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Milbeck SM, Bhattacharya SK. Alteration in Lysophospholipids and Converting Enzymes in Glaucomatous Optic Nerves. Invest Ophthalmol Vis Sci 2021; 61:60. [PMID: 32602905 PMCID: PMC7415893 DOI: 10.1167/iovs.61.6.60] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Purpose To determine whether lysophospholipid (LPL) profiles and corresponding conversion enzymes in the LPL pathways are altered in the optic nerve (ON) between human control and glaucoma samples. Methods Lipids extracted from control (n = 11) and glaucomatous (n = 12) ON samples using the Bligh and Dyer method were subjected to high-resolution mass spectrometry on a Q-exactive mass spectrometer coupled with a high-performance liquid chromatography (Accela 600) system. Analysis was performed for LPLs (lysophosphatidylcholines, lysophosphatidylserines, lysophosphatidylethanolamines, lysophosphatidylinositols, and lysosphingomyelines) using LipidSearch v.4.1, MZmine v.2.0, and MetaboAnalyst v.4.0. LPL synthesis and degradation pathway maps, utilizing UniProt and BRENDA database entries as needed, were created using Kyoto Encyclopedia of Genes and Genomes (KEGG)-based tools. The mRNA expression level in normal and glaucomatous human ON were analyzed using Gene Expression Omnibus (GEO) entry GSE45570. Protein amounts were determined using PHAST gel and dot blot and were used for normalization of protein amounts across samples. Western blot, ELISA, and protein quantification were performed using established protocols. Results Principal component analysis of ON LPL profile placed control and glaucomatous ONs in two distinct separate groups. Mass spectrometric analysis of ON revealed decrease in lysophosphatidic acid, lysophosphatidylethanolamine, lysophosphatidylcholine, and significant increase in diacylglycerol in glaucomatous ON. Statistical analysis of LPL conversion enzymes revealed significant overexpression of phosphatidate phosphatase LPIN2, phospholipid phosphatase 3, phosphatidylcholine-sterol acyltransferase, and calcium-dependent phospholipase 2, and significant downregulation of glycerol-3-phosphate acyltransferase 4 at mRNA level in glaucomatous ON. Western blot and ELISA confirmed proteomic differences between normal and diseased ON. Conclusions Our analysis revealed alterations in specific LPL levels and corresponding select enzyme-level changes in glaucomatous ON.
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Regulation of phosphatidic Acid metabolism by sphingolipids in the central nervous system. J Lipids 2010; 2011:342576. [PMID: 21490799 PMCID: PMC3068476 DOI: 10.1155/2011/342576] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2010] [Accepted: 10/14/2010] [Indexed: 12/12/2022] Open
Abstract
This paper explores the way ceramide, sphingosine, ceramide 1-phosphate, and sphingosine 1-phosphate modulate the generation of second lipid messengers from phosphatidic acid in two experimental models of the central nervous system: in vertebrate rod outer segments prepared from dark-adapted retinas as well as in rod outer segments prepared from light-adapted retinas and in rat cerebral cortex synaptosomes under physiological aging conditions. Particular attention is paid to lipid phosphate phosphatase, diacylglycerol lipase, and monoacylglycerol lipase. Based on the findings reported in this paper, it can be concluded that proteins related to phototransduction phenomena are involved in the effects derived from sphingosine 1-phosphate/sphingosine or ceramide 1-phosphate/ceramide and that age-related changes occur in the metabolism of phosphatidic acid from cerebral cortex synaptosomes in the presence of either sphingosine 1-phosphate/sphingosine or ceramide 1-phosphate/ceramide. The present paper demonstrates, in two different models of central nervous system, how sphingolipids influence phosphatidic acid metabolism under different physiological conditions such as light and aging.
