1
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Ekodo Voundi M, Hanekamp W, Lehr M. Synthesis, activity and metabolic stability of propan-2-one substituted tetrazolylalkanoic acids as dual inhibitors of cytosolic phospholipase A 2α and fatty acid amide hydrolase. RSC Med Chem 2023; 14:2079-2088. [PMID: 37859716 PMCID: PMC10583809 DOI: 10.1039/d3md00224a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Accepted: 08/09/2023] [Indexed: 10/21/2023] Open
Abstract
The serine hydrolases cytosolic phospholipase A2α (cPLA2α) and fatty acid amide hydrolase (FAAH) are interesting targets for the development of new anti-inflammatory and analgesic drugs. Structural modifications of a potent dual inhibitor with a propan-2-one substituted tetrazolylpropionic acid moiety led to compounds with also nanomolar activity against both enzymes but better physicochemical properties. The structure-activity relationships showed that the variations had partially divergent effects on the inhibitory activity of the compounds towards cPLA2α and FAAH reflecting differences in the binding mode to the enzymes. Furthermore, the metabolic stability of the target structures was investigated in vitro.
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Affiliation(s)
- Merlin Ekodo Voundi
- Institute of Pharmaceutical and Medicinal Chemistry, University of Münster Corrensstrasse 48 48149 Münster Germany
| | - Walburga Hanekamp
- Institute of Pharmaceutical and Medicinal Chemistry, University of Münster Corrensstrasse 48 48149 Münster Germany
| | - Matthias Lehr
- Institute of Pharmaceutical and Medicinal Chemistry, University of Münster Corrensstrasse 48 48149 Münster Germany
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2
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Ni WF, Zhou KL, Zhang HJ, Chen YT, Hu XL, Cai WT, Wang XY. Functions and mechanisms of cytosolic phospholipase A 2 in central nervous system trauma. Neural Regen Res 2023; 18:258-266. [PMID: 35900400 PMCID: PMC9396495 DOI: 10.4103/1673-5374.346460] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
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3
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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.
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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
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4
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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.
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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.
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5
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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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6
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Robello M, Barresi E, Baglini E, Salerno S, Taliani S, Settimo FD. The Alpha Keto Amide Moiety as a Privileged Motif in Medicinal Chemistry: Current Insights and Emerging Opportunities. J Med Chem 2021; 64:3508-3545. [PMID: 33764065 PMCID: PMC8154582 DOI: 10.1021/acs.jmedchem.0c01808] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Over the years, researchers in drug discovery have taken advantage of the use of privileged structures to design innovative hit/lead molecules. The α-ketoamide motif is found in many natural products, and it has been widely exploited by medicinal chemists to develop compounds tailored to a vast range of biological targets, thus presenting clinical potential for a plethora of pathological conditions. The purpose of this perspective is to provide insights into the versatility of this chemical moiety as a privileged structure in drug discovery. After a brief analysis of its physical-chemical features and synthetic procedures to obtain it, α-ketoamide-based classes of compounds are reported according to the application of this motif as either a nonreactive or reactive moiety. The goal is to highlight those aspects that may be useful to understanding the perspectives of employing the α-ketoamide moiety in the rational design of compounds able to interact with a specific target.
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Affiliation(s)
- Marco Robello
- Synthetic Bioactive Molecules Section, LBC, NIDDK, NIH, 8 Center Drive, Room 404, Bethesda, Maryland 20892, United States
| | - Elisabetta Barresi
- Department of Pharmacy, University of Pisa, Via Bonanno 6, 56126 Pisa, Italy
| | - Emma Baglini
- Department of Pharmacy, University of Pisa, Via Bonanno 6, 56126 Pisa, Italy
| | - Silvia Salerno
- Department of Pharmacy, University of Pisa, Via Bonanno 6, 56126 Pisa, Italy
| | - Sabrina Taliani
- Department of Pharmacy, University of Pisa, Via Bonanno 6, 56126 Pisa, Italy
| | - Federico Da Settimo
- Department of Pharmacy, University of Pisa, Via Bonanno 6, 56126 Pisa, Italy
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7
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Vasilakaki S, Kraml J, Schauperl M, Liedl KR, Kokotos G. Hydration thermodynamics of cytosolic phospholipase A 2 GIVA predict its membrane-associated parts and its highly hydrated binding site. J Biomol Struct Dyn 2020; 39:953-959. [PMID: 32085688 DOI: 10.1080/07391102.2020.1733665] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
During biological events, the water molecules associated with the protein are re-oriented to adapt to the new conditions, inducing changes in the system's free energy. The characterization of water structure and thermodynamics may facilitate the prediction of certain biological events, such as the binding of a ligand and the membrane-associated parts of a protein. In this computational study, we calculated the hydration thermodynamics of cytosolic phospholipase A2 group IV (GIVA cPLA2) to study the hydration properties of the protein's surface and binding pocket. Hydrophobicity scales and the Grid Inhomogeneous Solvation Theory (GIST) tool were employed for the calculations. The hydrophobic areas of the protein's surface were predicted more accurately with the GIST method rather than with the hydrophobicity scales. Based on this, a model of the protein-membrane complex was constructed. In addition, the calculation revealed the highly hydrated binding pocket that further contribute to our understanding of the ligands' binding. Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Sofia Vasilakaki
- Laboratory of Organic Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, Athens, Greece
| | - Johannes Kraml
- Institute of General, Inorganic and Theoretical Chemistry, and Center for Molecular Biosciences Innsbruck (CMBI), University of Innsbruck, Innsbruck, Tyrol, Austria
| | - Michael Schauperl
- Institute of General, Inorganic and Theoretical Chemistry, and Center for Molecular Biosciences Innsbruck (CMBI), University of Innsbruck, Innsbruck, Tyrol, Austria
| | - Klaus R Liedl
- Institute of General, Inorganic and Theoretical Chemistry, and Center for Molecular Biosciences Innsbruck (CMBI), University of Innsbruck, Innsbruck, Tyrol, Austria
| | - George Kokotos
- Laboratory of Organic Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, Athens, Greece
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8
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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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9
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Mouchlis VD, Armando A, Dennis EA. Substrate-Specific Inhibition Constants for Phospholipase A 2 Acting on Unique Phospholipid Substrates in Mixed Micelles and Membranes Using Lipidomics. J Med Chem 2019; 62:1999-2007. [PMID: 30615445 PMCID: PMC6398150 DOI: 10.1021/acs.jmedchem.8b01568] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Assaying lipolytic enzymes is extremely challenging because they act on water-insoluble lipid substrates, which are normally components of micelles, vesicles, and cellular membranes. We extended a new lipidomics-based liquid chromatographic-mass spectrometric assay for phospholipases A2 to perform inhibition analysis using a variety of commercially available synthetic and natural phospholipids as substrates. Potent and selective inhibitors of three recombinant human enzymes, including cytosolic, calcium-independent, and secreted phospholipases A2 were used to establish and validate this assay. This is a novel use of dose-response curves with a mixture of phospholipid substrates, not previously feasible using traditional radioactive assays. The new application of lipidomics to developing assays for lipolytic enzymes revolutionizes in vitro testing for the discovery of potent and selective inhibitors using mixtures of membranelike substrates.
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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
| | - Aaron Armando
- 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
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10
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Abstract
Since I started doing scientific research, I've been fascinated by the interplay of protein structure and dynamics and how they together mediate protein function. A particular area of interest has been in understanding the mechanistic basis of how lipid-signaling enzymes function on membrane surfaces. In this award lecture article, I will describe my laboratory's studies on the structure and dynamics of lipid-signaling enzymes on membrane surfaces. This is important, as many lipid-signaling enzymes are regulated through dynamic regulatory mechanisms that control their enzymatic activity. This article will discuss my continued enthusiasm in using a synergistic application of hydrogen-deuterium exchange MS (HDX-MS) with other structural biology techniques to probe the mechanistic basis for how membrane-localized signaling enzymes are regulated and how these approaches can be used to understand how they are misregulated in disease. I will discuss specific examples of how we have used HDX-MS to study phosphoinositide kinases and the protein kinase Akt. An important focus will be on a description of how HDX-MS can be used as a powerful tool to optimize the design of constructs for X-ray crystallography and EM. The use of a diverse toolbox of biophysical methods has revealed novel insight into the complex and varied regulatory networks that control the function of lipid-signaling enzymes and enabled unique insight into the mechanics of membrane recruitment.
