1
|
Murawska GM, Armando A, Dennis EA. Lipidomics of Phospholipase A 2 Reveals Exquisite Specificity in Macrophages. J Lipid Res 2024:100571. [PMID: 38795860 DOI: 10.1016/j.jlr.2024.100571] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2024] [Revised: 05/17/2024] [Accepted: 05/19/2024] [Indexed: 05/28/2024] Open
Abstract
Phospholipase A2 (PLA2) constitutes a superfamily of enzymes that hydrolyze phospholipids at their sn-2 fatty acyl position. Our laboratory has demonstrated that PLA2 enzymes regulate membrane remodeling and cell signaling by their specificity toward their phospholipid substrates at the molecular level. Recent in vitro studies show that each type of PLA2, including GIVA cytosolic PLA2 (cPLA2), GV secreted PLA2 (sPLA2), GVIA calcium independent PLA2 (iPLA2) and GVIIA lipoprotein-associated PLA2 (LpPLA2), also known as platelet-activating factor acetyl hydrolase (PAFAH), can discriminate exquisitely between fatty acids at the sn-2 position. Thus, these enzymes regulate the production of diverse polyunsaturated fatty acid (PUFA) precursors of inflammatory metabolites. We now determined PLA2 specificity in macrophage cells grown in cell culture, where the amounts and localization of the phospholipid substrates play a role in which specific phospholipids are hydrolyzed by each enzyme type. We employ PLA2 stereospecific inhibitors in tandem with a novel UPLC-MS/MS based lipidomics platform to quantify more than a thousand unique phospholipid molecular species demonstrating cPLA2, sPLA2, and iPLA2 activity and specificity toward the phospholipids in living cells. The observed specificity follows the in vitro capability of the enzymes and can reflect the enrichment of certain phospholipid species in specific membrane locations where particular PLA2's associate. For assaying, we target 20:4-PI for cPLA2, 22:6-PG for sPLA2 and 18:2-PC for iPLA2. These new results provide great insight into the physiological role of PLA2 enzymes in cell membrane remodeling and could shed light on how PLA2 enzymes underpin inflammation and other lipid-related diseases.
Collapse
Affiliation(s)
- Gosia M Murawska
- Department of Chemistry and Biochemistry and Department of Pharmacology, School of Medicine, University of California at San Diego, La Jolla, CA 92093, USA
| | - Aaron Armando
- Department of Chemistry and Biochemistry and Department of Pharmacology, School of Medicine, University of California at San Diego, La Jolla, CA 92093, USA
| | - Edward A Dennis
- Department of Chemistry and Biochemistry and Department of Pharmacology, School of Medicine, University of California at San Diego, La Jolla, CA 92093, USA.
| |
Collapse
|
2
|
Fernández-García M, Ares-Arroyo M, Wedel E, Montero N, Barbas C, Rey-Stolle MF, González-Zorn B, García A. Multiplatform Metabolomics Characterization Reveals Novel Metabolites and Phospholipid Compositional Rules of Haemophilus influenzae Rd KW20. Int J Mol Sci 2023; 24:11150. [PMID: 37446331 DOI: 10.3390/ijms241311150] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Revised: 06/30/2023] [Accepted: 07/04/2023] [Indexed: 07/15/2023] Open
Abstract
Haemophilus influenzae is a gram-negative bacterium of relevant clinical interest. H. influenzae Rd KW20 was the first organism to be sequenced and for which a genome-scale metabolic model (GEM) was developed. However, current H. influenzae GEMs are unable to capture several aspects of metabolome nature related to metabolite pools. To directly and comprehensively characterize the endometabolome of H. influenzae Rd KW20, we performed a multiplatform MS-based metabolomics approach combining LC-MS, GC-MS and CE-MS. We obtained direct evidence of 15-20% of the endometabolome present in current H. influenzae GEMs and showed that polar metabolite pools are interconnected through correlating metabolite islands. Notably, we obtained high-quality evidence of 18 metabolites not previously included in H. influenzae GEMs, including the antimicrobial metabolite cyclo(Leu-Pro). Additionally, we comprehensively characterized and evaluated the quantitative composition of the phospholipidome of H. influenzae, revealing that the fatty acyl chain composition is largely independent of the lipid class, as well as that the probability distribution of phospholipids is mostly related to the conditional probability distribution of individual acyl chains. This finding enabled us to provide a rationale for the observed phospholipid profiles and estimate the abundance of low-level species, permitting the expansion of the phospholipidome characterization through predictive probabilistic modelling.
