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Wang C, Li Y, Lin Y, Wang Y, Chen Z, Zhu L, Wang J. In situ enzymatic hydrolysis characterisation of phospholipid using 1H NMR in a heterogeneous environment. Lebensm Wiss Technol 2023. [DOI: 10.1016/j.lwt.2023.114592] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
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2
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Alekseeva AS, Volynsky PE, Krylov NA, Chernikov VP, Vodovozova EL, Boldyrev IA. Phospholipase A2 way to hydrolysis: Dint formation, hydrophobic mismatch, and lipid exclusion. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1863:183481. [PMID: 33002451 DOI: 10.1016/j.bbamem.2020.183481] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 08/23/2020] [Accepted: 09/21/2020] [Indexed: 01/05/2023]
Abstract
Phospholipase A2 (PLA2) exerts a wide range of biological effects and attracts a lot of attention of researchers. Two sites are involved in manifestation of PLA2 enzymatic activity: catalytic site responsible for substrate binding and fatty acid cleavage from the sn-2 position of a glycerophospholipid, and interface binding site (IBS) responsible for the protein binding to lipid membrane. IBS is formed by positively charged and hydrophobic amino acids on the outer surface of the protein molecule. Understanding the mechanism of PLA2 interaction with the lipid membrane is the most challenging step in biochemistry of this enzyme. We used a combination of experimental and computer simulation techniques to clarify molecular details of bee venom PLA2 interaction with lipid bilayers formed by palmitoyloleoylphosphatidylcholine or dipalmitoylphosphatidylcholine. We found that after initial enzyme contact with the membrane, a network of hydrogen bonds was formed. This led to deformation of the interacting leaflet and dint formation. The bilayer response to the deformation depended on its phase state. In a gel-phase bilayer, diffusion of lipids is restricted therefore chain melting occurred in both leaflets of the bilayer. In the case of a fluid-phase bilayer, lateral diffusion is possible, and lipid polar head groups were excluded from the contact area. As a result, the bilayer became thinner and a large hydrophobic area was formed. We assume that relative ability of a bilayer to come through lipid redistribution process defines the rate of initial stages of the catalysis.
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Affiliation(s)
- Anna S Alekseeva
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya st., 16/10, 117997 Moscow, Russia
| | - Pavel E Volynsky
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya st., 16/10, 117997 Moscow, Russia
| | - Nikolay A Krylov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya st., 16/10, 117997 Moscow, Russia
| | - Valery P Chernikov
- Scientific Research Institute of Human Morphology, Tsyurupy st., 3, 117418 Moscow, Russia
| | - Elena L Vodovozova
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya st., 16/10, 117997 Moscow, Russia
| | - Ivan A Boldyrev
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya st., 16/10, 117997 Moscow, Russia.
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3
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Zhang P, Villanueva V, Kalkowski J, Liu C, Donovan AJ, Bu W, Schlossman ML, Lin B, Liu Y. Molecular interactions of phospholipid monolayers with a model phospholipase. SOFT MATTER 2019; 15:4068-4077. [PMID: 30958491 DOI: 10.1039/c8sm01154k] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The intrinsic overexpression of secretory phospholipase A2 (sPLA2) in various pro-inflammatory diseases and cancers has the potential to be exploited as a therapeutic strategy for diagnostics and treatment. To explore this potential and advance our knowledge of the role of sPLA2 in related diseases, it is necessary to systematically investigate the molecular interaction of the enzyme with lipids. By employing a Langmuir trough integrated with X-ray reflectivity and grazing incidence X-ray diffraction techniques, this study examined the molecular packing structure of 1,2-palmitoyl-sn-glycero-3-phosphocholine (DPPC) films before and after enzyme adsorption and enzyme-catalyzed degradation. Molecular interaction of sPLA2 (from bee venom) with the DPPC monolayer exhibited Ca2+ dependence. DPPC molecules at the interface without Ca2+ retained a monolayer organization; upon adsorption of sPLA2 to the monolayer the packing became tighter. In contrast, sPLA2-catalyzed degradation of DPPC occurred in the presence of Ca2+, leading to disruption of the ordered monolayer structure of DPPC. The interfacial film became a mixture of highly ordered multilayer domains of palmitic acid (PA) and loosely packed monolayer phase of 1-palmitoyl-2-hydroxy-sn-glycero-3-phosphocholine (lysoPC) that potentially contained the remaining un-degraded DPPC. The redistribution of lipid degradation products into the third dimension, which produced multilayer PA domains, damaged the structural integrity of the original lipid layer and may explain the bursting of liposomes observed in other studies after a latency period of mixing liposomes with sPLA2. A quantitative understanding of the lipid packing and lipid-enzyme interaction provides an intuitive means of designing and optimizing lipid-related drug delivery systems.
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Affiliation(s)
- Pin Zhang
- Department of Chemical Engineering, University of Illinois at Chicago, Chicago, IL 60607, USA.
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4
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Wadsäter M, Barauskas J, Tiberg F, Nylander T. The lipolytic degradation of highly structured cubic micellar nanoparticles of soy phosphatidylcholine and glycerol dioleate by phospholipase A 2 and triacylglycerol lipase. Chem Phys Lipids 2018; 211:86-92. [PMID: 29132829 DOI: 10.1016/j.chemphyslip.2017.11.011] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2017] [Revised: 10/05/2017] [Accepted: 11/09/2017] [Indexed: 11/23/2022]
Abstract
The effects of different lipolytic enzymes on the structure of lipid liquid crystalline nano-particles (LCNP) have been investigated by cryogenic transmission electron microscopy (cryo-TEM) and synchrotron small angle X-ray diffraction (SAXD). Here we used highly structured cubic micellar (Fd3m) nanoparticles of 50/50 (wt%/wt%) soy phosphatidyl choline (SPC)/glycerol dioleate (GDO) as substrate. Two types of lipolytic enzymes were used, phospholipase A2 (PLA2) that catalyses degradation of the phospholipid component, SPC, and porcine pancreatic triacylglycerol lipase (TGL) that facilitate the hydrolysis of the diglyceride, GDO. Evolution of the structure was found to be very different and linked to specificity of the two types of enzymes. PLA2, which hydrolyses the lamellar forming component, SPC, induces a reversed micellar lipid phase, while TGL which hydrolysis the reverse phase forming compound, GDO, induces a lamellar phase.
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Affiliation(s)
- Maria Wadsäter
- Physical Chemistry, Department of Chemistry, Lund University, P.O. Box 124, SE-22100, Lund, Sweden.
| | - Justas Barauskas
- Camurus AB, Ideon Science Park, Gamma Building, Sölvegatan 41, SE-22379, Lund, Sweden(1); Biomedical Science, Faculty of Health and Society, Malmö University, SE-20506, Malmö, Sweden.
| | - Fredrik Tiberg
- Physical Chemistry, Department of Chemistry, Lund University, P.O. Box 124, SE-22100, Lund, Sweden; Camurus AB, Ideon Science Park, Gamma Building, Sölvegatan 41, SE-22379, Lund, Sweden(1)
| | - Tommy Nylander
- Physical Chemistry, Department of Chemistry, Lund University, P.O. Box 124, SE-22100, Lund, Sweden.
