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Fanani ML, Ambroggio EE. Phospholipases and Membrane Curvature: What Is Happening at the Surface? MEMBRANES 2023; 13:190. [PMID: 36837693 PMCID: PMC9965983 DOI: 10.3390/membranes13020190] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/30/2022] [Revised: 01/27/2023] [Accepted: 01/31/2023] [Indexed: 06/18/2023]
Abstract
In this revision work, we emphasize the close relationship between the action of phospholipases and the modulation of membrane curvature and curvature stress resulting from this activity. The alteration of the tridimensional structure of membranes upon the action of phospholipases is analyzed based on studies on model lipid membranes. The transient unbalance of both compositional and physical membrane properties between the hemilayers upon phospholipase activity lead to curvature tension and the catalysis of several membrane-related processes. Several proteins' membrane-bound and soluble forms are susceptible to regulation by the curvature stress induced by phospholipase action, which has important consequences in cell signaling. Additionally, the modulation of membrane fusion by phospholipase products regulates membrane dynamics in several cellular scenarios. We commented on vesicle fusion in the Golgi-endoplasmic system, synaptic vesicle fusion to the plasma membrane, viral membrane fusion to host cell plasma membrane and gametes membrane fusion upon acrosomal reaction. Furthermore, we explored the modulation of membrane fusion by the asymmetric adsorption of amphiphilic drugs. A deep understanding of the relevance of lipid membrane structure, particularly membrane curvature and curvature stress, on different cellular events leads to the challenge of its regulation, which may become a powerful tool for pharmacological therapy.
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Affiliation(s)
- María Laura Fanani
- Departamento de Química Biológica Ranwel Caputto, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba X5000HUA, Argentina
- Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), CONICET, Haya de la Torre y Medina Allende, Ciudad Universitaria, Córdoba X5000HUA, Argentina
| | - Ernesto Esteban Ambroggio
- Departamento de Química Biológica Ranwel Caputto, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba X5000HUA, Argentina
- Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), CONICET, Haya de la Torre y Medina Allende, Ciudad Universitaria, Córdoba X5000HUA, Argentina
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2
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Kim S, Voth GA. Physical Characterization of Triolein and Implications for Its Role in Lipid Droplet Biogenesis. J Phys Chem B 2021; 125:6874-6888. [PMID: 34139844 DOI: 10.1021/acs.jpcb.1c03559] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Lipid droplets (LDs) are neutral lipid-storing organelles surrounded by a phospholipid (PL) monolayer. At present, how LDs are formed in the endoplasmic reticulum (ER) bilayer is poorly understood. In this study, we present a revised all-atom (AA) triolein (TG) model, the main constituent of the LD core, and characterize its properties in a bilayer membrane to demonstrate the implications of its behavior in LD biogenesis. In bilayer simulations, TG resides at the surface, adopting PL-like conformations (denoted in this work as SURF-TG). Free energy sampling simulation results estimate the barrier for TG relocating from the bilayer surface to the bilayer center to be ∼2 kcal/mol in the absence of an oil lens. SURF-TG is able to modulate membrane properties by increasing PL ordering, decreasing bending modulus, and creating local negative curvature. The other neutral lipid, dioleoyl-glycerol (DAG), also reduces the membrane bending modulus and populates negative curvature regions. A phenomenological coarse-grained (CG) model is also developed to observe larger-scale SURF-TG-mediated membrane deformation. CG simulations confirm that TG nucleates between the bilayer leaflets at a critical concentration when SURF-TG is evenly distributed. However, when one monolayer contains more SURF-TG, the membrane bends toward the other leaflet, followed by TG nucleation if a concentration is higher than the critical threshold. The central conclusion of this study is that SURF-TG is a negative curvature inducer, as well as a membrane modulator. To this end, a model is proposed in which the accumulation of SURF-TG in the luminal leaflet bends the ER bilayer toward the cytosolic side, followed by TG nucleation.
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Affiliation(s)
- Siyoung Kim
- Pritzker School of Molecular Engineering, The University of Chicago, Chicago, Illinois 60637, United States
| | - Gregory A Voth
- Department of Chemistry, Chicago Center for Theoretical Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
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3
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Zulueta Díaz YDLM, Ambroggio EE, Fanani ML. Miltefosine inhibits the membrane remodeling caused by phospholipase action by changing membrane physical properties. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183407. [DOI: 10.1016/j.bbamem.2020.183407] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2020] [Revised: 06/23/2020] [Accepted: 06/29/2020] [Indexed: 01/04/2023]
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4
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Dymond MK. Mammalian phospholipid homeostasis: evidence that membrane curvature elastic stress drives homeoviscous adaptation in vivo. J R Soc Interface 2017; 13:rsif.2016.0228. [PMID: 27534697 DOI: 10.1098/rsif.2016.0228] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Accepted: 07/25/2016] [Indexed: 12/23/2022] Open
Abstract
Several theories of phospholipid homeostasis have postulated that cells regulate the molecular composition of their bilayer membranes, such that a common biophysical membrane parameter is under homeostatic control. Two commonly cited theories are the intrinsic curvature hypothesis, which states that cells control membrane curvature elastic stress, and the theory of homeoviscous adaptation, which postulates cells control acyl chain packing order (membrane order). In this paper, we present evidence from data-driven modelling studies that these two theories correlate in vivo. We estimate the curvature elastic stress of mammalian cells to be 4-7 × 10(-12) N, a value high enough to suggest that in mammalian cells the preservation of membrane order arises through a mechanism where membrane curvature elastic stress is controlled. These results emerge from analysing the molecular contribution of individual phospholipids to both membrane order and curvature elastic stress in nearly 500 cellular compositionally diverse lipidomes. Our model suggests that the de novo synthesis of lipids is the dominant mechanism by which cells control curvature elastic stress and hence membrane order in vivo These results also suggest that cells can increase membrane curvature elastic stress disproportionately to membrane order by incorporating polyunsaturated fatty acids into lipids.