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Affiliation(s)
- John E Burke
- From the Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia V8W 2Y2, Canada
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11
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Xiao Y, Li M, Larocque R, Zhang F, Malhotra A, Chen J, Linhardt RJ, Konermann L, Xu D. Dimerization interface of osteoprotegerin revealed by hydrogen-deuterium exchange mass spectrometry. J Biol Chem 2018; 293:17523-17535. [PMID: 30254073 DOI: 10.1074/jbc.ra118.004489] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Revised: 09/20/2018] [Indexed: 01/13/2023] Open
Abstract
Previous structural studies of osteoprotegerin (OPG), a crucial negative regulator of bone remodeling and osteoclastogenesis, were mostly limited to the N-terminal ligand-binding domains. It is now known that the three C-terminal domains of OPG also play essential roles in its function by mediating OPG dimerization, OPG-heparan sulfate (HS) interactions, and formation of the OPG-HS-receptor activator of nuclear factor κB ligand (RANKL) ternary complex. Employing hydrogen-deuterium exchange MS methods, here we investigated the structure of full-length OPG in complex with HS or RANKL in solution. Our data revealed two noteworthy aspects of the OPG structure. First, we found that the interconnection between the N- and C-terminal domains is much more rigid than previously thought, possibly because of hydrophobic interactions between the fourth cysteine-rich domain and the first death domain. Second, we observed that two hydrophobic clusters located in two separate C-terminal domains directly contribute to OPG dimerization, likely by forming a hydrophobic dimerization interface. Aided by site-directed mutagenesis, we further demonstrated that an intact dimerization interface is essential for the biological activity of OPG. Our study represents an important step toward deciphering the structure-function relationship of the full-length OPG protein.
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Affiliation(s)
- Yiming Xiao
- From the Department of Chemistry, University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Miaomiao Li
- the Department of Oral Biology, University of Buffalo, Buffalo, New York 14214, and
| | - Rinzhi Larocque
- the Department of Oral Biology, University of Buffalo, Buffalo, New York 14214, and
| | - Fuming Zhang
- the Department of Chemical and Biological Engineering, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York 12180
| | - Anju Malhotra
- the Department of Chemical and Biological Engineering, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York 12180
| | - Jianle Chen
- the Department of Chemical and Biological Engineering, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York 12180
| | - Robert J Linhardt
- the Department of Chemical and Biological Engineering, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York 12180
| | - Lars Konermann
- From the Department of Chemistry, University of Western Ontario, London, Ontario N6A 5B7, Canada,
| | - Ding Xu
- the Department of Oral Biology, University of Buffalo, Buffalo, New York 14214, and
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12
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Phospholipase A 2 catalysis and lipid mediator lipidomics. Biochim Biophys Acta Mol Cell Biol Lipids 2018; 1864:766-771. [PMID: 30905345 DOI: 10.1016/j.bbalip.2018.08.010] [Citation(s) in RCA: 84] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Revised: 08/10/2018] [Accepted: 08/16/2018] [Indexed: 01/09/2023]
Abstract
Phospholipase A2 (PLA2) enzymes are the upstream regulators of the eicosanoid pathway liberating free arachidonic acid from the sn-2 position of membrane phospholipids. Free intracellular arachidonic acid serves as a substrate for the eicosanoid biosynthetic enzymes including cyclooxygenases, lipoxygenases, and cytochrome P450s that lead to inflammation. The Group IVA cytosolic (cPLA2), Group VIA calcium-independent (iPLA2), and Group V secreted (sPLA2) are three well-characterized human enzymes that have been implicated in eicosanoid formation. In this review, we will introduce and summarize the regulation of catalytic activity and cellular localization, structural characteristics, interfacial activation and kinetics, substrate specificity, inhibitor binding and interactions, and the downstream implications for eicosanoid biosynthesis of these three important PLA2 enzymes.
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13
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Zhang Z, Liang WG, Bailey LJ, Tan YZ, Wei H, Wang A, Farcasanu M, Woods VA, McCord LA, Lee D, Shang W, Deprez-Poulain R, Deprez B, Liu DR, Koide A, Koide S, Kossiakoff AA, Li S, Carragher B, Potter CS, Tang WJ. Ensemble cryoEM elucidates the mechanism of insulin capture and degradation by human insulin degrading enzyme. eLife 2018; 7:33572. [PMID: 29596046 PMCID: PMC5910022 DOI: 10.7554/elife.33572] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Accepted: 03/28/2018] [Indexed: 11/29/2022] Open
Abstract
Insulin degrading enzyme (IDE) plays key roles in degrading peptides vital in type two diabetes, Alzheimer's, inflammation, and other human diseases. However, the process through which IDE recognizes peptides that tend to form amyloid fibrils remained unsolved. We used cryoEM to understand both the apo- and insulin-bound dimeric IDE states, revealing that IDE displays a large opening between the homologous ~55 kDa N- and C-terminal halves to allow selective substrate capture based on size and charge complementarity. We also used cryoEM, X-ray crystallography, SAXS, and HDX-MS to elucidate the molecular basis of how amyloidogenic peptides stabilize the disordered IDE catalytic cleft, thereby inducing selective degradation by substrate-assisted catalysis. Furthermore, our insulin-bound IDE structures explain how IDE processively degrades insulin by stochastically cutting either chain without breaking disulfide bonds. Together, our studies provide a mechanism for how IDE selectively degrades amyloidogenic peptides and offers structural insights for developing IDE-based therapies.
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Affiliation(s)
- Zhening Zhang
- National Resource for Automated Molecular Microscopy, Simons Electron Microscopy Center, New York Structural Biology Center, New York, United States
| | - Wenguang G Liang
- Ben-May Institute for Cancer Research, The University of Chicago, Chicago, United States
| | - Lucas J Bailey
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, United States
| | - Yong Zi Tan
- National Resource for Automated Molecular Microscopy, Simons Electron Microscopy Center, New York Structural Biology Center, New York, United States.,Department of Biochemistry and Molecular Biophysics, Columbia University, New York, United States
| | - Hui Wei
- National Resource for Automated Molecular Microscopy, Simons Electron Microscopy Center, New York Structural Biology Center, New York, United States
| | - Andrew Wang
- Ben-May Institute for Cancer Research, The University of Chicago, Chicago, United States
| | - Mara Farcasanu
- Ben-May Institute for Cancer Research, The University of Chicago, Chicago, United States
| | - Virgil A Woods
- Department of Medicine, University of California, San Diego, La Jolla, United States
| | - Lauren A McCord
- Ben-May Institute for Cancer Research, The University of Chicago, Chicago, United States
| | - David Lee
- Department of Medicine, University of California, San Diego, La Jolla, United States
| | - Weifeng Shang
- BioCAT, Argonne National Laboratory, Illinois, United States
| | | | - Benoit Deprez
- Univ. Lille, INSERM, Institut Pasteur de Lille, Lille, France
| | - David R Liu
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, United States
| | - Akiko Koide
- Perlmutter Cancer Center, New York University School of Medicine, New York, United States.,New York University Langone Medical Center, New York University School of Medicine, New York, United States.,Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, United States
| | - Shohei Koide
- Perlmutter Cancer Center, New York University School of Medicine, New York, United States.,New York University Langone Medical Center, New York University School of Medicine, New York, United States.,Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, United States
| | - Anthony A Kossiakoff
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, United States
| | - Sheng Li
- Department of Medicine, University of California, San Diego, La Jolla, United States
| | - Bridget Carragher
- National Resource for Automated Molecular Microscopy, Simons Electron Microscopy Center, New York Structural Biology Center, New York, United States.,Department of Biochemistry and Molecular Biophysics, Columbia University, New York, United States
| | - Clinton S Potter
- National Resource for Automated Molecular Microscopy, Simons Electron Microscopy Center, New York Structural Biology Center, New York, United States.,Department of Biochemistry and Molecular Biophysics, Columbia University, New York, United States
| | - Wei-Jen Tang
- Ben-May Institute for Cancer Research, The University of Chicago, Chicago, United States
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14
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Mouchlis VD, Chen Y, McCammon JA, Dennis EA. Membrane Allostery and Unique Hydrophobic Sites Promote Enzyme Substrate Specificity. J Am Chem Soc 2018; 140:3285-3291. [PMID: 29342349 PMCID: PMC5846079 DOI: 10.1021/jacs.7b12045] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
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We
demonstrate that lipidomics coupled with molecular dynamics
reveal unique phospholipase A2 specificity toward membrane
phospholipid substrates. We discovered unexpected headgroup and acyl-chain
specificity for three major human phospholipases A2. The
differences between each enzyme’s specificity, coupled with
molecular dynamics-based structural and binding studies, revealed
unique binding sites and interfacial surface binding moieties for
each enzyme that explain the observed specificity at a hitherto inaccessible
structural level. Surprisingly, we discovered that a unique hydrophobic
binding site for the cleaved fatty acid dominates each enzyme’s
specificity rather than its catalytic residues and polar headgroup
binding site. Molecular dynamics simulations revealed the optimal
phospholipid binding mode leading to a detailed understanding of the
preference of cytosolic phospholipase A2 for cleavage of
proinflammatory arachidonic acid, calcium-independent phospholipase
A2, which is involved in membrane remodeling for cleavage
of linoleic acid and for antibacterial secreted phospholipase A2 favoring linoleic acid, saturated fatty acids, and phosphatidylglycerol.