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5
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Damodaran S. Beyond the hydrophobic effect: Critical function of water at biological phase boundaries--A hypothesis. Adv Colloid Interface Sci 2015; 221:22-33. [PMID: 25888225 DOI: 10.1016/j.cis.2015.03.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Revised: 03/24/2015] [Accepted: 03/25/2015] [Indexed: 11/29/2022]
Abstract
Many life-sustaining processes in living cells occur at the membrane-water interface. The pertinent questions that need to be asked are what is the evolutionary reason for biology to choose the membrane-water interface as the site for performing and/or controlling crucial biological reactions and what is the key physical principle that is singular to the membrane-water interface that biology exploits for regulating metabolic processes in cells? In this review, a hypothesis is developed, which espouses that cells control activities of membrane-bound enzymes and receptor activated processes via manipulating the thermodynamic activity of water at the membrane-water interfacial region. In support of this hypothesis, first we establish that the surface pressure of a lipid monolayer is a direct measure of a reduction in the thermodynamic activity of interfacial water. Second, we show that the surface pressure-dependent activation/inactivation of interfacial enzymes is fundamentally related to their dependence on interfacial water activity. We extend this argument to infer that cells might manipulate activities of membrane-associated biological processes via manipulating the activity of interfacial water via localized compression or expansion of the interface. In this paper, we critically analyze literature data on mechano-activation of large pore ion channels in Escherichia coli spheroplasts and G-proteins in reconstituted lipid vesicles, and show that these pressure-induced activation processes are fundamentally and quantitatively related to changes in the thermodynamic state of interfacial water, caused by mechanical stretching of the bilayer.
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Affiliation(s)
- Srinivasan Damodaran
- University of Wisconsin-Madison, Department of Food Science, 1605 Linden Drive, Madison, WI 53706, United States.
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6
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Singh J, Lai AJ, Alaee Y, Ranganathan R. Partitioning of lysolipids, fatty acids and their mixtures in aqueous lipid bilayers: solute concentration/composition effects. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1838:348-54. [PMID: 24099742 DOI: 10.1016/j.bbamem.2013.09.017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Revised: 09/14/2013] [Accepted: 09/25/2013] [Indexed: 11/19/2022]
Abstract
Distributions of lysopalmitoylphosphatidylcholine (LPPC), palmitic acid (PA) and their 1:1 mixtures between water and dipalmitoylphosphatidylcholine (DPPC) bilayer were determined using a fluorescence probe that selectively detects only the solutes in water. Water solute concentrations were obtained at each of several lipid concentrations. Dynamic Light Scattering experiments confirmed that the lipid/solute aggregates were vesicles in the concentration range investigated. Lipid concentration dependence of the solute component in water was fit to a thermodynamic model of solute distribution between two coexisting solvents. Water/bilayer partition coefficient and the free energy of transfer, for each of these solutes were determined from the fit. Main findings are: (1) Water/bilayer partition coefficient of solute is greater for 2 to 10% solute mole fraction than for 0 to 2%, signaling solute induced bilayer perturbation that increases bilayer solubility, beginning at 2% solute mole fraction. (2) Partition coefficients are in the order LPPC<PA<LPPC+PA at 37°C and LPPC+PA≤LPPC<PA at 50°C. This signifies synergism toward increased solute solubility in the bilayer-gel phase and lack of it in the bilayer-liquid phase when LPPC and PA are present together. Implications of the solute concentration/composition and bilayer phase dependences of the partition coefficients to the reported solute induced enhancements in transmembrane permeability are discussed.
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Affiliation(s)
- Jasmeet Singh
- Department of Physics and the Center for Supramolecular Studies, California State University Northridge, CA 91330-8268, USA
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7
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Oude Blenke E, Mastrobattista E, Schiffelers RM. Strategies for triggered drug release from tumor targeted liposomes. Expert Opin Drug Deliv 2013; 10:1399-410. [DOI: 10.1517/17425247.2013.805742] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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8
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Wu H, Yu L, Tong Y, Ge A, Yau S, Osawa M, Ye S. Enzyme-catalyzed hydrolysis of the supported phospholipid bilayers studied by atomic force microscopy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1828:642-51. [DOI: 10.1016/j.bbamem.2012.09.010] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2012] [Revised: 09/06/2012] [Accepted: 09/07/2012] [Indexed: 01/17/2023]
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9
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Zhdanov VP, Höök F. Kinetics of the enzyme–vesicle interaction including the formation of rafts and membrane strain. Biophys Chem 2012; 170:17-24. [DOI: 10.1016/j.bpc.2012.06.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Revised: 06/19/2012] [Accepted: 06/28/2012] [Indexed: 11/29/2022]
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10
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Charalambous K, Booth PJ, Woscholski R, Seddon JM, Templer RH, Law RV, Barter LMC, Ces O. Engineering de novo membrane-mediated protein-protein communication networks. J Am Chem Soc 2012; 134:5746-9. [PMID: 22428921 DOI: 10.1021/ja300523q] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Mechanical properties of biological membranes are known to regulate membrane protein function. Despite this, current models of protein communication typically feature only direct protein-protein or protein-small molecule interactions. Here we show for the first time that, by harnessing nanoscale mechanical energy within biological membranes, it is possible to promote controlled communication between proteins. By coupling lipid-protein modules and matching their response to the mechanical properties of the membrane, we have shown that the action of phospholipase A(2) on acyl-based phospholipids triggers the opening of the mechanosensitive channel, MscL, by generating membrane asymmetry. Our findings confirm that the global physical properties of biological membranes can act as information pathways between proteins, a novel mechanism of membrane-mediated protein-protein communication that has important implications for (i) the underlying structure of signaling pathways, (ii) our understanding of in vivo communication networks, and (iii) the generation of building blocks for artificial protein networks.
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Affiliation(s)
- Kalypso Charalambous
- Institute of Chemical Biology and Department of Chemistry, Imperial College London, Exhibition Road, London SW7 2AZ, UK.
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11
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Leidy C, Ocampo J, Duelund L, Mouritsen OG, Jørgensen K, Peters GH. Membrane restructuring by phospholipase A2 is regulated by the presence of lipid domains. Biophys J 2011; 101:90-9. [PMID: 21723818 DOI: 10.1016/j.bpj.2011.02.062] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2010] [Revised: 02/22/2011] [Accepted: 02/24/2011] [Indexed: 12/13/2022] Open
Abstract
Secretory phospholipase A(2) (sPLA(2)) catalyzes the hydrolysis of glycerophospholipids. This enzyme is sensitive to membrane structure, and its activity has been shown to increase in the presence of liquid-crystalline/gel (L(α)/L(β)) lipid domains. In this work, we explore whether lipid domains can also direct the activity of the enzyme by inducing hydrolysis of certain lipid components due to preferential activity of the enzyme toward lipid domains susceptible to sPLA(2). Specifically, we show that the presence of L(α)/L(β) and L(α)/P(β') phase coexistence in a 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC)/1,2 distearoyl-sn-glycero-3-phosphocholine (DSPC) system results in the preferential hydrolysis of the shorter-chained lipid component in the mixture, leading to an enrichment in the longer-chained component. The restructuring process is monitored by atomic force microscopy on supported single and double bilayers formed by vesicle fusion. We observe that during preferential hydrolysis of the DMPC-rich L(α) regions, the L(β) and P(β') regions grow and reseal, maintaining membrane integrity. This result indicates that a sharp reorganization of the membrane structure can occur during sPLA(2) hydrolysis without necessarily destroying the membrane. We confirm by high-performance liquid chromatography the preferential hydrolysis of DMPC within the phase coexistence region of the DMPC/DSPC phase diagram, showing that this preferential hydrolysis is accentuated close to the solidus phase boundary. Differential scanning calorimetry results show that this preferential hydrolysis in the presence of lipid domains leads to a membrane system with a higher-temperature melting profile due to enrichment in DSPC. Together, these results show that the presence of lipid domains can induce specificity in the hydrolytic activity of the enzyme, resulting in marked differences in the physical properties of the membrane end-product.
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Affiliation(s)
- Chad Leidy
- Department of Physics, Universidad de los Andes, Bogotá, Colombia.
