1
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Eshima H, Johnson JM, Funai K. Lipid peroxidation does not mediate muscle atrophy induced by PSD deficiency. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.22.573082. [PMID: 38187526 PMCID: PMC10769360 DOI: 10.1101/2023.12.22.573082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2024]
Abstract
Mechanisms by which disuse promotes skeletal muscle atrophy is not well understood. We previously demonstrated that disuse reduces the abundance of mitochondrial phosphatidylethanolamine (PE) in skeletal muscle. Deletion of phosphatidylserine decarboxylase (PSD), an enzyme that generates mitochondrial PE, was sufficient to promote muscle atrophy. In this study, we tested the hypothesis that muscle atrophy induced by PSD deletion is driven by an accumulation of lipid hydroperoxides (LOOH). Mice with muscle-specific knockout of PSD (PSD-MKO) were crossed with glutathione peroxidase 4 (GPx4) transgenic mice (GPx4Tg) to suppress the accumulation of LOOH. However, PSD-MKO × GPx4Tg mice and PSD-MKO mice demonstrated equally robust loss of muscle mass. These results suggest that muscle atrophy induced by PSD deficiency is not driven by the accumulation of LOOH.
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Affiliation(s)
- Hiroaki Eshima
- Diabetes & Metabolism Research Center, University of Utah
- Department of Nutrition & Integrative Physiology, University of Utah
- Department of International Tourism, Nagasaki International University
| | - Jordan M. Johnson
- Diabetes & Metabolism Research Center, University of Utah
- Department of Nutrition & Integrative Physiology, University of Utah
| | - Katsuhiko Funai
- Diabetes & Metabolism Research Center, University of Utah
- Department of Nutrition & Integrative Physiology, University of Utah
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2
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Kimura T, Kimura AK, Epand RM. Systematic crosstalk in plasmalogen and diacyl lipid biosynthesis for their differential yet concerted molecular functions in the cell. Prog Lipid Res 2023; 91:101234. [PMID: 37169310 DOI: 10.1016/j.plipres.2023.101234] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Revised: 04/29/2023] [Accepted: 05/05/2023] [Indexed: 05/13/2023]
Abstract
Plasmalogen is a major phospholipid of mammalian cell membranes. Recently it is becoming evident that the sn-1 vinyl-ether linkage in plasmalogen, contrasting to the ester linkage in the counterpart diacyl glycerophospholipid, yields differential molecular characteristics for these lipids especially related to hydrocarbon-chain order, so as to concertedly regulate biological membrane processes. A role played by NMR in gaining information in this respect, ranging from molecular to tissue levels, draws particular attention. We note here that a broad range of enzymes in de novo synthesis pathway of plasmalogen commonly constitute that of diacyl glycerophospholipid. This fact forms the basis for systematic crosstalk that not only controls a quantitative balance between these lipids, but also senses a defect causing loss of lipid in either pathway for compensation by increase of the counterpart lipid. However, this inherent counterbalancing mechanism paradoxically amplifies imbalance in differential effects of these lipids in a diseased state on membrane processes. While sharing of enzymes has been recognized, it is now possible to overview the crosstalk with growing information for specific enzymes involved. The overview provides a fundamental clue to consider cell and tissue type-dependent schemes in regulating membrane processes by plasmalogen and diacyl glycerophospholipid in health and disease.
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Affiliation(s)
- Tomohiro Kimura
- Department of Chemistry & Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas 66506, USA.
| | - Atsuko K Kimura
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario L8S 4K1, Canada
| | - Richard M Epand
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario L8S 4K1, Canada
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3
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Phan K, He Y, Bhatia S, Pickford R, McDonald G, Mazumder S, Timmins HC, Hodges JR, Piguet O, Dzamko N, Halliday GM, Kiernan MC, Kim WS. Multiple pathways of lipid dysregulation in amyotrophic lateral sclerosis. Brain Commun 2022; 5:fcac340. [PMID: 36632187 PMCID: PMC9825811 DOI: 10.1093/braincomms/fcac340] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Revised: 11/02/2022] [Accepted: 12/12/2022] [Indexed: 12/27/2022] Open
Abstract
Amyotrophic lateral sclerosis is a rapidly progressing neurodegenerative disease characterized by the degeneration of motor neurons and loss of various muscular functions. Dyslipidaemia is prevalent in amyotrophic lateral sclerosis with aberrant changes mainly in cholesterol ester and triglyceride. Despite this, little is known about global lipid changes in amyotrophic lateral sclerosis or in relation to disease progression. The present study incorporated a longitudinal lipidomic analysis of amyotrophic lateral sclerosis serum with a comparison with healthy controls using advanced liquid chromatography-mass spectrometry. The results established that diglyceride, the precursor of triglyceride, was enriched the most, while ceramide was depleted the most in amyotrophic lateral sclerosis compared with controls, with the diglyceride species (18:1/18:1) correlating significantly to neurofilament light levels. The prenol lipid CoQ8 was also decreased in amyotrophic lateral sclerosis and correlated to neurofilament light levels. Most interestingly, the phospholipid phosphatidylethanolamine and its three derivatives decreased with disease progression, in contrast to changes with normal ageing. Unsaturated lipids that are prone to lipid peroxidation were elevated with disease progression with increases in the formation of toxic lipid products. Furthermore, in vitro studies revealed that phosphatidylethanolamine synthesis modulated TARDBP expression in SH-SY5Y neuronal cells. Finally, diglyceride, cholesterol ester and ceramide were identified as potential lipid biomarkers for amyotrophic lateral sclerosis diagnosis and monitoring disease progression. In summary, this study represents a longitudinal lipidomics analysis of amyotrophic lateral sclerosis serum and has provided new insights into multiple pathways of lipid dysregulation in amyotrophic lateral sclerosis.
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Affiliation(s)
| | | | | | - Russell Pickford
- Bioanalytical Mass Spectrometry Facility, University of New South Wales, Sydney, NSW, Australia
| | - Gordon McDonald
- The University of Sydney, Sydney Informatics Hub, Sydney, NSW, Australia
| | - Srestha Mazumder
- The University of Sydney, Brain and Mind Centre, Sydney, NSW, Australia
| | - Hannah C Timmins
- The University of Sydney, Brain and Mind Centre, Sydney, NSW, Australia
| | - John R Hodges
- The University of Sydney, Brain and Mind Centre, Sydney, NSW, Australia
| | - Olivier Piguet
- The University of Sydney, Brain and Mind Centre, Sydney, NSW, Australia,The University of Sydney, School of Psychology, Sydney, NSW, Australia
| | - Nicolas Dzamko
- The University of Sydney, Brain and Mind Centre, Sydney, NSW, Australia,The University of Sydney, School of Medical Sciences, Sydney, NSW, Australia
| | - Glenda M Halliday
- The University of Sydney, Brain and Mind Centre, Sydney, NSW, Australia,The University of Sydney, School of Medical Sciences, Sydney, NSW, Australia
| | - Matthew C Kiernan
- The University of Sydney, Brain and Mind Centre, Sydney, NSW, Australia,Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Sydney, NSW, Australia
| | - Woojin Scott Kim
- Correspondence to: W. S. Kim, Associate Professor Brain and Mind Centre, The University of Sydney Camperdown NSW 2050, Australia E-mail:
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4
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Morita SY, Ikeda Y. Regulation of membrane phospholipid biosynthesis in mammalian cells. Biochem Pharmacol 2022; 206:115296. [DOI: 10.1016/j.bcp.2022.115296] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Revised: 10/05/2022] [Accepted: 10/05/2022] [Indexed: 11/02/2022]
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5
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Fat of the Gut: Epithelial Phospholipids in Inflammatory Bowel Diseases. Int J Mol Sci 2021; 22:ijms222111682. [PMID: 34769112 PMCID: PMC8584226 DOI: 10.3390/ijms222111682] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Revised: 10/20/2021] [Accepted: 10/27/2021] [Indexed: 12/15/2022] Open
Abstract
Inflammatory bowel diseases (IBD) comprise a distinct set of clinical symptoms resulting from chronic inflammation within the gastrointestinal (GI) tract. Despite the significant progress in understanding the etiology and development of treatment strategies, IBD remain incurable for thousands of patients. Metabolic deregulation is indicative of IBD, including substantial shifts in lipid metabolism. Recent data showed that changes in some phospholipids are very common in IBD patients. For instance, phosphatidylcholine (PC)/phosphatidylethanolamine (PE) and lysophosphatidylcholine (LPC)/PC ratios are associated with the severity of the inflammatory process. Composition of phospholipids also changes upon IBD towards an increase in arachidonic acid and a decrease in linoleic and a-linolenic acid levels. Moreover, an increase in certain phospholipid metabolites, such as lysophosphatidylcholine, sphingosine-1-phosphate and ceramide, can result in enhanced intestinal inflammation, malignancy, apoptosis or necroptosis. Because some phospholipids are associated with pathogenesis of IBD, they may provide a basis for new strategies to treat IBD. Current attempts are aimed at controlling phospholipid and fatty acid levels through the diet or via pharmacological manipulation of lipid metabolism.
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6
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Henkels KM, Rehl KM, Cho KJ. Blocking K-Ras Interaction With the Plasma Membrane Is a Tractable Therapeutic Approach to Inhibit Oncogenic K-Ras Activity. Front Mol Biosci 2021; 8:673096. [PMID: 34222333 PMCID: PMC8244928 DOI: 10.3389/fmolb.2021.673096] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Accepted: 05/20/2021] [Indexed: 12/12/2022] Open
Abstract
Ras proteins are membrane-bound small GTPases that promote cell proliferation, differentiation, and apoptosis. Consistent with this key regulatory role, activating mutations of Ras are present in ∼19% of new cancer cases in the United States per year. K-Ras is one of the three ubiquitously expressed isoforms in mammalian cells, and oncogenic mutations in this isoform account for ∼75% of Ras-driven cancers. Therefore, pharmacological agents that block oncogenic K-Ras activity would have great clinical utility. Most efforts to block oncogenic Ras activity have focused on Ras downstream effectors, but these inhibitors only show limited clinical benefits in Ras-driven cancers due to the highly divergent signals arising from Ras activation. Currently, four major approaches are being extensively studied to target K-Ras–driven cancers. One strategy is to block K-Ras binding to the plasma membrane (PM) since K-Ras requires the PM binding for its signal transduction. Here, we summarize recently identified molecular mechanisms that regulate K-Ras–PM interaction. Perturbing these mechanisms using pharmacological agents blocks K-Ras–PM binding and inhibits K-Ras signaling and growth of K-Ras–driven cancer cells. Together, these studies propose that blocking K-Ras–PM binding is a tractable strategy for developing anti–K-Ras therapies.