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Affiliation(s)
- Marcus K Dymond
- Division of Chemistry, School of Pharmacy and Biological Sciences, University of Brighton, Brighton BN2 4GL, UK
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5
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Unexpected products of the hypochlorous acid-induced oxidation of oleic acid: A study using high performance thin-layer chromatographyelectrospray ionization mass spectrometry. J Chromatogr A 2016; 1439:89-96. [DOI: 10.1016/j.chroma.2015.11.059] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Revised: 11/08/2015] [Accepted: 11/17/2015] [Indexed: 01/14/2023]
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6
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Membrane lipid compositional sensing by the inducible amphipathic helix of CCT. Biochim Biophys Acta Mol Cell Biol Lipids 2015; 1861:847-861. [PMID: 26747646 DOI: 10.1016/j.bbalip.2015.12.022] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Revised: 12/22/2015] [Accepted: 12/29/2015] [Indexed: 11/21/2022]
Abstract
The amphipathic helical (AH) membrane binding motif is recognized as a major device for lipid compositional sensing. We explore the function and mechanism of sensing by the lipid biosynthetic enzyme, CTP:phosphocholine cytidylyltransferase (CCT). As the regulatory enzyme in phosphatidylcholine (PC) synthesis, CCT contributes to membrane PC homeostasis. CCT directly binds and inserts into the surface of bilayers that are deficient in PC and therefore enriched in lipids that enhance surface charge and/or create lipid packing voids. These two membrane physical properties induce the folding of the CCT M domain into a ≥60 residue AH. Membrane binding activates catalysis by a mechanism that has been partially deciphered. We review the evidence for CCT compositional sensing, and the membrane and protein determinants for lipid selective membrane-interactions. We consider the factors that promote the binding of CCT isoforms to the membranes of the ER, nuclear envelope, or lipid droplets, but exclude CCT from other organelles and the plasma membrane. The CCT sensing mechanism is compared with several other proteins that use an AH motif for membrane compositional sensing. This article is part of a Special Issue entitled: The cellular lipid landscape edited by Tim P. Levine and Anant K. Menon.
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7
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Hague CV, Postle AD, Attard GS, Dymond MK. Cell cycle dependent changes in membrane stored curvature elastic energy: evidence from lipidomic studies. Faraday Discuss 2013; 161:481-97; discussion 563-89. [PMID: 23805754 DOI: 10.1039/c2fd20078c] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
One of the most developed theories of phospholipid homeostasis is the intrinsic curvature hypothesis, which, in broad terms, postulates that cells regulate their lipid composition so as to keep constant the membrane stored curvature elastic energy. The implication of this hypothesis is that lipid composition is determined by a ratio control function consisting of the weighted sum of concentrations of type II lipids in the numerator and the weighted sum of concentrations of Type 0 lipids in the denominator. In previous work we used a data-driven approach, based on lipidomic data from asynchronous cell cultures, to determine a criterion that allows the different lipid species to be assigned to the set of type 0 or of type II lipids, and hence construct a ratio control function that serves as a proxy for the lipid contribution to total membrane stored curvature elastic energy in vivo. Here we apply the curvature elastic energy proxy to the analysis of lipid composition data from synchronous HeLa cells as they traverse the cell cycle. Our analysis suggests HeLa cells modify their membrane stored elastic energy through the cell cycle. In S-phase type 0 lipids are the most abundant, whilst in G2 type II lipids are most abundant. Changes in our proxy for membrane stored elastic energy correlate with membrane curvature dependent processes in the HeLa cell around division, providing some insights into the interplay between the individual lipid and protein contributions to membrane free energy.
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Affiliation(s)
- Charlotte V Hague
- Faculty of Natural and Environmental Sciences, University of Southampton, UK
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8
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Zhan H, Lazaridis T. Inclusion of lateral pressure/curvature stress effects in implicit membrane models. Biophys J 2013; 104:643-54. [PMID: 23442915 DOI: 10.1016/j.bpj.2012.12.022] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2012] [Revised: 12/06/2012] [Accepted: 12/10/2012] [Indexed: 02/06/2023] Open
Abstract
Implicit membrane models usually treat the membrane as a hydrophobic slab and neglect lateral pressure/curvature stress effects. As a result, they cannot distinguish, for example, PE from PC lipids. Here, the implicit membrane model IMM1 is extended to include these effects using a combination of classical thermodynamics and membrane elasticity theory. The proposed model is tested by molecular dynamics simulation of the peptides alamethicin, melittin, cyclotide kalata B1, 18A, and KKpL15. The lateral pressure term stabilizes interfacial binding due to the negative pressure at the hydrocarbon-water interface. In agreement with experiment, increase in the peptide/lipid molar ratio shifts the equilibrium from the interfacial to the transmembrane orientation. Simulations of mixed DOPC/DOPE bilayers show that increase of the DOPE mole fraction in general stabilizes interfacial orientations and destabilizes transmembrane orientations. The extent of the stabilization or destabilization varies depending on the exact position of the peptides. The computational results are in good agreement with experiments.
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Affiliation(s)
- Huan Zhan
- Department of Chemistry, City College of New York/City University of New York, New York, New York, USA
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9
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Dymond MK, Hague CV, Postle AD, Attard GS. An in vivo ratio control mechanism for phospholipid homeostasis: evidence from lipidomic studies. J R Soc Interface 2012; 10:20120854. [PMID: 23256189 DOI: 10.1098/rsif.2012.0854] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
While it is widely accepted that the lipid composition of eukaryotic membranes is under homeostatic control, the mechanisms through which cells sense lipid composition are still the subject of debate. It has been postulated that membrane curvature elastic energy is the membrane property that is regulated by cells, and that lipid composition is maintained by a ratio control function derived from the concentrations of type II and type 0 lipids, weighted appropriately. We assess this proposal by seeking a signature of ratio control in quantified lipid composition data obtained by electrospray ionization mass spectrometry from over 40 independent asynchronous cell populations. Our approach revealed the existence of a universal 'pivot' lipid, which marks the boundary between type 0 lipids and type II lipids, and which is invariant between different cell types or cells grown under different conditions. The presence of such a pivot species is a distinctive signature of the operation in vivo, in human cell lines, of a control function that is consistent with the hypothesis that membrane elastic energy is homeostatically controlled.
