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A Elmihi K, Leonard KA, Nelson R, Thiesen A, Clugston RD, Jacobs RL. The emerging role of ethanolamine phosphate phospholyase in regulating hepatic phosphatidylethanolamine and plasma lipoprotein metabolism in mice. FASEB J 2024; 38:e70063. [PMID: 39312446 DOI: 10.1096/fj.202401321r] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2024] [Revised: 08/26/2024] [Accepted: 09/09/2024] [Indexed: 09/25/2024]
Abstract
Ethanolamine phosphate phospholyase (ETNPPL) is an enzyme that irreversibly degrades phospho-ethanolamine (p-ETN), an intermediate in the Kennedy pathway of phosphatidylethanolamine (PE) biosynthesis. PE is the second most abundant phospholipid in mammalian membranes. Disturbance of hepatic phospholipid homeostasis has been linked to the development of metabolic dysfunction-associated steatotic liver disease (MASLD). We generated whole-body Etnppl knockout mice to investigate the impact of genetic deletion of Etnppl on hepatic lipid metabolism. Primary hepatocytes isolated from Etnppl-/- mice showed increased conversion of [3H]ethanolamine to [3H]p-ETN and [3H]PE compared to Etnppl+/+ mice. Male and female Etnppl+/+ and Etnppl-/- mice were fed either a chow or a western-type diet (WTD). Irrespective of diet, Etnppl-/- mice had elevated fasting levels of total plasma cholesterol, triglyceride (TG) and apolipoprotein B100 (VLDL particles). Interestingly, hepatic TG secretion was unchanged between groups. Although hepatic lipids (phosphatidylcholine (PC), PE, TG, and cholesterol) were not different between mice, RNA sequencing analysis showed downregulation in genes related to cholesterol biosynthesis in Etnppl-/- mice. Furthermore, hepatic low-density lipoprotein receptor-related protein1 (LRP1) protein level was lower in female Etnppl-/- mice, which may indicate reduced uptake of remnant VLDL particles from circulation. Hepatic PE levels were only increased in WTD-fed female Etnppl-/- mice, not chow diet-fed mice. However, hepatic lipid accumulation and metabolic dysfunction-associated steatohepatitis (MASH) development were unchanged between Etnppl+/+ and Etnppl-/- mice. To conclude, ETNPPL has a role in regulating plasma lipoprotein metabolism independent of hepatic TG levels.
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Affiliation(s)
- Kholoud A Elmihi
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta, Canada
- Biochemistry Department, Faculty of Pharmacy, Mansoura University, Mansoura, Egypt
- Group on the Molecular and Cell Biology of Lipids, University of Alberta, Edmonton, Alberta, Canada
| | - Kelly-Ann Leonard
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta, Canada
- Group on the Molecular and Cell Biology of Lipids, University of Alberta, Edmonton, Alberta, Canada
| | - Randy Nelson
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta, Canada
- Group on the Molecular and Cell Biology of Lipids, University of Alberta, Edmonton, Alberta, Canada
| | - Aducio Thiesen
- Department of Laboratory Medicine and Pathology, University of Alberta, Edmonton, Alberta, Canada
| | - Robin D Clugston
- Group on the Molecular and Cell Biology of Lipids, University of Alberta, Edmonton, Alberta, Canada
- Department of Physiology, University of Alberta, Edmonton, Alberta, Canada
| | - René L Jacobs
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta, Canada
- Group on the Molecular and Cell Biology of Lipids, University of Alberta, Edmonton, Alberta, Canada
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Yang N, Zhang Y, Huang Y, Yan J, Qian Z, Li H, Luo P, Yang Z, Luo M, Wei X, Nie H, Ruan L, Hao Y, Gao S, Zheng K, Zhang C, Zhang L. FGF21 at physiological concentrations regulates vascular endothelial cell function through multiple pathways. Biochim Biophys Acta Mol Basis Dis 2022; 1868:166558. [PMID: 36174877 DOI: 10.1016/j.bbadis.2022.166558] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Revised: 09/05/2022] [Accepted: 09/20/2022] [Indexed: 11/26/2022]
Abstract
Cardiovascular diseases are closely associated with dysfunction of vascular endothelial cells (VECs), which can be influenced by various intrinsic and extrinsic factors, including fibroblast growth factor 21 (FGF21), but the effects of serum FGF21 on VECs remain unclear. We performed a cross-sectional study nested within a prospective cohort to assess the range of physiological concentrations of fasting serum FGF21 in 212 healthy individuals. We also treated human umbilical VECs (HUVECs) with recombinant FGF21 at different concentrations. The effects of FGF21 treatment on glycolysis, nitric oxide release and reduction of intracellular reactive oxygen species were assessed. The cells were also collected for RNA transcriptomic sequencing to investigate the potential mechanisms induced by FGF21 treatment. In addition, the roles of SIRT1 in the regulation of FGF21 were evaluated by SIRT1 knockdown. The results showed that the serum FGF21 concentration in healthy individuals ranged from 15.70 to 499.96 pg/mL and was positively correlated with age and pulse wave velocity. FGF21 at 400 pg/mL was sufficient to enhance glycolysis, increase nitric oxide release and protect cells from H2O2-induced oxidative damage. The upregulated genes after FGF21 treatment were mostly enriched in metabolic pathways, whereas the downregulated genes were mostly enriched in inflammation and apoptosis signaling pathways. Moreover, SIRT1 may be involved in the regulation of some genes by FGF21. In conclusion, our data indicate that FGF21 at a level within the physiological concentration range has a beneficial effect on HUVECs and that this effect may partly depend on the regulation of SIRT1.