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12
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Mahalka AK, Code C, Rezaijahromi B, Kirkegaard T, Jäättelä M, Kinnunen PK. Activation of phospholipase A2 by Hsp70 in vitro. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:2569-72. [DOI: 10.1016/j.bbamem.2011.06.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2011] [Revised: 05/12/2011] [Accepted: 06/02/2011] [Indexed: 11/16/2022]
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13
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Lokajová J, Laine J, Puukilainen E, Ritala M, Holopainen JM, Wiedmer SK. Liposomes for entrapping local anesthetics: a liposome electrokinetic chromatographic study. Electrophoresis 2010; 31:1540-9. [PMID: 20358540 DOI: 10.1002/elps.200900562] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Bupivacaine is a lipophilic, long-acting, amide class local anesthetic commonly used in clinical practice to provide local anesthesia during surgical procedures. Several cases of accidental overdose with cardiac arrest and death have been reported since bupivacaine was introduced to human use. Recent case reports have suggested that Intralipid (Fresenius Kabi) is an effective therapy for cardiac toxicity from high systemic concentrations of, e.g. bupivacaine, even though the mechanism behind the interaction is not fully clear yet. Our long-term aim is to develop a sensitive, efficient, and non-harmful lipid-based formulation to specifically trap harmful substances in vivo. In this study, the in vitro interaction of local anesthetics (bupivacaine, prilocaine, and lidocaine) with Intralipid or lipid vesicles containing phosphatidylglycerol, phosphatidylcholine, cardiolipin, cholesterol, and N-palmitoyl-D-erythro-sphingosine (ceramide) was determined by liposome electrokinetic chromatography. The interactions were evaluated by calculating the retention factors and distribution constants. Atomic force microscopy measurements were carried out to confirm that the interaction mechanism was solely due to interactions between the analytes and the moving pseudostationary phase and not by interactions with a stationary lipid phase adsorbed to the fused-silica wall. The heterogeneity of the liposomes was also studied by atomic force microscopy. The liposome electrokinetic chromatography results demonstrate that there is higher interaction between the drugs and negatively charged liposome dispersion than with the commercial Intralipid dispersion.
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Affiliation(s)
- Jana Lokajová
- Laboratory of Analytical Chemistry, Department of Chemistry, University of Helsinki, Finland
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14
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Code C, Mahalka AK, Bry K, Kinnunen PK. Activation of phospholipase A2 by 1-palmitoyl-2-(9'-oxo-nonanoyl)-sn-glycero-3-phosphocholine in vitro. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1798:1593-600. [DOI: 10.1016/j.bbamem.2010.05.002] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2009] [Revised: 04/28/2010] [Accepted: 05/03/2010] [Indexed: 11/26/2022]
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15
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Heimburg T. Lipid ion channels. Biophys Chem 2010; 150:2-22. [DOI: 10.1016/j.bpc.2010.02.018] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2010] [Revised: 02/27/2010] [Accepted: 02/27/2010] [Indexed: 10/19/2022]
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16
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Fanani ML, Hartel S, Maggio B, De Tullio L, Jara J, Olmos F, Oliveira RG. The action of sphingomyelinase in lipid monolayers as revealed by microscopic image analysis. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1798:1309-23. [DOI: 10.1016/j.bbamem.2010.01.001] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2009] [Revised: 12/16/2009] [Accepted: 01/04/2010] [Indexed: 11/26/2022]
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17
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Tong Y, Li N, Liu H, Ge A, Osawa M, Ye S. Mechanistic studies by sum-frequency generation spectroscopy: hydrolysis of a supported phospholipid bilayer by phospholipase A2. Angew Chem Int Ed Engl 2010; 49:2319-23. [PMID: 20209538 DOI: 10.1002/anie.200904950] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Yujin Tong
- Catalysis Research Centre, Hokkaido University, Sapporo 001-0021, Japan
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18
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Gudmand M, Rocha S, Hatzakis NS, Peneva K, Müllen K, Stamou D, Uji-I H, Hofkens J, Bjørnholm T, Heimburg T. Influence of lipid heterogeneity and phase behavior on phospholipase A2 action at the single molecule level. Biophys J 2010; 98:1873-82. [PMID: 20441751 PMCID: PMC2862199 DOI: 10.1016/j.bpj.2010.01.035] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2009] [Revised: 01/14/2010] [Accepted: 01/15/2010] [Indexed: 10/19/2022] Open
Abstract
We monitored the action of phospholipase A(2) (PLA(2)) on L- and D-dipalmitoyl-phosphatidylcholine (DPPC) Langmuir monolayers by mounting a Langmuir-trough on a wide-field fluorescence microscope with single molecule sensitivity. This made it possible to directly visualize the activity and diffusion behavior of single PLA(2) molecules in a heterogeneous lipid environment during active hydrolysis. The experiments showed that enzyme molecules adsorbed and interacted almost exclusively with the fluid region of the DPPC monolayers. Domains of gel state L-DPPC were degraded exclusively from the gel-fluid interface where the buildup of negatively charged hydrolysis products, fatty acid salts, led to changes in the mobility of PLA(2). The mobility of individual enzymes on the monolayers was characterized by single particle tracking. Diffusion coefficients of enzymes adsorbed to the fluid interface were between 3.2 microm(2)/s on the L-DPPC and 4.9 microm(2)/s on the D-DPPC monolayers. In regions enriched with hydrolysis products, the diffusion dropped to approximately 0.2 microm(2)/s. In addition, slower normal and anomalous diffusion modes were seen at the L-DPPC gel domain boundaries where hydrolysis took place. The average residence times of the enzyme in the fluid regions of the monolayer and on the product domain were between approximately 30 and 220 ms. At the gel domains it was below the experimental time resolution, i.e., enzymes were simply reflected from the gel domains back into solution.
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Affiliation(s)
- Martin Gudmand
- Membrane Biophysics Group, Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
- Nano-Science Center, University of Copenhagen, Copenhagen, Denmark
| | - Susana Rocha
- Laboratory for Photochemistry and Spectroscopy, Department of Chemistry, Catholic University of Leuven, Leuven, Belgium
| | | | - Kalina Peneva
- Max Planck Institut für Polymerforschung, Mainz, Germany
| | - Klaus Müllen
- Max Planck Institut für Polymerforschung, Mainz, Germany
| | - Dimitrios Stamou
- Nano-Science Center, University of Copenhagen, Copenhagen, Denmark
| | - Hiroshi Uji-I
- Laboratory for Photochemistry and Spectroscopy, Department of Chemistry, Catholic University of Leuven, Leuven, Belgium
| | - Johan Hofkens
- Laboratory for Photochemistry and Spectroscopy, Department of Chemistry, Catholic University of Leuven, Leuven, Belgium
| | - Thomas Bjørnholm
- Nano-Science Center, University of Copenhagen, Copenhagen, Denmark
| | - Thomas Heimburg
- Membrane Biophysics Group, Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
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19
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Tong Y, Li N, Liu H, Ge A, Osawa M, Ye S. Mechanistic Studies by Sum-Frequency Generation Spectroscopy: Hydrolysis of a Supported Phospholipid Bilayer by Phospholipase A2. Angew Chem Int Ed Engl 2010. [DOI: 10.1002/ange.200904950] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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20
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Sphingomyelinase-induced domain shape relaxation driven by out-of-equilibrium changes of composition. Biophys J 2010; 96:67-76. [PMID: 18849413 DOI: 10.1529/biophysj.108.141499] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2008] [Accepted: 08/27/2008] [Indexed: 11/18/2022] Open
Abstract
Sphingomyelinase (SMase)-induced ceramide (Cer)-enriched domains in a lipid monolayer are shown to result from an out-of-equilibrium situation. This is induced by a change of composition caused by the enzymatic production of Cer in a sphingomyelin (SM) monolayer that leads to a fast SM/Cer demixing into a liquid-condensed (LC), Cer-enriched and a liquid-expanded, SM-enriched phases. The morphological evolution and kinetic dependence of Cer-enriched domains is studied under continuous observation by epifluorescence microscopy. Domain shape annealing is observed from branched to rounded shapes after SMase activity quenching by EDTA, with a decay halftime of approximately 10 min. An out-of-equilibrium fast domain growth is not the determinant factor for domain morphology. Domain shape rearrangement in nearly equilibrium conditions result from the counteraction of intradomain dipolar repulsion and line tension, according to McConnell's shape transition theory. Phase separation causes a transient compositional overshoot within the LC phase that implies an increased out-of-equilibrium enrichment of Cer into the LC domains. As a consequence, higher intradomain repulsion leads to transient branched structures that relax to rounded shapes by lowering the proportion of Cer in the domain to equilibrium values. The fast action of SMase can be taken as a compositional perturbation that brings about important consequences for the surface organization.