Collapse
Affiliation(s)
- Miguel Fernández-García
- Centro de Metabolómica y Bioanálisis (CEMBIO), Facultad de Farmacia, Universidad San Pablo-CEU, CEU Universities, Urbanización Montepríncipe, 28660 Boadilla del Monte, Spain
- Departamento de Ciencias Médicas Básicas, Facultad de Medicina, Universidad San Pablo-CEU, CEU Universities, Urbanización Montepríncipe, 28660 Boadilla del Monte, Spain
| | - Manuel Ares-Arroyo
- Antimicrobial Resistance Unit (ARU), Departamento de Sanidad Animal and Centro de Vigilancia Sanitaria Veterinaria (VISAVET), Complutense University of Madrid, 28040 Madrid, Spain
| | - Emilia Wedel
- Antimicrobial Resistance Unit (ARU), Departamento de Sanidad Animal and Centro de Vigilancia Sanitaria Veterinaria (VISAVET), Complutense University of Madrid, 28040 Madrid, Spain
| | - Natalia Montero
- Antimicrobial Resistance Unit (ARU), Departamento de Sanidad Animal and Centro de Vigilancia Sanitaria Veterinaria (VISAVET), Complutense University of Madrid, 28040 Madrid, Spain
| | - Coral Barbas
- Centro de Metabolómica y Bioanálisis (CEMBIO), Facultad de Farmacia, Universidad San Pablo-CEU, CEU Universities, Urbanización Montepríncipe, 28660 Boadilla del Monte, Spain
| | - Mª Fernanda Rey-Stolle
- Centro de Metabolómica y Bioanálisis (CEMBIO), Facultad de Farmacia, Universidad San Pablo-CEU, CEU Universities, Urbanización Montepríncipe, 28660 Boadilla del Monte, Spain
| | - Bruno González-Zorn
- Antimicrobial Resistance Unit (ARU), Departamento de Sanidad Animal and Centro de Vigilancia Sanitaria Veterinaria (VISAVET), Complutense University of Madrid, 28040 Madrid, Spain
| | - Antonia García
- Centro de Metabolómica y Bioanálisis (CEMBIO), Facultad de Farmacia, Universidad San Pablo-CEU, CEU Universities, Urbanización Montepríncipe, 28660 Boadilla del Monte, Spain
| |
Collapse
|
3
|
Manson A, Winter T, Aukema HM. Phospholipase A 2 enzymes differently impact PUFA release and oxylipin formation ex vivo in rat hearts. Prostaglandins Leukot Essent Fatty Acids 2023; 191:102555. [PMID: 36878084 DOI: 10.1016/j.plefa.2023.102555] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2022] [Revised: 02/16/2023] [Accepted: 02/23/2023] [Indexed: 03/04/2023]
Abstract
Phospholipase A2 (PLA2) enzymes cleave cell membrane phospholipids and release polyunsaturated fatty acids (PUFA), which can be converted into oxylipins. However, little is known about PLA2 preference for PUFA, and even less is known about how this further impacts oxylipin formation. Therefore, we investigated the role of different PLA2 groups in PUFA release and oxylipin formation in rat hearts. Sprague-Dawley rat heart homogenates were incubated without or with varespladib (VAR), methyl arachidonyl fluorophosphonate (MAFP) or EDTA. Free PUFA and oxylipins were determined by HPLC-MS/MS, and isoform expressions by RT-qPCR. Inhibition of sPLA2 IIA and/or V by VAR reduced the release of ARA and DHA, but only DHA oxylipins were inhibited. MAFP reduced the release of ARA, DHA, ALA, and EPA, and the formation of ARA, LA, DGLA, DHA, ALA, and EPA oxylipins. Interestingly, cyclooxygenase and 12-lipoxygenase oxylipins were not inhibited. mRNA expression levels of sPLA2 and iPLA2 isoforms were highest whereas levels of cPLA2 were low, consistent with activity. In conclusion, sPLA2 enzymes lead to the formation of DHA oxylipins, while iPLA2 is likely responsible for the formation of most other oxylipins in healthy rat hearts. Oxylipin formation cannot be implied from PUFA release, thus, both should be evaluated in PLA2 activity studies.
Collapse
Affiliation(s)
- Anne Manson
- Food and Human Nutritional Sciences, University of Manitoba, Winnipeg MB, Canada; Canadian Centre for Agri-Food Research in Health and Medicine (CCARM), Winnipeg MB, Canada
| | - Tanja Winter
- Food and Human Nutritional Sciences, University of Manitoba, Winnipeg MB, Canada; Canadian Centre for Agri-Food Research in Health and Medicine (CCARM), Winnipeg MB, Canada
| | - Harold M Aukema
- Food and Human Nutritional Sciences, University of Manitoba, Winnipeg MB, Canada; Canadian Centre for Agri-Food Research in Health and Medicine (CCARM), Winnipeg MB, Canada.