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Snider AJ, Zhang Z, Xie Y, Meier KE. Epidermal growth factor increases lysophosphatidic acid production in human ovarian cancer cells: roles for phospholipase D2 and receptor transactivation. Am J Physiol Cell Physiol 2010; 298:C163-70. [DOI: 10.1152/ajpcell.00001.2009] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Lysophosphatidic acid (LPA), is a lipid mediator that binds to G-protein coupled receptors. Epidermal growth factor (EGF), a polypeptide growth factor, binds to the EGF receptor (EGFR), a receptor tyrosine kinase. Both LPA and EGF induce responses in tumor cells that include proliferation, migration, metastasis, and induction of angiogenesis. LPA has the potential to act as an autocrine/paracrine factor and can transactivate the EGFR. This study explores the role of phospholipase D2 (PLD2) activation in LPA production, as well as cross-talk between EGF and LPA receptors. We demonstrate that EGF and LPA both stimulate production of LPA by OVCAR3 and SKOV3 human ovarian cancer cell lines. PD158780, an EGFR-selective tyrosine kinase inhibitor, blocks LPA production in response to both EGF and LPA in OVCAR3 and SKOV3 cells. Pertussis toxin, an inhibitor of LPA receptor signaling, inhibits LPA production in response to both EGF and LPA. Similar results were observed for the LPA receptor antagonist, Ki16425. Overexpression of PLD2 increases LPA production, while knockdown of PLD2 blocks EGF-induced LPA production. A phospholipase A2 (PLA2) inhibitor also blocks LPA- and EGF-induced LPA production. These results indicate that EGF stimulates LPA production in a manner that requires PLD2, and suggest that cross-talk can occur bidirectionally between EGF and LPA receptors.
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Affiliation(s)
- Ashley J. Snider
- Department of Pharmaceutical Sciences, Washington State University, Pullman, Washington
| | - Zhihong Zhang
- Department of Pharmaceutical Sciences, Washington State University, Pullman, Washington
| | - Yuhuan Xie
- Department of Pharmaceutical Sciences, Washington State University, Pullman, Washington
| | - Kathryn E. Meier
- Department of Pharmaceutical Sciences, Washington State University, Pullman, Washington
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Zhao Y, Natarajan V. Lysophosphatidic acid signaling in airway epithelium: role in airway inflammation and remodeling. Cell Signal 2009; 21:367-77. [PMID: 18996473 PMCID: PMC2660380 DOI: 10.1016/j.cellsig.2008.10.010] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2008] [Revised: 09/27/2008] [Accepted: 10/21/2008] [Indexed: 02/07/2023]
Abstract
Lysophosphatidic acid (LPA), a potent bioactive phospholipid, induces diverse cellular responses, including cell proliferation, migration, and cytokine release. LPA can be generated intracellularly and extracellularly through multiple synthetic pathways by action of various enzymes, such as phospholipase A(1/2) (PLA(1/2)), phospholipase D (PLD), acylglycerol kinase (AGK), and lysophospholipase D (lysoPLD). Metabolism of LPA is regulated by a family of lipid phosphate phosphatases (LPPs). Significant amounts of LPA have been detected in various biological fluids, including serum, saliva, and bronchoalveolar lavage fluid (BALF). The most significant effects of LPA appear to be through activation of the G-protein-coupled receptors (GPCRs), termed LPA(1-6). LPA regulates gene expression through activation of several transcriptional factors, such as nuclear factor-kappaB (NF-kappaB), AP-1, and C/EBPbeta. In addition to GPCRs, cross-talk between LPA receptors and receptor tyrosine kinases (RTKs) partly regulates LPA-induced intracellular signaling and cellular responses. Airway epithelial cells participate in innate immunity through the release of cytokines, chemokines, lipid mediators, other inflammatory mediators and an increase in barrier function in response to a variety of inhaled stimuli. Expression of LPA receptors has been demonstrated in airway epithelial cells. This review summarizes our recent observations of the role of LPA/LPA-Rs in regulation of airway epithelium, especially in relation to the secretion of pro- and anti-inflammatory mediators and regulation of airway barrier function.
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Affiliation(s)
- Yutong Zhao
- Department of Medicine, University of Chicago, Chicago, IL 60637, USA.
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5
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Affiliation(s)
- Yan Xu
- Department of Obstetrics and Gynecology, Indiana University, 975 W. Walnut St., IB355A, Indianapolis, IN 46202, USA.
