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Hayashi D, Dennis EA. Differentiating human phospholipase A 2's activity toward phosphatidylinositol, phosphatidylinositol phosphate and phosphatidylinositol bisphosphate. Biochim Biophys Acta Mol Cell Biol Lipids 2024; 1869:159527. [PMID: 38917952 DOI: 10.1016/j.bbalip.2024.159527] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2024] [Revised: 05/02/2024] [Accepted: 05/24/2024] [Indexed: 06/27/2024]
Abstract
Phospholipase A2's (PLA2's) constitute a superfamily of enzymes that hydrolyze the sn-2 fatty acyl chain on glycerophospholipids. We have previously reported that each PLA2 Type shows a unique substrate specificity for the molecular species it hydrolyzes, especially the acyl chain that is cleaved from the sn-2 position and to some extent the polar group. However, phosphatidylinositol (PI) and PI phosphates (PIPs) have not been as well studied as substrates as other phospholipids because the PIPs require adaptation of the standard analysis methods, but they are important in vivo. We determined the in vitro activity of the three major types of human PLA2's, namely the cytosolic (c), calcium-independent (i), and secreted (s) PLA2's toward PI, PI-4-phosphate (PI(4)P), and PI-4,5-bisphosphate (PI(4,5)P2). The in vitro assay revealed that Group IVA cPLA2 (GIVA cPLA2) showed relatively high activity toward PI and PI(4)P among the tested PLA2's; nevertheless, the highly hydrophilic headgroup disrupted the interaction between the lipid surface and the enzyme. GIVA cPLA2 and GVIA iPLA2 showed detectable activity toward PI(4,5)P2, but it appeared to be a poorer substrate for all of the PLA2's tested. Furthermore, molecular dynamics (MD) simulations demonstrated that Thr416 and Glu418 of GIVA cPLA2 contribute significantly to accommodating the hydrophilic head groups of PI and PI(4)P, which could explain some selectivity for PI and PI(4)P. These results indicated that GIVA cPLA2 can accommodate PI and PI(4)P in its active site and hydrolyze them, suggesting that the GIVA cPLA2 may best account for the PI and PIP hydrolysis in living cells.
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Affiliation(s)
- Daiki Hayashi
- Department of Applied Chemistry in Bioscience, Graduate School of Agricultural Science, Faculty of Agriculture, Kobe University, Kobe 657-8501, Japan; Department of Pharmacology and Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093, USA
| | - Edward A Dennis
- Department of Pharmacology and Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093, USA.
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2
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Lin CY, Xu WB, Li BZ, Shu MA, Zhang YM. Identification and functional analysis of cytosolic phospholipase A2 (cPLA2) from the red swamp crayfish Procambarus clarkii: The first evidence of cPLA2 involved in immunity in invertebrates. FISH & SHELLFISH IMMUNOLOGY 2023; 140:108944. [PMID: 37451527 DOI: 10.1016/j.fsi.2023.108944] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Revised: 07/09/2023] [Accepted: 07/11/2023] [Indexed: 07/18/2023]
Abstract
Cytosolic phospholipase A2 (cPLA2) specifically liberates the arachidonic acids from the phospholipid substrates. In mammals, cPLA2 serves as a key control point in inflammatory responses due to its diverse downstream products. However, the role of cPLA2 in animals lower than mammals largely remains unknown. In the current research, a homolog of cPLA2 was first identified and characterized in the red swamp crayfish Procambarus clarkii. The full-length cDNA of PccPLA2 was 4432 bp in length with a 3036 bp-long open reading frame, encoding a putative protein of 1011 amino acids that contained a protein kinase C conserved region 2 and a catalytic subunit of cPLA2. PccPLA2 was ubiquitously expressed in all examined tissues with the highest expression in the hepatopancreas, and the expression in hemocytes as well as hepatopancreas was induced upon the immune challenges of WSSV and Aeromonas hydrophila. After the co-treatment of RNA interference and bacterial infection, the decline of bacteria clearance capability was observed in the hemolymph, and the expression of some antimicrobial peptides (AMPs) was significantly suppressed. Additionally, the phagocytosis of A. hydrophila by primary hemocytes decreased when treated with the specific inhibitor CAY10650 of cPLA2. These results indicated the participation of PccPLA2 in both cellular and humoral immune responses in the crayfish, which provided an insight into the role that cPLA2 played in the innate immunity of crustaceans, and even in invertebrates.
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Affiliation(s)
- Chen-Yang Lin
- College of Animal Sciences, Zhejiang University, Hangzhou, 310058, China
| | - Wen-Bin Xu
- College of Animal Sciences, Zhejiang University, Hangzhou, 310058, China
| | - Bang-Ze Li
- College of Animal Sciences, Zhejiang University, Hangzhou, 310058, China
| | - Miao-An Shu
- College of Animal Sciences, Zhejiang University, Hangzhou, 310058, China.
| | - Yan-Mei Zhang
- College of Animal Sciences, Zhejiang University, Hangzhou, 310058, China.
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Hayashi D, Mouchlis VD, Dennis EA. Omega-3 versus Omega-6 fatty acid availability is controlled by hydrophobic site geometries of phospholipase A 2s. J Lipid Res 2021; 62:100113. [PMID: 34474084 PMCID: PMC8551542 DOI: 10.1016/j.jlr.2021.100113] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2021] [Revised: 08/24/2021] [Accepted: 08/27/2021] [Indexed: 11/12/2022] Open
Abstract
Human phospholipase A2s (PLA2) constitute a superfamily of enzymes that hydrolyze the sn-2 acyl-chain of glycerophospholipids, producing lysophospholipids and free fatty acids. Each PLA2 enzyme type contributes to specific biological functions based on its expression, subcellular localization, and substrate specificity. Among the PLA2 superfamily, the cytosolic cPLA2 enzymes, calcium-independent iPLA2 enzymes, and secreted sPLA2 enzymes are implicated in many diseases, but a central issue is the preference for double-bond positions in polyunsaturated fatty acids (PUFAs) occupying the sn-2 position of membrane phospholipids. We demonstrate that each PLA2 has a unique preference between the specific omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) and the omega-6 arachidonic acid (AA), which are the precursors of most proinflammatory and anti-inflammatory or resolving eicosanoids and related oxylipins. Surprisingly, we discovered that human cPLA2 selectively prefers AA, whereas iPLA2 prefers EPA, and sPLA2 prefers DHA as substrate. We determined the optimal binding of each phospholipid substrate in the active site of each PLA2 to explain these specificities. To investigate this, we utilized recently developed lipidomics-based LC-MS/MS and GC/MS assays to determine the sn-2 acyl chain specificity in mixtures of phospholipids. We performed μs timescale molecular dynamics (MD) simulations to reveal unique active site properties, especially how the precise hydrophobic cavity accommodation of the sn-2 acyl chain contributes to the stability of substrate binding and the specificity of each PLA2 for AA, EPA, or DHA. This study provides the first comprehensive picture of the unique substrate selectivity of each PLA2 for omega-3 and omega-6 fatty acids.
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Affiliation(s)
- Daiki Hayashi
- Department of Chemistry and Biochemistry and Department of Pharmacology, School of Medicine, University of California San Diego, La Jolla, CA, USA
| | - Varnavas D Mouchlis
- Department of Chemistry and Biochemistry and Department of Pharmacology, School of Medicine, University of California San Diego, La Jolla, CA, USA
| | - Edward A Dennis
- Department of Chemistry and Biochemistry and Department of Pharmacology, School of Medicine, University of California San Diego, La Jolla, CA, USA.
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Peng Z, Chang Y, Fan J, Ji W, Su C. Phospholipase A2 superfamily in cancer. Cancer Lett 2020; 497:165-177. [PMID: 33080311 DOI: 10.1016/j.canlet.2020.10.021] [Citation(s) in RCA: 55] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Revised: 10/11/2020] [Accepted: 10/14/2020] [Indexed: 12/12/2022]
Abstract
Phospholipase A2 enzymes (PLA2s) comprise a superfamily that is generally divided into six subfamilies known as cytosolic PLA2s (cPLA2s), calcium-independent PLA2s (iPLA2s), secreted PLA2s (sPLA2s), lysosomal PLA2s, platelet-activating factor (PAF) acetylhydrolases, and adipose specific PLA2s. Each subfamily consists of several isozymes that possess PLA2 activity. The first three PLA2 subfamilies play important roles in inflammation-related diseases and cancer. In this review, the roles of well-studied enzymes sPLA2-IIA, cPLA2α and iPLA2β in carcinogenesis and cancer development were discussed. sPLA2-IIA seems to play conflicting roles and can act as a tumor suppressor or a tumor promoter according to the cancer type, but cPLA2α and iPLA2β play protumorigenic role in most cancers. The mechanisms of PLA2-mediated signal transduction and crosstalk between cancer cells and endothelial cells in the tumor microenvironment are described. Moreover, the mechanisms by which PLA2s mediate lipid reprogramming and glycerophospholipid remodeling in cancer cells are illustrated. PLA2s as the upstream regulators of the arachidonic acid cascade are generally high expressed and activated in various cancers. Therefore, they can be considered as potential pharmacological targets and biomarkers in cancer. The detailed information summarized in this review may aid in understanding the roles of PLA2s in cancer, and provide new clues for the development of novel agents and strategies for tumor prevention and treatment.
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Affiliation(s)
- Zhangxiao Peng
- Department of Molecular Oncology, Eastern Hepatobiliary Surgical Hospital & National Center for Liver Cancer, Navy Military Medical University, Shanghai, 200438, China.
| | - Yanxin Chang
- Department of Biliary Tract Surgery IV, Eastern Hepatobiliary Surgical Hospital, Navy Military Medical University, Shanghai, 200438, China.
| | - Jianhui Fan
- Mengchao Hepatobiliary Hospital, Fujian Medical University, Fuzhou, 350025, Fujian Province, China.
| | - Weidan Ji
- Department of Molecular Oncology, Eastern Hepatobiliary Surgical Hospital & National Center for Liver Cancer, Navy Military Medical University, Shanghai, 200438, China.
| | - Changqing Su
- Department of Molecular Oncology, Eastern Hepatobiliary Surgical Hospital & National Center for Liver Cancer, Navy Military Medical University, Shanghai, 200438, China.