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Affiliation(s)
- Karen M Henkels
- Department of Biochemistry and Molecular Biology, School of Boonshoft School of Medicine, Wright State University, Dayton, OH, United States
| | - Kristen M Rehl
- Department of Biochemistry and Molecular Biology, School of Boonshoft School of Medicine, Wright State University, Dayton, OH, United States
| | - Kwang-Jin Cho
- Department of Biochemistry and Molecular Biology, School of Boonshoft School of Medicine, Wright State University, Dayton, OH, United States
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7
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Pandey SK, Paul A, Shteinfer-Kuzmine A, Zalk R, Bunz U, Shoshan-Barmatz V. SMAC/Diablo controls proliferation of cancer cells by regulating phosphatidylethanolamine synthesis. Mol Oncol 2021; 15:3037-3061. [PMID: 33794068 PMCID: PMC8564633 DOI: 10.1002/1878-0261.12959] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Revised: 01/26/2021] [Accepted: 03/31/2021] [Indexed: 01/13/2023] Open
Abstract
SMAC/Diablo, a pro-apoptotic protein, yet it is overexpressed in several cancer types. We have described a noncanonical function for SMAC/Diablo as a regulator of lipid synthesis during cancer cell proliferation and development. Here, we explore the molecular mechanism through which SMAC/Diablo regulates phospholipid synthesis. We showed that SMAC/Diablo directly interacts with mitochondrial phosphatidylserine decarboxylase (PSD) and inhibits its catalytic activity during synthesis of phosphatidylethanolamine (PE) from phosphatidylserine (PS). Unlike other phospholipids (PLs), PE is synthesized not only in the endoplasmic reticulum but also in mitochondria. As a result, PSD activity and mitochondrial PE levels were increased in the mitochondria of SMAC/Diablo-deficient cancer cells, with the total amount of cellular PLs and phosphatidylcholine (PC) being lower as compared to SMAC-expressing cancer cells. Moreover, in the absence of SMAC/Diablo, PSD inhibited cancer cell proliferation by catalysing the overproduction of mitochondrial PE and depleting the cellular levels of PC, PE and PS. Additionally, we demonstrated that both SMAC/Diablo and PSD colocalization in the nucleus resulted in increased levels of nuclear PE, that acts as a signalling molecule in regulating several nuclear activities. By using a peptide array composed of 768-peptides derived from 11 SMAC-interacting proteins, we identified six nuclear proteins ARNT, BIRC2, MAML2, NR4A1, BIRC5 and HTRA2 Five of them also interacted with PSD through motifs that are not involved in SMAC binding. Synthetic peptides carrying the PSD-interacting motifs of these proteins could bind purified PSD and inhibit the PSD catalytic activity. When targeted specifically to the mitochondria or the nucleus, these synthetic peptides inhibited cancer cell proliferation. To our knowledge, these are the first reported inhibitors of PSD acting also as inhibitors of cancer cell proliferation. Altogether, we demonstrated that phospholipid metabolism and PE synthesis regulated by the SMAC-PSD interaction are essential for cancer cell proliferation and may be potentially targeted for treating cancer.
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Affiliation(s)
- Swaroop Kumar Pandey
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel.,National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer Sheva, Israel
| | - Avijit Paul
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel.,National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer Sheva, Israel
| | - Anna Shteinfer-Kuzmine
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel.,National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer Sheva, Israel
| | - Ran Zalk
- Ilse Katz Institute for Nanoscale Science & Technology, Ben-Gurion University of the Negev, Beer Sheva, Israel
| | - Uwe Bunz
- Organisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Germany
| | - Varda Shoshan-Barmatz
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel.,National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer Sheva, Israel
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8
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Kumar S, Chitraju C, Farese RV, Walther TC, Burd CG. Conditional targeting of phosphatidylserine decarboxylase to lipid droplets. Biol Open 2021; 10:bio.058516. [PMID: 33593792 PMCID: PMC7938800 DOI: 10.1242/bio.058516] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Phosphatidylethanolamine is an abundant component of most cellular membranes whose physical and chemical properties modulate multiple aspects of organelle membrane dynamics. An evolutionarily ancient mechanism for producing phosphatidylethanolamine is to decarboxylate phosphatidylserine and the enzyme catalyzing this reaction, phosphatidylserine decarboxylase, localizes to the inner membrane of the mitochondrion. We characterize a second form of phosphatidylserine decarboxylase, termed PISD-LD, that is generated by alternative splicing of PISD pre-mRNA and localizes to lipid droplets and to mitochondria. Sub-cellular targeting is controlled by a common segment of PISD-LD that is distinct from the catalytic domain and is regulated by nutritional state. Growth conditions that promote neutral lipid storage in lipid droplets favors targeting to lipid droplets, while targeting to mitochondria is favored by conditions that promote consumption of lipid droplets. Depletion of both forms of phosphatidylserine decarboxylase impairs triacylglycerol synthesis when cells are challenged with free fatty acid, indicating a crucial role phosphatidylserine decarboxylase in neutral lipid storage. The results reveal a previously unappreciated role for phosphatidylserine decarboxylase in lipid droplet biogenesis.
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Affiliation(s)
- Santosh Kumar
- Department of Cell Biology, Yale School of Medicine, New Haven, Connecticut 06520, USA
| | - Chandramohan Chitraju
- Department of Molecular Metabolism, Harvard T.H. Chan School of Public Health, Boston, MA 02115, USA.,Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Robert V Farese
- Department of Molecular Metabolism, Harvard T.H. Chan School of Public Health, Boston, MA 02115, USA.,Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA.,Broad Institute of Harvard and MIT, Cambridge, MA 02142, USA
| | - Tobias C Walther
- Department of Molecular Metabolism, Harvard T.H. Chan School of Public Health, Boston, MA 02115, USA.,Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA.,Broad Institute of Harvard and MIT, Cambridge, MA 02142, USA.,Howard Hughes Medical Institute, Boston, MA 02115, USA
| | - Christopher G Burd
- Department of Cell Biology, Yale School of Medicine, New Haven, Connecticut 06520, USA
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9
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Zhao H, Wang T. PE homeostasis rebalanced through mitochondria-ER lipid exchange prevents retinal degeneration in Drosophila. PLoS Genet 2020; 16:e1009070. [PMID: 33064773 PMCID: PMC7592913 DOI: 10.1371/journal.pgen.1009070] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Revised: 10/28/2020] [Accepted: 08/21/2020] [Indexed: 02/06/2023] Open
Abstract
The major glycerophospholipid phosphatidylethanolamine (PE) in the nervous system is essential for neural development and function. There are two major PE synthesis pathways, the CDP-ethanolamine pathway in the endoplasmic reticulum (ER) and the phosphatidylserine decarboxylase (PSD) pathway in mitochondria. However, the role played by mitochondrial PE synthesis in maintaining cellular PE homeostasis is unknown. Here, we show that Drosophila pect (phosphoethanolamine cytidylyltransferase) mutants lacking the CDP-ethanolamine pathway, exhibited alterations in phospholipid composition, defective phototransduction, and retinal degeneration. Induction of the PSD pathway fully restored levels and composition of cellular PE, thus rescued the retinal degeneration and defective visual responses in pect mutants. Disrupting lipid exchange between mitochondria and ER blocked the ability of PSD to rescue pect mutant phenotypes. These findings provide direct evidence that the synthesis of PE in mitochondria contributes to cellular PE homeostasis, and suggest the induction of mitochondrial PE synthesis as a promising therapeutic approach for disorders associated with PE deficiency.
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Affiliation(s)
- Haifang Zhao
- National Institute of Biological Sciences, Beijing, China
| | - Tao Wang
- National Institute of Biological Sciences, Beijing, China
- Tsinghua Institute of Multidisciplinary Biomedical Research, Tsinghua University, Beijing, China
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10
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Montesinos J, Area-Gomez E, Schlame M. Analysis of phospholipid synthesis in mitochondria. Methods Cell Biol 2020; 155:321-335. [PMID: 32183965 DOI: 10.1016/bs.mcb.2019.12.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Mitochondria and their associated membranes actively participate in biosynthesis, trafficking, and degradation of cellular phospholipids. Two crucial lipid biosynthetic activities of mitochondria include (i) the decarboxylation of phosphatidylserine to phosphatidylethanolamine and (ii) the de novo synthesis of cardiolipin. Here we describe protocols to measure these two activities, applying isotope-labeled or exogenous substrates in combination with thin-layer chromatography or mass spectrometry.
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Affiliation(s)
- Jorge Montesinos
- Department of Neurology, Columbia University Medical Center, New York, NY, United States
| | - Estela Area-Gomez
- Department of Neurology, Columbia University Medical Center, New York, NY, United States
| | - Michael Schlame
- Departments of Anesthesiology and Cell Biology, New York University School of Medicine, New York, NY, United States.
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11
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Miller TE, Henkels KM, Huddleston M, Salisbury R, Hussain SM, Sasaki AT, Cho KJ. Depletion of phosphatidylinositol 4-phosphate at the Golgi translocates K-Ras to mitochondria. J Cell Sci 2019; 132:jcs.231886. [PMID: 31331963 DOI: 10.1242/jcs.231886] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Accepted: 07/12/2019] [Indexed: 01/05/2023] Open
Abstract
Ras proteins are small GTPases localized to the plasma membrane (PM), which regulate cellular proliferation, apoptosis and differentiation. After a series of post-translational modifications, H-Ras and N-Ras traffic to the PM from the Golgi via the classical exocytic pathway, but the exact mechanism of K-Ras trafficking to the PM from the ER is not fully characterized. ATP5G1 (also known as ATP5MC1) is one of the three proteins that comprise subunit c of the F 0 complex of the mitochondrial ATP synthase. In this study, we show that overexpression of the mitochondrial targeting sequence of ATP5G1 perturbs glucose metabolism, inhibits oncogenic K-Ras signaling, and redistributes phosphatidylserine (PtdSer) to mitochondria and other endomembranes, resulting in K-Ras translocation to mitochondria. Also, it depletes phosphatidylinositol 4-phosphate (PI4P) at the Golgi. Glucose supplementation restores PtdSer and K-Ras PM localization and PI4P at the Golgi. We further show that inhibition of the Golgi-localized PI4-kinases (PI4Ks) translocates K-Ras, and PtdSer to mitochondria and endomembranes, respectively. We conclude that PI4P at the Golgi regulates the PM localization of PtdSer and K-Ras.This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Taylor E Miller
- Department of Biochemistry and Molecular Biology, Boonshoft School of Medicine, Wright State University, OH 45435, USA
| | - Karen M Henkels
- Department of Biochemistry and Molecular Biology, Boonshoft School of Medicine, Wright State University, OH 45435, USA
| | - Mary Huddleston
- Human Signatures Branch, Human-Centered ISR Division, Airman Systems Directorate, 711 Human Performance Wing, Air Force Research Laboratory, Wright Patterson Air Force Base, OH 45433, USA
| | - Richard Salisbury
- Human Signatures Branch, Human-Centered ISR Division, Airman Systems Directorate, 711 Human Performance Wing, Air Force Research Laboratory, Wright Patterson Air Force Base, OH 45433, USA
| | - Saber M Hussain
- Human Signatures Branch, Human-Centered ISR Division, Airman Systems Directorate, 711 Human Performance Wing, Air Force Research Laboratory, Wright Patterson Air Force Base, OH 45433, USA
| | - Atsuo T Sasaki
- Division of Hematology and Oncology, Department of Internal Medicine, University of Cincinnati, Cincinnati, OH 45267, USA
| | - Kwang-Jin Cho
- Department of Biochemistry and Molecular Biology, Boonshoft School of Medicine, Wright State University, OH 45435, USA
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12
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The Liberfarb syndrome, a multisystem disorder affecting eye, ear, bone, and brain development, is caused by a founder pathogenic variant in thePISD gene. Genet Med 2019; 21:2734-2743. [PMID: 31263216 PMCID: PMC6892740 DOI: 10.1038/s41436-019-0595-x] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Accepted: 06/17/2019] [Indexed: 01/24/2023] Open
Abstract
Purpose We observed four individuals in two unrelated but consanguineous
families from Portugal and Brazil affected by early-onset retinal degeneration,
sensorineural hearing loss, microcephaly, intellectual disability, and skeletal
dysplasia with scoliosis and short stature. The phenotype precisely matched that
of an individual of Azorean descent published in 1986 by Liberfarb and
coworkers. Methods Patients underwent specialized clinical examinations (including
ophthalmological, audiological, orthopedic, radiological, and developmental
assessment). Exome and targeted sequencing was performed on selected
individuals. Minigene constructs were assessed by quantitative polymerase chain
reaction (qPCR) and Sanger sequencing. Results Affected individuals shared a 3.36-Mb region of autozygosity on
chromosome 22q12.2, including a 10-bp deletion
(NM_014338.3:c.904-12_904-3delCTATCACCAC), immediately upstream of the last exon
of the PISD (phosphatidylserine
decarboxylase) gene. Sequencing of PISD from
paraffin-embedded tissue from the 1986 case revealed the identical homozygous
variant. In HEK293T cells, this variant led to aberrant splicing of PISD transcripts. Conclusion We have identified the genetic etiology of the Liberfarb syndrome,
affecting brain, eye, ear, bone, and connective tissue. Our work documents the
migration of a rare Portuguese founder variant to two continents and highlights
the link between phospholipid metabolism and bone formation, sensory defects,
and cerebral development, while raising the possibility of therapeutic
phospholipid replacement.