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Affiliation(s)
- Marcus K Dymond
- Division of Chemistry, Faculty of Natural and Environmental Sciences, University of Southampton, Southampton SO17 1BJ, UK.
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10
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Selvy PE, Lavieri RR, Lindsley CW, Brown HA. Phospholipase D: enzymology, functionality, and chemical modulation. Chem Rev 2011; 111:6064-119. [PMID: 21936578 PMCID: PMC3233269 DOI: 10.1021/cr200296t] [Citation(s) in RCA: 251] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Paige E Selvy
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee 37064, USA
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11
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Fuchs B, Süss R, Teuber K, Eibisch M, Schiller J. Lipid analysis by thin-layer chromatography--a review of the current state. J Chromatogr A 2010; 1218:2754-74. [PMID: 21167493 DOI: 10.1016/j.chroma.2010.11.066] [Citation(s) in RCA: 206] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2010] [Revised: 11/24/2010] [Accepted: 11/26/2010] [Indexed: 12/15/2022]
Abstract
High-performance thin-layer chromatography (HPTLC) is a widely used, fast and relatively inexpensive method of separating complex mixtures. It is particularly useful for smaller, apolar compounds and offers some advantages over HPLC. This review gives an overview about the special features as well as the problems that have to be considered upon the HPTLC analysis of lipids. The term "lipids" is used here in a broad sense and comprises fatty acids and their derivatives as well as substances related biosynthetically or functionally to these compounds. After a short introduction regarding the stationary phases and the methods how lipids can be visualized on an HPTLC plate, the individual lipid classes will be discussed and the most suitable solvent systems for their separation indicated. The focus will be on lipids that are most abundant in biological systems, i.e. cholesterol and its derivates, glycerides, sphingo- and glycolipids as well as phospholipids. Finally, a nowadays very important topic, the combination between HPTLC and mass spectrometric (MS) detection methods will be discussed. It will be shown that this is a very powerful method to investigate the identities of the HPTLC spots in more detail than by the use of common staining methods. Future aspects of HPTLC in the lipid field will be also discussed.
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Affiliation(s)
- Beate Fuchs
- University of Leipzig, Medical Department, Institute of Medical Physics and Biophysics, Härtelstr. 16/18, D-04107 Leipzig, Germany
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12
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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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13
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Miller D, Booth PJ. The use of isothermal titration calorimetry to study multidrug transport proteins in liposomes. Methods Mol Biol 2010; 606:233-245. [PMID: 20013401 DOI: 10.1007/978-1-60761-447-0_17] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Biophysical measurements of multidrug transporters in vitro can often be of limited relevance to the natural in vivo behavior. In particular, the properties of transporters when removed from their native bilayer and solubilized in detergents or lipids can differ significantly from their in vivo properties, reducing the value of in vitro measurements for the design of antagonists to the transporters. This problem can be addressed by studying the transport protein in liposomes in which the properties of the liposome bilayer are altered through systematic changes in lipid composition. Isothermal titration calorimetry can be used to determine the properties of the lipid-reconstituted protein in bilayers of different lipid compositions as well as to quantify the percentage recovery of functional protein in different lipids. Both these measurements lead to an accurate analysis of substrate binding activity. The approach is illustrated here for the small multidrug transport protein, EmrE from Escherichia coli. The percentage of functional EmrE successfully reconstituted into liposome depends on lipid composition. Differences in ligand binding and subtle differences in the secondary structure also occur in different lipid compositions.
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Affiliation(s)
- David Miller
- Department of Biochemistry, University of Bristol, UK
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14
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García-Pacios M, Collado MI, Busto JV, Sot J, Alonso A, Arrondo JLR, Goñi FM. Sphingosine-1-phosphate as an amphipathic metabolite: its properties in aqueous and membrane environments. Biophys J 2009; 97:1398-407. [PMID: 19720028 DOI: 10.1016/j.bpj.2009.07.001] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2009] [Revised: 07/01/2009] [Accepted: 07/01/2009] [Indexed: 12/22/2022] Open
Abstract
Sphingosine-1-phosphate (S1P) is currently considered to be an important signaling molecule in cell metabolism. We studied a number of relevant biophysical properties of S1P, using mainly Langmuir balance, differential scanning calorimetry, (31)P-NMR, and infrared (IR) spectroscopy. We found that, at variance with other, structurally related sphingolipids that are very hydrophobic, S1P may occur in either an aqueous dispersion or a bilayer environment. S1P behaves in aqueous media as a soluble amphiphile, with a critical micelle concentration of approximately 12 muM. Micelles give rise to larger aggregates (in the micrometer size range) at and above a 1 mM concentration. The aggregates display a thermotropic transition at approximately 60 degrees C, presumably due to the formation of smaller structures at the higher temperatures. S1P can also be studied in mixtures with phospholipids. Studies with dielaidoylphosphatidylethanolamine (DEPE) or deuterated dipalmitoylphosphatidylcholine (DPPC) show that S1P modifies the gel-fluid transition of the glycerophospholipids, shifting it to lower temperatures and decreasing the transition enthalpy. Low (<10 mol %) concentrations of S1P also have a clear effect on the lamellar-to-inverted hexagonal transition of DEPE, i.e., they increase the transition temperature and stabilize the lamellar versus the inverted hexagonal phase. IR spectroscopy of natural S1P mixed with deuterated DPPC allows the independent observation of transitions in each molecule, and demonstrates the existence of molecular interactions between S1P and the phospholipid at the polar headgroup level that lead to increased hydration of the carbonyl group. The combination of calorimetric, IR, and NMR data allowed the construction of a temperature-composition diagram ("partial phase diagram") to facilitate a comparative study of the properties of S1P and other related lipids (ceramide and sphingosine) in membranes. In conclusion, two important differences between S1P and ceramide are that S1P stabilizes the lipid bilayer structure, and physiologically relevant concentrations of S1P can exist dispersed in the cytosol.