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6
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Zhao Y, Kalari SK, Usatyuk PV, Gorshkova I, He D, Watkins T, Brindley DN, Sun C, Bittman R, Garcia JGN, Berdyshev EV, Natarajan V. Intracellular generation of sphingosine 1-phosphate in human lung endothelial cells: role of lipid phosphate phosphatase-1 and sphingosine kinase 1. J Biol Chem 2007; 282:14165-77. [PMID: 17379599 PMCID: PMC2659598 DOI: 10.1074/jbc.m701279200] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Sphingosine 1-phosphate (S1P) regulates diverse cellular functions through extracellular ligation to S1P receptors, and it also functions as an intracellular second messenger. Human pulmonary artery endothelial cells (HPAECs) effectively utilized exogenous S1P to generate intracellular S1P. We, therefore, examined the role of lipid phosphate phosphatase (LPP)-1 and sphingosine kinase1 (SphK1) in converting exogenous S1P to intracellular S1P. Exposure of (32)P-labeled HPAECs to S1P or sphingosine (Sph) increased the intracellular accumulation of [(32)P]S1P in a dose- and time-dependent manner. The S1P formed in the cells was not released into the medium. The exogenously added S1P did not stimulate the sphingomyelinase pathway; however, added [(3)H]S1P was hydrolyzed to [(3)H]Sph in HPAECs, and this was blocked by XY-14, an inhibitor of LPPs. HPAECs expressed LPP1-3, and overexpression of LPP-1 enhanced the hydrolysis of exogenous [(3)H]S1P to [(3)H]Sph and increased intracellular S1P production by 2-3-fold compared with vector control cells. Down-regulation of LPP-1 by siRNA decreased intracellular S1P production from extracellular S1P but had no effect on the phosphorylation of Sph to S1P. Knockdown of SphK1, but not SphK2, by siRNA attenuated the intracellular generation of S1P. Overexpression of wild type SphK1, but not SphK2 wild type, increased the accumulation of intracellular S1P after exposure to extracellular S1P. These studies provide the first direct evidence for a novel pathway of intracellular S1P generation. This involves the conversion of extracellular S1P to Sph by LPP-1, which facilitates Sph uptake, followed by the intracellular conversion of Sph to S1P by SphK1.
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Affiliation(s)
- Yutong Zhao
- Department of Medicine, Section of Pulmonary and Critical Care Medicine, University of Chicago, Chicago, IL 60637, USA
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Pilquil C, Dewald J, Cherney A, Gorshkova I, Tigyi G, English D, Natarajan V, Brindley DN. Lipid phosphate phosphatase-1 regulates lysophosphatidate-induced fibroblast migration by controlling phospholipase D2-dependent phosphatidate generation. J Biol Chem 2006; 281:38418-29. [PMID: 17057224 DOI: 10.1074/jbc.m601670200] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Lysophosphatidate (LPA) stimulates cell migration and division through a family of G-protein-coupled receptors. Lipid phosphate phosphatase-1 (LPP1) regulates the degradation of extracellular LPA as well as the intracellular accumulation of lipid phosphates. Here we show that increasing the catalytic activity of LPP1 decreased the pertussis toxin-sensitive stimulation of fibroblast migration by LPA and an LPA-receptor agonist that could not be dephosphorylated. Conversely, knockdown of endogenous LPP1 activity increased LPA-induced migration. However, LPP1 did not affect PDGF- or endothelin-induced migration of fibroblasts in Transwell chamber and "wound healing" assays. Thus, in addition to degrading exogenous LPA, LPP1 controls signaling downstream of LPA receptors. Consistent with this conclusion, LPP1 expression decreased phospholipase D (PLD) stimulation by LPA and PDGF, and phosphatidate accumulation. This LPP1 effect was upstream of PLD activation in addition to the possible metabolism of phosphatidate to diacylglycerol. PLD(2) activation was necessary for LPA-, but not PDGF-induced migration. Increased LPP1 expression also decreased the LPA-, but not the PDGF-induced activation of important proteins involved in fibroblast migration. These included decreased LPA-induced activation of ERK and Rho, and the basal activities of Rac and Cdc42. However, ERK and Rho activation were not downstream targets of LPA-induced PLD(2) activity. We conclude that the intracellular actions of LPP1 play important functions in regulating LPA-induced fibroblast migration through PLD2. LPP1 also controls PDGF-induced phosphatidate formation. These results shed new light on the roles of LPP1 in controlling wound healing and the growth and metastasis of tumors.