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13
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Phosphatidylserine decarboxylase is critical for the maintenance of skeletal muscle mitochondrial integrity and muscle mass. Mol Metab 2019; 27:33-46. [PMID: 31285171 PMCID: PMC6717954 DOI: 10.1016/j.molmet.2019.06.020] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Revised: 06/12/2019] [Accepted: 06/23/2019] [Indexed: 11/24/2022] Open
Abstract
Objective Phosphatidylethanolamine (PtdEtn) is a major phospholipid in mammals. It is synthesized via two pathways, the CDP-ethanolamine pathway in the endoplasmic reticulum and the phosphatidylserine (PtdSer) decarboxylase (PSD) pathway in the mitochondria. While the CDP-ethanolamine pathway is considered the major route for PtdEtn synthesis in most mammalian tissues, little is known about the importance of the PSD pathway in vivo, especially in tissues enriched with mitochondria such as skeletal muscle. Therefore, we aimed to examine the role of the mitochondrial PSD pathway in regulating PtdEtn homeostasis in skeletal muscle in vivo. Methods To determine the functional significance of this pathway in skeletal muscle in vivo, an adeno-associated viral vector approach was employed to knockdown PSD expression in skeletal muscle of adult mice. Muscle lipid and metabolite profiling was performed using mass spectrometry. Results PSD knockdown disrupted muscle phospholipid homeostasis leading to an ∼25% reduction in PtdEtn and an ∼45% increase in PtdSer content. This was accompanied by the development of a severe myopathy, evident by a 40% loss in muscle mass as well as extensive myofiber damage as shown by increased DNA synthesis and central nucleation. In addition, PSD knockdown caused marked accumulation of abnormally appearing mitochondria that exhibited severely disrupted inner membrane integrity and reduced OXPHOS protein content. Conclusions The PSD pathway has a significant role in maintaining phospholipid homeostasis in adult skeletal muscle. Moreover, PSD is essential for maintenance of mitochondrial integrity and skeletal muscle mass. The PSD pathway has an important role in regulating muscle phospholipid homeostasis. Disrupting the PSD pathway caused marked muscle wasting and myofibre damage. Knockdown of PSD caused accumulation of mitochondria with ultrastructural defects. PSD is important in regulating mitochondrial integrity and skeletal muscle mass.
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14
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Zhao T, Goedhart CM, Sam PN, Sabouny R, Lingrell S, Cornish AJ, Lamont RE, Bernier FP, Sinasac D, Parboosingh JS, Vance JE, Claypool SM, Innes AM, Shutt TE. PISD is a mitochondrial disease gene causing skeletal dysplasia, cataracts, and white matter changes. Life Sci Alliance 2019; 2:2/2/e201900353. [PMID: 30858161 PMCID: PMC6412922 DOI: 10.26508/lsa.201900353] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Revised: 02/25/2019] [Accepted: 02/26/2019] [Indexed: 12/18/2022] Open
Abstract
This work demonstrates that pathogenic variants in PISD cause mitochondrial disease and suggests a novel mechanistic link whereby impaired lipid content in the inner mitochondrial membrane alters the activity of inner mitochondrial membrane proteases. Exome sequencing of two sisters with congenital cataracts, short stature, and white matter changes identified compound heterozygous variants in the PISD gene, encoding the phosphatidylserine decarboxylase enzyme that converts phosphatidylserine to phosphatidylethanolamine (PE) in the inner mitochondrial membrane (IMM). Decreased conversion of phosphatidylserine to PE in patient fibroblasts is consistent with impaired phosphatidylserine decarboxylase (PISD) enzyme activity. Meanwhile, as evidence for mitochondrial dysfunction, patient fibroblasts exhibited more fragmented mitochondrial networks, enlarged lysosomes, decreased maximal oxygen consumption rates, and increased sensitivity to 2-deoxyglucose. Moreover, treatment with lyso-PE, which can replenish the mitochondrial pool of PE, and genetic complementation restored mitochondrial and lysosome morphology in patient fibroblasts. Functional characterization of the PISD variants demonstrates that the maternal variant causes an alternative splice product. Meanwhile, the paternal variant impairs autocatalytic self-processing of the PISD protein required for its activity. Finally, evidence for impaired activity of mitochondrial IMM proteases suggests an explanation as to why the phenotypes of these PISD patients resemble recently described “mitochondrial chaperonopathies.” Collectively, these findings demonstrate that PISD is a novel mitochondrial disease gene.
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Affiliation(s)
- Tian Zhao
- Alberta Children's Hospital Research Institute, Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.,Department of Biochemistry and Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Caitlin M Goedhart
- Alberta Children's Hospital Research Institute, Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Pingdewinde N Sam
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Rasha Sabouny
- Alberta Children's Hospital Research Institute, Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.,Department of Biochemistry and Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Susanne Lingrell
- Department of Medicine and Group on Molecular and Cell Biology of Lipids, University of Alberta, Edmonton, Alberta, Canada
| | - Adam J Cornish
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Ryan E Lamont
- Alberta Children's Hospital Research Institute, Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Francois P Bernier
- Alberta Children's Hospital Research Institute, Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.,Department of Pediatrics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - David Sinasac
- Alberta Children's Hospital Research Institute, Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Jillian S Parboosingh
- Alberta Children's Hospital Research Institute, Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | | | - Jean E Vance
- Department of Medicine and Group on Molecular and Cell Biology of Lipids, University of Alberta, Edmonton, Alberta, Canada
| | - Steven M Claypool
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - A Micheil Innes
- Alberta Children's Hospital Research Institute, Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada .,Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.,Department of Pediatrics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Timothy E Shutt
- Alberta Children's Hospital Research Institute, Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada .,Department of Biochemistry and Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.,Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
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15
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Girisha KM, von Elsner L, Neethukrishna K, Muranjan M, Shukla A, Bhavani GS, Nishimura G, Kutsche K, Mortier G. The homozygous variant c.797G>A/p.(Cys266Tyr) in PISD is associated with a Spondyloepimetaphyseal dysplasia with large epiphyses and disturbed mitochondrial function. Hum Mutat 2018; 40:299-309. [PMID: 30488656 DOI: 10.1002/humu.23693] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Revised: 11/16/2018] [Accepted: 11/24/2018] [Indexed: 02/06/2023]
Abstract
Spondyloepimetaphyseal dysplasias (SEMD) are a group of genetically heterogeneous skeletal disorders characterized by abnormal vertebral bodies and epimetaphyseal abnormalities. We investigated two families with a new SEMD type with one proband each. They showed mild facial dysmorphism, flat vertebral bodies (platyspondyly), large epiphyses, metaphyseal dysplasia, and hallux valgus as common clinical features. By trio-exome sequencing, the homozygous missense variant c.797G>A/p.(Cys266Tyr) in PISD was found in both affected individuals. Based on exome data analyses for homozygous regions, the two patients shared a single homozygous block on chromosome 22 including PISD, indicating their remote consanguinity. PISD encodes phosphatidylserine (PS) decarboxylase that is localized in the inner mitochondrial membrane and catalyzes the decarboxylation of PS to phosphatidylethanolamine (PE) in mammalian cells. PE occurs at high abundance in mitochondrial membranes. Patient-derived fibroblasts showed fragmented mitochondrial morphology. Treatment of patient cells with MG-132 or staurosporine to induce activation of the intrinsic apoptosis pathway revealed significantly decreased cell viability with increased caspase-3 and caspase-7 activation. Remarkably, ethanolamine (Etn) supplementation largely restored cell viability and enhanced apoptosis in MG-132-stressed patient cells. Our data demonstrate that the biallelic hypomorphic PISD variant p.(Cys266Tyr) is associated with a novel SEMD form, which may be treatable with Etn administration.
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Affiliation(s)
- Katta M Girisha
- Department of Medical Genetics, Kasturba Medical College, Manipal Academy of Higher Education, Manipal, India
| | - Leonie von Elsner
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Kausthubham Neethukrishna
- Department of Medical Genetics, Kasturba Medical College, Manipal Academy of Higher Education, Manipal, India
| | - Mamta Muranjan
- Department of Clinical Genetics, Seth GS Medical College and KEM Hospital, Mumbai, India.,Consultant in Clinical Genetics, P.D. Hinduja National Hospital & MRC, Mumbai, India
| | - Anju Shukla
- Department of Medical Genetics, Kasturba Medical College, Manipal Academy of Higher Education, Manipal, India
| | - Gandham SriLakshmi Bhavani
- Department of Medical Genetics, Kasturba Medical College, Manipal Academy of Higher Education, Manipal, India
| | - Gen Nishimura
- Department of Pediatric Imaging, Tokyo Metropolitan Children's Medical Center, Fuchu, Japan
| | - Kerstin Kutsche
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Geert Mortier
- Centre of Medical Genetics, University of Antwerp & University Hospital Antwerp, Antwerp, Belgium
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16
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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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17
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Ethanolamine and Phosphatidylethanolamine: Partners in Health and Disease. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2017; 2017:4829180. [PMID: 28785375 PMCID: PMC5529665 DOI: 10.1155/2017/4829180] [Citation(s) in RCA: 206] [Impact Index Per Article: 29.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/25/2017] [Accepted: 06/01/2017] [Indexed: 12/18/2022]
Abstract
Phosphatidylethanolamine (PE) is the second most abundant phospholipid in mammalian cells. PE comprises about 15–25% of the total lipid in mammalian cells; it is enriched in the inner leaflet of membranes, and it is especially abundant in the inner mitochondrial membrane. PE has quite remarkable activities: it is a lipid chaperone that assists in the folding of certain membrane proteins, it is required for the activity of several of the respiratory complexes, and it plays a key role in the initiation of autophagy. In this review, we focus on PE's roles in lipid-induced stress in the endoplasmic reticulum (ER), Parkinson's disease (PD), ferroptosis, and cancer.