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Sundar S, Thangamani L, Manivel G, Kumar P, Piramanayagam S. Rv0807, a putative phospholipase A2 of Mycobacterium tuberculosis; Elucidation through sequence analysis, homology modeling, molecular docking and molecular dynamics studies of potential substrates and inhibitors. J Biomol Struct Dyn 2019; 38:3990-4004. [PMID: 31588859 DOI: 10.1080/07391102.2019.1677499] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Mycobacterium tuberculosis (Mtb) has the ability to scrounge off the host macrophages and create a cordial environment for its survival. Identification of mechanisms favoring this purpose leads to novel treatment strategies for tuberculosis. In this study through in silico approaches, we intend to identify the putative role for Rv0807 from Mtb and its essentiality for mycobacterium survival within the macrophages. Through sequence analysis, we hypothesize that Rv0807 could be a Phospholipase A2 of Mtb. Moreover, through in silico mutation studies we have predicted certain residues to be a part of the catalytic process of the Rv0807 homodimer. Rv0807 could be a potential drug target as it binds phosphatidylinositol-3-phosphate (PI3P) and could be involved in processing the host cell PI3Ps, thereby blocking the phagosomal maturation. A pharmacophore hypothesis was generated for the Rv0807 homodimer based on the ligand binding site and a set of Pretomanid related compounds were screened against the Rv0807 homodimer. The top five compounds which had better docking scores and good ADME properties were selected as best inhibitory compounds and analyzed further. Molecular dynamics (MD) studies of Rv0807 homodimer with PI3P and with the top scored compound in docking studies, demonstrated a lot of conformational changes in the protein structure as it gets occluded through the course of simulation. The movement of a loop atop the ligand binding site, suggests of a lid-like region as seen in many other phospholipases. MD simulation of the mutant structures was also performed and its effect on the protein conformational changes was discussed.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Shobana Sundar
- Department of Bioinformatics, Bharathiar University, Coimbatore, India
| | - Lokesh Thangamani
- Department of Bioinformatics, Bharathiar University, Coimbatore, India
| | - Gowdham Manivel
- Department of Bioinformatics, Bharathiar University, Coimbatore, India
| | - Praveen Kumar
- Department of Bioinformatics, Bharathiar University, Coimbatore, India
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Nikolaou A, Kokotou MG, Vasilakaki S, Kokotos G. Small-molecule inhibitors as potential therapeutics and as tools to understand the role of phospholipases A 2. Biochim Biophys Acta Mol Cell Biol Lipids 2019; 1864:941-956. [PMID: 30905350 PMCID: PMC7106526 DOI: 10.1016/j.bbalip.2018.08.009] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Revised: 08/10/2018] [Accepted: 08/16/2018] [Indexed: 11/20/2022]
Abstract
Phospholipase A2 (PLA2) enzymes are involved in various inflammatory pathological conditions including arthritis, cardiovascular and autoimmune diseases. The regulation of their catalytic activity is of high importance and a great effort has been devoted in developing synthetic inhibitors. We summarize the most important small-molecule synthetic PLA2 inhibitors developed to target each one of the four major types of human PLA2 (cytosolic cPLA2, calcium-independent iPLA2, secreted sPLA2, and lipoprotein-associated LpPLA2). We discuss recent applications of inhibitors to understand the role of each PLA2 type and their therapeutic potential. Potent and selective PLA2 inhibitors have been developed. Although some of them have been evaluated in clinical trials, none reached the market yet. Apart from their importance as potential medicinal agents, PLA2 inhibitors are excellent tools to unveil the role that each PLA2 type plays in cells and in vivo. Modern medicinal chemistry approaches are expected to generate improved PLA2 inhibitors as new agents to treat inflammatory diseases.
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Affiliation(s)
- Aikaterini Nikolaou
- Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis, Athens 15771, Greece
| | - Maroula G Kokotou
- Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis, Athens 15771, Greece
| | - Sofia Vasilakaki
- Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis, Athens 15771, Greece
| | - George Kokotos
- Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis, Athens 15771, Greece.
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7
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Phospholipases play multiple cellular roles including growth, stress tolerance, sexual development, and virulence in fungi. Microbiol Res 2018; 209:55-69. [DOI: 10.1016/j.micres.2017.12.012] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Revised: 12/21/2017] [Accepted: 12/31/2017] [Indexed: 12/16/2022]
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8
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Vasquez AM, Mouchlis VD, Dennis EA. Review of four major distinct types of human phospholipase A 2. Adv Biol Regul 2018; 67:212-218. [PMID: 29248300 PMCID: PMC5807221 DOI: 10.1016/j.jbior.2017.10.009] [Citation(s) in RCA: 69] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2017] [Revised: 10/20/2017] [Accepted: 10/20/2017] [Indexed: 12/18/2022]
Abstract
The phospholipase A2 superfamily of enzymes plays a significant role in the development and progression of numerous inflammatory diseases. Through their catalytic action on membrane phospholipids, phospholipases are the upstream regulators of the eicosanoid pathway releasing free fatty acids for cyclooxygenases, lipoxygenases, and cytochrome P450 enzymes which produce various well-known inflammatory mediators including leukotrienes, thromboxanes and prostaglandins. Elucidating the association of phospholipases A2 with the membrane, the extraction and binding of phospholipid substrates, and their interactions with small-molecule inhibitors is crucial for the development of new anti-inflammatory therapeutics. Studying phospholipases has been challenging because they act on the surface of cellular membranes and micelles. Multidisciplinary approaches including hydrogen/deuterium exchange mass spectrometry, molecular dynamics simulations, and other computer-aided drug design techniques have been successfully employed by our laboratory to study interactions of phospholipases with membranes, phospholipid substrates and inhibitors. This review summarizes the application of these techniques to study four human recombinant phospholipases A2.
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Affiliation(s)
- Alexis M Vasquez
- Department of Chemistry and Biochemistry and Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, CA 92093-0601, United States
| | - Varnavas D Mouchlis
- Department of Chemistry and Biochemistry and Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, CA 92093-0601, United States.
| | - Edward A Dennis
- Department of Chemistry and Biochemistry and Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, CA 92093-0601, United States.
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A New Generation of Arachidonic Acid Analogues as Potential Neurological Agent Targeting Cytosolic Phospholipase A 2. Sci Rep 2017; 7:13683. [PMID: 29057981 PMCID: PMC5651845 DOI: 10.1038/s41598-017-13996-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Accepted: 10/04/2017] [Indexed: 11/08/2022] Open
Abstract
Cytosolic phospholipase A2 (cPLA2) is an enzyme that releases arachidonic acid (AA) for the synthesis of eicosanoids and lysophospholipids which play critical roles in the initiation and modulation of oxidative stress and neuroinflammation. In the central nervous system, cPLA2 activation is implicated in the pathogenesis of various neurodegenerative diseases that involves neuroinflammation, thus making it an important pharmacological target. In this paper, a new class of arachidonic acid (AA) analogues was synthesized and evaluated for their ability to inhibit cPLA2. Several compounds were found to inhibit cPLA2 more strongly than arachidonyl trifluoromethyl ketone (AACOCF3), an inhibitor that is commonly used in the study of cPLA2-related neurodegenerative diseases. Subsequent experiments concluded that one of the inhibitors was found to be cPLA2-selective, non-cytotoxic, cell and brain penetrant and capable of reducing reactive oxygen species (ROS) and nitric oxide (NO) production in stimulated microglial cells. Computational studies were employed to understand how the compound interacts with cPLA2.
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2-Oxoesters: A Novel Class of Potent and Selective Inhibitors of Cytosolic Group IVA Phospholipase A 2. Sci Rep 2017; 7:7025. [PMID: 28765606 PMCID: PMC5539244 DOI: 10.1038/s41598-017-07330-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2017] [Accepted: 06/28/2017] [Indexed: 12/30/2022] Open
Abstract
Cytosolic phospholipase A2 (GIVA cPLA2) is the only PLA2 that exhibits a marked preference for hydrolysis of arachidonic acid containing phospholipid substrates releasing free arachidonic acid and lysophospholipids and giving rise to the generation of diverse lipid mediators involved in inflammatory conditions. Thus, the development of potent and selective GIVA cPLA2 inhibitors is of great importance. We have developed a novel class of such inhibitors based on the 2-oxoester functionality. This functionality in combination with a long aliphatic chain or a chain carrying an appropriate aromatic system, such as the biphenyl system, and a free carboxyl group leads to highly potent and selective GIVA cPLA2 inhibitors (XI(50) values 0.00007–0.00008) and docking studies aid in understanding this selectivity. A methyl 2-oxoester, with a short chain carrying a naphthalene ring, was found to preferentially inhibit the other major intracellular PLA2, the calcium-independent PLA2. In RAW264.7 macrophages, treatment with the most potent 2-oxoester GIVA cPLA2 inhibitor resulted in over 50% decrease in KLA-elicited prostaglandin D2 production. The novel, highly potent and selective GIVA cPLA2 inhibitors provide excellent tools for the study of the role of the enzyme and could contribute to the development of novel therapeutic agents for the treatment of inflammatory diseases.
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Zhu H, Liu P, Du J, Wang J, Jing Y, Zhang J, Gu W, Wang W, Meng Q. Identification of lysophospholipase protein from Spiroplasma eriocheiris and verification of its function. Microbiology (Reading) 2017; 163:175-184. [DOI: 10.1099/mic.0.000407] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Huanxi Zhu
- Laboratory of Animal Improvement and Reproduction, Institute of Animal Science, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, PR China
- Jiangsu Key Laboratory for Biodiversity & Biotechnology and Jiangsu Key Laboratory for Aquatic Crustacean Diseases, College of Life Sciences, Nanjing Normal University, Nanjing 210023, PR China
| | - Peng Liu
- Jiangsu Key Laboratory for Biodiversity & Biotechnology and Jiangsu Key Laboratory for Aquatic Crustacean Diseases, College of Life Sciences, Nanjing Normal University, Nanjing 210023, PR China
| | - Jie Du
- Jiangsu Key Laboratory for Biodiversity & Biotechnology and Jiangsu Key Laboratory for Aquatic Crustacean Diseases, College of Life Sciences, Nanjing Normal University, Nanjing 210023, PR China
| | - Jian Wang
- Jiangsu Key Laboratory for Biodiversity & Biotechnology and Jiangsu Key Laboratory for Aquatic Crustacean Diseases, College of Life Sciences, Nanjing Normal University, Nanjing 210023, PR China
| | - Yunting Jing
- Jiangsu Key Laboratory for Biodiversity & Biotechnology and Jiangsu Key Laboratory for Aquatic Crustacean Diseases, College of Life Sciences, Nanjing Normal University, Nanjing 210023, PR China
| | - Jia Zhang
- Jiangsu Key Laboratory for Biodiversity & Biotechnology and Jiangsu Key Laboratory for Aquatic Crustacean Diseases, College of Life Sciences, Nanjing Normal University, Nanjing 210023, PR China
| | - Wei Gu
- Co-Innovation Center for Marine Bio-Industry Technology of Jiangsu Province, Lianyungang, Jiangsu 222005, PR China
- Jiangsu Key Laboratory for Biodiversity & Biotechnology and Jiangsu Key Laboratory for Aquatic Crustacean Diseases, College of Life Sciences, Nanjing Normal University, Nanjing 210023, PR China
| | - Wen Wang
- Jiangsu Key Laboratory for Biodiversity & Biotechnology and Jiangsu Key Laboratory for Aquatic Crustacean Diseases, College of Life Sciences, Nanjing Normal University, Nanjing 210023, PR China
| | - Qingguo Meng
- Jiangsu Key Laboratory for Biodiversity & Biotechnology and Jiangsu Key Laboratory for Aquatic Crustacean Diseases, College of Life Sciences, Nanjing Normal University, Nanjing 210023, PR China
- Co-Innovation Center for Marine Bio-Industry Technology of Jiangsu Province, Lianyungang, Jiangsu 222005, PR China
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Kotani S, Izawa S, Komai N, Takayanagi A, Arioka M. Mitochondria-localized phospholipase A 2, AoPlaA, in Aspergillus oryzae displays phosphatidylethanolamine-specific activity and is involved in the maintenance of mitochondrial phospholipid composition. Fungal Genet Biol 2016; 96:1-11. [PMID: 27634187 DOI: 10.1016/j.fgb.2016.09.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Revised: 09/01/2016] [Accepted: 09/01/2016] [Indexed: 10/21/2022]
Abstract
In mammals, cytosolic phospholipases A2 (cPLA2s) play important physiological roles by releasing arachidonic acid, a precursor for bioactive lipid mediators, from the biological membranes. In contrast, fungal cPLA2-like proteins are much less characterized and their roles have remained elusive. AoPlaA is a cPLA2-like protein in the filamentous fungus Aspergillus oryzae which, unlike mammalian cPLA2, localizes to mitochondria. In this study, we investigated the biochemical and physiological functions of AoPlaA. Recombinant AoPlaA produced in E. coli displayed Ca2+-independent lipolytic activity. Mass spectrometry analysis demonstrated that AoPlaA displayed PLA2 activity to phosphatidylethanolamine (PE), but not to other phospholipids, and generated 1-acylated lysoPE. Catalytic site mutants of AoPlaA displayed almost no or largely reduced activity to PE. Consistent with PE-specific activity of AoPlaA, AoplaA-overexpressing strain showed decreased PE content in the mitochondrial fraction. In contrast, AoplaA-disruption strain displayed increased content of cardiolipin. AoplaA-overexpressing strain, but not its counterparts overexpressing the catalytic site mutants, exhibited retarded growth at low temperature, possibly because of the impairment of the mitochondrial function caused by excess degradation of PE. These results suggest that AoPlaA is a novel PE-specific PLA2 that plays a regulatory role in the maintenance of mitochondrial phospholipid composition.