| |
Collapse
|
4
|
Mouchlis VD, Dennis EA. Membrane Association Allosterically Regulates Phospholipase A 2 Enzymes and Their Specificity. Acc Chem Res 2022; 55:3303-3311. [PMID: 36315840 PMCID: PMC9730854 DOI: 10.1021/acs.accounts.2c00497] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Indexed: 01/19/2023]
Abstract
Water-soluble proteins as well as membrane-bound proteins associate with membrane surfaces and bind specific lipid molecules in specific sites on the protein. Membrane surfaces include the traditional bilayer membranes of cells and subcellular organelles formed by phospholipids. Monolayer membranes include the outer monolayer phospholipid surface of intracellular lipid droplets of triglycerides and various lipoproteins including HDL, LDL, VLDL, and chylomicrons. These lipoproteins circulate in our blood and lymph systems and contain triglycerides, cholesterol, cholesterol esters, and proteins in their interior, and these are sometimes interspersed on their surfaces. Similar lipid-water interfaces also occur in mixed micelles of phospholipids and bile acids in our digestive system, which may also include internalized triglycerides and cholesterol esters. Diacyl phospholipids constitute the defining molecules of biological membranes. Phospholipase A1 (PLA1) hydrolyzes phospholipid acyl chains at the sn-1 position of membrane phospholipids, phospholipase A2 (PLA2) hydrolyzes acyl chains at the sn-2 position, phospholipase C (PLC) hydrolyzes the glycerol-phosphodiester bond, and phospholipase D (PLD) hydrolyzes the polar group-phosphodiester bond. Of the phospholipases, the PLA2s have been the most well studied at the mechanistic level. The PLA2 superfamily consists of 16 groups and numerous subgroups, and each is generally described as one of 6 types. The most well studied of the PLA2s include extensive genetic and mutational studies, complete lipidomics specificity characterization, and crystallographic structures. This Account will focus principally on results from deuterium exchange mass spectrometric (DXMS) studies of PLA2 interactions with membranes and extensive molecular dynamics (MD) simulations of their interactions with membranes and specific phospholipids bound in their catalytic and allosteric sites. These enzymes either are membrane-bound or are water-soluble and associate with membranes before extracting their phospholipid substrate molecule into their active site to carry out their enzymatic hydrolytic reaction. We present evidence that when a PLA2 associates with a membrane, the membrane association can result in a conformational change in the enzyme whereby the membrane association with an allosteric site on the enzyme stabilizes the enzyme in an active conformation on the membrane. We sometimes refer to this transition from a "closed" conformation in aqueous solution to an "open" conformation when associated with a membrane. The enzyme can then extract a single phospholipid substrate into its active site, and catalysis occurs. We have also employed DXMS and MD simulations to characterize how PLA2s interact with specific inhibitors that could lead to potential therapeutics. The PLA2s constitute a paradigm for how membranes interact allosterically with proteins, causing conformational changes and activation of the proteins to enable them to extract and bind a specific phospholipid from a membrane for catalysis, which is probably generalizable to intracellular and extracellular transport and phospholipid exchange processes as well as other specific biological functions. We will focus on the four main types of PLA2, namely, the secreted (sPLA2), cytosolic (cPLA2), calcium-independent (iPLA2), and lipoprotein-associated PLA2 (Lp-PLA2) also known as platelet-activating factor acetyl hydrolase (PAF-AH). Studies on a well-studied specific example of each of the four major types of the PLA2 superfamily demonstrate clearly that protein subsites can show precise specificity for one of the phospholipid hydrophobic acyl chains, often the one at the sn-2 position, including exquisite sensitivity to the number and position of double bonds.
Collapse
Affiliation(s)
- Varnavas D. Mouchlis
- Department of Chemistry and Biochemistry
and Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, California 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, California 92093-0601 United States
| |
Collapse
|
5
|
Chen C, Lou MM, Sun YM, Luo F, Liu FT, Luo SS, Wang WY, Wang J. Serum metabolomic characterization of PLA2G6-associated dystonia-parkinsonism: A case-control biomarker study. Front Neurosci 2022; 16:879548. [PMID: 36033628 PMCID: PMC9406281 DOI: 10.3389/fnins.2022.879548] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2022] [Accepted: 07/15/2022] [Indexed: 01/09/2023] Open
Abstract
Introduction Phospholipase A2 Group VI (PLA2G6), encoding calcium-independent phospholipase A2, has been isolated as the gene responsible for an autosomal recessive form of early-onset Parkinson's disease (namely, PARK14). Compared to idiopathic Parkinson's disease (iPD), PARK14 has several atypical clinical features. PARK14 has an earlier age at onset and is more likely to develop levodopa-induced dyskinesia. In iPD, serum metabolomics has observed alterations in several metabolic pathways that are related to disease status and clinical manifestations. This study aims to describe the serum metabolomics features of patients with PARK14. Design This case-control biomarker study tested nine patients diagnosed with PARK14. Eight age and sex-matched healthy subjects were recruited as controls. To evaluate the influence of single heterozygous mutation, we enrolled eight healthy one-degree family members of patients with PARK14, two patients diagnosed with early-onset Parkinson's disease (EOPD) who had only a single heterozygous PLA2G6 mutation, and one patient with EOPD without any known pathogenic mutation. Methods The diagnosis of PARK14 was made according to the diagnostic criteria for Parkinson's disease (PD) and confirmed by genetic testing. To study the serum metabolic features, we analyzed participants' serum using UHPLC-QTOF/MS analysis, a well-established technology. Results We quantified 50 compounds of metabolites from the serum of all the study subjects. Metabolites alterations in serum had good predictive accuracy for PARK14 diagnosis (AUC 0.903) and advanced stage in PARK14 (AUC 0.944). Of the 24 metabolites that changed significantly in patients' serum, eight related to lipid metabolism. Oleic acid and xanthine were associated with MMSE scores. Xanthine, L-histidine, and phenol correlated with UPDRS-III scores. Oleic acid and 1-oleoyl-L-alpha-lysophosphatidic acid could also predict the subclass of the more advanced stage in the PLA2G6 Group in ROC models. Conclusion The significantly altered metabolites can be used to differentiate PLA2G6 pathogenic mutations and predict disease severity. Patients with PLA2G6 mutations had elevated lipid compounds in C18:1 and C16:0 groups. The alteration of lipid metabolism might be the key intermediate process in PLA2G6-related disease that needs further investigation.