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18
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van der Veen JN, Kennelly JP, Wan S, Vance JE, Vance DE, Jacobs RL. The critical role of phosphatidylcholine and phosphatidylethanolamine metabolism in health and disease. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:1558-1572. [PMID: 28411170 DOI: 10.1016/j.bbamem.2017.04.006] [Citation(s) in RCA: 921] [Impact Index Per Article: 131.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Revised: 03/27/2017] [Accepted: 04/09/2017] [Indexed: 12/11/2022]
Abstract
Phosphatidylcholine (PC) and phosphatidylethanolamine (PE) are the most abundant phospholipids in all mammalian cell membranes. In the 1950s, Eugene Kennedy and co-workers performed groundbreaking research that established the general outline of many of the pathways of phospholipid biosynthesis. In recent years, the importance of phospholipid metabolism in regulating lipid, lipoprotein and whole-body energy metabolism has been demonstrated in numerous dietary studies and knockout animal models. The purpose of this review is to highlight the unappreciated impact of phospholipid metabolism on health and disease. Abnormally high, and abnormally low, cellular PC/PE molar ratios in various tissues can influence energy metabolism and have been linked to disease progression. For example, inhibition of hepatic PC synthesis impairs very low density lipoprotein secretion and changes in hepatic phospholipid composition have been linked to fatty liver disease and impaired liver regeneration after surgery. The relative abundance of PC and PE regulates the size and dynamics of lipid droplets. In mitochondria, changes in the PC/PE molar ratio affect energy production. We highlight data showing that changes in the PC and/or PE content of various tissues are implicated in metabolic disorders such as atherosclerosis, insulin resistance and obesity. This article is part of a Special Issue entitled: Membrane Lipid Therapy: Drugs Targeting Biomembranes edited by Pablo V. Escribá.
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Affiliation(s)
- Jelske N van der Veen
- Group on the Molecular and Cell Biology of Lipids, Canada; Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2S2, Canada
| | - John P Kennelly
- Group on the Molecular and Cell Biology of Lipids, Canada; Department of Agricultural, Food and Nutritional Science, 4-002 Li Ka Shing Centre for Heath Research Innovations, University of Alberta, Edmonton, AB T6G 2E1, Canada
| | - Sereana Wan
- Group on the Molecular and Cell Biology of Lipids, Canada; Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2S2, Canada
| | - Jean E Vance
- Group on the Molecular and Cell Biology of Lipids, Canada; Department of Medicine, University of Alberta, Edmonton, AB T6G 2S2, Canada
| | - Dennis E Vance
- Group on the Molecular and Cell Biology of Lipids, Canada; Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2S2, Canada
| | - René L Jacobs
- Group on the Molecular and Cell Biology of Lipids, Canada; Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2S2, Canada; Department of Agricultural, Food and Nutritional Science, 4-002 Li Ka Shing Centre for Heath Research Innovations, University of Alberta, Edmonton, AB T6G 2E1, Canada.
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19
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Schreiner B, Ankarcrona M. Isolation of Mitochondria-Associated Membranes (MAM) from Mouse Brain Tissue. Methods Mol Biol 2017; 1567:53-68. [PMID: 28276013 DOI: 10.1007/978-1-4939-6824-4_5] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
During the last decades, increasing evidence indicated that subcellular organelles do not exist as autarkic units but instead communicate constantly and extensively with each other in various ways. Some communication, for example, the exchange of small molecules, requires the marked convergence of two distinct organelles for a certain period of time. The cross talk between endoplasmic reticulum (ER) and mitochondria, two subcellular organelles of utmost importance for cellular bioenergetics and protein homeostasis, has been increasingly investigated under the last years. This development was significantly driven by the establishment of optimized subcellular fractionation techniques. In this chapter, we will describe and critically discuss the currently used protocol for the isolation of the membrane fraction containing mitochondria-associated membranes (MAM).
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Affiliation(s)
- Bernadette Schreiner
- Center for Alzheimer Research, Division of Neurogeriatrics, Department of Neurobiology, Care Sciences and Society,, Karolinska Institutet, SE, -141 57, Huddinge, Sweden.
| | - Maria Ankarcrona
- Center for Alzheimer Research, Division of Neurogeriatrics, Department of Neurobiology, Care Sciences and Society,, Karolinska Institutet, SE, -141 57, Huddinge, Sweden
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20
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Di Bartolomeo F, Wagner A, Daum G. Cell biology, physiology and enzymology of phosphatidylserine decarboxylase. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1862:25-38. [PMID: 27650064 DOI: 10.1016/j.bbalip.2016.09.007] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Revised: 09/02/2016] [Accepted: 09/10/2016] [Indexed: 12/17/2022]
Abstract
Phosphatidylethanolamine is one of the most abundant phospholipids whose major amounts are formed by phosphatidylserine decarboxylases (PSD). Here we provide a comprehensive description of different types of PSDs in the different kingdoms of life. In eukaryotes, type I PSDs are mitochondrial enzymes, whereas other PSDs are localized to other cellular compartments. We describe the role of mitochondrial Psd1 proteins, their function, enzymology, biogenesis, assembly into mitochondria and their contribution to phospholipid homeostasis in much detail. We also discuss briefly the cellular physiology and the enzymology of Psd2. This article is part of a Special Issue entitled: Lipids of Mitochondria edited by Guenther Daum.
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Affiliation(s)
- Francesca Di Bartolomeo
- Institute of Biochemistry, Graz University of Technology, Petersgasse 12/2, A-8010 Graz, Austria
| | - Ariane Wagner
- Institute of Biochemistry, Graz University of Technology, Petersgasse 12/2, A-8010 Graz, Austria
| | - Günther Daum
- Institute of Biochemistry, Graz University of Technology, Petersgasse 12/2, A-8010 Graz, Austria.
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21
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Junker M, Rapoport TA. Involvement of VAT-1 in Phosphatidylserine Transfer from the Endoplasmic Reticulum to Mitochondria. Traffic 2015; 16:1306-17. [DOI: 10.1111/tra.12336] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Revised: 09/17/2015] [Accepted: 09/17/2015] [Indexed: 11/29/2022]
Affiliation(s)
- Mirco Junker
- Howard Hughes Medical Institute and Department of Cell Biology; Harvard Medical School; 240 Longwood Avenue Boston MA 02115 USA
| | - Tom A. Rapoport
- Howard Hughes Medical Institute and Department of Cell Biology; Harvard Medical School; 240 Longwood Avenue Boston MA 02115 USA
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22
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Raghupathy R, Anilkumar AA, Polley A, Singh PP, Yadav M, Johnson C, Suryawanshi S, Saikam V, Sawant SD, Panda A, Guo Z, Vishwakarma RA, Rao M, Mayor S. Transbilayer lipid interactions mediate nanoclustering of lipid-anchored proteins. Cell 2015; 161:581-594. [PMID: 25910209 DOI: 10.1016/j.cell.2015.03.048] [Citation(s) in RCA: 279] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Revised: 11/12/2014] [Accepted: 03/18/2015] [Indexed: 01/22/2023]
Abstract
Understanding how functional lipid domains in live cell membranes are generated has posed a challenge. Here, we show that transbilayer interactions are necessary for the generation of cholesterol-dependent nanoclusters of GPI-anchored proteins mediated by membrane-adjacent dynamic actin filaments. We find that long saturated acyl-chains are required for forming GPI-anchor nanoclusters. Simultaneously, at the inner leaflet, long acyl-chain-containing phosphatidylserine (PS) is necessary for transbilayer coupling. All-atom molecular dynamics simulations of asymmetric multicomponent-membrane bilayers in a mixed phase provide evidence that immobilization of long saturated acyl-chain lipids at either leaflet stabilizes cholesterol-dependent transbilayer interactions forming local domains with characteristics similar to a liquid-ordered (lo) phase. This is verified by experiments wherein immobilization of long acyl-chain lipids at one leaflet effects transbilayer interactions of corresponding lipids at the opposite leaflet. This suggests a general mechanism for the generation and stabilization of nanoscale cholesterol-dependent and actin-mediated lipid clusters in live cell membranes.
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Affiliation(s)
- Riya Raghupathy
- National Centre for Biological Sciences (TIFR), Bellary Road, Bangalore 560 065, India; Shanmugha Arts, Science, Technology & Research Academy, Thanjavur 613401, India
| | - Anupama Ambika Anilkumar
- National Centre for Biological Sciences (TIFR), Bellary Road, Bangalore 560 065, India; Shanmugha Arts, Science, Technology & Research Academy, Thanjavur 613401, India
| | - Anirban Polley
- Raman Research Institute, C.V. Raman Avenue, Bangalore 560 080, India; Tampere University of Technology, Korkeakoulunkatu 10, 33720 Tampere, Finland
| | - Parvinder Pal Singh
- Indian Institute of Integrative Medicine (CSIR), Canal Road, Jammu 180001, India
| | - Mahipal Yadav
- Indian Institute of Integrative Medicine (CSIR), Canal Road, Jammu 180001, India
| | - Charles Johnson
- Wayne State University, 5101 Cass Avenue, Detroit, MI 48202, USA
| | | | - Varma Saikam
- Indian Institute of Integrative Medicine (CSIR), Canal Road, Jammu 180001, India
| | - Sanghapal D Sawant
- Indian Institute of Integrative Medicine (CSIR), Canal Road, Jammu 180001, India
| | - Aniruddha Panda
- National Centre for Biological Sciences (TIFR), Bellary Road, Bangalore 560 065, India; Manipal University, Madhav Nagar, Manipal 576104, Karnataka, India
| | - Zhongwu Guo
- Wayne State University, 5101 Cass Avenue, Detroit, MI 48202, USA
| | - Ram A Vishwakarma
- Indian Institute of Integrative Medicine (CSIR), Canal Road, Jammu 180001, India
| | - Madan Rao
- National Centre for Biological Sciences (TIFR), Bellary Road, Bangalore 560 065, India; Raman Research Institute, C.V. Raman Avenue, Bangalore 560 080, India.
| | - Satyajit Mayor
- National Centre for Biological Sciences (TIFR), Bellary Road, Bangalore 560 065, India; Institute for Stem Cell Biology and Regenerative Medicine, Bellary Road, Bangalore 560 065, India.