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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
| | - Yuan Chen
- Department of Chemistry and Biochemistry and Department of Pharmacology, School of Medicine , University of California , San Diego, La Jolla , California 92093-0601 , United States
| | - J Andrew McCammon
- 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
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15
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Offenbacher AR, Iavarone AT, Klinman JP. Hydrogen-deuterium exchange reveals long-range dynamical allostery in soybean lipoxygenase. J Biol Chem 2018; 293:1138-1148. [PMID: 29191828 PMCID: PMC5787793 DOI: 10.1074/jbc.m117.817197] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Revised: 11/28/2017] [Indexed: 11/06/2022] Open
Abstract
In lipoxygenases, the topologically conserved C-terminal domain catalyzes the oxidation of polyunsaturated fatty acids, generating an assortment of biologically relevant signaling mediators. Plant and animal lipoxygenases also contain a 100-150-amino acid N-terminal C2-like domain that has been implicated in interactions with isolated fatty acids and at the phospholipid bilayer. These interactions may lead to increased substrate availability and contribute to the regulation of active-site catalysis. Because of a lack of structural information, a molecular understanding of this lipid-protein interaction remains unresolved. Herein, we employed hydrogen-deuterium exchange MS (HDXMS) to spatially resolve changes in protein conformation upon interaction of soybean lipoxygenase with a fatty acid surrogate, oleyl sulfate (OS), previously shown to act at a site separate from the substrate-binding site. Specific, OS-induced conformational changes are detected both at the N-terminal domain and within the substrate portal nearly 30 Å away. Combining previously measured kinetic properties in the presence of OS with its impact on the Kd for linoleic acid substrate binding, we conclude that OS binding brings about an increase in rate constants for both the ingress and egress of substrate. We discuss the role of OS-induced changes in protein flexibility in the context of changes in the mechanism of substrate acquisition.
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Affiliation(s)
- Adam R Offenbacher
- From the Department of Chemistry, California Institute for Quantitative Biosciences (QB3), and
| | - Anthony T Iavarone
- From the Department of Chemistry, California Institute for Quantitative Biosciences (QB3), and
| | - Judith P Klinman
- From the Department of Chemistry, California Institute for Quantitative Biosciences (QB3), and
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720
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16
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Fast CS, Vahidi S, Konermann L. Changes in Enzyme Structural Dynamics Studied by Hydrogen Exchange-Mass Spectrometry: Ligand Binding Effects or Catalytically Relevant Motions? Anal Chem 2017; 89:13326-13333. [DOI: 10.1021/acs.analchem.7b03506] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Affiliation(s)
- Courtney S. Fast
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Siavash Vahidi
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Lars Konermann
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
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17
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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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18
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Masson GR, Jenkins ML, Burke JE. An overview of hydrogen deuterium exchange mass spectrometry (HDX-MS) in drug discovery. Expert Opin Drug Discov 2017; 12:981-994. [PMID: 28770632 DOI: 10.1080/17460441.2017.1363734] [Citation(s) in RCA: 89] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
INTRODUCTION Hydrogen deuterium exchange mass spectrometry (HDX-MS) is a powerful methodology to study protein dynamics, protein folding, protein-protein interactions, and protein small molecule interactions. The development of novel methodologies and technical advancements in mass spectrometers has greatly expanded the accessibility and acceptance of this technique within both academia and industry. Areas covered: This review examines the theoretical basis of how amide exchange occurs, how different mass spectrometer approaches can be used for HDX-MS experiments, as well as the use of HDX-MS in drug development, specifically focusing on how HDX-MS is used to characterize bio-therapeutics, and its use in examining protein-protein and protein small molecule interactions. Expert opinion: HDX-MS has been widely accepted within the pharmaceutical industry for the characterization of bio-therapeutics as well as in the mapping of antibody drug epitopes. However, there is room for this technique to be more widely used in the drug discovery process. This is particularly true in the use of HDX-MS as a complement to other high-resolution structural approaches, as well as in the development of small molecule therapeutics that can target both active-site and allosteric binding sites.
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Affiliation(s)
- Glenn R Masson
- a Protein and Nucleic Acid Chemistry Division , MRC Laboratory of Molecular Biology , Cambridge , UK
| | - Meredith L Jenkins
- b Department of Biochemistry and Microbiology , University of Victoria , Victoria , Canada
| | - John E Burke
- b Department of Biochemistry and Microbiology , University of Victoria , Victoria , Canada
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19
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Xiao Y, Shaw GS, Konermann L. Calcium-Mediated Control of S100 Proteins: Allosteric Communication via an Agitator/Signal Blocking Mechanism. J Am Chem Soc 2017; 139:11460-11470. [PMID: 28758397 DOI: 10.1021/jacs.7b04380] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Allosteric proteins possess dynamically coupled residues for the propagation of input signals to distant target binding sites. The input signals usually correspond to "effector is present" or "effector is not present". Many aspects of allosteric regulation remain incompletely understood. This work focused on S100A11, a dimeric EF-hand protein with two hydrophobic target binding sites. An annexin peptide (Ax) served as the target. Target binding is allosterically controlled by Ca2+ over a distance of ∼26 Å. Ca2+ promotes formation of a [Ca4 S100 Ax2] complex, where the Ax peptides are accommodated between helices III/IV and III'/IV'. Without Ca2+ these binding sites are closed, precluding interactions with Ax. The allosteric mechanism was probed by microsecond MD simulations in explicit water, complemented by hydrogen exchange mass spectrometry (HDX/MS). Consistent with experimental data, MD runs in the absence of Ca2+ and Ax culminated in target binding site closure. In simulations on [Ca4 S100] the target binding sites remained open. These results capture the essence of allosteric control, revealing how Ca2+ prevents binding site closure. Both HDX/MS and MD data showed that the metalation sites become more dynamic after Ca2+ loss. However, these enhanced dynamics do not represent the primary trigger of the allosteric cascade. Instead, a labile salt bridge acts as an incessantly active "agitator" that destabilizes the packing of adjacent residues, causing a domino chain of events that culminates in target binding site closure. This agitator represents the starting point of the allosteric signal propagation pathway. Ca2+ binding rigidifies elements along this pathway, thereby blocking signal transmission. This blocking mechanism does not conform to the commonly held view that allosteric communication pathways generally originate at the sites where effectors interact with the protein.
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Affiliation(s)
- Yiming Xiao
- Department of Chemistry, The University of Western Ontario , London, Ontario N6A 5B7, Canada
| | - Gary S Shaw
- Department of Chemistry, The University of Western Ontario , London, Ontario N6A 5B7, Canada
| | - Lars Konermann
- Department of Chemistry, The University of Western Ontario , London, Ontario N6A 5B7, Canada
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20
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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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21
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Vadas O, Jenkins ML, Dornan GL, Burke JE. Using Hydrogen-Deuterium Exchange Mass Spectrometry to Examine Protein-Membrane Interactions. Methods Enzymol 2016; 583:143-172. [PMID: 28063489 DOI: 10.1016/bs.mie.2016.09.008] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Many fundamental cellular processes are controlled via assembly of a network of proteins at membrane surfaces. The proper recruitment of proteins to membranes can be controlled by a wide variety of mechanisms, including protein lipidation, protein-protein interactions, posttranslational modifications, and binding to specific lipid species present in membranes. There are, however, only a limited number of analytical techniques that can study the assembly of protein-membrane complexes at the molecular level. A relatively new addition to the set of techniques available to study these protein-membrane systems is the use of hydrogen-deuterium exchange mass spectrometry (HDX-MS). HDX-MS experiments measure protein conformational dynamics in their native state, based on the rate of exchange of amide hydrogens with solvent. This review discusses the use of HDX-MS as a tool to identify the interfaces of proteins with membranes and membrane-associated proteins, as well as define conformational changes elicited by membrane recruitment. Specific examples will focus on the use of HDX-MS to examine how large macromolecular protein complexes are recruited and activated on membranes, and how both posttranslational modifications and cancer-linked oncogenic mutations affect these processes.