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Affiliation(s)
- Ni Yang
- Department of Geriatrics, Institute of Gerontology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Yucong Zhang
- Department of Geriatrics, Institute of Gerontology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Yi Huang
- Department of Geriatrics, Institute of Gerontology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Jinhua Yan
- Department of Geriatrics, Institute of Gerontology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Zonghao Qian
- Department of Geriatrics, Institute of Gerontology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Han Li
- Department of Geriatrics, Institute of Gerontology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Pengcheng Luo
- Department of Geriatrics, Institute of Gerontology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Zhen Yang
- Department of Geriatrics, Institute of Gerontology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Mandi Luo
- Department of Geriatrics, Institute of Gerontology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Xiuxian Wei
- Department of Geriatrics, Institute of Gerontology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Hao Nie
- Department of Geriatrics, Institute of Gerontology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Lei Ruan
- Department of Geriatrics, Institute of Gerontology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Yi Hao
- Department of Geriatrics, Institute of Gerontology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China; Department of Pathogen Biology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Shangbang Gao
- Department of Geriatrics, Institute of Gerontology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China; College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Kai Zheng
- Department of Geriatrics, Institute of Gerontology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Cuntai Zhang
- Department of Geriatrics, Institute of Gerontology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
| | - Le Zhang
- Department of Geriatrics, Institute of Gerontology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
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Grapentine S, Singh RK, Basu P, Sivanesan S, Mattos G, Oresajo O, Cheema J, Demeke W, Dolinsky VW, Bakovic M. Pcyt2 deficiency causes age-dependant development of nonalcoholic steatohepatitis and insulin resistance that could be attenuated with phosphoethanolamine. Sci Rep 2022; 12:1048. [PMID: 35058529 PMCID: PMC8776951 DOI: 10.1038/s41598-022-05140-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Accepted: 01/06/2022] [Indexed: 12/19/2022] Open
Abstract
The mechanisms of NASH development in the context of age and genetics are not fully elucidated. This study investigates the age-dependent liver defects during NASH development in mice with heterozygous deletion of Pcyt2 (Pcyt2+/−), the rate limiting enzyme in phosphatidylethanolamine (PE) synthesis. Further, the therapeutic potential of Pcyt2 substrate, phosphoethanolamine (PEtn), is examined. Pcyt2+/− were investigated at 2 and 6–8 months (mo) of age and in addition, 6-mo old Pcyt2+/− with developed NASH were supplemented with PEtn for 8 weeks and glucose and fatty acid metabolism, insulin signaling, and inflammation were examined. Heterozygous ablation of Pcyt2 causes changes in liver metabolic regulators from young age, prior to the development of liver disease which does not occur until adulthood. Only older Pcyt2+/− experiences perturbed glucose and fatty acid metabolism. Older Pcyt2+/− liver develops NASH characterized by increased glucose production, accumulation of TAG and glycogen, and increased inflammation. Supplementation with PEtn reverses Pcyt2+/− steatosis, inflammation, and other aspects of NASH, showing that was directly caused by Pcyt2 deficiency. Pcyt2 deficiency is a novel mechanism of metabolic dysregulation due to reduced membrane ethanolamine phospholipid synthesis, and the metabolite PEtn offers therapeutic potential for NASH reversion.
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O’Dwyer C, Yaworski R, Katsumura S, Ghorbani P, Gobeil Odai K, Nunes JR, LeBlond ND, Sanjana S, Smith TT, Han S, Margison KD, Alain T, Morita M, Fullerton MD. Hepatic Choline Transport Is Inhibited During Fatty Acid-Induced Lipotoxicity and Obesity. Hepatol Commun 2020; 4:876-889. [PMID: 32490323 PMCID: PMC7262319 DOI: 10.1002/hep4.1516] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Revised: 02/25/2020] [Accepted: 03/11/2020] [Indexed: 01/11/2023] Open
Abstract
Choline is an essential nutrient and a critical component of the membrane phospholipid phosphatidylcholine (PC), the neurotransmitter acetylcholine, while also contributing to the methylation pathway. In the liver specifically, PC is the major membrane constituent and can be synthesized by the cytidine diphosphate-choline or the phosphatidylethanolamine N-methyltransferase pathway. With the continuing global rise in the rates of obesity and nonalcoholic fatty liver disease, we sought to explore how excess fatty acids on primary hepatocytes and diet-induced obesity affect choline uptake and metabolism. Our results demonstrate that hepatocytes chronically treated with palmitate, but not oleate or a mixture, had decreased choline uptake, which was associated with lower choline incorporation into PC and lower expression of choline transport proteins. Interestingly, a reduction in the rate of degradation spared PC levels in response to palmitate when compared with control. The effects of palmitate treatment were independent of endoplasmic reticulum stress, which counterintuitively augmented choline transport and transporter expression. In a model of obesity-induced hepatic steatosis, male mice fed a 60% high-fat diet for 10 weeks had significantly diminished hepatic choline uptake compared with lean mice fed a control diet. Although the transcript and protein expression of various choline metabolic enzymes fluctuated slightly, we observed reduced protein expression of choline transporter-like 1 (CTL1) in the liver of mice fed a high-fat diet. Polysome profile analyses revealed that in livers of obese mice, the CTL1 transcript, despite being more abundant, was translated to a lesser extent compared with lean controls. Finally, human liver cells demonstrated a similar response to palmitate treatment. Conclusion: Our results suggest that the altered fatty acid milieu seen in obesity-induced fatty liver disease progression may adversely affect choline metabolism, potentially through CTL1, but that compensatory mechanisms work to maintain phospholipid homeostasis.
