1
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Liu J, Tan J, Tang B, Guo J. Unveiling the role of iPLA 2β in neurodegeneration: From molecular mechanisms to advanced therapies. Pharmacol Res 2024; 202:107114. [PMID: 38395207 DOI: 10.1016/j.phrs.2024.107114] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/18/2023] [Revised: 02/08/2024] [Accepted: 02/20/2024] [Indexed: 02/25/2024]
Abstract
Calcium-independent phospholipase A2β (iPLA2β), a member of the phospholipase A2 (PLA2s) superfamily, is encoded by the PLA2G6 gene. Mutations in the PLA2G6 gene have been identified as the primary cause of infantile neuroaxonal dystrophy (INAD) and, less commonly, as a contributor to Parkinson's disease (PD). Recent studies have revealed that iPLA2β deficiency leads to neuroinflammation, iron accumulation, mitochondrial dysfunction, lipid dysregulation, and other pathological changes, forming a complex pathogenic network. These discoveries shed light on potential mechanisms underlying PLA2G6-associated neurodegeneration (PLAN) and offer valuable insights for therapeutic development. This review provides a comprehensive analysis of the fundamental characteristics of iPLA2β, its association with neurodegeneration, the pathogenic mechanisms involved in PLAN, and potential targets for therapeutic intervention. It offers an overview of the latest advancements in this field, aiming to contribute to ongoing research endeavors and facilitate the development of effective therapies for PLAN.
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Affiliation(s)
- Jiabin Liu
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Jieqiong Tan
- Centre for Medical Genetics and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410008, China
| | - Beisha Tang
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan, China; Department of Geriatrics, Xiangya Hospital, Central South University, Changsha, Hunan, China; National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Jifeng Guo
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan, China; Centre for Medical Genetics and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410008, China; National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, Hunan, China.
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2
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Sugihara R, Taneike M, Murakawa T, Tamai T, Ueda H, Kitazume-Taneike R, Oka T, Akazawa Y, Nishida H, Mine K, Hioki A, Omi J, Omiya S, Aoki J, Ikeda K, Nishida K, Arita M, Yamaguchi O, Sakata Y, Otsu K. Lysophosphatidylserine induces necrosis in pressure overloaded male mouse hearts via G protein coupled receptor 34. Nat Commun 2023; 14:4494. [PMID: 37524709 PMCID: PMC10390482 DOI: 10.1038/s41467-023-40201-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Accepted: 07/17/2023] [Indexed: 08/02/2023] Open
Abstract
Heart failure is a leading cause of mortality in developed countries. Cell death is a key player in the development of heart failure. Calcium-independent phospholipase A2β (iPLA2β) produces lipid mediators by catalyzing lipids and induces nuclear shrinkage in caspase-independent cell death. Here, we show that lysophosphatidylserine generated by iPLA2β induces necrotic cardiomyocyte death, as well as contractile dysfunction mediated through its receptor, G protein-coupled receptor 34 (GPR34). Cardiomyocyte-specific iPLA2β-deficient male mice were subjected to pressure overload. While control mice showed left ventricular systolic dysfunction with necrotic cardiomyocyte death, iPLA2β-deficient mice preserved cardiac function. Lipidomic analysis revealed a reduction of 18:0 lysophosphatidylserine in iPLA2β-deficient hearts. Knockdown of Gpr34 attenuated 18:0 lysophosphatidylserine-induced necrosis in neonatal male rat cardiomyocytes, while the ablation of Gpr34 in male mice reduced the development of pressure overload-induced cardiac remodeling. Thus, the iPLA2β-lysophosphatidylserine-GPR34-necrosis signaling axis plays a detrimental role in the heart in response to pressure overload.
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Affiliation(s)
- Ryuta Sugihara
- Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Manabu Taneike
- Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Tomokazu Murakawa
- Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Takahito Tamai
- Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Hiromichi Ueda
- Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka, 565-0871, Japan
- Preventive Diagnostics, Department of Biomedical Informatics, Division of Health Sciences, Osaka University Graduate School of Medicine, 1-7 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Rika Kitazume-Taneike
- Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Takafumi Oka
- Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Yasuhiro Akazawa
- Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Hiroki Nishida
- Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Kentaro Mine
- Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Ayana Hioki
- Preventive Diagnostics, Department of Biomedical Informatics, Division of Health Sciences, Osaka University Graduate School of Medicine, 1-7 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Jumpei Omi
- Department of Health Chemistry, Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Shigemiki Omiya
- The School of Cardiovascular Medicine and Sciences, King's College London British Heart Foundation Centre of Excellence, 125 Coldharbour Lane, London, SE5 9NU, UK
- National Cerebral and Cardiovascular Center, 6-1 Kishibe-Shinmachi, Suita, Osaka, 564-8565, Japan
| | - Junken Aoki
- Department of Health Chemistry, Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Kazutaka Ikeda
- Laboratory for Metabolomics, RIKEN Center for Integrative Medical Sciences (IMS), 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama City, Kanagawa, 230-0045, Japan
- Cellular and Molecular Epigenetics Laboratory, Graduate School of Medical Life Science, Yokohama-City University, 1-7-29 Suehiro-cho, Tsurumi-ku, Yokohama City, Kanagawa, 230-0045, Japan
| | - Kazuhiko Nishida
- The School of Cardiovascular Medicine and Sciences, King's College London British Heart Foundation Centre of Excellence, 125 Coldharbour Lane, London, SE5 9NU, UK
| | - Makoto Arita
- Laboratory for Metabolomics, RIKEN Center for Integrative Medical Sciences (IMS), 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama City, Kanagawa, 230-0045, Japan
- Cellular and Molecular Epigenetics Laboratory, Graduate School of Medical Life Science, Yokohama-City University, 1-7-29 Suehiro-cho, Tsurumi-ku, Yokohama City, Kanagawa, 230-0045, Japan
- Division of Physiological Chemistry and Metabolism, Keio University Faculty of Pharmacy, 1-5-30 Shibakoen, Minato-ku, Tokyo, 105-8512, Japan
| | - Osamu Yamaguchi
- Department of Cardiology, Pulmonology, Hypertension & Nephrology, Ehime University Graduate School of Medicine, 454 Shitsukawa, Toon, Ehime, 791-0295, Japan
| | - Yasushi Sakata
- Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Kinya Otsu
- The School of Cardiovascular Medicine and Sciences, King's College London British Heart Foundation Centre of Excellence, 125 Coldharbour Lane, London, SE5 9NU, UK.
- National Cerebral and Cardiovascular Center, 6-1 Kishibe-Shinmachi, Suita, Osaka, 564-8565, Japan.
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3
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Ramanadham S, Turk J, Bhatnagar S. Noncanonical Regulation of cAMP-Dependent Insulin Secretion and Its Implications in Type 2 Diabetes. Compr Physiol 2023; 13:5023-5049. [PMID: 37358504 PMCID: PMC10809800 DOI: 10.1002/cphy.c220031] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/27/2023]
Abstract
Impaired glucose tolerance (IGT) and β-cell dysfunction in insulin resistance associated with obesity lead to type 2 diabetes (T2D). Glucose-stimulated insulin secretion (GSIS) from β-cells occurs via a canonical pathway that involves glucose metabolism, ATP generation, inactivation of K ATP channels, plasma membrane depolarization, and increases in cytosolic concentrations of [Ca 2+ ] c . However, optimal insulin secretion requires amplification of GSIS by increases in cyclic adenosine monophosphate (cAMP) signaling. The cAMP effectors protein kinase A (PKA) and exchange factor activated by cyclic-AMP (Epac) regulate membrane depolarization, gene expression, and trafficking and fusion of insulin granules to the plasma membrane for amplifying GSIS. The widely recognized lipid signaling generated within β-cells by the β-isoform of Ca 2+ -independent phospholipase A 2 enzyme (iPLA 2 β) participates in cAMP-stimulated insulin secretion (cSIS). Recent work has identified the role of a G-protein coupled receptor (GPCR) activated signaling by the complement 1q like-3 (C1ql3) secreted protein in inhibiting cSIS. In the IGT state, cSIS is attenuated, and the β-cell function is reduced. Interestingly, while β-cell-specific deletion of iPLA 2 β reduces cAMP-mediated amplification of GSIS, the loss of iPLA 2 β in macrophages (MØ) confers protection against the development of glucose intolerance associated with diet-induced obesity (DIO). In this article, we discuss canonical (glucose and cAMP) and novel noncanonical (iPLA 2 β and C1ql3) pathways and how they may affect β-cell (dys)function in the context of impaired glucose intolerance associated with obesity and T2D. In conclusion, we provide a perspective that in IGT states, targeting noncanonical pathways along with canonical pathways could be a more comprehensive approach for restoring β-cell function in T2D. © 2023 American Physiological Society. Compr Physiol 13:5023-5049, 2023.
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Affiliation(s)
- Sasanka Ramanadham
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Alabama, USA
- Comprehensive Diabetes Center, University of Alabama at Birmingham, Alabama, USA
| | - John Turk
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Sushant Bhatnagar
- Comprehensive Diabetes Center, University of Alabama at Birmingham, Alabama, USA
- Department of Medicine, University of Alabama at Birmingham, Alabama, USA
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4
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Turk J, White TD, Nelson AJ, Lei X, Ramanadham S. iPLA 2β and its role in male fertility, neurological disorders, metabolic disorders, and inflammation. Biochim Biophys Acta Mol Cell Biol Lipids 2018; 1864:846-860. [PMID: 30408523 DOI: 10.1016/j.bbalip.2018.10.010] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2018] [Revised: 10/26/2018] [Accepted: 10/29/2018] [Indexed: 02/06/2023]
Abstract
The Ca2+-independent phospholipases, designated as group VI iPLA2s, also referred to as PNPLAs due to their shared homology with patatin, include the β, γ, δ, ε, ζ, and η forms of the enzyme. The iPLA2s are ubiquitously expressed, share a consensus GXSXG catalytic motif, and exhibit organelle/cell-specific localization. Among the iPLA2s, iPLA2β has received wide attention as it is recognized to be involved in membrane remodeling, cell proliferation, cell death, and signal transduction. Ongoing studies implicate participation of iPLA2β in a variety of disease processes including cancer, cardiovascular abnormalities, glaucoma, and peridonditis. This review will focus on iPLA2β and its links to male fertility, neurological disorders, metabolic disorders, and inflammation.
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Affiliation(s)
- John Turk
- Department of Medicine, Washington University School of Medicine, St. Louis, MO, United States of America
| | - Tayleur D White
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, United States of America; Comprehensive Diabetes Center, University of Alabama at Birmingham, Birmingham, AL, United States of America
| | - Alexander J Nelson
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, United States of America; Comprehensive Diabetes Center, University of Alabama at Birmingham, Birmingham, AL, United States of America
| | - Xiaoyong Lei
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, United States of America; Comprehensive Diabetes Center, University of Alabama at Birmingham, Birmingham, AL, United States of America
| | - Sasanka Ramanadham
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, United States of America; Comprehensive Diabetes Center, University of Alabama at Birmingham, Birmingham, AL, United States of America.