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23
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Dorninger F, Brodde A, Braverman NE, Moser AB, Just WW, Forss-Petter S, Brügger B, Berger J. Homeostasis of phospholipids - The level of phosphatidylethanolamine tightly adapts to changes in ethanolamine plasmalogens. Biochim Biophys Acta Mol Cell Biol Lipids 2014; 1851:117-28. [PMID: 25463479 PMCID: PMC4331674 DOI: 10.1016/j.bbalip.2014.11.005] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2014] [Revised: 11/04/2014] [Accepted: 11/10/2014] [Indexed: 01/19/2023]
Abstract
Ethanolamine plasmalogens constitute a group of ether glycerophospholipids that, due to their unique biophysical and biochemical properties, are essential components of mammalian cellular membranes. Their importance is emphasized by the consequences of defects in plasmalogen biosynthesis, which in humans cause the fatal disease rhizomelic chondrodysplasia punctata (RCDP). In the present lipidomic study, we used fibroblasts derived from RCDP patients, as well as brain tissue from plasmalogen-deficient mice, to examine the compensatory mechanisms of lipid homeostasis in response to plasmalogen deficiency. Our results show that phosphatidylethanolamine (PE), a diacyl glycerophospholipid, which like ethanolamine plasmalogens carries the head group ethanolamine, is the main player in the adaptation to plasmalogen insufficiency. PE levels were tightly adjusted to the amount of ethanolamine plasmalogens so that their combined levels were kept constant. Similarly, the total amount of polyunsaturated fatty acids (PUFAs) in ethanolamine phospholipids was maintained upon plasmalogen deficiency. However, we found an increased incorporation of arachidonic acid at the expense of docosahexaenoic acid in the PE fraction of plasmalogen-deficient tissues. These data show that under conditions of reduced plasmalogen levels, the amount of total ethanolamine phospholipids is precisely maintained by a rise in PE. At the same time, a shift in the ratio between ω-6 and ω-3 PUFAs occurs, which might have unfavorable, long-term biological consequences. Therefore, our findings are not only of interest for RCDP but may have more widespread implications also for other disease conditions, as for example Alzheimer's disease, that have been associated with a decline in plasmalogens. PE accurately compensates for the lack of plasmalogens in vitro and in vivo. PE levels decrease to adapt to excess of ethanolamine plasmalogens (PlsEtn). Plasmalogen deficiency favors incorporation of arachidonic acid into PE. Docosahexaenoic acid in ethanolamine phospholipids decreases upon PlsEtn depletion.
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Affiliation(s)
- Fabian Dorninger
- Department of Pathobiology of the Nervous System, Center for Brain Research, Medical University of Vienna, Spitalgasse 4, 1090 Vienna, Austria.
| | - Alexander Brodde
- Heidelberg University Biochemistry Center, Im Neuenheimer Feld 328, 69120 Heidelberg, Germany.
| | - Nancy E Braverman
- Department of Human Genetics and Pediatrics, McGill University-Montreal Children's Hospital, 4060 Ste-Catherine West, PT-406.2, Montreal, QC H3Z 2Z3, Canada.
| | - Ann B Moser
- Peroxisomal Diseases Laboratory, The Hugo W Moser Research Institute, The Kennedy Krieger Institute, 707 N. Broadway, Baltimore, MD 21205, USA.
| | - Wilhelm W Just
- Heidelberg University Biochemistry Center, Im Neuenheimer Feld 328, 69120 Heidelberg, Germany.
| | - Sonja Forss-Petter
- Department of Pathobiology of the Nervous System, Center for Brain Research, Medical University of Vienna, Spitalgasse 4, 1090 Vienna, Austria.
| | - Britta Brügger
- Heidelberg University Biochemistry Center, Im Neuenheimer Feld 328, 69120 Heidelberg, Germany.
| | - Johannes Berger
- Department of Pathobiology of the Nervous System, Center for Brain Research, Medical University of Vienna, Spitalgasse 4, 1090 Vienna, Austria.
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24
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Hartmann A, Hellmund M, Lucius R, Voelker DR, Gupta N. Phosphatidylethanolamine synthesis in the parasite mitochondrion is required for efficient growth but dispensable for survival of Toxoplasma gondii. J Biol Chem 2014; 289:6809-6824. [PMID: 24429285 DOI: 10.1074/jbc.m113.509406] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Toxoplasma gondii is a highly prevalent obligate intracellular parasite of the phylum Apicomplexa, which also includes other parasites of clinical and/or veterinary importance, such as Plasmodium, Cryptosporidium, and Eimeria. Acute infection by Toxoplasma is hallmarked by rapid proliferation in its host cells and requires a significant synthesis of parasite membranes. Phosphatidylethanolamine (PtdEtn) is the second major phospholipid class in T. gondii. Here, we reveal that PtdEtn is produced in the parasite mitochondrion and parasitophorous vacuole by decarboxylation of phosphatidylserine (PtdSer) and in the endoplasmic reticulum by fusion of CDP-ethanolamine and diacylglycerol. PtdEtn in the mitochondrion is synthesized by a phosphatidylserine decarboxylase (TgPSD1mt) of the type I class. TgPSD1mt harbors a targeting peptide at its N terminus that is required for the mitochondrial localization but not for the catalytic activity. Ablation of TgPSD1mt expression caused up to 45% growth impairment in the parasite mutant. The PtdEtn content of the mutant was unaffected, however, suggesting the presence of compensatory mechanisms. Indeed, metabolic labeling revealed an increased usage of ethanolamine for PtdEtn synthesis by the mutant. Likewise, depletion of nutrients exacerbated the growth defect (∼56%), which was partially restored by ethanolamine. Besides, the survival and residual growth of the TgPSD1mt mutant in the nutrient-depleted medium also indicated additional routes of PtdEtn biogenesis, such as acquisition of host-derived lipid. Collectively, the work demonstrates a metabolic cooperativity between the parasite organelles, which ensures a sustained lipid synthesis, survival and growth of T. gondii in varying nutritional milieus.
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Affiliation(s)
- Anne Hartmann
- Department of Molecular Parasitology, Humboldt University, Philippstrasse 13, 10115 Berlin, Germany
| | - Maria Hellmund
- Department of Molecular Parasitology, Humboldt University, Philippstrasse 13, 10115 Berlin, Germany
| | - Richard Lucius
- Department of Molecular Parasitology, Humboldt University, Philippstrasse 13, 10115 Berlin, Germany
| | - Dennis R Voelker
- Department of Medicine, National Jewish Health, Denver, Colorado 80206
| | - Nishith Gupta
- Department of Molecular Parasitology, Humboldt University, Philippstrasse 13, 10115 Berlin, Germany; Department of Parasitology, Max-Planck Institute for Infection Biology, Charitéplatz 1, 10117 Berlin, Germany.
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25
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MAM (mitochondria-associated membranes) in mammalian cells: lipids and beyond. Biochim Biophys Acta Mol Cell Biol Lipids 2013; 1841:595-609. [PMID: 24316057 DOI: 10.1016/j.bbalip.2013.11.014] [Citation(s) in RCA: 446] [Impact Index Per Article: 40.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2013] [Revised: 11/21/2013] [Accepted: 11/27/2013] [Indexed: 12/15/2022]
Abstract
One mechanism by which communication between the endoplasmic reticulum (ER) and mitochondria is achieved is by close juxtaposition between these organelles via mitochondria-associated membranes (MAM). The MAM consist of a region of the ER that is enriched in several lipid biosynthetic enzyme activities and becomes reversibly tethered to mitochondria. Specific proteins are localized, sometimes transiently, in the MAM. Several of these proteins have been implicated in tethering the MAM to mitochondria. In mammalian cells, formation of these contact sites between MAM and mitochondria appears to be required for key cellular events including the transport of calcium from the ER to mitochondria, the import of phosphatidylserine into mitochondria from the ER for decarboxylation to phosphatidylethanolamine, the formation of autophagosomes, regulation of the morphology, dynamics and functions of mitochondria, and cell survival. This review focuses on the functions proposed for MAM in mediating these events in mammalian cells. In light of the apparent involvement of MAM in multiple fundamental cellular processes, recent studies indicate that impaired contact between MAM and mitochondria might underlie the pathology of several human neurodegenerative diseases, including Alzheimer's disease. Moreover, MAM has been implicated in modulating glucose homeostasis and insulin resistance, as well as in some viral infections.
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Bohdanowicz M, Grinstein S. Role of Phospholipids in Endocytosis, Phagocytosis, and Macropinocytosis. Physiol Rev 2013; 93:69-106. [DOI: 10.1152/physrev.00002.2012] [Citation(s) in RCA: 198] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Endocytosis, phagocytosis, and macropinocytosis are fundamental processes that enable cells to sample their environment, eliminate pathogens and apoptotic bodies, and regulate the expression of surface components. While a great deal of effort has been devoted over many years to understanding the proteins involved in these processes, the important contribution of phospholipids has only recently been appreciated. This review is an attempt to collate and analyze the rapidly emerging evidence documenting the role of phospholipids in clathrin-mediated endocytosis, phagocytosis, and macropinocytosis. A primer on phospholipid biosynthesis, catabolism, subcellular distribution, and transport is presented initially, for reference, together with general considerations of the effects of phospholipids on membrane curvature and charge. This is followed by a detailed analysis of the critical functions of phospholipids in the internalization processes and in the maturation of the resulting vesicles and vacuoles as they progress along the endo-lysosomal pathway.
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Affiliation(s)
- Michal Bohdanowicz
- Division of Cell Biology, Hospital for Sick Children, and Institute of Medical Sciences, University of Toronto, Toronto, Canada
| | - Sergio Grinstein
- Division of Cell Biology, Hospital for Sick Children, and Institute of Medical Sciences, University of Toronto, Toronto, Canada
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Vance JE, Tasseva G. Formation and function of phosphatidylserine and phosphatidylethanolamine in mammalian cells. Biochim Biophys Acta Mol Cell Biol Lipids 2012; 1831:543-54. [PMID: 22960354 DOI: 10.1016/j.bbalip.2012.08.016] [Citation(s) in RCA: 382] [Impact Index Per Article: 31.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2012] [Revised: 08/20/2012] [Accepted: 08/21/2012] [Indexed: 12/16/2022]
Abstract
Phosphatidylserine (PS) and phosphatidylethanolamine (PE) are metabolically related membrane aminophospholipids. In mammalian cells, PS is required for targeting and function of several intracellular signaling proteins. Moreover, PS is asymmetrically distributed in the plasma membrane. Although PS is highly enriched in the cytoplasmic leaflet of plasma membranes, PS exposure on the cell surface initiates blood clotting and removal of apoptotic cells. PS is synthesized in mammalian cells by two distinct PS synthases that exchange serine for choline or ethanolamine in phosphatidylcholine (PC) or PE, respectively. Targeted disruption of each PS synthase individually in mice demonstrated that neither enzyme is required for viability whereas elimination of both synthases was embryonic lethal. Thus, mammalian cells require a threshold amount of PS. PE is synthesized in mammalian cells by four different pathways, the quantitatively most important of which are the CDP-ethanolamine pathway that produces PE in the ER, and PS decarboxylation that occurs in mitochondria. PS is made in ER membranes and is imported into mitochondria for decarboxylation to PE via a domain of the ER [mitochondria-associated membranes (MAM)] that transiently associates with mitochondria. Elimination of PS decarboxylase in mice caused mitochondrial defects and embryonic lethality. Global elimination of the CDP-ethanolamine pathway was also incompatible with mouse survival. Thus, PE made by each of these pathways has independent and necessary functions. In mammals PE is a substrate for methylation to PC in the liver, a substrate for anandamide synthesis, and supplies ethanolamine for glycosylphosphatidylinositol anchors of cell-surface signaling proteins. Thus, PS and PE participate in many previously unanticipated facets of mammalian cell biology. This article is part of a Special Issue entitled Phospholipids and Phospholipid Metabolism.
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Affiliation(s)
- Jean E Vance
- Group on the Molecular and Cell Biology of Lipids and the Department of Medicine, University of Alberta, Edmonton, Canada AB T6G 2S2.