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Affiliation(s)
- Carlos Pilquil
- Signal Transduction Research Group, Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2S2, Canada
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8
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Taylor MM, Macdonald K, Morris AJ, McMaster CR. Enhanced apoptosis through farnesol inhibition of phospholipase D signal transduction. FEBS J 2005; 272:5056-63. [PMID: 16176276 DOI: 10.1111/j.1742-4658.2005.04914.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Farnesol is a catabolite of the cholesterol biosynthetic pathway that preferentially causes apoptosis in tumorigenic cells. Phosphatidylcholine (PC), phosphatidic acid (PA), and diacylglycerol (DAG) were able to prevent induction of apoptosis by farnesol. Primary alcohol inhibition of PC catabolism by phospholipase D augmented farnesol-induced apoptosis. Exogenous PC was unable to prevent the increase in farnesol-induced apoptosis by primary alcohols, whereas DAG was protective. Farnesol-mediated apoptosis was prevented by transformation with a plasmid coding for the PA phosphatase LPP3, but not by an inactive LPP3 point mutant. Farnesol did not directly inhibit LPP3 PA phosphatase enzyme activity in an in vitro mixed micelle assay. We propose that farnesol inhibits the action of a DAG pool generated by phospholipase D signal transduction that normally activates an antiapoptotic/pro-proliferative target.
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Affiliation(s)
- Marcia M Taylor
- Atlantic Research Centre, Dalhousie University, Halifax, Canada
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9
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Zhao Y, Usatyuk P, Cummings R, Saatian B, He D, Watkins T, Morris A, Spannhake E, Brindley D, Natarajan V. Lipid phosphate phosphatase-1 regulates lysophosphatidic acid-induced calcium release, NF-kappaB activation and interleukin-8 secretion in human bronchial epithelial cells. Biochem J 2005; 385:493-502. [PMID: 15461590 PMCID: PMC1134721 DOI: 10.1042/bj20041160] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
LPA (lysophosphatidic acid), a potent bioactive phospholipid, elicits diverse cellular responses through activation of the G-protein-coupled receptors LPA1-LPA4. LPA-mediated signalling is partially regulated by LPPs (lipid phosphate phosphatases; LPP-1, -2 and -3) that belong to the phosphatase superfamily. This study addresses the role of LPPs in regulating LPA-mediated cell signalling and IL-8 (interleukin-8) secretion in HBEpCs (human bronchial epithelial cells). Reverse transcription-PCR and Western blotting revealed the presence and expression of LPP-1-3 in HBEpCs. Exogenous [3H]oleoyl LPA was hydrolysed to [3H]-mono-oleoylglycerol. Infection of HBEpCs with an adenoviral construct of human LPP-1 for 48 h enhanced the dephosphorylation of exogenous LPA by 2-3-fold compared with vector controls. Furthermore, overexpression of LPP-1 partially attenuated LPA-induced increases in the intracellular Ca2+ concentration, phosphorylation of IkappaB (inhibitory kappaB) and translocation of NF-kappaB (nuclear factor-kappaB) to the nucleus, and almost completely prevented IL-8 secretion. Infection of cells with an adenoviral construct of the mouse LPP-1 (R217K) mutant partially attenuated LPA-induced IL-8 secretion without altering LPA-induced changes in intracellular Ca2+ concentration, phosphorylation of IkappaB, NF-kappaB activation or IL-8 gene expression. Our results identify LPP-1 as a key regulator of LPA signalling and IL-8 secretion in HBEpCs. Thus LPPs could represent potential targets in regulating leucocyte infiltration and airway inflammation.