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5
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Malley KR, Koroleva O, Miller I, Sanishvili R, Jenkins CM, Gross RW, Korolev S. The structure of iPLA 2β reveals dimeric active sites and suggests mechanisms of regulation and localization. Nat Commun 2018; 9:765. [PMID: 29472584 PMCID: PMC5823874 DOI: 10.1038/s41467-018-03193-0] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Accepted: 01/26/2018] [Indexed: 11/17/2022] Open
Abstract
Calcium-independent phospholipase A2β (iPLA2β) regulates important physiological processes including inflammation, calcium homeostasis and apoptosis. It is genetically linked to neurodegenerative disorders including Parkinson’s disease. Despite its known enzymatic activity, the mechanisms underlying iPLA2β-induced pathologic phenotypes remain poorly understood. Here, we present a crystal structure of iPLA2β that significantly revises existing mechanistic models. The catalytic domains form a tight dimer. They are surrounded by ankyrin repeat domains that adopt an outwardly flared orientation, poised to interact with membrane proteins. The closely integrated active sites are positioned for cooperative activation and internal transacylation. The structure and additional solution studies suggest that both catalytic domains can be bound and allosterically inhibited by a single calmodulin. These features suggest mechanisms of iPLA2β cellular localization and activity regulation, providing a basis for inhibitor development. Furthermore, the structure provides a framework to investigate the role of neurodegenerative mutations and the function of iPLA2β in the brain. Calcium-independent phospholipase A2β (iPLA2β) is involved in many physiological and pathological processes but the underlying mechanisms are largely unknown. Here, the authors present the structure of dimeric iPLA2β, providing insights into the regulation of its activity and cellular localization.
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Affiliation(s)
- Konstantin R Malley
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO, 63104, USA
| | - Olga Koroleva
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO, 63104, USA
| | - Ian Miller
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO, 63104, USA
| | - Ruslan Sanishvili
- GM/CA@APS, Advanced Photon Source, Argonne National Laboratory, Argonne, IL, 60439, USA
| | - Christopher M Jenkins
- Division of Bioorganic Chemistry and Molecular Pharmacology, Department of Medicine, Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8020, Saint Louis, MO, 63110, USA
| | - Richard W Gross
- Division of Bioorganic Chemistry and Molecular Pharmacology, Department of Medicine, Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8020, Saint Louis, MO, 63110, USA.,Department of Developmental Biology, Washington University School of Medicine, Saint Louis, MO, 63110, USA.,Department of Medicine, Center for Cardiovascular Research, Washington University School of Medicine, Saint Louis, MO, 63110, USA.,Department of Chemistry, Washington University, Saint Louis, MO, 63130, USA
| | - Sergey Korolev
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO, 63104, USA.
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6
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Ramanadham S, Ali T, Ashley JW, Bone RN, Hancock WD, Lei X. Calcium-independent phospholipases A2 and their roles in biological processes and diseases. J Lipid Res 2015; 56:1643-68. [PMID: 26023050 DOI: 10.1194/jlr.r058701] [Citation(s) in RCA: 135] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Indexed: 12/24/2022] Open
Abstract
Among the family of phospholipases A2 (PLA2s) are the Ca(2+)-independent PLA2s (iPLA2s) and they are designated group VI iPLA2s. In relation to secretory and cytosolic PLA2s, the iPLA2s are more recently described and details of their expression and roles in biological functions are rapidly emerging. The iPLA2s or patatin-like phospholipases (PNPLAs) are intracellular enzymes that do not require Ca(2+) for activity, and contain lipase (GXSXG) and nucleotide-binding (GXGXXG) consensus sequences. Though nine PNPLAs have been recognized, PNPLA8 (membrane-associated iPLA2γ) and PNPLA9 (cytosol-associated iPLA2β) are the most widely studied and understood. The iPLA2s manifest a variety of activities in addition to phospholipase, are ubiquitously expressed, and participate in a multitude of biological processes, including fat catabolism, cell differentiation, maintenance of mitochondrial integrity, phospholipid remodeling, cell proliferation, signal transduction, and cell death. As might be expected, increased or decreased expression of iPLA2s can have profound effects on the metabolic state, CNS function, cardiovascular performance, and cell survival; therefore, dysregulation of iPLA2s can be a critical factor in the development of many diseases. This review is aimed at providing a general framework of the current understanding of the iPLA2s and discussion of the potential mechanisms of action of the iPLA2s and related involved lipid mediators.
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Affiliation(s)
- Sasanka Ramanadham
- Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL 35294 Comprehensive Diabetes Center, University of Alabama at Birmingham, Birmingham, AL 35294
| | - Tomader Ali
- Undergraduate Research Office, University of Alabama at Birmingham, Birmingham, AL 35294
| | - Jason W Ashley
- Department of Orthopaedic Surgery, University of Pennsylvania, Philadelphia, PA 19104
| | - Robert N Bone
- Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL 35294 Comprehensive Diabetes Center, University of Alabama at Birmingham, Birmingham, AL 35294
| | - William D Hancock
- Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL 35294 Comprehensive Diabetes Center, University of Alabama at Birmingham, Birmingham, AL 35294
| | - Xiaoyong Lei
- Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL 35294 Comprehensive Diabetes Center, University of Alabama at Birmingham, Birmingham, AL 35294
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7
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Calderon LE, Liu S, Su W, Xie Z, Guo Z, Eberhard W, Gong MC. iPLA2β overexpression in smooth muscle exacerbates angiotensin II-induced hypertension and vascular remodeling. PLoS One 2012; 7:e31850. [PMID: 22363752 PMCID: PMC3282780 DOI: 10.1371/journal.pone.0031850] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2011] [Accepted: 01/13/2012] [Indexed: 12/12/2022] Open
Abstract
Objectives Calcium independent group VIA phospholipase A2 (iPLA2β) is up-regulated in vascular smooth muscle cells in some diseases, but whether the up-regulated iPLA2β affects vascular morphology and blood pressure is unknown. The current study addresses this question by evaluating the basal- and angiotensin II infusion-induced vascular remodeling and hypertension in smooth muscle specific iPLA2β transgenic (iPLA2β -Tg) mice. Method and Results Blood pressure was monitored by radiotelemetry and vascular remodeling was assessed by morphologic analysis. We found that the angiotensin II-induced increase in diastolic pressure was significantly higher in iPLA2β-Tg than iPLA2β-Wt mice, whereas, the basal blood pressure was not significantly different. The media thickness and media∶lumen ratio of the mesenteric arteries were significantly increased in angiotensin II-infused iPLA2β-Tg mice. Analysis revealed no difference in vascular smooth muscle cell proliferation. In contrast, adenovirus-mediated iPLA2β overexpression in cultured vascular smooth muscle cells promoted angiotensin II-induced [3H]-leucine incorporation, indicating enhanced hypertrophy. Moreover, angiotensin II infusion-induced c-Jun phosphorylation in vascular smooth muscle cells overexpressing iPLA2β to higher levels, which was abolished by inhibition of 12/15 lipoxygenase. In addition, we found that angiotensin II up-regulated the endogenous iPLA2β protein in-vitro and in-vivo. Conclusion The present study reports that iPLA2β up-regulation exacerbates angiotensin II-induced vascular smooth muscle cell hypertrophy, vascular remodeling and hypertension via the 12/15 lipoxygenase and c-Jun pathways.
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MESH Headings
- Angiotensin II/administration & dosage
- Angiotensin II/pharmacology
- Animals
- Aorta, Thoracic/drug effects
- Aorta, Thoracic/physiopathology
- Arachidonate 15-Lipoxygenase
- Arachidonic Acid/metabolism
- Blood Pressure/drug effects
- Cell Proliferation/drug effects
- Diastole/drug effects
- Group VI Phospholipases A2/metabolism
- Hypertension/enzymology
- Hypertension/pathology
- Hypertension/physiopathology
- Hypertrophy
- Leucine/metabolism
- Mesenteric Arteries/drug effects
- Mesenteric Arteries/physiopathology
- Mice
- Mice, Inbred C57BL
- Mice, Transgenic
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/enzymology
- Muscle, Smooth, Vascular/pathology
- Muscle, Smooth, Vascular/physiopathology
- Myocytes, Smooth Muscle/drug effects
- Myocytes, Smooth Muscle/enzymology
- Myocytes, Smooth Muscle/pathology
- Organ Specificity/drug effects
- Proto-Oncogene Proteins c-jun/metabolism
- Rats
- Signal Transduction/drug effects
- p38 Mitogen-Activated Protein Kinases/metabolism
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Affiliation(s)
- Lindsay E. Calderon
- Department of Molecular and Biomedical Pharmacology, University of Kentucky, Lexington, Kentucky, United States of America
| | - Shu Liu
- Department of Internal Medicine, University of Kentucky, Lexington, Kentucky, United States of America
| | - Wen Su
- Department of Internal Medicine, University of Kentucky, Lexington, Kentucky, United States of America
| | - Zhongwen Xie
- Department of Physiology, University of Kentucky, Lexington, Kentucky, United States of America
| | - Zhenheng Guo
- Department of Internal Medicine, University of Kentucky, Lexington, Kentucky, United States of America
| | - Wanda Eberhard
- Department of Physiology, University of Kentucky, Lexington, Kentucky, United States of America
| | - Ming C. Gong
- Department of Physiology, University of Kentucky, Lexington, Kentucky, United States of America
- * E-mail:
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8
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Jeong EM, Ahn KH, Jeon HJ, Kim HD, Lee HS, Jung SY, Jung KM, Kim SK, Bonventre JV, Kim DK. Purification and characterization of a cytosolic Ca(2+)-independent phospholipase A(2) from bovine brain. Mol Cells 2011; 32:405-13. [PMID: 21874539 PMCID: PMC3887695 DOI: 10.1007/s10059-011-1058-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2011] [Revised: 06/13/2011] [Accepted: 07/01/2011] [Indexed: 02/02/2023] Open
Abstract
The Ca(2+)-independent phospholipase A(2) (iPLA(2)) subfamily of enzymes is associated with arachidonic acid (AA) release and the subsequent increase in fatty acid turnover. This phenomenon occurs not only during apoptosis but also during inflammation and lymphocyte proliferation. In this study, we purified and characterized a novel type of iPLA(2) from bovine brain. iPLA(2) was purified 4,174-fold from the bovine brain by a sequential process involving DEAE-cellulose anion exchange, phenyl-5PW hydrophobic interaction, heparin-Sepharose affinity, Sephacryl S-300 gel filtration, Mono S cation exchange, Mono Q anion exchange, and Superose 12 gel filtration. A single peak of iPLA(2) activity was eluted at an apparent molecular mass of 155 kDa during the final Superose 12 gel-filtration step. The purified enzyme had an isoelectric point of 5.3 on two-dimensional gel electrophoresis (2-DE) and was inhibited by arachidonyl trifluoromethyl ketone (AACOCF(3)), Triton X-100, iron, and Ca(2+). However, it was not inhibited by bromoenol lactone (BEL), an inhibitor of iPLA(2), and adenosine triphosphate (ATP). The spot with the iPLA(2) activity did not match with any known protein sequence, as determined by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) analysis. Altogether, these data suggest that the purified enzyme is a novel form of cytosolic iPLA(2).
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Affiliation(s)
| | | | | | | | | | | | | | | | - Joseph V. Bonventre
- Medical Services, Brigham and Women’s Hospital, Harvard Medical School, Boston, Longwood, MA, USA
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9
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Phospholipase A2 mediates apolipoprotein-independent uptake of chylomicron remnant-like particles by human macrophages. Int J Vasc Med 2011; 2012:501954. [PMID: 21876814 PMCID: PMC3160105 DOI: 10.1155/2012/501954] [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: 04/13/2011] [Revised: 06/24/2011] [Accepted: 06/29/2011] [Indexed: 01/26/2023] Open
Abstract
Apolipoprotein E-receptor-mediated pathways are the main routes by which macrophages take up chylomicron remnants, but uptake may also be mediated by receptor-independent routes. To investigate these mechanisms, triacylglycerol (TG) accumulation induced by apolipoprotein-free chylomicron remnant-like particles (CRLPw/o) in human monocyte-derived macrophages was evaluated. Macrophage TG content increased about 5-fold after incubation with
CRLPw/o, and this effect was not reduced by the inhibition of phagocytosis, macropinocytosis, apolipoprotein E function, or proteoglycan bridging.