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Wriessnegger T, Sunga AJ, Cregg JM, Daum G. Identification of phosphatidylserine decarboxylases 1 and 2 fromPichia pastoris. FEMS Yeast Res 2009; 9:911-22. [DOI: 10.1111/j.1567-1364.2009.00544.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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Schuiki I, Daum G. Phosphatidylserine decarboxylases, key enzymes of lipid metabolism. IUBMB Life 2009; 61:151-62. [PMID: 19165886 DOI: 10.1002/iub.159] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Phosphatidylserine decarboxylases (PSDs) (E.C. 4.1.1.65) are enzymes which catalyze the formation of phosphatidylethanolamine (PtdEtn) by decarboxylation of phosphatidylserine (PtdSer). This enzymatic activity has been identified in both prokaryotic and eukaryotic organisms. PSDs occur as two types of proteins depending on their localization and the sequence of a conserved motif. Type I PSDs include enzymes of eukaryotic mitochondria and bacterial origin which contain the amino acid sequence LGST as a characteristic motif. Type II PSDs are found in the endomembrane system of eukaryotes and contain a typical GGST motif. These characteristic motifs are considered as autocatalytic cleavage sites where proenzymes are split into alpha- and beta-subunits. The S-residue set free by this cleavage serves as an attachment site of a pyruvoyl group which is required for the activity of the enzymes. Moreover, PSDs harbor characteristic binding sites for the substrate PtdSer. Substrate supply to eukaryotic PSDs requires lipid transport because PtdSer synthesis and decarboxylation are spatially separated. Targeting of PSDs to their proper locations requires additional intramolecular domains. Mitochondrially localized type I PSDs are directed to the inner mitochondrial membrane by N-terminal targeting sequences. Type II PSDs also contain sequences in their N-terminal extensions which might be required for subcellular targeting. Lack of PSDs causes various defects in different cell types. The physiological relevance of these findings and the central role of PSDs in lipid metabolism will be discussed in this review.
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Affiliation(s)
- Irmgard Schuiki
- Institute of Biochemistry, Graz University of Technology, Graz, Austria
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Arikketh D, Nelson R, Vance JE. Defining the importance of phosphatidylserine synthase-1 (PSS1): unexpected viability of PSS1-deficient mice. J Biol Chem 2008; 283:12888-97. [PMID: 18343815 DOI: 10.1074/jbc.m800714200] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phosphatidylserine (PS) is a quantitatively minor, but physiologically important, phospholipid in mammalian cells. PS is synthesized by two distinct base-exchange enzymes, PS synthase-1 (PSS1) and PS synthase-2 (PSS2), that are encoded by different genes. PSS1 exchanges serine for choline of phosphatidylcholine, whereas PSS2 exchanges ethanolamine of phosphatidylethanolamine for serine. We previously generated mice lacking PSS2 (Bergo, M. O., Gavino, B. J., Steenbergen, R., Sturbois, B., Parlow, A. F., Sanan, D. A., Skarnes, W. C., Vance, J. E., and Young, S. G. (2002) J. Biol. Chem. 277, 47701-47708) and found that PSS2 is not required for mouse viability. We have now generated PSS1-deficient mice. In light of the markedly impaired survival of Chinese hamster ovary cells lacking PSS1 we were surprised that PSS1-deficient mice were viable, fertile, and had a normal life span. Total serine-exchange activity (contributed by PSS1 and PSS2) in tissues of Pss1(-/-) mice was reduced by up to 85%, but except in liver, the PS content was unaltered. Despite the presumed importance of PS in the nervous system, the rate of axonal extension of PSS1-deficient neurons was normal. Intercrosses of Pss1(-/-) mice and Pss2(-/-) mice yielded mice with three disrupted Pss alleles but no double knockout mice. In Pss1(-/-)/Pss2(-/-) and Pss1(-/-)/Pss2(-/-) mice, serine-exchange activity was reduced by 65-91%, and the tissue content of PS and phosphatidylethanolamine was also decreased. We conclude that (i) elimination of either PSS1 or PSS2, but not both, is compatible with mouse viability, (ii) mice can tolerate as little as 10% of normal total serine-exchange activity, and (iii) mice survive with significantly reduced PS and phosphatidylethanolamine content.
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Affiliation(s)
- Devi Arikketh
- University of Alberta, Edmonton, Alberta T6G 2S2, Canada
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31
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Vance JE. Phosphatidylserine and phosphatidylethanolamine in mammalian cells: two metabolically related aminophospholipids. J Lipid Res 2008; 49:1377-87. [PMID: 18204094 DOI: 10.1194/jlr.r700020-jlr200] [Citation(s) in RCA: 335] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Phosphatidylserine (PS) and phosphatidylethanolamine (PE) are two aminophospholipids whose metabolism is interrelated. Both phospholipids are components of mammalian cell membranes and play important roles in biological processes such as apoptosis and cell signaling. PS is synthesized in mammalian cells by base-exchange reactions in which polar head groups of preexisting phospholipids are replaced by serine. PS synthase activity resides primarily on mitochondria-associated membranes and is encoded by two distinct genes. Studies in mice in which each gene has been individually disrupted are beginning to elucidate the importance of these two synthases for biological functions in intact animals. PE is made in mammalian cells by two completely independent major pathways. In one pathway, PS is converted into PE by the mitochondrial enzyme PS decarboxylase. In addition, PE is made via the CDP-ethanolamine pathway, in which the final reaction occurs on the endoplasmic reticulum and nuclear envelope. The relative importance of these two pathways of PE synthesis has been investigated in knockout mice. Elimination of either pathway is embryonically lethal, despite the normal activity of the other pathway. PE can also be generated from a base-exchange reaction and by the acylation of lyso-PE. Cellular levels of PS and PE are tightly regulated by the implementation of multiple compensatory mechanisms.
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Affiliation(s)
- Jean E Vance
- Group on the Molecular and Cell Biology of Lipids and Department of Medicine, University of Alberta, Edmonton, Alberta T6G 2S2, Canada.
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Steenbergen R, Nanowski TS, Beigneux A, Kulinski A, Young SG, Vance JE. Disruption of the phosphatidylserine decarboxylase gene in mice causes embryonic lethality and mitochondrial defects. J Biol Chem 2005; 280:40032-40. [PMID: 16192276 PMCID: PMC2888304 DOI: 10.1074/jbc.m506510200] [Citation(s) in RCA: 204] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Most of the phosphatidylethanolamine (PE) in mammalian cells is synthesized by two pathways, the CDP-ethanolamine pathway and the phosphatidylserine (PS) decarboxylation pathway, the final steps of which operate at spatially distinct sites, the endoplasmic reticulum and mitochondria, respectively. We investigated the importance of the mitochondrial pathway for PE synthesis in mice by generating mice lacking PS decarboxylase activity. Disruption of Pisd in mice resulted in lethality between days 8 and 10 of embryonic development. Electron microscopy of Pisd-/- embryos revealed large numbers of aberrantly shaped mitochondria. In addition, fluorescence confocal microscopy of Pisd-/- embryonic fibroblasts showed fragmented mitochondria. PS decarboxylase activity and mRNA levels in Pisd+/- tissues were approximately one-half of those in wild-type mice. However, heterozygous mice appeared normal, exhibited normal vitality, and the phospholipid composition of livers, testes, brains, and of mitochondria isolated from livers, was the same as in wild-type littermates. The amount and activity of a key enzyme of the CDP-ethanolamine pathway for PE synthesis, CTP:phosphoethanolamine cytidylyltransferase, were increased by 35-40 and 100%, respectively, in tissues of Pisd+/- mice, as judged by immunoblotting; PE synthesis from [3H]ethanolamine was correspondingly increased in hepatocytes. We conclude that the CDP-ethanolamine pathway in mice cannot substitute for a lack of PS decarboxylase during development. Moreover, elimination of PE production in mitochondria causes fragmented, misshapen mitochondria, an abnormality that likely contributes to the embryonic lethality.
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Affiliation(s)
- Rineke Steenbergen
- Canadian Institutes for Health Research Group on the Molecular and Cell Biology of Lipids and Department of Medicine, University of Alberta, Edmonton, Alberta T6G 2S2, Canada
| | - Terry S. Nanowski
- Canadian Institutes for Health Research Group on the Molecular and Cell Biology of Lipids and Department of Medicine, University of Alberta, Edmonton, Alberta T6G 2S2, Canada
| | - Anne Beigneux
- Department of Medicine/Division of Cardiology, David Geffen School of Medicine, University of California, Los Angeles, California 90095
| | - Agnes Kulinski
- Canadian Institutes for Health Research Group on the Molecular and Cell Biology of Lipids and Department of Medicine, University of Alberta, Edmonton, Alberta T6G 2S2, Canada
| | - Stephen G. Young
- Department of Medicine/Division of Cardiology, David Geffen School of Medicine, University of California, Los Angeles, California 90095
| | - Jean E. Vance
- Canadian Institutes for Health Research Group on the Molecular and Cell Biology of Lipids and Department of Medicine, University of Alberta, Edmonton, Alberta T6G 2S2, Canada
- To whom correspondence should be addressed: 332 HMRC, University of Alberta, Edmonton, AB T6G 2S2, Canada. Tel.: 780-492-7250; Fax: 780-492-3383;
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Macchioni L, Corazzi L, Nardicchi V, Mannucci R, Arcuri C, Porcellati S, Sposini T, Donato R, Goracci G. Rat Brain Cortex Mitochondria Release Group II Secretory Phospholipase A2 under Reduced Membrane Potential. J Biol Chem 2004; 279:37860-9. [PMID: 15231825 DOI: 10.1074/jbc.m303855200] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Activation of brain mitochondrial phospholipase(s) A(2) (PLA(2)) might contribute to cell damage and be involved in neurodegeneration. Despite the potential importance of the phenomenon, the number, identities, and properties of these enzymes are still unknown. Here, we demonstrate that isolated mitochondria from rat brain cortex, incubated in the absence of respiratory substrates, release a Ca(2+)-dependent PLA(2) having biochemical properties characteristic to secreted PLA(2) (sPLA(2)) and immunoreacting with the antibody raised against recombinant type IIA sPLA(2) (sPLA(2)-IIA). Under identical conditions, no release of fumarase in the extramitochondrial medium was observed. The release of sPLA(2) from mitochondria decreases when mitochondria are incubated in the presence of respiratory substrates such as ADP, malate, and pyruvate, which causes an increase of transmembrane potential determined by cytofluorimetric analysis using DiOC(6)(3) as a probe. The treatment of mitochondria with the uncoupler carbonyl cyanide 3-chlorophenylhydrazone slightly enhances sPLA(2) release. The increase of sPLA(2) specific activity after removal of mitochondrial outer membrane indicates that the enzyme is associated with mitoplasts. The mitochondrial localization of the enzyme has been confirmed by electron microscopy in U-251 astrocytoma cells and by confocal laser microscopy in the same cells and in PC-12 cells, where the structurally similar isoform type V-sPLA(2) has mainly nuclear localization. In addition to sPLA(2), mitochondria contain another phospholipase A(2) that is Ca(2+)-independent and sensitive to bromoenol lactone, associated with the outer mitochondrial membrane. We hypothesize that, under reduced respiratory rate, brain mitochondria release sPLA(2)-IIA that might contribute to cell damage.