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Affiliation(s)
- O Vadas
- Pharmaceutical Sciences Section, University of Geneva, Geneva, Switzerland
| | | | - G L Dornan
- University of Victoria, Victoria BC, Canada
| | - J E Burke
- University of Victoria, Victoria BC, Canada.
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22
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Barbour SE, Ramanadham S. Analyses of Calcium-Independent Phospholipase A 2beta (iPLA 2β) in Biological Systems. Methods Enzymol 2016; 583:119-141. [PMID: 28063488 DOI: 10.1016/bs.mie.2016.09.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/23/2023]
Abstract
The Ca2+-independent phospholipases A2 (iPLA2s) are part of a diverse family of PLA2s, manifest activity in the absence of Ca2+, are ubiquitous, and participate in a variety of biological processes. Among the iPLA2s, the cytosolic iPLA2β has received considerable attention and ongoing studies from various laboratories suggest that dysregulation of iPLA2β can have a profound impact on the onset and/or progression of many diseases (e.g., cardiovascular, neurological, metabolic, autoimmune). Therefore, appropriate approaches are warranted to gain a better understanding of the role of iPLA2β in vivo and its contribution to pathophysiology. Given that iPLA2β is very labile, its basal expression is low in a number of cell systems, and that crystal structure of iPLA2β is not yet available, careful and efficient protocols are needed to appropriately assess iPLA2β biochemistry, dynamics, and membrane association. Here, step-by-step details are provided to (a) measure iPLA2β-specific activity in cell lines or tissue preparations (using a simple radiolabel-based assay) and assess the impact of stimuli and inhibitors on resting- and disease-state iPLA2β activity, (b) purify the iPLA2β to near homogeneity (via sequential chromatography) from cell line or tissue preparations, enabling concentration of the enzyme for subsequent analyses (e.g., proteomics), and (c) employ hydrogen/deuterium exchange mass spectrometry analyses to probe both the structure of iPLA2β and dynamics of its association with the membranes, substrates, and inhibitors.
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Affiliation(s)
- S E Barbour
- University of Georgia at Athens, Athens, GA, United States
| | - S Ramanadham
- Comprehensive Diabetes Center, University of Alabama at Birmingham, Birmingham, AL, United States.
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23
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Probing the dynamic regulation of peripheral membrane proteins using hydrogen deuterium exchange-MS (HDX-MS). Biochem Soc Trans 2016; 43:773-86. [PMID: 26517882 DOI: 10.1042/bst20150065] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Many cellular signalling events are controlled by the selective recruitment of protein complexes to membranes. Determining the molecular basis for how lipid signalling complexes are recruited, assembled and regulated on specific membrane compartments has remained challenging due to the difficulty of working in conditions mimicking native biological membrane environments. Enzyme recruitment to membranes is controlled by a variety of regulatory mechanisms, including binding to specific lipid species, protein-protein interactions, membrane curvature, as well as post-translational modifications. A powerful tool to study the regulation of membrane signalling enzymes and complexes is hydrogen deuterium exchange-MS (HDX-MS), a technique that allows for the interrogation of protein dynamics upon membrane binding and recruitment. This review will highlight the theory and development of HDX-MS and its application to examine the molecular basis of lipid signalling enzymes, specifically the regulation and activation of phosphoinositide 3-kinases (PI3Ks).
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24
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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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25
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Wang H, Klein MG, Snell G, Lane W, Zou H, Levin I, Li K, Sang BC. Structure of Human GIVD Cytosolic Phospholipase A2 Reveals Insights into Substrate Recognition. J Mol Biol 2016; 428:2769-79. [PMID: 27220631 DOI: 10.1016/j.jmb.2016.05.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2016] [Revised: 05/09/2016] [Accepted: 05/13/2016] [Indexed: 11/18/2022]
Abstract
Cytosolic phospholipases A2 (cPLA2s) consist of a family of calcium-sensitive enzymes that function to generate lipid second messengers through hydrolysis of membrane-associated glycerophospholipids. The GIVD cPLA2 (cPLA2δ) is a potential drug target for developing a selective therapeutic agent for the treatment of psoriasis. Here, we present two X-ray structures of human cPLA2δ, capturing an apo state, and in complex with a substrate-like inhibitor. Comparison of the apo and inhibitor-bound structures reveals conformational changes in a flexible cap that allows the substrate to access the relatively buried active site, providing new insight into the mechanism for substrate recognition. The cPLA2δ structure reveals an unexpected second C2 domain that was previously unrecognized from sequence alignments, placing cPLA2δ into the class of membrane-associated proteins that contain a tandem pair of C2 domains. Furthermore, our structures elucidate novel inter-domain interactions and define three potential calcium-binding sites that are likely important for regulation and activation of enzymatic activity. These findings provide novel insights into the molecular mechanisms governing cPLA2's function in signal transduction.
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Affiliation(s)
- Hui Wang
- Department of Structural Biology, Takeda California, San Diego, CA 92121, USA.
| | - Michael G Klein
- Department of Structural Biology, Takeda California, San Diego, CA 92121, USA.
| | - Gyorgy Snell
- Department of Structural Biology, Takeda California, San Diego, CA 92121, USA
| | - Weston Lane
- Department of Structural Biology, Takeda California, San Diego, CA 92121, USA
| | - Hua Zou
- Department of Structural Biology, Takeda California, San Diego, CA 92121, USA
| | - Irena Levin
- Department of Structural Biology, Takeda California, San Diego, CA 92121, USA
| | - Ke Li
- Department of Structural Biology, Takeda California, San Diego, CA 92121, USA
| | - Bi-Ching Sang
- Department of Structural Biology, Takeda California, San Diego, CA 92121, USA
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26
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Computer-aided drug design guided by hydrogen/deuterium exchange mass spectrometry: A powerful combination for the development of potent and selective inhibitors of Group VIA calcium-independent phospholipase A 2. Bioorg Med Chem 2016; 24:4801-4811. [PMID: 27320659 DOI: 10.1016/j.bmc.2016.05.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2016] [Revised: 05/05/2016] [Accepted: 05/09/2016] [Indexed: 11/20/2022]
Abstract
Potent and selective inhibitors for phospholipases A2 (PLA2) are useful for studying their intracellular functions. PLA2 enzymes liberate arachidonic acid from phospholipids activating eicosanoid pathways that involve cyclooxygenase (COX) and lipoxygenase (LOX) leading to inflammation. Anti-inflammatory drugs target COX and LOX; thus, PLA2 can also be targeted to diminish inflammation at an earlier stage in the process. This paper describes the employment of enzymatic assays, hydrogen/deuterium exchange mass spectrometry (DXMS) and computational chemistry to develop PLA2 inhibitors. Beta-thioether trifluoromethylketones (TFKs) were screened against human GVIA calcium-independent, GIVA cytosolic and GV secreted PLA2s. These compounds exhibited inhibition toward Group VIA calcium-independent PLA2 (GVIA iPLA2), with the most potent and selective inhibitor 3 (OTFP) obtaining an XI(50) of 0.0002 mole fraction (IC50 of 110nM). DXMS binding experiments in the presence of OTFP revealed the peptide regions of GVIA iPLA2 that interact with the inhibitor. Molecular docking and dynamics simulations in the presence of a membrane were guided by the DXMS data in order to identify the binding mode of OTFP. Clustering analysis showed the binding mode of OTFP that occupied 70% of the binding modes occurring during the simulation. The resulted 3D complex was used for docking studies and a structure-activity relationship (SAR) was established. This paper describes a novel multidisciplinary approach in which a 3D complex of GVIA iPLA2 with an inhibitor is reported and validated by experimental data. The SAR showed that the sulfur atom is vital for the potency of beta-thioether analogues, while the hydrophobic chain is important for selectivity. This work constitutes the foundation for further design, synthesis and inhibition studies in order to develop new beta-thioether analogues that are potent and selective for GVIA iPLA2 exclusively.