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Affiliation(s)
- Conor O’Dwyer
- Department of Biochemistry, Microbiology and ImmunologyFaculty of MedicineUniversity of OttawaOttawaONCanada
- Centre for InfectionImmunity and Inflammation and Centre for Catalysis Research and InnovationUniversity of OttawaOttawaONCanada
| | - Rebecca Yaworski
- Department of Biochemistry, Microbiology and ImmunologyFaculty of MedicineUniversity of OttawaOttawaONCanada
- Centre for InfectionImmunity and Inflammation and Centre for Catalysis Research and InnovationUniversity of OttawaOttawaONCanada
| | - Sakie Katsumura
- Department of Molecular MedicineUniversity of Texas Health Science Center at San AntonioSan AntonioTX
| | - Peyman Ghorbani
- Department of Biochemistry, Microbiology and ImmunologyFaculty of MedicineUniversity of OttawaOttawaONCanada
- Centre for InfectionImmunity and Inflammation and Centre for Catalysis Research and InnovationUniversity of OttawaOttawaONCanada
| | - Kaelan Gobeil Odai
- Department of Biochemistry, Microbiology and ImmunologyFaculty of MedicineUniversity of OttawaOttawaONCanada
- Centre for InfectionImmunity and Inflammation and Centre for Catalysis Research and InnovationUniversity of OttawaOttawaONCanada
| | - Julia R.C. Nunes
- Department of Biochemistry, Microbiology and ImmunologyFaculty of MedicineUniversity of OttawaOttawaONCanada
- Centre for InfectionImmunity and Inflammation and Centre for Catalysis Research and InnovationUniversity of OttawaOttawaONCanada
| | - Nicholas D. LeBlond
- Department of Biochemistry, Microbiology and ImmunologyFaculty of MedicineUniversity of OttawaOttawaONCanada
- Centre for InfectionImmunity and Inflammation and Centre for Catalysis Research and InnovationUniversity of OttawaOttawaONCanada
| | - Sabrin Sanjana
- Department of Biochemistry, Microbiology and ImmunologyFaculty of MedicineUniversity of OttawaOttawaONCanada
- Centre for InfectionImmunity and Inflammation and Centre for Catalysis Research and InnovationUniversity of OttawaOttawaONCanada
| | - Tyler T.K. Smith
- Department of Biochemistry, Microbiology and ImmunologyFaculty of MedicineUniversity of OttawaOttawaONCanada
- Centre for InfectionImmunity and Inflammation and Centre for Catalysis Research and InnovationUniversity of OttawaOttawaONCanada
| | - Shauna Han
- Department of Biochemistry, Microbiology and ImmunologyFaculty of MedicineUniversity of OttawaOttawaONCanada
- Centre for InfectionImmunity and Inflammation and Centre for Catalysis Research and InnovationUniversity of OttawaOttawaONCanada
| | - Kaitlyn D. Margison
- Department of Biochemistry, Microbiology and ImmunologyFaculty of MedicineUniversity of OttawaOttawaONCanada
- Centre for InfectionImmunity and Inflammation and Centre for Catalysis Research and InnovationUniversity of OttawaOttawaONCanada
| | - Tommy Alain
- Department of Biochemistry, Microbiology and ImmunologyFaculty of MedicineUniversity of OttawaOttawaONCanada
- Centre for InfectionImmunity and Inflammation and Centre for Catalysis Research and InnovationUniversity of OttawaOttawaONCanada
- Children’s Hospital of Eastern Ontario Research InstituteOttawaONCanada
| | - Masahiro Morita
- Department of Molecular MedicineUniversity of Texas Health Science Center at San AntonioSan AntonioTX
- Barshop Institute for Longevity and Aging StudiesUniversity of Texas Health Science Center at San AntonioSan AntonioTX
- Institute of Resource Development and AnalysisKumamoto UniversityKumamotoJapan
| | - Morgan D. Fullerton
- Department of Biochemistry, Microbiology and ImmunologyFaculty of MedicineUniversity of OttawaOttawaONCanada
- Centre for InfectionImmunity and Inflammation and Centre for Catalysis Research and InnovationUniversity of OttawaOttawaONCanada
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Somerharju P, Virtanen JA, Hermansson M. Hypothesis: Chemical activity regulates and coordinates the processes maintaining glycerophospholipid homeostasis in mammalian cells. FASEB Bioadv 2020; 2:182-187. [PMID: 32161907 PMCID: PMC7059623 DOI: 10.1096/fba.2019-00058] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Revised: 07/19/2019] [Accepted: 12/31/2019] [Indexed: 02/06/2023] Open
Abstract
Mammalian cells maintain the complex glycerophospholipid (GPL) class compositions of their various membranes within close limits because this is essential to their well‐being or viability. Surprisingly, however, it is still not understood how those compositions are maintained except that GPL synthesis and degradation are closely coordinated. Here, we hypothesize that abrupt changes in the chemical activity of the individual GPL classes coordinate synthesis and degradation as well other the homeostatic processes. We have previously proposed that only a limited number of “allowed” or “optimal” GPL class compositions exist in cellular membranes because those compositions are energetically more favorable than others, that is, they represent local free energy minima (Somerharju et al 2009, Biochim. Biophys. Acta 1788, 12‐23). This model, however, could not satisfactorily explain how the “optimal” compositions are sensed by the key homeostatic enzymes, that is, rate‐limiting synthetizing enzymes and homeostatic phospholipases. We now hypothesize that when the mole fraction of a GPL class exceeds an optimal value, its chemical activity abruptly increases which (a) increases its propensity to efflux from the membrane thus making it susceptible for hydrolysis by homeostatic phospholipases; (b) increases its potency to inhibit its own biosynthesis via a feedback mechanism; (c) enhances its conversion to another glycerophospholipid class via a novel process termed “head group remodeling” or (d) enhances its translocation to other subcellular membranes. In summary, abrupt change in the chemical activity of the individual GPL classes is proposed to regulate and coordinate those four processes maintaining GPL class homeostasis in mammalian cells.
