoginseng saponins. The multivariate statistical analysis method was used to screen and identify the biomarkers. A total of 49 potential biomarkers (28 in plasma and 21 in urine) associated with periplocin-induced cardiotoxicity were identified. Seven pathways were found through metabolomic pathway analysis. Moreover, the levels of 42 biomarkers (22 in plasma and 20 in urine) were close to normal after compatibility pairing. By analyzing the relative metabolic pathways, Panax notoginseng saponins could effectively reduce the cardiotoxicity of periplocin by affecting the tricarboxylic acid cycle, energy metabolism, and arachidonic acid metabolism.

Decrease of an intracellular organic osmolyte contributes to the cytotoxicity of organophosphate in neuroblastoma cells in vitro

Organophosphorus compounds (OP) causes prominent delayed neuropathy in vivo and cytotoxicity to neuronal cells in vitro. The primary target protein of OP's neurotoxicity is neuropathy target esterase (NTE), which can convert phosphatidylcholine (PC) to glycerophosphocholine (GPC). Recent studies reveal that autophagic cell death is important for the initiation and progression of OP-induced neurotoxicity both in vivo and in vitro. However, the mechanism of how OP induces autophagic cell death is unknown. Here it is found that GPC is an important organic osmolyte in the neuroblastoma cells, and treatment with tri-o-cresyl phosphate (TOCP), a representative OP, leads to the decrease of GPC and imbalance of extracellular and intracellular osmolality. Knockdown of GPC metabolizing enzyme glycerophosphodiester phosphodiesterase domain containing 5 (GDPD5) reverses TOCP-induced autophagic cell death, which further supports the notion that the reduced GPC level leads to the autophagic cell death. Furthermore, it is found that autophagic cell death is due to the induction of reactive oxygen species (ROS) and mitochondrial damage by imbalance of osmolality with TOCP treatment. In summary, this study reveals that TOCP treatment decreases GPC level and intracellular osmolality, which induces ROS and mitochondrial damage and leads to the cell death and neurite degradation by autophagy. This study lays the foundation for further investigations on the potential therapeutic approaches for OP neurotoxicity or NTE mutation-related neurological diseases.

Metabolome Changes during In Vivo Red Cell Aging Reveal Disruption of Key Metabolic Pathways

Understanding the mechanisms for cellular aging is a fundamental question in biology. Normal red blood cells (RBCs) survive for approximately 100 days, and their survival is likely limited by functional decline secondary to cumulative damage to cell constituents, which may be reflected in altered metabolic capabilities. To investigate metabolic changes during in vivo RBC aging, labeled cell populations were purified at intervals and assessed for abundance of metabolic intermediates using mass spectrometry. A total of 167 metabolites were profiled and quantified from cell populations of defined ages. Older RBCs maintained ATP and redox charge states at the cost of altered activity of enzymatic pathways. Time-dependent changes were identified in metabolites related to maintenance of the redox state and membrane structure. These findings illuminate the differential metabolic pathway usage associated with normal cellular aging and identify potential biomarkers to determine average RBC age and rates of RBC turnover from a single blood sample.

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Altered glycolytic, amino acid, and fatty acid metabolism occurs in normal RBC aging

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GSH pools are maintained in spite of age-dependent shifts in enzyme synthesis

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Changes in choline and GPC suggest alterations in membrane lipid metabolism

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Ophthalmate, GPC, and ergothioneine are candidate metabolic clocks for RBC aging

Glycerophosphodiesterase 3 (GDE3) is a lysophosphatidylinositol-specific ectophospholipase C acting as an endocannabinoid signaling switch

Endocannabinoid signaling plays a regulatory role in various (neuro)biological functions. 2-arachidonoylglycerol (2-AG) is the most abundant endocannabinoid, and although its canonical biosynthetic pathway involving phosphoinositide-specific phospholipase C and diacylglycerol lipase α is known, alternative pathways remain unsettled. Here, we characterize a noncanonical pathway implicating glycerophosphodiesterase 3 (GDE3, from GDPD2 gene). Human GDE3 expressed in HEK293T cell membranes catalyzed the conversion of lysophosphatidylinositol (LPI) into monoacylglycerol and inositol-1-phosphate. The enzyme was equally active against 1-acyl and 2-acyl LPI. When using 2-acyl LPI, where arachidonic acid is the predominant fatty acid, LC-MS analysis identified 2-AG as the main product of LPI hydrolysis by GDE3. Furthermore, inositol-1-phosphate release into the medium occurred upon addition of LPI to intact cells, suggesting that GDE3 is actually an ecto-lysophospholipase C. In cells expressing G-protein-coupled receptor GPR55, GDE3 abolished 1-acyl LPI-induced signaling. In contrast, upon simultaneous ex-pression of GDE3 and cannabinoid receptor CB2, 2-acyl LPI evoked the same signal as that induced by 2-AG. These data strongly suggest that, in addition to degrading the GPR55 LPI ligand, GDE3 can act as a switch between GPR55 and CB2 signaling. Coincident with a major expression of both GDE3 and CB2 in the spleen, spleens from transgenic mice lacking GDE3 displayed doubling of LPI content compared with WT mice. Decreased production of 2-AG in whole spleen was also observed, supporting the in vivo relevance of our findings. These data thus open a new research avenue in the field of endocannabinoid generation and reinforce the view of GPR55 and LPI being genuine actors of the endocannabinoid system.