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21
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Chemistry and Function of Phospholipids. FOOD SCIENCE AND TECHNOLOGY 2010. [DOI: 10.1201/9781420046649.ch2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/31/2023]
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22
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Pakkanen K, Salonen E, Mäkelä AR, Oker-Blom C, Vattulainen I, Vuento M. Desipramine induces disorder in cholesterol-rich membranes: implications for viral trafficking. Phys Biol 2009; 6:046004. [DOI: 10.1088/1478-3975/6/4/046004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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Bailey RW, Nguyen T, Robertson L, Gibbons E, Nelson J, Christensen RE, Bell JP, Judd AM, Bell JD. Sequence of physical changes to the cell membrane during glucocorticoid-induced apoptosis in S49 lymphoma cells. Biophys J 2009; 96:2709-18. [PMID: 19348753 DOI: 10.1016/j.bpj.2008.12.3925] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2008] [Revised: 12/15/2008] [Accepted: 12/18/2008] [Indexed: 01/03/2023] Open
Abstract
During apoptosis, physical changes in the plasma membrane prepare the cell for clearance by phagocytes and hydrolysis by secretory phospholipase A(2) (sPLA(2)). The relationships among these changes have not been adequately established, especially for hormone-stimulated apoptosis. This study addresses these issues for glucocorticoid-induced apoptosis in S49 lymphoma cells. Flow cytometry, microscopy, and fluorescence spectroscopy were used to assess merocyanine 540 emission, laurdan generalized polarization, phosphatidylserine exposure, caspase activation, and membrane permeability to propidium iodide in the absence and presence of sPLA(2). The earliest event observed was activation of cellular caspases. Results with membrane probes suggest that interlipid spacing also increases early during apoptosis and precedes transbilayer migration of phosphatidylserine, DNA fragmentation, and a general increase in lipid order associated with blebbing and dissolution of the cells. The activity of sPLA(2) appeared to be linked more to lipid spacing than to loss of membrane asymmetry. The early nature of some of these events and their ability to promote activity of a proinflammatory enzyme suggests the possibility of an inflammatory response during T-lymphocyte apoptosis.
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Affiliation(s)
- Rachel W Bailey
- Department of Physiology and Developmental Biology, Brigham Young University, Provo, Utah, USA
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24
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Wacklin HP. Interfacial Mechanism of Phospholipase A2: pH-Dependent Inhibition and Me-β-cyclodextrin Activation. Biochemistry 2009; 48:5874-81. [DOI: 10.1021/bi802280b] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Hanna P. Wacklin
- Australian Nuclear Science and Technology Organisation, PMB1, Menai, NSW 2234, Australia and Institut Laue Langevin, BP 156, 38042 Grenoble Cedex 9, France
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25
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Activation of phospholipase A2 by temporin B: formation of antimicrobial peptide-enzyme amyloid-type cofibrils. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2009; 1788:1064-72. [PMID: 19285031 DOI: 10.1016/j.bbamem.2009.03.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2008] [Revised: 03/03/2009] [Accepted: 03/03/2009] [Indexed: 11/21/2022]
Abstract
Phospholipases A2 have been shown to be activated in a concentration dependent manner by a number of antimicrobial peptides, including melittin, magainin 2, indolicidin, and temporins B and L. Here we used fluorescently labelled bee venom PLA2 (PLA2D) and the saturated phospholipid substrate 1,2-dipalmitoyl-glycero-sn-3-phosphocholine (L-DPPC), exhibiting a lag-burst behaviour upon the initiation of the hydrolytic reaction by PLA2. Increasing concentrations of Cys-temporin B and its fluorescent Texas red derivative (TRC-temB) caused progressive shortening of the lag period. TRC-temB/PLA2D interaction was observed by Förster resonance energy transfer (FRET), with maximum efficiency coinciding with the burst in hydrolysis. Subsequently, supramolecular structures became visible by microscopy, revealing amyloid-like fibrils composed of both the activating peptide and PLA2. Reaction products, palmitic acid and 1-palmitoyl-2-lyso-glycero-sn-3-phosphocholine (lysoPC, both at >8 mol%) were required for FRET when using the non-hydrolysable substrate enantiomer 2,3-dipalmitoyl-glycero-sn-1-phosphocholine (D-DPPC). A novel mechanism of PLA2 activation by co-fibril formation and associated conformational changes is suggested.
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26
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Kuppe K, Kerth A, Blume A, Ulbrich-Hofmann R. Calcium-induced membrane microdomains trigger plant phospholipase D activity. Chembiochem 2009; 9:2853-9. [PMID: 18942690 DOI: 10.1002/cbic.200800431] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Plant alpha-type phospholipase D proteins are calcium-dependent, lipolytic enzymes. The morphology of the aggregates of their phospholipid substrate fundamentally defines the interaction between the enzyme and the surface. Here we demonstrate that the Ca(2+)-induced generation of membrane microdomains dramatically activates alpha-type phospholipase D from white cabbage. 500-fold stimulation was observed upon incorporation of 10 mol % 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphate (POPA) into 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) vesicles in the presence of Ca(2+) ions. Enhanced association of PLDalpha2 with phospholipid surfaces containing anionic components was indicated by lag phase analysis and film balance measurements. Differential scanning calorimetry showed that the POPA-specific activation correlates with the phase behavior of the POPC/POPA vesicles in the presence of Ca(2+) ions. We conclude from the results that the Ca(2+)-induced formation of POPA microdomains is the crucial parameter that facilitates the binding of PLD to the phospholipid surface and suggest that this effect serves as a cellular switch for controlling PLD activity.
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Affiliation(s)
- Konstantin Kuppe
- Institute of Biochemistry and Biotechnology, Martin-Luther University Halle-Wittenberg, Kurt-Mothes Strasse 3, 06120 Halle, Germany
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27
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Vallejo AA, Fernández MS. FRET between non-substrate probes detects lateral lipid domain formation during phospholipase A2 interfacial catalysis. Arch Biochem Biophys 2008; 480:1-10. [DOI: 10.1016/j.abb.2008.09.015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2008] [Revised: 09/19/2008] [Accepted: 09/25/2008] [Indexed: 10/21/2022]
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28
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Elegbede AI, Banerjee J, Hanson AJ, Tobwala S, Ganguli B, Wang R, Lu X, Srivastava DK, Mallik S. Mechanistic studies of the triggered release of liposomal contents by matrix metalloproteinase-9. J Am Chem Soc 2008; 130:10633-42. [PMID: 18642903 PMCID: PMC2644422 DOI: 10.1021/ja801548g] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Matrix metalloproteinases (MMPs) constitute a class of extracellular-matrix-degrading enzymes overexpressed in many cancers and contribute to the metastatic ability of the cancer cells. We have recently demonstrated that liposomal contents can be released when triggered by the enzyme MMP-9. Herein, we report the results of our mechanistic studies of the MMP-9-triggered release of liposomal contents. We synthesized peptides containing the cleavage site for MMP-9 and conjugated them with fatty acids to prepare the corresponding lipopeptides. By employing circular dichroism (CD) spectroscopy, we demonstrated that the lipopeptides, when incorporated into liposomes, are demixed in the lipid bilayers and generate triple-helical structures. MMP-9 cleaves the triple-helical peptides, leading to the release of the liposomal contents. Other MMPs, which cannot hydrolyze triple-helical peptides, fail to release the contents from the liposomes. We also observed that the rate and extent of release of the liposomal contents depend on the mismatch between the acyl chains of the synthesized lipopeptide and phospholipid components of the liposomes. CD spectroscopic studies imply that the observed differences in the release reflect the ability of the liposomal membrane to anneal the defects following the enzymatic cleavage of the liposome-incorporated lipopeptides.