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Miller D, Charalambous K, Rotem D, Schuldiner S, Curnow P, Booth PJ. In vitro Unfolding and Refolding of the Small Multidrug Transporter EmrE. J Mol Biol 2009; 393:815-32. [DOI: 10.1016/j.jmb.2009.08.039] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2009] [Revised: 08/12/2009] [Accepted: 08/14/2009] [Indexed: 11/28/2022]
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Atkinson J, Epand RF, Epand RM. Tocopherols and tocotrienols in membranes: a critical review. Free Radic Biol Med 2008; 44:739-64. [PMID: 18160049 DOI: 10.1016/j.freeradbiomed.2007.11.010] [Citation(s) in RCA: 190] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/04/2007] [Revised: 11/09/2007] [Accepted: 11/12/2007] [Indexed: 12/14/2022]
Abstract
The familiar role of tocols (tocopherols and tocotrienols) as lipid-soluble chain-terminating inhibitors of lipid peroxidation is currently in the midst of a reinterpretation. New biological activities have been described for tocols that apparently are not dependent on their well-established antioxidant behaviour. These activities could well be real, but there remain large gaps in our understanding of the behaviour of tocols in membranes, especially when it comes to the alpha-, beta-, gamma-, delta-chroman methylation patterns and the seemingly special nature of tocotrienols. It is inappropriate to make conclusions and develop models based on in vivo (or cell culture) results with reference to in vitro measurements of antioxidant activity. When present in biological membranes, tocols will experience a large variation in the local composition of phospholipids and the presence of neutral lipids such as cholesterol, both of which would be expected to change the efficiency of antioxidant action. It is likely that tocols are not homogeneously dispersed in a membrane, but it is still not known whether any specific combination of lipid head group and acyl chains are conferred special protection from peroxidation, nor do we currently appreciate the structural role that tocols play in membranes. Tocols may enhance curvature stress or counteract similar stresses generated by other lipids such as lysolipids. This review will outline what is known about the location and behaviour of tocols in phospholipid bilayers. We will draw mainly from the biophysical literature, but will attempt to extend the discussion to biologically relevant phenomena when appropriate. We hope that it will assist researchers when designing new experiments and when critically assessing the results, in turn providing a more thorough understanding of the biochemistry of tocols.
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Affiliation(s)
- Jeffrey Atkinson
- Department of Chemistry and Centre for Biotechnology, Brock University, 500 Glenridge Avenue, St. Catharines, Ontario, Canada.
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17
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Ces O, Mulet X. Physical coupling between lipids and proteins: a paradigm for cellular control. ACTA ACUST UNITED AC 2006. [DOI: 10.1002/sita.200500079] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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18
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Andresen TL, Jensen SS, Jørgensen K. Advanced strategies in liposomal cancer therapy: problems and prospects of active and tumor specific drug release. Prog Lipid Res 2005; 44:68-97. [PMID: 15748655 DOI: 10.1016/j.plipres.2004.12.001] [Citation(s) in RCA: 400] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Tumor specific drug delivery has become increasingly interesting in cancer therapy, as the use of chemotherapeutics is often limited due to severe side effects. Conventional drug delivery systems have shown low efficiency and a continuous search for more advanced drug delivery principles is therefore of great importance. In the first part of this review, we present current strategies in the drug delivery field, focusing on site-specific triggered drug release from liposomes in cancerous tissue. Currently marketed drug delivery systems lack the ability to actively release the carried drug and rely on passive diffusion or slow non-specific degradation of the liposomal carrier. To obtain elevated tumor-to-normal tissue drug ratios, it is important to develop drug delivery strategies where the liposomal carriers are actively degraded specifically in the tumor tissue. Many promising strategies have emerged ranging from externally triggered light- and thermosensitive liposomes to receptor targeted, pH- and enzymatically triggered liposomes relying on an endogenous trigger mechanism in the cancerous tissue. However, even though several of these strategies were introduced three decades ago, none of them have yet led to marketed drugs and are still far from achieving this goal. The most advanced and prospective technologies are probably the prodrug strategies where non-toxic drugs are carried and activated specifically in the malignant tissue by overexpressed enzymes. In the second part of this paper, we review our own work, exploiting secretory phospholipase A2 as a site-specific trigger and prodrug activator in cancer therapy. We present novel prodrug lipids together with biophysical investigations of liposome systems, constituted by these new lipids and demonstrate their degradability by secretory phospholipase A2. We furthermore give examples of the biological performance of the enzymatically degradable liposomes as advanced drug delivery systems.
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Affiliation(s)
- Thomas L Andresen
- Department of Chemistry, Technical University of Denmark, Building 207, DK-2800 Lyngby, Denmark.
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19
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van den Brink-van der Laan E, Killian JA, de Kruijff B. Nonbilayer lipids affect peripheral and integral membrane proteins via changes in the lateral pressure profile. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2004; 1666:275-88. [PMID: 15519321 DOI: 10.1016/j.bbamem.2004.06.010] [Citation(s) in RCA: 330] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2004] [Revised: 06/16/2004] [Accepted: 06/24/2004] [Indexed: 11/23/2022]
Abstract
Nonbilayer lipids can be defined as cone-shaped lipids with a preference for nonbilayer structures with a negative curvature, such as the hexagonal phase. All membranes contain these lipids in large amounts. Yet, the lipids in biological membranes are organized in a bilayer. This leads to the question: what is the physiological role of nonbilayer lipids? Different models are discussed in this review, with a focus on the lateral pressure profile within the membrane. Based on this lateral pressure model, predictions can be made for the effect of nonbilayer lipids on peripheral and integral membrane proteins. Recent data on the catalytic domain of Leader Peptidase and the potassium channel KcsA are discussed in relation to these predictions and in relation to the different models on the function of nonbilayer lipids. The data suggest a general mechanism for the interaction between nonbilayer lipids and membrane proteins via the membrane lateral pressure.