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Affiliation(s)
- Shohei Kotani
- Department of Biotechnology, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Sho Izawa
- Department of Biotechnology, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Noriyuki Komai
- Department of Biotechnology, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Ayumi Takayanagi
- Department of Biotechnology, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Manabu Arioka
- Department of Biotechnology, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
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Dennis EA. Liberating Chiral Lipid Mediators, Inflammatory Enzymes, and LIPID MAPS from Biological Grease. J Biol Chem 2016; 291:24431-24448. [PMID: 27555328 DOI: 10.1074/jbc.x116.723791] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
In 1970, it was well accepted that the central role of lipids was in energy storage and metabolism, and it was assumed that amphipathic lipids simply served a passive structural role as the backbone of biological membranes. As a result, the scientific community was focused on nucleic acids, proteins, and carbohydrates as information-containing molecules. It took considerable effort until scientists accepted that lipids also "encode" specific and unique biological information and play a central role in cell signaling. Along with this realization came the recognition that the enzymes that act on lipid substrates residing in or on membranes and micelles must also have important signaling roles, spurring curiosity into their potentially unique modes of action differing from those acting on water-soluble substrates. This led to the creation of the concept of "surface dilution kinetics" for describing the mechanism of enzymes acting on lipid substrates, as well as the demonstration that lipid enzymes such as phospholipase A2 (PLA2) contain allosteric activator sites for specific phospholipids as well as for membranes. As our understanding of phospholipases advanced, so did the understanding that many of the lipids released by these enzymes are chiral information-containing signaling molecules; for example, PLA2 regulates the generation of precursors for the biosynthesis of eicosanoids and other bioactive lipid mediators of inflammation and resolution underlying disease progression. The creation of the LIPID MAPS initiative in 2003 and the ensuing development of the lipidomics field have revealed that lipid metabolites are central to human metabolism. Today lipids are recognized as key mediators of health and disease as we enter a new era of biomarkers and personalized medicine. This article is my personal "reflection" on these scientific advances.
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Affiliation(s)
- Edward A Dennis
- From the Department of Chemistry and Biochemistry and Department of Pharmacology, School of Medicine, University of California at San Diego, La Jolla, California 92093-0601.
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14
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Chiorazzo MG, Bloch NB, Popov AV, Delikatny EJ. Synthesis and Evaluation of Cytosolic Phospholipase A(2) Activatable Fluorophores for Cancer Imaging. Bioconjug Chem 2015; 26:2360-70. [PMID: 26426140 DOI: 10.1021/acs.bioconjchem.5b00417] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Activatable fluorophores selective to cytosolic phospholipase A2 (cPLA2) were synthesized and evaluated for their ability to image triple negative breast cancer cells. The activatable constructs were synthesized by esterification of a small molecule fluorophore with a fatty acid resulting in ablated fluorescence. Selectivity for cPLA2 was generated through the choice of fluorophore and fatty acid. Esterification with arachidonic acid was sufficient to impart specificity to cPLA2 when compared to esterification with palmitic acid. In vitro analysis of probes incorporated into phosphatidylcholine liposomes demonstrated that a nonselective phospholipase (sPLA2 group IB) was able to hydrolyze both arachidonate and palmitate coupled fluorophores resulting in the generation of fluorescence. Of the four fluorophores tested, DDAO (7-hydroxy-9H-(1,3-dichloro-9,9-dimethylacridin-2-one)) was observed to perform optimally in vitro and was analyzed further in 4175-Luc+ cells, a metastatic triple negative human breast cancer cell line expressing high levels of cPLA2. In contrast to the in vitro analysis, DDAO arachidonate was shown to activate selectively in 4175-Luc+ cells compared to the control DDAO palmitate as measured by fluorescence microscopy and quantitated with fluorescence spectroscopy. The addition of two agents known to activate cPLA2 enhanced DDAO arachidonate fluorescence without inducing any change to DDAO palmitate. Inhibition of cPLA2 resulted in reduced fluorescence of DDAO arachidonate but not DDAO palmitate. Together, we report the synthesis of a cPLA2 selective activatable fluorophore capable of detecting cPLA2 in triple negative breast cancer cells.
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Affiliation(s)
- Michael G Chiorazzo
- Department of Pharmacology, University of Pennsylvania , Philadelphia, Pennsylvania 19104, United States.,Department of Radiology, University of Pennsylvania , Philadelphia, Pennsylvania 19104, United States
| | - Noah B Bloch
- Department of Radiology, University of Pennsylvania , Philadelphia, Pennsylvania 19104, United States
| | - Anatoliy V Popov
- Department of Radiology, University of Pennsylvania , Philadelphia, Pennsylvania 19104, United States
| | - Edward J Delikatny
- Department of Radiology, University of Pennsylvania , Philadelphia, Pennsylvania 19104, United States
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15
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Leslie CC. Cytosolic phospholipase A₂: physiological function and role in disease. J Lipid Res 2015; 56:1386-402. [PMID: 25838312 DOI: 10.1194/jlr.r057588] [Citation(s) in RCA: 269] [Impact Index Per Article: 29.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2015] [Indexed: 02/06/2023] Open
Abstract
The group IV phospholipase A2 (PLA2) family is comprised of six intracellular enzymes (GIVA, -B, -C, -D, -E, and -F) commonly referred to as cytosolic PLA2 (cPLA2)α, -β, -γ, -δ, -ε, and -ζ. They contain a Ser-Asp catalytic dyad and all except cPLA2γ have a C2 domain, but differences in their catalytic activities and subcellular localization suggest unique regulation and function. With the exception of cPLA2α, the focus of this review, little is known about the in vivo function of group IV enzymes. cPLA2α catalyzes the hydrolysis of phospholipids to arachidonic acid and lysophospholipids that are precursors of numerous bioactive lipids. The regulation of cPLA2α is complex, involving transcriptional and posttranslational processes, particularly increases in calcium and phosphorylation. cPLA2α is a highly conserved widely expressed enzyme that promotes lipid mediator production in human and rodent cells from a variety of tissues. The diverse bioactive lipids produced as a result of cPLA2α activation regulate normal physiological processes and disease pathogenesis in many organ systems, as shown using cPLA2α KO mice. However, humans recently identified with cPLA2α deficiency exhibit more pronounced effects on health than observed in mice lacking cPLA2α, indicating that much remains to be learned about this interesting enzyme.
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Affiliation(s)
- Christina C Leslie
- Department of Pediatrics, National Jewish Health, Denver, CO 80206; and Departments of Pathology and Pharmacology, University of Colorado Denver, Aurora, CO 80045
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16
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Grandits M, Oostenbrink C. Selectivity of cytosolic phospholipase A2 type IV toward arachidonyl phospholipids. J Mol Recognit 2015; 28:447-57. [PMID: 25703463 DOI: 10.1002/jmr.2462] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2014] [Revised: 01/07/2015] [Accepted: 01/07/2015] [Indexed: 11/06/2022]
Abstract
Cytosolic phospholipase A2 (cPLA2 ) is an interesting protein involved in inflammatory processes and various diseases. Its catalytic mechanism as well as its substrate specificity for arachidonyl phospholipids is not typical for other phospolipases. Furthermore, a lid structure, which ensures a hydrophilic surface of the protein without any substrate bound and the movement of this flexible loop to make the hydrophobic active site accessible, is of high interest. Therefore, the focus of this work was to determine the binding mode of cPLA2 with various substrates, such as arachidonic acid, a synthetic inhibitor, a saturated phospholipid, and most importantly an arachidonyl phospholipid. To understand the selectivity of the protein toward the arachidonyl phospholipid and the interaction in a protein-ligand complex, molecular dynamics simulations were performed using the GROMOS suite of simulation programs. The simulations provide insight into the protein and showed that selective binding of arachidonyl phospholipids is because of the shape of the sn-2 tail. The amino acids Asn555 and Ala578 are involved in the strongest interactions observed in the protein-ligand complexes.