The role of lipases, including lipoprotein lipase, cholesteryl ester hydrolase, and secretory (sPLA2) and cytosolic phospholipase A2, was studied using [3H]TG-labelled CRLPw/o. Total cell radioactivity after incubation with [3H]TG CRLPw/o was reduced by 15–30% by inhibitors of lipoprotein lipase and cholesteryl ester hydrolase and by about 45% by inhibitors of sPLA2 and cytosolic PLA2 . These results suggest that macrophage lipolytic enzymes mediate the internalization of postprandial TG-rich lipoproteins and that sPLA2 and cytosolic PLA2, play a more important role than extracellular lipoprotein lipase-mediated TG hydrolysis.
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10
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Mancuso DJ, Sims HF, Yang K, Kiebish MA, Su X, Jenkins CM, Guan S, Moon SH, Pietka T, Nassir F, Schappe T, Moore K, Han X, Abumrad NA, Gross RW. Genetic ablation of calcium-independent phospholipase A2gamma prevents obesity and insulin resistance during high fat feeding by mitochondrial uncoupling and increased adipocyte fatty acid oxidation. J Biol Chem 2010; 285:36495-510. [PMID: 20817734 DOI: 10.1074/jbc.m110.115766] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Phospholipases are critical enzyme mediators participating in many aspects of cellular function through modulating the generation of lipid 2nd messengers, membrane physical properties, and cellular bioenergetics. Here, we demonstrate that mice null for calcium-independent phospholipase A(2)γ (iPLA(2)γ(-/-)) are completely resistant to high fat diet-induced weight gain, adipocyte hypertrophy, hyperinsulinemia, and insulin resistance, which occur in iPLA(2)γ(+/+) mice after high fat feeding. Notably, iPLA(2)γ(-/-) mice were lean, demonstrated abdominal lipodystrophy, and remained insulin-sensitive despite having a marked impairment in glucose-stimulated insulin secretion after high fat feeding. Respirometry of adipocyte explants from iPLA(2)γ(-/-) mice identified increased rates of oxidation of multiple different substrates in comparison with adipocyte explants from wild-type littermates. Shotgun lipidomics of adipose tissue from wild-type mice demonstrated the anticipated 2-fold increase in triglyceride content after high fat feeding. In sharp contrast, the adipocyte triglyceride content was identical in iPLA(2)γ(-/-) mice fed either a standard diet or a high fat diet. Respirometry of skeletal muscle mitochondria from iPLA(2)γ(-/-) mice demonstrated marked decreases in state 3 respiration using multiple substrates whose metabolism was uncoupled from ATP production. Shotgun lipidomics of skeletal muscle revealed a decreased content of cardiolipin with an altered molecular species composition thereby identifying the mechanism underlying mitochondrial uncoupling in the iPLA(2)γ(-/-) mouse. Collectively, these results identify iPLA(2)γ as an obligatory upstream enzyme that is necessary for efficient electron transport chain coupling and energy production through its participation in the alterations of cellular bioenergetics that promote the development of the metabolic syndrome.
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Affiliation(s)
- David J Mancuso
- Division of Bioorganic Chemistry and Molecular Pharmacology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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11
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Lei X, Barbour SE, Ramanadham S. Group VIA Ca2+-independent phospholipase A2 (iPLA2beta) and its role in beta-cell programmed cell death. Biochimie 2010; 92:627-37. [PMID: 20083151 DOI: 10.1016/j.biochi.2010.01.005] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2009] [Accepted: 01/11/2010] [Indexed: 01/09/2023]
Abstract
Activation of phospholipases A(2) (PLA(2)s) leads to the generation of biologically active lipid mediators that can affect numerous cellular events. The Group VIA Ca(2+)-independent PLA(2), designated iPLA(2)beta, is active in the absence of Ca(2+), activated by ATP, and inhibited by the bromoenol lactone suicide inhibitor (BEL). Over the past 10-15 years, studies using BEL have demonstrated that iPLA(2)beta participates in various biological processes and the recent availability of mice in which iPLA(2)beta expression levels have been genetically-modified are extending these findings. Work in our laboratory suggests that iPLA(2)beta activates a unique signaling cascade that promotes beta-cell apoptosis. This pathway involves iPLA(2)beta dependent induction of neutral sphingomyelinase, production of ceramide, and activation of the intrinsic pathway of apoptosis. There is a growing body of literature supporting beta-cell apoptosis as a major contributor to the loss of beta-cell mass associated with the onset and progression of Type 1 and Type 2 diabetes mellitus. This underscores a need to gain a better understanding of the molecular mechanisms underlying beta-cell apoptosis so that improved treatments can be developed to prevent or delay the onset and progression of diabetes mellitus. Herein, we offer a general review of Group VIA Ca(2+)-independent PLA(2) (iPLA(2)beta) followed by a more focused discussion of its participation in beta-cell apoptosis. We suggest that iPLA(2)beta-derived products trigger pathways which can lead to beta-cell apoptosis during the development of diabetes.
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Affiliation(s)
- Xiaoyong Lei
- Department of Medicine, Mass Spectrometry Resource and Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, MO 63110, USA
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12
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Coupled calcium and zinc dyshomeostasis and oxidative stress in cardiac myocytes and mitochondria of rats with chronic aldosteronism. J Cardiovasc Pharmacol 2009; 53:414-23. [PMID: 19333130 DOI: 10.1097/fjc.0b013e3181a15e77] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
A dyshomeostasis of extra- and intracellular Ca(2+) and Zn(2+) occurs in rats receiving chronic aldosterone/salt treatment (ALDOST). Herein, we hypothesized that the dyshomeostasis of intracellular Ca(2+) and Zn(2+) is intrinsically coupled that alters the redox state of cardiac myocytes and mitochondria, with Ca(2+) serving as a pro-oxidant and Zn(2+) as an antioxidant. Toward this end, we harvested hearts from rats receiving 4 weeks of ALDOST alone or cotreatment with either spironolactone (Spiro), an aldosterone receptor antagonist, or amlodipine (Amlod), an L-type Ca(2+) channel blocker, and from age/sex-matched untreated controls. In each group, we monitored cardiomyocyte [Ca(2+)]i and [Zn(2+)]i and mitochondrial [Ca(2+)]m and [Zn(2+)]m; biomarkers of oxidative stress and antioxidant defenses; expression of Zn transporters, Zip1 and ZnT-1; metallothionein-1, a Zn(2+)-binding protein; and metal response element transcription factor-1, a [Zn(2+)]i sensor and regulator of antioxidant defenses. Compared with controls, at 4-week ALDOST, we found the following: (a) increased [Ca(2+)]i and [Zn(2+)]i, together with increased [Ca(2+)]m and [Zn(2+)]m, each of which could be prevented by Spiro and attenuated with Amlod; (b) increased levels of 3-nitrotyrosine and 4-hydroxy-2-nonenal in cardiomyocytes, together with increased H(2)O(2) production, malondialdehyde, and oxidized glutathione in mitochondria that were coincident with increased activities of Cu/Zn superoxide dismutase and glutathione peroxidase; and (c) increased expression of metallothionein-1, Zip1 and ZnT-1, and metal response element transcription factor-1, attenuated by Spiro. Thus, an intrinsically coupled dyshomeostasis of intracellular Ca(2+) and Zn(2+) occurs in cardiac myocytes and mitochondria in rats receiving ALDOST, where it serves to alter their redox state through a respective induction of oxidative stress and generation of antioxidant defenses. The importance of therapeutic strategies that can uncouple these two divalent cations and modulate their ratio in favor of sustained antioxidant defenses is therefore suggested.
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13
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Moon SH, Jenkins CM, Mancuso DJ, Turk J, Gross RW. Smooth muscle cell arachidonic acid release, migration, and proliferation are markedly attenuated in mice null for calcium-independent phospholipase A2beta. J Biol Chem 2008; 283:33975-87. [PMID: 18927078 DOI: 10.1074/jbc.m805817200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Pharmacologic evidence suggests that the lipid products generated by one or more calcium-independent phospholipases A(2) (iPLA(2)s) participate in the regulation of vascular tone through smooth muscle cell (SMC) Ca(2+) signaling and the release of arachidonic acid. However, the recent identification of new members of the iPLA(2) family, each inhibitable by (E)-6-(bromomethylene)-3-(1-naphthalenyl)-2H-tetrahydropyran-2-one, has rendered definitive identification of the specific enzyme(s) mediating these processes difficult. Accordingly, we used iPLA(2)beta(-/-) mice to demonstrate that iPLA(2)beta is responsible for the majority of thapsigargin and ionophore (A23187)-induced arachidonic acid release from SMCs. Both thapsigargin and A23187 stimulated robust [(3)H]arachidonate (AA) release from wild-type aortic SMCs that was dramatically attenuated in iPLA(2)beta(-/-) mice (>80% reduction at 5 min; p < 0.01). Moreover, iPLA(2)beta(-/-) mice displayed defects in SMC Ca(2+) homeostasis and decreased SMC migration and proliferation in a model of vascular injury. Ca(2+)-store depletion resulted in the rapid entry of external Ca(2+) into wild-type aortic SMCs that was significantly slower in iPLA(2)beta-null cells (p < 0.01). Furthermore, SMCs from iPLA(2)beta-null mesenteric arterial explants demonstrated decreased proliferation and migration. The defects in migration and proliferation in iPLA(2)beta-null SMCs were restored by 2 mum AA. Remarkably, the cyclooxygenase-2-specific inhibitor, NS-398, prevented AA-induced rescue of SMC migration and proliferation in iPLA(2)beta(-/-) mice. Moreover, PGE(2) alone rescued proliferation and migration in iPLA(2)beta(-/-) mice. We conclude that iPLA(2)beta is an important mediator of AA release and prostaglandin E(2) production in SMCs, modulating vascular tone, cellular signaling, proliferation, and migration.
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Affiliation(s)
- Sung Ho Moon
- Division of Bioorganic Chemistry and Molecular Pharmacology, Endocrinology, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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van der Vusse GJ, van Bilsen M. Free Fatty acids and postischemic myocardial function. Semin Cardiothorac Vasc Anesth 2007; 10:231-5. [PMID: 16959757 DOI: 10.1177/1089253206291319] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
This review highlights the changes in fatty acid homeostasis in the postischemic heart. The impact of restoration of flow (reperfusion) after an ischemic episode on both structural fatty acids (ie, incorporated in phospholipids, the building blocks of cellular membranes) and fatty acids, serving as energy donors by mitochondrial oxidation, are discussed. Attempts to interfere with cardiac fatty acid homeostasis to prevent loss of cardiac function or to restore cardiac performance after reperfusion is also discussed.
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Affiliation(s)
- Ger J van der Vusse
- Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, The Netherlands.
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15
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Beckett CS, Pennington K, McHowat J. Activation of MAPKs in thrombin-stimulated ventricular myocytes is dependent on Ca2+-independent PLA2. Am J Physiol Cell Physiol 2006; 290:C1350-4. [PMID: 16338969 DOI: 10.1152/ajpcell.00487.2005] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Thrombin stimulation of isolated rabbit ventricular myocytes activates a membrane-associated, Ca2+-independent PLA2(iPLA2) that selectively hydrolyzes plasmalogen phospholipids and results in increased production of arachidonic acid and lysoplasmenylcholine. To determine whether MAPK regulates myocardial iPLA2activity, we isolated ventricular myocytes from rabbit heart by collagenase digestion and pretreated them with MAPK inhibitors before stimulating them with thrombin. Pretreatment with PD-98059 to inhibit p42/44 MAPK or SB-203580 to inhibit p38 MAPK had no significant effect on thrombin-stimulated, membrane-associated iPLA2activity. Thrombin stimulation resulted in significant increases in both p42/44 and p38 MAPK activity after 2 min. Pretreatment with the iPLA2-selective inhibitor bromoenol lactone completely inhibited thrombin-stimulated MAPK activity, suggesting that activation of MAPKs was dependent on iPLA2activation. Ventricular myocyte MAPK activity was increased by incubation of the myocytes with lysoplasmenylcholine, a metabolite produced by iPLA2-catalyzed membrane plasmalogen phospholipid hydrolysis. Altogether, these data suggest that activation of MAPKs occurs downstream of and is dependent on iPLA2activation in thrombin-stimulated rabbit ventricular myocytes.