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Affiliation(s)
- Els van den Brink-van der Laan
- Department Biochemistry of Membranes, Centre for Biomembranes and Lipid Enzymology, Institute of Biomembranes, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands.
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Davidsen J, Jørgensen K, Andresen TL, Mouritsen OG. Secreted phospholipase A(2) as a new enzymatic trigger mechanism for localised liposomal drug release and absorption in diseased tissue. BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1609:95-101. [PMID: 12507763 DOI: 10.1016/s0005-2736(02)00659-4] [Citation(s) in RCA: 116] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Polymer-coated liposomes can act as versatile drug-delivery systems due to long vascular circulation time and passive targeting by leaky blood vessels in diseased tissue. We present an experimental model system illustrating a new principle for improved and programmable drug-delivery, which takes advantage of an elevated activity of secretory phospholipase A(2) (PLA(2)) at the diseased target tissue. The secretory PLA(2) hydrolyses a lipid-based proenhancer in the carrier liposome, producing lyso-phospholipids and free fatty acids, which are shown in a synergistic way to lead to enhanced liposome destabilization and drug release at the same time as the permeability of the target membrane is enhanced. Moreover, the proposed system can be made thermosensitive and offers a rational way for developing smart liposome-based drug delivery systems. This can be achieved by incorporating specific lipid-based proenhancers or prodestabilisers into the liposome carrier, which automatically becomes activated by PLA(2) only at the diseased target sites, such as inflamed or cancerous tissue.
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Affiliation(s)
- Jesper Davidsen
- Department of Pharmaceutics, The Royal Danish School of Pharmacy, Copenhagen, Denmark
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Bodennec J, Pelled D, Riebeling C, Trajkovic S, Futerman AH. Phosphatidylcholine synthesis is elevated in neuronal models of Gaucher disease due to direct activation of CTP:phosphocholine cytidylyltransferase by glucosylceramide. FASEB J 2002; 16:1814-6. [PMID: 12223447 DOI: 10.1096/fj.02-0149fje] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Glucosylceramide (GlcCer) accumulates in the inherited metabolic disorder, Gaucher disease, because of the defective activity of lysosomal glucocerebrosidase. We previously demonstrated that upon GlcCer accumulation, cultured hippocampal neurons exhibit modified growth patterns, altered endoplasmic reticulum density, and altered calcium release from intracellular stores. We here examined the relationship between GlcCer accumulation and phospholipid synthesis. After treatment of neurons with an active site-directed inhibitor of glucocerebrosidase, or in neurons obtained from a mouse model of Gaucher disease, [14C]methyl choline incorporation into [14C]phosphatidylcholine ([14C]PC) and [14C]sphingomyelin was elevated, as were [14C]CDP-choline levels, suggesting that CTP:phosphocholine cytidylyltransferase (CCT) is activated. Indeed, CCT activity was elevated in neurons that had accumulated GlcCer. GlcCer, but not galactosylceramide (GalCer), stimulated CCT activity in rat brain homogenates, and significantly higher levels of CCT were membrane associated in cortical homogenates from a mouse model of Gaucher disease compared with wild-type mice. Because CCT mRNA and protein levels were unaltered in either neurons or brain tissue that had accumulated GlcCer, it appeared likely that GlcCer activates CCT by a post-translational mechanism. This was verified by examination of the effect of GlcCer on CCT purified about 1200-fold from rat brain. GlcCer stimulated CCT activity, with stimulation observed at levels as low as 2.5 mol% and with maximal activation reached at 10 mol%. In contrast, GalCer had no effect. Together, these data demonstrate that GlcCer directly activates CCT, which results in elevated PC synthesis, which may account for some of the changes in growth rates observed upon neuronal GlcCer accumulation.
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Affiliation(s)
- Jacques Bodennec
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
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22
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Rilfors L, Lindblom G. Regulation of lipid composition in biological membranes—biophysical studies of lipids and lipid synthesizing enzymes. Colloids Surf B Biointerfaces 2002. [DOI: 10.1016/s0927-7765(01)00310-1] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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23
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Armstrong DL, Borchardt DB, Zidovetzki R. Synergistic perturbation of phosphatidylcholine/sphingomyelin bilayers by diacylglycerol and cholesterol. Biochem Biophys Res Commun 2002; 296:806-12. [PMID: 12200119 DOI: 10.1016/s0006-291x(02)00946-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The perturbations induced by second messenger diacylglycerols (DAGs) into bovine brain phosphatidylcholine (BBPC) bilayers in the presence or absence of bovine brain sphingomyelin (SM) and/or cholesterol were studied by (2)H NMR. Addition of 15 mol% DAG to BBPC bilayers did not induce non-bilayer lipid phases in the temperature range 30-60 degrees C. Similar measurements performed in the presence of cholesterol revealed that cholesterol progressively destabilizes PC bilayers with respect to DAG-induced perturbations. Thus, at 40 mol% cholesterol, addition of 15 mol% DAG induced the formation of non-bilayer (isotropic and inverted hexagonal) phases at 60 degrees C. Whereas some lateral separation of the bilayers into domains of different cholesterol contents was observed in BBPC/cholesterol membranes, such a lateral heterogeneity was greatly facilitated by the addition of SM. Since both a tendency to form non-bilayer lipid phases and lateral heterogeneity of the membranes are associated with increased activation of a number of membrane-associated enzymes, our results suggest that SM- and cholesterol-enriched regions of biological membranes (rafts) provide an environment with increased sensitivity to the generation of lipid second messengers and modified transmembrane signal transduction properties.