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Affiliation(s)
| | - Jorma A Virtanen
- Medicum Faculty of Medicine University of Helsinki Helsinki Finland
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Ando H, Horibata Y, Aoyama C, Shimizu H, Shinohara Y, Yamashita S, Sugimoto H. Side-chain oxysterols suppress the transcription of CTP: Phosphoethanolamine cytidylyltransferase and 3-hydroxy-3-methylglutaryl-CoA reductase by inhibiting the interaction of p300 and NF-Y, and H3K27 acetylation. J Steroid Biochem Mol Biol 2019; 195:105482. [PMID: 31580889 DOI: 10.1016/j.jsbmb.2019.105482] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Revised: 09/10/2019] [Accepted: 09/18/2019] [Indexed: 10/25/2022]
Abstract
CTP: phosphoethanolamine cytidylyltransferase (Pcyt2) is the rate-limiting enzyme in mammalian phosphatidylethanolamine (PE) biosynthesis. Previously, we reported that increasedPcyt2 mRNA levels after serum starvation are suppressed by 25-hydroxycholesterol (HC) (25-HC), and that nuclear factor-Y (NF-Y) is involved in the inhibitory effects. Transcription of Hmgcr, which encodes 3-hydroxy-3-methylglutaryl-CoA reductase, is suppressed in the same manner. However, no typical sterol regulatory element (SRE) was detected in the Pcyt2 promoter. We were therefore interested in the effect of 25-HC on the modification of histones and thus treated cells with histone acetyltransferase inhibitor (anacardic acid) or histone deacetylase inhibitor (trichostatin A). The suppressive effect of 25-HC on Pcyt2 and Hmgcr mRNA transcription was ameliorated by trichostatin A. Anacardic acid, 25-HC and 24(S)-HC suppressed their transcription by inhibiting H3K27 acetylation in their promoters as evaluated by chromatin immunoprecipitation (ChIP) assays. 27-HC, 22(S)-HC and 22(R)-HC also suppressed their transcription, but 7α-HC, 7β-HC, the synthetic LXR agonist T0901317 and cholesterol did not. Furthermore, 25-HC inhibited p300 recruitment to the Pcyt2 and Hmgcr promoters, and suppressed H3K27 acetylation. 25-HC in the medium was easily conducted into cells. Based on these results, we concluded that 25-HC (and other side-chain oxysterols) in the medium was easily transferred into cells, suppressed H3K27 acetylation via p300 recruitment on the NF-Y complex in the Pcyt2 and Hmgcr promoters, and then suppressed transcription of these genes although LXR is not involved.
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Affiliation(s)
- Hiromi Ando
- Department of Biochemistry, Dokkyo Medical University School of Medicine, Mibu 321-0293, Japan
| | - Yasuhiro Horibata
- Department of Biochemistry, Dokkyo Medical University School of Medicine, Mibu 321-0293, Japan
| | - Chieko Aoyama
- Department of Biochemistry, Dokkyo Medical University School of Medicine, Mibu 321-0293, Japan
| | - Hiroaki Shimizu
- Department of Biochemistry, Dokkyo Medical University School of Medicine, Mibu 321-0293, Japan
| | - Yasutake Shinohara
- Department of Biochemistry, Dokkyo Medical University School of Medicine, Mibu 321-0293, Japan
| | - Satoko Yamashita
- Department of Biochemistry, Dokkyo Medical University School of Medicine, Mibu 321-0293, Japan
| | - Hiroyuki Sugimoto
- Department of Biochemistry, Dokkyo Medical University School of Medicine, Mibu 321-0293, Japan.
