1
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Fujimoto T. Nuclear lipid droplet: Guardian of nuclear membrane lipid homeostasis? Curr Opin Cell Biol 2024; 88:102370. [PMID: 38744005 DOI: 10.1016/j.ceb.2024.102370] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2024] [Accepted: 04/22/2024] [Indexed: 05/16/2024]
Abstract
Lipid droplets (LDs) are cytoplasmic organelles, but they are also found within the nucleus in small numbers. Nuclear LDs that form at the inner nuclear membrane (INM) often increase in response to perturbation in phosphatidic acid (PA) and/or diacylglycerol (DAG), both implicated in various INM functions. Nuclear LDs also increase upon downregulation of seipin, a protein that can trap PA and DAG in the endoplasmic reticulum. Notably, both PA and DAG appear to be more densely distributed on the surface of nuclear LDs than in the INM. I propose that nuclear LDs play a role in regulating the PA and DAG level in the INM, thereby contributing to the lipid homeostasis in this compartment.
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Affiliation(s)
- Toyoshi Fujimoto
- Laboratory of Molecular Cell Biology, Research Institute for Diseases of Old Age, Juntendo University Graduate School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan. mailto:
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2
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Lee S, Carrasquillo Rodríguez JW, Merta H, Bahmanyar S. A membrane-sensing mechanism links lipid metabolism to protein degradation at the nuclear envelope. J Cell Biol 2023; 222:e202304026. [PMID: 37382667 PMCID: PMC10309186 DOI: 10.1083/jcb.202304026] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Revised: 05/22/2023] [Accepted: 06/02/2023] [Indexed: 06/30/2023] Open
Abstract
Lipid composition determines organelle identity; however, whether the lipid composition of the inner nuclear membrane (INM) domain of the ER contributes to its identity is not known. Here, we show that the INM lipid environment of animal cells is under local control by CTDNEP1, the master regulator of the phosphatidic acid phosphatase lipin 1. Loss of CTDNEP1 reduces association of an INM-specific diacylglycerol (DAG) biosensor and results in a decreased percentage of polyunsaturated containing DAG species. Alterations in DAG metabolism impact the levels of the resident INM protein Sun2, which is under local proteasomal regulation. We identify a lipid-binding amphipathic helix (AH) in the nucleoplasmic domain of Sun2 that prefers membrane packing defects. INM dissociation of the Sun2 AH is linked to its proteasomal degradation. We suggest that direct lipid-protein interactions contribute to sculpting the INM proteome and that INM identity is adaptable to lipid metabolism, which has broad implications on disease mechanisms associated with the nuclear envelope.
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Affiliation(s)
- Shoken Lee
- Department of Molecular Cellular and Developmental Biology, Yale University, New Haven, CT, USA
| | | | - Holly Merta
- Department of Molecular Cellular and Developmental Biology, Yale University, New Haven, CT, USA
| | - Shirin Bahmanyar
- Department of Molecular Cellular and Developmental Biology, Yale University, New Haven, CT, USA
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3
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Sarmento MJ, Llorente A, Petan T, Khnykin D, Popa I, Nikolac Perkovic M, Konjevod M, Jaganjac M. The expanding organelle lipidomes: current knowledge and challenges. Cell Mol Life Sci 2023; 80:237. [PMID: 37530856 PMCID: PMC10397142 DOI: 10.1007/s00018-023-04889-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 06/13/2023] [Accepted: 07/19/2023] [Indexed: 08/03/2023]
Abstract
Lipids in cell membranes and subcellular compartments play essential roles in numerous cellular processes, such as energy production, cell signaling and inflammation. A specific organelle lipidome is characterized by lipid synthesis and metabolism, intracellular trafficking, and lipid homeostasis in the organelle. Over the years, considerable effort has been directed to the identification of the lipid fingerprints of cellular organelles. However, these fingerprints are not fully characterized due to the large variety and structural complexity of lipids and the great variability in the abundance of different lipid species. The process becomes even more challenging when considering that the lipidome differs in health and disease contexts. This review summarizes the information available on the lipid composition of mammalian cell organelles, particularly the lipidome of the nucleus, mitochondrion, endoplasmic reticulum, Golgi apparatus, plasma membrane and organelles in the endocytic pathway. The lipid compositions of extracellular vesicles and lamellar bodies are also described. In addition, several examples of subcellular lipidome dynamics under physiological and pathological conditions are presented. Finally, challenges in mapping organelle lipidomes are discussed.
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Affiliation(s)
- Maria J Sarmento
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, 1649-028, Lisbon, Portugal
| | - Alicia Llorente
- Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, 0379, Oslo, Norway
- Department for Mechanical, Electronics and Chemical Engineering, Oslo Metropolitan University, 0167, Oslo, Norway
- Faculty of Medicine, Centre for Cancer Cell Reprogramming, University of Oslo, Montebello, 0379, Oslo, Norway
| | - Toni Petan
- Department of Molecular and Biomedical Sciences, Jožef Stefan Institute, Ljubljana, Slovenia
| | - Denis Khnykin
- Department of Pathology, Oslo University Hospital, Oslo, Norway
| | - Iuliana Popa
- Pharmacy Department, Bâtiment Henri Moissan, University Paris-Saclay, 17 Avenue des Sciences, 91400, Orsay, France
| | | | - Marcela Konjevod
- Division of Molecular Medicine, Ruder Boskovic Institute, 10000, Zagreb, Croatia
| | - Morana Jaganjac
- Division of Molecular Medicine, Ruder Boskovic Institute, 10000, Zagreb, Croatia.
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4
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Carew NT, Schmidt HM, Yuan S, Galley JC, Hall R, Altmann HM, Hahn SA, Miller MP, Wood KC, Gabris B, Stapleton MC, Hartwick S, Fazzari M, Wu YL, Trebak M, Kaufman BA, McTiernan CF, Schopfer FJ, Navas P, Thibodeau PH, McNamara DM, Salama G, Straub AC. Loss of cardiomyocyte CYB5R3 impairs redox equilibrium and causes sudden cardiac death. J Clin Invest 2022; 132:e147120. [PMID: 36106636 PMCID: PMC9479700 DOI: 10.1172/jci147120] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Accepted: 07/19/2022] [Indexed: 01/04/2023] Open
Abstract
Sudden cardiac death (SCD) in patients with heart failure (HF) is allied with an imbalance in reduction and oxidation (redox) signaling in cardiomyocytes; however, the basic pathways and mechanisms governing redox homeostasis in cardiomyocytes are not fully understood. Here, we show that cytochrome b5 reductase 3 (CYB5R3), an enzyme known to regulate redox signaling in erythrocytes and vascular cells, is essential for cardiomyocyte function. Using a conditional cardiomyocyte-specific CYB5R3-knockout mouse, we discovered that deletion of CYB5R3 in male, but not female, adult cardiomyocytes causes cardiac hypertrophy, bradycardia, and SCD. The increase in SCD in CYB5R3-KO mice is associated with calcium mishandling, ventricular fibrillation, and cardiomyocyte hypertrophy. Molecular studies reveal that CYB5R3-KO hearts display decreased adenosine triphosphate (ATP), increased oxidative stress, suppressed coenzyme Q levels, and hemoprotein dysregulation. Finally, from a translational perspective, we reveal that the high-frequency missense genetic variant rs1800457, which translates into a CYB5R3 T117S partial loss-of-function protein, associates with decreased event-free survival (~20%) in Black persons with HF with reduced ejection fraction (HFrEF). Together, these studies reveal a crucial role for CYB5R3 in cardiomyocyte redox biology and identify a genetic biomarker for persons of African ancestry that may potentially increase the risk of death from HFrEF.