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Affiliation(s)
- Caroline S Beckett
- Department of Pathology, St. Louis University School of Medicine, 1402 S. Grand Blvd., St. Louis, MO 63104, USA
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16
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Jenkins CM, Yan W, Mancuso DJ, Gross RW. Highly selective hydrolysis of fatty acyl-CoAs by calcium-independent phospholipase A2beta. Enzyme autoacylation and acyl-CoA-mediated reversal of calmodulin inhibition of phospholipase A2 activity. J Biol Chem 2006; 281:15615-24. [PMID: 16595686 DOI: 10.1074/jbc.m511623200] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Calcium-independent phospholipase A2beta (iPLA2beta) participates in numerous diverse cellular processes, such as arachidonic acid release, insulin secretion, calcium signaling, and apoptosis. Herein, we demonstrate the highly selective iPLA2beta-catalyzed hydrolysis of saturated long-chain fatty acyl-CoAs (palmitoyl-CoA approximately myristoyl-CoA >> stearoyl-CoA >> oleoyl-CoA approximately = arachidonoyl-CoA) present either as monomers in solution or guests in host membrane bilayers. Site-directed mutagenesis of the iPLA2beta catalytic serine (S465A) completely abolished acyl-CoA thioesterase activity, demonstrating that Ser-465 catalyzes both phospholipid and acyl-CoA hydrolysis. Remarkably, incubation of iPLA2beta with oleoyl-CoA, but not other long-chain acyl-CoAs, resulted in robust stoichiometric covalent acylation of the enzyme. Moreover, S465A mutagenesis or pretreatment of wild-type iPLA2beta with (E)-6-(bromomethylene)-3-(1-naphthalenyl)-2H-tetrahydropyran-2-one unexpectedly increased acylation of the enzyme, indicating the presence of a second reactive nucleophilic residue that participates in the formation of the fatty acyl-iPLA2beta adduct. Radiolabeling of intact Sf9 cells expressing iPLA2beta with [3H]oleic acid demonstrated oleoylation of the membrane-associated enzyme. Partial trypsinolysis of oleoylated iPLA2beta and matrix-assisted laser desorption ionization mass spectrometry analysis localized the acylation site to a hydrophobic 25-kDa fragment (residues approximately 400-600) spanning the active site to the calmodulin binding domain. Intriguingly, calmodulin-Ca2+ blocked acylation of iPLA2beta by oleoyl-CoA. Remarkably, the addition of low micromolar concentrations (5 microM) of oleoyl-CoA resulted in reversal of calmodulin-mediated inhibition of iPLA2 beta phospholipase A2 activity. These results collectively identify the molecular species-specific acyl-CoA thioesterase activity of iPLA2beta, demonstrate the presence of a second active site that mediates iPLA2beta autoacylation, and identify long-chain acyl-CoAs as potential candidates mediating calcium influx factor activity.
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Affiliation(s)
- Christopher M Jenkins
- Division of Bioorganic Chemistry and Molecular Pharmacology, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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Gross RW, Jenkins CM, Yang J, Mancuso DJ, Han X. Functional lipidomics: the roles of specialized lipids and lipid–protein interactions in modulating neuronal function. Prostaglandins Other Lipid Mediat 2005; 77:52-64. [PMID: 16099391 DOI: 10.1016/j.prostaglandins.2004.09.005] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2004] [Accepted: 09/14/2004] [Indexed: 11/18/2022]
Abstract
Lipids fulfill multiple specialized roles in neuronal function. In brain, the conduction of electrical impulses, synaptic function, and complex signaling pathways depend on the temporally and spatially coordinated interactions of specialized lipids (e.g., arachidonic acid and plasmalogens), proteins (e.g., ion channels, phospholipases and cyclooxygenases) and integrative lipid-protein interactions. Recent technical advances in mass spectrometry have allowed unparalled insight into the roles of lipids in neuronal function. Through shotgun lipidomics and multidimensional mass spectrometry, in conjunction with the identification of new classes of phospholipases (e.g., calcium dependent and calcium independent intracellular phospholipases), new roles for lipids in cerebral function have been accrued. This review summarizes the advances in our understanding of the types of lipids and phospholipases in the brain and the role of functional lipidomics in increasing our chemical understanding of complex neuronal processes.
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Affiliation(s)
- Richard W Gross
- Division of Bioorganic Chemistry and Molecular Pharmacology, Department of Medicine, Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8020, St. Louis, MO 63110, USA.
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18
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Tibes U, Friebe WG. Phospholipase A2 inhibitors in development. Expert Opin Investig Drugs 2005; 6:279-98. [PMID: 15989628 DOI: 10.1517/13543784.6.3.279] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
To date, three isoforms of phospholipase A2 (PLA2) have been identified. Of these, the two Ca2+-dependent isoforms, secretory (sPLA2) and cytosolic phospholipase A2 (cPLA2), are targets for new anti-inflammatory drugs. The catalytic mechanisms and functions of the third isoform, Ca2+-independent cytosolic phospholipase A2 (iPLA2), are unknown at present. sPLA2 and cPLA2 are both implicated in the release of arachidonic acid and prophlogistic lipid mediators. However, recent findings provide evidence that cPLA2 is the dominant isoform in various kinds of inflammation, such as T-cell-mediated experimental arthritis. A triple function of PLA2-derived lipid mediators has been suggested: causing immediate inflammatory signs, involvement in secondary processes, e.g., superoxide free radical (O2) generation, apoptosis, or tumour necrosis factor-alpha (TNF-alpha)-cytotoxicity, and controlling the expression and activation of pivotal proteins implicated in inflammation and cell development, e.g., cytokines, adhesion proteins, proteinases, NF-kappaB, fos/jun/AP-1, c-Myc, or p21ras. In the past, research predominantly focused on the development of sPLA2 inhibitors; however, present techniques enable discrimination of cPLA2, sPLA2, and iPLA2, and specific inhibitors of each of the three isoforms are likely to appear soon. Over the last decade, between 40 and 50 sPLA2 inhibitors have been described; and the list is growing. However, of these, few have the potential for clinical success, and those that do are predominantly active site-directed inhibitors, e.g., BMS-181162, LY311727, ARL-67974, FPL67047, SB-203347, Ro-23-9358, YM-26734, and IS-741. At present, there are no likely clinical candidates emerging from the ranks of cPLA2 and iPLA2 inhibitors in development. Indications for which PLA2 inhibitors are being pursued include, sepsis, acute pancreatitis, inflammatory skin and bowel diseases, asthma, and rheumatoid arthritis. The three main obstacles to the successful development of PLA2 inhibitors include, insufficient oral bioavailability, low affinity for the enzyme corresponding to low in vivo efficacy and insufficient selectivity.
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Affiliation(s)
- U Tibes
- Department of Preclinical Research, Boehringer Mannheim GmbH, Germany
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19
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Meyer MC, Kell PJ, Creer MH, McHowat J. Calcium-independent phospholipase A2 is regulated by a novel protein kinase C in human coronary artery endothelial cells. Am J Physiol Cell Physiol 2005; 288:C475-82. [PMID: 15643055 DOI: 10.1152/ajpcell.00306.2004] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We demonstrated previously that thrombin stimulation of endothelial cells activates a membrane-associated, Ca(2+)-independent phospholipase A2 (iPLA2) that selectively hydrolyzes arachidonylated plasmalogen phospholipids. We report that incubation of human coronary artery endothelial cells (HCAEC) with phorbol 12-myristate 13-acetate (PMA) to activate protein kinase C (PKC) resulted in hydrolysis of cellular phospholipids similar to that observed with thrombin stimulation (0.05 IU/ml; 10 min). Thrombin stimulation resulted in a decrease in arachidonylated plasmenylcholine (2.7 +/- 0.1 vs. 5.3 +/- 0.4 nmol PO4/mg of protein) and plasmenylethanolamine (7.5 +/- 1.0 vs. 12.0 +/- 0.9 nmol PO4/mg of protein). Incubation with PMA resulted in decreases in arachidonylated plasmenylcholine (3.2 +/- 0.3 nmol PO4/mg of protein) and plasmenylethanolamine (6.0 +/- 1.0 nmol PO4/mg of protein). Incubation of HCAEC with the selective iPLA2 inhibitor bromoenol lactone (5 mM; 10 min) inhibited accelerated plasmalogen phospholipid hydrolysis in response to both PMA and thrombin stimulation. Incubation of HCAEC with PMA (100 nM; 5 min) resulted in increased arachidonic acid release (7.1 +/- 0.3 vs. 1.1 +/- 0.1%) and increased production of lysoplasmenylcholine (1.4 +/- 0.2 vs. 0.6 +/- 0.1 nmol PO4/mg of protein), similar to the responses observed with thrombin stimulation. Downregulation of PKC by prolonged exposure to PMA (100 nM; 24 h) completely inhibited thrombin-stimulated increases in arachidonic acid release (7.1 +/- 0.6 to 0.5 +/- 0.1%) and lysoplasmenylcholine production (2.0 +/- 0.1 to 0.2 +/- 0.1 nmol PO4/mg of protein). These data suggest that PKC activates iPLA2 in HCAEC, leading to accelerated plasmalogen phospholipid hydrolysis and increased phospholipid metabolite production.
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Affiliation(s)
- Maureen C Meyer
- Department of Pathology, St. Louis University School of Medicine, St. Louis, Missouri 63104, USA
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Su X, Mancuso DJ, Bickel PE, Jenkins CM, Gross RW. Small interfering RNA knockdown of calcium-independent phospholipases A2 beta or gamma inhibits the hormone-induced differentiation of 3T3-L1 preadipocytes. J Biol Chem 2004; 279:21740-8. [PMID: 15024020 DOI: 10.1074/jbc.m314166200] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Alterations in lipid secondary messenger generation and lipid metabolic flux are essential in promoting the differentiation of adipocytes. To determine whether specific subtypes of intracellular phospholipases A(2) (PLA(2)s) facilitate hormone-induced differentiation of 3T3-L1 cells into adipocytes, we examined alterations in the mRNA level, protein mass, and activity of three previously characterized mammalian intracellular PLA(2)s. Hormone-induced differentiation of 3T3-L1 cells resulted in 7.3 +/- 0.5- and 7.4 +/- 1.4-fold increases of mRNA encoding the calcium-independent phospholipases, iPLA(2)beta and iPLA(2)gamma, respectively. In contrast, the temporally coordinated loss of at least 90% of cPLA(2)alpha mRNA was manifest. Western analysis demonstrated the near absence of both iPLA(2)beta and iPLA(2)gamma protein mass in resting 3T3-L1 cells that increased dramatically during differentiation. In vitro measurement of PLA(2) activities demonstrated an increase in both iPLA(2)beta and iPLA(2)gamma activities that were discriminated using the chiral mechanism based inhibitors (S)- and (R)-BEL, respectively. Remarkably, treatment of 3T3-L1 cells with small interfering RNA directed against either iPLA(2)beta or iPLA(2)gamma prevented hormone-induced differentiation. Moreover, analysis of the temporally programmed expression of transcription factors demonstrated that the small interfering RNA knockdown of iPLA(2)beta or iPLA(2)gamma resulted in down-regulation of the expression of peroxisome proliferator-activated receptor gamma and the CCAAT enhancer-binding protein alpha (C/EBPalpha). No alterations in the expression of the early stage transcription factors C/EBPbeta and C/EBPdelta were observed. Collectively, these results demonstrate prominent alterations in intracellular PLA(2)s during 3T3-L1 cell differentiation into adipocytes and identify the requirement of iPLA(2)beta and iPLA(2)gamma for the adipogenic program that drives resting 3T3-L1 cells into adipocytes after hormone stimulation.