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7
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Vance JE. Historical perspective: phosphatidylserine and phosphatidylethanolamine from the 1800s to the present. J Lipid Res 2018; 59:923-944. [PMID: 29661786 DOI: 10.1194/jlr.r084004] [Citation(s) in RCA: 57] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Revised: 04/12/2018] [Indexed: 12/17/2022] Open
Abstract
This article provides a historical account of the discovery, chemistry, and biochemistry of two ubiquitous phosphoglycerolipids, phosphatidylserine (PS) and phosphatidylethanolamine (PE), including the ether lipids. In addition, the article describes the biosynthetic pathways for these phospholipids and how these pathways were elucidated. Several unique functions of PS and PE in mammalian cells in addition to their ability to define physical properties of membranes are discussed. For example, the translocation of PS from the inner to the outer leaflet of the plasma membrane of cells occurs during apoptosis and during some other specific physiological processes, and this translocation is responsible for profound life-or-death events. Moreover, mitochondrial function is severely impaired when the PE content of mitochondria is reduced below a threshold level. The discovery and implications of the existence of membrane contact sites between the endoplasmic reticulum and mitochondria and their relevance for PS and PE metabolism, as well as for mitochondrial function, are also discussed. Many of the recent advances in these fields are due to the use of isotope labeling for tracing biochemical pathways. In addition, techniques for disruption of specific genes in mice are now widely used and have provided major breakthroughs in understanding the roles and metabolism of PS and PE in vivo.
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Affiliation(s)
- Jean E Vance
- Department of Medicine and Group on the Molecular and Cell Biology of Lipids, University of Alberta, Edmonton, Alberta T6G 2S2, Canada.
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8
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Singh RK, Lui E, Wright D, Taylor A, Bakovic M. Alcohol extract of North American ginseng (Panax quinquefolius) reduces fatty liver, dyslipidemia, and other complications of metabolic syndrome in a mouse model. Can J Physiol Pharmacol 2017; 95:1046-1057. [PMID: 28666094 DOI: 10.1139/cjpp-2016-0510] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
We investigated whether North American ginseng (Panax quinquefolius) could reduce development of the metabolic syndrome phenotype in a mouse model (ETKO) of the disease. Young ETKO mice have no disease but similar to humans start to develop the fatty liver, hypertriglyceridemia, obesity, and insulin resistance at 25-30 weeks of age, and the disease continues to progress with ageing. ETKO mice were orally given an ethanol extract of ginseng roots at 4 and 32 weeks of age. Treatments with ginseng eliminated the ETKO fatty liver, reduced hepatic and intestinal lipoprotein secretion, and reduced the level of circulating lipids. Improvements by ginseng treatments were manifested as a reduction in the expression of genes involved in the regulation of fatty acid and triglyceride (fat) synthesis and secretion by the lipoproteins on one hand, and the stimulation of fatty acid oxidation and triglyceride degradation by lipolysis on the other hand. These processes altogether improved glucose, fatty acid, and triglyceride metabolism, reduced liver fat load, and reversed the progression of metabolic syndrome. These data confirm that treatments with North American ginseng could alleviate metabolic syndrome through the maintenance of a better balance between glucose and fatty acid metabolism, lipoprotein secretion, and energy homeostasis in disease-prone states.
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Affiliation(s)
- Ratnesh K Singh
- a Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Edmund Lui
- b Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, ON N6A 5C1, Canada
| | - David Wright
- a Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Adrian Taylor
- a Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Marica Bakovic
- a Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada
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9
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Schenkel LC, Sivanesan S, Zhang J, Wuyts B, Taylor A, Verbrugghe A, Bakovic M. Choline supplementation restores substrate balance and alleviates complications of Pcyt2 deficiency. J Nutr Biochem 2015; 26:1221-34. [PMID: 26242921 DOI: 10.1016/j.jnutbio.2015.05.014] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Revised: 05/24/2015] [Accepted: 05/27/2015] [Indexed: 02/07/2023]
Abstract
Choline plays a critical role in systemic lipid metabolism and hepatic function. Here we conducted a series of experiments to investigate the effect of choline supplementation on metabolically altered Pcyt2(+/-) mice. In Pcyt2(+/-) mice, the membrane phosphatidylethanolamine (PE) turnover is reduced and the formation of fatty acids (FA) and triglycerides (TAG) increased, resulting in hypertriglyceridemia, liver steatosis and obesity. One month of choline supplementation reduced the incorporation of FA into TAG and facilitated TAG degradation in Pcyt2(+/-) adipocytes, plasma and liver. Choline particularly stimulated adipocyte and liver TAG lipolysis by specific lipases (ATGL, LPL and HSL) and inhibited TAG formation by DGAT1 and DGAT2. Choline also activated the liver AMPK and mitochondrial FA oxidation gene PPARα and reduced the FA synthesis genes SREBP1, SCD1 and FAS. Liver (HPLC) and plasma (tandem mass spectroscopy and (1)H-NMR) metabolite profiling established that Pcyt2(+/-) mice have reduced membrane cholesterol/sphingomyelin ratio and the homocysteine/methionine cycle that were improved by choline supplementation. These data suggest that supplementary choline is beneficial for restoring FA and TAG homeostasis under conditions of obesity caused by impaired PE synthesis.
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Affiliation(s)
- Laila C Schenkel
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, ON, Canada N1G 2W1
| | - Sugashan Sivanesan
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, ON, Canada N1G 2W1
| | - Junzeng Zhang
- Aquatic and Crop Resource Development, National Research Council Canada, Halifax, NS, Canada B3H 3Z1
| | - Birgitte Wuyts
- Department of Clinical Chemistry, Laboratory of Metabolic Disorders, University Hospital Ghent, 9000 Ghent, Belgium
| | - Adrian Taylor
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, ON, Canada N1G 2W1
| | - Adronie Verbrugghe
- University of Guelph, Ontario Veterinary College, Dep. Clinical Studies, Guelph, Canada
| | - Marica Bakovic
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, ON, Canada N1G 2W1.