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Affiliation(s)
- Melanie Grandits
- Department of Material Sciences and Process Engineering, Institute of Molecular Modeling and Simulation, University of Natural Resources and Life Sciences Vienna, Muthgasse 18, 1190, Vienna, Austria
| | - Chris Oostenbrink
- Department of Material Sciences and Process Engineering, Institute of Molecular Modeling and Simulation, University of Natural Resources and Life Sciences Vienna, Muthgasse 18, 1190, Vienna, Austria
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17
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Mouchlis VD, Bucher D, McCammon JA, Dennis EA. Membranes serve as allosteric activators of phospholipase A2, enabling it to extract, bind, and hydrolyze phospholipid substrates. Proc Natl Acad Sci U S A 2015; 112:E516-25. [PMID: 25624474 PMCID: PMC4330758 DOI: 10.1073/pnas.1424651112] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Defining the molecular details and consequences of the association of water-soluble proteins with membranes is fundamental to understanding protein-lipid interactions and membrane functioning. Phospholipase A2 (PLA2) enzymes, which catalyze the hydrolysis of phospholipid substrates that compose the membrane bilayers, provide the ideal system for studying protein-lipid interactions. Our study focuses on understanding the catalytic cycle of two different human PLA2s: the cytosolic Group IVA cPLA2 and calcium-independent Group VIA iPLA2. Computer-aided techniques guided by deuterium exchange mass spectrometry data, were used to create structural complexes of each enzyme with a single phospholipid substrate molecule, whereas the substrate extraction process was studied using steered molecular dynamics simulations. Molecular dynamic simulations of the enzyme-substrate-membrane systems revealed important information about the mechanisms by which these enzymes associate with the membrane and then extract and bind their phospholipid substrate. Our data support the hypothesis that the membrane acts as an allosteric ligand that binds at the allosteric site of the enzyme's interfacial surface, shifting its conformation from a closed (inactive) state in water to an open (active) state at the membrane interface.
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Affiliation(s)
| | | | - J Andrew McCammon
- Departments of Pharmacology and Chemistry and Biochemistry, and Howard Hughes Medical Institute, University of California, San Diego, La Jolla, CA 92093-0601
| | - Edward A Dennis
- Departments of Pharmacology and Chemistry and Biochemistry, and
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18
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Ubiquitin activates patatin-like phospholipases from multiple bacterial species. J Bacteriol 2014; 197:529-41. [PMID: 25404699 DOI: 10.1128/jb.02402-14] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Phospholipase A2 enzymes are ubiquitously distributed throughout the prokaryotic and eukaryotic kingdoms and are utilized in a wide array of cellular processes and physiological and immunological responses. Several patatin-like phospholipase homologs of ExoU from Pseudomonas aeruginosa were selected on the premise that ubiquitin activation of this class of bacterial enzymes was a conserved process. We found that ubiquitin activated all phospholipases tested in both in vitro and in vivo assays via a conserved serine-aspartate catalytic dyad. Ubiquitin chains versus monomeric ubiquitin were superior in inducing catalysis, and ubiquitin-like proteins failed to activate phospholipase activity. Toxicity studies in a prokaryotic dual-expression system grouped the enzymes into high- and low-toxicity classes. Toxicity measured in eukaryotic cells also suggested a two-tiered classification but was not predictive of the severity of cellular damage, suggesting that each enzyme may correspond to unique properties perhaps based on its specific biological function. Additional studies on lipid binding preference suggest that some enzymes in this family may be differentially sensitive to phosphatidyl-4,5-bisphosphate in terms of catalytic activation enhancement and binding affinity. Further analysis of the function and amino acid sequences of this enzyme family may lead to a useful approach to formulating a unifying model of how these phospholipases behave after delivery into the cytoplasmic compartment.
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19
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Mouchlis VD, Michopoulou V, Constantinou-Kokotou V, Mavromoustakos T, Dennis EA, Kokotos G. Binding conformation of 2-oxoamide inhibitors to group IVA cytosolic phospholipase A2 determined by molecular docking combined with molecular dynamics. J Chem Inf Model 2012; 52:243-54. [PMID: 22196172 DOI: 10.1021/ci2005093] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The group IVA cytosolic phospholipase A(2) (GIVA cPLA(2)) plays a central role in inflammation. Long chain 2-oxoamides constitute a class of potent GIVA cPLA(2) inhibitors that exhibit potent in vivo anti-inflammatory and analgesic activity. We have now gained insight into the binding of 2-oxoamide inhibitors in the GIVA cPLA(2) active site through a combination of molecular docking calculations and molecular dynamics simulations. Recently, the location of the 2-oxoamide inhibitor AX007 within the active site of the GIVA cPLA(2) was determined using a combination of deuterium exchange mass spectrometry followed by molecular dynamics simulations. After the optimization of the AX007-GIVA cPLA(2) complex using the docking algorithm Surflex-Dock, a series of additional 2-oxoamide inhibitors have been docked in the enzyme active site. The calculated binding affinity presents a good statistical correlation with the experimental inhibitory activity (r(2) = 0.76, N = 11). A molecular dynamics simulation of the docking complex of the most active compound has revealed persistent interactions of the inhibitor with the enzyme active site and proves the stability of the docking complex and the validity of the binding suggested by the docking calculations. The combination of molecular docking calculations and molecular dynamics simulations is useful in defining the binding of small-molecule inhibitors and provides a valuable tool for the design of new compounds with improved inhibitory activity against GIVA cPLA(2).
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Affiliation(s)
- Varnavas D Mouchlis
- Laboratory of Organic Chemistry, Department of Chemistry, University of Athens, Panepistimiopolis, Athens 15771, Greece
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Abstract
Phospholipids are present in all living organisms. They are a major component of all biological membranes, along with glycolipids and cholesterol. Enzymes aimed at cleaving the various bonds in phospholipids, namely phospholipases, are consequently widespread in nature, playing very diverse roles from aggression in snake venom to signal transduction, lipid mediators production, and digestion in humans. Although all phospholipases target phospholipids as substrates, they vary in the site of action on the phospholipids molecules, physiological function, mode of action, and their regulation. Significant studies on phospholipases characterization, physiological role, and industrial potential have been conducted worldwide. Some of them have been directed for biotechnological advances, such as gene discovery and functional enhancement by protein engineering. Others reported phospholipases as virulence factors and major causes of pathophysiological effects. In this introductory chapter, we provide brief details of different phospholipases.
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Affiliation(s)
- Ahmed Aloulou
- National School of Engineers of Sfax, University of Sfax, Sfax, Tunisia.
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21
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Dennis EA, Cao J, Hsu YH, Magrioti V, Kokotos G. Phospholipase A2 enzymes: physical structure, biological function, disease implication, chemical inhibition, and therapeutic intervention. Chem Rev 2011; 111:6130-85. [PMID: 21910409 PMCID: PMC3196595 DOI: 10.1021/cr200085w] [Citation(s) in RCA: 820] [Impact Index Per Article: 63.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Edward A. Dennis
- Department of Chemistry and Biochemistry and Pharmacology, School of Medicine, University of California, San Diego, La Jolla, California 92093-0601
| | - Jian Cao
- Department of Chemistry and Biochemistry and Pharmacology, School of Medicine, University of California, San Diego, La Jolla, California 92093-0601
| | - Yuan-Hao Hsu
- Department of Chemistry and Biochemistry and Pharmacology, School of Medicine, University of California, San Diego, La Jolla, California 92093-0601
| | - Victoria Magrioti
- Laboratory of Organic Chemistry, Department of Chemistry, University of Athens, Panepistimiopolis, Athens 15771, Greece
| | - George Kokotos
- Laboratory of Organic Chemistry, Department of Chemistry, University of Athens, Panepistimiopolis, Athens 15771, Greece
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22
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Madsen JJ, Linderoth L, Subramanian AK, Andresen TL, Peters GH. Secretory phospholipase A2 activity toward diverse substrates. J Phys Chem B 2011; 115:6853-61. [PMID: 21561115 DOI: 10.1021/jp112137b] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We have studied secretory phospholipase A(2)-IIA (sPLA(2)) activity toward different phospholipid analogues by performing biophysical characterizations and molecular dynamics simulations. The phospholipids were natural substrates, triple alkyl phospholipids, a prodrug anticancer etherlipid, and an inverted ester. The latter were included to study head group-enzyme interactions. Our simulation results show that the lipids are optimally placed into the binding cleft and that water molecules can freely reach the active site through a well-defined pathway; both are indicative that these substrates are efficiently hydrolyzed, which is in good agreement with our experimental data. The phospholipid analogue with three alkyl side chains forms aggregates of different shapes with no well-defined sizes due to its cone-shape structure. Phosphatidylglycerol and phosphatidylcholine head groups interact with specific charged residues, but relatively large fluctuations are observed, suggesting that these interactions are not necessarily important for stabilizing substrate binding to the enzyme.
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Affiliation(s)
- Jesper J Madsen
- Department of Chemistry, Technical University of Denmark, Kgs. Lyngby, Denmark
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23
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Djordjevic JT. Role of phospholipases in fungal fitness, pathogenicity, and drug development - lessons from cryptococcus neoformans. Front Microbiol 2010; 1:125. [PMID: 21687772 PMCID: PMC3109512 DOI: 10.3389/fmicb.2010.00125] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2010] [Accepted: 10/25/2010] [Indexed: 11/13/2022] Open
Abstract
Many pathogenic microbes, including many fungi, produce phospholipases which facilitate survival of the pathogen in vivo, invasion and dissemination throughout the host, expression of virulence traits and evasion of host immune defense mechanisms. These phospholipases are either secreted or produced intracellularly and act by physically disrupting host membranes, and/or by affecting fungal cell signaling and production of immunomodulatory effectors. Many of the secreted phospholipases acquire a glycosylphosphatidylinositol sorting motif to facilitate membrane and/or cell wall association and secretion. This review focuses primarily on the role of two members of the phospholipase enzyme family, phospholipase B (Plb) and phosphatidylinositol (PI)-specific phospholipase C (PI-C/Plc), in fungal pathogenesis and in particular, what has been learnt about their function from studies performed in the model pathogenic yeast, Cryptococcus neoformans. These studies have revealed how Plb has adapted to become an important part of the virulence repertoire of pathogenic fungi and how its secretion is regulated. They have also provided valuable insight into how the intracellular enzyme, Plc1, contributes to fungal fitness and pathogenicity – via a putative role in signal transduction pathways that regulate the production of stress-protecting pigments, polysaccharide capsule, cell wall integrity, and adaptation to growth at host temperature. Finally, this review will address the role fungal phospholipases have played in the development of a new class of antifungal drugs, which mimic their phospholipid substrates.