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Affiliation(s)
- Xiong Su
- Department of Internal Medicine, Washington University School of Medicine, St Louis, Missouri 63110, USA
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Steer SA, Wirsig KC, Creer MH, Ford DA, McHowat J. Regulation of membrane-associated iPLA2 activity by a novel PKC isoform in ventricular myocytes. Am J Physiol Cell Physiol 2002; 283:C1621-6. [PMID: 12419708 DOI: 10.1152/ajpcell.00109.2002] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Thrombin stimulation of rabbit ventricular myocytes increases membrane-associated, Ca2+-independent phospholipase A2 (iPLA2) activity, resulting in accelerated hydrolysis of membrane plasmalogen phospholipids and increased production of arachidonic acid and lysoplasmenylcholine. This study was designed to investigate the signal transduction pathways involved in activation of membrane-associated iPLA2. Incubation of isolated membrane fractions suspended in Ca2+-free buffer with thrombin or phorbol 12-myristate 13-acetate resulted in a two- to threefold increase in iPLA2 activity. Prior treatment with the PKC inhibitor GF-109203X blocked iPLA2 activation by thrombin. These data suggest that a novel PKC isoform present in the membrane fraction modulates iPLA2 activity. Immunoblot analysis revealed a significant portion of PKC-epsilon present in the membrane fraction, but no other membrane-associated novel PKC isoform was detected by this method. These data indicate that activation of membrane-associated iPLA2 is mediated by a membrane-associated novel PKC isoform in thrombin-stimulated rabbit ventricular myocytes.
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Affiliation(s)
- Sarah A Steer
- Department of Biochemistry, St. Louis University School of Medicine, St. Louis, Missouri 63104, USA
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Olivero J, Ganey PE. Participation of Ca2+/calmodulin during activation of rat neutrophils by polychlorinated biphenyls. Biochem Pharmacol 2001; 62:1125-32. [PMID: 11597581 DOI: 10.1016/s0006-2952(01)00768-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The effects of Ca2+ and Ca2+/calmodulin on the polychlorinated biphenyl (PCB)-induced activation of phospholipase A2 (PLA2) in rat neutrophils were examined. The commercial PCB mixture Aroclor 1242 induced activation of PLA2 and promoted an increase in the intracellular free calcium concentration ([Ca2+]i). Bromoenol lactone (BEL), an inhibitor of the Ca2+-independent PLA2 isoform (iPLA2) activated by PCBs, did not abrogate the increase in [Ca2+]i, suggesting that this change in Ca2+ concentration is not downstream from the activation of iPLA2. TMB-8 [8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate], a blocker of the release of intracellular Ca2+, decreased Aroclor 1242-induced stimulation of PLA2 with a maximal inhibition of 17% at 50 microM. These two results suggest little direct dependence between the PCB-induced activation of iPLA2 and increase in [Ca2+]i. Calmidazolium and W7 [N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide], two chemically distinct calmodulin inhibitors, inhibited Aroclor 1242-induced PLA2 activity, whereas trifluoperazine (TFP), another inhibitor of calmodulin, had no effect at noncytotoxic concentrations. Thus, activation of PLA2 is dependent, in part, on calmodulin. Furthermore, both TFP and Aroclor 1242 inhibited neutrophil degranulation stimulated by the bacterial peptide formyl-methionyl-leucyl-phenylalanine. These results raise the possibility that some of the effects of PCBs on neutrophil function can be explained by effects on Ca2+/calmodulin-dependent processes.
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Affiliation(s)
- J Olivero
- Department of Pharmacology and Toxicology, National Food Safety and Toxicology Center and Institute for Environmental Toxicology, Michigan State University, East Lansing, MI 48824, USA
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Mizuno-Kamiya M, Inokuchi H, Kameyama Y, Yashiro K, Fujita A. Ca2+-independent phospholipase A2 activity in apical plasma membranes from the rat parotid gland. Arch Oral Biol 2001; 46:789-99. [PMID: 11420051 DOI: 10.1016/s0003-9969(01)00050-4] [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: 10/18/2022]
Abstract
An apical-enriched plasma membrane fraction (A-PM) was prepared from rat parotid gland by Mn2+ precipitation. In this fraction, phosphatidylcholine (PC) labelled at the sn-2 position was mainly decomposed into two labelled compounds (free fatty acid and 1,2-diacylglycerol) under Ca2+-free conditions. Studies using double-labelled PC and 2,3-diphosphoglycerate (as a phospholipase D inhibitor) showed that they were produced through different pathways: free fatty acid was released by phospholipase A2 (PLA2) while 1,2-diacylglycerol may be produced by sequential action of phospholipase D and phosphatidate phosphatase. The PLA2 in A-PM did not require Ca2+ for its activity and was highly activated by Triton X-100 and ATP. The inhibitor of the well-documented Ca2+-independent PLA2, bromoenol lactone, did not inhibit the PLA2 activity in A-PM. Although PLA2 activity was detected in other subcellular fractions, the highest specific activity was in A-PM. Its distribution among various fractions was roughly similar to that of the marker enzyme of apical plasma membranes. These findings suggested that Ca2+-independent PLA2 activity is present in apical plasma membranes from rat parotid gland. In addition, to clarify the involvement of the PLA2 in exocytosis, the fusion of exogenous PLA2-treated membranes with secretory granules was examined by fluorescence dequenching assay. This study clearly demonstrated the facilitation of fusion by PLA2 treatment, which suggests some involvement of apical PLA2 in saliva secretion.
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Affiliation(s)
- M Mizuno-Kamiya
- Department of Oral Biochemistry, Asahi University School of Dentistry, 1851 Hozumi, Motosu, 501-0296, Gifu, Japan.
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Han MH, Han DK, Aebersold RH, Glomset JA. Effects of protein kinase CK2, extracellular signal-regulated kinase 2, and protein phosphatase 2A on a phosphatidic acid-preferring phospholipase A1. J Biol Chem 2001; 276:27698-708. [PMID: 11328814 DOI: 10.1074/jbc.m101983200] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A soluble, phosphatidic acid-preferring phospholipase A1, expressed in mature bovine testes but not in newborn calf testes, may contribute to the formation or function of sperm. Here we incubated a recombinant preparation of the phospholipase in vitro with several enzymes including protein kinase CK2 (CK2), extracellular signal-regulated kinase 2 (ERK2), and protein phosphatase 2A (PP2A) to identify effects that might be of regulatory importance in vivo. Major findings were that 1) CK2 phosphorylated the phospholipase on serines 93, 105, and 716; 2) ERK2 phosphorylated the enzyme on serine 730; 3) there was cross-antagonism between the reactions that phosphorylated serines 716 and 730; 4) PP2A selectively hydrolyzed phosphate groups that were esterified to serines 716 and 730; 5) CK2alpha formed a stable, MgATP/MgGTP-dependent complex with the phospholipase by a novel mechanism; and 6) the complex showed reduced phospholipase activity and resembled a complex identified in homogenates of macaque testis. These results provide the first available information about the effects of reactions of phosphorylation and dephosphorylation on the behavior of the phospholipase, shed light on properties of CK2alpha that may be required for the formation of complexes with its substrates, and raise the possibility that a complex containing CK2alpha and the phospholipase may play a special biological role in the testis.
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Affiliation(s)
- M H Han
- Howard Hughes Medical Institute, Departments of Medicine and Biochemistry, and Regional Primate Research Center, University of Washington, Seattle, Washington 98195-7370, USA
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25
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Murphy EJ, Rosenberger TA, Patrick CB, Rapoport SI. Intravenously injected [1-14C]arachidonic acid targets phospholipids, and [1-14C]palmitic acid targets neutral lipids in hearts of awake rats. Lipids 2000; 35:891-8. [PMID: 10984112 DOI: 10.1007/s11745-000-0598-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The differential uptake and targeting of intravenously infused [1-14C]palmitic ([1-14C]16:0) and [1-14C]arachidonic ([1-14C]20:4n-6) acids into heart lipid pools were determined in awake adult male rats. The fatty acid tracers were infused (170 microCi/kg) through the femoral vein at a constant rate of 0.4 mL/min over 5 min. At 10 min postinfusion, the rats were killed using pentobarbital. The hearts were rapidly removed, washed free of exogenous blood, and frozen in dry ice. Arterial blood was withdrawn over the course of the experiment to determine plasma radiotracer levels. Lipids were extracted from heart tissue using a two-phase system, and total radioactivity was measured in the nonvolatile aqueous and organic fractions. Both fatty acid tracers had similar plasma curves, but were differentially distributed into heart lipid compartments. The extent of [1-14C]20:4n-6 esterification into heart phospholipids, primarily choline glycerophospholipids, was elevated 3.5-fold compared to [1-14C]16:0. The unilateral incorporation coefficient, k*, which represents tissue radioactivity divided by the integrated plasma radioactivity for heart phospholipid, was sevenfold greater for [1-14C]20:4n-6 than for [1-14C]16:0. In contrast, [1-14C]16:0 was esterified mainly into heart neutral lipids, primarily triacylglycerols (TG), and was also found in the nonvolatile aqueous compartment. Thus, in rat heart, [1-14C]20:4n-6 was primarily targeted for esterification into phospholipids, while [1-14C]16:0 was targeted for esterification into TG or metabolized into nonvolatile aqueous components.
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Affiliation(s)
- E J Murphy
- Section on Brain Physiology and Metabolism, National Institute on Aging, National Institutes of Health, Bethesda, Maryland 20892-1582, USA.
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26
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Olivero J, Ganey PE. Role of protein phosphorylation in activation of phospholipase A2 by the polychlorinated biphenyl mixture Aroclor 1242. Toxicol Appl Pharmacol 2000; 163:9-16. [PMID: 10662600 DOI: 10.1006/taap.1999.8827] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Polychlorinated biphenyls (PCBs) activate neutrophils to induce degranulation and undergo superoxide production through a mechanism that involves stimulation of phospholipase A(2) (PLA(2)). Since the biochemical processes leading to the PCB-induced activation of this enzyme are unknown, the objective of this study was to determine whether protein phosphorylation has a role in this mechanism. Isolated rat neutrophils were labeled with [(3)H]-arachidonic acid ([(3)H]-AA), and activation of PLA(2) was determined from release of radioactivity into the medium. Exposure to the PCB mixture Aroclor 1242 induced release of [(3)H]-AA, and pretreatment with bromoenol lactone (BEL), an inhibitor of calcium-independent PLA(2), diminished release by 80%. Genistein, an inhibitor of tyrosine kinases, caused a small but significant decrease in Aroclor 1242-stimulated release of [(3)H]-AA. Daidzein, a genistein analog with no activity to inhibit tyrosine kinases, had no effect on [(3)H]-AA release. An inhibitor of p38 mitogen-activated protein kinase (MAPK), SB203580, did not affect Aroclor 1242-induced PLA(2) activity at concentrations selective for p38 MAPK; however, PD 98059, which inhibits MAPK kinase (MEK), decreased [(3)H]-AA release to about the same extent as genistein. Treatment of neutrophils with Aroclor 1242 induced phosphorylation of p44 MAPK, and this phosphorylation was unaffected by BEL but was inhibited by PD 98059. Staurosporine, a nonselective inhibitor of protein kinase C (PKC), inhibited PCB-induced release of [(3)H]-AA. Ro 32-0432, a selective inhibitor of PKC(alpha) and PKC(beta1), produced the greatest degree of inhibition (40%) among the tested protein kinase inhibitors. These results suggest that tyrosine kinases, PKC, and the MEK/MAPK pathway are involved in a fraction of Aroclor 1242-induced activation of PLA(2).