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Affiliation(s)
- Lara Macchioni
- Department of Internal Medicine, Division of Biochemistry, University of Perugia, I-06125 Perugia, Italy
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Mozzi R, Buratta S, Goracci G. Metabolism and functions of phosphatidylserine in mammalian brain. Neurochem Res 2003; 28:195-214. [PMID: 12608694 DOI: 10.1023/a:1022412831330] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Phosphatidylserine (PtdSer) is involved in cell signaling and apoptosis. The mechanisms regulating its synthesis and degradation are still not defined. Thus, its role in these processes cannot be clearly established at molecular level. In higher eukaryotes, PtdSer is synthesized from phosphatidylethanolamine or phosphatidylcholine through the exchange of the nitrogen base with free serine. PtdSer concentration in the nervous tissue membranes varies with age, brain areas, cells, and subcellular components. At least two serine base exchange enzymes isoforms are present in brain, and their biochemical properties and regulation are still largely unknown because their activities vary with cell type and/or subcellular fraction, developmental stage, and differentiation. These peculiarities may explain the apparent contrasting reports. PtdSer cellular levels also depend on its decarboxylation to phosphatidylethanolamine and conversion to lysoPtdSer by phospholipases. Several aspects of brain PtdSer metabolism and functions seem related to the high polyunsaturated fatty acids content, particularly docosahexaenoic acid (DHA).
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Affiliation(s)
- Rita Mozzi
- Department of Internal Medicine, Division of Biochemistry, University of Perugia, Perugia, Italy
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35
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Kevala JH, Kim HY. Determination of substrate preference in phosphatidylserine decarboxylation by liquid chromatography-electrospray ionization mass spectrometry. Anal Biochem 2001; 292:130-8. [PMID: 11319827 DOI: 10.1006/abio.2001.5076] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A method has been developed to determine the substrate preference in phosphatidylserine decarboxylation (PSD), the process by which phosphatidylserine is converted to phosphatidylethanolamine (PE) in the mitochondria. The in vitro assay utilized liposomes containing deuterium-labeled PS molecular species incubated with liver and brain cortex mitochondria, and the conversion of PS to the corresponding PE species was monitored by electrospray ionization mass spectrometry in conjunction with reversed-phase liquid chromatography. Employing this approach we were able to establish for the first time that there exists a substrate preference in PSD in liver (18:0,18:1 > or = 18:0,22:6 > 18:0,20:4-PS) and brain cortex (18:0,22:6 > 18:0,18:1 > 18:0,20:4-PS). The observed PSD molecular species preference, however, did not reflect the mitochondrial PE profile, suggesting that selectivity in other processes such as de novo PE synthesis, intracellular transport of phospholipid molecules, or remodeling by deacylation-reacylation may be important contributors in maintaining a specific lipid profile in mitochondria.
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Affiliation(s)
- J H Kevala
- Section of Mass Spectrometry, Laboratory of Membrane Biochemistry and Biophysics, National Institute on Alcohol Abuse and Alcoholism, 12420 Parklawn Drive, Room 158, Rockville, Maryland 20852, USA
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36
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Camici O, Corazzi L. Phosphatidylserine translocation into brain mitochondria: involvement of a fusogenic protein associated with mitochondrial membranes. Mol Cell Biochem 1997; 175:71-80. [PMID: 9350036 DOI: 10.1023/a:1006889328983] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Data reported in the literature indicate that lipid movement between intracellular organelles can occur through contacts and close physical association of membranes (Vance, J.E. 1990. J Biol Chem 265: 7248-7256). The advantage of this mechanism is that the direct interaction of membranes provides the translocation event without the involvement of lipid-transport systems. However, pre-requisite for the functioning of this machinery is the presence of protein factors controlling membrane association and fusion. In the present work we have found that liposomes fuse to mitochondria at acidic pH and that the pre-treatment of mitochondria with pronase inhibits the fusogenic activity. Mixing of 14C-phosphatidylserine (PS) labeled liposomes with mitochondria at pH 6.0 results in the translocation of 14C-PS into mitochondria and in its decarboxylation to 14C-phosphatidylethanolamine through the PS decarboxylase activity localized on the outer surface of the inner mitochondrial membrane. Incorporation of 14C-PS is inhibited by the pre-treatment of mitochondria with pronase or with EEDQ, a reagent for the derivatization of the protonated form of carboxylic groups. These results indicate the presence of a protein associated with mitochondria which is able to trigger the fusion of liposomes to the mitochondrial membrane. A partial purification of a mitochondrial fusogenic glycoprotein is described in this work. The activity of the fusogenic protein appears to be dependent on the extent of protonation of the residual carboxylic groups and is influenced by the glucidic moiety, as demonstrated by its interaction with Concanavalin A. The purified protein is able to promote the recover of the 14C-PS import from liposomes to pronase-treated mitochondria. Therefore, the protein is candidate to be an essential component in the machinery for the mitochondrial import of PS.
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Affiliation(s)
- O Camici
- Institute of Biochemistry and Medical Chemistry, University of Perugia, Italy
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37
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Camici O, Corazzi L. Import of phosphatidylethanolamine for the assembly of rat brain mitochondrial membranes. J Membr Biol 1995; 148:169-76. [PMID: 8606365 DOI: 10.1007/bf00207272] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Mitochondria can synthesize phosphatidyl-ethanolamine (PE) through phosphatidylserine decarboxylase (PS decarboxylase) activity or can import this lipid from the endoplasmic reticulum. In this work, we studied the factors influencing the import of PE in brain mitochondria and its utilization for the assembly of mitochondrial membranes. Incubation of rat brain homogenate with [1-3H]ethanolamine resulted in the synthesis and distribution of 3H-PE to subcellular fractions. Twenty-one percent of labeled PE was recovered in purified mitochondria. The import of PE in mitochondria was studied in a reconstituted system made of microsomes (donor particles) and purified mitochondria (acceptor particles). Ca2+ and nonspecific lipid transfer protein purified from liver tissue (nsL-TP) enhanced the translocation process. 3H-PE synthesized in membrane associated to mitochondria (MAM) could also translocate to mitochondria in the reconstituted system. Exposure of mitochondria to trinitrobenzensulfonic acid (TNBS) resulted in the reaction of more than 60% of 3H-PE imported from endoplasmic reticulum and of about 25% of 14C-PE produced in mitochondria by decarboxylation of 14C-PS. Moreover, the removal of the outer mitochondrial membrane by digitonin treatment, resulted in the loss of 3H-PE, but not 14C-PE. These results indicate that labeled PE imported in mitochondria is mainly localized in the outer mitochondrial membrane, whereas PE produced by PS decarboxylase activity is confined to the inner mitochondrial membrane. Phospholipase C hydrolyzed 25-30% of both PE radioactivity and mass of the outer mitochondrial membrane indicating an asymmetrical distribution of this lipid across the membrane.
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Affiliation(s)
- O Camici
- Institute of Biochemistry and Medical Chemistry, University of Perugia, Italy
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38
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Moreau P, Cassagne C. Phospholipid trafficking and membrane biogenesis. BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1197:257-90. [PMID: 7819268 DOI: 10.1016/0304-4157(94)90010-8] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- P Moreau
- URA 1811 CNRS, IBGC, University of Bordeaux II, France
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Jasińska R, Zborowski J, Somerharju P. Intramitochondrial distribution and transport of phosphatidylserine and its decarboxylation product, phosphatidylethanolamine. Application of pyrene-labeled species. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1152:161-70. [PMID: 8399295 DOI: 10.1016/0005-2736(93)90243-s] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
To investigate the mechanism of intramitochondrial translocation of phosphatidylserine and its decarboxylation product, phosphatidylethanolamine, the distribution of these lipids between the outer (OM) and inner (IM) mitochondrial membranes, as well as their transversal and lateral distribution in OM were studied. Fluorescent, pyrenyl derivatives of phosphatidylserine (PyrxPS) and phosphatidylethanolamine (PyrxPE) species were employed because they allow: (i), direct monitoring of PS (and PE) loading to the mitochondria; (ii) assay of PS decarboxylation by high-performance liquid chromatography with fluorescence detection and (iii), determination of the lateral distributions of PS and PE within the mitochondrial membranes. All PyrxPS species tested were efficiently decarboxylated by the solubilized decarboxylase and thus the distribution of the endogenous PE could be also studied. When the PyrxPS species were loaded to isolated mitochondria very little, if any, of the loaded PyrxPS or of the PyrxPE product was found in IM independent of the time and temperature of incubation, strongly suggesting that these lipids either never enter IM or their residence there is only transient. When mitochondria preloaded with Pyr4PS were incubated with an excess of acceptor vesicles in the presence of the lipid transfer protein, 80% of Pyr4PS and 30-40% of the Pyr4PE product were transported to the acceptor vesicles, indicating that at least corresponding fractions of these lipid were located in, or were in rapid equilibrium with the outer leaflet of OM. Since the decarboxylase is located in the inner membrane, these results signify that both PS and PE must be able to move readily across OM. Determination of the excimer to monomer ratio as the function of pyrenyl lipid concentration in mitochondria (i.e., OM) gave parallel results for PyrxPS and -PE species suggesting the lateral distribution of PS and PE in OM is similar and thus there is no specific enrichment of PS to the contact sites. To investigate the mechanism of PS transport from the outer leaflet to the decarboxylation site, the influence of PyrxPS hydrophobicity, i.e., pyrenylacyl chain length, on the rate of decarboxylation was determined. The variation of the length of the pyrenyl acyl chain from 4 to 12 carbons did not significantly affect the rate of PyrxPS decarboxylation in intact mitochondria, indicating that the transport of PS from the outer leaflet of OM to the site of decarboxylation takes place by lateral diffusion rather than by spontaneous or protein-mediated transport. The implications of these findings on the mechanism of intramitochondrial transport of PS and PE are discussed in terms of alternative models.
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Affiliation(s)
- R Jasińska
- Department of Cellular Biochemistry, Nencki Institute on Experimental Biology, Warsaw, Poland
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41
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Corazzi L, Pistolesi R, Carlini E, Arienti G. Transport of phosphatidylserine from microsomes to the inner mitochondrial membrane in brain tissue. J Neurochem 1993; 60:50-6. [PMID: 8417166 DOI: 10.1111/j.1471-4159.1993.tb05821.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Phosphatidylserine was labeled by incubating rat brain homogenates with [3-14C]serine in the presence of Ca2+ (base-exchange conditions). Some labeled phosphatidylethanolamine also forms, in spite of the inhibition of Ca2+ on phosphatidylserine decarboxylase. Phosphatidylserine labeling and decarboxylation also occur on incubating a mixture of purified mitochondria and microsomes, suggesting that no soluble factors are necessary for the synthesis and the decarboxylation of phosphatidylserine. Ca2+ favors the transfer of phosphatidylserine from microsomes (where it forms) to mitochondria (where it is decarboxylated). The specific radioactivity of the phosphatidylserine transferred to mitochondria is higher than that of microsomal phosphatidylserine. This finding supports the hypothesis that the lipid is compartmentalized in microsomes and that radioactive, newly synthesized phosphatidylserine is much better exported than the bulk of microsomal phospholipid.