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Affiliation(s)
- Julianne Teresa Djordjevic
- Fungal Pathogenesis Laboratory, Centre for Infectious Diseases and Microbiology, Sydney Medical School-Western, Westmead Millennium Institute, University of Sydney at Westmead Hospital Westmead, NSW, Australia
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24
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Takaya K, Higuchi Y, Kitamoto K, Arioka M. A cytosolic phospholipase A2-like protein in the filamentous fungusAspergillus oryzaelocalizes to the intramembrane space of the mitochondria. FEMS Microbiol Lett 2009; 301:201-9. [DOI: 10.1111/j.1574-6968.2009.01818.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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25
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Pietro ES, Capestrano M, Polishchuk EV, DiPentima A, Trucco A, Zizza P, Mariggiò S, Pulvirenti T, Sallese M, Tete S, Mironov AA, Leslie CC, Corda D, Luini A, Polishchuk RS. Group IV phospholipase A(2)alpha controls the formation of inter-cisternal continuities involved in intra-Golgi transport. PLoS Biol 2009; 7:e1000194. [PMID: 19753100 PMCID: PMC2732982 DOI: 10.1371/journal.pbio.1000194] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2008] [Accepted: 07/31/2009] [Indexed: 11/18/2022] Open
Abstract
The organization of intra-Golgi trafficking and the nature of the transport intermediates involved (e.g., vesicles, tubules, or tubular continuities) remain incompletely understood. It was recently shown that successive cisternae in the Golgi stack are interconnected by membrane tubules that form during the arrival of transport carriers from the endoplasmic reticulum. Here, we examine the mechanisms of generation and the function of these tubules. In principle, tubule formation might depend on several protein- and/or lipid-based mechanisms. Among the latter, we have studied the phospholipase A(2) (PLA(2))-mediated generation of wedge-shaped lysolipids, with the resulting local positive membrane curvature. We show that the arrival of cargo at the Golgi complex induces the recruitment of Group IVA Ca(2+)-dependent, cytosolic PLA(2) (cPLA(2)alpha) onto the Golgi complex itself, and that this cPLA(2)alpha is required for the formation of the traffic-dependent intercisternal tubules and for intra-Golgi transport. In contrast, silencing of cPLA(2)alpha has no inhibitory effects on peri-Golgi vesicles. These findings identify cPLA(2)alpha as the first component of the machinery that is responsible for the formation of intercisternal tubular continuities and support a role for these continuities in transport through the Golgi complex.
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Affiliation(s)
- Enrica San Pietro
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Chieti, Italy
| | | | - Elena V. Polishchuk
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Chieti, Italy
| | - Alessio DiPentima
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Chieti, Italy
| | - Alvar Trucco
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Chieti, Italy
| | - Pasquale Zizza
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Chieti, Italy
| | - Stefania Mariggiò
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Chieti, Italy
| | - Teodoro Pulvirenti
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Chieti, Italy
| | - Michele Sallese
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Chieti, Italy
| | - Stefano Tete
- Department of Oral Sciences, University “G. D'Annunzio”, Chieti, Italy
| | - Alexander A. Mironov
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Chieti, Italy
| | - Christina C. Leslie
- Department of Pediatrics, National Jewish Medical and Research Center, Denver, Colorado, United States of America
| | - Daniela Corda
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Chieti, Italy
| | - Alberto Luini
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Chieti, Italy
- Telethon Institute of Genetics and Medicine, Naples, Italy
- * E-mail: (AL); (RSP)
| | - Roman S. Polishchuk
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Chieti, Italy
- Telethon Institute of Genetics and Medicine, Naples, Italy
- * E-mail: (AL); (RSP)
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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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27
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Burke JE, Babakhani A, Gorfe AA, Kokotos G, Li S, Woods VL, McCammon JA, Dennis EA. Location of inhibitors bound to group IVA phospholipase A2 determined by molecular dynamics and deuterium exchange mass spectrometry. J Am Chem Soc 2009; 131:8083-91. [PMID: 19459633 DOI: 10.1021/ja900098y] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
An analysis of group IVA (GIVA) phospholipase A(2) (PLA(2)) inhibitor binding was conducted using a combination of deuterium exchange mass spectrometry (DXMS) and molecular dynamics (MD). Models of the GIVA PLA(2) inhibitors pyrrophenone and the 2-oxoamide AX007 docked into the protein were designed on the basis of deuterium exchange results, and extensive molecular dynamics simulations were run to determine protein-inhibitor contacts. The models show that both inhibitors interact with key residues that also exhibit changes in deuterium exchange upon inhibitor binding. Pyrrophenone is bound to the protein through numerous hydrophobic residues located distal from the active site, while the oxoamide is bound mainly through contacts near the active site. We also show differences in protein dynamics around the active site between the two inhibitor-bound complexes. This combination of computational and experimental methods is useful in defining more accurate inhibitor binding sites and can be used in the generation of better inhibitors against GIVA PLA(2).
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Affiliation(s)
- John E Burke
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive MC 0601, La Jolla, California 92093-0601, USA
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28
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Cytosolic phospholipase A2: a member of the signalling pathway of a new G protein alpha subunit in Sporothrix schenckii. BMC Microbiol 2009; 9:100. [PMID: 19454031 PMCID: PMC2694196 DOI: 10.1186/1471-2180-9-100] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2008] [Accepted: 05/19/2009] [Indexed: 11/25/2022] Open
Abstract
Background Sporothrix schenckii is a pathogenic dimorphic fungus, the etiological agent of sporotrichosis, a lymphocutaneous disease that can remain localized or can disseminate, involving joints, lungs, and the central nervous system. Pathogenic fungi use signal transduction pathways to rapidly adapt to changing environmental conditions and S. schenckii is no exception. S. schenckii yeast cells, either proliferate (yeast cell cycle) or engage in a developmental program that includes proliferation accompanied by morphogenesis (yeast to mycelium transition) depending on the environmental conditions. The principal intracellular receptors of environmental signals are the heterotrimeric G proteins, suggesting their involvement in fungal dimorphism and pathogenicity. Identifying these G proteins in fungi and their involvement in protein-protein interactions will help determine their role in signal transduction pathways. Results In this work we describe a new G protein α subunit gene in S. schenckii, ssg-2. The cDNA sequence of ssg-2 revealed a predicted open reading frame of 1,065 nucleotides encoding a 355 amino acids protein with a molecular weight of 40.9 kDa. When used as bait in a yeast two-hybrid assay, a cytoplasmic phospholipase A2 catalytic subunit was identified as interacting with SSG-2. The sspla2 gene, revealed an open reading frame of 2538 bp and encoded an 846 amino acid protein with a calculated molecular weight of 92.62 kDa. The principal features that characterize cPLA2 were identified in this enzyme such as a phospholipase catalytic domain and the characteristic invariable arginine and serine residues. A role for SSPLA2 in the control of dimorphism in S. schenckii is suggested by observing the effects of inhibitors of the enzyme on the yeast cell cycle and the yeast to mycelium transition in this fungus. Phospholipase A2 inhibitors such as AACOCF3 (an analogue of archidonic acid) and isotetrandrine (an inhibitor of G protein PLA2 interactions) were found to inhibit budding by yeasts induced to re-enter the yeast cell cycle and to stimulate the yeast to mycelium transition showing that this enzyme is necessary for the yeast cell cycle. Conclusion A new G protein α subunit gene was characterized in S. schenckii and protein-protein interactions studies revealed this G protein alpha subunit interacts with a cPLA2 homologue. The PLA2 homologue reported here is the first phospholipase identified in S. schenckii and the first time a PLA2 homologue is identified as interacting with a G protein α subunit in a pathogenic dimorphic fungus, establishing a relationship between these G proteins and the pathogenic potential of fungi. This cPLA2 homologue is known to play a role in signal transduction and fungal pathogenesis. Using cPLA2 inhibitors, this enzyme was found to affect dimorphism in S. schenckii and was found to be necessary for the development of the yeast or pathogenic form of the fungus.
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29
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Abstract
The phospholipase A(2) (PLA(2)) superfamily consists of many different groups of enzymes that catalyze the hydrolysis of the sn-2 ester bond in a variety of different phospholipids. The products of this reaction, a free fatty acid, and lysophospholipid have many different important physiological roles. There are five main types of PLA(2): the secreted sPLA(2)'s, the cytosolic cPLA(2)'s, the Ca(2+)independent iPLA(2)'s, the PAF acetylhydrolases, and the lysosomal PLA(2)'s. This review focuses on the superfamily of PLA(2) enzymes, and then uses three specific examples of these enzymes to examine the differing biochemistry of the three main types of these enzymes. These three examples are the GIA cobra venom PLA(2), the GIVA cytosolic cPLA(2), and the GVIA Ca(2+)-independent iPLA(2).
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Affiliation(s)
- John E Burke
- Department of Chemistry and Biochemistry, School of Medicine, University of California, La Jolla, San Diego, CA 92093-0601, USA
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Phospholipases A(2) in the genome of the sea anemone Nematostella vectensis. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY D-GENOMICS & PROTEOMICS 2008; 3:226-33. [PMID: 20483221 DOI: 10.1016/j.cbd.2008.04.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2008] [Revised: 04/27/2008] [Accepted: 04/28/2008] [Indexed: 11/22/2022]
Abstract
The genome of the sea anemone Nematostella vectensis (Nv) (Cnidaria, Anthozoa) was sequenced recently (Putnam et al., Science 317: 86, 2007). In the current study, 22 proteins of Nv were identified as putative phospholipases A(2) (PLA(2)) that showed up to 40-50% sequence identity with secreted or intracellular PLA(2)s including those of humans. Nv1-Nv6 PLA(2)s have identity with secreted human group (G)IB and GIIA PLA(2)s and PLA(2)s of the sea anemones Adamsia carciniopados and Urticina crassicornis. Nv7 and Nv8 PLA(2)s have identity with human and bee venom GIII PLA(2)s and Nv9 PLA(2) with GXIIA PLA(2). Nv10-Nv13 PLA(2)s show identity with GIX PLA(2) of Conus magus and bacterial PLA(2)s but no significant identity with any human PLA(2). Nv14 has identity with intracellular GIV PLA(2), Nv15 with GVII PLA(2), Nv16 and Nv17 with GVIII PLA(2), Nv18-Nv20 with GVI PLA(2), and Nv21 and Nv22 with patatin, respectively. The observations indicate that the cnidarian phospholipasome contains a rich array of orthologs of most types of animal PLA(2)s, and that many of the PLA(2)-driven vital functions prevail in these ancient metazoans. Cnidarian PLA(2)s may be considered as evolutionary precursors of PLA(2)s of higher animals.
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31
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Jones PM, Turner KM, Djordjevic JT, Sorrell TC, Wright LC, George AM. Role of Conserved Active Site Residues in Catalysis by Phospholipase B1 from Cryptococcus neoformans. Biochemistry 2007; 46:10024-32. [PMID: 17685590 DOI: 10.1021/bi7009508] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Phospholipase B1 (PLB1), secreted by the pathogenic yeast Cryptococcus neoformans, has an established role in virulence. Although the mechanism of its phospholipase B, lysophospholipase, and lysophospholipase transacylase activities is unknown, it possesses lipase, subtilisin protease aspartate, and phospholipase motifs containing putative catalytic residues S146, D392, and R108, respectively, conserved in fungal PLBs and essential for human cytosolic phospholipase A2 (cPLA2) catalysis. To determine the role of these residues in PLB1 catalysis, each was substituted with alanine, and the mutant cDNAs were expressed in Saccharomyces cerevisiae. The mutant PLB1s were deficient in all three enzymatic activities. As the active site structure of PLB1 is unknown, a homology model was developed, based on the X-ray structure of the cPLA2 catalytic domain. This shows that the two proteins share a closely related fold, with the three catalytic residues located in identical positions as part of a single active site, with S146 and D392 forming a catalytic dyad. The model suggests that PLB1 lacks the "lid" region which occludes the cPLA2 active site and provides a mechanism of interfacial activation. In silico substrate docking studies with cPLA2 reveal the binding mode of the lipid headgroup, confirming the catalytic dyad mechanism for the cleavage of the sn-2 ester bond within one of two separate binding tracts for the lipid acyl chains. Residues specific for binding arachidonic and palmitic acids, preferred substrates for cPLA2 and PLB1, respectively, are identified. These results provide an explanation for differences in substrate specificity between lipases sharing the cPLA2 catalytic domain fold and for the differential effect of inhibitors on PLB1 enzymatic activities.