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Affiliation(s)
- Nolan T. Carew
- Heart, Lung, Blood and Vascular Medicine Institute
- Department of Pharmacology and Chemical Biology
| | - Heidi M. Schmidt
- Heart, Lung, Blood and Vascular Medicine Institute
- Department of Pharmacology and Chemical Biology
| | - Shuai Yuan
- Heart, Lung, Blood and Vascular Medicine Institute
| | - Joseph C. Galley
- Heart, Lung, Blood and Vascular Medicine Institute
- Department of Pharmacology and Chemical Biology
| | - Robert Hall
- Heart, Lung, Blood and Vascular Medicine Institute
- Department of Pharmacology and Chemical Biology
| | | | | | | | - Katherine C. Wood
- Heart, Lung, Blood and Vascular Medicine Institute
- Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, and
| | - Bethann Gabris
- Division of Cardiology, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Margaret C. Stapleton
- Department of Developmental Biology and Rangos Research Center Animal Imaging Core, Children’s Hospital of Pittsburgh, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Sean Hartwick
- Department of Developmental Biology and Rangos Research Center Animal Imaging Core, Children’s Hospital of Pittsburgh, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | | | - Yijen L. Wu
- Department of Developmental Biology and Rangos Research Center Animal Imaging Core, Children’s Hospital of Pittsburgh, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Mohamed Trebak
- Heart, Lung, Blood and Vascular Medicine Institute
- Department of Pharmacology and Chemical Biology
| | - Brett A. Kaufman
- Heart, Lung, Blood and Vascular Medicine Institute
- Division of Cardiology, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Charles F. McTiernan
- Heart, Lung, Blood and Vascular Medicine Institute
- Division of Cardiology, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Francisco J. Schopfer
- Heart, Lung, Blood and Vascular Medicine Institute
- Department of Pharmacology and Chemical Biology
| | - Placido Navas
- Andalusian Center for Developmental Biology and Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Instituto de Salud Carlos III, Universidad Pablo de Olavide-CSIC-JA, Sevilla, Spain
| | | | - Dennis M. McNamara
- Division of Cardiology, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Guy Salama
- Heart, Lung, Blood and Vascular Medicine Institute
- Division of Cardiology, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Adam C. Straub
- Heart, Lung, Blood and Vascular Medicine Institute
- Department of Pharmacology and Chemical Biology
- Center for Microvascular Research, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
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5
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Ramírez-Nuñez O, Jové M, Torres P, Sol J, Fontdevila L, Romero-Guevara R, Andrés-Benito P, Ayala V, Rossi C, Boada J, Povedano M, Ferrer I, Pamplona R, Portero-Otin M. Nuclear lipidome is altered in amyotrophic lateral sclerosis: A pilot study. J Neurochem 2021; 158:482-499. [PMID: 33905537 DOI: 10.1111/jnc.15373] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Revised: 03/28/2021] [Accepted: 04/12/2021] [Indexed: 12/13/2022]
Abstract
Nucleocytosolic transport, a membrane process, is impaired in motor neurons in amyotrophic lateral sclerosis (ALS). This study analyzes the nuclear lipidome in motor neurons in ALS and examines molecular pathways linked to the major lipid alterations. Nuclei were obtained from the frozen anterior horn of the lumbar spinal cord of ALS patients and age-matched controls. Lipidomic profiles of this subcellular fraction were obtained using liquid chromatography and mass spectrometry. We validated the mechanisms behind presumable lipidomic changes by exploring ALS surrogate models including human motor neurons (derived from ALS lines and controls) subjected to oxidative stress, the hSOD-G93A transgenic mice, and samples from an independent cohort of ALS patients. Among the differential lipid species, we noted 41 potential identities, mostly belonging to phospholipids (particularly ether phospholipids, as plasmalogens), as well as diacylglycerols and triacylglycerides. Decreased expression of alkyldihydroxyacetonephosphate synthase (AGPS)-a critical peroxisomal enzyme in plasmalogen synthesis-is found in motor neuron disease models; this occurs in parallel with an increase in the expression of sterol carrier protein 2 (SCP2) mRNA in ALS and Scp2 levels in G93A transgenic mice. Further, we identified diminished expression of diacylglycerol-related enzymes, such as phospholipase C βI (PLCβI) and protein kinase CβII (PKCβII), linked to diacylglycerol metabolism. Finally, lipid droplets were recognized in the nuclei, supporting the identification of triacylglycerides as differential lipids. Our results point to the potentially pathogenic role of altered composition of nuclear membrane lipids and lipids in the nucleoplasm in the anterior horn of the spinal cord in ALS. Overall, these data support the usefulness of subcellular lipidomics applied to neurodegenerative diseases.
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Affiliation(s)
- Omar Ramírez-Nuñez
- Department of Experimental Medicine, School of Medicine, IRBLleida-UdL, Lleida, Spain
| | - Mariona Jové
- Department of Experimental Medicine, School of Medicine, IRBLleida-UdL, Lleida, Spain
| | - Pascual Torres
- Department of Experimental Medicine, School of Medicine, IRBLleida-UdL, Lleida, Spain
| | - Joaquim Sol
- Department of Experimental Medicine, School of Medicine, IRBLleida-UdL, Lleida, Spain.,Institut Català de la Salut, Lleida, Spain.,Research Support Unit Lleida, Fundació Institut Universitari per a la recerca a l'Atenció Primària de Salut Jordi Gol i Gurina (IDIAPJGol), Lleida, Spain
| | - Laia Fontdevila
- Department of Experimental Medicine, School of Medicine, IRBLleida-UdL, Lleida, Spain
| | | | - Pol Andrés-Benito
- Departament of Pathology and Experimental Therapeutics, Hospital Universitari de Bellvitge, IDIBELL, Universitat de Barcelona, Hospitalet de Llobregat, Spain.,CIBERNED (Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas), Instituto Carlos III, Barcelona, Spain
| | - Victòria Ayala
- Department of Experimental Medicine, School of Medicine, IRBLleida-UdL, Lleida, Spain
| | - Chiara Rossi
- Department of Experimental Medicine, School of Medicine, IRBLleida-UdL, Lleida, Spain
| | - Jordi Boada
- Department of Experimental Medicine, School of Medicine, IRBLleida-UdL, Lleida, Spain
| | - Mònica Povedano
- Neurology Service, Hospital Universitari de Bellvitge, Barcelona, Spain
| | - Isidro Ferrer
- Departament of Pathology and Experimental Therapeutics, Hospital Universitari de Bellvitge, IDIBELL, Universitat de Barcelona, Hospitalet de Llobregat, Spain.,CIBERNED (Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas), Instituto Carlos III, Barcelona, Spain
| | - Reinald Pamplona
- Department of Experimental Medicine, School of Medicine, IRBLleida-UdL, Lleida, Spain
| | - Manuel Portero-Otin
- Department of Experimental Medicine, School of Medicine, IRBLleida-UdL, Lleida, Spain
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6
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Tomczyk MM, Dolinsky VW. The Cardiac Lipidome in Models of Cardiovascular Disease. Metabolites 2020; 10:E254. [PMID: 32560541 PMCID: PMC7344916 DOI: 10.3390/metabo10060254] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Revised: 06/11/2020] [Accepted: 06/11/2020] [Indexed: 12/19/2022] Open
Abstract
Cardiovascular disease (CVD) is the leading cause of death worldwide. There are numerous factors involved in the development of CVD. Among these, lipids have an important role in maintaining the myocardial cell structure as well as cardiac function. Fatty acids (FA) are utilized for energy, but also contribute to the pathogenesis of CVD and heart failure. Advances in mass spectrometry methods have enabled the comprehensive analysis of a plethora of lipid species from a single sample comprised of a heterogeneous population of lipid molecules. Determining cardiac lipid alterations in different models of CVD identifies novel biomarkers as well as reveals molecular mechanisms that underlie disease development and progression. This information could inform the development of novel therapeutics in the treatment of CVD. Herein, we provide a review of recent studies of cardiac lipid profiles in myocardial infarction, obesity, and diabetic and dilated cardiomyopathy models of CVD by methods of mass spectrometry analysis.
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Affiliation(s)
- Mateusz M. Tomczyk
- Diabetes Research Envisioned and Accomplished in Manitoba (DREAM) Theme of the Children’s Hospital Research Institute of Manitoba, 715 McDermot Avenue, Winnipeg, MB R3E 3P4, Canada;
- Department of Pharmacology and Therapeutics, University of Manitoba, Winnipeg, MB R3E 0T6, Canada
- Rady Faculty of Health Science, College of Medicine, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
| | - Vernon W. Dolinsky
- Diabetes Research Envisioned and Accomplished in Manitoba (DREAM) Theme of the Children’s Hospital Research Institute of Manitoba, 715 McDermot Avenue, Winnipeg, MB R3E 3P4, Canada;
- Department of Pharmacology and Therapeutics, University of Manitoba, Winnipeg, MB R3E 0T6, Canada
- Rady Faculty of Health Science, College of Medicine, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
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7
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Ghosh SS, Krieg R, Massey HD, Sica DA, Fakhry I, Ghosh S, Gehr TWB. Curcumin and enalapril ameliorate renal failure by antagonizing inflammation in 5/6 nephrectomized rats: role of phospholipase and cyclooxygenase. Am J Physiol Renal Physiol 2011; 302:F439-54. [PMID: 22031851 DOI: 10.1152/ajprenal.00356.2010] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Previously, we showed that curcumin prevents chronic kidney disease (CKD) development in ⅚ nephrectomized (Nx) rats when given within 1 wk after Nx (Ghosh SS, Massey HD, Krieg R, Fazelbhoy ZA, Ghosh S, Sica DA, Fakhry I, Gehr TW. Am J Physiol Renal Physiol 296: F1146-F1157, 2009). To better mimic the scenario for renal disease in humans, we began curcumin and enalapril therapy when proteinuria was already established. We hypothesized that curcumin, by blocking the inflammatory mediators TNF-α and IL-1β, could also reduce cyclooxygenase (COX) and phospholipase expression in the kidney. Nx animals were divided into untreated Nx, curcumin-treated, and enalapril-treated groups. Curcumin (75 mg/kg) and enalapril (10 mg/kg) were administered for 10 wk. Renal dysfunction in the Nx group, as evidenced by elevated blood urea nitrogen, plasma creatinine, proteinuria, segmental sclerosis, and tubular dilatation, was comparably reduced by curcumin and enalapril, with only enalapril significantly lowering blood pressure. Compared with controls, Nx animals had higher plasma/kidney TNF-α and IL-1β, which were reduced by curcumin and enalapril treatment. Nx animals had significantly elevated kidney levels of cytosolic PLA(2), calcium-independent intracellular PLA(2), COX 1, and COX 2, which were comparably reduced by curcumin and enalapril. Studies in mesangial cells and macrophages were carried out to establish that the in vivo increase in PLA(2) and COX were mediated by TNF-α and IL-1β and that curcumin, by antagonizing the cytokines, could significantly reduce both PLA(2) and COX. We conclude that curcumin ameliorates CKD by blocking inflammatory signals even if it is given at a later stage of the disease.