Collapse
Affiliation(s)
- Chen Chen
- State Key Laboratory of Medical Neurobiology, Department of Neurology and National Research Center for Aging and Medicine, Huashan Hospital, Fudan University, Shanghai, China,State Key Laboratory of Medical Neurobiology, National Center for Neurological Disorders, Huashan Hospital, Fudan University, Shanghai, China
| | - Min-Min Lou
- Interdisciplinary Research Center on Biology and Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences – University of Chinese Academy of Sciences, Shanghai, China
| | - Yi-Min Sun
- State Key Laboratory of Medical Neurobiology, Department of Neurology and National Research Center for Aging and Medicine, Huashan Hospital, Fudan University, Shanghai, China,State Key Laboratory of Medical Neurobiology, National Center for Neurological Disorders, Huashan Hospital, Fudan University, Shanghai, China
| | - Fang Luo
- Interdisciplinary Research Center on Biology and Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences – University of Chinese Academy of Sciences, Shanghai, China
| | - Feng-Tao Liu
- State Key Laboratory of Medical Neurobiology, Department of Neurology and National Research Center for Aging and Medicine, Huashan Hospital, Fudan University, Shanghai, China,State Key Laboratory of Medical Neurobiology, National Center for Neurological Disorders, Huashan Hospital, Fudan University, Shanghai, China
| | - Su-Shan Luo
- State Key Laboratory of Medical Neurobiology, Department of Neurology and National Research Center for Aging and Medicine, Huashan Hospital, Fudan University, Shanghai, China,State Key Laboratory of Medical Neurobiology, National Center for Neurological Disorders, Huashan Hospital, Fudan University, Shanghai, China
| | - Wen-Yuan Wang
- Interdisciplinary Research Center on Biology and Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences – University of Chinese Academy of Sciences, Shanghai, China,*Correspondence: Wen-Yuan Wang,
| | - Jian Wang
- State Key Laboratory of Medical Neurobiology, Department of Neurology and National Research Center for Aging and Medicine, Huashan Hospital, Fudan University, Shanghai, China,State Key Laboratory of Medical Neurobiology, National Center for Neurological Disorders, Huashan Hospital, Fudan University, Shanghai, China,Jian Wang,
| |
Collapse
|
6
|
Dennis EA. Outtakes from My Journey through the World of LIPID MAPS. Molecules 2022; 27:3885. [PMID: 35745008 PMCID: PMC9228998 DOI: 10.3390/molecules27123885] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Revised: 06/13/2022] [Accepted: 06/13/2022] [Indexed: 02/04/2023] Open
Abstract
My laboratory's research on lipids has focused on phospholipases and lipidomics and in many ways has evolved in parallel to the evolution of the lipid field over the past half century. I have reviewed our research elsewhere. Herein, I describe the "side stories" or "outtakes" that parallel the main story that focuses on our laboratory's research. I will emphasize the importance of community activities and describe how I came to initiate and lead the international effort on the Lipid Metabolites and Pathways Strategy (LIPID MAPS). Several of these side activities had a significant effect on discoveries in my laboratory research and its evolution as well as contributing significantly to the development of the LIPID MAPS initiative. These included experience and influences from serving as Editor-in-Chief of the Journal of Lipid Research and Chair and President of the Keystone Symposia on Cell and Molecular Biology as well as other experiences in organizing lipid conferences, teaching on lipid structure and mechanism, and earlier formative administrative and leadership experiences. The relevant influences are summarized herein.
Collapse
Affiliation(s)
- Edward A. Dennis
- Department of Chemistry and Biochemistry, University of California at San Diego, La Jolla, CA 92093-0601, USA;
- Department of Pharmacology, School of Medicine, University of California at San Diego, La Jolla, CA 92093-0601, USA
| |
Collapse
|
7
|
Ruiz Puentes P, Rueda-Gensini L, Valderrama N, Hernández I, González C, Daza L, Muñoz-Camargo C, Cruz JC, Arbeláez P. Predicting target-ligand interactions with graph convolutional networks for interpretable pharmaceutical discovery. Sci Rep 2022; 12:8434. [PMID: 35589824 PMCID: PMC9119967 DOI: 10.1038/s41598-022-12180-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Accepted: 05/05/2022] [Indexed: 02/08/2023] Open
Abstract
Drug Discovery is an active research area that demands great investments and generates low returns due to its inherent complexity and great costs. To identify potential therapeutic candidates more effectively, we propose protein–ligand with adversarial augmentations network (PLA-Net), a deep learning-based approach to predict target–ligand interactions. PLA-Net consists of a two-module deep graph convolutional network that considers ligands’ and targets’ most relevant chemical information, successfully combining them to find their binding capability. Moreover, we generate adversarial data augmentations that preserve relevant biological backgrounds and improve the interpretability of our model, highlighting the relevant substructures of the ligands reported to interact with the protein targets. Our experiments demonstrate that the joint ligand–target information and the adversarial augmentations significantly increase the interaction prediction performance. PLA-Net achieves 86.52% in mean average precision for 102 target proteins with perfect performance for 30 of them, in a curated version of actives as decoys dataset. Lastly, we accurately predict pharmacologically-relevant molecules when screening the ligands of ChEMBL and drug repurposing Hub datasets with the perfect-scoring targets.