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Affiliation(s)
- Yutong Zhao
- *Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21222, U.S.A
| | - Peter V. Usatyuk
- *Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21222, U.S.A
| | - Rhett Cummings
- *Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21222, U.S.A
| | - Bahman Saatian
- *Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21222, U.S.A
| | - Donghong He
- *Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21222, U.S.A
| | - Tonya Watkins
- *Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21222, U.S.A
| | - Andrew Morris
- †Department of Cell Biology, University of North Carolina, Chapel Hill, NC, U.S.A
| | - Ernst Wm. Spannhake
- ‡Department of Environmental Health Sciences, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, U.S.A
| | - David N. Brindley
- §Department of Biochemistry and Signal Transduction Research Group, University of Alberta, Edmonton, Canada
| | - Viswanathan Natarajan
- *Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21222, U.S.A
- To whom correspondence should be addressed: Division of Pulmonary and Critical Care, Johns Hopkins University Medical School, Mason F. Lord Building, Center Tower, 675, 5200 Eastern Avenue, Baltimore, MD, U.S.A. (email )
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10
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Brindley DN. Lipid phosphate phosphatases and related proteins: signaling functions in development, cell division, and cancer. J Cell Biochem 2005; 92:900-12. [PMID: 15258914 DOI: 10.1002/jcb.20126] [Citation(s) in RCA: 198] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Lipid phosphates initiate key signaling cascades in cell activation. Lysophosphatidate (LPA) and sphingosine 1-phosphate (S1P) are produced by activated platelets. LPA is also formed from circulating lysophosphatidylcholine by autotaxin, a protein involved tumor progression and metastasis. Extracellular LPA and S1P stimulate families of G-protein coupled receptors that elicit diverse responses. LPA is involved in wound repair and tumor growth. Exogenous S1P is a potent stimulator of angiogenesis, a process vital in development, tissue repair and the growth of aggressive tumors. Inside the cell, phosphatidate (PA), ceramide 1-phosphate (C1P), LPA, and S1P act as signaling molecules with distinct functions including the stimulation of cell division, cytoskeletal rearrangement, Ca(2+) transients, and membrane movement. These observations imply that phosphatases that degrade lipid phosphates on the cell surface, or inside the cell, regulate cell signaling under physiological and pathological conditions. This occurs through attenuation of signaling by the lipid phosphates and by the production of bioactive products (diacylglycerol, ceramide, and sphingosine). Three lipid phosphate phosphatases (LPPs) and a splice variant dephosphorylate LPA, PA, CIP, and S1P. Two S1P phosphatases (SPPs) act specifically on S1P. In addition, there is family of four LPP-related proteins (LPRs, or plasticity-related genes, PRGs). PRG-1 expression in neurons has been reported to increase extracellular LPA breakdown and attenuate LPA-induced axonal retraction. It is unclear whether the LRPs dephosphorylate LPA directly, stimulate LPP activity, or bind LPA and S1P. Also, the importance of extra- versus intra-cellular actions of the LPPs and SPPs, and the individual roles of different isoforms is not firmly established. Understanding the functions and regulation of the LPPs, SPPs and related proteins will hopefully contribute to interventions to correct dysfunctions in conditions such as wound repair, inflammation, angiogenesis, tumor growth, and metastasis.
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Affiliation(s)
- David N Brindley
- Signal Transduction Research Group, Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2S2.
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11
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Abstract
The lysophospholipids, lysophosphatidic acid (LPA) and sphingosine 1-phosphate (S1P), regulate various signaling pathways within cells by binding to multiple G protein-coupled receptors. Receptor-mediated LPA and S1P signaling induces diverse cellular responses including proliferation, adhesion, migration, morphogenesis, differentiation and survival. This review will focus on major components of lysophospholipid signaling: metabolism, identification and expression of LPA and S1P receptors, general signaling pathways and specific signaling mechanisms in mouse embryonic fibroblasts. Finally, in vivo effects of LP receptor gene deletion in mice will be discussed.
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Affiliation(s)
- Brigitte Anliker
- Department of Molecular Biology, Helen L. Dorris Institute for Neurological and Psychiatric Disorders, The Scripps Research Institute, 10550 North Torrey Pines Rd., La Jolla, CA 92037, USA.