Identification of human glycerophosphodiesterase 3 as an ecto phospholipase C that converts the G protein-coupled receptor 55 agonist lysophosphatidylinositol to bioactive monoacylglycerols in cultured mammalian cells

A family of glycerol-based lysolipid mediators comprises lysophosphatidic acid as a representative phospholipidic member but also a monoacylglycerol as a non-phosphorus-containing member. These critical lysolipid mediators are known to be produced from different lysophospholipids by actions of lysophospholipases C and D in mammals. Some members of the glycerophosphodiesterase (GDE) family have attracted recent attention due to their phospholipid-metabolizing activity. In this study, we found selective depletion of lysophosphatidylinositol among lysophospholipids in the culture medium of COS-7 cells transfected with a vector containing glycerophosphodiester phosphodiesterase 2 (GDPD2, GDE3). Thin-layer chromatography and liquid chromatography-tandem mass spectrometry of lipids extracted from GDE3-transfected COS-7 cells exposed to fluorescent analogs of phosphatidylinositol (PI) revealed that GDE3 acted as an ecto-type lysophospholipase C preferring endogenous lysophosphatidylinositol and PI having a long-chain acyl and a short-chain acyl group rather than endogenous PI and its fluorescent analog having two long chain acyl groups. In MC3T3-E1 cells cultured with an osteogenic or mitogenic medium, mRNA expression of GDE3 was increased by culturing in 10% fetal bovine serum for several days, concomitant with increased activity of ecto-lysophospholipase C, converting arachidonoyl-lysophosphatidylinositol, a physiological agonist of G protein-coupled receptor 55, to arachidonoylglycerol, a physiological agonist of cannabinoid receptors 1 and 2. We suggest that GDE3 acts as an ecto-lysophospholipase C, by switching signaling from lysophosphatidylinositol to that from arachidonoylglycerol in an opposite direction in mouse bone remodeling.

Human GDPD3 overexpression promotes liver steatosis by increasing lysophosphatidic acid production and fatty acid uptake

The glycerol phosphate pathway produces more than 90% of the liver triacylglycerol (TAG). LysoPA, an intermediate in this pathway, is produced by glycerol-3-phosphate acyltransferase. Glycerophosphodiester phosphodiesterase domain containing 3 (GDPD3), whose gene was recently cloned, contains lysophospholipase D activity, which produces LysoPA from lysophospholipids. Whether human GDPD3 plays a role in hepatic TAG homeostasis is unknown. We hypothesized that human GDPD3 increases LysoPA production and availability in the glycerol phosphate pathway, promoting TAG biosynthesis. To test our hypothesis, we infected C57BL/6J mice with adeno-associated virus encoding a hepatocyte-specific albumin promoter that drives GFP (control) or FLAG-tagged human GDPD3 overexpression and fed the mice chow or a Western diet to induce hepatosteatosis. Hepatic human GDPD3 overexpression induced LysoPA production and increased FA uptake and incorporation into TAG in mouse hepatocytes and livers, ultimately exacerbating Western diet-induced liver steatosis. Our results also showed that individuals with hepatic steatosis have increased GDPD3 mRNA levels compared with individuals without steatosis. Collectively, these findings indicate that upregulation of GDPD3 expression may play a key role in hepatic TAG accumulation and may represent a molecular target for managing hepatic steatosis.

Study on amniotic fluid metabolism in the second trimester of Trisomy 21

BACKGROUND

Trisomy 21 is a common aneuploid condition in humans and accounts for approximately one quarter of all aneuploid live births. To date, early diagnosis of Trisomy 21 remains a challenging task. Metabolomics may prove an innovative tool to study the early pathophysiology of Trisomy 21 at a functional level.

METHODS

Ultra-performance liquid chromatography coupled with mass spectrometer (UPLC-MS) was used for untargeted metabolomic analysis of amniotic fluid samples from women having normal and trisomy 21 fetuses.

RESULTS

Many significantly changed metabolites were identified between amniotic fluid samples from Trisomy 21 pregnancies and normal euploid pregnancies, such as generally lower levels of several steroid hormones and their derivatives, higher levels of glutathione catabolites coupled with lower levels of gamma-glutamyl amino acids, and increased levels of phospholipid catabolites, sugars, and dicarboxylic acids. The identification of a human milk oligosaccharide in amniotic fluid may worth further investigation, since confirmation of this observation may have significant implications for regulation of fetal development.

CONCLUSIONS

The metabolisms in amniotic fluid from Trisomy 21 and normal pregnancies are quite different, and some of the significantly changed metabolites may be considered as candidates of early diagnostic biomarkers for Trisomy 21.

Sequence-dependent trafficking and activity of GDE2, a GPI-specific phospholipase promoting neuronal differentiation

GDE2 (also known as GDPD5) is a multispanning membrane phosphodiesterase with phospholipase D-like activity that cleaves select glycosylphosphatidylinositol (GPI)-anchored proteins and thereby promotes neuronal differentiation both in vitro and in vivo GDE2 is a prognostic marker in neuroblastoma, while loss of GDE2 leads to progressive neurodegeneration in mice; however, its regulation remains unclear. Here, we report that, in immature neuronal cells, GDE2 undergoes constitutive endocytosis and travels back along both fast and slow recycling routes. GDE2 trafficking is directed by C-terminal tail sequences that determine the ability of GDE2 to cleave GPI-anchored glypican-6 (GPC6) and induce a neuronal differentiation program. Specifically, we define a GDE2 truncation mutant that shows aberrant recycling and is dysfunctional, whereas a consecutive deletion results in cell-surface retention and gain of GDE2 function, thus uncovering distinctive regulatory sequences. Moreover, we identify a C-terminal leucine residue in a unique motif that is essential for GDE2 internalization. These findings establish a mechanistic link between GDE2 neuronal function and sequence-dependent trafficking, a crucial process gone awry in neurodegenerative diseases.This article has an associated First Person interview with the first author of the paper.

Focus on the glycerophosphocholine pathway in choline phospholipid metabolism of cancer

Activated choline metabolism is a hallmark of carcinogenesis and tumor progression, which leads to elevated levels of phosphocholine and glycerophosphocholine in all types of cancer tested so far. Magnetic resonance spectroscopy applications have played a key role in detecting these elevated choline phospholipid metabolites. To date, the majority of cancer-related studies have focused on phosphocholine and the Kennedy pathway, which constitutes the biosynthesis pathway for membrane phosphatidylcholine. Fewer and more recent studies have reported on the importance of glycerophosphocholine in cancer. In this review article, we summarize the recent literature on glycerophosphocholine metabolism with respect to its cancer biology and its detection by magnetic resonance spectroscopy applications.