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Pereira TJ, Fonseca MA, Campbell KE, Moyce BL, Cole LK, Hatch GM, Doucette CA, Klein J, Aliani M, Dolinsky VW. Maternal obesity characterized by gestational diabetes increases the susceptibility of rat offspring to hepatic steatosis via a disrupted liver metabolome. J Physiol 2015; 593:3181-97. [PMID: 25922055 DOI: 10.1113/jp270429] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2015] [Accepted: 04/17/2015] [Indexed: 12/16/2022] Open
Abstract
Maternal obesity is associated with a high risk for gestational diabetes mellitus (GDM), which is a common complication of pregnancy. The influence of maternal obesity and GDM on the metabolic health of the offspring is poorly understood. We hypothesize that GDM associated with maternal obesity will cause obesity, insulin resistance and hepatic steatosis in the offspring. Female Sprague-Dawley rats were fed a high-fat (45%) and sucrose (HFS) diet to cause maternal obesity and GDM. Lean control pregnant rats received low-fat (LF; 10%) diets. To investigate the interaction between the prenatal environment and postnatal diets, rat offspring were assigned to LF or HFS diets for 12 weeks, and insulin sensitivity and hepatic steatosis were evaluated. Pregnant GDM dams exhibited excessive gestational weight gain, hyperinsulinaemia and hyperglycaemia. Offspring of GDM dams gained more weight than the offspring of lean dams due to excess adiposity. The offspring of GDM dams also developed hepatic steatosis and insulin resistance. The postnatal consumption of a LF diet did not protect offspring of GDM dams against these metabolic disorders. Analysis of the hepatic metabolome revealed increased diacylglycerol and reduced phosphatidylethanolamine in the offspring of GDM dams compared to offspring of lean dams. Consistent with altered lipid metabolism, the expression of CTP:phosphoethanolamine cytidylyltransferase, and peroxisomal proliferator activated receptor-α mRNA was reduced in the livers of GDM offspring. GDM exposure programs gene expression and hepatic metabolite levels and drives the development of hepatic steatosis and insulin resistance in young adult rat offspring.
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Affiliation(s)
- Troy J Pereira
- Department of Pharmacology & Therapeutics.,Diabetes Research Envisioned and Accomplished in Manitoba (DREAM) Research Theme.,Children's Hospital Research Institute of Manitoba
| | - Mario A Fonseca
- Department of Pharmacology & Therapeutics.,Diabetes Research Envisioned and Accomplished in Manitoba (DREAM) Research Theme.,Children's Hospital Research Institute of Manitoba
| | - Kristyn E Campbell
- Department of Pharmacology & Therapeutics.,Diabetes Research Envisioned and Accomplished in Manitoba (DREAM) Research Theme.,Children's Hospital Research Institute of Manitoba
| | - Brittany L Moyce
- Department of Pharmacology & Therapeutics.,Diabetes Research Envisioned and Accomplished in Manitoba (DREAM) Research Theme.,Children's Hospital Research Institute of Manitoba
| | - Laura K Cole
- Department of Pharmacology & Therapeutics.,Diabetes Research Envisioned and Accomplished in Manitoba (DREAM) Research Theme.,Children's Hospital Research Institute of Manitoba
| | - Grant M Hatch
- Department of Pharmacology & Therapeutics.,Diabetes Research Envisioned and Accomplished in Manitoba (DREAM) Research Theme.,Children's Hospital Research Institute of Manitoba
| | - Christine A Doucette
- Diabetes Research Envisioned and Accomplished in Manitoba (DREAM) Research Theme.,Children's Hospital Research Institute of Manitoba.,Department of Physiology and Pathophysiology
| | | | - Michel Aliani
- Department of Human Nutrition, University of Manitoba, Winnipeg, MB, Canada
| | - Vernon W Dolinsky
- Department of Pharmacology & Therapeutics.,Diabetes Research Envisioned and Accomplished in Manitoba (DREAM) Research Theme.,Children's Hospital Research Institute of Manitoba
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11
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Pavlovic Z, Zhu L, Pereira L, Singh RK, Cornell RB, Bakovic M. Isoform-specific and protein kinase C-mediated regulation of CTP:phosphoethanolamine cytidylyltransferase phosphorylation. J Biol Chem 2014; 289:9053-64. [PMID: 24519946 DOI: 10.1074/jbc.m113.544932] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
CTP:phosphoethanolamine cytidylyltransferase (Pcyt2) is the main regulatory enzyme for de novo biosynthesis of phosphatidylethanolamine by the CDP-ethanolamine pathway. There are two isoforms of Pcyt2, -α and -β; however, very little is known about their specific roles in this important metabolic pathway. We previously demonstrated increased phosphatidylethanolamine biosynthesis subsequent to elevated activity and phosphorylation of Pcyt2α and -β in MCF-7 breast cancer cells grown under conditions of serum deficiency. Mass spectroscopy analyses of Pcyt2 provided evidence for isoform-specific as well as shared phosphorylations. Pcyt2β was specifically phosphorylated at the end of the first cytidylyltransferase domain. Pcyt2α was phosphorylated within the α-specific motif that is spliced out in Pcyt2β and on two PKC consensus serine residues, Ser-215 and Ser-223. Single and double mutations of PKC consensus sites reduced Pcyt2α phosphorylation, activity, and phosphatidylethanolamine synthesis by 50-90%. The phosphorylation and activity of endogenous Pcyt2 were dramatically increased with phorbol esters and reduced by specific PKC inhibitors. In vitro translated Pcyt2α was phosphorylated by PKCα, PKCβI, and PKCβII. Pcyt2α Ser-215 was also directly phosphorylated with PKCα. Mapping of the Pcyt2α- and -β-phosphorylated sites to the solved structure of a human Pcyt2β showed that they clustered within and flanking the central linker region that connects the two catalytic domains and is a novel regulatory segment not present in other cytidylyltransferases. This study is the first to demonstrate differences in phosphorylation between Pcyt2 isoforms and to uncover the role of the PKC-regulated phosphorylation.