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Affiliation(s)
- Don L Armstrong
- Department of Cell Biology and Neuroscience, College of Natural and Agricultural Sciences, University of California, 1306/1303 Spieth, Riverside, CA 92521, USA
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24
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Ruiz-Argüello MB, Veiga MP, Arrondo JLR, Goñi FM, Alonso A. Sphingomyelinase cleavage of sphingomyelin in pure and mixed lipid membranes. Influence of the physical state of the sphingolipid. Chem Phys Lipids 2002; 114:11-20. [PMID: 11841822 DOI: 10.1016/s0009-3084(01)00195-5] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Sphingomyelin hydrolysis by sphingomyelinase is essential in regulating membrane levels of ceramide, a well-known metabolic signal. Since natural sphingomyelins have a gel-to-fluid transition temperature in the range of the physiological temperatures of mammals and birds, it is important to understand the influence of the physical state of the lipid on the enzyme activity. With that aim, large unilamellar vesicles consisting of pure egg sphingomyelin (gel-to-fluid crystalline transition temperature ca. 39 degrees C) were treated with sphingomyelinase in the temperature range 10-70 degrees C. The vesicles were also examined by differential scanning calorimetry (DSC). Shingomyelinase was active on pure sphingomyelin bilayers, leading to concomitant lipid hydrolysis, vesicle aggregation, and leakage of aqueous liposomal contents. Enzyme activity was found to be much higher when the substrate was in the fluid than when it was in the gel state. Sphingomyelinase activity was found to exhibit lag times, followed by bursts of activity. Lag times decreased markedly when the substrate went from the gel to the fluid state. When egg phosphatidylcholine, or egg phosphatidylethanolamine were included in the bilayer composition together with sphingomyelin, sphingomyelinase activity at 37 degrees C, that was negligible for the pure sphingolipid bilayers, was seen to increase with the proportion of glycerophospholipid, while the latency times became progressively shorter. A DSC study of the mixed-lipid vesicles revealed that both phosphatidylcholine and phosphatidyletanolamine decreased in a dose-dependent way the transition temperature of sphingomyelin. Thus, as those glycerophospholipids were added to the membrane composition, the proportion of sphingomyelin in the fluid state at 37 degrees C increased accordingly, in this way becoming amenable to rapid hydrolysis by the enzyme. Thus sphingomyelinase requires the substrate in bilayer form to be in the fluid state, irrespective of whether this is achieved through a thermotropic transition or by modulating bilayer composition.
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Affiliation(s)
- M Begoña Ruiz-Argüello
- Unidad de Biofísica (CSIC-UPV/EHU), and Departamento de Bioquímica, Universidad del Paijs Vasco, Apartado 644, 48080, Bilbao, Spain
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25
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Sugar IP, Mizuno NK, Momsen MM, Brockman HL. Lipid lateral organization in fluid interfaces controls the rate of colipase association. Biophys J 2001; 81:3387-97. [PMID: 11721001 PMCID: PMC1301795 DOI: 10.1016/s0006-3495(01)75971-1] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Colipase, a cofactor of pancreatic triacylglycerol lipase, binds to surfaces of lipolysis reactants, like fatty acid and diacylglycerol, but not to the nonsubstrate phosphatidylcholine. The initial rate of colipase binding to fluid, single-phase lipid monolayers was used to characterize the interfacial requirements for its adsorption. Colipase adsorption rates to phosphatidylcholine/reactant mixed monolayers depended strongly on lipid composition and packing. Paradoxically, reactants lowered colipase adsorption rates only if phosphatidylcholine was present. This suggests that interactions between phosphatidylcholine and reactants create dynamic complexes that impede colipase adsorption. Complex formation was independently verified by physical measurements. Colipase binding rate depends nonlinearly on the two-dimensional concentration of phosphatidylcholine. This suggests that binding is initiated by a cluster of nonexcluded surface sites smaller than the area occupied by a bound colipase. Binding rates are mathematically consistent with this mechanism. Moreover, for each phosphatidylcholine-reactant pair, the complex area obtained from the analysis of binding rates agrees well with the independently measured collapse area of the complex. The dynamic complexes between phosphatidylcholine and lipids, like diacylglycerols, exist independently of the presence of colipase. Thus, our results suggest that lipid complexes may regulate the fluxes of other proteins to membranes during, for example, lipid-mediated signaling events in cells.
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Affiliation(s)
- I P Sugar
- Mt. Sinai School of Medicine, Department of Biomathematical Science, New York, New York 10029, USA
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26
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Abstract
Phospholipases are a diverse series of enzymes that hydrolyze phospholipids. Multiple forms of phospholipases D, C, and A have been characterized in plants. These enzymes are involved in a broad range of functions in cellular regulation, lipid metabolism, and membrane remodeling. In recent years, increasing attention has been paid to the many roles of phospholipases in signal transduction. This review highlights recent developments in the understanding of biochemical, molecular biological, and functional aspects of various phospholipases in plants.
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Affiliation(s)
- Xuemin Wang
- Department of Biochemistry, Kansas State University, Willard Hall, Manhattan, Kansas 66506; e-mail:
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27
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Villar AV, Goñi FM, Alonso A. Diacylglycerol effects on phosphatidylinositol-specific phospholipase C activity and vesicle fusion. FEBS Lett 2001; 494:117-20. [PMID: 11297746 DOI: 10.1016/s0014-5793(01)02333-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Diacylglycerol increased the hydrolytic activity of phosphatidylinositol-specific phospholipase C on large unilamellar vesicles containing 5-40% phosphatidylinositol. Moreover, diacylglycerol increased the rate and extent of vesicle fusion (contents mixing) induced by the enzyme. Kinetic studies of intervesicular lipid mixing revealed that fusion was limited by the frequency of contacts involving two diacylglycerol-rich domains.
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Affiliation(s)
- A V Villar
- Unidad de Biofísica (CSIC-UPV/EHU), and Departamento de Bioquímica, Universidad del País Vasco, Aptdo. 644, 48080, Bilbao, Spain
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28
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Attard GS, Templer RH, Smith WS, Hunt AN, Jackowski S. Modulation of CTP:phosphocholine cytidylyltransferase by membrane curvature elastic stress. Proc Natl Acad Sci U S A 2000; 97:9032-6. [PMID: 10908674 PMCID: PMC16816 DOI: 10.1073/pnas.160260697] [Citation(s) in RCA: 204] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/1999] [Accepted: 06/07/2000] [Indexed: 11/18/2022] Open
Abstract
The activity of CTP:phosphocholine cytidylyltransferase, a rate-limiting enzyme in phosphatidylcholine biosynthesis, is modulated by its interaction with lipid bilayers [Kent, C. (1997) Biochim. Biophys. Acta 1348, 79-90]. Its regulation is of central importance in the maintenance of membrane lipid homeostasis. Here we show evidence that the stored curvature elastic stress in the lipid membrane's monolayer modulates the activity of CTP:phosphocholine cytidylyltransferase. Our results show how a purely physical feedback signal could play a key role in the control of membrane lipid synthesis.