Dynamic Analysis of Metabolic Response in Gastric Ulcer (GU) Rats with Electroacupuncture Treatment Using 1H NMR-Based Metabolomics

Gastric ulcer (GU), a common digestive disease, has a high incidence and seriously endangers health of human. According to the previous studies, it has been proved that electroacupuncture at acupoints of stomach meridian had a good effect on GU. However, there are few published studies on metabolic response in gastric ulcer (GU) rats with electroacupuncture treatment. Herein, we observed the metabolic profiles in biological samples (stomach, liver, and kidney) of GU rats with electroacupuncture treatment by ¹H NMR metabolomics combined with pathological examination. The male SD rats were induced by intragastric administration of 70% ethanol after fasting for 24 hours and treated by electroacupuncture at Zusanli (ST36) and Liangmen (ST21) for 1 day, 4 days, or 7 days, respectively. And the conventional histopathological examinations as well as metabolic pathways assays were also performed. We found that GU rats were basically cured after electroacupuncture treatment for 4 days and had a complete recovery after electroacupuncture treatment for 7 days by being modulated comprehensive metabolic changes, involved in the function of neurotransmitters, energy metabolism, cells metabolism, antioxidation, tissue repairing, and other metabolic pathways. These findings may be helpful to facilitate the mechanism elucidating of electroacupuncture treatment on GU.

Pancreatic and mucosal enzymes in choline phospholipid digestion

The digestion of choline phospholipids is important for choline homeostasis, lipid signaling, postprandial lipid and energy metabolism, and interaction with intestinal bacteria. The digestion is mediated by the combined action of pancreatic and mucosal enzymes. In the proximal small intestine, hydrolysis of phosphatidylcholine (PC) to 1-lyso-PC and free fatty acid (FFA) by the pancreatic phospholipase A₂ IB coincides with the digestion of the dietary triacylglycerols by lipases, but part of the PC digestion is extended and must be mediated by other enzymes as the jejunoileal brush-border phospholipase B/lipase and mucosal secreted phospholipase A₂ X. Absorbed 1-lyso-PC is partitioned in the mucosal cells between degradation and reacylation into chyle PC. Reutilization of choline for hepatic bile PC synthesis, and the reacylation of 1-lyso-PC into chylomicron PC by the lyso-PC-acyl-CoA-acyltransferase 3 are important features of choline recycling and postprandial lipid metabolism. The role of mucosal enzymes is emphasized by sphingomyelin (SM) being sequentially hydrolyzed by brush-border alkaline sphingomyelinase (alk-SMase) and neutral ceramidase to sphingosine and FFA, which are well absorbed. Ceramide and sphingosine-1-phosphate are generated and are both metabolic intermediates and important lipid messengers. Alk-SMase has anti-inflammatory effects that counteract gut inflammation and tumorigenesis. These may be mediated by multiple mechanisms including generation of sphingolipid metabolites and suppression of autotaxin induction and lyso-phosphatidic acid formation. Here we summarize current knowledge on the roles of pancreatic and mucosal enzymes in PC and SM digestion, and its implications in intestinal and liver diseases, bacterial choline metabolism in the gut, and cholesterol absorption.

GDE5 inhibition accumulates intracellular glycerophosphocholine and suppresses adipogenesis at a mitotic clonal expansion stage

Mammalian glycerophosphodiesterases (GDEs) were recently shown to be involved in multiple cellular signaling pathways. This study showed that decreased GDE5 expression results in accumulation of intracellular glycerophosphocholine (GPC), showing that GDE5 is actively involved in GPC/choline metabolism in 3T3-L1 adipocytes. Using 3T3-L1 adipocytes, we further studied the biological significance of GPC/choline metabolism during adipocyte differentiation. Inhibition of GDE5 suppressed the formation of lipid droplets, which is accompanied by the decreased expression of adipocyte differentiation markers. We further showed that the decreased GDE5 expression suppressed mitotic clonal expansion (MCE) of preadipocytes. Decreased expression of CTP: phosphocholine cytidylyltransferase (CCTβ), a rate-limiting enzyme for phosphatidylcholine (PC) synthesis, is similarly able to inhibit MCE and PC synthesis; however, the decreased GDE5 expression resulted in accumulation of intracellular GPC but did not affect PC synthesis. Furthermore, we showed that mRNAs of proteoglycans and transporters for organic osmolytes are significantly upregulated and that intracellular amino acids and urea levels are altered in response to GDE5 inhibition. Finally, we showed that reduction of GDE5 expression increased lactate dehydrogenase release from preadipocytes. These observations indicate that decreased GDE5 expression can suppress adipocyte differentiation not through the PC pathway but possibly by intracellular GPC accumulation. These results provide insight into the roles of mammalian GDEs and their dependence upon osmotic regulation by altering intracellular GPC levels.

Transcriptome reprogramming during severe dehydration contributes to physiological and metabolic changes in the resurrection plant Haberlea rhodopensis

BACKGROUND

Water shortage is a major factor that harms agriculture and ecosystems worldwide. Plants display various levels of tolerance to water deficit, but only resurrection plants can survive full desiccation of their vegetative tissues. Haberlea rhodopensis, an endemic plant of the Balkans, is one of the few resurrection plants found in Europe. We performed transcriptomic analyses of this species under slight, severe and full dehydration and recovery to investigate the dynamics of gene expression and associate them with existing physiological and metabolomics data.