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Affiliation(s)
- Adekunle I. Elegbede
- Department of Pharmaceutical Sciences, North Dakota State University, Fargo, North Dakota 58105
| | - Jayati Banerjee
- Department of Pharmaceutical Sciences, North Dakota State University, Fargo, North Dakota 58105
| | - Andrea J. Hanson
- Department of Pharmaceutical Sciences, North Dakota State University, Fargo, North Dakota 58105
| | - Shakila Tobwala
- Department of Chemistry, Biochemistry and Molecular Biology, North Dakota State University, Fargo, North Dakota 58105
| | - Bratati Ganguli
- Department of Chemistry, Biochemistry and Molecular Biology, North Dakota State University, Fargo, North Dakota 58105
| | - Rongying Wang
- Proteomics Core Facility, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, North Dakota 58202
| | - Xiaoning Lu
- Proteomics Core Facility, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, North Dakota 58202
| | - D. K. Srivastava
- Department of Chemistry, Biochemistry and Molecular Biology, North Dakota State University, Fargo, North Dakota 58105
| | - Sanku Mallik
- Department of Pharmaceutical Sciences, North Dakota State University, Fargo, North Dakota 58105
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29
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Effects of cholesterol on physical properties of human erythrocyte membranes: impact on susceptibility to hydrolysis by secretory phospholipase A2. Biophys J 2008; 94:3084-93. [PMID: 18192373 DOI: 10.1529/biophysj.107.118356] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The ability of secretory phospholipase A(2) (sPLA(2)) to hydrolyze cell membranes is highly dependent on the physical properties of the membrane. The effects of cholesterol on these properties have been characterized in artificial bilayers and found to alter sPLA(2) activity significantly. It is hypothesized that the natural difference in cholesterol content between erythrocytes and leukocytes is in part responsible for their differing susceptibility to hydrolysis by sPLA(2). To test this hypothesis, defined amounts of cholesterol were removed from erythrocyte membranes using methyl-beta-cyclodextrin. Treatment of cells with methyl-beta-cyclodextrin increased the hydrolysis rate and total substrate hydrolyzed by sPLA(2). In general, this effect of cholesterol removal was more pronounced at higher temperatures. Comparison of the level of membrane order (assessed with the fluorescent probe laurdan) with hydrolysis rate revealed that sPLA(2) activity was greatly enhanced upon significant reductions in lipid order. Additional treatment of the cells with calcium ionophore further enhanced the hydrolysis rate and altered the relationship with membrane order. These data demonstrated that interactions with sPLA(2) observed in artificial bilayers apply to biological membranes. It is also proposed that the high level of cholesterol in erythrocyte membranes is a protective mechanism to guard against hydrolytic enzymes.
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30
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Liang H, Whited G, Nguyen C, Okerlund A, Stucky GD. Inherently tunable electrostatic assembly of membrane proteins. NANO LETTERS 2008; 8:333-339. [PMID: 18052232 DOI: 10.1021/nl0729173] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Membrane proteins are a class of nanoscopic entities that control the matter, energy, and information transport across cellular boundaries. Electrostatic interactions are shown to direct the rapid co-assembly of proteorhodopsin (PR) and lipids into long-range crystalline arrays. The roles of inherent charge variations on lipid membranes and PR variants with different compositions are examined by tuning recombinant PR variants with different extramembrane domain sizes and charged amino acid substitutions, lipid membrane compositions, and lipid-to-PR stoichiometric ratios. Rational control of this predominantly electrostatic assembly for PR crystallization is demonstrated, and the same principles should be applicable to the assembly and crystallization of other integral membrane proteins.
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Affiliation(s)
- Hongjun Liang
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106, USA
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31
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Wagner K, Desbat B, Brezesinski G. Liquid–liquid immiscibility in model membranes activates secretory phospholipase A2. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2008; 1778:166-74. [DOI: 10.1016/j.bbamem.2007.09.015] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2007] [Revised: 09/17/2007] [Accepted: 09/19/2007] [Indexed: 01/16/2023]
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32
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Brake JM, Abbott NL. Coupling of the orientations of thermotropic liquid crystals to protein binding events at lipid-decorated interfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2007; 23:8497-507. [PMID: 17595119 DOI: 10.1021/la0634286] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
We report a study of the interactions of proteins with monolayers of phospholipids (D/L-alpha-dipalmitoyl phosphatidylcholine and L-alpha-dilauroyl phosphatidylcholine) spontaneously assembled at an interface between an aqueous phase and a 20-microm-thick film of a nematic liquid crystal (4'-pentyl-4-cyanobiphenyl). Because the orientation of the liquid crystal is coupled to the organization of the lipids, specific interactions between phospholipase A2 and the lipids (binding and/or hydrolysis) that lead to reorganization of the lipids are optically reported (using polarized light) as dynamic orientational transitions in the liquid crystal. In contrast, nonspecific interactions between proteins such as albumin, lysozyme, and cytochrome-c and the lipid-laden interface of the liquid crystal are not reported as orientational transitions in the liquid crystals. Concurrent epifluorescence and polarized light imaging of labeled lipids and proteins at the aqueous-liquid crystal interface demonstrate that spatially patterned orientations of the liquid crystals observed during specific binding of phospholipase A2 to the interface, as well as during the subsequent hydrolysis of lipids by phospholipase A2, reflect the lateral organization (micrometer-sized domains) of the proteins and lipids, respectively, at the aqueous-liquid crystal interface.
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Affiliation(s)
- Jeffrey M Brake
- Department of Chemical Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, Wisconsin 53706, USA
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33
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Bailey RW, Olson ED, Vu MP, Brueseke TJ, Robertson L, Christensen RE, Parker KH, Judd AM, Bell JD. Relationship between membrane physical properties and secretory phospholipase A2 hydrolysis kinetics in S49 cells during ionophore-induced apoptosis. Biophys J 2007; 93:2350-62. [PMID: 17545239 PMCID: PMC1965435 DOI: 10.1529/biophysj.107.104679] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
During apoptosis, changes occur in lymphocyte membranes that render them susceptible to hydrolysis by secretory phospholipase A(2) (sPLA(2)). To study the relevant mechanisms, a simplified model of apoptosis using a calcium ionophore was applied. Kinetic and flow cytometry experiments provided key observations regarding ionophore treatment: the initial rate of hydrolysis was elevated at all enzyme concentrations, the total amount of reaction product was increased fourfold, and adsorption of the enzyme to the membrane surface was unaltered. Analysis of these results suggested that susceptibility during calcium-induced apoptosis is limited by availability of substrate rather than adsorption of enzyme. Fluorescence experiments identified three membrane alterations during apoptosis that might affect substrate access to the sPLA(2) active site. First, intercalation of merocyanine 540 into the membrane was improved, suggesting an increase in lipid spacing. Second, laurdan detected increased solvation of the lower headgroup region of the membrane. Third, the rate at which fluorescent lipids could be removed from the membrane by albumin was enhanced, implying greater vertical mobility of phospholipids. Thus, it is proposed that the membranes of apoptotic cells become susceptible to sPLA(2) through a reduction in lipid-neighbor interactions that facilitates migration of phospholipids into the enzyme active site.