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27
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Mouchlis VD, Limnios D, Kokotou MG, Barbayianni E, Kokotos G, McCammon JA, Dennis EA. Development of Potent and Selective Inhibitors for Group VIA Calcium-Independent Phospholipase A2 Guided by Molecular Dynamics and Structure-Activity Relationships. J Med Chem 2016; 59:4403-14. [PMID: 27087127 DOI: 10.1021/acs.jmedchem.6b00377] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The development of inhibitors for phospholipase A2 (PLA2) is important in elucidating the enzymes implication in various biological pathways. PLA2 enzymes are an important pharmacological target implicated in various inflammatory diseases. Computational chemistry, organic synthesis, and in vitro assays were employed to develop potent and selective inhibitors for group VIA calcium-independent PLA2. A set of fluoroketone inhibitors was studied for their binding mode with two human cytosolic PLA2 enzymes: group IVA cPLA2 and group VIA iPLA2. New compounds were synthesized and assayed toward three major PLA2s. This study led to the development of four potent and selective thioether fluoroketone inhibitors as well as a thioether keto-1,2,4-oxadiazole inhibitor for GVIA iPLA2, which will serve as lead compounds for future development and studies. The keto-1,2,4-oxadiazole functionality with a thioether is a novel structure, and it will be used as a lead to develop inhibitors with higher potency and selectivity toward GVIA iPLA2.
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Affiliation(s)
- Varnavas D Mouchlis
- Department of Pharmacology and Department of Chemistry and Biochemistry, School of Medicine, University of California, San Diego , La Jolla, California 92093-0601, United States
| | - Dimitris Limnios
- 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
| | - Efrosini Barbayianni
- Laboratory of Organic Chemistry, Department of Chemistry, National and Kapodistrian University of Athens , Panepistimiopolis, Athens 15771, Greece
| | - George Kokotos
- Laboratory of Organic Chemistry, Department of Chemistry, National and Kapodistrian University of Athens , Panepistimiopolis, Athens 15771, Greece
| | - J Andrew McCammon
- Department of Pharmacology and Department of Chemistry and Biochemistry, School of Medicine, University of California, San Diego , La Jolla, California 92093-0601, United States
| | - Edward A Dennis
- Department of Pharmacology and Department of Chemistry and Biochemistry, School of Medicine, University of California, San Diego , La Jolla, California 92093-0601, United States
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28
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Membrane and inhibitor interactions of intracellular phospholipases A2. Adv Biol Regul 2015; 61:17-24. [PMID: 26774606 DOI: 10.1016/j.jbior.2015.11.011] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Revised: 11/19/2015] [Accepted: 11/20/2015] [Indexed: 02/06/2023]
Abstract
Studying phospholipases A2 (PLA2s) is a challenging task since they act on membrane-like aggregated substrates and not on monomeric phospholipids. Multidisciplinary approaches that include hydrogen/deuterium exchange mass spectrometry (DXMS) and computational techniques have been employed with great success in order to address important questions about the mode of interactions of PLA2 enzymes with membranes, phospholipid substrates and inhibitors. Understanding the interactions of PLA2s is crucial since these enzymes are the upstream regulators of the eicosanoid pathway liberating free arachidonic acid (AA) and other polyunsaturated fatty acids (PUFA). The liberation of AA by PLA2 enzymes sets off a cascade of molecular events that involves downstream regulators such as cyclooxygenase (COX) and lipoxygenase (LOX) metabolites leading to inflammation. Aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) work by inhibiting COX, while Zileuton inhibits LOX and both rely on PLA2 enzymes to provide them with AA. That means PLA2 enzymes can potentially also be targeted to diminish inflammation at an earlier point in the process. In this review we describe extensive efforts reported in the past to define the interactions of PLA2 enzymes with membranes, substrate phospholipids and inhibitors using DXMS, molecular docking, and molecular dynamics (MD) simulations.
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29
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Ong WY, Farooqui T, Kokotos G, Farooqui AA. Synthetic and natural inhibitors of phospholipases A2: their importance for understanding and treatment of neurological disorders. ACS Chem Neurosci 2015; 6:814-31. [PMID: 25891385 DOI: 10.1021/acschemneuro.5b00073] [Citation(s) in RCA: 86] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Phospholipases A2 (PLA2) are a diverse group of enzymes that hydrolyze membrane phospholipids into arachidonic acid and lysophospholipids. Arachidonic acid is metabolized to eicosanoids (prostaglandins, leukotrienes, thromboxanes), and lysophospholipids are converted to platelet-activating factors. These lipid mediators play critical roles in the initiation, maintenance, and modulation of neuroinflammation and oxidative stress. Neurological disorders including excitotoxicity; traumatic nerve and brain injury; cerebral ischemia; Alzheimer's disease; Parkinson's disease; multiple sclerosis; experimental allergic encephalitis; pain; depression; bipolar disorder; schizophrenia; and autism are characterized by oxidative stress, inflammatory reactions, alterations in phospholipid metabolism, accumulation of lipid peroxides, and increased activities of brain phospholipase A2 isoforms. Several old and new synthetic inhibitors of PLA2, including fatty acid trifluoromethyl ketones; methyl arachidonyl fluorophosphonate; bromoenol lactone; indole-based inhibitors; pyrrolidine-based inhibitors; amide inhibitors, 2-oxoamides; 1,3-disubstituted propan-2-ones and polyfluoroalkyl ketones as well as phytochemical based PLA2 inhibitors including curcumin, Ginkgo biloba and Centella asiatica extracts have been discovered and used for the treatment of neurological disorders in cell culture and animal model systems. The purpose of this review is to summarize information on selective and potent synthetic inhibitors of PLA2 as well as several PLA2 inhibitors from plants, for treatment of oxidative stress and neuroinflammation associated with the pathogenesis of neurological disorders.
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Affiliation(s)
- Wei-Yi Ong
- Department
of Anatomy, National University of Singapore, Singapore 119260, Singapore
| | - Tahira Farooqui
- Department
of Molecular and Cellular Biochemistry, Ohio State University, Columbus, Ohio 43210, United States
| | - George Kokotos
- Laboratory
of Organic Chemistry, Department of Chemistry, University of Athens, Panepistimiopolis,
Athens 15771, Greece
| | - Akhlaq A. Farooqui
- Department
of Molecular and Cellular Biochemistry, Ohio State University, Columbus, Ohio 43210, United States
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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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Sowole MA, Innes BT, Amunugama M, Litchfield DW, Brandl CJ, Shilton BH, Konermann L. Noncovalent binding of a cyclic peptide inhibitor to the peptidyl-prolyl isomerase Pin1, explored by hydrogen exchange mass spectrometry. CAN J CHEM 2015. [DOI: 10.1139/cjc-2014-0230] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Pin1 is a peptidyl-prolyl isomerase (PPIase) that plays a central role in eukaryotic cell cycle regulation, making this protein an interesting target for cancer therapy. Pin1 exhibits high specificity for substrates where proline is preceded by phosphoserine or phosphothreonine. The protein comprises an N-terminal WW (tryptophan–tryptophan) domain and a C-terminal PPIase domain. The cyclic peptide [CRYPEVEIC] (square brackets are used to denote the cyclic structure) represents a lead compound for a new class of nonphosphorylated Pin1 inhibitors. Unfortunately, it has not been possible thus far to characterize the Pin1–[CRYPEVEIC] complex by X-ray crystallography. Thus, the exact binding mode remains unknown. The current work employs hydrogen/deuterium exchange mass spectrometry for gaining insights into the Pin1–[CRYPEVEIC] interactions. The WW domain shows extensive conformational dynamics, both in the presence and in the absence of ligand. In contrast, profound changes in deuteration kinetics are observed in the PPIase domain after the addition of [CRYPEVEIC]. The secondary structure elements β2, α3, and α4 exhibit markedly reduced deuteration, consistent with their postulated involvement in ligand binding. Unexpectedly, [CRYPEVEIC] destabilizes the range of residues 61–86, a segment that comprises basic side chains that normally interact with the substrate phosphate. This destabilization is likely caused by steric clashes with Y3 or E5 of the inhibitor. Ligand-induced destabilization has previously been reported for a few other proteins, but effects of this type are not very common. Our findings suggest that future crystallization trials on Pin1 variants deleted for residues in the 61–86 range might provide a path towards high-resolution X-ray structures of Pin1 bound to cyclic peptide inhibitors.