Collapse
Affiliation(s)
- Paola Ruiz Puentes
- Center for Research and Formation in Artificial Intelligence, Universidad de los Andes, Bogotá, 111711, Colombia.,Department of Biomedical Engineering, Universidad de los Andes, Bogotá, 111711, Colombia
| | - Laura Rueda-Gensini
- Center for Research and Formation in Artificial Intelligence, Universidad de los Andes, Bogotá, 111711, Colombia.,Department of Biomedical Engineering, Universidad de los Andes, Bogotá, 111711, Colombia
| | - Natalia Valderrama
- Center for Research and Formation in Artificial Intelligence, Universidad de los Andes, Bogotá, 111711, Colombia.,Department of Biomedical Engineering, Universidad de los Andes, Bogotá, 111711, Colombia
| | - Isabela Hernández
- Center for Research and Formation in Artificial Intelligence, Universidad de los Andes, Bogotá, 111711, Colombia.,Department of Biomedical Engineering, Universidad de los Andes, Bogotá, 111711, Colombia
| | - Cristina González
- Center for Research and Formation in Artificial Intelligence, Universidad de los Andes, Bogotá, 111711, Colombia.,Department of Biomedical Engineering, Universidad de los Andes, Bogotá, 111711, Colombia
| | - Laura Daza
- Center for Research and Formation in Artificial Intelligence, Universidad de los Andes, Bogotá, 111711, Colombia.,Department of Biomedical Engineering, Universidad de los Andes, Bogotá, 111711, Colombia
| | - Carolina Muñoz-Camargo
- Department of Biomedical Engineering, Universidad de los Andes, Bogotá, 111711, Colombia
| | - Juan C Cruz
- Department of Biomedical Engineering, Universidad de los Andes, Bogotá, 111711, Colombia
| | - Pablo Arbeláez
- Center for Research and Formation in Artificial Intelligence, Universidad de los Andes, Bogotá, 111711, Colombia. .,Department of Biomedical Engineering, Universidad de los Andes, Bogotá, 111711, Colombia.
| |
Collapse
|
8
|
Dennis EA. Allosteric regulation by membranes and hydrophobic subsites in phospholipase A 2 enzymes determine their substrate specificity. J Biol Chem 2022; 298:101873. [PMID: 35358512 PMCID: PMC9079178 DOI: 10.1016/j.jbc.2022.101873] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Revised: 03/09/2022] [Accepted: 03/14/2022] [Indexed: 11/26/2022] Open
Abstract
Lipids play critical roles in several major chronic diseases of our times, including those that involve inflammatory sequelae such as metabolic syndrome including obesity, insulin sensitivity, and cardiovascular diseases. However, defining the substrate specificity of enzymes of lipid metabolism is a challenging task. For example, phospholipase A2 (PLA2) enzymes constitute a superfamily of degradative, biosynthetic, and signaling enzymes that all act stereospecifically to hydrolyze and release the fatty acids of membrane phospholipids. This review focuses on how membranes interact allosterically with enzymes to regulate cell signaling and metabolic pathways leading to inflammation and other diseases. Our group has developed “substrate lipidomics” to quantify the substrate phospholipid specificity of each PLA2 and coupled this with molecular dynamics simulations to reveal that enzyme specificity is linked to specific hydrophobic binding subsites for membrane phospholipid substrates. We have also defined unexpected headgroup and acyl chain specificity for each of the major human PLA2 enzymes, which explains the observed specificity at a structural level. Finally, we discovered that a unique hydrophobic binding site—and not each enzyme’s catalytic residues or polar headgroup binding site—predominantly determines enzyme specificity. We also discuss how PLA2s release specific fatty acids after allosteric enzyme association with membranes and extraction of the phospholipid substrate, which can be blocked by stereospecific inhibitors. After decades of work, we can now correlate PLA2 specificity and inhibition potency with molecular structure and physiological function.
Collapse
Affiliation(s)
- Edward A Dennis
- Department of Chemistry and Biochemistry and Department of Pharmacology, School of Medicine, University of California at San Diego, La Jolla, California, USA.
| |
Collapse
|
9
|
Geng F, Zhang G, Wang Y, Lü J. Membrane phosphatidylserine allosterically regulates the cytosolic phospholipase A2 activity via an electrostatic-switch mechanism. SOFT MATTER 2022; 18:2203-2210. [PMID: 35226022 DOI: 10.1039/d1sm01791h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Phospholipase A2 (PLA2) is a peripheral membrane protein that plays an essential role in many inflammatory responses. However, the activation mechanisms of PLA2 on the membrane surface have not been fully understood. Herein, we have combined experimental techniques and theoretical approaches to investigate the activation and association of the PLA2 protein on an artificial phospholipid membrane. Using a phosphatidylserine (PS) nanodomain containing membrane to mimic the inflammatory conditions, we found that the activity of cytosolic PLA2s (cPLA2s) increases with higher ratios of PS in the membrane. Molecular dynamics simulations reveal that significant changes in the protein structure are related to negatively charged membranes. In particular, the alteration of negatively charged residues in the C2 domain brings about an opened binding pocket and the catalytic site access to the substrate phospholipid. Meanwhile, the negative residues in the loop 650-665 facilitate the optimal interfacial orientation of the protein with a closed binding pocket on the membrane surface. These results lead us to suggest an electrostatic-switch allosteric mechanism for cPLA2 activation on the cell membrane surface under the inflammatory state.