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Affiliation(s)
- Rachel W Bailey
- Department of Physiology and Developmental Biology, Brigham Young University, Provo, Utah, USA
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34
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Wacklin HP, Tiberg F, Fragneto G, Thomas RK. Distribution of reaction products in phospholipase A2 hydrolysis. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1768:1036-49. [PMID: 17355873 DOI: 10.1016/j.bbamem.2006.10.020] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2006] [Revised: 09/20/2006] [Accepted: 10/30/2006] [Indexed: 11/29/2022]
Abstract
We have monitored the composition of supported phospholipid bilayers during phospholipase A(2) hydrolysis using specular neutron reflection and ellipsometry. Porcine pancreatic PLA(2) shows a long lag phase of several hours during which the enzyme binds to the bilayer surface, but only 5+/-3% of the lipids react before the onset of rapid hydrolysis. The amount of PLA(2), which resides in a 21+/-1 A thick layer at the water-bilayer interface, as well as its depth of penetration into the membrane, increase during the lag phase, the length of which is also proportional to the enzyme concentration. Hydrolysis of a single-chain deuterium labelled d(31)-POPC reveals for the first time that there is a significant asymmetry in the distribution of the reaction products between the membrane and the aqueous environment. The lyso-lipid leaves the membrane while the number of PLA(2) molecules bound to the interface increases with increasing fatty acid content. These results constitute the first direct measurement of the membrane structure and composition, including the location and amount of the enzyme during hydrolysis. These are discussed in terms of a model of fatty-acid mediated activation of PLA(2).
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Affiliation(s)
- Hanna P Wacklin
- Oxford University, Physical and Theoretical Chemistry Laboratory, South Parks Road, Oxford OX1 3QZ, UK.
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35
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De Tullio L, Maggio B, Hartel S, Jara J, Fanani ML. The initial surface composition and topography modulate sphingomyelinase-driven sphingomyelin to ceramide conversion in lipid monolayers. Cell Biochem Biophys 2007; 47:169-77. [PMID: 17652769 DOI: 10.1007/s12013-007-0001-1] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/1999] [Revised: 11/30/1999] [Accepted: 11/30/1999] [Indexed: 01/28/2023]
Abstract
Changes of the initial composition and topography of mixed monolayers of Sphingomyelin and Ceramide modulate the degradation of Sphingomyelin by Bacillus cereus Sphingomyelinase. The presence of initial lateral phase boundary due to coexisting condensed and expanded phase domains favors the precatalytic steps of the reaction. The amount and quality of the domain lateral interface, defined by the type of boundary undulation, appears as a modulatory supramolecular code which regulates the catalytic efficiency of the enzyme. The long range domain lattice structuring is determined by the Sphingomyelinase activity.
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Affiliation(s)
- Luisina De Tullio
- Departamento de Química Biológica, Facultad de Ciencias Químicas - CONICET, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende, Ciudad Universitaria, X5000HUA Córdoba, República Argentina
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36
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Cherney DP, Myers GA, Horton RA, Harris JM. Optically trapping confocal Raman microscopy of individual lipid vesicles: kinetics of phospholipase A(2)-catalyzed hydrolysis of phospholipids in the membrane bilayer. Anal Chem 2007; 78:6928-35. [PMID: 17007516 DOI: 10.1021/ac061049b] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Phospholipase A2 (PLA2)-catalyzed hydrolysis at the sn-2 position of 1,2-dimyristoyl-sn-glycero-3-phosphocholine in optically trapped liposomes is monitored in situ using confocal Raman microscopy. Individual optically trapped liposomes (0.6 microm in diameter) are exposed to PLA2 isolated from cobra (Naja naja naja) venom at varying enzyme concentrations. The relative Raman scattering intensities of C-C stretching vibrations from the trans and gauche conformers of the acyl chains are correlated directly with the extent of hydrolysis, allowing the progress of the reaction to be monitored in situ on a single vesicle. In dilute vesicle dispersions, the technique allows the much higher local concentration of lipid molecules in a single vesicle to be detected free of interferences from the surrounding solution. Observing the local composition of an optically trapped vesicle also allows one to determine whether the products of enzyme-catalyzed hydrolysis remain associated with the vesicle or dissolve into solution. The observed reaction kinetics exhibited a time lag prior to the rapid hydrolysis. The lag time varied inversely with the enzyme concentration, which is consistent with the products of enzyme-catalyzed lipid hydrolysis reaching a critical concentration that allows the enzyme to react at a much faster rate. The turnover rate of membrane-bound enzyme determined by Raman microscopy during the rapid, burst-phase kinetics was 1200 s(-1). Based on previous measurements of the equilibrium for PLA2 binding to lipid membranes, the average number of enzyme molecules responsible for catalyzing the hydrolysis of lipid on a single optically trapped vesicle is quite small, only two PLA2 molecules at the lowest enzyme concentration studied.
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Affiliation(s)
- Daniel P Cherney
- Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112-0850, USA
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37
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Brueseke TJ, Bell JD. A new hat for an old enzyme: Waste management. Biochim Biophys Acta Mol Cell Biol Lipids 2006; 1761:1270-9. [PMID: 16828338 DOI: 10.1016/j.bbalip.2006.05.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2006] [Revised: 05/19/2006] [Accepted: 05/24/2006] [Indexed: 11/27/2022]
Abstract
The history of research regarding secretory phospholipase A(2) (sPLA(2)) has often focused in one of two directions. Originally, the enzyme was studied biophysically in terms of its fundamental structure, enzymology, and the relationship between membrane physics and catalytic activity. More recently, a large and growing body of information has accumulated concerning regulatory factors, tissue distribution, and physiological/pathological roles of sPLA(2). Evidence is presented that suggests an additional function for the protein in which it helps to clear dead and damaged cells while avoiding digestion of those that are healthy. Apparently, the ability of the enzyme to discriminate between susceptible and resistant cells depends on physical properties of membrane lipids related to order, distribution, and neighbor/neighbor interactions. Investigations into this action of the enzyme offer the rare opportunity to apply biophysical approaches and principles to a physiological setting.
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Affiliation(s)
- Taylor J Brueseke
- Department of Physiology and Developmental Biology, College of Biology and Agriculture, 302C WIDB, Brigham Young University, Provo, UT 84602, USA
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38
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Leidy C, Linderoth L, Andresen TL, Mouritsen OG, Jørgensen K, Peters GH. Domain-induced activation of human phospholipase A2 type IIA: local versus global lipid composition. Biophys J 2006; 90:3165-75. [PMID: 16461407 PMCID: PMC1432114 DOI: 10.1529/biophysj.105.070987] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Secretory human phospholipase A2 type IIA (PLA2-IIA) catalyzes the hydrolysis of the sn-2 ester bond in glycerolipids to produce fatty acids and lysolipids. The enzyme is coupled to the inflammatory response, and its specificity toward anionic membrane interfaces suggests a role as a bactericidal agent. PLA2-IIA may also target perturbed native cell membranes that expose anionic lipids to the extracellular face. However, anionic lipid contents in native cells appear lower than the threshold levels necessary for activation. By using phosphatidylcholine/phosphatidylglycerol model systems, we show that local enrichment of anionic lipids into fluid domains triggers PLA2-IIA activity. In addition, the compositional range of enzyme activity is shown to be related to the underlying lipid phase diagram. A comparison is done between PLA2-IIA and snake venom PLA2, which in contrast to PLA2-IIA hydrolyzes both anionic and zwitterionic membranes. In general, this work shows that PLA2-IIA activation can be accomplished through local enrichment of anionic lipids into domains, indicating a mechanism for PLA2-IIA to target perturbed native membranes with low global anionic lipid contents. The results also show that the underlying lipid phase diagram, which determines the lipid composition at a local level, can be used to predict PLA2-IIA activity.
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Affiliation(s)
- Chad Leidy
- Department of Physics, Universidad de los Andes, Bogotá, Colombia.