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Affiliation(s)
- Modupeola A. Sowole
- Department of Chemistry, The University of Western Ontario, London, ON N6A 5B7, Canada
| | - Brendan T. Innes
- Department of Biochemistry, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, ON N6A 5C1, Canada
| | - Mahasilu Amunugama
- Department of Chemistry, The University of Western Ontario, London, ON N6A 5B7, Canada
| | - David W. Litchfield
- Department of Biochemistry, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, ON N6A 5C1, Canada
| | - Christopher J. Brandl
- Department of Biochemistry, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, ON N6A 5C1, Canada
| | - Brian H. Shilton
- Department of Biochemistry, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, ON N6A 5C1, Canada
| | - Lars Konermann
- Department of Chemistry, The University of Western Ontario, London, ON N6A 5B7, Canada
- Department of Biochemistry, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, ON N6A 5C1, Canada
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32
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Kokotos G, Feuerherm AJ, Barbayianni E, Shah I, Sæther M, Magrioti V, Nguyen T, Constantinou-Kokotou V, Dennis EA, Johansen B. Inhibition of group IVA cytosolic phospholipase A2 by thiazolyl ketones in vitro, ex vivo, and in vivo. J Med Chem 2014; 57:7523-35. [PMID: 25152071 DOI: 10.1021/jm500192s] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Group IVA cytosolic phospholipase A2 (GIVA cPLA2) is the rate-limiting provider of pro-inflammatory mediators in many tissues and is thus an attractive target for the development of novel anti-inflammatory agents. In this work, we present the synthesis of new thiazolyl ketones and the study of their activities in vitro, in cells, and in vivo. Within this series of compounds, methyl 2-(2-(4-octylphenoxy)acetyl)thiazole-4-carboxylate (GK470) was found to be the most potent inhibitor of GIVA cPLA2, exhibiting an XI(50) value of 0.011 mole fraction in a mixed micelle assay and an IC50 of 300 nM in a vesicle assay. In a cellular assay using SW982 fibroblast-like synoviocytes, it suppressed the release of arachidonic acid with an IC50 value of 0.6 μM. In a prophylactic collagen-induced arthritis model, it exhibited an anti-inflammatory effect comparable to the reference drug methotrexate, whereas in a therapeutic model, it showed results comparable to those of the reference drug Enbrel. In both models, it significantly reduced plasma PGE2 levels.
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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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Tomoo T, Nakatsuka T, Katayama T, Hayashi Y, Fujieda Y, Terakawa M, Nagahira K. Design, synthesis, and biological evaluation of 3-(1-Aryl-1H-indol-5-yl)propanoic acids as new indole-based cytosolic phospholipase A2α inhibitors. J Med Chem 2014; 57:7244-62. [PMID: 25102418 DOI: 10.1021/jm500494y] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
This article describes the design, synthesis, and biological evaluation of new indole-based cytosolic phospholipase A2α (cPLA2α, a group IVA phospholipase A2) inhibitors. A screening-hit compound from our library, (E)-3-{4-[(4-chlorophenyl)thio]-3-nitrophenyl}acrylic acid (5), was used to design a class of 3-(1-aryl-1H-indol-5-yl)propanoic acids as new small molecule inhibitors. The resultant structure-activity relationships studied using the isolated enzyme and by cell-based assays revealed that the 1-(p-O-substituted)phenyl, 3-phenylethyl, and 5-propanoic acid groups on the indole core are essential for good inhibitory activity against cPLA2α. Optimization of the p-substituents on the N1 phenyl group led to the discovery of 56n (ASB14780), which was shown to be a potent inhibitor of cPLA2α via enzyme assay, cell-based assay, and guinea pig and human whole-blood assays. It displayed oral efficacy toward mice tetradecanoyl phorbol acetate-induced ear edema and guinea pig ovalbumin-induced asthma models.
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Affiliation(s)
- Toshiyuki Tomoo
- Faculty of Pharmaceutical Chemistry, ‡R&D Administration, §Exploratory Technology, ∥Drug Discovery Technology, and ⊥Pharmacology I, Asubio Pharma Co., Ltd. , 6-4-3 Minatojima-Minamimachi, Chuo-ku, Kobe, Hyogo 650-0047, Japan
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Sowole MA, Konermann L. Effects of Protein–Ligand Interactions on Hydrogen/Deuterium Exchange Kinetics: Canonical and Noncanonical Scenarios. Anal Chem 2014; 86:6715-22. [DOI: 10.1021/ac501849n] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- Modupeola A. Sowole
- Department
of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Lars Konermann
- Department
of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
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Konermann L, Rodriguez AD, Sowole MA. Type 1 and Type 2 scenarios in hydrogen exchange mass spectrometry studies on protein–ligand complexes. Analyst 2014; 139:6078-87. [DOI: 10.1039/c4an01307g] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Ligand binding to a protein can elicit a wide range of responses when studied by HDX mass spectrometry.
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Affiliation(s)
- Lars Konermann
- Department of Chemistry
- The University of Western Ontario
- London, Canada
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36
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Bucher D, Hsu YH, Mouchlis VD, Dennis EA, McCammon JA. Insertion of the Ca²⁺-independent phospholipase A₂ into a phospholipid bilayer via coarse-grained and atomistic molecular dynamics simulations. PLoS Comput Biol 2013; 9:e1003156. [PMID: 23935474 PMCID: PMC3723492 DOI: 10.1371/journal.pcbi.1003156] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2013] [Accepted: 06/11/2013] [Indexed: 01/19/2023] Open
Abstract
Group VI Ca²⁺-independent phospholipase A₂ (iPLA₂) is a water-soluble enzyme that is active when associated with phospholipid membranes. Despite its clear pharmaceutical relevance, no X-ray or NMR structural information is currently available for the iPLA₂ or its membrane complex. In this paper, we combine homology modeling with coarse-grained (CG) and all-atom (AA) molecular dynamics (MD) simulations to build structural models of iPLA₂ in association with a phospholipid bilayer. CG-MD simulations of the membrane insertion process were employed to provide a starting point for an atomistic description. Six AA-MD simulations were then conducted for 60 ns, starting from different initial CG structures, to refine the membrane complex. The resulting structures are shown to be consistent with each other and with deuterium exchange mass spectrometry (DXMS) experiments, suggesting that our approach is suitable for the modeling of iPLA₂ at the membrane surface. The models show that an anchoring region (residues 710-724) forms an amphipathic helix that is stabilized by the membrane. In future studies, the proposed iPLA₂ models should provide a structural basis for understanding the mechanisms of lipid extraction and drug-inhibition. In addition, the dual-resolution approach discussed here should provide the means for the future exploration of the impact of lipid diversity and sequence mutations on the activity of iPLA₂ and related enzymes.
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Affiliation(s)
- Denis Bucher
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California, United States of America.
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Hsu YH, Bucher D, Cao J, Li S, Yang SW, Kokotos G, Woods VL, McCammon JA, Dennis EA. Fluoroketone inhibition of Ca(2+)-independent phospholipase A2 through binding pocket association defined by hydrogen/deuterium exchange and molecular dynamics. J Am Chem Soc 2013; 135:1330-7. [PMID: 23256506 PMCID: PMC3561773 DOI: 10.1021/ja306490g] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
![]()
The mechanism of inhibition of group VIA Ca2+-independent
phospholipase A2 (iPLA2) by fluoroketone (FK)
ligands is examined by a combination of deuterium exchange mass spectrometry
(DXMS) and molecular dynamics (MD). Models for iPLA2 were
built by homology with the known structure of patatin and equilibrated
by extensive MD simulations. Empty pockets were identified during
the simulations and studied for their ability to accommodate FK inhibitors.