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Affiliation(s)
- Peter M Jones
- Department of Medical and Molecular Biosciences, University of Technology Sydney, P.O. Box 123, Broadway, NSW 2007, Australia
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32
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Six DA, Barbayianni E, Loukas V, Constantinou-Kokotou V, Hadjipavlou-Litina D, Stephens D, Wong AC, Magrioti V, Moutevelis-Minakakis P, Baker SF, Dennis EA, Kokotos G. Structure-activity relationship of 2-oxoamide inhibition of group IVA cytosolic phospholipase A2 and group V secreted phospholipase A2. J Med Chem 2007; 50:4222-35. [PMID: 17672443 DOI: 10.1021/jm0613673] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The Group IVA cytosolic phospholipase A2 (GIVA cPLA2) is a key provider of substrates for the production of eicosanoids and platelet-activating factor. We explored the structure-activity relationship of 2-oxoamide-based compounds and GIVA cPLA2 inhibition. The most potent inhibitors are derived from delta- and gamma-amino acid-based 2-oxoamides. The optimal side-chain moiety is a short nonpolar aliphatic chain. All of the newly developed 2-oxoamides as well as those previously described have now been tested with the human Group V secreted PLA2 (GV sPLA2) and the human Group VIA calcium-independent PLA2 (GVIA iPLA2). Only one 2-oxoamide compound had appreciable inhibition of GV sPLA2, and none of the potent GIVA cPLA2 inhibitors inhibited either GV sPLA2 or GVIA iPLA2. Two of these specific GIVA cPLA2 inhibitors were also found to have potent therapeutic effects in animal models of pain and inflammation at dosages well below the control nonsteroidal anti-inflammatory drugs.
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Affiliation(s)
- David A Six
- Department of Chemistry and Biochemistry and Department of Pharmacology, School of Medicine, MC 0601, University of California, San Diego, La Jolla, California 92093-0601, USA
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Ma C, Hu X, Hu F, Li Y, Chen X, Zhou Z, Lu F, Xu J, Wu Z, Yu X. Molecular characterization and serodiagnosis analysis of a novel lysophospholipase from Clonorchis sinensis. Parasitol Res 2007; 101:419-25. [PMID: 17318582 DOI: 10.1007/s00436-007-0481-3] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2007] [Accepted: 01/25/2007] [Indexed: 01/25/2023]
Abstract
A cDNA clone encoding a novel lysophospholipase with a predicted molecular weight of 25.2 kDa was isolated from a Clonorchis sinensis adult cDNA library. The enzyme activity of the recombinant protein expressed in Escherichia coli was determined using phosphatidylcholine and lysophosphatidylcholine as substrates. Western blotting analysis indicated that it belonged to excretory/secretory proteins of the adults. The sensitivity and specificity of the recombinant antigen for serodiagnosis were evaluated with immunoglobulin enzyme-linked immunosorbent assay using serum samples from 20 patients with clonorchiasis and 20 patients with schistosomiasis. The sensitivity (75%) and specificity (80%) of the recombinant protein were comparable to those of crude extracts, at 65 and 82.5%, respectively. The sensitivity of the recombinant protein was 77% using 100 serum samples of clonorchiasis patients with various parasite burden. The results suggested that the recombinant lysophospholipase protein was not a satisfactory candidate for diagnosis of clonorchiasis, although it might be an excretory/secretory protein.
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Affiliation(s)
- Changling Ma
- Department of Parasitology, Zhongshan School of Medicine, SunYat-sen University, Guangzhou, 510080, People's Republic of China
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Köhler GA, Brenot A, Haas-Stapleton E, Agabian N, Deva R, Nigam S. Phospholipase A2 and phospholipase B activities in fungi. BIOCHIMICA ET BIOPHYSICA ACTA 2006; 1761:1391-9. [PMID: 17081801 PMCID: PMC2077850 DOI: 10.1016/j.bbalip.2006.09.011] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2006] [Revised: 09/20/2006] [Accepted: 09/25/2006] [Indexed: 10/24/2022]
Abstract
As saprophytes or disease causing microorganisms, fungi acquire nutrients from dead organic material or living host organisms. Lipids as structural components of cell membranes and storage compartments play an important role as energy-rich food source. In recent years, it also has become clear that lipids have a wide range of bioactive properties including signal transduction and cell to cell communication. Thus, it is not surprising that fungi possess a broad range of hydrolytic enzymes that attack neutral lipids and phospholipids. Especially during infection of a mammalian host, phospholipase A(2) (PLA(2)) enzymes released by fungi could play important roles not only for nutrient acquisition and tissue invasion, but for intricate modulation of the host's immune response. Sequencing of fungal genomes has revealed a wide range of genes encoding PLA(2) activities in fungi. We are just beginning to become aware of the significance these enzymes could have for the fungal cells and their interaction with the host.
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Affiliation(s)
- Gerwald A. Köhler
- Department of Cell and Tissue Biology, University of California, San Francisco, U.S.A
| | - Audrey Brenot
- Department of Cell and Tissue Biology, University of California, San Francisco, U.S.A
| | - Eric Haas-Stapleton
- Department of Cell and Tissue Biology, University of California, San Francisco, U.S.A
| | - Nina Agabian
- Department of Cell and Tissue Biology, University of California, San Francisco, U.S.A
| | - Rupal Deva
- Eicosanoid Research Division and Center for Experimental Gynecology & Breast Research, Charité - Univ.-Klinikum Benjamin Franklin, D-12200 Berlin, Germany
| | - Santosh Nigam
- Eicosanoid Research Division and Center for Experimental Gynecology & Breast Research, Charité - Univ.-Klinikum Benjamin Franklin, D-12200 Berlin, Germany
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35
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Stephens D, Barbayianni E, Constantinou-Kokotou V, Peristeraki A, Six DA, Cooper J, Harkewicz R, Deems RA, Dennis EA, Kokotos G. Differential inhibition of group IVA and group VIA phospholipases A2 by 2-oxoamides. J Med Chem 2006; 49:2821-8. [PMID: 16640343 PMCID: PMC2544624 DOI: 10.1021/jm050993h] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Inhibitors of the Group IVA phospholipase A(2) (GIVA cPLA(2)) and GVIA iPLA(2) are useful tools for defining the roles of these enzymes in cellular signaling and inflammation. We have developed inhibitors of GVIA iPLA(2) building upon the 2-oxoamide backbone that are uncharged, containing ester groups. Although the most potent inhibitors of GVIA iPLA(2) also inhibited GIVA cPLA(2), there were three 2-oxoamide compounds that selectively and weakly inhibited GVIA iPLA(2). We further show that several potent 2-oxoamide inhibitors of GIVA cPLA(2) containing free carboxylic groups (Kokotos et al. J. Med. Chem. 2002, 45, 2891-2893) do not inhibit GVIA iPLA(2) and are, therefore, selective GIVA cPLA(2) inhibitors.
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Affiliation(s)
- Daren Stephens
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093-0601
| | - Efrosini Barbayianni
- Laboratory of Organic Chemistry, Department of Chemistry, University of Athens, Panepistimiopolis, Athens 15771, Greece
| | | | - Anna Peristeraki
- Chemical Laboratories, Agricultural University of Athens, Athens 11855, Greece
| | - David A. Six
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093-0601
| | - Jennifer Cooper
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093-0601
| | - Richard Harkewicz
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093-0601
| | - Raymond A. Deems
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093-0601
| | - Edward A. Dennis
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093-0601
- To whom correspondence should be addressed. For E.A.D. e-mail: ; phone: 858-534-3055; fax: 858-534-7390. For G.K. ; phone: 30210 7274462; fax: 30210 7274761
| | - George Kokotos
- Laboratory of Organic Chemistry, Department of Chemistry, University of Athens, Panepistimiopolis, Athens 15771, Greece
- To whom correspondence should be addressed. For E.A.D. e-mail: ; phone: 858-534-3055; fax: 858-534-7390. For G.K. ; phone: 30210 7274462; fax: 30210 7274761
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Ghosh M, Loper R, Gelb MH, Leslie CC. Identification of the Expressed Form of Human Cytosolic Phospholipase A2β (cPLA2β). J Biol Chem 2006; 281:16615-24. [PMID: 16617059 DOI: 10.1074/jbc.m601770200] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In this study, we identify the principal splice variant of human cytosolic phospholipase A(2)beta (cPLA(2)beta) (also known as Group IVB cPLA(2)) present in cells. In human lung, spleen, and ovary and in a lung epithelial cell line (BEAS-2B), cPLA(2)beta is expressed as a 100-kDa protein, not the 114-kDa form originally predicted. Using RNA interference, the 100-kDa protein in BEAS-2B cells was confirmed to be cPLA(2)beta. BEAS-2B cells contain three different RNA splice variants of cPLA(2)beta (beta1, beta2, and beta3). cPLA(2)beta1 is identical to the previously cloned cPLA(2)beta, predicted to encode a 114-kDa protein. However, cPLA(2)beta2 and cPLA(2)beta3 splice variants are smaller and contain internal deletions in the catalytic domain. The 100-kDa cPLA(2)beta in BEAS-2B cells is the translated product of cPLA(2)beta3. cPLA(2)beta3 exhibits calcium-dependent PLA(2) activity against palmitoyl-arachidonyl-phosphatidylethanolamine and low level lysophospholipase activity but no activity against phosphatidylcholine. Unlike Group IVA cPLA(2)alpha, cPLA(2)beta3 is constitutively bound to membrane in unstimulated cells, localizing to mitochondria and early endosomes. cPLA(2)beta3 is widely expressed in tissues, suggesting that it has a generalized function at these unique sites.