RESULTS

De novo assembly yielded a total of 142,479 unigenes with an average sequence length of 1034 nt. Among them, 18,110 unigenes were differentially expressed. Hierarchical clustering of all differentially expressed genes resulted in seven clusters of dynamic expression patterns. The most significant expression changes, involving more than 15,000 genes, started at severe dehydration (~ 20% relative water content) and were partially maintained at full desiccation (< 10% relative water content). More than a hundred pathways were enriched and functionally organized in a GO/pathway network at the severe dehydration stage. Transcriptomic changes in key pathways were analyzed and discussed in relation to metabolic processes, signal transduction, quality control of protein and DNA repair in this plant during dehydration and rehydration.

CONCLUSION

Reprograming of the transcriptome occurs during severe dehydration, resulting in a profound alteration of metabolism toward alternative energy supply, hormone signal transduction, and prevention of DNA/protein damage under very low cellular water content, underlying the observed physiological and metabolic responses and the resurrection behavior of H. rhodopensis.

Difference of Liver and Kidney Metabolic Profiling in Chronic Atrophic Gastritis Rats between Acupuncture and Moxibustion Treatment

Acupuncture and moxibustion proved to be very effective in chronic atrophic gastritis (CAG). According to the Chinese traditional medicine theory, chronic diseases have an influence on the function of liver and kidney. However, there is little research to demonstrate this theory. This study is aimed at assessing the ¹H NMR-based metabolic profiling in liver and kidney of CAG rats and comparing the difference between electroacupuncture and moxibustion treatment. Male SD rats were subjected to CAG modeling by intragastric administration of mixture of 2% sodium salicylate and 30% alcohol coupled with compulsive sporting and irregular fasting for 12 weeks and then treated by electroacupuncture or moxibustion at Liangmen (ST 21) and Zusanli (ST 36) acupoints for 2 weeks. A ¹H NMR analysis of liver and kidney samples along with histopathological examination and molecular biological assay was employed to assess and compare the therapeutic effects of electroacupuncture and moxibustion. CAG brought characterization of metabolomic signatures in liver and kidney of rats. Both electroacupuncture and moxibustion treatment were found to normalize the CAG-induced changes by restoring energy metabolism, neurotransmitter metabolism, antioxidation metabolism, and other metabolism, while the moxibustion treatment reversed more metabolites related to energy metabolism in liver than electroacupuncture treatment. CAG did have influence on liver and kidney of rats. Both of these treatments had good effects on CAG by reversing the CAG-induced perturbation in liver and kidney. For regulating the energy metabolism in liver, the moxibustion played more important role than electroacupuncture treatment.

From yeast to humans - roles of the Kennedy pathway for phosphatidylcholine synthesis

The major phospholipid present in most eukaryotic membranes is phosphatidylcholine (PC), comprising ~ 50% of phospholipid content. PC metabolic pathways are highly conserved from yeast to humans. The main pathway for the synthesis of PC is the Kennedy (CDP-choline) pathway. In this pathway, choline is converted to phosphocholine by choline kinase, phosphocholine is metabolized to CDP-choline by the rate-determining enzyme for this pathway, CTP:phosphocholine cytidylyltransferase, and cholinephosphotransferase condenses CDP-choline with diacylglycerol to produce PC. This Review discusses how PC synthesis via the Kennedy pathway is regulated, its role in cellular and biological processes, as well as diseases known to be associated with defects in PC synthesis. Finally, we present the first model for the making of a membrane via PC synthesis.

Mammalian enzymes responsible for the biosynthesis of N-acylethanolamines

Bioactive N-acylethanolamines (NAEs) are ethanolamides of long-chain fatty acids, including palmitoylethanolamide, oleoylethanolamide and anandamide. In animal tissues, NAEs are biosynthesized from membrane phospholipids. The classical "transacylation-phosphodiesterase" pathway proceeds via N-acyl-phosphatidylethanolamine (NAPE), which involves the actions of two enzymes, NAPE-generating Ca²⁺-dependent N-acyltransferase (Ca-NAT) and NAPE-hydrolyzing phospholipase D (NAPE-PLD). Recent identification of Ca-NAT as Ɛ isoform of cytosolic phospholipase A₂ enabled the further molecular biological approaches toward this enzyme. In addition, Ca²⁺-independent NAPE formation was shown to occur by N-acyltransferase activity of a group of proteins named phospholipase A/acyltransferases (PLAAT)-1-5. The analysis of NAPE-PLD-deficient mice confirmed that NAEs can be produced through multi-step pathways bypassing NAPE-PLD. The NAPE-PLD-independent pathways involved three members of the glycerophosphodiesterase (GDE) family (GDE1, GDE4 and GDE7) as well as α/β-hydrolase domain-containing protein (ABHD)4. In this review article, we will focus on recent progress made and latest insights in the enzymes involved in NAE synthesis and their further characterization.

Molecular Effects of Doxorubicin on Choline Metabolism in Breast Cancer

Abnormal choline phospholipid metabolism is a hallmark of cancer. The magnetic resonance spectroscopy (MRS) detected total choline (tCho) signal can serve as an early noninvasive imaging biomarker of chemotherapy response in breast cancer. We have quantified the individual components of the tCho signal, glycerophosphocholine (GPC), phosphocholine (PC) and free choline (Cho), before and after treatment with the commonly used chemotherapeutic drug doxorubicin in weakly metastatic human MCF7 and triple-negative human MDA-MB-231 breast cancer cells. While the tCho concentration did not change following doxorubicin treatment, GPC significantly increased and PC decreased. Of the two phosphatidylcholine-specific PLD enzymes, only PLD1, but not PLD2, mRNA was down-regulated by doxorubicin treatment. For the two reported genes encoding GPC phosphodiesterase, the mRNA of GDPD6, but not GDPD5, decreased following doxorubicin treatment. mRNA levels of choline kinase α (ChKα), which converts Cho to PC, were reduced following doxorubicin treatment. PLD1 and ChKα protein levels decreased following doxorubicin treatment in a concentration dependent manner. Treatment with the PLD1 specific inhibitor VU0155069 sensitized MCF7 and MDA-MB-231 breast cancer cells to doxorubicin-induced cytotoxicity. Low concentrations of 100 nM of doxorubicin increased MDA-MB-231 cell migration. GDPD6, but not PLD1 or ChKα, silencing by siRNA abolished doxorubicin-induced breast cancer cell migration. Doxorubicin induced GPC increase and PC decrease are caused by reductions in PLD1, GDPD6, and ChKα mRNA and protein expression. We have shown that silencing or inhibiting these genes/proteins can promote drug effectiveness and reduce adverse drug effects. Our findings emphasize the importance of detecting PC and GPC individually.