Ligand docking techniques showed that the potent inhibitor 1,1,1,3-tetrafluoro-7-phenylheptan-2-one
(PHFK) forms favorable interactions inside an active-site pocket,
where it blocks the entrance of phospholipid substrates. The polar
fluoroketone headgroup is stabilized by hydrogen bonds with residues
Gly486, Gly487, and Ser519. The nonpolar aliphatic chain and aromatic
group are stabilized by hydrophobic contacts with Met544, Val548,
Phe549, Leu560, and Ala640. The binding mode is supported by DXMS
experiments showing an important decrease of deuteration in the contact
regions in the presence of the inhibitor. The discovery of the precise
binding mode of FK ligands to the iPLA2 should greatly
improve our ability to design new inhibitors with higher potency and
selectivity.
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Affiliation(s)
- Yuan-Hao Hsu
- Department of Pharmacology, University of California, San Diego, La Jolla, California 92093-0601, USA.
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38
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Magrioti V, Kokotos G. Phospholipase A2inhibitors for the treatment of inflammatory diseases: a patent review (2010 – present). Expert Opin Ther Pat 2013; 23:333-44. [DOI: 10.1517/13543776.2013.754425] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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Cao J, Hsu YH, Li S, Woods VL, Dennis EA. Structural basis of specific interactions of Lp-PLA2 with HDL revealed by hydrogen deuterium exchange mass spectrometry. J Lipid Res 2013; 54:127-33. [PMID: 23089916 PMCID: PMC3520519 DOI: 10.1194/jlr.m030221] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2012] [Revised: 09/26/2012] [Indexed: 12/23/2022] Open
Abstract
Lipoprotein-associated phospholipase A(2) (Lp-PLA(2)), specifically Group VIIA PLA(2), is a member of the phospholipase A(2) superfamily and is found mainly associated with LDL and HDL in human plasma. Lp-PLA(2) is considered as a risk factor, a potential biomarker, a target for therapy in the treatment of cardiovascular disease, and evidence suggests that the level of Lp-PLA(2) in plasma is associated with the risk of future cardiovascular and stroke events. The differential location of the enzyme in LDL/HDL lipoproteins has been suggested to affect Lp-PLA(2) function and/or its physiological role and an abnormal distribution of the enzyme may correlate with diseases. Although a mutagenesis study suggested that a surface helix (residues 362-369) mediates the association between Lp-PLA(2) and HDL, the molecular details and mechanism of association has remained unknown. We have now employed hydrogen deuterium exchange mass spectrometry to characterize the interaction between recombinant human Lp-PLA(2) and human HDL. We have found that specific residues 113-120, 192-204, and 360-368 likely mediate HDL binding. In a previous study, we showed that residues 113-120 are important for Lp-PLA(2)-liposome interactions. We now find that residues 192-204 show a decreased deuteration level when Lp-PLA(2) is exposed to apoA-I, but not apoA-II, the most abundant apoproteins in HDL, and additionally, residues 360-368 are only affected by HDL.The results suggest that apoA-I and phospholipid membranes play crucial roles in Lp-PLA(2) localization to HDL.
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Affiliation(s)
- Jian Cao
- Departments of Chemistry and Biochemistry and Pharmacology and
| | - Yuan-Hao Hsu
- Departments of Chemistry and Biochemistry and Pharmacology and
| | - Sheng Li
- Department of Medicine and Biomedical Sciences Graduate Program, School of Medicine, University of California, San Diego, La Jolla, CA 92093-0601
| | - Virgil L. Woods
- Department of Medicine and Biomedical Sciences Graduate Program, School of Medicine, University of California, San Diego, La Jolla, CA 92093-0601
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40
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Cao J, Burke JE, Dennis EA. Using hydrogen/deuterium exchange mass spectrometry to define the specific interactions of the phospholipase A2 superfamily with lipid substrates, inhibitors, and membranes. J Biol Chem 2012; 288:1806-13. [PMID: 23209293 DOI: 10.1074/jbc.r112.421909] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The phospholipase A(2) (PLA(2)) superfamily consists of 16 groups and many subgroups and constitutes a diverse set of enzymes that have a common catalytic activity due to convergent evolution. However, different PLA(2) types have unique three-dimensional structures and catalytic residues as well as specific tissue localization and distinct biological functions. Understanding how the different PLA(2) enzymes associate with phospholipid membranes, specific phospholipid substrate molecules, and inhibitors on a molecular basis has advanced in recent years due to the introduction of hydrogen/deuterium exchange mass spectrometry. Its theory, practical considerations, and application to understanding PLA(2)/membrane interactions are addressed.
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Affiliation(s)
- Jian Cao
- Department of Chemistry and Biochemistry and Department of Pharmacology, University of California, San Diego, La Jolla, California 92093-0601, USA
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41
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Brock A. Fragmentation hydrogen exchange mass spectrometry: A review of methodology and applications. Protein Expr Purif 2012; 84:19-37. [DOI: 10.1016/j.pep.2012.04.009] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Accepted: 04/13/2012] [Indexed: 01/19/2023]
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Potent and selective 2-oxoamide inhibitors of phospholipases A2 as novel medicinal agents for the treatment of inflammatory diseases. PURE APPL CHEM 2012. [DOI: 10.1351/pac-con-11-10-32] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Phospholipases A2 (PLA2s) are enzymes that are capable of catalyzing the hydrolysis of the sn-2 ester bond of glycerophospholipids, releasing free fatty acids, including arachidonic acid (AA), and lysophospholipids. Both products are precursor signaling molecules involved in inflammation. Among the various PLA2s, cytosolic GIVA cPLA2 is considered a major target for inflammatory diseases, while secreted GIIA sPLA2 is involved in cardiovascular diseases. We have developed lipophilic 2-oxoamides based on (S)-γ- or δ-amino acids as potent and selective inhibitors of GIVA cPLA2, which present interesting in vivo anti-inflammatory activity. 2-Oxoamides based on natural α-amino acids are selective inhibitors of GIIA sPLA2. The mode of binding of 2-oxoamides with either GIVA cPLA2 or GIIA sPLA2 has been studied by various techniques.
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43
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Zizza P, Iurisci C, Bonazzi M, Cossart P, Leslie CC, Corda D, Mariggiò S. Phospholipase A2IVα regulates phagocytosis independent of its enzymatic activity. J Biol Chem 2012; 287:16849-59. [PMID: 22393044 DOI: 10.1074/jbc.m111.309419] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Group IVα phospholipase A(2) (PLA(2)IVα) is a lipolytic enzyme that catalyzes the hydrolysis of membrane phospholipids to generate precursors of potent inflammatory lipid mediators. Here, the role of PLA(2)IVα in Fc receptor (FcR)-mediated phagocytosis was investigated, demonstrating that PLA(2)IVα is selectively activated upon FcR-mediated phagocytosis in macrophages and that it rapidly translocates to the site of the nascent phagosome. Moreover, pharmacological inhibition of PLA(2)IVα by pyrrophenone reduces particle internalization by up to 50%. In parallel, fibroblasts from PLA(2)IVα knock-out mice overexpressing FcγRIIA and able to internalize IgG-opsonized beads show 50% lower phagocytosis, compared with wild-type cells, and transfection of PLA(2)IVα fully recovers this impaired function. Interestingly, transfection of the catalytically inactive deleted PLA(2)IVα mutant (PLA(2)IVα(1-525)) and point mutant (PLA(2)IVα-S228C) also promotes recovery of this impaired function. Finally, transfection of the PLA(2)IVα C2 domain (which is directly involved in PLA(2)IVα membrane binding), but not of PLA(2)IVα-D43N (which cannot bind to membranes), rescues FcR-mediated phagocytosis. These data unveil a new mechanism of action for PLA(2)IVα, which demonstrates that the membrane binding, and not the enzymatic activity, is required for PLA(2)IVα modulation of FcR-mediated phagocytosis.
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Affiliation(s)
- Pasquale Zizza
- Institute of Protein Biochemistry, National Research Council, Via Pietro Castellino 111, 80131 Naples, Italy
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44
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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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45
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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: 804] [Impact Index Per Article: 61.8] [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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46
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Abstract
Lipidomics, a major part of metabolomics, constitutes the detailed analysis and global characterization, both spatial and temporal, of the structure and function of lipids (the lipidome) within a living system. As with proteomics, mass spectrometry has earned a central analytical role in lipidomics, and this role will continue to grow with technological developments. Currently, there exist two mass spectrometry-based lipidomics approaches, one based on a division of lipids into categories and classes prior to analysis, the "comprehensive lipidomics analysis by separation simplification" (CLASS), and the other in which all lipid species are analyzed together without prior separation, shotgun. In exploring the lipidome of various living systems, novel lipids are being discovered, and mass spectrometry is helping characterize their chemical structure. Deuterium exchange mass spectrometry (DXMS) is being used to investigate the association of lipids and membranes with proteins and enzymes, and imaging mass spectrometry (IMS) is being applied to the in situ analysis of lipids in tissues.