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39
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Andresen TL, Jørgensen K. Synthesis and membrane behavior of a new class of unnatural phospholipid analogs useful as phospholipase A2 degradable liposomal drug carriers. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2005; 1669:1-7. [PMID: 15842993 DOI: 10.1016/j.bbamem.2005.02.012] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2004] [Revised: 02/07/2005] [Accepted: 02/24/2005] [Indexed: 01/02/2023]
Abstract
A new and unnatural type of lipid analogs with the phosphocholine and phosphoglycerol head groups linked to the C-2 position of the glycerol moiety have been synthesized and the thermodynamic lipid membrane behavior has been investigated using differential scanning calorimetry. From the heat capacity measurements, it was observed that the pre-transition was abolished most likely due to the central position of the head groups providing better packing properties in the low temperature ordered gel phase. Activity measurements of secretory phospholipase A2 (PLA2) on unilamellar liposomal membranes revealed that the unnatural phospholipids are excellent substrates for PLA2 catalyzed hydrolysis. This was manifested as a minimum in the PLA2 lag time in the main phase transition temperature regime and a high degree of lipid hydrolysis over a broad temperature range. The obtained results provide new information about the interplay between the molecular structure of phospholipids and the lipid membrane packing constrains that govern the pre-transition. In addition, the PLA2 activity measurements are useful for obtaining deeper insight into the molecular details of the catalytic site of PLA2. The combined results also suggest new approaches to rationally design liposomal drug carries that can undergo a triggered activation in diseased tissue by overexpressed PLA2.
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Affiliation(s)
- Thomas L Andresen
- Department of Chemistry, Technical University of Denmark, DK-2800 Lyngby, Denmark
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40
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Nakahara H, Nakamura S, Nakamura K, Inagaki M, Aso M, Higuchi R, Shibata O. Cerebroside Langmuir monolayers originated from the echinoderms: II. Binary systems of cerebrosides and steroids. Colloids Surf B Biointerfaces 2005; 42:175-85. [PMID: 15833669 DOI: 10.1016/j.colsurfb.2005.01.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2004] [Accepted: 01/29/2005] [Indexed: 11/30/2022]
Abstract
Two-component Langmuir monolayers formed on a subphase of 0.5M sodium chloride solution were investigated for two different cerebrosides (LMC-1 and LMC-2) with steroids of cholesterol (Ch) and cholesteryl sodium sulfate (Ch-S); i.e. LMC-1/Ch, LMC-1/Ch-S, LMC-2/Ch, and LMC-2/Ch-S were examined in terms of surface pressure (pi), the surface potential (DeltaV) and the dipole moment (mu( perpendicular)) as a function of surface area (A) by employing the Langmuir method, the ionizing electrode method, and the fluorescence microscopy. Surface potentials (DeltaV) of steroids were analyzed using the three-layer model proposed by Demchak and Fort. The miscibility of cerebrosides and steroids in the insoluble monolayers was examined by plotting the variation of the molecular area and the surface potential as a function of the steroid molar fraction (X(steroid)) based upon the additivity rule. From the A-X(steroid) and DeltaV(m)-X(steroid) plots, partial molecular surface area (PMA) and apparent partial molecular surface potential (APSP) were determined at the different surface pressures. The PMA and APSP with the mole fraction were discussed for the miscible system. Judging from the two-dimensional phase diagrams, they can be classified into two types. The first is a completely immiscible type; the combination of cerebrosides with cholesterol. The second is a negative azeotropic type, where cerebrosides and cholesteryl sodium sulfate are completely miscible both in the expanded state and in the condensed state. In addition, a regular surface mixture (the Joos equation for the analysis of the collapse pressure of two-component monolayers) allowed calculation of the interaction parameter (xi) and the interaction energy (-Delta epsilon) between the cerebrosides and Ch-S. The miscibility of cerebroside and steroid components in the monolayer state was also supported by fluorescence microscopy.
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Affiliation(s)
- Hiromichi Nakahara
- Division of Biointerfacial Science, Graduate School of Pharmaceutical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
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Leidy C, Mouritsen OG, Jørgensen K, Peters GH. Evolution of a rippled membrane during phospholipase A2 hydrolysis studied by time-resolved AFM. Biophys J 2005; 87:408-18. [PMID: 15240475 PMCID: PMC1304362 DOI: 10.1529/biophysj.103.036103] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The sensitivity of phospholipase A(2) (PLA(2)) for lipid membrane curvature is explored by monitoring, through time-resolved atomic force microscopy, the hydrolysis of supported double bilayers in the ripple phase. The ripple phase presents a corrugated morphology. PLA(2) is shown to have higher activity toward the ripple phase compared to the gel phase in 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) membranes, indicating its preference for this highly curved membrane morphology. Hydrolysis of the stable and metastable ripple structures is monitored for equimolar DMPC/1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC)-supported double bilayers. As shown by high-performance liquid chromatography results, DSPC is resistant to hydrolysis at this temperature, resulting in a more gradual hydrolysis of the surface that leads to a change in membrane morphology without loss of membrane integrity. This is reflected in an increase in ripple spacing, followed by a sudden flattening of the lipid membrane during hydrolysis. Hydrolysis of the ripple phase results in anisotropic holes running parallel to the ripples, suggesting that the ripple phase has strip regions of higher sensitivity to enzymatic attack. Bulk high-performance liquid chromatography measurements indicate that PLA(2) preferentially hydrolyzes DMPC in the DMPC/DSPC ripples. We suggest that this leads to the formation of a flat gel-phase lipid membrane due to enrichment in DSPC. The results point to the ability of PLA(2) for inducing a compositional phase transition in multicomponent membranes through preferential hydrolysis while preserving membrane integrity.
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Affiliation(s)
- Chad Leidy
- MEMPHYS-Center for Biomembrane Physics, and Department of Chemistry, Technical University of Denmark, DK-2800 Lyngby, Denmark.
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Justesen PH, Kristensen T, Ebdrup T, Otzen D. Investigating porcine pancreatic phospholipase A2 action on vesicles and supported planar bilayers using a quartz crystal microbalance with dissipation. J Colloid Interface Sci 2004; 279:399-409. [PMID: 15464804 DOI: 10.1016/j.jcis.2004.06.083] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2003] [Accepted: 06/27/2004] [Indexed: 11/15/2022]
Abstract
We present an investigation of the activity of porcine pancreatic phospholipase A2 towards phospholipids. The phospholipids are presented in three different ways, namely as tethered vesicles, intact surface-bound vesicles, and supported planar bilayers (SPBs). The process is followed using a quartz crystal microbalance which measures both the frequency shift and the energy dissipation factor. This technique is very sensitive not only to the mass of the material deposited on the crystal, but also to its viscoelasticity. The breakdown of the phospholipid vesicles and bilayers consequently gives rise to very large signal changes. Enzyme binding is separated from vesicle hydrolysis using nonhydrolyzable ether lipids. Intact and tethered vesicles give rise to the same profile, indicating that direct immobilization of the vesicles does not affect hydrolysis significantly. The data fit well to a Voight-based model describing the change in film structure with time. Initial enzyme binding to intact vesicles is accompanied by a significant increase in layer thickness as well as a decrease in viscosity and shear modulus. This effect, which is less pronounced in SPBs, is probably mainly due to the accumulation of hydrolysis products in the vesicle prior to rupture of the vesicles and release of bound water, since it disappears when lysolipid is included in the vesicles prior to hydrolysis.
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Affiliation(s)
- Pernille H Justesen
- Department of Life Sciences, Aalborg University, Sohngaardsholmsvej 49, DK-9000 Aalborg, Denmark
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43
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Estrela-Lopis I, Brezesinski G, Möhwald H. Miscibility of DPPC and DPPA in monolayers at the air/water interface. Chem Phys Lipids 2004; 131:71-80. [PMID: 15210366 DOI: 10.1016/j.chemphyslip.2004.04.005] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2003] [Revised: 03/23/2004] [Accepted: 04/05/2004] [Indexed: 10/26/2022]
Abstract
Monolayers of mixtures of 1,2-dipalmitoylphosphatidylcholine (DPPC) as the substrate and 1,2-dipalmitoylphosphatidic acid (DPPA) as the product of the hydrolysis reaction catalyzed by phospholipase D (PLD) were investigated in the presence of Ca2+. The miscibility behavior and the microstructure of mixed domains have been studied by grazing incidence X-ray diffraction (GIXD), Brewster angle microscopy and film balance measurements. The phase diagram reveals partial miscibility on both sides and a wide miscibility gap, which becomes narrower at high pressure. At low pressure, the segregation of condensed DPPA-rich domains in a fluid-like DPPC matrix was detected already at small DPPA concentrations and their structure was determined. A small amount of DPPC mixed into the segregated DPPA domains induces the transformation from rectangular to an oblique unit cell and increases the tilt angle in the condensed domains. At high pressure, two types of condensed phase domains were found: DPPC-rich and DPPA-rich. A drastic reduction of the tilt angle in the DPPC-rich domains with increasing amount of DPPA was observed. The decrease of the tilt angle must be connected with a change of the head group conformation of DPPC in such mixed domains.