Collapse
Affiliation(s)
- Feng Geng
- School of Pharmacy, Binzhou Medical University, Yantai 264003, China.
- Jinan Microecological Biomedicine Shandong Laboratory, Jinan 250000, China
| | - Guangxu Zhang
- Jinan Microecological Biomedicine Shandong Laboratory, Jinan 250000, China
- CAS key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
- Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201203, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yadi Wang
- School of Pharmacy, Binzhou Medical University, Yantai 264003, China.
- Jinan Microecological Biomedicine Shandong Laboratory, Jinan 250000, China
| | - Junhong Lü
- School of Pharmacy, Binzhou Medical University, Yantai 264003, China.
- Jinan Microecological Biomedicine Shandong Laboratory, Jinan 250000, China
- CAS key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
- Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201203, China
| |
Collapse
|
10
|
N-Acylated and N-Alkylated 2-Aminobenzothiazoles Are Novel Agents That Suppress the Generation of Prostaglandin E2. Biomolecules 2022; 12:biom12020267. [PMID: 35204768 PMCID: PMC8961538 DOI: 10.3390/biom12020267] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Revised: 01/25/2022] [Accepted: 01/27/2022] [Indexed: 11/23/2022] Open
Abstract
The quest for novel agents to regulate the generation of prostaglandin E2 (PGE2) is of high importance because this eicosanoid is a key player in inflammatory diseases. We synthesized a series of N-acylated and N-alkylated 2-aminobenzothiazoles and related heterocycles (benzoxazoles and benzimidazoles) and evaluated their ability to suppress the cytokine-stimulated generation of PGE2 in rat mesangial cells. 2-Aminobenzothiazoles, either acylated by the 3-(naphthalen-2-yl)propanoyl moiety (GK510) or N-alkylated by a chain carrying a naphthalene (GK543) or a phenyl moiety (GK562) at a distance of three carbon atoms, stand out in inhibiting PGE2 generation, with EC50 values ranging from 118 nM to 177 nM. Both GK510 and GK543 exhibit in vivo anti-inflammatory activity greater than that of indomethacin. Thus, N-acylated or N-alkylated 2-aminobenzothiazoles are novel leads for the regulation of PGE2 formation.
Collapse
|
11
|
Lipoprotein-associated phospholipase A 2: A paradigm for allosteric regulation by membranes. Proc Natl Acad Sci U S A 2022; 119:2102953118. [PMID: 34996868 PMCID: PMC8764669 DOI: 10.1073/pnas.2102953118] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/27/2021] [Indexed: 12/27/2022] Open
Abstract
Lp-PLA2 is a physiologically important human enzyme and an inflammatory biomarker for assessing risk factors associated with cardiovascular diseases. It is associated with low- and high-density lipoproteins in human plasma and acts on the outside of the phospholipid monolayer that coats these particles, in stark contrast to traditional PLA2 enzymes that act on bilayer membranes. This study addresses the allosteric activation of Lp-PLA2 by phospholipid monolayers and membranes, its precise selectivity and specificity for particular oxidized and short acyl-chain phospholipid substrates not previously possible. Of particular importance, this work identifies and confirms by site-directed mutagenesis a phospholipid head-group binding pocket distinct from known drug inhibitor binding pockets that informs us about Lp-PLA2’s mechanism of action and creates opportunities for additional therapeutic approaches. Lipoprotein-associated phospholipase A2 (Lp-PLA2) associates with low- and high-density lipoproteins in human plasma and specifically hydrolyzes circulating oxidized phospholipids involved in oxidative stress. The association of this enzyme with the lipoprotein’s phospholipid monolayer to access its substrate is the most crucial first step in its catalytic cycle. The current study demonstrates unequivocally that a significant movement of a major helical peptide region occurs upon membrane binding, resulting in a large conformational change upon Lp-PLA2 binding to a phospholipid surface. This allosteric regulation of an enzyme’s activity by a large membrane-like interface inducing a conformational change in the catalytic site defines a unique dimension of allosterism. The mechanism by which this enzyme associates with phospholipid interfaces to select and extract a single phospholipid substrate molecule and carry out catalysis is key to understanding its physiological functioning. A lipidomics platform was employed to determine the precise substrate specificity of human recombinant Lp-PLA2 and mutants. This study uniquely elucidates the association mechanism of this enzyme with membranes and its resulting conformational change as well as the extraction and binding of specific oxidized and short acyl-chain phospholipid substrates. Deuterium exchange mass spectrometry coupled with molecular dynamics simulations was used to define the precise specificity of the subsite for the oxidized fatty acid at the sn-2 position of the phospholipid backbone. Despite the existence of several crystal structures of this enzyme cocrystallized with inhibitors, little was understood about Lp-PLA2‘s specificity toward oxidized phospholipids.