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12
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Dawson J, Hotchin N, Lax S, Rumsby M. Lysophosphatidic acid induces process retraction in CG-4 line oligodendrocytes and oligodendrocyte precursor cells but not in differentiated oligodendrocytes. J Neurochem 2004; 87:947-57. [PMID: 14622125 DOI: 10.1046/j.1471-4159.2003.02056.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Lysophosphatidic acid is a growth factor-like signalling phospholipid. We demonstrate here that lysophosphatidic acid induces process retraction in central glia-4 cells and oligodendrocyte precursors. This lysophosphatidic acid effect is rapid and concentration-dependent and results in cell rounding. It is inhibited by pre-treatment of cells with C3 exoenzyme, a specific inhibitor of Rho, or with Y-27632, a specific inhibitor of ROCK, a downstream kinase of Rho. Processes of differentiated central glia-4 oligodendrocytes were insensitive to lysophosphatidic acid treatment but cell bodies became phase dark, indicating cell spreading on the poly-l-lysine substratum. RT-PCR and Western blot analyses indicate that oligodendrocyte precursors and mature oligodendrocytes express mRNA and protein for LPA1, one of several LPA receptors. Thus lysophosphatidic acid may be signalling to Rho and stimulating actomyosin contraction in precursor oligodendrocytes by this family of receptors. The results show that lysophosphatidic acid signalling pathways influence retraction of processes in oligodendrocyte precursors but that this effect changes as oligodendrocytes differentiate.
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Affiliation(s)
- John Dawson
- Department of Biology, University of York, York, UK.
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Smyth SS, Sciorra VA, Sigal YJ, Pamuklar Z, Wang Z, Xu Y, Prestwich GD, Morris AJ. Lipid phosphate phosphatases regulate lysophosphatidic acid production and signaling in platelets: studies using chemical inhibitors of lipid phosphate phosphatase activity. J Biol Chem 2003; 278:43214-23. [PMID: 12909631 DOI: 10.1074/jbc.m306709200] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Blood platelets play an essential role in ischemic heart disease and stroke contributing to acute thrombotic events by release of potent inflammatory agents within the vasculature. Lysophosphatidic acid (LPA) is a bioactive lipid mediator produced by platelets and found in the blood and atherosclerotic plaques. LPA receptors on platelets, leukocytes, endothelial cells, and smooth muscle cells regulate growth, differentiation, survival, motility, and contractile activity. Definition of the opposing pathways of synthesis and degradation that control extracellular LPA levels is critical to understanding how LPA bioactivity is regulated. We show that intact platelets and platelet membranes actively dephosphorylate LPA and identify the major enzyme responsible as lipid phosphate phosphatase 1 (LPP1). Localization of LPP1 to the platelet surface is increased by exposure to LPA. A novel receptor-inactive sn-3-substituted difluoromethylenephosphonate analog of phosphatidic acid that is a potent competitive inhibitor of LPP1 activity potentiates platelet aggregation and shape change responses to LPA and amplifies LPA production by agonist-stimulated platelets. Our results identify LPP1 as a pivotal regulator of LPA signaling in the cardiovascular system. These findings are consistent with genetic and cell biological evidence implicating LPPs as negative regulators of lysophospholipid signaling and suggest that the mechanisms involve both attenuation of lysophospholipid actions at cell surface receptors and opposition of lysophospholipid production.