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Affiliation(s)
- S S Ghosh
- Virginia Commonwealth Univ., Dept. of Internal Medicine/Nephrology, 1101 E. Marshall St., Sanger Hall, Rm. 8-059, Richmond, VA 23298, USA.
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8
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Liepinsh E, Skapare E, Svalbe B, Makrecka M, Cirule H, Dambrova M. Anti-diabetic effects of mildronate alone or in combination with metformin in obese Zucker rats. Eur J Pharmacol 2011; 658:277-83. [PMID: 21371472 DOI: 10.1016/j.ejphar.2011.02.019] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2010] [Revised: 01/28/2011] [Accepted: 02/17/2011] [Indexed: 01/25/2023]
Abstract
Mildronate is a cardioprotective drug, the mechanism of action of which is based on the regulation of l-carnitine concentration. We studied the metabolic effects of treatment with mildronate, metformin and a combination of the two in the Zucker rat model of obesity and impaired glucose tolerance. Zucker rats were p.o. treated daily with mildronate (200mg/kg), metformin (300 mg/kg), and a combination of both drugs for 4 weeks. Weight gain and plasma metabolites reflecting glucose metabolism were measured. The expression of peroxisome proliferator-activated receptor (PPAR)-α and PPAR-γ and target genes was measured in rat heart and liver tissues. Each treatment decreased the blood glucose concentration during the fed and fasted states by 1 to 2 mmol/l. Treatment with mildronate and metformin decreased the plasma insulin concentration by 31 and 29%, respectively, while the combination of both drugs significantly reduced fed insulin concentration by about 47%. Mildronate treatment increased the expression of PPAR-α in the heart tissue and PPAR-γ in the heart and liver tissues. In addition, treatment increased the expression of PPAR target genes in the heart, but not in the liver tissue. In contrast to monotherapy, treatment with the combination of mildronate and metformin significantly decreased weight gain by 19% and did not affect food intake. In conclusion, our results demonstrate that mildronate, an inhibitor of l-carnitine biosynthesis, improves adaptation to hyperglycemia- and hyperlipidemia-induced metabolic disturbances and increases PPAR-α activity.
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9
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Robichaud JC, van der Veen JN, Yao Z, Trigatti B, Vance DE. Hepatic uptake and metabolism of phosphatidylcholine associated with high density lipoproteins. Biochim Biophys Acta Gen Subj 2009; 1790:538-51. [PMID: 19250958 DOI: 10.1016/j.bbagen.2009.02.010] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2008] [Revised: 02/11/2009] [Accepted: 02/17/2009] [Indexed: 01/20/2023]
Abstract
BACKGROUND Phosphatidylcholine (PC) is the predominant phospholipid associated with high density lipoproteins (HDL). Although the hepatic uptake of cholesteryl esters from HDL is well characterized, much less is known about the fate of PC associated with HDL. Thus, we investigated the uptake and subsequent metabolism of HDL-PC in primary mouse hepatocytes. METHODS AND RESULTS The absence of scavenger receptor-BI resulted in a 30% decrease in cellular incorporation of [(3)H]PC whereas [(3)H]cholesteryl ether uptake was almost completely abolished. Although endocytosis is not involved in the uptake of cholesteryl esters from HDL, we demonstrate that HDL internalization accounts for 40% of HDL-PC uptake. Extracellular remodeling of HDL by secretory phospholipase A(2) significantly enhances HDL lipid uptake. HDL-PC taken up by hepatocytes is partially converted to triacylglycerols via PC-phospholipase C-mediated hydrolysis of PC and incorporation of diacylglycerol into triacylglycerol. The formation of triacylglycerol is independent of scavenger receptor-BI and occurs in extralysosomal compartments. CONCLUSIONS AND GENERAL SIGNIFICANCE These findings indicate that HDL-associated PC is incorporated into primary hepatocytes via a pathway that differs significantly from that of HDL-cholesteryl ester, and shows that HDL-PC is more than a framework molecule, as evidenced by its partial conversion to hepatic triacylglycerol.
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Affiliation(s)
- Julie C Robichaud
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada
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10
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Minahk C, Kim KW, Nelson R, Trigatti B, Lehner R, Vance DE. Conversion of low density lipoprotein-associated phosphatidylcholine to triacylglycerol by primary hepatocytes. J Biol Chem 2008; 283:6449-58. [PMID: 18175806 DOI: 10.1074/jbc.m706995200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
We have studied the uptake and metabolism of phosphatidylcholine (PC), the major phospholipid of low density lipoproteins (LDL), by cultures of primary hepatocytes. Strikingly, in the absence of the LDL receptor, PC incorporation into hepatocytes was inhibited by only 30%, whereas cholesteryl ether uptake was inhibited by 60-70%. On the other hand, scavenger receptor class B, type I, the other important receptor for LDL in the liver, was found to be responsible for the uptake of the remaining 30-40% of LDL-cholesteryl ether. PC uptake was, however, only partially inhibited (30%) in scavenger receptor class B, type I, knock-out hepatocytes. Once LDL-PC was taken up by hepatocytes, approximately 50% of LDL-[(3)H]oleate-PC was converted to triacylglycerol rather than degraded in lysosomes as occurs for LDL-derived cholesteryl esters. The remainder of the LDL-derived PC was not significantly metabolized to other products. Triacylglycerol synthesis from LDL-PC requires a PC-phospholipase C activity as demonstrated by inhibition with the phospholipase C inhibitor D609 or activation with rattlesnake venom. Small interfering RNA-mediated suppression of acyl-CoA:diacylglycerol acyltransferase 2 (DGAT2), but not DGAT1, decreased the acylation of the LDL-derived diacylglycerol. These findings show that PC in LDL particles is taken up not only by the classical receptors but also by additional mechanism(s) followed by metabolism that is completely different from the cholesteryl esters or apoB100, the other main components of LDL.
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Affiliation(s)
- Carlos Minahk
- Department of Biochemistry and the Group on the Molecular and Cell Biology of Lipids, University of Alberta, Edmonton, Alberta, Canada
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11
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Ford DA, Monda JK, Brush RS, Anderson RE, Richards MJ, Fliesler SJ. Lipidomic analysis of the retina in a rat model of Smith-Lemli-Opitz syndrome: alterations in docosahexaenoic acid content of phospholipid molecular species. J Neurochem 2007; 105:1032-47. [PMID: 18182048 DOI: 10.1111/j.1471-4159.2007.05203.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Smith-Lemli-Opitz syndrome (SLOS) is a complex hereditary disease caused by an enzymatic defect in the last step of cholesterol biosynthesis. Progressive retinal degeneration occurs in an AY9944-induced rat model of SLOS, with biochemical and electroretinographic hallmarks comparable with the human disease. We evaluated alterations in the non-sterol lipid components of the retina in this model, compared with age-matched controls, using lipidomic analysis. The levels of 16:0-22:6 and 18:0-22:6 phosphatidylcholine molecular species in retinas were less by > 50% and > 33%, respectively, in rats treated for either 2 or 3 months with AY9944. Relative to controls, AY9944 treatment resulted in > 60% less di-22:6 and > 15% less 18:0-22:6 phosphatidylethanolamine molecular species. The predominant phosphatidylserine (PS) molecular species in control retinas were 18:0-22:6 and di-22:6; notably, AY9944 treatment resulted in > 80% less di-22:6 PS, relative to controls. Remarkably, these changes occurred in the absence of n3 fatty acid deficiency in plasma or liver. Thus, the retinal lipidome is globally altered in the SLOS rat model, relative to control rats, with the most profound changes being less phosphatidylcholine, phosphatidylethanolamine, and PS molecular species containing docosahexaenoic acid (22:6). These findings suggest that SLOS may involve additional metabolic compromise beyond the primary enzymatic defect in the cholesterol pathway.