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Affiliation(s)
- Richard Harkewicz
- Department of Chemistry and Biochemistry and Department of Pharmacology, School of Medicine, University of California at San Diego, La Jolla, California 92093-0601, USA.
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Cao J, Hsu YH, Li S, Woods VL, Dennis EA. Lipoprotein-associated phospholipase A(2) interacts with phospholipid vesicles via a surface-disposed hydrophobic α-helix. Biochemistry 2011; 50:5314-21. [PMID: 21553808 DOI: 10.1021/bi101916w] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) plays important roles in both the inhibition and promotion of inflammation in human disease. It catalyzes the hydrolytic inactivation of plasma platelet activating factor (PAF) and is also known as PAF acetylhydrolase. High levels of PAF are implicated in a variety of inflammatory diseases such as asthma, necrotizing enterocolitis, and sepsis. Lp-PLA(2) also associates with lipoproteins in human plasma where it hydrolyzes oxidized phospholipids to produce pro-inflammatory lipid mediators that can promote inflammation and the development of atherosclerosis. Lp-PLA(2) plasma levels have recently been identified as a biomarker of vascular inflammation, atherosclerotic vulnerability, and future cardiovascular events. The enzyme is thus a prominent target for the development of inflammation and atherosclerosis-modulating therapeutics. While the crystallographically determined structure of the enzyme is known, the enzyme's mechanism of interaction with PAF and the function-modulating lipids in lipoproteins is unknown. We have employed peptide amide hydrogen-deuterium exchange mass spectrometry (DXMS) to characterize the association of Lp-PLA(2) with dimyristoylphosphatidylcholine (DMPC) vesicles and found that specific residues 113-120 in one of the enzyme's surface-disposed hydrophobic α-helices likely mediate liposome binding.
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Affiliation(s)
- Jian Cao
- Department of Chemistry and Biochemistry and Pharmacology, University of California, La Jolla, CA 92093-0601, USA
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Changes in PLA2 activity after interacting with anti-inflammatory drugs and model membranes: evidence for the involvement of tryptophan residues. Chem Phys Lipids 2011; 164:292-9. [DOI: 10.1016/j.chemphyslip.2011.03.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2010] [Revised: 03/09/2011] [Accepted: 03/11/2011] [Indexed: 11/23/2022]
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Stanford SM, Krishnamurthy D, Falk MD, Messina R, Debnath B, Li S, Liu T, Kazemi R, Dahl R, He Y, Yu X, Chan AC, Zhang ZY, Barrios AM, Woods VL, Neamati N, Bottini N. Discovery of a novel series of inhibitors of lymphoid tyrosine phosphatase with activity in human T cells. J Med Chem 2011; 54:1640-54. [PMID: 21341673 PMCID: PMC3086468 DOI: 10.1021/jm101202j] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The lymphoid tyrosine phosphatase LYP, encoded by the PTPN22 gene, is a critical regulator of signaling in T cells and recently emerged as a candidate target for therapy of autoimmune diseases. Here, by library screening, we identified a series of noncompetitive inhibitors of LYP that showed activity in primary T cells. Kinetic analysis confirmed that binding of the compounds to the phosphatase is nonmutually exclusive with respect to a known bidentate competitive inhibitor. The mechanism of action of the lead inhibitor compound 4e was studied by a combination of hydrogen/deuterium-exchange mass spectrometry and molecular modeling. The results suggest that the inhibitor interacts critically with a hydrophobic patch located outside the active site of the phosphatase. Targeting of secondary allosteric sites is viewed as a promising yet unexplored approach to develop pharmacological inhibitors of protein tyrosine phosphatases. Our novel scaffold could be a starting point to attempt development of "nonactive site" anti-LYP pharmacological agents.
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Affiliation(s)
- Stephanie M. Stanford
- Institute for Genetic Medicine, University of Southern California, Los Angeles, California 90033, United States
- Division of Cell Biology, La Jolla Institute for Allergy and Immunology, La Jolla, California 92037, United States
| | - Divya Krishnamurthy
- Institute for Genetic Medicine, University of Southern California, Los Angeles, California 90033, United States
- Department of Medicinal Chemistry, University of Utah, Salt Lake City, Utah 84112, United States
| | - Matthew D. Falk
- Division of Cell Biology, La Jolla Institute for Allergy and Immunology, La Jolla, California 92037, United States
| | - Rossella Messina
- Division of Cell Biology, La Jolla Institute for Allergy and Immunology, La Jolla, California 92037, United States
| | - Bikash Debnath
- Department of Pharmacology and Pharmaceutical Sciences, University of Southern California, Los Angeles, California 90033, United States
| | - Sheng Li
- Department of Medicine, University of California San Diego, La Jolla, California 92093, United States
| | - Tong Liu
- Department of Medicine, University of California San Diego, La Jolla, California 92093, United States
| | - Roza Kazemi
- Department of Pharmacology and Pharmaceutical Sciences, University of Southern California, Los Angeles, California 90033, United States
| | - Russell Dahl
- CPCCG, Sanford-Burnham Medical Research Institute, La Jolla, California 92037, United States
| | - Yantao He
- Department of Biochemistry and Molecular Biology, Indiana University, Indianapolis, Indiana 46202, United States
| | - Xiao Yu
- Department of Biochemistry and Molecular Biology, Indiana University, Indianapolis, Indiana 46202, United States
| | - Andrew C. Chan
- Department of Immunology, Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Zhong-Yin Zhang
- Department of Biochemistry and Molecular Biology, Indiana University, Indianapolis, Indiana 46202, United States
| | - Amy M. Barrios
- Department of Medicinal Chemistry, University of Utah, Salt Lake City, Utah 84112, United States
| | - Virgil L. Woods
- Department of Medicine, University of California San Diego, La Jolla, California 92093, United States
| | - Nouri Neamati
- Department of Pharmacology and Pharmaceutical Sciences, University of Southern California, Los Angeles, California 90033, United States
| | - Nunzio Bottini
- Institute for Genetic Medicine, University of Southern California, Los Angeles, California 90033, United States
- Division of Cell Biology, La Jolla Institute for Allergy and Immunology, La Jolla, California 92037, United States
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50
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Li S, Tsalkova T, White MA, Mei FC, Liu T, Wang D, Woods VL, Cheng X. Mechanism of intracellular cAMP sensor Epac2 activation: cAMP-induced conformational changes identified by amide hydrogen/deuterium exchange mass spectrometry (DXMS). J Biol Chem 2011; 286:17889-97. [PMID: 21454623 DOI: 10.1074/jbc.m111.224535] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Epac2, a guanine nucleotide exchange factor, regulates a wide variety of intracellular processes in response to second messenger cAMP. In this study, we have used peptide amide hydrogen/deuterium exchange mass spectrometry to probe the solution structural and conformational dynamics of full-length Epac2 in the presence and absence of cAMP. The results support a mechanism in which cAMP-induced Epac2 activation is mediated by a major hinge motion centered on the C terminus of the second cAMP binding domain. This conformational change realigns the regulatory components of Epac2 away from the catalytic core, making the later available for effector binding. Furthermore, the interface between the first and second cAMP binding domains is highly dynamic, providing an explanation of how cAMP gains access to the ligand binding sites that, in the crystal structure, are seen to be mutually occluded by the other cAMP binding domain. Moreover, cAMP also induces conformational changes at the ionic latch/hairpin structure, which is directly involved in RAP1 binding. These results suggest that in addition to relieving the steric hindrance imposed upon the catalytic lobe by the regulatory lobe, cAMP may also be an allosteric modulator directly affecting the interaction between Epac2 and RAP1. Finally, cAMP binding also induces significant conformational changes in the dishevelled/Egl/pleckstrin (DEP) domain, a conserved structural motif that, although missing from the active Epac2 crystal structure, is important for Epac subcellular targeting and in vivo functions.
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Affiliation(s)
- Sheng Li
- Department of Medicine and Biomedical Sciences Graduate program, University of California, San Diego, La Jolla, California 92093-0656, USA
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