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Affiliation(s)
- J Olivero
- Department of Pharmacology, Michigan State University, East Lansing, Michigan, 48824, USA
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27
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Alasnier C, Meynier A, Viau M, Gandemer G. Hydrolytic and Oxidative Changes in the Lipids of Chicken Breast and Thigh Muscles During Refrigerated Storage. J Food Sci 2000. [DOI: 10.1111/j.1365-2621.2000.tb15947.x] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Abstract
Phospholipase A2 (PLA2) is an enzyme that catalyzes the hydrolysis of membrane phospholipids. This article reviews the source and structure of PLA2, the involvement of the enzyme in various biological and pathological phenomena, and the usefulness of PLA2 assays in laboratory diagnostics. Of particular importance is the role of PLA2 in the cellular production of mediators of inflammatory response to various stimuli. Assays for PLA2 activity and mass concentration are discussed, and the results of enzyme determinations in plasma from patients with different pathological conditions are presented. The determination of activity and mass concentration in plasma is particularly useful in the diagnosis and prognosis of pancreatitis, multiple organ failure, septic shock, and rheumatoid arthritis. A very important result is the demonstration that PLA2 is an acute phase protein, like CRP. Indeed, there is a close correlation between PLA2 mass concentration and CRP levels in several pathological conditions. Although the determination of C-reactive protein is much easier to perform and is routinely carried out in most clinical laboratories, the assessment of PLA2 activity or mass concentration has to be considered as a reliable approach to obtain a deeper understanding of some pathological conditions and may offer additional information concerning the prognosis of several disorders.
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Affiliation(s)
- E Kaiser
- Department of Medical Chemistry, University of Vienna, Austria
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29
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Owada S, Larsson O, Arkhammar P, Katz AI, Chibalin AV, Berggren PO, Bertorello AM. Glucose decreases Na+,K+-ATPase activity in pancreatic beta-cells. An effect mediated via Ca2+-independent phospholipase A2 and protein kinase C-dependent phosphorylation of the alpha-subunit. J Biol Chem 1999; 274:2000-8. [PMID: 9890957 DOI: 10.1074/jbc.274.4.2000] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In the pancreatic beta-cell, glucose-induced membrane depolarization promotes opening of voltage-gated L-type Ca2+ channels, an increase in cytoplasmic free Ca2+ concentration ([Ca2+]i), and exocytosis of insulin. Inhibition of Na+,K+-ATPase activity by ouabain leads to beta-cell membrane depolarization and Ca2+ influx. Because glucose-induced beta-cell membrane depolarization cannot be attributed solely to closure of ATP-regulated K+ channels, we investigated whether glucose regulates other transport proteins, such as the Na+,K+-ATPase. Glucose inhibited Na+,K+-ATPase activity in single pancreatic islets and intact beta-cells. This effect was reversible and required glucose metabolism. The inhibitory action of glucose was blocked by pretreatment of the islets with a selective inhibitor of a Ca2+-independent phospholipase A2. Arachidonic acid, the hydrolytic product of this phospholipase A2, also inhibited Na+, K+-ATPase activity. This effect, like that of glucose, was blocked by nordihydroguaiaretic acid, a selective inhibitor of the lipooxygenase metabolic pathway, but not by inhibitors of the cyclooxygenase or cytochrome P450-monooxygenase pathways. The lipooxygenase product 12(S)-HETE (12-S-hydroxyeicosatetranoic acid) inhibited Na+,K+-ATPase activity, and this effect, as well as that of glucose, was blocked by bisindolylmaleimide, a specific protein kinase C inhibitor. Moreover, glucose increased the state of alpha-subunit phosphorylation by a protein kinase C-dependent process. These results demonstrate that glucose inhibits Na+, K+-ATPase activity in beta-cells by activating a distinct intracellular signaling network. Inhibition of Na+,K+-ATPase activity may thus be part of the mechanisms whereby glucose promotes membrane depolarization, an increase in [Ca2+]i, and thereby insulin secretion in the pancreatic beta-cell.
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Affiliation(s)
- S Owada
- Rolf Luft Center for Diabetes Research L6B:01, Department of Molecular Medicine, Karolinska Institutet, Karolinska Hospital, S-171 76 Stockholm, Sweden
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30
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Abstract
We characterized phospholipase A2 (PLA2) activity in isolated rabbit ventricular myocytes with respect to subcellular distribution, substrate specificity, and Ca2+ dependency. Membrane-associated PLA2 was found to be an order of magnitude greater than cytosolic PLA2. Ventricular myocyte PLA2 activity was enhanced following protease-activated receptor stimulation with thrombin and was found to be largely Ca2+-independent and selective for phospholipid substrates containing arachidonic acid at the sn-2 position. Immunoblot analysis using an antibody to cytosolic Ca2+-independent PLA2 from Chinese hamster ovary cells recognized a membrane-associated protein with a molecular mass of approximately 80 kDa; however, differences in pH optima, response to inhibitors, and substrate selectivity of membrane-associated and cytosolic PLA2 activity suggest the presence of multiple Ca2+-independent PLA2. Pretreatment with bromoenol lactone, a specific inhibitor of Ca2+-independent PLA2, significantly attenuated membrane-associated and cytosolic PLA2 in unstimulated and thrombin-stimulated myocytes. Pretreatment with methyl arachidonyl fluorophosphonate, mepacrine, or dibucaine had no significant effect on PLA2 activity under all conditions tested. Ventricular myocyte PLA2 activity was significantly inhibited by ATP, GTP, and their nonhydrolyzable analogs and was regulated by protein kinase C activity. These studies demonstrate the presence of one or more unique membrane-associated Ca2+-independent PLA2 in isolated ventricular myocytes that exhibit a preference for phospholipids with arachidonate at the sn-2 position and that are activated by thrombin stimulation.
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Affiliation(s)
- J McHowat
- Department of Pathology, St. Louis University School of Medicine, Missouri 63104, USA.
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McHowat J, Liu S, Creer MH. Selective hydrolysis of plasmalogen phospholipids by Ca2+-independent PLA2 in hypoxic ventricular myocytes. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 274:C1727-37. [PMID: 9611139 DOI: 10.1152/ajpcell.1998.274.6.c1727] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Accelerated phospholipid catabolism occurs early after the onset of myocardial ischemia and is likely to be mediated by the activation of one or more phospholipases in ischemic tissue. We hypothesized that hypoxia increases phospholipase A2 (PLA2) activity in isolated ventricular myocytes, resulting in increased lysophospholipid and arachidonic acid production, contributing to arrhythmogenesis in ischemic heart disease. The majority of ventricular myocyte arachidonic acid was found in plasmalogen phospholipids. Hypoxia increased membrane-associated, Ca2+-independent, plasmalogen-selective PLA2 activity, resulting in increased arachidonic acid release and lysoplasmenylcholine production. Pretreatment with the specific Ca2+-independent PLA2 inhibitor bromoenol lactone blocked hypoxia-induced increases in PLA2 activity, arachidonic acid release, and lysoplasmenylcholine production. Lysoplasmenylcholine produced action potential derangements, including shortening of action potential duration, and induced early and delayed afterdepolarizations in normoxic myocytes. The electrophysiological alterations induced by lysoplasmenylcholine would likely contribute to the initiation of arrhythmogenesis in the ischemic heart.
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Affiliation(s)
- J McHowat
- Department of Pathology, St. Louis University Medical School, St. Louis, Missouri 63104, USA
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McHowat J, Creer MH. Thrombin activates a membrane-associated calcium-independent PLA2 in ventricular myocytes. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 274:C447-54. [PMID: 9486135 DOI: 10.1152/ajpcell.1998.274.2.c447] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Activation of phospholipase A2 (PLA2) and accumulation of lysophosphatidylcholine contribute importantly to arrhythmogenesis during acute myocardial ischemia. We examined thrombin stimulation of PLA2 activity in isolated ventricular myocytes. Basal and thrombin-stimulated cardiac myocyte PLA2 activity demonstrated a distinct preference for sn-1 ether-linked phospholipids with arachidonate esterified at the sn-2 position. The majority of PLA2 activity was calcium independent and membrane associated. Thrombin stimulation of membrane-associated PLA2 occurs in a time- and concentration-dependent fashion. An increase in PLA2 activity was also observed using the synthetic peptide SFLLRNPNDKYEPF (the tethered ligand generated by thrombin cleavage of its receptor). Bromoenol lactone, a selective inhibitor of calcium-independent PLA2, completely blocked thrombin-stimulated increases in PLA2 activity and arachidonic acid release. No significant inhibition of thrombin-induced PLA2 was observed following pretreatment with mepacrine or dibucaine. These data confirm the presence of high-affinity thrombin receptors on isolated cardiac myocytes and demonstrate the specific activation of a unique membrane-associated, calcium-independent PLA2 following thrombin receptor ligation.
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Affiliation(s)
- J McHowat
- Department of Pathology, St. Louis University Medical School, Missouri 63104, USA
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33
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Ma Z, Landt M, Bohrer A, Ramanadham S, Kipnis DM, Turk J. Interleukin-1 reduces the glycolytic utilization of glucose by pancreatic islets and reduces glucokinase mRNA content and protein synthesis by a nitric oxide-dependent mechanism. J Biol Chem 1997; 272:17827-35. [PMID: 9211938 DOI: 10.1074/jbc.272.28.17827] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Culture of rat pancreatic islets with interleukin-1 (IL-1) results in up-regulation of the inducible isoform of nitric oxide synthase and overproduction of nitric oxide (NO). This is associated with reversible inhibition of both glucose-induced insulin secretion and islet glucose oxidation, and these effects are prevented by the inducible nitric oxide synthase inhibitor NG-monomethylarginine. IL-1 also induces accumulation of nonesterified arachidonic acid in islets by an NO-dependent mechanism, and one potential explanation for that effect would involve an IL-1-induced enhancement of islet glycolytic flux. We have therefore examined effects of IL-1 on islet glycolytic utilization of glucose and find that culture of islets with IL-1 in medium containing 5.5 mM glucose results in suppression of islet glucose utilization subsequently measured at glucose concentrations between 6 and 18 mM. The IL-1-induced suppression of islet glucose utilization is associated with a decline in islet glucokinase mRNA content, as determined by competitive reverse transcriptase-polymerase chain reaction, and in glucokinase protein synthesis, as determined by immuoprecipitation experiments, and all of these effects are prevented by NG-monomethylarginine. These findings suggest that IL-1 can down-regulate islet glucokinase, which is the primary component of the islet glucose-sensor apparatus, by an NO-dependent mechanism. Because reductions in islet glucokinase levels are known to cause a form of type II diabetes mellitus, these observations raise the possibility that factors which increase islet NO levels might contribute to development of glucose intolerance.