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Affiliation(s)
- Moumita Ghosh
- Program in Cell Biology, Department of Pediatrics, National Jewish Medical and Research Center, 1400 Jackson Street, Denver, CO 80206, USA
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Merkel O, Oskolkova O, Raab F, El-Toukhy R, Paltauf F. Regulation of activity in vitro and in vivo of three phospholipases B from Saccharomyces cerevisiae. Biochem J 2005; 387:489-96. [PMID: 15588231 PMCID: PMC1134978 DOI: 10.1042/bj20041272] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The genome of the yeast, Saccharomyces cerevisiae, contains three highly similar genes coding for phospholipases B/lysophospholipases. These enzymes behave differently with respect to substrate preferences in vitro and relative contributions to phospholipid catabolism in vivo [Merkel, Fido, Mayr, Pruger, Raab, Zandonella, Kohlwein and Paltauf (1999) J. Biol. Chem. 274, 28121-28127]. It is shown in the present study that, in vitro, pH markedly affects the substrate preference of Plb1p and Plb2p, but not of Plb3p. At the pH optimum of 2.5-3.5, the order of substrate preference of Plb1p and Plb2p is PtdSer (phosphatidylserine)>PtdIns>PtdCho (phosphatidylcholine>PtdEtn (phosphatidylethanolamine). At pH values of 5 and above, the substrate preferences change to PtdCho=PtdEtn for Plb1p and PtdSer=PtdEtn for Plb2p. Accordingly, with cultured cells the ratio of PtdIns/PtdCho breakdown, as reflected in the ratio of GroPIns (glycerophosphoinositol)/GroPCho (glycerophosphocholine) released into the culture medium, is inversely related to the pH of the growth medium. This effect is ascribed to the pH response of Plb1p, because Plb2p does not contribute to the degradation of PtdIns and PtdCho in vivo. Bivalent and tervalent cations activate phospholipases B at pH 5.5, but are inhibitory at pH 2.5. Al3+ at a concentration of 20 mM increases Plb1p activity in vitro by 8-fold and leads to a 9-fold increase in GroPCho release by whole cells. In vivo, cycloheximide strongly inhibits the breakdown of PtdIns, and to a lesser extent PtdCho. However, Al3+-stimulated GroPCho release is almost completely inhibited by cycloheximide. Deletion of PLB3 leads to increased sensitivity to toxic Al3+. Addition of SDS or melittin to cultured cells leads to a significant increase in phospholipid degradation, which is insensitive to inhibition by cycloheximide. Deletion mutants defective in the PLB1 gene are significantly more resistant to SDS than are wild-type cells.
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Affiliation(s)
- Olaf Merkel
- Institut für Biochemie, Technische Universität Graz, Petersgasse 12, 8010 Graz, Austria
- To whom correspondence should be sent, at present address: Institute of Molecular Biosciences, Universität Graz, Schubertstrasse 1, 8010 Graz, Austria (email or )
| | - Olga V. Oskolkova
- Institut für Biochemie, Technische Universität Graz, Petersgasse 12, 8010 Graz, Austria
| | - Florian Raab
- Institut für Biochemie, Technische Universität Graz, Petersgasse 12, 8010 Graz, Austria
| | - Rosemarie El-Toukhy
- Institut für Biochemie, Technische Universität Graz, Petersgasse 12, 8010 Graz, Austria
| | - Fritz Paltauf
- Institut für Biochemie, Technische Universität Graz, Petersgasse 12, 8010 Graz, Austria
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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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40
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Ohto T, Uozumi N, Hirabayashi T, Shimizu T. Identification of novel cytosolic phospholipase A(2)s, murine cPLA(2){delta}, {epsilon}, and {zeta}, which form a gene cluster with cPLA(2){beta}. J Biol Chem 2005; 280:24576-83. [PMID: 15866882 DOI: 10.1074/jbc.m413711200] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phospholipase A(2) hydrolyzes the sn-2 ester bond of glycerophospholipids that produce free fatty acids and lysophospholipids. Cytosolic phospholipase A(2)s (cPLA(2), group IV) are a subgroup of enzymes that act on the intracellular phospholipid membrane. The best investigated cPLA(2)alpha (group IVA) is a key enzyme for lipid mediator production in vivo. Here we report cloning and characterization of novel murine cPLA(2)s: cPLA(2)delta (group IVD), cPLA(2)epsilon (group IVE), and cPLA(2)zeta (group IVF), that form a gene cluster with cPLA(2)beta (group IVB). The deduced amino acid sequences of cPLA(2)delta, epsilon, and zeta demonstrated a conserved domain structure of cPLA(2), i.e. one C2 domain and one lipase domain. The potential catalytic dyad, Ser and Asp, was conserved for these newly cloned cPLA(2)s along with relatively high conservation for the surrounding residues. Transcripts of murine cPLA(2)delta, epsilon, and zeta appeared to be enriched in certain organs rather than ubiquitous distribution. Major Northern signals for cPLA(2)delta were detected in placenta, cPLA(2)epsilon in thyroid, heart, and skeletal muscle, and cPLA(2)zeta in thyroid. Recombinant proteins expressed in human embryonic kidney 293 cells demonstrated molecular sizes of about 100 kDa by Western blotting and exhibited Ca(2+)-dependent PLA(2) activities on 1-palmitoyl-2-[(14)C]arachidonoyl-phosphatidylcholine substrate. In contrast to cPLA(2)alpha, cPLA(2)zeta preferred phosphatidylethanolamine to phosphatidylcholine. Intracellular localization was visualized by green fluorescent-tagged proteins. Each molecule showed specific localization, and cPLA(2)delta translocated from the cytosol to the perinuclear region by calcium-ionophore stimulation. We thus discovered these functional novel cPLA(2) genes, which cluster on murine chromosome 2E5.
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MESH Headings
- Amino Acid Sequence
- Animals
- Aspartic Acid/metabolism
- Blotting, Northern
- Blotting, Western
- Calcium/metabolism
- Catalysis
- Catalytic Domain
- Cell Line
- Cloning, Molecular
- Cytosol/enzymology
- Electrophoresis, Polyacrylamide Gel
- Exons
- Expressed Sequence Tags
- Genetic Vectors
- Green Fluorescent Proteins/metabolism
- Humans
- Male
- Mice
- Mice, Inbred C57BL
- Microscopy, Confocal
- Models, Genetic
- Molecular Sequence Data
- Multigene Family
- Open Reading Frames
- Peptides/chemistry
- Phospholipases A/chemistry
- Phospholipases A/genetics
- Phylogeny
- Protein Isoforms
- Protein Structure, Tertiary
- Protein Transport
- RNA/chemistry
- RNA, Messenger/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
- Sequence Analysis, DNA
- Sequence Homology, Amino Acid
- Serine/chemistry
- Software
- Substrate Specificity
- Tissue Distribution
- Transfection
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Affiliation(s)
- Takayo Ohto
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan
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Becker M, Bunikis J, Lade BD, Dunn JJ, Barbour AG, Lawson CL. Structural investigation of Borrelia burgdorferi OspB, a bactericidal Fab target. J Biol Chem 2005; 280:17363-70. [PMID: 15713683 DOI: 10.1074/jbc.m412842200] [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] [Indexed: 11/06/2022] Open
Abstract
Certain antibody Fab fragments directed against the C terminus of outer surface protein B (OspB), a major lipoprotein of the Lyme disease spirochete, Borrelia burgdorferi, have the unusual property of being bactericidal even in the absence of complement. We report here x-ray crystal structures of a C-terminal fragment of B. burgdorferi OspB, which spans residues 152-296, alone at 2.0-A resolution, and in a complex with the bactericidal Fab H6831 at 2.6-A resolution. The H6831 epitope is topologically analogous to the LA-2 epitope of OspA and is centered around OspB Lys-253, a residue essential for H6831 recognition. A beta-sheet present in the free OspB fragment is either disordered or removed by proteolysis in the H6831-bound complex. Other conformational changes between free and H6831-bound structures are minor and appear to be related to this loss. In both crystal structures, OspB C-terminal fragments form artificial dimers connected by intermolecular beta-sheets. OspB structure, stability, and possible mechanisms of killing by H6831 and other bactericidal Fabs are discussed in light of the structural data.
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Affiliation(s)
- Michael Becker
- Biology Department, Brookhaven National Laboratory, Upton, New York 11973, USA.
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Pankhaniya RR, Tamura M, Allmond LR, Moriyama K, Ajayi T, Wiener-Kronish JP, Sawa T. Pseudomonas aeruginosa causes acute lung injury via the catalytic activity of the patatin-like phospholipase domain of ExoU. Crit Care Med 2005; 32:2293-9. [PMID: 15640644 DOI: 10.1097/01.ccm.0000145588.79063.07] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE Acute lung injury in Pseudomonas aeruginosa pneumonia depends primarily on ExoU toxin being delivered directly into the eukaryotic cell cytosol through the type III secretion system. The amino-acid sequence of ExoU has a potato patatin-like phospholipase domain, similar to the sequence of mammalian Ca-independent phospholipase A2. We examined whether the acute lung injury caused by cytotoxic P. aeruginosa was dependent on the patatin-like phospholipase domain of ExoU. DESIGN Laboratory investigation using an established mouse model for P. aeruginosa pneumonia with quantitative measurements of acute lung injury and mortality. SETTING University experimental research laboratory. SUBJECTS Balb/c mice. INTERVENTIONS First, a site-directional mutation was introduced in the predicted catalytically active site of the patatin-like phospholipase domain of recombinant ExoU protein. The effect of the mutation on the catalytic activity of ExoU was tested by the in vitro lysophospholipase A assay. Second, the same site-directional mutation was introduced into the exoU gene of P. aeruginosa PA103. Mice were intratracheally infected with either a wild-type P. aeruginosa strain PA103 or an isogenic mutant containing the mutation in exoU. Acute epithelial lung injury, lung edema, bacteremia, and mortality were evaluated quantitatively. MEASUREMENTS AND MAIN RESULTS Recombinant ExoU had lysophospholipase A activity. Site-directional mutations in the predicted catalytic site of ExoU caused a loss of the lysophospholipase A activity. Whereas the airspace instillation of PA103 caused acute lung injury and death of the infected mice, the airspace instillation of isogenic mutants secreting catalytically inactive ExoU were noncytotoxic and did not cause acute lung injury or death of the infected mice. CONCLUSION Virulent P. aeruginosa causes acute lung injury and death by the cytotoxic activity derived from the patatin-like phospholipase domain of ExoU.
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Affiliation(s)
- Ravi R Pankhaniya
- Department of Anesthesia and Perioperative Care, School of Medicine, University of California San Francisco, San Francisco, CA 94143-0542, USA
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Abstract
The combination of a large genome encoding metabolic versatility and conserved secreted virulence determinants makes Pseudomonas aeruginosa a model pathogen that can be used to study host-parasite interactions in many eukaryotic hosts. One of the virulence regulons that likely plays a role in the ability of P. aeruginosa to avoid innate immune clearance in mammals is a type III secretion system (TTSS). Upon cellular contact, the P. aeruginosa TTSS is capable of delivering a combination of at least four different effector proteins, exoenzyme S (ExoS), ExoT, ExoU, and ExoY. Two of the four translocated proteins, ExoS and ExoU, are cytotoxic to cells during infection and transfection. The mechanism of cytotoxicity of ExoS is unclear. ExoU, however, has recently been characterized as a member of the phospholipase A family of enzymes, possessing at least phospholipase A2 activity. Similar to ExoS, ExoT and ExoY, ExoU requires either a eukaryotic-specific modification or cofactor for its activity in vitro. The biologic effects of minimal expression of ExoU in yeast can be visualized by membrane damage to different organelles and fragmentation of the vacuole. In mammalian cells, the direct injection of ExoU causes irreversible damage to cellular membranes and rapid necrotic death. ExoU likely represents a unique enzyme and is the first identified phopholipase virulence factor that is translocated into the cytosol by TTSS.