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Affiliation(s)
- David A Ford
- E. A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, Saint Louis, Missouri, USA
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12
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Poulsen KA, Pedersen SF, Kolko M, Lambert IH. Induction of group VIA phospholipase A2activity during in vitro ischemia in C2C12 myotubes is associated with changes in the level of its splice variants. Am J Physiol Cell Physiol 2007; 293:C1605-15. [PMID: 17804611 DOI: 10.1152/ajpcell.00012.2007] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The involvement of group VI Ca2+-independent PLA2s (iPLA2-VI) in in vitro ischemia [oxygen and glucose deprivation (OGD)] in mouse C2C12 myotubes was investigated. OGD induced a time-dependent (0–6 h) increase in bromoenol lactone (BEL)-sensitive iPLA2activity, which was suppressed by specific short interfering (si)RNA knockdown of iPLA2-VIA. OGD was associated with an increase in iPLA2-VIA protein levels, whereas mRNA levels were unchanged. The levels of iPLA2-VIB mRNA and protein were not increased by OGD. RT-PCR and Western blot analysis identified a mouse iPLA2-VIA homolog to catalytically inactive 50-kDa iPLA2-VIA-ankyrin variants previously identified in humans. Both the mRNA and protein levels of this ∼50-kDa variant were reduced significantly within 1 h following OGD. In C2C12 myoblasts, iPLA2-VIA seemed to predominantly reside at the endoplasmatic reticulum, where it accumulated further during OGD. A time-dependent reduction in cell viability during the early OGD period (3 h) was partially prevented by iPLA2-VIA knockdown or pharmacological inhibition (10 μM BEL), whereas iPLA2-VIA overexpression had no effect on cell viability. Taken together, these data demonstrate that OGD in C2C12 myotubes is associated with an increase in iPLA2-VIA activity that decreases cell viability. iPLA2-VIA activation may be modulated by changes in the levels of active and inactive iPLA2-VIA isoforms.
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Affiliation(s)
- K A Poulsen
- Dept. of Molecular Biology, Univ. of Copenhagen, Universitetsparken 13, Copenhagen Ø DK-2100, Denmark.
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13
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Bao S, Li Y, Lei X, Wohltmann M, Jin W, Bohrer A, Semenkovich CF, Ramanadham S, Tabas I, Turk J. Attenuated free cholesterol loading-induced apoptosis but preserved phospholipid composition of peritoneal macrophages from mice that do not express group VIA phospholipase A2. J Biol Chem 2007; 282:27100-27114. [PMID: 17627946 PMCID: PMC2044506 DOI: 10.1074/jbc.m701316200] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Mouse macrophages undergo ER stress and apoptosis upon free cholesterol loading (FCL). We recently generated iPLA(2)beta-null mice, and here we demonstrate that iPLA(2)beta-null macrophages have reduced sensitivity to FCL-induced apoptosis, although they and wild-type (WT) cells exhibit similar increases in the transcriptional regulator CHOP. iPLA(2)beta-null macrophages are also less sensitive to apoptosis induced by the sarcoplasmic reticulum Ca(2+)-ATPase inhibitor thapsigargin and the scavenger receptor A ligand fucoidan, and restoring iPLA(2)betaexpression with recombinant adenovirus increases apoptosis toward WT levels. WT and iPLA(2)beta-null macrophages incorporate [(3)H]arachidonic acid ([(3)H]AA]) into glycerophosphocholine lipids equally rapidly and exhibit identical zymosan-induced, cPLA(2)alpha-catalyzed [(3)H]AA release. In contrast, although WT macrophages exhibit robust [(3)H]AA release upon FCL, this is attenuated in iPLA(2)beta-null macrophages and increases toward WT levels upon restoring iPLA(2)beta expression. Recent reports indicate that iPLA(2)beta modulates mitochondrial cytochrome c release, and we find that thapsigargin and fucoidan induce mitochondrial phospholipid loss and cytochrome c release into WT macrophage cytosol and that these events are blunted in iPLA(2)beta-null cells. Immunoblotting studies indicate that iPLA(2)beta associates with mitochondria in macrophages subjected to ER stress. AA incorporation into glycerophosphocholine lipids is unimpaired in iPLA(2)beta-null macrophages upon electrospray ionization-tandem mass spectrometry analyses, and their complex lipid composition is similar to WT cells. These findings suggest that iPLA(2)beta participates in ER stress-induced macrophage apoptosis caused by FCL or thapsigargin but that deletion of iPLA(2)beta does not impair macrophage arachidonate incorporation or phospholipid composition.
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Affiliation(s)
- Shunzhong Bao
- Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the
| | - Yankun Li
- Departments of Medicine and of Anatomy and Cell Biology, Columbia University, New York, New York 10032
| | - Xiaoyong Lei
- Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the
| | - Mary Wohltmann
- Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the
| | - Wu Jin
- Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the
| | - Alan Bohrer
- Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the
| | - Clay F Semenkovich
- Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the
| | - Sasanka Ramanadham
- Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the
| | - Ira Tabas
- Departments of Medicine and of Anatomy and Cell Biology, Columbia University, New York, New York 10032
| | - John Turk
- Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the.
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14
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Postle AD, Wilton DC, Hunt AN, Attard GS. Probing phospholipid dynamics by electrospray ionisation mass spectrometry. Prog Lipid Res 2007; 46:200-24. [PMID: 17540449 DOI: 10.1016/j.plipres.2007.04.001] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2007] [Revised: 03/30/2007] [Accepted: 04/04/2007] [Indexed: 11/25/2022]
Abstract
Recent advances in electrospray ionisation mass spectrometry (ESI-MS) have greatly facilitated the analysis of phospholipid molecular species in a growing diversity of biological and clinical settings. The combination of ESI-MS and metabolic labelling employing substrates labelled with stable isotopes is especially exciting, permitting studies of phospholipid synthesis and turnover in vivo. This review will first describe the methodology involved and will then detail dynamic lipidomic studies that have applied the stable isotope incorporation approach. Finally, it will summarise the increasing number of studies that have used ESI-MS to characterise structural and signalling phospholipid molecular species in development and disease.
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Affiliation(s)
- Anthony D Postle
- School of Medicine, University of Southampton, Southampton SO17 1BJ, UK.
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15
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Gruber F, Oskolkova O, Leitner A, Mildner M, Mlitz V, Lengauer B, Kadl A, Mrass P, Krönke G, Binder BR, Bochkov VN, Leitinger N, Tschachler E. Photooxidation generates biologically active phospholipids that induce heme oxygenase-1 in skin cells. J Biol Chem 2007; 282:16934-41. [PMID: 17449870 DOI: 10.1074/jbc.m702523200] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Heme oxygenase-1 (HO-1) is a key enzyme in the cellular response to tissue injury and oxidative stress. HO-1 enzymatic activity results in the formation of the cytoprotective metabolites CO and biliverdin. In the skin, HO-1 is strongly induced after long wave ultraviolet radiation (UVA-1). Here we show that UVA-1 irradiation generates oxidized phospholipids derived from 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine (PAPC) that mediate the expression of HO-1 in skin cells. Using EO6 antibodies that recognize oxidized phospholipids, we show that UVA-1 irradiation of dermal fibroblasts generates oxidation-specific epitopes. Irradiation of arachidonate-containing phospholipids with UVA-1 led to formation of defined lipid oxidation products including epoxyisoprostane-phosphatidylcholine that induced HO-1 expression in dermal fibroblasts, in keratinocytes, and in a three-dimensional epidermal equivalent model. In addition, we demonstrate that the oxidation of PAPC by UVA-1 is a singlet oxygen-dependent mechanism. Together, we present a novel mechanism of UVA-1-induced HO-1 expression that is mediated by the generation of biologically active phospholipid oxidation products. Because UVA-1 irradiation is a mainstay treatment of several inflammatory skin diseases, structural identification of UVA-1-generated biomolecules with HO-1-inducing capacity should lead to the development of drugs that could substitute for irradiation.
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Affiliation(s)
- Florian Gruber
- Deparment of Dermatology, Medical University of Vienna, Vienna 1090, Austria
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16
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Kinsey GR, McHowat J, Beckett CS, Schnellmann RG. Identification of calcium-independent phospholipase A2gamma in mitochondria and its role in mitochondrial oxidative stress. Am J Physiol Renal Physiol 2006; 292:F853-60. [PMID: 17047165 DOI: 10.1152/ajprenal.00318.2006] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Oxidant-induced lipid peroxidation and cell death mediate pathologies associated with ischemia-reperfusion and inflammation. Our previous work in rabbit renal proximal tubular cells (RPTC) demonstrated that inhibition of Ca(2+)-independent phospholipase A(2) (iPLA(2)) potentiates oxidant-induced lipid peroxidation and necrosis, implicating iPLA(2) in phospholipid repair. This study was conducted to identify a RPTC mitochondrial PLA(2) and determine the role of PLA(2) in oxidant-induced mitochondrial dysfunction. iPLA(2) activity was detected in Percoll-purified rabbit renal cortex mitochondria (RCM) and in isolated mitochondrial inner membrane fractions from rabbit and human RCM. Immunoblot analysis and inhibitor sensitivity profiles revealed that iPLA(2)gamma is the RCM iPLA(2) activity. RCM iPLA(2) activity was enhanced in the presence of ATP and was blocked by the PKCepsilon V1-2 inhibitor. Oxidant-induced mitochondrial lipid peroxidation and swelling were accelerated by pretreatment with R-BEL, but not S-BEL. Furthermore, oxidant treatment of isolated RCM resulted in decreased iPLA(2)gamma activity. These results reveal that RCM iPLA(2) is iPLA(2)gamma, RCM iPLA(2)gamma is regulated by phosphorylation by PKCepsilon, iPLA(2)gamma protects RCM from oxidant-induced lipid peroxidation and dysfunction, and that a strategy to preserve or enhance iPLA(2)gamma activity may be of therapeutic benefit.