Targeting Phospholipid Metabolism in Cancer

All cancers tested so far display abnormal choline and ethanolamine phospholipid metabolism, which has been detected with numerous magnetic resonance spectroscopy (MRS) approaches in cells, animal models of cancer, as well as the tumors of cancer patients. Since the discovery of this metabolic hallmark of cancer, many studies have been performed to elucidate the molecular origins of deregulated choline metabolism, to identify targets for cancer treatment, and to develop MRS approaches that detect choline and ethanolamine compounds for clinical use in diagnosis and treatment monitoring. Several enzymes in choline, and recently also ethanolamine, phospholipid metabolism have been identified, and their evaluation has shown that they are involved in carcinogenesis and tumor progression. Several already established enzymes as well as a number of emerging enzymes in phospholipid metabolism can be used as treatment targets for anticancer therapy, either alone or in combination with other chemotherapeutic approaches. This review summarizes the current knowledge of established and relatively novel targets in phospholipid metabolism of cancer, covering choline kinase α, phosphatidylcholine-specific phospholipase D1, phosphatidylcholine-specific phospholipase C, sphingomyelinases, choline transporters, glycerophosphodiesterases, phosphatidylethanolamine N-methyltransferase, and ethanolamine kinase. These enzymes are discussed in terms of their roles in oncogenic transformation, tumor progression, and crucial cancer cell properties such as fast proliferation, migration, and invasion. Their potential as treatment targets are evaluated based on the current literature.

Utilization of glycerophosphodiesters by Staphylococcus aureus

The facultative pathogen Staphylococcus aureus colonizes the human anterior nares and causes infections of various organ systems. Which carbon, energy, and phosphate sources can be utilized by S. aureus in nutrient-poor habitats has remained largely unknown. We describe that S. aureus secretes a glycerophosphodiesterase (glycerophosphodiester phosphodiesterase, EC 3.1.4.46), GlpQ, degrading the glycerophosphodiester (GPD) head groups of phospholipids such as human phosphatidylcholine (GroPC). Deletion of glpQ completely abolished the GroPC-degrading activity in S. aureus culture supernatants. GroPC has been detected in human tissues and body fluids probably as a result of phospholipid remodelling and degradation. Notably, GroPC promoted S. aureus growth under carbon- and phosphate-limiting conditions in a GlpQ-dependent manner indicating that GlpQ permits S. aureus to utilize GPD-derived glycerol-3-phosphate as a carbon and phosphate sources. Thus, S. aureus can use a broader spectrum of nutrients than previously thought which underscores its capacity to adapt to the highly variable and nutrient-poor surroundings.

Glycerophosphodiesterase GDE2 Promotes Neuroblastoma Differentiation through Glypican Release and Is a Marker of Clinical Outcome

Neuroblastoma is a pediatric embryonal malignancy characterized by impaired neuronal differentiation. A better understanding of neuroblastoma differentiation is essential for developing new therapeutic approaches. GDE2 (encoded by GDPD5) is a six-transmembrane-domain glycerophosphodiesterase that promotes embryonic neurogenesis. We find that high GDPD5 expression is strongly associated with favorable outcome in neuroblastoma. GDE2 induces differentiation of neuroblastoma cells, suppresses cell motility, and opposes RhoA-driven neurite retraction. GDE2 alters the Rac-RhoA activity balance and the expression of multiple differentiation-associated genes. Mechanistically, GDE2 acts by cleaving (in cis) and releasing glycosylphosphatidylinositol-anchored glypican-6, a putative co-receptor. A single point mutation in the ectodomain abolishes GDE2 function. Our results reveal GDE2 as a cell-autonomous inducer of neuroblastoma differentiation with prognostic significance and potential therapeutic value.

The Baseplate of Lactobacillus delbrueckii Bacteriophage Ld17 Harbors a Glycerophosphodiesterase

Glycerophosphodiester phosphodiesterases (GDPDs; EC 3.1.4.46) typically hydrolyze glycerophosphodiesters to sn-glycerol 3-phosphate (Gro3P) and their corresponding alcohol during patho/physiological processes in bacteria and eukaryotes. GDPD(-like) domains were identified in the structural particle of bacterial viruses (bacteriophages) specifically infecting Gram-positive bacteria. The GDPD of phage 17 (Ld17; GDPDLd17), representative of the group b Lactobacillus delbrueckii subsp. bulgaricus (Ldb)-infecting bacteriophages, was shown to hydrolyze, besides the simple glycerophosphodiester, two complex surface-associated carbohydrates of the Ldb17 cell envelope: the Gro3P decoration of the major surface polysaccharide d-galactan and the oligo(glycerol phosphate) backbone of the partially glycosylated cell wall teichoic acid, a minor Ldb17 cell envelope component. Degradation of cell wall teichoic acid occurs according to an exolytic mechanism, and Gro3P substitution is presumed to be inhibitory for GDPDLd17 activity. The presence of the GDPDLd17 homotrimer in the viral baseplate structure involved in phage-host interaction together with the dependence of native GDPD activity, adsorption, and efficiency of plating of Ca(2+) ions supports a role for GDPDLd17 activity during phage adsorption and/or phage genome injection. In contrast to GDPDLd17, we could not identify any enzymatic activity for the GDPD-like domain in the neck passage structure of phage 340, a 936-type Lactococcus lactis subsp. lactis bacteriophage.