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Affiliation(s)
- Hiromi Sato
- Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, Wisconsin 53226, USA
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45
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Abstract
ExoU, a potent patatin-like phospholipase, causes rapid cell death following its injection into host cells by the Pseudomonas aeruginosa type III secretion system. To better define regions of ExoU required for cytotoxicity, transposon-based linker insertion mutagenesis followed by site-directed mutagenesis of individual residues was employed by using a Saccharomyces cerevisiae model system. Random insertion of five amino acids identified multiple regions within ExoU that are required for cell killing. Five regions were chosen for further characterization: three corresponded to the oxyanion hole, hydrolase motif, and catalytic aspartate motif of the patatin-like domain within the N-terminal half of ExoU; one corresponded to an uncharacterized part of the patatin-like domain; and one corresponded to a region near the C terminus. Specific individual amino acid substitutions in each of the four N-terminal regions prevented killing of yeast and significantly reduced phospholipase activity. Whereas five amino acid insertions in the fifth region near the C terminus markedly reduced cytotoxicity and phospholipase activity, substitution of individual amino acids did not abolish either activity. To determine whether each of the five identified regions of ExoU was also essential for cytotoxicity in human cells, representative mutant forms of ExoU fused to green fluorescent protein were expressed in HeLa cells. These variants of ExoU were readily visualized and caused minimal cytotoxicity to HeLa cells, while wild-type ExoU fused to green fluorescent protein induced significant cell lysis and no detectable fluorescence. Thus, a minimum of five regions, including one which is well removed from the patatin-like domain, are required for the cytotoxicity and phospholipase activity of ExoU.
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Affiliation(s)
- Shira D P Rabin
- Department of Microbiology/Immunology, Northwestern University, 303 East Chicago Ave., Searle 6-495, Chicago, IL 60611, USA
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46
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Shen DK, Noodeh AD, Kazemi A, Grillot R, Robson G, Brugère JF. Characterisation and expression of phospholipases B from the opportunistic fungusAspergillus fumigatus. FEMS Microbiol Lett 2004; 239:87-93. [PMID: 15451105 DOI: 10.1016/j.femsle.2004.08.019] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2004] [Revised: 08/17/2004] [Accepted: 08/18/2004] [Indexed: 11/21/2022] Open
Abstract
The phospholipase B family (PLB) are enzymes sharing phospholipase (PL), lysophospholipase (LPL) and lysophospholipase-transacylase (LPTA) activities. They have been shown to be important virulence factors in several human fungal pathogens including Candida albicans and Cryptococcus neoformans. Aspergillus fumigatus, a human opportunistic fungal pathogen leading to a high rate of mortality in immunosuppressed patients is known to possess an extracellular phospholipase B activity. In this paper, we report the molecular characterisation of three PLB genes from A. fumigatus (afplb) using degenerate primers in PCR amplification and data from the A. fumigatus genome project. They are expressed at 37 degrees C, and two of them (afplb1 and afplb3) are induced by lecithin. They encode proteins of 633, 588 and 630 amino acids, respectively, presenting together a T-Coffee score of 81. They also possess the amino acid triad responsible for enzymatic activity in the mammalian cytosolic PLA2 and other fungal PLBs. AfPLB1 and afPLB3 are secreted with a cleaved signal peptide. The complete cDNA sequences were obtained by RACE-PCR for the two secreted afPLBs and probably account for the extracellular phospholipase activity previously reported in the culture media of A. fumigatus.
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Affiliation(s)
- Da-Kang Shen
- Laboratoire Interactions Cellulaires Parasite-Hôte--ICPH, Facultéde Médecine et Pharmacie, Université Joseph Fourier, F-38706 La Tronche, France
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Kokotos G, Six DA, Loukas V, Smith T, Constantinou-Kokotou V, Hadjipavlou-Litina D, Kotsovolou S, Chiou A, Beltzner CC, Dennis EA. Inhibition of Group IVA Cytosolic Phospholipase A2by Novel 2-Oxoamides in Vitro, in Cells, and in Vivo. J Med Chem 2004; 47:3615-28. [PMID: 15214789 DOI: 10.1021/jm030485c] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The Group IVA cytosolic phospholipase A(2) (GIVA PLA(2)) is a particularly attractive target for drug development because it is the rate-limiting provider of proinflammatory mediators. We previously reported the discovery of novel 2-oxoamides that inhibit GIVA PLA(2) [Kokotos, G.; et al. J. Med. Chem. 2002, 45, 2891-2893]. In the present work, we have further explored this class of inhibitors and found that the 2-oxoamide functionality is more potent when it contains a long 2-oxoacyl residue and a free carboxy group. Long-chain 2-oxoamides based on gamma-aminobutyric acid and gamma-norleucine are potent inhibitors of GIVA PLA(2). Such inhibitors act through a fast and reversible mode of inhibition in vitro, are able to block the production of arachidonic acid and prostaglandin E(2) in cells, and demonstrate potent in vivo anti-inflammatory and analgesic activity.
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Affiliation(s)
- George Kokotos
- Laboratory of Organic Chemistry, Department of Chemistry, University of Athens, Panepistimiopolis, Athens 15771, Greece.
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48
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Phillips RM, Six DA, Dennis EA, Ghosh P. In vivo phospholipase activity of the Pseudomonas aeruginosa cytotoxin ExoU and protection of mammalian cells with phospholipase A2 inhibitors. J Biol Chem 2003; 278:41326-32. [PMID: 12915403 DOI: 10.1074/jbc.m302472200] [Citation(s) in RCA: 143] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A number of clinical isolates of Pseudomonas aeruginosa are cytotoxic to mammalian cells due to the action of the 74-kDa protein ExoU, which is secreted into host cells by the type III secretion system and whose function is unknown. Here we report that the swift and profound cytotoxicity induced by purified ExoU or by an ExoU-expressing strain of P. aeruginosa is blocked by various inhibitors of cytosolic (cPLA2) and Ca2+ -independent (iPLA2) phospholipase A2 enzymes. In contrast, no cytoprotection is offered by inhibitors of secreted phospholipase A2 enzymes or by a number of inhibitors of signal transduction pathways. This suggests that phospholipase A2 inhibitors may represent a novel mode of treatment for acute P. aeruginosa infections. We find that 300-600 molecules of ExoU/cell are required to achieve half-maximal cell killing and that ExoU localizes to the host cell plasma membrane in punctate fashion. We also show that ExoU interacts in vitro with an inhibitor of cPLA2 and iPLA2 enzymes and contains a putative serine-aspartate catalytic dyad homologous to those found in cPLA2 and iPLA2 enzymes. Mutation of either the serine or the aspartate renders ExoU non-cytotoxic. Although no phospholipase or esterase activity is detected in vitro, significant phospholipase activity is detected in vivo, suggesting that ExoU requires one or more host cell factors for activation as a membrane-lytic and cytotoxic phospholipase.
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Affiliation(s)
- Rebecca M Phillips
- Department of Chemistry and Biochemistry, University of California at San Diego, La Jolla, California 92093-0314, USA
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49
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Abstract
Several new PLA(2)s have been identified based on their nucleotide gene sequences. They were classified mainly into three groups: cytosolic PLA(2) (cPLA(2)), secretary PLA(2) (sPLA(2)), and intracellular PLA(2) (iPLA(2)). They differ from each other in terms of substrate specificity, Ca(2+) requirement and lipid modification. The questions that still remain to be addressed are the subcellular localization and differential regulation of the isoforms in various cell types and under different physiological conditions. It is required to identify the downstream events that occur upon PLA(2) activation, particularly target protein or metabolic pathway for liberated arachidonic acid or other fatty acids. Understanding the same will greatly help in the development of potent and specific pharmacological modulators that can be used for basic research and clinical applications. The information of the human and other genomes of PLA(2)s, combined with the use of proteomics and genetically manipulated mouse models of different diseases, will illuminate us about the specific and potentially overlapping roles of individual phospholipases as mediators of physiological and pathological processes. Hopefully, such understanding will enable the development of specific agents aimed at decreasing the potential contribution of individual secretary phospholipases to vascular diseases. The signaling cascades involved in the activation of cPLA(2) by mitogen activated protein kinases (MAPKs) is now evident. It has been demonstrated that p44 MAPK phosphorylates cPLA(2) and increases its activity in cells and tissues. The phosphorylation of cPLA(2) at ser505 occurs before the increase in intracellular Ca(2+) that facilitate the binding of the lipid binding domain of cPLA(2) to phospholipids, promoting its translocation to cellular membranes and AA release. Recently, a negative feed back loop for cPLA(2) activation by MAPK has been proposed. If PLA(2) activation in a given model depends on PKC, PKA, cAMP, or MAPK then inhibition of these phosphorylating enzymes may alter activities of PLA(2) isoforms during cellular injury. Understanding the signaling pathways involved in the activation/deactivation of PLA(2) during cellular injury will point to key events that can be used to prevent the cellular injury. Furthermore, to date, there is limited information available regarding the regulation of iPLA(2) or sPLA(2) by these pathways.
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Affiliation(s)
- Sajal Chakraborti
- Department of Biochemistry and Biophysics, University of Kalyani, Kalyani 741235, West Bengal, India.
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50
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Sato H, Frank DW, Hillard CJ, Feix JB, Pankhaniya RR, Moriyama K, Finck-Barbançon V, Buchaklian A, Lei M, Long RM, Wiener-Kronish J, Sawa T. The mechanism of action of the Pseudomonas aeruginosa-encoded type III cytotoxin, ExoU. EMBO J 2003; 22:2959-69. [PMID: 12805211 PMCID: PMC162142 DOI: 10.1093/emboj/cdg290] [Citation(s) in RCA: 258] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Pseudomonas aeruginosa delivers the toxin ExoU to eukaryotic cells via a type III secretion system. Intoxication with ExoU is associated with lung injury, bacterial dissemination and sepsis in animal model and human infections. To search for ExoU targets in a genetically tractable system, we used controlled expression of the toxin in Saccharomyces cerevisiae. ExoU was cytotoxic for yeast and caused a vacuolar fragmentation phenotype. Inhibitors of human calcium-independent (iPLA(2)) and cytosolic phospholipase A(2) (cPLA(2)) lipase activity reduce the cytotoxicity of ExoU. The catalytic domains of patatin, iPLA(2) and cPLA(2) align or are similar to ExoU sequences. Site-specific mutagenesis of predicted catalytic residues (ExoUS142A or ExoUD344A) eliminated toxicity. ExoU expression in yeast resulted in an accumulation of free palmitic acid, changes in the phospholipid profiles and reduction of radiolabeled neutral lipids. ExoUS142A and ExoUD344A expressed in yeast failed to release palmitic acid. Recombinant ExoU demonstrated lipase activity in vitro, but only in the presence of a yeast extract. From these data we conclude that ExoU is a lipase that requires activation or modification by eukaryotic factors.
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Affiliation(s)
- Hiromi Sato
- Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
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