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Affiliation(s)
- Gilbert R Kinsey
- Dept. of Pharmaceutical Sciences, Medical University of South Carolina, Charleston, SC 29425, USA
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17
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Yedgar S, Cohen Y, Shoseyov D. Control of phospholipase A2 activities for the treatment of inflammatory conditions. Biochim Biophys Acta Mol Cell Biol Lipids 2006; 1761:1373-82. [PMID: 16978919 DOI: 10.1016/j.bbalip.2006.08.003] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2006] [Accepted: 08/01/2006] [Indexed: 01/10/2023]
Abstract
Phospholipase-A2 (PLA2) enzymes hydrolyze cell membrane phospholipids to produce arachidonic acid (AA) and lyso-phospholipids (LysoPL), playing a key role in the production of inflammatory lipid mediators, mainly eicosanoids. They are therefore considered pro-inflammatory enzymes and their inhibition has long been recognized as a desirable therapeutic target. However, attempts to develop suitable PLA2 inhibitors for the treatment of inflammatory diseases have yet to succeed. This is due to their functional and structural diversity, and their homeostatic and even anti-inflammatory roles in certain circumstances. In the present review we outline the diversity and functions of PLA2 isoforms, and their interplay in the induction and inhibition of inflammatory processes, with emphasis on discussing approaches for therapeutic manipulation of PLA2 activities.
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Affiliation(s)
- Saul Yedgar
- Department of Biochemistry, Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel.
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18
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Hunt AN, Postle AD. Mass spectrometry determination of endonuclear phospholipid composition and dynamics. Methods 2006; 39:104-11. [PMID: 16831558 DOI: 10.1016/j.ymeth.2006.05.005] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2006] [Accepted: 05/01/2006] [Indexed: 11/19/2022] Open
Abstract
Mammalian cell lipid analyses using tandem electrospray ionization mass spectrometry, in conjunction with stable isotope labeling, permit unparalleled access to membrane phospholipid molecular species compositions and turnover. Lipidomic data from isolable compartments of lipid second messenger generation, such as membrane-free nuclei, can provide dynamic insights into the topology of phospholipid turnover. For example, ESI-MS/MS precursor scans of characteristic phosphocholine m/z 184(+) fragments reveal a highly saturated endonuclear phosphatidylcholine pool with homeostatic maintenance properties. A spatially distinct CDPcholine pathway yields, within minutes of choline-d(9) labeling, unsaturated endonuclear phosphatidylcholines progressively remodeled to more saturated species evidenced by tracking the deuteriated headgroup through precursor scans of phosphocholine-d(9) (m/z 193(+) fragment). Among the other endonuclear phospholipids, diacyl phosphatidylethanolamines (neutral loss of m/z 141(+)) are also highly saturated compared with those of whole cell whereas, phophatidylinositols (precursor scans of m/z 241(-) fragment) are essentially identical in nuclei and whole cells. Moreover, the pattern of myo-inositol-d(6) acquisition into endonuclear phosphatidylinositol (precursor scans of m/z 247(-) fragment) is inconsistent with compartment-specific synthesis. Endonuclear sphingomyelins (seen in precursor scans of m/z 184(+) and confirmed from precursor scans of m/z 168(-) fragments) are enriched but similar in composition to whole cell species whereas endonuclear phosphatidylserines (neutral loss of m/z 87(-)) are more saturated than their whole cell counterparts. The focus of described methodologies emphasize their value in probing the compositions and dynamics of endonuclear phospholipids, but in principle may be extended to exploration of other isolable compartments including ER or plasma membranes.
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Affiliation(s)
- Alan N Hunt
- Allergy and Inflammation Research, Division of Infection, Inflammation and Repair, School of Medicine, University of Southampton, Southampton SO16 6YD, UK.
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19
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Hunt AN. Completing the cycles; the dynamics of endonuclear lipidomics. Biochim Biophys Acta Mol Cell Biol Lipids 2006; 1761:577-87. [PMID: 16581290 DOI: 10.1016/j.bbalip.2006.02.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2006] [Revised: 02/17/2006] [Accepted: 02/20/2006] [Indexed: 12/29/2022]
Abstract
Signal transductions via periodic generation and mobilisation of lipid second messengers within the nuclear matrix of eukaryotic cells have focused renewed attention on their precursor phospholipids' location, structure, form and function. The nuclear matrix contains and supports dynamic pools of phosphatidylcholine and phosphatidylinositol which serve as parent molecules of lipid second messengers but also of other phospholipids requiring cyclical replacement as cells proliferate. Applications of new, highly sensitive and specific analytical methodologies based on tandem electrospray ionisation mass spectrometry and the use of stable isotopes have allowed both static and dynamic lipidomic profiling of these endonuclear phospholipid pools. Together with more conventional enzymatic analyses and evaluation of the effect of specific "knock-out" of phospholipid transfer capacity, a number of important principles have been established. Specifically, a compartmental capacity to synthesise and remodel highly saturated phosphatidylcholine exists alongside transport mechanisms that facilitate the nuclear import of phosphatidylinositol and other phospholipids synthesised elsewhere within the cell. Subnuclear fractionation and the use of newly emerging techniques for sensitive lipidomic profiling of polyphosphoinositides, diacylglycerols and phosphatidate molecular species offer the potential for further significant advances in the near future.
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Affiliation(s)
- Alan N Hunt
- Allergy and Inflammation Research, Division of Infection, Inflammation and Repair, School of Medicine, University of Southampton, Southampton General Hospital, Tremona Road, Southampton SO16 6YD, UK.
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20
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Abstract
Once nuclear envelope membranes have been removed from isolated nuclei, around 6% of mammalian cell phospholipid is retained within the nuclear matrix, which calculations suggest may occupy 10% of the volume of this subcellular compartment. It is now acknowledged that endonuclear phospholipid, largely ignored for the past 40 years, provides substrate for lipid-mediated signaling events. However, given its abundance, it likely also has other as yet incompletely defined roles. Endonuclear phosphatidylcholine is the predominant phospholipid comprising distinct and highly saturated molecular species compared with that of the whole cell. Moreover, this unusual composition is subject to tight homeostatic maintenance even under conditions of extreme dietary manipulation, presumably reflecting a functional requirement for highly saturated endonuclear phosphatidylcholine. Recent application of new lipidomic technologies exploiting tandem electrospray ionization mass spectrometry in conjunction with deuterium stable isotope labeling have permitted us to probe not just molecular species compositions but endonuclear phospholipid acquisition and turnover with unparalleled sensitivity and specificity. What emerges is a picture of a dynamic pool of endonuclear phospholipid subject to autonomous regulation with respect to bulk cellular phospholipid metabolism. Compartmental biosynthesis de novo of endonuclear phosphatidylcholine contrasts with import of phosphatidylinositol synthesized elsewhere. However, irrespective of the precise temporal-spatial-dynamic relationships underpinning phospholipid acquisition, derangement of endonuclear lipid-mediated signaling from these parental phospholipids halts cell growth and division indicating a pivotal control point. This in turn defines the manipulation of compartmentalized endonuclear phospholipid acquisition and metabolism as intriguing potential targets for the development of future antiproliferative strategies.
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Affiliation(s)
- Alan N Hunt
- Allergy and Inflammation Research, Division of Infection, Inflammation & Repair, School of Medicine, University of Southampton, Southampton SO16 6YD, United Kingdom.
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21
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Yan W, Jenkins CM, Han X, Mancuso DJ, Sims HF, Yang K, Gross RW. The Highly Selective Production of 2-Arachidonoyl Lysophosphatidylcholine Catalyzed by Purified Calcium-independent Phospholipase A2γ. J Biol Chem 2005; 280:26669-79. [PMID: 15908428 DOI: 10.1074/jbc.m502358200] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Herein, we report the heterologous expression of the human peroxisomal 63-kDa calcium-independent phospholipase A2gamma (iPLA2gamma) isoform in Sf9 cells, purification of the N-terminal His-tagged enzyme by affinity chromatography, and the identification of its remarkable substrate selectivity that results in the highly selective generation of 2-arachidonoyl lysophosphatidylcholine. Mass spectrometric analyses demonstrated that purified iPLA2gamma hydrolyzed saturated or monounsaturated aliphatic groups readily from either the sn-1 or sn-2 positions of phospholipids. In addition, purified iPLA2gamma effectively liberated arachidonic acid from the sn-2 position of plasmenylcholine substrates. In contrast, incubation of iPLA2gamma with 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine resulted in the rapid release of palmitic acid and the selective accumulation of 2-arachidonoyl lysophosphatidylcholine (LPC), which was not metabolized further by iPLA2gamma. The putative regiospecificity of the 2-arachidonoyl LPC product was authenticated by its diagnostic fragmentation pattern during tandem mass spectrometric analysis. To identify the physiological relevance of iPLA2gamma-mediated 2-arachidonoyl LPC production utilizing naturally occurring membranes, we incubated purified rat hepatic peroxisomes with iPLA2gamma and similarly identified the selective accumulation of 2-arachidonoyl LPC. Furthermore, tandem mass spectrometric analysis demonstrated that 2-arachidonoyl LPC is a natural product in human myocardium, a tissue in which iPLA2gamma expression is robust. Because 2-arachidonoyl LPC represents a key branch point intermediate that can potentially lead to a variety of bioactive molecules in eicosanoid signaling (e.g. arachidonic acid, 2-arachidonoylglycerol), these results have uncovered a novel eicosanoid selective pathway through iPLA2gamma-mediated 2-arachidonoyl LPC production to amplify and diversify the repertoire of biologic lipid second messengers in response to cellular stimulation.