Targeting choline phospholipid metabolism: GDPD5 and GDPD6 silencing decrease breast cancer cell proliferation, migration, and invasion

Abnormal choline phospholipid metabolism is associated with oncogenesis and tumor progression. We have investigated the effects of targeting choline phospholipid metabolism by silencing two glycerophosphodiesterase genes, GDPD5 and GDPD6, using small interfering RNA (siRNA) in two breast cancer cell lines, MCF-7 and MDA-MB-231. Treatment with GDPD5 and GDPD6 siRNA resulted in significant increases in glycerophosphocholine (GPC) levels, and no change in the levels of phosphocholine or free choline, which further supports their role as GPC-specific regulators in breast cancer. The GPC levels were increased more than twofold during GDPD6 silencing, and marginally increased during GDPD5 silencing. DNA laddering was negative in both cell lines treated with GDPD5 and GDPD6 siRNA, indicating absence of apoptosis. Treatment with GDPD5 siRNA caused a decrease in cell viability in MCF-7 cells, while GDPD6 siRNA treatment had no effect on cell viability in either cell line. Decreased cell migration and invasion were observed in MDA-MB-231 cells treated with GDPD5 or GDPD6 siRNA, where a more pronounced reduction in cell migration and invasion was observed under GDPD5 siRNA treatment as compared with GDPD6 siRNA treatment. In conclusion, GDPD6 silencing increased the GPC levels in breast cancer cells more profoundly than GDPD5 silencing, while the effects of GDPD5 silencing on cell viability/proliferation, migration, and invasion were more severe than those of GDPD6 silencing. Our results suggest that silencing GDPD5 and GDPD6 alone or in combination may have potential as a new molecular targeting strategy for breast cancer treatment. Copyright © 2016 John Wiley & Sons, Ltd.

Expression and Characterization of a Novel Glycerophosphodiester Phosphodiesterase from Pyrococcus furiosus DSM 3638 That Possesses Lysophospholipase D Activity

Glycerophosphodiester phosphodiesterases (GDPD) are enzymes which degrade various glycerophosphodiesters to produce glycerol-3-phosphate and the corresponding alcohol moiety. Apart from this, a very interesting finding is that this enzyme could be used in the degradation of toxic organophosphorus esters, which has resulted in much attention on the biochemical and application research of GDPDs. In the present study, a novel GDPD from Pyrococcus furiosus DSM 3638 (pfGDPD) was successfully expressed in Escherichia coli and biochemically characterized. This enzyme hydrolyzed bis(p-nitrophenyl) phosphate, one substrate analogue of organophosphorus diester, with an optimal reaction temperature 55 °C and pH 8.5. The activity of pfGDPD was strongly dependent on existing of bivalent cations. It was strongly stimulated by Mn(2+) ions, next was Co(2+) and Ni(2+) ions. Further investigations were conducted on its substrate selectivity towards different phospholipids. The results indicated that except of glycerophosphorylcholine (GPC), this enzyme also possessed lysophospholipase D activity toward both sn1-lysophosphatidylcholine (1-LPC) and sn2-lysophosphatidylcholine (2-LPC). Higher activity was found for 1-LPC than 2-LPC; however, no hydrolytic activity was found for phosphatidylcholine (PC). Molecular docking based on the 3D-modeled structure of pfGDPD was conducted in order to provide a structural foundation for the substrate selectivity.

GPI-AP release in cellular, developmental, and reproductive biology

Glycosylphosphatidylinositol-anchored proteins (GPI-APs) contain a covalently linked GPI anchor located on outer cell membranes. GPI-APs are ubiquitously conserved from protozoa to vertebrates and are critical for physiological events such as development, immunity, and neurogenesis in vertebrates. Both membrane-anchored and soluble GPI-APs play a role in regulating their protein conformation and functional properties. Several pathways mediate the release of GPI-APs from the plasma membrane by vesiculation or cleavage. Phospholipases and putative substrate-specific GPI-AP-releasing enzymes, such as NOTUM, glycerophosphodiesterase 2, and angiotensin-converting enzyme, have been characterized in mammals. Here, the protein modifications resulting from the cleavage of the GPI anchor are discussed in the context of its physiological functions.

Downregulation of hepatic betaine:homocysteine methyltransferase (BHMT) expression in taurine-deficient mice is reversed by taurine supplementation in vivo

The cysteine dioxygenase (Cdo1)-null and the cysteine sulfinic acid decarboxylase (Csad)-null mouse are not able to synthesize hypotaurine/taurine by the cysteine/cysteine sulfinate pathway and have very low tissue taurine levels. These mice provide excellent models for studying the effects of taurine on biological processes. Using these mouse models, we identified betaine:homocysteine methyltransferase (BHMT) as a protein whose in vivo expression is robustly regulated by taurine. BHMT levels are low in liver of both Cdo1-null and Csad-null mice, but are restored to wild-type levels by dietary taurine supplementation. A lack of BHMT activity was indicated by an increase in the hepatic betaine level. In contrast to observations in liver of Cdo1-null and Csad-null mice, BHMT was not affected by taurine supplementation of primary hepatocytes from these mice. Likewise, CSAD abundance was not affected by taurine supplementation of primary hepatocytes, although it was robustly upregulated in liver of Cdo1-null and Csad-null mice and lowered to wild-type levels by dietary taurine supplementation. The mechanism by which taurine status affects hepatic CSAD and BHMT expression appears to be complex and to require factors outside of hepatocytes. Within the liver, mRNA abundance for both CSAD and BHMT was upregulated in parallel with protein levels, indicating regulation of BHMT and CSAD mRNA synthesis or degradation.