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Affiliation(s)
- I Estrela-Lopis
- Institute for Medical Physics and Biophysics, University of Leipzig, Liebigstr. 27, D-04103 Leipzig, Germany
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44
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Borioli GA, Caputto BL, Maggio B. Phospholipase activity is modulated by c-Fos through substrate expansion and hyperpolarization. FEBS Lett 2004; 570:82-6. [PMID: 15251444 DOI: 10.1016/j.febslet.2004.06.033] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2004] [Accepted: 06/09/2004] [Indexed: 10/26/2022]
Abstract
c-Fos, a component of AP-1 transcription factors, has been shown to have marked amphitropic properties and to regulate phospholipase activity against lipid monolayers. In agreement with its high surface activity, it has also been found to associate to membranes of the endoplasmic reticulum and to activate phospholipid metabolism in vivo. All these findings point to an involvement of this oncoprotein within a membrane environment. We have previously shown that c-Fos modulates in different manners the activity of phospholipase A2 and phospholipase C against monolayers of dilauroylphosphatidylcholine (PC). In this work, we have studied the possible molecular mechanism underlying the phosphohydrolytic modulation. Our results show that c-Fos expands and hyperpolarizes PC, indicating that its effects on these enzymatic activities are due to the changes it induces on the interfacial organization of the substrate.
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Affiliation(s)
- Graciela A Borioli
- CIQUIBIC, Departmento Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba Pabellón Argentina, Ciudad Universitaria, 5000 Córdoba, Argentina.
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45
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Gómez-Serranillos IR, Miñones J, Dynarowicz-łatka P, Miñiones J, Iribarnegaray E. Miltefosine-cholesterol interactions: a monolayer study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2004; 20:928-933. [PMID: 15773125 DOI: 10.1021/la0303254] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Mixed Langmuir monolayers of miltefosine (hexadecylphosphocholine) and cholesterol have been investigated by recording surface pressure-area (pi-A) isotherms at different subphase pHs (2, 6, and 10) and temperatures (10, 20, 25, and 30 degrees C). The change of both pH and temperature within the investigated range does not modify significantly the behavior of mixed films. The most pronounced effect involves condensation of the miltefosine monolayer by cholesterol, which diminishes in the following order: pH 6 > pH 2 > pH 10. The analyses of pi-A and compressibility modulus dependencies indicate the existence of interactions in the investigated system; at pH 2 and 6, the strongest were found to occur for the mixed film of miltefosine molar fraction (XM) between 0.6 and 0.7 (mean value, 0.66). Such a composition corresponds to the stable complex formation wherein 2 miltefosine molecules and 1 molecule of cholesterol are strongly bound together, mainly by attractive hydrophobic forces between their apolar tails. However, at pH 10 the highest stability occurs for mixtures containing a smaller proportion of miltefosine (XM = 0.5), which means that on alkaline subphases the ability to condense the miltefosine monolayer by cholesterol is less efficient as it requires a higher proportion of cholesterol (1:1 as compared to 1:2 at pH 2 and 6) to attain the maximum stability of the mixed film. The attractive forces between miltefosine and cholesterol are also weaker at pH 10 due to a greater solvatation of the miltefosine polar group. A similar trend is observed on increasing subphase temperature, when monolayers are more expanded.
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Affiliation(s)
- I Rey Gómez-Serranillos
- Department of Physical Chemistry, Faculty of Pharmacy, University of Santiago de Compostela, Santiago de Compostela, Spain
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46
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Ickenstein LM, Arfvidsson MC, Needham D, Mayer LD, Edwards K. Disc formation in cholesterol-free liposomes during phase transition. BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1614:135-8. [PMID: 12896806 DOI: 10.1016/s0005-2736(03)00196-2] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Cryogenic transmission electron microscopy (cryo-TEM) images of lysolipid-containing thermosensitive liposomes (LTSL) revealed that open liposomes and bilayer discs appeared when liposomes were cycled through the gel (Lbeta') to liquid-crystalline (Lalpha) phase transition. The amount of bilayer discs generated was dependent on the combined presence of PEG-lipid and lysolipid in the membrane. We hypothesize that micelle-forming membrane components stabilize the rim of bilayer openings and membrane discs that form when liposomes are cycled through TC.
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Affiliation(s)
- Ludger M Ickenstein
- Department of Advanced Therapeutics, The British Columbia Cancer Agency Research Centre, 601 West 10th Avenue, Vancouver, BC, Canada V5Z 1L3
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47
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48
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Bagatolli LA, Sanchez SA, Hazlett T, Gratton E. Giant vesicles, Laurdan, and two-photon fluorescence microscopy: evidence of lipid lateral separation in bilayers. Methods Enzymol 2003; 360:481-500. [PMID: 12622164 DOI: 10.1016/s0076-6879(03)60124-2] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Luis A Bagatolli
- Department of Physics, MEMPHYS-Center for Biomembrane Physics, University of Southern Denmark, Odense
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49
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Brezesinski G, Möhwald H. Langmuir monolayers to study interactions at model membrane surfaces. Adv Colloid Interface Sci 2003; 100-102:563-84. [PMID: 12668338 DOI: 10.1016/s0001-8686(02)00071-4] [Citation(s) in RCA: 229] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Langmuir monolayers at the liquid-air interface are well-defined interfacial systems and, therefore, excellent model systems to learn about interactions at interfaces beyond the classical DLVO description. Many parameters can be independently varied over a broad range and the structure can be analyzed with A precision. In the first part of the paper, the rich polymorphism in monolayers composed of amphiphilic molecules is demonstrated. Using homologues series generic phase diagrams can be derived. The delicate interplay of interactions causes a richness of phases which in turn can be used to measure fine variations in these interactions. Based on the understanding of the polymorphism in pure or mixed lipid monolayers, one can study the interaction of molecules dissolved in the subphase with monolayers. Samples presented are chemical reactions catalyzed by enzymes and coupling of polyelectrolytes to oppositely charged monolayers. To relate structure and reactivity, the activity of enzymes at the interface can be studied, predominantly combining X-ray diffraction and FTIR-spectroscopy. It is shown that the activity depends on monolayer structure. In one case, the reaction product leads to structural changes in the monolayer and stops the reaction, hence, indicating a subtle case of product inhibition via the membrane. On the other hand it has become possible to manipulate the organization of polyelectrolytes at interfaces via lipid charge density and ionic strength. In the most important case of DNA interacting with a membrane surface we show that DNA arranges at the interface in a lamellar manner, and the intermolecular distances, measured by Synchrotron X-ray diffraction can be varied by the lipid density.
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Affiliation(s)
- Gerald Brezesinski
- Max-Planck-Institute of Colloids and Interfaces, Am Mühlenberg 1, D-14476, Golm, Germany.
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50
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Bell JD, Sanchez SA, Hazlett TL. Liposomes in the Study of Phospholipase A2 Activity. Methods Enzymol 2003; 372:19-48. [PMID: 14610805 DOI: 10.1016/s0076-6879(03)72002-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/27/2023]
Affiliation(s)
- John D Bell
- Department of Physiology and Developmental Biology, Brigham Young University, Provo, Utah 84602, USA
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