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Affiliation(s)
- Wei Yan
- Division of Bioorganic Chemistry and Molecular Pharmacology, Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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22
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Han X, Gross RW. Shotgun lipidomics: electrospray ionization mass spectrometric analysis and quantitation of cellular lipidomes directly from crude extracts of biological samples. MASS SPECTROMETRY REVIEWS 2005; 24:367-412. [PMID: 15389848 DOI: 10.1002/mas.20023] [Citation(s) in RCA: 876] [Impact Index Per Article: 46.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Lipidomics, after genomics and proteomics, is a newly and rapidly expanding research field that studies cellular lipidomes and the organizational hierarchy of lipid and protein constituents mediating life processes. Lipidomics is greatly facilitated by recent advances in, and novel applications of, electrospray ionization mass spectrometry (ESI/MS). In this review, we will focus on the advances in ESI/MS, which have facilitated the development of shotgun lipidomics and the utility of intrasource separation as an enabling strategy for utilization of 2D mass spectrometry in shotgun lipidomics of biological samples. The principles and experimental details of the intrasource separation approach will be extensively discussed. Other ESI/MS approaches towards the quantitative analyses of global cellular lipidomes directly from crude lipid extracts of biological samples will also be reviewed and compared. Multiple examples of lipidomic analyses from crude lipid extracts employing these approaches will be given to show the power of ESI/MS techniques in lipidomics. Currently, modern society is plagued by the sequelae of lipid-related diseases. It is our hope that the integration of these advances in multiple disciplines will catalyze the development of lipidomics, and such development will lead to improvements in diagnostics and therapeutics, which will ultimately result in the extended longevity and an improved quality of life for humankind.
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Affiliation(s)
- Xianlin Han
- Division of Bioorganic Chemistry and Molecular Pharmacology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
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23
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Han X, Cheng H, Mancuso DJ, Gross RW. Caloric restriction results in phospholipid depletion, membrane remodeling, and triacylglycerol accumulation in murine myocardium. Biochemistry 2005; 43:15584-94. [PMID: 15581371 DOI: 10.1021/bi048307o] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Herein, we utilize the power of shotgun lipidomics to demonstrate that modest caloric restriction results in phospholipid depletion, membrane remodeling, and triacylglycerol (TAG) accumulation in murine myocardium. After brief periods of fasting (4 and 12 h), substantial decreases occurred in the choline and ethanolamine glycerophospholipid pools in murine myocardium (collectively, a decrease of 39 nmol of phospholipid per milligram of protein at 12 h representing approximately 25% of total phospholipid mass and approximately 20 cal of Gibbs free energy per gram wet weight of tissue). Remarkably, the selective loss of long-chain polyunsaturated molecular species was present in the major phospholipid classes thereby altering the physical properties of myocardial membranes. No decrease in TAG mass was present in myocardium during fasting, but rather myocardial TAG increased during 12 h of refeeding nearly 3-fold returning to baseline levels only after 24 h of refeeding. No alterations in other examined lipid classes were present during fasting. In contrast to these lipid alterations in myocardium, no decreases in phospholipid mass were present in skeletal muscle myocytes and a dramatic decrease in skeletal muscle (or skeletal muscle associated) TAG mass was prominent after 12 h of fasting. These results identify phospholipids as a rapidly mobilizable energy source during modest caloric deprivation in murine myocardium, while triacylglycerols are a major source of energy reserve in skeletal muscle. Collectively, these results demonstrate dramatic alterations in the membrane composition of mildly fasted mammalian myocardium that identify the unanticipated plasticity of myocardial phospholipids to adapt to modest chemical and physical perturbations.
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Affiliation(s)
- Xianlin Han
- Division of Bioorganic Chemistry and Molecular Pharmacology, and Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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24
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Delton-Vandenbroucke I, Lemaire P, Lagarde M, Laugier C. Hydrolysis of nuclear phospholipids in relation with proliferative state in uterine stromal cells. Biochimie 2004; 86:269-74. [PMID: 15194229 DOI: 10.1016/j.biochi.2004.04.006] [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] [Received: 11/04/2003] [Accepted: 04/01/2004] [Indexed: 01/12/2023]
Abstract
The current study examined the metabolism of phospholipid (PL) in the whole cell homogenate and in the nuclear fraction in proliferative and non-proliferative uterine stromal cells (U(III) cells). Growth arrested cells were obtained either from contact-inhibited confluent cells or from proliferative cells treated with aristolochic acid (AR) for 2 days. Fatty acid composition and fatty acid amount of both total and nuclear PL were not significantly different between proliferative, confluent and AR-treated cells. In contrast, marked differences were observed in the incorporation of [(3)H]AA, with greater incorporation in proliferative cells than in confluent or AR-treated cells, particularly in nuclear PL. Considering endogenous level of arachidonic acid (AA) in total and nuclear PL, we found that AA turnover in nuclear PL was especially high compared to that in total PL and that this difference was accentuated in proliferative cells compared to non-proliferative cells. Interestingly, [(3)H]AA incorporation and AA turnover in proliferative, confluent and AR-treated cells vary accordingly to the expression, activity and/or content of pancreatic phospholipase A(2) (PLA(2)-I) in the nuclear compartment of these cells that we reported in previous studies. The changes in metabolism of nuclear PL during cell proliferation are consistent with an enhanced PL hydrolysis that could involve PLA(2)-I.
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Abstract
The catalytic activity of calcium-independent phospholipase A2 (iPLA2), which is classified as a group VI PLA2, is regulated by protein kinase C, calmodulin, and others such as reactive oxygen species. Numerous findings have shown that iPLA2 is involved in stimulus-induced arachidonic acid release and lysophospholipid generation, although the participation is dependent upon the cell type and stimulus. The catalytic action of iPLA2 is known to be responsible for phospholipid remodeling as a housekeeping function. However, it has been widely accepted that arachidonic acid and lysophospholipid generated by iPLA2 act as a signaling molecule in cellular functions. Those include eicosanoid production, glucose-induced insulin secretion, Fas-induced apoptosis, cellular proliferation, membrane traffic in fusion, contribution to myocardial ischemia, and others. In this review, the functional role of iPLA2 in cellular responses upon stimulation is the focus.
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Affiliation(s)
- Satoshi Akiba
- Department of Pathological Biochemistry, Kyoto Pharmaceutical University, Kyoto, Japan
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26
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Abstract
Apoptosis is defined on the basis of morphological changes like nuclear fragmentation and chromatin condensation, which are dependent on caspases. Many forms of caspase-independent cell death have been reported, but the mechanisms are still poorly understood. We found that hypoxic cell death was independent of caspases and was associated with significant nuclear shrinkage. Neither Bcl-2 nor Apaf-1 deficiency prevented hypoxic nuclear shrinkage. To understand the molecular mechanism of the nuclear shrinkage, we developed an in vitro system using permeabilized cells, which allowed us to purify a novel member of the phospholipase A2 (PLA2) family that induced nuclear shrinkage. Purified PLA2 induced nuclear shrinkage in our permeabilized cell system. PLA2 inhibitors prevented hypoxic nuclear shrinkage in cells and cell death. Hypoxia caused elevation of PLA2 activity and translocation of intracellular PLA2s to the nucleus. Knockdown of the Ca2+-independent PLA2 delayed nuclear shrinkage and cell death. These results indicate that Ca2+-independent PLA2 is crucial for a caspase-independent cell death signaling pathway leading to nuclear shrinkage.
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Affiliation(s)
- Koei Shinzawa
- Laboratory of Molecular Genetics, Department of Post-Genomics and Diseases, Osaka University Medical School, Yamadaoka, Suita, Osaka 565-0871, Japan
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27
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Stahelin RV, Rafter JD, Das S, Cho W. The molecular basis of differential subcellular localization of C2 domains of protein kinase C-alpha and group IVa cytosolic phospholipase A2. J Biol Chem 2003; 278:12452-60. [PMID: 12531893 DOI: 10.1074/jbc.m212864200] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The C2 domain is a Ca(2+)-dependent membrane-targeting module found in many cellular proteins involved in signal transduction or membrane trafficking. C2 domains are unique among membrane targeting domains in that they show a wide range of lipid selectivity for the major components of cell membranes, including phosphatidylserine and phosphatidylcholine. To understand how C2 domains show diverse lipid selectivity and how this functional diversity affects their subcellular targeting behaviors, we measured the binding of the C2 domains of group IVa cytosolic phospholipase A(2) (cPLA(2)) and protein kinase C-alpha (PKC-alpha) to vesicles that model cell membranes they are targeted to, and we monitored their subcellular targeting in living cells. The surface plasmon resonance analysis indicates that the PKC-alpha C2 domain strongly prefers the cytoplasmic plasma membrane mimic to the nuclear membrane mimic due to high phosphatidylserine content in the former and that Asn(189) plays a key role in this specificity. In contrast, the cPLA(2) C2 domain has specificity for the nuclear membrane mimic over the cytoplasmic plasma membrane mimic due to high phosphatidylcholine content in the former and aromatic and hydrophobic residues in the calcium binding loops of the cPLA(2) C2 domain are important for its lipid specificity. The subcellular localization of enhanced green fluorescent protein-tagged C2 domains and mutants transfected into HEK293 cells showed that the subcellular localization of the C2 domains is consistent with their lipid specificity and could be tailored by altering their in vitro lipid specificity. The relative cell membrane translocation rate of selected C2 domains was also consistent with their relative affinity for model membranes. Together, these results suggest that biophysical principles that govern the in vitro membrane binding of C2 domains can account for most of their subcellular targeting properties.