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Affiliation(s)
- Z Ma
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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34
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Van der Vusse GJ, Reneman RS, van Bilsen M. Accumulation of arachidonic acid in ischemic/reperfused cardiac tissue: possible causes and consequences. Prostaglandins Leukot Essent Fatty Acids 1997; 57:85-93. [PMID: 9250613 DOI: 10.1016/s0952-3278(97)90497-x] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Under physiological conditions, the content of unesterified arachidonic acid in cardiac tissue is very low. The bulk of arachidonic acid is present in the membrane phospholipid pool. Incorporation of arachidonic acid into phospholipids (reacylation) and liberation of this fatty acid from the phospholipid pool (deacylation) are controlled by a set of finely tuned enzymes, including lysophospholipid acyltransferase and phospholipase A2. At present, at least three subtypes of phospholipase A2 have been identified in cardiac structures, i.e., a low molecular mass group II phospholipase A2, a cytoplasmic high molecular mass phospholipase A2 and a plasmalogen-specific phospholipase A2. Cessation of flow to the heart (ischemia) gives rise to net degradation of membrane phospholipids accompanied by accumulation of fatty acids, including (unesterified) arachidonic acid. Restoration of flow to the previously ischemic cells results in a continued accumulation of fatty acids. The mechanism(s) underlying net phospholipid degradation in ischemic/reperfused myocardial tissue is (are) incompletely understood. Impaired reacylation, enhanced hydrolysis of phospholipids, or a combination of both may be responsible for the phenomena observed. Elevated tissue levels of arachidonic acid may exert both direct and indirect effects on the affected myocardium and healthy cardiac cells adjacent to the injured cardiomyocytes. Indirect effects might be evoked by arachidonic acid metabolites, i.e., eicosanoids. Arachidonic acid may directly influence ion channel activity, substrate metabolism and signal transduction, thereby affecting the functional characteristics of the ischemic/reperfused myocardium.
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Affiliation(s)
- G J Van der Vusse
- Department of Physiology, Maastricht University, Cardiovascular Research Institute Maastricht, the Netherlands.
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35
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Tang J, Kriz RW, Wolfman N, Shaffer M, Seehra J, Jones SS. A novel cytosolic calcium-independent phospholipase A2 contains eight ankyrin motifs. J Biol Chem 1997; 272:8567-75. [PMID: 9079687 DOI: 10.1074/jbc.272.13.8567] [Citation(s) in RCA: 238] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
We report the purification, molecular cloning, and expression of a novel cytosolic calcium-independent phospholipase A2 (iPLA2) from Chinese hamster ovary cells, which lacks extended homology to other phospholipases. iPLA2 is an 85-kDa protein that exists as a multimeric complex of 270-350 kDa with a specific activity of 1 micromol/min/mg. The full-length cDNA clone encodes a 752-amino acid cytoplasmic protein with one lipase motif (GXS465XG) and eight ankyrin repeats. Expression of the cDNA in mammalian cells generates an active 85-kDa protein. Mutagenesis studies show that Ser465 and the ankyrin repeats are required for activity. We demonstrate that iPLA2 selectively hydrolyzes the sn-2 over sn-1 fatty acid by 5-fold for 1,2-dipalmitoyl phosphatidylcholine in a mixed micelle. Moreover, we found the fatty acid preference at the sn-2 position to be highly dependent upon substrate presentation. However, iPLA2 does have a marked preference for 1,2-dipalmitoyl phosphatidic acid presented in a vesicle, generating the lipid second messenger lysophosphatidic acid. Finally the enzyme is able to hydrolyze the acetyl moiety at the sn-2 position of platelet-activating factor.
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Affiliation(s)
- J Tang
- Genetics Institute, Cambridge, Massachusetts 02140, USA
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36
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Keogh RJ, Dunlop ME, Larkins RG. Effect of inhibition of aldose reductase on glucose flux, diacylglycerol formation, protein kinase C, and phospholipase A2 activation. Metabolism 1997; 46:41-7. [PMID: 9005967 DOI: 10.1016/s0026-0495(97)90165-7] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Activation of the polyol pathway under hyperglycemic conditions is proposed to contribute to the development of diabetic nephropathy. The mechanisms by which this activation may lead to functional and structural changes within the kidney are yet to be definitively established. We have examined in vitro the steps linking increased polyol pathway activity resulting from hyperglycemia to prostaglandin production. Following the demonstration of increased prostaglandin E (PGE) levels in glomeruli from diabetic rats (14.9 +/- 2.5 v 59.1 +/- 19.4 ng PGE/mg protein), a specific inhibitor of aldose reductase, HOE-843, was used in vitro to analyze the response to hyperglycemia of the steps preceding prostaglandin production. In explants of glomeruli from control animals, increasing the glucose concentration in vitro from 5.6 mmol/L to 25 mmol/L resulted in a significant increase in the flux of glucose through the pentose phosphate pathway ([PPP] 1.29 +/- 0.08 v 2.00 +/- 0.11 nmol/h), de novo diacylglycerol synthesis (2.2 +/- 0.1 v 3.1 +/- 0.2 micromol/mg protein), membrane protein kinase C (PKC) activity (18.7 +/- 0.5 v 24.3 +/- 0.75 pmol/microg protein), and in vitro phospholipase A2 (PLA2) activity (2.18 +/- 0.46 v 3.83 +/- 1.07 nmol arachidonic acid hydrolyzed/min/mg cytosolic protein). For all parameters measured, the increase resulting from the increased glucose concentration could be prevented by in vitro addition of HOE-843 for 24 hours before measurement. These findings provide evidence to suggest a mechanism linking increased polyol pathway activity and an increase in PLA2 activity to increased prostaglandin production, which is observed in diabetes of recent onset and may ultimately lead to changes associated with the development of diabetic nephropathy.
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Affiliation(s)
- R J Keogh
- Department of Medicine, University of Melbourne, Parkville, Victoria, Australia
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37
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Pompeo A, Luini A, Buccione R. Functional dissociation between glucocorticoid-induced decrease in arachidonic acid release and inhibition of adrenocorticotropic hormone secretion in AtT-20 corticotrophs. J Steroid Biochem Mol Biol 1997; 60:51-7. [PMID: 9182858 DOI: 10.1016/s0960-0760(96)00161-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The biochemical basis of the short-term inhibitory effects of glucocorticoids on corticotropin release from pituitary corticotrophs is still obscure. A well-characterized effect of glucocorticoids in several cell types is the inhibition of arachidonic acid (AA) generation by phospholipase A2 (PLA2). Arachidonic acid and its metabolites have been implicated in the secretory process from a number of pituitary cells, such as the corticotrophs. We have thus examined the role of AA in the anti-secretagogue effects of glucocorticoids in a corticotropin-secreting clonal corticotroph line (AtT-20 D16/16). Glucocorticoids decreased AA release induced by melittin, a bee venom protein related to extracellular PLA2. When a possible role of AA in corticotropin release was studied, the following results were obtained: (a) all corticotropin secretagogues tested, including corticotropin-releasing factor (CRF), did not alter AA generation; (b) calcium and guanine nucleotides, which stimulate corticotropin release in permeabilized cells, inhibited the release of AA under the same conditions; (c) administration of melittin or of exogenous AA had no effect on basal and CRF-stimulated corticotropin release; (d) administration of large amounts of exogenous AA was unable to restore the ability to secrete corticotropin under suppression by glucocorticoids. Altogether, the data suggest that whereas glucocorticoids can inhibit both AA generation and corticotropin release, these two effects appear to be causally unrelated.
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Affiliation(s)
- A Pompeo
- Istituto di Richerche Farmacologiche Mario Negri, Consorzio Mario Negri Sud, Department of Cell Biology and Oncology, Chieti, Italy
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38
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39
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Wolf MJ, Gross RW. Expression, purification, and kinetic characterization of a recombinant 80-kDa intracellular calcium-independent phospholipase A2. J Biol Chem 1996; 271:30879-85. [PMID: 8940072 DOI: 10.1074/jbc.271.48.30879] [Citation(s) in RCA: 77] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
A CHO cell-derived 80-kDa recombinant polypeptide (GenBank number I15470I15470) putatively encoding a calcium-independent phospholipase A2 was expressed in S. frugiperda cells resulting in over a 15-fold increase in a calcium-independent phospholipase A1/A2 activity which was entirely inhibitable by (E)-6-(bromomethylene)-3-(1-naphthalenyl)-2H-tetrahydropyran-2-one. The recombinant polypeptide was purified from cytosol by sequential tandem affinity chromatographies employing ATP-agarose and calmodulin-Sepharose stationary phases. This strategy resulted in the rapid purification (36 h) of recombinant phospholipase A2 activity in 56% overall yield to a single intense 80-kDa protein band on SDS-polyacrylamide gel electrophoresis after silver staining. The purified protein possessed phospholipase A1, phospholipase A2, and lysophospholipase activities. Microbore anion exchange chromatography demonstrated that the 80-kDa protein band was comprised of multiple distinct isoforms including an anionic isoform which possessed over a 5-fold higher specific activity (5 micromol/mg.min) than earlier eluting isoforms. Collectively, these results unambiguously demonstrate that: 1) the 80-kDa polypeptide catalyzes phospholipase A1/A2 and lysophospholipase activities with distinct kinetic parameters; 2) calmodulin and ATP both interact with the catalytic polypeptide independent of regulatory proteins; and 3) distinct isoforms of this polypeptide exist which possess markedly different specific activities.
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Affiliation(s)
- M J Wolf
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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Ma Z, Ramanadham S, Kempe K, Hu Z, Ladenson J, Turk J. Characterization of expression of phosphofructokinase isoforms in isolated rat pancreatic islets and purified beta cells and cloning and expression of the rat phosphofructokinase-A isoform. BIOCHIMICA ET BIOPHYSICA ACTA 1996; 1308:151-63. [PMID: 8764833 DOI: 10.1016/0167-4781(96)00088-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Phosphofructokinase (PFK) plays a key role in regulating glycolytic flux, and the mammalian enzyme is a tetramer. Three monomeric isoforms are encoded by separate genes, are differentially expressed in specific tissues, and are designated by tissues in which they are most abundant (A, muscle; B, liver; and C, brain). Glucose-induced insulin secretion from pancreatic islets requires glucose transport into islet beta-cells and glycolytic metabolism. Little is known about islet PFK isozymes, but the possibility that PFK-A is expressed in beta-cells is of interest because that isoform is thought to govern glycolytic oscillations and to interact with a metabolically activated beta-cell phospholipase A2 enzyme. Using as probe a PCR product generated from rat islet RNA with primers designed from the human PFK-A sequence, we have cloned a full-length PFK-A cDNA from a rat islet cDNA library. The rat PFK-A deduced amino-acid sequence is 96% identical to that of human PFK-A, and all residues thought to participate in substrate or allosteric effector binding are conserved between the two sequences. The rat PFK-A amino-acid sequence is 69% and 68% identical to those for rat PFK-B and rat PFK-C, respectively, and differences in residues involved in binding of allosteric effectors were observed among the three isoforms. Rat PFK-A expressed as a glutathione-S-transferase fusion protein was recognized by antibodies raised against a peptide in the PFK-A sequence. Expression of PFK isoform mRNA species was examined by RT-PCR in rat islets, in purified populations of beta-cells prepared by fluorescence-activated cell sorting (FACS), and in RIN-m5F insulinoma cells, all of which expressed mRNA species for PFK-A, -B, and -C isoforms. PFK-A mRNA was expressed at much lower levels in an islet alpha-cell-enriched population. Interleukin-1 impairs islet glucose metabolism and insulin secretion and was found to induce a specific decline in islet expression of PFK-A mRNA. These findings establish the sequence of rat PFK-A, demonstrate that it is expressed in FACS-purified islet beta-cells, and suggest that its expression is regulated by a cytokine which influences insulin secretion.