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Affiliation(s)
- Susan S Smyth
- Howard Hughes Medical Institute, University of California, San Diego, La Jolla, California 92093-0668, USA
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Aoki J, Taira A, Takanezawa Y, Kishi Y, Hama K, Kishimoto T, Mizuno K, Saku K, Taguchi R, Arai H. Serum lysophosphatidic acid is produced through diverse phospholipase pathways. J Biol Chem 2002; 277:48737-44. [PMID: 12354767 DOI: 10.1074/jbc.m206812200] [Citation(s) in RCA: 332] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Lysophosphatidic acid (LPA) is a lipid mediator with multiple biological activities that accounts for many biological properties of serum. LPA is thought to be produced during serum formation based on the fact that the LPA level is much higher in serum than in plasma. In this study, to better understand the pathways of LPA synthesis in serum, we evaluated the roles of platelets, plasma, and phospholipases by measuring LPA using a novel enzyme-linked fluorometric assay. First, examination of platelet-depleted rats showed that half of the LPA in serum is produced via a platelet-dependent pathway. However, the amount of LPA released from isolated platelets after they are activated by thrombin or calcium ionophore accounted for only a small part of serum LPA. Most of the platelet-derived LPA was produced in a two-step process: lysophospholipids such as lysophosphatidylcholine (LPC), lysophosphatidylethanolamine, and lysophosphatidylserine, were released from activated rat platelets by the actions of two phospholipases, group IIA secretory phospholipase A(2) (sPLA(2)-IIA) and phosphatidylserine-specific phospholipase A(1) (PS-PLA(1)), which were abundantly expressed in the cells. Then these lysophospholipids were converted to LPA by the action of plasma lysophospholipase D (lysoPLD). Second, accumulation of LPA in incubated plasma was strongly accelerated by the addition of recombinant lysoPLD with a concomitant decrease in LPC accumulation, indicating that the enzyme produces LPA by hydrolyzing LPC produced during the incubation. In addition, incubation of plasma isolated from human subjects who were deficient in lecithin-cholesterol acyltransferase (LCAT) did not result in increases of either LPC or LPA. The present study demonstrates multiple pathways for LPA production in serum and the involvement of several phospholipases, including PS-PLA(1), sPLA(2)-IIA, LCAT, and lysoPLD.
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Affiliation(s)
- Junken Aoki
- Graduate School of Pharmaceutical Sciences, the University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Japan.
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15
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Gueguen G, Granci V, Rogalle P, Briand-Mésange F, Wilson M, Klaébé A, Tercé F, Chap H, Salles JP, Simon MF, Gaits F. A lysophosphatidic acid analogue is revealed as a potent inhibitor of phosphatidylcholine synthesis, inducing apoptosis. Biochem J 2002; 368:447-59. [PMID: 12197836 PMCID: PMC1223009 DOI: 10.1042/bj20020273] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2002] [Revised: 08/01/2002] [Accepted: 08/28/2002] [Indexed: 01/15/2023]
Abstract
A previous study demonstrated that cross-desensitization experiments performed with the lysophosphatidic acid (LPA) analogues (R)- and (S)-N-palmitoyl-norleucinol 1-phosphate (PNPAs) inhibited LPA-induced platelet aggregation without any stereospecificity. Here we report opposite biological effects of the two enantiomers on mitogenesis of IMR-90 fibroblasts in relation to their respective metabolism. (R)PNPA was proliferative, while (S)PNPA induced apoptosis by specifically inhibiting phosphatidylcholine biosynthesis at the last step of the CDP-choline pathway controlled by cholinephosphotransferase. This effect was not direct but required dephosphorylation of PNPAs by ecto-lipid phosphate phosphatase before cellular uptake of the generated N-palmitoyl-norleucinols (PNOHs). Inhibition of cholinephosphotransferase by the derivative (S)PNOH was confirmed by an in vitro assay. (S)PNPA proapoptotic effects led us to clarify the mechanism linking cholinephosphotransferase inhibition to apoptosis. Three proapoptotic responses were observed: the activation of caspase-3, the production of ceramides from newly synthesized pools (as demonstrated by the inhibitor Fumonisin B1) and finally the activation of stress-activated protein kinase, p38 and c-Jun N-terminal kinases 1/2, as a result of ceramide increase. Thus our data demonstrate that synthetic analogues of LPA might display stereospecific effects leading to apoptosis independently of classical LPA-activated pathways.
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Affiliation(s)
- Geneviéve Gueguen
- Institut fédératif de recherche Claude de Préval, INSERM U326, Phospholipides membranaires, Signalisation cellulaire et Lipoprotéines, Hôpital Purpan, 31059 Toulouse Cedex, France
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Lu J, Xiao YJ, Baudhuin LM, Hong G, Xu Y. Role of ether-linked lysophosphatidic acids in ovarian cancer cells. J Lipid Res 2002. [DOI: 10.1016/s0022-2275(20)30153-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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