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Affiliation(s)
- Robert V Stahelin
- Department of Chemistry, University of Illinois at Chicago, Chicago, Illinois 60607, USA
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Welti R, Wang X, Williams TD. Electrospray ionization tandem mass spectrometry scan modes for plant chloroplast lipids. Anal Biochem 2003; 314:149-52. [PMID: 12633615 DOI: 10.1016/s0003-2697(02)00623-1] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Affiliation(s)
- Ruth Welti
- Division of Biology, Kansas State University, Ackert Hall, Manhattan, KS 66506-4901, USA.
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Maggi LB, Moran JM, Scarim AL, Ford DA, Yoon JW, McHowat J, Buller RML, Corbett JA. Novel role for calcium-independent phospholipase A(2) in the macrophage antiviral response of inducible nitric-oxide synthase expression. J Biol Chem 2002; 277:38449-55. [PMID: 12167650 DOI: 10.1074/jbc.m206247200] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The double-stranded (ds) RNA-dependent protein kinase (PKR) is a primary regulator of antiviral responses; however, the ability of dsRNA to activate nuclear factor-kappa B (NF-kappa B) and dsRNA + interferon gamma (IFN-gamma) to stimulate inducible nitric-oxide synthase (iNOS) expression by macrophages isolated from PKR(-/-) mice suggests that signaling pathways in addition to PKR participate in antiviral activities. We have identified a novel phospholipid-signaling cascade that mediates macrophage activation by dsRNA and viral infection. Bromoenol lactone (BEL), a selective inhibitor of the calcium-independent phospholipase A(2) (iPLA(2)), prevents dsRNA- and virus-induced iNOS expression by RAW 264.7 cells and mouse macrophages. BEL does not modulate dsRNA-induced interleukin 1 expression, nor does it affect dsRNA-induced NF-kappa B activation. Protein kinase A (PKA) and the cAMP response element binding protein (CREB) are downstream targets of iPLA(2), because selective PKA inhibition prevents dsRNA-induced iNOS expression, and the inhibitory actions of BEL on dsRNA-induced iNOS expression are overcome by the direct activation of PKA. In addition, BEL inhibits dsRNA-induced CREB phosphorylation and CRE reporter activation. PKR does not participate in iPLA(2) activation or iNOS expression, because dsRNA stimulates iPLA(2) activity and dsRNA + IFN-gamma induces iNOS expression and nitric oxide production to similar levels by macrophages isolated from PKR(+/+) and PKR(-/-) mice. These findings support a PKR-independent signaling role for iPLA(2) in the antiviral response of macrophages.
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Affiliation(s)
- Leonard B Maggi
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, Missouri 63104, USA
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Zacarias A, Bolanowski D, Bhatnagar A. Comparative measurements of multicomponent phospholipid mixtures by electrospray mass spectroscopy: relating ion intensity to concentration. Anal Biochem 2002; 308:152-9. [PMID: 12234476 DOI: 10.1016/s0003-2697(02)00209-9] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Electrospray mass spectrometry allows direct identification and sensitive detection of multiple phospholipids in non-derivatized cell extracts. However, quantitative analyses are not straightforward, and are confounded by analyte and mass discrimination effects, and non-linear dependence of the ion intensity on concentration. This non-linearity is particularly severe in the negative mode and precludes even comparative measurements of anion concentrations. Herein, we report a general method for relating negative electrospray ion intensity to concentration when analyzing multicomponent phospholipid samples. In this method, the intensity of individual ions is measured at several different concentrations of the total mixture and the slope (n(E)) of the double log plot of sample concentration vs. intensity for each analyte is determined. The n(E) is then used to map intensity data to a quantity proportional to concentration for each analyte. The method allows facile and accurate comparison of negative spectra of complex mixtures containing structurally different anions.
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Affiliation(s)
- Albert Zacarias
- Division of Cardiology, Department of Medicine, University of Louisville, 500 S Floyd St, KY 40202, USA
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31
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Welti R, Li W, Li M, Sang Y, Biesiada H, Zhou HE, Rajashekar CB, Williams TD, Wang X. Profiling membrane lipids in plant stress responses. Role of phospholipase D alpha in freezing-induced lipid changes in Arabidopsis. J Biol Chem 2002; 277:31994-2002. [PMID: 12077151 DOI: 10.1074/jbc.m205375200] [Citation(s) in RCA: 670] [Impact Index Per Article: 30.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A sensitive approach based on electrospray ionization tandem mass spectrometry has been employed to profile membrane lipid molecular species in Arabidopsis undergoing cold and freezing stresses. Freezing at a sublethal temperature induced a decline in many molecular species of phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylglycerol (PG) but induced an increase in phosphatidic acid (PA) and lysophospholipids. To probe the metabolic steps generating these changes, lipids of Arabidopsis deficient in the most abundant phospholipase D, PLD alpha, were analyzed. The PC content dropped only half as much, and PA levels rose only half as high in the PLD alpha-deficient plants as in wild-type plants. In contrast, neither PE nor PG levels decreased significantly more in wild-type plants than in PLD alpha-deficient plants. These data suggest that PC, rather than PE and PG, is the major in vivo substrate of PLD alpha. The action of PLD alpha during freezing is of special interest because Arabidopsis plants that are deficient in PLD alpha have improved tolerance to freezing. The greater loss of PC and increase in PA in wild-type plants as compared with PLD alpha-deficient plants may be responsible for destabilizing membrane bilayer structure, resulting in a greater propensity toward membrane fusion and cell death in wild-type plants.
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Affiliation(s)
- Ruth Welti
- Division of Biology, Ackert Hall, Kansas State University, Manhattan, Kansas 66506, USA.
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Das S, Cho W. Roles of catalytic domain residues in interfacial binding and activation of group IV cytosolic phospholipase A2. J Biol Chem 2002; 277:23838-46. [PMID: 11956215 DOI: 10.1074/jbc.m202322200] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Group IV cytosolic phospholipase A(2) (cPLA(2)) has been shown to play a critical role in eicosanoid biosynthesis. cPLA(2) is composed of the C2 domain that mediates the Ca(2+)-dependent interfacial binding of protein and the catalytic domain. To elucidate the mechanism of interfacial activation of cPLA(2), we measured the effects of mutations of selected ionic and hydrophobic residues in the catalytic domain on the enzyme activity and the membrane binding of cPLA(2). Mutations of anionic residues located on (Glu(419) and Glu(420)) or near (Asp(436), Asp(438), Asp(439), and Asp(440)) the active site lid enhanced the affinity for cPLA(2) for anionic membranes, implying that the electrostatic repulsion between these residues and the anionic membrane surface might trigger the opening of the active site. This notion is further supported by a biphasic dependence of cPLA(2) activity on the anionic lipid composition of the vesicles. Mutations of a cluster of cationic residues (Lys(541), Lys(543), Lys(544), and Arg(488)), while significantly enhancing the activity of enzyme, abrogated the specific activation effect by phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P(2)). These data, in conjunction with cell activity of cPLA(2) and mutants transfected into HEK293 cells, suggest that the cationic residues form a specific binding site for PtdIns(4,5)P(2) and that the specific PtdIns(4,5)P(2) binding is involved in cellular activation of cPLA(2). Also, three hydrophobic residues at the rim of the active site (Ile(399), Leu(400), and Leu(552)) were shown to partially penetrate the membrane, thereby promoting membrane binding and activation of cPLA(2). Based on these results, we propose an interfacial activation mechanism for cPLA(2) which involves the removal of the active site lid by nonspecific electrostatic repulsion, the interdomain hinge movement induced by specific PtdIns(4,5)P(2) binding, and the partial membrane penetration by catalytic domain hydrophobic residues.