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Affiliation(s)
- Zvezdan Pavlovic
- From the Department of Human Health and Nutritional Sciences, University of Guelph, Ontario N1G 2W1 and
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12
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Regulation of Phosphatidylethanolamine Homeostasis—The Critical Role of CTP:Phosphoethanolamine Cytidylyltransferase (Pcyt2). Int J Mol Sci 2013; 14:2529-50. [PMID: 23354482 PMCID: PMC3588000 DOI: 10.3390/ijms14022529] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Revised: 01/02/2013] [Accepted: 01/17/2013] [Indexed: 12/21/2022] Open
Abstract
Phosphatidylethanolamine (PE) is the most abundant lipid on the protoplasmatic leaflet of cellular membranes. It has a pivotal role in cellular processes such as membrane fusion, cell cycle regulation, autophagy, and apoptosis. CTP:phosphoethanolamine cytidylyltransferase (Pcyt2) is the main regulatory enzyme in de novo biosynthesis of PE from ethanolamine and diacylglycerol by the CDP-ethanolamine Kennedy pathway. The following is a summary of the current state of knowledge on Pcyt2 and how splicing and isoform specific differences could lead to variations in functional properties in this family of enzymes. Results from the most recent studies on Pcyt2 transcriptional regulation, promoter function, autophagy, and cell growth regulation are highlighted. Recent data obtained from Pcyt2 knockout mouse models is also presented, demonstrating the essentiality of this gene in embryonic development as well as the major physiological consequences of deletion of one Pcyt2 allele. Those include development of symptoms of the metabolic syndrome such as elevated lipogenesis and lipoprotein secretion, hypertriglyceridemia, liver steatosis, obesity, and insulin resistance. The objective of this review is to elucidate the nature of Pcyt2 regulation by linking its catalytic function with the regulation of lipid and energy homeostasis.
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13
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Basseri S, Lhoták Š, Fullerton MD, Palanivel R, Jiang H, Lynn EG, Ford RJ, Maclean KN, Steinberg GR, Austin RC. Loss of TDAG51 results in mature-onset obesity, hepatic steatosis, and insulin resistance by regulating lipogenesis. Diabetes 2013; 62:158-69. [PMID: 22961087 PMCID: PMC3526025 DOI: 10.2337/db12-0256] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Regulation of energy metabolism is critical for the prevention of obesity, diabetes, and hepatic steatosis. Here, we report an important role for the pleckstrin homology-related domain family member, T-cell death-associated gene 51 (TDAG51), in the regulation of energy metabolism. TDAG51 expression was examined during adipocyte differentiation. Adipogenic potential of preadipocytes with knockdown or absence of TDAG51 was assessed. Weight gain, insulin sensitivity, metabolic rate, and liver lipid content were also compared between TDAG51-deficient (TDAG51(-/-)) and wild-type mice. In addition to its relatively high expression in liver, TDAG51 was also present in white adipose tissue (WAT). TDAG51 was downregulated during adipogenesis, and TDAG51(-/-) preadipocytes exhibited greater lipogenic potential. TDAG51(-/-) mice fed a chow diet exhibited greater body and WAT mass, had reduced energy expenditure, displayed mature-onset insulin resistance (IR), and were predisposed to hepatic steatosis. TDAG51(-/-) mice had increased hepatic triglycerides and SREBP-1 target gene expression. Furthermore, TDAG51 expression was inversely correlated with fatty liver in multiple mouse models of hepatic steatosis. Taken together, our findings suggest that TDAG51 is involved in energy homeostasis at least in part by regulating lipogenesis in liver and WAT, and hence, may constitute a novel therapeutic target for the treatment of obesity and IR.