Collapse
|
12
|
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.
Collapse
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.
| |
Collapse
|
13
|
Batsika CS, Gerogiannopoulou ADD, Mantzourani C, Vasilakaki S, Kokotos G. The design and discovery of phospholipase A 2 inhibitors for the treatment of inflammatory diseases. Expert Opin Drug Discov 2021; 16:1287-1305. [PMID: 34143707 DOI: 10.1080/17460441.2021.1942835] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
AREAS COVERED This review article summarizes the most important 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 Lp-PLA2), discussing their in vitro and in vivo activities as well as their recent applications and therapeutic properties. Recent findings on the role of PLA2 in the pathobiology of COVID-19 are also discussed. EXPERT OPINION Although a number of PLA2 inhibitors have entered clinical trials, none has reached the market yet. Lipoprotein-associated PLA2 is now considered a biomarker of vascular inflammation rather than a therapeutic target for inhibitors like darapladib. Inhibitors of cytosolic PLA2 may find topical applications for diseases like atopic dermatitis and psoriasis. Inhibitors of secreted PLA2, varespladib and varespladib methyl, are under investigation for repositioning in snakebite envenoming. A deeper understanding of PLA2 enzymes is needed for the development of novel selective inhibitors. Lipidomic technologies combined with medicinal chemistry approaches may be useful tools toward this goal.
Collapse
Affiliation(s)
| | | | - Christiana Mantzourani
- Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis Greece
| | - Sofia Vasilakaki
- Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis Greece
| | - George Kokotos
- Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis Greece
| |
Collapse
|
14
|
The Impact of the Ca 2+-Independent Phospholipase A 2β (iPLA 2β) on Immune Cells. Biomolecules 2021; 11:biom11040577. [PMID: 33920898 PMCID: PMC8071342 DOI: 10.3390/biom11040577] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Revised: 04/06/2021] [Accepted: 04/12/2021] [Indexed: 12/31/2022] Open
Abstract
The Ca2+-independent phospholipase A2β (iPLA2β) is a member of the PLA2 family that has been proposed to have roles in multiple biological processes including membrane remodeling, cell proliferation, bone formation, male fertility, cell death, and signaling. Such involvement has led to the identification of iPLA2β activation in several diseases such as cancer, cardiovascular abnormalities, glaucoma, periodontitis, neurological disorders, diabetes, and other metabolic disorders. More recently, there has been heightened interest in the role that iPLA2β plays in promoting inflammation. Recognizing the potential contribution of iPLA2β in the development of autoimmune diseases, we review this issue in the context of an iPLA2β link with macrophages and T-cells.
Collapse
|
15
|
Dennis EA. Enzyme Hydrophobic Sites and Allosteric Membrane Interactions Regulate Signaling and Mediators of Inflammation. FASEB J 2020. [DOI: 10.1096/fasebj.2020.34.s1.00199] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
16
|
Koutoulogenis GS, Kokotou MG, Hayashi D, Mouchlis VD, Dennis EA, Kokotos G. 2-Oxoester Phospholipase A 2 Inhibitors with Enhanced Metabolic Stability. Biomolecules 2020; 10:biom10030491. [PMID: 32213911 PMCID: PMC7175278 DOI: 10.3390/biom10030491] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2020] [Revised: 03/19/2020] [Accepted: 03/20/2020] [Indexed: 12/21/2022] Open
Abstract
2-Oxoesters constitute an important class of potent and selective inhibitors of human cytosolic phospholipase A2 (GIVA cPLA2) combining an aromatic scaffold or a long aliphatic chain with a short aliphatic chain containing a free carboxylic acid. Although highly potent 2-oxoester inhibitors of GIVA cPLA2 have been developed, their rapid degradation in human plasma limits their pharmaceutical utility. In an effort to address this problem, we designed and synthesized two new 2-oxoesters introducing a methyl group either on the α-carbon to the oxoester functionality or on the carbon carrying the ester oxygen. We studied the in vitro plasma stability of both derivatives and their in vitro inhibitory activity on GIVA cPLA2. Both derivatives exhibited higher plasma stability in comparison with the unsubstituted compound and both derivatives inhibited GIVA cPLA2, however to different degrees. The 2-oxoester containing a methyl group on the α-carbon atom to the oxoester functionality exhibits enhancement of the metabolic stability and retains considerable inhibitory potency.
Collapse
Affiliation(s)
- Giorgos S. Koutoulogenis
- Department of Chemistry, National and Kapodistrian University of Athens, Athens 15771, Greece; (G.S.K.); (M.G.K.)
| | - Maroula G. Kokotou
- Department of Chemistry, National and Kapodistrian University of Athens, Athens 15771, Greece; (G.S.K.); (M.G.K.)
| | - Daiki Hayashi
- Department of Chemistry and Biochemistry and Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, CA 92093-0601, USA; (D.H.); (V.D.M.)
| | - 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, USA; (D.H.); (V.D.M.)
| | - 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, USA; (D.H.); (V.D.M.)
- Correspondence: (E.A.D.); (G.K.); Tel.: +1-858-534-3055 (E.A.D.); +30-210-7274462 (G.K.)
| | - George Kokotos
- Department of Chemistry, National and Kapodistrian University of Athens, Athens 15771, Greece; (G.S.K.); (M.G.K.)