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Affiliation(s)
- Sudipto Das
- Department of Chemistry, University of Illinois, Chicago, Illinois 60607-7061, USA
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Kulkarni S, Das S, Funk CD, Murray D, Cho W. Molecular basis of the specific subcellular localization of the C2-like domain of 5-lipoxygenase. J Biol Chem 2002; 277:13167-74. [PMID: 11796736 DOI: 10.1074/jbc.m112393200] [Citation(s) in RCA: 134] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The activation of 5-lipoxygenase (5-LO) involves its calcium-dependent translocation to the nuclear envelope, where it catalyzes the two-step transformation of arachidonic acid into leukotriene A(4), leading to the synthesis of various leukotrienes. To understand the mechanism by which 5-LO is specifically targeted to the nuclear envelope, we studied the membrane binding properties of the amino-terminal domain of 5-LO, which has been proposed to have a C2 domain-like structure. The model building, electrostatic potential calculation, and in vitro membrane binding studies of the isolated C2-like domain of 5-LO and selected mutants show that this Ca(2+)-dependent domain selectively binds zwitterionic phosphatidylcholine, which is conferred by tryptophan residues (Trp(13), Trp(75), and Trp(102)) located in the putative Ca(2+)-binding loops. The spatiotemporal dynamics of the enhanced green fluorescence protein-tagged C2-like domain of 5-LO and mutants in living cells also show that the phosphatidylcholine selectivity of the C2-like domain accounts for the specific targeting of 5-LO to the nuclear envelope. Together, these results show that the C2-like domain of 5-LO is a genuine Ca(2+)-dependent membrane-targeting domain and that the subcellular localization of the domain is governed in large part by its membrane binding properties.
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Affiliation(s)
- Shilpa Kulkarni
- Department of Chemistry, University of Illinois, 845 West Taylor Street, Chicago, IL 60607-7061, USA
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Ma Z, Zhang S, Turk J, Ramanadham S. Stimulation of insulin secretion and associated nuclear accumulation of iPLA(2)beta in INS-1 insulinoma cells. Am J Physiol Endocrinol Metab 2002; 282:E820-33. [PMID: 11882502 DOI: 10.1152/ajpendo.00165.2001] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Accumulating evidence suggests that the cytosolic calcium-independent phospholipase A(2) (iPLA(2)beta) manifests a signaling role in insulin-secreting (INS-1) beta-cells. Earlier, we reported that insulin-secretory responses to cAMP-elevating agents are amplified in iPLA(2)beta-overexpressing INS-1 cells (Ma Z, Ramanadham S, Bohrer A, Wohltmann M, Zhang S, and Turk J. J Biol Chem 276: 13198-13208, 2001). Here, immunofluorescence, immunoaffinity, and enzymatic activity analyses are used to examine distribution of iPLA(2)beta in stimulated INS-1 cells in greater detail. Overexpression of iPLA(2)beta in INS-1 cells leads to increased accumulation of iPLA(2)beta in the nuclear fraction. Increasing glucose concentrations alone results in modest increases in insulin secretion, relative to parental cells, and in nuclear accumulation of the iPLA(2)beta protein. In contrast, cAMP-elevating agents induce robust increases in insulin secretion and in time-dependent nuclear accumulation of iPLA(2)beta fluorescence, which is reflected by increases in nuclear iPLA(2)beta protein content and specific enzymatic activity. The stimulated effects are significantly attenuated in the presence of cell-permeable inhibitors of protein phosphorylation and glycosylation. These findings suggest that conditions that amplify insulin secretion promote translocation of beta-cell iPLA(2)beta to the nuclei, where it may serve a crucial signaling role.
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Affiliation(s)
- Zhongmin Ma
- Division of Experimental Diabetes and Aging, Mount Sinai School of Medicine, New York, New York 10029, USA
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Kim YJ, Kim KP, Rhee HJ, Das S, Rafter JD, Oh YS, Cho W. Internalized group V secretory phospholipase A2 acts on the perinuclear membranes. J Biol Chem 2002; 277:9358-65. [PMID: 11777916 DOI: 10.1074/jbc.m110987200] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mammalian secretory phospholipases A(2) (sPLA(2)) have been implicated in cellular eicosanoid biosynthesis but the mechanism of their cellular action remains unknown. To elucidate the spatiotemporal dynamics of sPLA(2) mobilization and determine the site of its lipolytic action, we performed time-lapse confocal microscopic imaging of fluorescently labeled sPLA(2) acting on human embryonic kidney (HEK) 293 cells the membranes of which are labeled with a fluorogenic phospholipid, N-((6-(2,4-dinitrophenyl)amino)hexanoyl)-1-hexadecanoyl-2-(4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene-3-pentanoyl)-sn-glycero-3-phosphoethanolamine. The Western blotting analysis of HEK293 cells treated with exogenous sPLA(2)s showed that not only the affinity for heparan sulfate proteoglycan but also other factors, such as sPLA(2) hydrolysis products or cytokines, are necessary for the internalization of sPLA(2) into HEK293 cells. Live cell imaging showed that the hydrolysis of fluorogenic phospholipids incorporated into HEK293 cell membranes was synchronized with the spatiotemporal dynamics of sPLA(2) internalization, detectable initially at the plasma membrane and then at the perinuclear region. Also, immunocytostaining showed that human group V sPLA(2) induced the translocation of 5-lipoxygenase to the nuclear envelope at which they were co-localized. Together, these studies provide the first experimental evidence that the internalized sPLA(2) acts on the nuclear envelope to provide arachidonate for other enzymes involved in the eicosanoid biosynthesis.
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Affiliation(s)
- Young Jun Kim
- Department of Chemistry, University of Illinois at Chicago, Chicago, Illinois 60607, USA
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36
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Jones DR, D'Santos CS, Mérida I, Divecha N. T lymphocyte nuclear diacylglycerol is derived from both de novo synthesis and phosphoinositide hydrolysis. Int J Biochem Cell Biol 2002; 34:158-68. [PMID: 11809418 DOI: 10.1016/s1357-2725(01)00108-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Novel phospholipid metabolism in T lymphocytes and the generation of biologically active lipid second messengers (LSMs) has attracted much attention in recent years. Despite this interest, no reports have attempted to characterise such events in the nuclei of these cells. In order to gain insight into the structural relationships between the lipids diglyceride (DG) and phosphatidic acid (PtdOH) and their structural precursors phosphatidylcholine (PtdCho) and phosphatidylinositides (PtdIns) in the nuclei of CTLL-2 T lymphocytes, an analysis of their molecular species was performed. The results clearly indicated that there were two pools of DG. The major pool consisted primarily of saturated and monunsaturated structures whereas the minor pool consisted of more unsaturated species, most likely derived from PtdIns. Only the latter pool was found to be accessible to endogenous nuclear diacylglycerol kinase (DGK) activity which showed partial inhibition with the recognised DGK inhibitor R59949. Molecular species analysis of the endogenous nuclear PtdOH revealed it to be distinct from that generated by the endogenous DGK, but instead resembled that of PtdCho species. We were unable to detect enzymatic activities which targeted PtdCho (PtdCho-phospholipase C (PtdCho-PLC), PtdCho-phospholipase D (PtdCho-PLD) and sphingomyelin synthase (SMS)) but instead a detectable PtdOH phosphatase (PAP) activity. We propose that, in exponentially growing CTLL-2 cells, synthesis de novo represents one of the routes for the biosynthesis of structural phospholipids which may be the source of biologically active LSMs in the nucleus.
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Affiliation(s)
- David R Jones
- Department of Immunology and Oncology, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas, Cantoblanco, 28049 Madrid, Spain.
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Hunt AN, Clark GT, Attard GS, Postle AD. Highly saturated endonuclear phosphatidylcholine is synthesized in situ and colocated with CDP-choline pathway enzymes. J Biol Chem 2001; 276:8492-9. [PMID: 11121419 DOI: 10.1074/jbc.m009878200] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Chromatin-associated phospholipids are well recognized. A report that catalytically active endonuclear CTP:choline-phosphate cytidylyltransferase alpha is necessary for cell survival questions whether endonuclear, CDP-choline pathway phosphatidylcholine synthesis may occur in situ. We report that chromatin from human IMR-32 neuroblastoma cells possesses such a biosynthetic pathway. First, membrane-free nuclei retain all three CDP-choline pathway enzymes in proportions comparable with the content of chromatin-associated phosphatidylcholine. Second, following supplementation of cells with deuterated choline and using electrospray ionization mass spectrometry, both the time course and molecular species labeling pattern of newly synthesized endonuclear and whole cell phosphatidylcholine revealed the operation of spatially separate, compositionally distinct biosynthetic routes. Specifically, endogenous and newly synthesized endonuclear phosphatidylcholine species are both characterized by a high degree of diacyl/alkylacyl chain saturation. This unusual species content and synthetic pattern (evident within 10 min of supplementation) are maintained through cell growth arrest by serum depletion and when proliferation is restored, suggesting that endonuclear disaturated phosphatidylcholine enrichment is essential and closely regulated. We propose that endonuclear phosphatidylcholine synthesis may regulate periodic nuclear accumulations of phosphatidylcholine-derived lipid second messengers. Furthermore, our estimates of saturated phosphatidylcholine nuclear volume occupancy of around 10% may imply a significant additional role in regulating chromatin structure.
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Affiliation(s)
- A N Hunt
- Department of Child Health, University of Southampton, Southampton General Hospital, Southampton SO16 6YD, United Kingdom.
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Current literature in mass spectrometry. JOURNAL OF MASS SPECTROMETRY : JMS 2001; 36:225-235. [PMID: 11345053 DOI: 10.1002/jms.89] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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