In vivo spectroscopy and NMR metabolite fingerprinting approaches to connect the dynamics of photosynthetic and metabolic phenotypes in resurrection plant Haberlea rhodopensis during desiccation and recovery

The resurrection plant Haberlea rhodopensis was used to study dynamics of drought response of photosynthetic machinery parallel with changes in primary metabolism. A relation between leaf water content and photosynthetic performance was established, enabling us to perform a non-destructive evaluation of the plant water status during stress. Spectroscopic analysis of photosynthesis indicated that, at variance with linear electron flow (LEF) involving photosystem (PS) I and II, cyclic electron flow around PSI remains active till almost full dry state at the expense of the LEF, due to the changed protein organization of photosynthetic apparatus. We suggest that, this activity could have a photoprotective role and prevent a complete drop in adenosine triphosphate (ATP), in the absence of LEF, to fuel specific energy-dependent processes necessary for the survival of the plant, during the late states of desiccation. The NMR fingerprint shows the significant metabolic changes in several pathways. Due to the declining of LEF accompanied by biosynthetic reactions during desiccation, a reduction of the ATP pool during drought was observed, which was fully and quickly recovered after plants rehydration. We found a decline of valine accompanied by lipid degradation during stress, likely to provide alternative carbon sources for sucrose accumulation at late stages of desiccation. This accumulation, as well as the increased levels of glycerophosphodiesters during drought stress could provide osmoprotection to the cells.

New members of the mammalian glycerophosphodiester phosphodiesterase family: GDE4 and GDE7 produce lysophosphatidic acid by lysophospholipase D activity

The known mammalian glycerophosphodiester phosphodiesterases (GP-PDEs) hydrolyze glycerophosphodiesters. In this study, two novel members of the mammalian GP-PDE family, GDE4 and GDE7, were isolated, and the molecular basis of mammalian GP-PDEs was further explored. The GDE4 and GDE7 sequences are highly homologous and evolutionarily close. GDE4 is expressed in intestinal epithelial cells, spermatids, and macrophages, whereas GDE7 is particularly expressed in gastro-esophageal epithelial cells. Unlike other mammalian GP-PDEs, GDE4 and GDE7 cannot hydrolyze either glycerophosphoinositol or glycerophosphocholine. Unexpectedly, both GDE4 and GDE7 show a lysophospholipase D activity toward lysophosphatidylcholine (lyso-PC). We purified the recombinant GDE4 and GDE7 proteins and show that these enzymes can hydrolyze lyso-PC to produce lysophosphatidic acid (LPA). Further characterization of purified recombinant GDE4 showed that it can also convert lyso-platelet-activating factor (1-O-alkyl-sn-glycero-3-phosphocholine; lyso-PAF) to alkyl-LPA. These data contribute to our current understanding of mammalian GP-PDEs and of their physiological roles via the control of lyso-PC and lyso-PAF metabolism in gastrointestinal epithelial cells and macrophages.

Alterations of choline phospholipid metabolism in endometrial cancer are caused by choline kinase alpha overexpression and a hyperactivated deacylation pathway

Metabolic rearrangements subsequent to malignant transformation are not well characterized in endometrial cancer. Identification of altered metabolites could facilitate imaging-guided diagnosis, treatment surveillance, and help to identify new therapeutic options. Here, we used high-resolution magic angle spinning magnetic resonance mass spectroscopy on endometrial cancer surgical specimens and normal endometrial tissue to investigate the key modulators that might explain metabolic changes, incorporating additional investigations using qRT-PCR, Western blotting, tissue microarrays (TMA), and uptake assays of [(3)H]-labeled choline. Lipid metabolism was severely dysregulated in endometrial cancer with various amino acids, inositols, nucleobases, and glutathione also altered. Among the most important lipid-related alterations were increased phosphocholine levels (increased 70% in endometrial cancer). Mechanistic investigations revealed that changes were not due to altered choline transporter expression, but rather due to increased expression of choline kinase α (CHKA) and an activated deacylation pathway, as indicated by upregulated expression of the catabolic enzymes LYPLA1, LYPLA2, and GPCPD1. We confirmed the significance of CHKA overexpression on a TMA, including a large series of endometrial hyperplasia, atypical hyperplasia, and adenocarcinoma tissues, supporting a role for CHKA in malignant transformation. Finally, we documented several-fold increases in the uptake of [(3)H]choline in endometrial cancer cell lines compared with normal endometrial stromal cells. Our results validate deregulated choline biochemistry as an important source of noninvasive imaging biomarkers for endometrial cancer.

Metabolite localization by atmospheric pressure high-resolution scanning microprobe matrix-assisted laser desorption/ionization mass spectrometry imaging in whole-body sections and individual organs of the rove beetle Paederus riparius

Mass spectrometry imaging provides for non-targeted, label-free chemical imaging. In this study, atmospheric pressure high-resolution scanning microprobe matrix-assisted laser desorption/ionization mass spectrometry imaging (AP-SMALDI MSI) was used for the first time to describe the chemical distribution of the defensive compounds pederin, pseudopederin, and pederon in tissue sections (16 μm thick) of the rove beetle Paederus riparius. The whole-insect tissue section was scanned with a 20-μm step size. Mass resolution of the orbital trapping mass spectrometer was set to 100,000 at m/z 200. Additionally, organ-specific compounds were identified for brain, nerve cord, eggs, gut, ovaries, and malpighian tubules. To confirm the distribution of the specific compounds, individual organs from the insect were dissected, and MSI experiments were performed on the dissected organs. Three ganglia of the nerve cord, with a dimension of 250–500 μm, were measured with 10-μm spatial resolution. High-quality m/z images, based on high spatial resolution and high mass accuracy were generated. These features helped to assign mass spectral peaks with high confidence. Mass accuracy of the imaging experiments was <3 ppm root mean square error, and mapping of different compound classes from a single experiment was possible. This approach improved the understanding of the biochemistry of P. riparius. Concentration differences and distributions of pederin and its analogues could be visualized in the whole-insect section. Without any labeling, we assigned key lipids for specific organs to describe their location in the body and to identify morphological structures with a specificity higher than with staining or immunohistology methods.