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Affiliation(s)
- G S Attard
- Departments of Chemistry and Child Health, University of Southampton, Southampton SO17 1BJ, United Kingdom.
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29
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Wang X. Multiple forms of phospholipase D in plants: the gene family, catalytic and regulatory properties, and cellular functions. Prog Lipid Res 2000; 39:109-49. [PMID: 10775762 DOI: 10.1016/s0163-7827(00)00002-3] [Citation(s) in RCA: 164] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Multiple Phospholipase D (PLD) genes have been identified in plants and encode isoforms with distinct regulatory and catalytic properties. Elucidation of the genetic and biochemical heterogeneity has provided important clues as to the regulation and function of this family of enzymes. Polyphosphoinositides, Ca(2+), and G-proteins are possible cellular regulators for PLD activation. PLD-mediated hydrolysis of membrane lipids increases in response to various stresses. Recent studies suggest that PLD plays a role in the signaling and production of hormones involved in plant stress responses.
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Affiliation(s)
- X Wang
- Department of Biochemistry, Kansas State University, Manhattan 66506, USA.
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30
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Buckland AG, Wilton DC. Anionic phospholipids, interfacial binding and the regulation of cell functions. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1483:199-216. [PMID: 10634937 DOI: 10.1016/s1388-1981(99)00188-2] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- A G Buckland
- Division of Biochemistry and Molecular Biology, School of Biological Sciences, University of Southampton, Bassett Crescent East, Southampton, UK
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31
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Pappan K, Wang X. Molecular and biochemical properties and physiological roles of plant phospholipase D. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1439:151-66. [PMID: 10425392 DOI: 10.1016/s1388-1981(99)00091-8] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Recent advances have thrust the study of plant phospholipase D (PLD) into the molecular era. This review will highlight some of the recent progress made in elucidating the molecular and biochemical nature of plant PLDs as well as their roles in plant physiology.
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Affiliation(s)
- K Pappan
- Department of Biochemistry, Kansas State University, Manhattan, KS 66506, USA
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32
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Affiliation(s)
- X Wang
- Department of Biochemistry, Kansas State University, Manhattan, Kansas 66506, USA
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33
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Rilfors L, Niemi A, Haraldsson S, Edwards K, Andersson AS, Dowhan W. Reconstituted phosphatidylserine synthase from Escherichia coli is activated by anionic phospholipids and micelle-forming amphiphiles. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1438:281-94. [PMID: 10320811 DOI: 10.1016/s1388-1981(99)00060-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
The activity of phosphatidylserine (PS) synthase (CDP-1, 2-diacyl-sn-glycerol: l-serine O-phosphatidyltransferase, EC 2.7.8. 8) from Escherichia coli was studied after reconstitution with lipid vesicles of various compositions. PS synthase exhibited practically no activity in the absence of a detergent and with the substrate CDP-diacylglycerol (CDP-DAG) present only in the lipid vesicles. Inclusion of octylglucoside (OG) in the assay mixture increased the activity 20- to 1000-fold, the degree of activation depending on the lipid composition of the vesicles. Inclusion of additional CDP-DAG in the assay mixture increased the activity 5- to 25-fold. When the fraction of phosphatidylglycerol (PG) was increased from 15 to 100 mol% in the vesicles the activity increased 10-fold using the assay mixture containing OG. The highest activities were exhibited with the anionic lipids synthesized by E. coli, namely PG, diphosphatidylglycerol (DPG), and phosphatidic acid, while phosphatidylinositol gave a lower activity. Cryotransmission electron microscopy showed that transformation of the vesicles to micelles brings about an activation of the enzyme that is proportional to the degree of micellization. Thus, the activity of PS synthase is modulated by the lipid aggregate structure and by the fraction and type of anionic phospholipid in the aggregates. The increase in the activity caused by PG and DPG is physiologically relevant; it may be part of a regulatory mechanism that keeps the balance between phosphatidylethanolamine, and the sum of PG and DPG, nearly constant in wild-type E. coli cells.
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Affiliation(s)
- L Rilfors
- Department of Chemistry, Biophysical Chemistry, Umeå University, SE-901 87, Umeå, Sweden.
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34
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Williams EE, May BD, Stillwell W, Jenski LJ. Docosahexaenoic acid (DHA) alters the phospholipid molecular species composition of membranous vesicles exfoliated from the surface of a murine leukemia cell line. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1418:185-96. [PMID: 10209223 DOI: 10.1016/s0005-2736(99)00032-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Previously, we presented evidence that the vesicles routinely exfoliated from the surface of T27A tumor cells arise from vesicle-forming regions of the plasma membrane and possess a set of lateral microdomains distinct from those of the plasma membrane as a whole. We also showed that docosahexaenoic acid (DHA, or 22:6n-3), a fatty acyl chain known to alter microdomain structure in model membranes, also alters the structure and composition of exfoliated vesicles, implying a DHA-induced change in microdomain structure on the cell surface. In this report we show that enrichment of the cells with DHA reverses some of the characteristic differences in composition between the parent plasma membrane and shed microdomain vesicles, but does not alter their phospholipid class composition. In untreated cells, DHA-containing species were found to be a much greater proportion of the total phosphatidylethanolamine (PE) pool than the total phosphatidylcholine (PC) pool in both the plasma membrane and the shed vesicles. After DHA treatment, the proportion of DHA-containing species in the PE and PC pools of the plasma membrane were elevated, and unlike in untreated cells, their proportions were equal in the two pools. In the vesicles shed from DHA-loaded cells, the proportion of DHA-containing species of PE was the same as in the plasma membrane. However, the proportion of DHA-containing species of PC in the vesicles (0.089) was much lower than that found in the plasma membrane (0.194), and was relatively devoid of species with 16-carbon acyl components. These data suggested that DHA-containing species of PC, particularly those having a 16-carbon chain in the sn-1 position, were preferentially retained in the plasma membrane. The data can be interpreted as indicating that DHA induces a restructuring of lateral microdomains on the surface of living cells similar to that predicted by its behavior in model membranes.