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Affiliation(s)
- L Corazzi
- Istituto di Biochimica e Chimica Medica, Facoltà di Medicina e Chirurgia, Perugia, Italy
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42
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Hovius R, Faber B, Brigot B, Nicolay K, de Kruijff B. On the mechanism of the mitochondrial decarboxylation of phosphatidylserine. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)41851-0] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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43
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Overmeyer JH, Waechter CJ. Regulation of phosphatidylserine decarboxylase in Saccharomyces cerevisiae by inositol and choline: kinetics of repression and derepression. Arch Biochem Biophys 1991; 290:511-6. [PMID: 1929418 DOI: 10.1016/0003-9861(91)90574-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The biosynthesis of phosphatidylserine (PS) and its conversion to phosphatidylcholine (PC) are regulated coordinately by inositol and choline in Saccharomyces cerevisiae (G. M. Carman and S. A. Henry, 1989, Annu. Rev. Biochem. 58, 635-669). In this study, PS decarboxylase activity is shown to be partially repressed when inositol is added to the medium of cells in the log phase of growth, and the extent of repression is augmented by the inclusion of choline, but not ethanolamine. The kinetics of repression and derepression of PS decarboxylase, PS synthase, and phospholipid N-methyltransferase (PNMT) activities, as regulatory responses to the availability of exogenous inositol and choline, have been characterized. When inositol was added to the medium of cell cultures growing exponentially, the three biosynthetic enzyme activities reached an intermediate level of repression (50-85% of control) within 60 min. After the addition of the combination of inositol and choline, PS decarboxylase, PS synthase, and PNMT activities decreased to the intermediate levels of repression in 60 min and were subsequently reduced to 15-40% of control values during a later stage of regulation (2-3 h). In a derepression study, the three enzyme activities remained relatively stable for approximately 60 min following the removal of choline and/or inositol from the growth medium, but the specific activities of PS decarboxylase, PS synthase, and PNMT increased to maximally derepressed levels within 2-3 h. The induction of the three biosynthetic activities was blocked by cycloheximide, but not by chloramphenicol. In summary, the level of PS decarboxylase activity in S. cerevisiae is partially and reversibly suppressed by inositol and further diminished by the combination of inositol and choline. The biphasic kinetics of repression by inositol and choline suggest that the effect of choline is dependent on earlier events mediated by inositol and possibly involves a separate regulatory factor(s).
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Affiliation(s)
- J H Overmeyer
- Department of Biochemistry, University of Kentucky College of Medicine, A. B. Chandler Medical Center, Lexington 40536
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Percy AK, Moore JF, Plishker GA, Waymire JC. Phosphoglyceride biosynthesis in bovine adrenal chromaffin cells. Neurochem Res 1991; 16:505-11. [PMID: 1656294 DOI: 10.1007/bf00965573] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Cultured adrenal chromaffin cells, representing a virtually homogeneous population of neuronal elements, have been utilized to examine the final enzymes in the formation of phosphatidylcholine (PC) and phosphatidylethanolamine (PE), namely, choline phosphotransferase, ethanolaminephosphotransferase, and the N-methyltransferases in the sequential methylation of PE to PC. Each enzyme has been characterized extensively in terms of substrate requirements, pH optima, detergent and cation effects, and response to inhibitors revealing properties very similar to those in other neural preparations. The respective activities are stable for up to two weeks of adrenal chromaffin cell culture suggesting that this system is a suitable model for examining the relative roles and the regulation of each pathway in PC formation.
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Affiliation(s)
- A K Percy
- Baylor College of Medicine, Dept. of Pediatrics (Neurology), Houston, TX 77030
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Overmeyer JH, Waechter CJ. Assay for phosphatidylserine decarboxylase utilizing DEAE-cellulose column chromatography. Anal Biochem 1989; 182:452-6. [PMID: 2692476 DOI: 10.1016/0003-2697(89)90622-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
A simple assay for phosphatidylserine decarboxylase is described. Following incubation of a mitochondrial fraction from Saccharomyces cerevisiae with purified, exogenous phosphatidyl[3H]serine, the lipid extract is applied to a small DEAE-cellulose column equilibrated in CHCI3-CH3OH (1:1). The unreacted substrate, phosphatidyl[3H]serine, is quantitatively bound by the ion-exchange column while the product, phosphatidyl[3H]ethanolamine, is eluted by sequential washing with CHCI3-CH3OH (1:1) and CH3OH. The organic solvents are evaporated, and the amount of radiolabeled phosphatidyl[3H]ethanolamine formed by enzymatic decarboxylation is determined by liquid scintillation spectrometry. The reliability of this assay was established by showing that several enzymatic properties of the yeast enzyme, defined by the new assay, were essentially identical to the properties characterized by a more tedious paper chromatographic assay described previously. Virtually identical rates of enzymatic decarboxylation of phosphatidyl[3H]serine were also obtained for mitochondrial fractions from pig brain and rat liver when the activities were compared by the column and paper chromatographic methods.
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Affiliation(s)
- J H Overmeyer
- Department of Biochemistry, University of Kentucky College of Medicine, A.B. Chandler Medical Center, Lexington 40536
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Sandri G, Siagri M, Panfili E. Influence of Ca2+ on the isolation from rat brain mitochondria of a fraction enriched of boundary membrane contact sites. Cell Calcium 1988; 9:159-65. [PMID: 3191526 DOI: 10.1016/0143-4160(88)90020-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Data have been obtained suggesting that the complex porin-hexokinase of brain mitochondria may be related to the contact sites between the outer and inner membrane. In the attempt to isolate from brain mitochondria the inner and outer membranes and the boundary membrane contacts, a procedure was developed based on swelling and shrinking of the organelles, followed by sonication and reverse discontinuous density gradient centrifugation. Three fractions were obtained by this technique, which were identified by measuring the relative specific activities of marker enzymes, namely succinate-cytochrome c reductase; NADH-cytochrome c reductase (rotenone insensitive); hexokinase and glutathione transferase, for the inner and outer membranes and contact sites, respectively. The fraction which contains the contact sites is characterized by the highest specific activity of hexokinase and glutathione transferase and by the highest calcium binding capacity; physiological concentrations of this cation produces a sharper separation of this fraction. Results indicate that both the porin-hexokinase gating system of the outer membrane and the calcium transporting complex of the inner membrane are present in the fraction which contains the contact sites.
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Affiliation(s)
- G Sandri
- Dipartimento di Biochimica, Università degli Studi, Trieste, Italy
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Abstract
To probe the activities of various pathways of lipid metabolism in peripheral nerve, six phospholipid-directed precursors were individually injected into the exposed sciatic nerves of adult mice, and their incorporation into phospholipids and proteins was studied over a 2-week period. Tritiated choline, inositol, ethanolamine, serine, and glycerol were mainly used in phospholipid synthesis; in contrast, methyl-labeled methionine was primarily incorporated into protein. Phosphatidylcholine was the main lipid formed from tritiated choline, glycerol, and methionine precursors. Phosphatidylserine, phosphatidylethanolamine, and phosphatidylinositol were the main lipids formed from serine, ethanolamine, and inositol, respectively. With time there was a shift in label among phospholipids, with higher proportions of choline appearing in sphingomyelin, glycerol in phosphatidylserine, ethanolamine in phosphatidylethanolamine (plasmalogen), and inositol in polyphosphoinositides, especially phosphatidylinositol 4,5-bisphosphate. We suggest that the delay in formation of these phospholipids, which are concentrated in peripheral nerve myelin, may, at least in part, be due to their formation at a site(s) distant from the sites where the bulk of Schwann cell lipids are made. We propose that separating the synthesis of these myelin-destined lipids to near the Schwann cell's plasma membrane would facilitate their concentration in peripheral nerve myelin sheaths. At earlier labeling times, ethanolamine and glycerol were more actively incorporated into phosphatidylcholine and phosphatidylinositol, respectively, than later. The transient labeling of these phospholipids may reflect some unique role in peripheral nerve function.
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Rietveld A, de Kruijff B. Phospholipids as a possible instrument for translocation of nascent proteins across biological membranes. Biosci Rep 1986; 6:775-82. [PMID: 3028524 DOI: 10.1007/bf01117100] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The interaction of phospholipids with precursor proteins, particularly with the mitochondrial precursor protein apocytochrome c is reviewed and integrated with other aspects of protein insertion and translocation, leading to a model for (apo)cytochrome c import into mitochondria, in which phospholipids play a dominant role.
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Abstract
In adult rats, a significant portion of brain ethanolamine glycerophospholipids are synthesized by a pathway involving phosphatidylserine decarboxylase, a mitochondrial enzyme. We have now examined whether this enzyme plays a particularly prominent role during development. Activities for both phosphatidylserine decarboxylase and succinate dehydrogenase (another mitochondrial enzyme) were determined in brain homogenates from rats 5 days of age to adulthood. Succinate dehydrogenase activity, expressed on a per unit brain protein basis, increased markedly during development. This pattern has been reported previously and is as expected from the postnatal increase in oxidative metabolism. In contrast, phosphatidylserine decarboxylase activity decreased 40% from 5 to 30 days of age. The apparent Km for brain phosphatidylserine decarboxylase was 85 microM in both young (8- and 20-day-old) and adult animals. Parallel studies in vivo were carried out to determine the contribution of the phosphatidylserine decarboxylase pathway, relative to pathways utilizing ethanolamine directly, to the synthesis of brain ethanolamine glycerophospholipids. Animals were injected intracranially with a mixture of L-[G-3H]serine and [2-14C]ethanolamine and incorporation into the base moieties of the phospholipids determined. The 3H/14C ratio of ethanolamine glycerophospholipids decreased about 50% during development. Our studies in vitro and in vivo both suggest that phosphatidylserine decarboxylase plays a significant role in the synthesis of brain ethanolamine glycerophospholipids at all ages, although it is relatively more prominent early in development.
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Kuchler K, Daum G, Paltauf F. Subcellular and submitochondrial localization of phospholipid-synthesizing enzymes in Saccharomyces cerevisiae. J Bacteriol 1986; 165:901-10. [PMID: 3005242 PMCID: PMC214514 DOI: 10.1128/jb.165.3.901-910.1986] [Citation(s) in RCA: 180] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Using highly enriched membrane preparations from lactate-grown Saccharomyces cerevisiae cells, the subcellular and submitochondrial location of eight enzymes involved in the biosynthesis of phospholipids was determined. Phosphatidylserine decarboxylase and phosphatidylglycerolphosphate synthase were localized exclusively in the inner mitochondrial membrane, while phosphatidylethanolamine methyltransferase activity was confined to microsomal fractions. The other five enzymes tested in this study were common both to the outer mitochondrial membrane and to microsomes. The transmembrane orientation of the mitochondrial enzymes was investigated by protease digestion of intact mitochondria and of outside-out sealed vesicles of the outer mitochondrial membrane. Glycerolphosphate acyltransferase, phosphatidylinositol synthase, and phosphatidylserine synthase were exposed at the cytosolic surface of the outer mitochondrial membrane. Cholinephosphotransferase was apparently located at the inner aspect or within the outer mitochondrial membrane. Phosphatidate cytidylyltransferase was localized in the endoplasmic reticulum, on the cytoplasmic side of the outer mitochondrial membrane, and in the inner mitochondrial membrane. Inner membrane activity of this enzyme constituted 80% of total mitochondrial activity; inactivation by trypsin digestion was observed only after preincubation of membranes with detergent (0.1% Triton X-100). Total activity of those enzymes that are common to mitochondria and the endoplasmic reticulum was about equally distributed between the two organelles. Data concerning susceptibility to various inhibitors, heat sensitivity, and the pH optima indicate that there is a close similarity of the mitochondrial and microsomal enzymes that catalyze the same reaction.
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