- Correspondence: (E.A.D.); (G.K.); Tel.: +1-858-534-3055 (E.A.D.); +30-210-7274462 (G.K.)
| |
Collapse
|
17
|
Mouchlis VD, Mu C, Hammons R, Dennis EA. Lipidomics-based assays coupled with computational approaches can identify novel phospholipase A 2 inhibitors. Adv Biol Regul 2020; 76:100719. [PMID: 32199750 DOI: 10.1016/j.jbior.2020.100719] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Revised: 03/02/2020] [Accepted: 03/05/2020] [Indexed: 10/24/2022]
Abstract
Phospholipase A2 (PLA2) enzymes play a major role in many diseases including the inflammatory cascade and specific potent small molecule inhibitors could be useful in studying their physiological role as well as for the development of drugs. In order to discover novel small molecule inhibitor platforms for members of the PLA2 superfamily of enzymes, we have applied computational approaches to determine the binding mode of potent inhibitors specific for particular PLA2s to the screening of chemical libraries. This has including the U.S. National Institutes of Health (NIH) National Cancer Institute (NCI) Diversity Set V and the ChemBridge commercial compound libraries. We have then subjected identified inhibitor structures to recently developed lipidomics based screening assays to determine the XI(50) and specificity of the identified compounds for specific PLA2s. Herein we review this approach and report the identity of initial hits for both the Group IVA cytosolic PLA2 and the Group VIA calcium-independent PLA2 that are worthy of further structural modification to develop novel platforms for inhibitor development.
Collapse
Affiliation(s)
- 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, USA.
| | - Carol Mu
- Department of Chemistry and Biochemistry and Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, CA, 92093-0601, USA
| | - Renee Hammons
- Department of Chemistry and Biochemistry and Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, CA, 92093-0601, USA
| | - 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, USA.
| |
Collapse
|
18
|
Dedaki C, Kokotou MG, Mouchlis VD, Limnios D, Lei X, Mu CT, Ramanadham S, Magrioti V, Dennis EA, Kokotos G. β-Lactones: A Novel Class of Ca 2+-Independent Phospholipase A 2 (Group VIA iPLA 2) Inhibitors with the Ability To Inhibit β-Cell Apoptosis. J Med Chem 2019; 62:2916-2927. [PMID: 30798607 DOI: 10.1021/acs.jmedchem.8b01216] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Ca2+-independent phospholipase A2 (GVIA iPLA2) has gained increasing interest recently as it has been recognized as a participant in biological processes underlying diabetes development and autoimmune-based neurological disorders. The development of potent GVIA iPLA2 inhibitors is of great importance because only a few have been reported so far. We present a novel class of GVIA iPLA2 inhibitors based on the β-lactone ring. This functionality in combination with a four-carbon chain carrying a phenyl group at position-3 and a linear propyl group at position-4 of the lactone ring confers excellent potency. trans-3-(4-Phenylbutyl)-4-propyloxetan-2-one (GK563) was identified as being the most potent GVIA iPLA2 inhibitor ever reported ( XI(50) 0.0000021, IC50 1 nM) and also one that is 22 000 times more active against GVIA iPLA2 than GIVA cPLA2. It was found to reduce β-cell apoptosis induced by proinflammatory cytokines, raising the possibility that it can be beneficial in countering autoimmune diseases, such as type 1 diabetes.
Collapse
Affiliation(s)
- Christina Dedaki
- Laboratory of Organic Chemistry, Department of Chemistry , National and Kapodistrian University of Athens , Panepistimiopolis, Athens 15771 , Greece
| | - Maroula G Kokotou
- Laboratory of Organic Chemistry, Department of Chemistry , National and Kapodistrian University of Athens , Panepistimiopolis, Athens 15771 , Greece.,Department of Chemistry and Biochemistry and Department of Pharmacology, School of Medicine , University of California, San Diego , La Jolla, San Diego , California 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, San Diego , California 92093-0601 , United States
| | - Dimitris Limnios
- Laboratory of Organic Chemistry, Department of Chemistry , National and Kapodistrian University of Athens , Panepistimiopolis, Athens 15771 , Greece.,Department of Chemistry and Biochemistry and Department of Pharmacology, School of Medicine , University of California, San Diego , La Jolla, San Diego , California 92093-0601 , United States
| | | | - Carol T Mu
- Department of Chemistry and Biochemistry and Department of Pharmacology, School of Medicine , University of California, San Diego , La Jolla, San Diego , California 92093-0601 , United States
| | | | - Victoria Magrioti
- Laboratory of Organic Chemistry, Department of Chemistry , National and Kapodistrian University of Athens , Panepistimiopolis, Athens 15771 , Greece
| | - Edward A Dennis
- Department of Chemistry and Biochemistry and Department of Pharmacology, School of Medicine , University of California, San Diego , La Jolla, San Diego , California 92093-0601 , United States
| | - George Kokotos
- Laboratory of Organic Chemistry, Department of Chemistry , National and Kapodistrian University of Athens , Panepistimiopolis, Athens 15771 , Greece
| |
Collapse
|