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Affiliation(s)
- Z Ma
- Division of Endocrinology, Diabetes and Metabolism, Washington University School of Medicine, St. Louis, MO 63110, USA
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41
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Lio YC, Reynolds LJ, Balsinde J, Dennis EA. Irreversible inhibition of Ca(2+)-independent phospholipase A2 by methyl arachidonyl fluorophosphonate. BIOCHIMICA ET BIOPHYSICA ACTA 1996; 1302:55-60. [PMID: 8695655 DOI: 10.1016/0005-2760(96)00002-1] [Citation(s) in RCA: 176] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Methyl arachidonyl fluorophosphonate (MAFP) has been recently reported to be a selective, active-site directed, irreversible inhibitor of the Group IV 85 kDa cytosolic phospholipase A2 (cPLA2). We have now shown that this compound also potently inhibits the Ca(2+)-independent cytosolic phospholipase A2 (iPLA2). MAFP inhibited iPLA2 in a concentration-dependent manner with half-maximal inhibition observed at 0.5 microM after a 5 min preincubation at 40 degrees C. This inhibition was not reversed upon extensive dilution of the enzyme into the assay mixture. Preincubation of iPLA2 with MAFP resulted in a linear, time-dependent inactivation of enzyme activity, and the enzyme was protected from inactivation by the reversible inhibitor PACOCF3. The ability of MAFP to inhibit the iPLA2 suggests that this enzyme proceeds through an acyl-enzyme intermediate as has been proposed for the cPLA2. Further testing indicated that MAFP did not inhibit the arachidonoyl-CoA synthetase, CoA-dependent acyltransferase, or CoA-independent transacylase activities from P388D1 cells. Thus, MAFP is not a general inhibitor for enzymes which act on arachidonoyl substrates. Instead, the inhibitor appears to show some selectivity for PLA2, although it does not discriminate between cPLA2 and iPLA2. Particular caution must be exercised to distinguish these activities if this inhibitor is used in intact cells.
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Affiliation(s)
- Y C Lio
- Department of Chemistry and Biochemistry, Revelle College, San Diego, La Jolla, CA, USA
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42
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Portilla D, Dai G. Purification of a novel calcium-independent phospholipase A2 from rabbit kidney. J Biol Chem 1996; 271:15451-7. [PMID: 8663076 DOI: 10.1074/jbc.271.26.15451] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
We have recently identified a cytosolic calcium-independent phospholipase A2 (PLA2) that represents the major measurable PLA2 activity in rabbit proximal tubules (Portilla, D., Shah, S. V., Lehman, P. A., and Creer, M. H.(1994) J. Clin. Invest. 93, 1609-1615). We now report the 3200-fold purification of this PLA2 to homogeneity from rabbit kidney cortex through sequential column chromatography including anion exchange, hydrophobic interaction, Mono Q, hydroxylapatite, phenyl-Sepharose, and chromatofocusing fast protein liquid chromatography from rabbit kidney cortex. The purified enzyme had a molecular mass of 28 kDa, possessed a specific activity of 1.2 micronol/mg min and a neutral pH optimum, and exhibited a preferential hydrolysis toward sn-2 fatty acid from diradylglycerophospholipids. The purified polypeptide hydrolyzed plasmenylcholine > phosphatidylcholine glycerophospholipids and selectively cleaved phospholipids containing arachidonic acid at the sn-2 position in comparison to oleic acid. Antibodies against the purified protein precipitated all of the soluble calcium-independent PLA2 activity from rabbit kidney cortex. These data altogether suggest that the 28-kDa protein in the kidney represents a novel class of calcium-independent PLA2.
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Affiliation(s)
- D Portilla
- Department of Medicine, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205-7199, USA
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43
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Lennartz MR, Lefkowith JB. Role of arachidonate in monocyte/macrophage function. ACTA ACUST UNITED AC 1996. [DOI: 10.1016/s1874-5245(96)80017-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/21/2023]
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45
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Ackermann EJ, Dennis EA. Mammalian calcium-independent phospholipase A2. BIOCHIMICA ET BIOPHYSICA ACTA 1995; 1259:125-36. [PMID: 7488632 DOI: 10.1016/0005-2760(95)00143-z] [Citation(s) in RCA: 100] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- E J Ackermann
- Department of Chemistry and Biochemistry, University of California at San Diego, La Jolla 92093-0601, USA
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46
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Affiliation(s)
- R W Gross
- Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
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47
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Farooqui AA, Yang HC, Horrocks LA. Plasmalogens, phospholipases A2 and signal transduction. BRAIN RESEARCH. BRAIN RESEARCH REVIEWS 1995; 21:152-61. [PMID: 8866672 DOI: 10.1016/0165-0173(95)00008-9] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Several lines of evidence indicate that the breakdown of plasmalogens in neural membranes during neurodegenerative diseases is a receptor-mediated process catalyzed by a plasmalogen-selective phospholipase A2. This enzyme has recently been purified from bovine brain. It does not require Ca2+ and is localized in cytosol. It has a molecular mass of 39 kDa and is strongly inhibited by glycosaminoglycans, with the pattern of inhibition being heparan sulfate > hyaluronic acid > chondroitin sulfate > heparin. This plasmalogen-selective phospholipase A2 is also inhibited by gangliosides and sialoglycoproteins. Substrate specificity and the effects of metal ions, detergents and inhibitors suggest that this phospholipase A2 is different from the well-known 85 kDa Ca(2+)-dependent cytosolic phospholipase A2 that has recently been cloned and is not plasmalogen-selective. The plasmalogen-selective phospholipase A2 may be regulated by glycosaminoglycans and sialoglycoconjugates and may be involved in the regulation of K+ channels. This enzyme, which plays a major role in the release of fatty acids during ischemic injury and reperfusion, shows promise as a major target for drug therapy.
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Affiliation(s)
- A A Farooqui
- Neurovation Inc. and Department of Medical Biochemistry, Ohio State University, Columbus 43210, USA
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48
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Gross RW, Rudolph AE, Wang J, Sommers CD, Wolf MJ. Nitric oxide activates the glucose-dependent mobilization of arachidonic acid in a macrophage-like cell line (RAW 264.7) that is largely mediated by calcium-independent phospholipase A2. J Biol Chem 1995; 270:14855-8. [PMID: 7797462 DOI: 10.1074/jbc.270.25.14855] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Herein, we demonstrate that nitric oxide is a potent (> 20% release) and highly selective inducer of [3H]arachidonic acid mobilization in the macrophage-like cell line RAW 264.7. Treatment of RAW 264.7 cells with (E)-6-(bromomethylene)-3-(1-naphthalenyl)-2H-tetrahydropyran-2-one resulted in the inhibition of the large majority (86%) of nitric oxide-induced [3H]arachidonic acid release into the medium (IC50 < 0.5 microM) and the concomitant inhibition of in vitro measurable calcium-independent phospholipase A2 activity (92% inhibition) without demonstrable effects on calcium-dependent phospholipase A2 activity. Since nitric oxide is a potent stimulator of glycolysis (and therefore glycolytically derived ATP) and since cytosolic calcium-independent phospholipase A2 exists as a catalytic complex comprised of ATP-modulated phosphofructokinase-like regulatory polypeptides and a catalytic subunit, we examined the role of glucose in facilitating nitric oxide-mediated arachidonic acid release. Nitric oxide-induced release of [3H]arachidonic acid possessed an obligatory requirement for glucose, was highly correlated with the concentration of glucose in the medium, and was dependent on the metabolism of glucose. Thus, [3H]arachidonic acid release is coupled to cellular glucose metabolism through alterations in the activity of calcium-independent phospholipase A2. Collectively, these results identify a unifying metabolic paradigm in which the generation of lipid second messengers is coordinately linked to the signalstimulated acceleration of glycolytic flux, thereby facilitating integrated metabolic responses to cellular stimuli.
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Affiliation(s)
- R W Gross
- Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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Neve EP, Boyer CS, Moldéus P. N-ethyl maleimide stimulates arachidonic acid release through activation of the signal-responsive phospholipase A2 in endothelial cells. Biochem Pharmacol 1995; 49:57-63. [PMID: 7840783 DOI: 10.1016/0006-2952(94)00308-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Treatment of bovine endothelial cells with the alkylator N-ethyl maleimide results in arachidonic acid mobilization. N-ethyl maleimide-stimulated arachidonic acid release was dose and time dependent and maximum release was achieved after 10-15 min with 50 microM N-ethyl maleimide, N-ethyl maleimide-stimulated arachidonic acid release could be prevented by pretreating the cells with the phospholipase A2 inhibitor quinacrine. Based on the finding that N-ethyl maleimide was not able to release oleic acid from oleic acid-preloaded cells, it was clear that the effect of N-ethyl maleimide was limited to an arachidonic acid-specific phospholipase. The effect of N-ethyl maleimide does not appear to be dependent on calcium, as shown by the observation that N-ethyl maleimide was not able to increase intracellular calcium concentration in FURA2-loaded cells. Pretreatment of the cells with staurosporine totally inhibited N-ethyl maleimide-stimulated arachidonic acid liberation. The tyrosine kinase inhibitor genistein was also able to significantly inhibit arachidonic acid release. It is concluded from the results obtained in this study that N-ethyl maleimide stimulates arachidonic acid release by stimulating the activity of a specific, signal-responsive phospholipase A2. Furthermore this activation is not mediated by intracellular calcium fluxes but by a stimulation of intracellular kinase activity which eventually leads to the activation of this signal-responsive phospholipase A2.
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Affiliation(s)
- E P Neve
- Division of Toxicology, Karolinska Institute, Stockholm, Sweden
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Ackermann EJ, Conde-Frieboes K, Dennis EA. Inhibition of macrophage Ca(2+)-independent phospholipase A2 by bromoenol lactone and trifluoromethyl ketones. J Biol Chem 1995; 270:445-50. [PMID: 7814408 DOI: 10.1074/jbc.270.1.445] [Citation(s) in RCA: 322] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
A novel Ca(2+)-independent phospholipase A2 (PLA2) has recently been purified from the murine macrophage-like cell line P388D1 (Ackermann, E. J., Kempner, E. S., and Dennis, E. A. (1994) J. Biol. Chem. 269, 9227-9233). This enzyme is now shown to be inhibited by palmitoyl trifluoromethyl ketone (PACOCF3), arachidonyl trifluoromethyl ketone (AACOCF3), and a bromoenol lactone (BEL). Both PACOCF3 and AACOCF3 were found to inhibit the macrophage PLA2 in a concentration-dependent manner. PACOCF3 was found to be approximately 4-fold more potent than AACOCF3, with IC50 values of 3.8 microM (0.0075 mol fraction) and 15 microM (0.028 mol fraction), respectively. Reaction progress curves in the presence of either inhibitor were found to be linear, and the PACOCF3.PLA2 complex rapidly dissociated upon dilution. BEL was also found to inhibit the macrophage PLA2 in a concentration-dependent manner, with half-maximal inhibition observed at 60 nM after a 5-min preincubation at 40 degrees C. Inhibition was not reversed after extensive dilution of the enzyme into assay buffer. Treatment of the PLA2 with BEL resulted in a linear, time-dependent inactivation of activity, and the rate of this inactivation was diminished in the presence of PACOCF3. In addition, PLA2 treated with [3H]BEL resulted in the covalent labeling of a major band at M(r) 80,000. Inactivation of the PLA2 by 5,5'-dithiobis(2-nitrobenzoic acid) prior to treatment with [3H]BEL resulted in the near complete lack of labeling consistent with covalent irreversible suicide inhibition of the enzyme. The labeling of a M(r) 80,000 band rather than a M(r) 40,000 band upon treatment with [3H]BEL distinguishes the macrophage Ca(2+)-independent PLA2 from a previously identified myocardial Ca(2+)-independent PLA2 and provides strong evidence that the M(r) 80,000 protein is the catalytic subunit.
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Affiliation(s)
- E J Ackermann
- Department of Chemistry and Biochemistry, Revelle College and School of Medicine, University of California at San Diego, La Jolla 92093-0601
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