Silencing of the glycerophosphocholine phosphodiesterase GDPD5 alters the phospholipid metabolite profile in a breast cancer model in vivo as monitored by (31) P MRS

Abnormal choline phospholipid metabolism is an emerging hallmark of cancer, which is implicated in carcinogenesis and tumor progression. The malignant metabolic phenotype is characterized by high levels of phosphocholine (PC) and relatively low levels of glycerophosphocholine (GPC) in aggressive breast cancer cells. Phosphorus ((31) P) MRS is able to non-invasively detect these water-soluble metabolites of choline as well as ethanolamine phospholipid metabolism. Here we have investigated the effects of stably silencing glycerophosphoester diesterase domain containing 5 (GDPD5), which is an enzyme with glycerophosphocholine phosphodiesterase activity, in MDA-MB-231 breast cancer cells and orthotopic tumor xenografts. Tumors in which GDPD5 was stably silenced with GDPD5-specific shRNA contained increased levels of GPC and phosphoethanolamine (PE) compared with control tumors.

Interplay of choline metabolites and genes in patient-derived breast cancer xenografts

Introduction

Dysregulated choline metabolism is a well-known feature of breast cancer, but the underlying mechanisms are not fully understood. In this study, the metabolomic and transcriptomic characteristics of a large panel of human breast cancer xenograft models were mapped, with focus on choline metabolism.

Methods

Tumor specimens from 34 patient-derived xenograft models were collected and divided in two. One part was examined using high-resolution magic angle spinning (HR-MAS) MR spectroscopy while another part was analyzed using gene expression microarrays. Expression data of genes encoding proteins in the choline metabolism pathway were analyzed and correlated to the levels of choline (Cho), phosphocholine (PCho) and glycerophosphocholine (GPC) using Pearson’s correlation analysis. For comparison purposes, metabolic and gene expression data were collected from human breast tumors belonging to corresponding molecular subgroups.

Results

Most of the xenograft models were classified as basal-like (N = 19) or luminal B (N = 7). These two subgroups showed significantly different choline metabolic and gene expression profiles. The luminal B xenografts were characterized by a high PCho/GPC ratio while the basal-like xenografts were characterized by highly variable PCho/GPC ratio. Also, Cho, PCho and GPC levels were correlated to expression of several genes encoding proteins in the choline metabolism pathway, including choline kinase alpha (CHKA) and glycerophosphodiester phosphodiesterase domain containing 5 (GDPD5). These characteristics were similar to those found in human tumor samples.

Conclusion

The higher PCho/GPC ratio found in luminal B compared with most basal-like breast cancer xenograft models and human tissue samples do not correspond to results observed from in vitro studies. It is likely that microenvironmental factors play a role in the in vivo regulation of choline metabolism. Cho, PCho and GPC were correlated to different choline pathway-encoding genes in luminal B compared with basal-like xenografts, suggesting that regulation of choline metabolism may vary between different breast cancer subgroups. The concordance between the metabolic and gene expression profiles from xenograft models with breast cancer tissue samples from patients indicates that these xenografts are representative models of human breast cancer and represent relevant models to study tumor metabolism in vivo.

The emerging physiological roles of the glycerophosphodiesterase family

The glycerophosphodiester phosphodiesterases are evolutionarily conserved proteins that have been linked to several patho/physiological functions, comprising bacterial pathogenicity and mammalian cell proliferation or differentiation. The bacterial enzymes do not show preferential substrate selectivities among the glycerophosphodiesters, and they are mainly dedicated to glycerophosphodiester hydrolysis, producing glycerophosphate and alcohols as the building blocks that are required for bacterial biosynthetic pathways. In some cases, this enzymatic activity has been demonstrated to contribute to bacterial pathogenicity, such as with Hemophilus influenzae. Mammalian glyerophosphodiesterases have high substrate specificities, even if the number of potential physiological substrates is continuously increasing. Some of these mammalian enzymes have been directly linked to cell differentiation, such as GDE2, which triggers motor neuron differentiation, and GDE3, the enzymatic activity of which is necessary and sufficient to induce osteoblast differentiation. Instead, GDE5 has been shown to inhibit skeletal muscle development independent of its enzymatic activity.

Glycerophosphocholine utilization by Candida albicans: role of the Git3 transporter in virulence

Candida albicans contains four ORFs (GIT1,2,3,4) predicted to encode proteins involved in the transport of glycerophosphodiester metabolites. Previously, we reported that Git1, encoded by ORF 19.34, is responsible for the transport of intact glycerophosphoinositol but not glycerophosphocholine (GroPCho). Here, we report that a strain lacking both GIT3 (ORF 19.1979) and GIT4 (ORF 19.1980) is unable to transport [(3)H]GroPCho into the cell. In the absence of a GroPCho transporter, C. albicans can utilize GroPCho via a mechanism involving extracellular hydrolysis. Upon reintegration of either GIT3 or GIT4 into the genome, measurable uptake of [(3)H]GroPCho is observed. Transport assays and kinetic analyses indicate that Git3 has the greater transport velocity. We present evidence that GDE1 (ORF 19.3936) codes for an enzyme with glycerophosphodiesterase activity against GroPCho. Homozygous deletion of GDE1 results in a buildup of internal GroPCho that is restored to wild type levels by reintegration of GDE1 into the genome. The transcriptional regulator, Pho4, is shown to regulate the expression of GIT3, GIT4, and GDE1. Finally, Git3 is shown to be required for full virulence in a mouse model of disseminated candidiasis, and Git3 sequence orthologs are present in other pathogenic Candida species. In summary, we have characterized multiple aspects of GroPCho utilization by C. albicans and have demonstrated that GroPCho transport plays a key role in the growth of the organism in the host.