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Affiliation(s)
- Sana Basseri
- Division of Nephrology, Department of Medicine, McMaster University, Hamilton, Ontario, Canada
- Hamilton Centre for Kidney Research, St. Joseph’s Healthcare Hamilton, Hamilton, Ontario, Canada
| | - Šárka Lhoták
- Hamilton Centre for Kidney Research, St. Joseph’s Healthcare Hamilton, Hamilton, Ontario, Canada
| | - Morgan D. Fullerton
- Division of Endocrinology and Metabolism, Department of Medicine, McMaster University, Hamilton, Ontario, Canada
| | - Rengasamy Palanivel
- Division of Endocrinology and Metabolism, Department of Medicine, McMaster University, Hamilton, Ontario, Canada
| | - Hua Jiang
- Department of Pediatrics, University of Colorado School of Medicine, Aurora, Colorado
| | - Edward G. Lynn
- Division of Nephrology, Department of Medicine, McMaster University, Hamilton, Ontario, Canada
- Hamilton Centre for Kidney Research, St. Joseph’s Healthcare Hamilton, Hamilton, Ontario, Canada
| | - Rebecca J. Ford
- Division of Endocrinology and Metabolism, Department of Medicine, McMaster University, Hamilton, Ontario, Canada
| | - Kenneth N. Maclean
- Department of Pediatrics, University of Colorado School of Medicine, Aurora, Colorado
| | - Gregory R. Steinberg
- Division of Endocrinology and Metabolism, Department of Medicine, McMaster University, Hamilton, Ontario, Canada
| | - Richard C. Austin
- Division of Nephrology, Department of Medicine, McMaster University, Hamilton, Ontario, Canada
- Hamilton Centre for Kidney Research, St. Joseph’s Healthcare Hamilton, Hamilton, Ontario, Canada
- Corresponding author: Richard C. Austin,
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14
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Singh RK, Fullerton MD, Vine D, Bakovic M. Mechanism of hypertriglyceridemia in CTP:phosphoethanolamine cytidylyltransferase-deficient mice. J Lipid Res 2012; 53:1811-22. [PMID: 22764088 DOI: 10.1194/jlr.m021881] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Phosphatidylethanolamine is an important inner-leaflet phospholipid, and CTP:phosphoethanolamine cytidylyltransferase-Pcyt2 acts as the main regulator of the de novo phosphatidylethanolamine synthesis from ethanolamine and diacylglycerol. Complete deletion of the mouse Pcyt2 gene is embryonic lethal, and the single-allele deficiency leads to development of the metabolic syndrome phenotype, including liver steatosis, hypertriglyceridemia, obesity, and insulin resistance. This study aimed to specifically elucidate the mechanisms of hypertriglyceridemia in Pcyt2 heterozygous mice (Pcyt2(+/-)). Evidence here shows that unlike 8 week-old mice, 32 week- and 42 week-old Pcyt2(+/-) mice experience increased VLDL secretion and liver microsomal triglyceride transfer protein activity. Older Pcyt2(+/-) mice also demonstrate increased levels of postprandial plasma TAGs, increased stimulation of genes responsible for intestinal lipid absorption, transport and chylomicron secretion, and dramatically elevated plasma Angptl4, apoB-100, and apoB-48 content. In addition, plasma HL and LPL activities and TAG clearance following a lipid challenge were significantly reduced in Pcyt2(+/-) mice relative to control littermates. Collectively, these results establish that the hypertriglyceridemia that accompanies Pcyt2 deficiency is the result of multiple metabolic adaptations, including elevated hepatic and intestinal lipoprotein secretion and stimulated expression and/or activity of genes involved in lipid absorption and transport and lipoprotein assembly, together with reduced plasma TAG clearance and utilization with peripheral tissues.
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Affiliation(s)
- Ratnesh Kumar Singh
- Department of Human Health & Nutritional Sciences, University of Guelph, Guelph, Ontario N1G2W1, Canada
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15
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Zhu L, Bakovic M. Breast cancer cells adapt to metabolic stress by increasing ethanolamine phospholipid synthesis and CTP:ethanolaminephosphate cytidylyltransferase-Pcyt2 activity. Biochem Cell Biol 2012; 90:188-99. [PMID: 22339418 DOI: 10.1139/o11-081] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The significance of phosphatidylethanolamine (PE) in breast cancer cell metabolism was investigated under stress conditions caused by serum deficiency. Serum deficient MCF-7 cells adapt to stress conditions by increasing synthesis and content of PE and diacylglycerol (DAG). The biosynthesis of PE from DAG and ethanolamine was regulated at the level of formation of CDP-ethanolamine, the metabolic step catalyzed by Pcyt2. The catalytic activity of Pcyt2 was elevated 2-3-fold, yet the enzyme remained rate-limiting in serum-deficient cells. Contributions to the elevated Pcyt2 activity included transcriptional and translational components. The mRNA levels of two splice variants, Pcyt2α and Pcyt2β, were 1.5-3-fold higher in deficient cells. The total amounts of Pcyt2 and Pcyt2α proteins were similarly elevated 1.5-2.5-fold. In vivo [γ(32)Pi] radiolabeling revealed that Pcyt2 was additionally regulated by phosphorylation. Under unfavorable metabolic conditions, both endogenous and His/Myc-tagged Pcyt2 were increasingly phosphorylated at Ser residues. The results established that elevated DAG formation and the increased activity of the rate-regulatory enzyme Pcyt2 were critical modulators of the PE Kennedy pathway, and total PE content in serum deprived breast cancer cells. Therefore, as an essential gene sensitive to nutritional microenvironment, Pcyt2 could represent a legitimate target in novel metabolic strategies for cancer.
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Affiliation(s)
- Lin Zhu
- Department of Human Health and Nutritional Sciences, University of Guelph, ON N1G 2W1, Canada
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16
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Hermansson M, Hokynar K, Somerharju P. Mechanisms of glycerophospholipid homeostasis in mammalian cells. Prog Lipid Res 2011; 50:240-57. [DOI: 10.1016/j.plipres.2011.02.004] [Citation(s) in RCA: 129] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2011] [Revised: 02/21/2011] [Accepted: 02/25/2011] [Indexed: 01/09/2023]
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