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Affiliation(s)
- E E Williams
- Department of Biology, Indiana University/Purdue University at Indianapolis, 723 West Michigan Street, Indianapolis, IN 46202, USA.
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35
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Hirche F, Ulbrich-Hofmann R. The interfacial pressure is an important parameter for the rate of phospholipase D catalyzed reactions in emulsion systems. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1436:383-9. [PMID: 9989269 DOI: 10.1016/s0005-2760(98)00143-x] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Phospholipase D (PLD) is widely used for the transformation of phospholipids, which is preferably performed in aqueous-organic emulsion systems. The influence of the organic solvent on the reaction rates has been studied on the hydrolysis of phosphatidylcholine (PC) and its transesterification with glycerol by two types of PLD (cabbage and Streptomyces sp.). The initial rates determined by quantitative HPTLC show great differences in dependence on the solvent used with a similar tendency for both reactions and both PLDs. Since the polymorphism of the PC aggregates was assumed to be responsible for these effects, the critical concentration of micelle formation, the size of the aggregates, the water content of the organic phase, and the interfacial tension were determined in the different reaction systems. As result the interfacial pressure in the reaction systems influencing the package density of the PC aggregates is suggested to regulate the enzymatic activity.
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Affiliation(s)
- F Hirche
- Department of Biochemistry/Biotechnology, Martin Luther University Halle-Wittenberg, Germany
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36
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Abstract
1. 1,2-Diacyl-sn-glycerols (DAG) are minor components of cell membranes (about 1 mole% of the lipids) and yet they are potent regulators of both the physical properties of the lipid bilayer and the catalytic behaviour of several membrane-related enzymes. 2. In the pure state DAG's present a considerable polymorphism, with several crystalline phases in addition to the neat fluid phase. The most stable crystalline phase is the so-called beta' phase, a monoclinic crystalline form with orthorhombic perpendicular subcell chain packing, in which both acyl chains lie parallel to each other in a hairpinlike configuration about the sn-1 and sn-2 glycerol carbon atoms. The molecules are organized in a bilayer, with the glycerol backbone roughly parallel to the plane of the bilayer, and the acyl chains tilted at approximately 60 degrees with respect to that plane. Acyl chain unsaturation, and particularly a single cis unsaturation, impairs chain packing in mixed-chain DAG's, and this results in an increased number of metastable crystalline phases. 3. DAG's mix with phospholipids in fluid bilayers when their melting temperature is below or close enough to the melting temperature of the bilayer system. When incorporated in phospholipid bilayers, the conformation of DAG is such that the glycerol backbone is nearly perpendicular to the bilayer, with the sn-1 chain extending from the glycerol Cl carbon into the hydrophobic matrix of the bilayer and the sn-2 chain first extending parallel to the bilayer surface, then making a 90 degrees bend at the position of the sn-1 carbonyl to become parallel to the sn-1 chain. DAG's are located in phospholipid bilayers about two CH2 units deeper than the adjacent phospholipids. DAG's mix nonideally with phospholipids, giving rise to in-plane separations of DAG-rich and -poor domains, even in the fluid state. DAG molecules also increase the separation between phospholipid headgroups, and decrease the hydration of the bilayer surface. Also, because the transversal section of the DAG headgroup is small when compared to that of the acyl chains, DAG favours the (negative) curvature of the lipid monolayers, and DAG-phospholipid mixtures tend to convert into inverted nonlamellar hexagonal or cubic phases. 4. A number of membrane enzyme activities are modulated (activated) by DAG, most notably protein kinase C, phospholipases and other enzymes of lipid metabolism. Protein kinase C activation (and perhaps that of other enzymes as well) occurs as the combined result of a number of DAG-induced modifications of lipid bilayers that include: changes in lipid headgroup conformation, interspacing and hydration, changes in the bilayer propensity to form inverted nonlamellar phases, and lateral phase separations of DAG-rich and -poor domains. Among the DAG-activated enzymes, phospholipases C show the peculiarity of yielding the activator DAG as their reaction product, and this allows the self-induced transition from a low- to a high-activity status. 5. DAG's induce or enhance membrane fusion in a number of ways, mainly through partial dehydration of the bilayer surface, increase in lipid monolayer curvature and perhaps lateral phase separation. DAG-increased fusion rates have been demonstrated in several instances of cation-induced fusion of model membranes, as well as in Ca(2+)-induced fusion of chromaffin granules with plasma membrane vesicles. Also phospholipase C has been shown to induce vesicle aggregation and fusion through the catalytic generation of DAG in the bilayers. A rather general property of DAG is that it promotes vesicular or interparticle aggregation. 6. In the living cell, DAG is often generated through phospholipid degradation in response to an extracellular agonist binding a specific receptor in the cell surface. DAG is said to act as an intracellular second messenger. (ABSTRACT TRUNCATED)
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Affiliation(s)
- F M Goñi
- Departamento de Bioquímica, Universidad del País Vasco, Bilbao, Spain
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37
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Abstract
Non-lamellar-forming lipids play an important role in determining the physical properties of membranes. They affect the activity of membrane proteins and peptides. In addition, peptides which lyse membranes as well as those which promote membrane fusion facilitate the formation of non-lamellar phases, either micelles, cubic or hexagonal phases. The relationship of these diverse effects on membrane curvature is discussed in relation to the function of certain peptides and proteins. Specific examples of ionophoric peptides, cytotoxic peptides and viral fusion peptides are given. In addition, we compare the modulation of the rate of photoisomerisation of an integral membrane protein, rhodopsin, by non-lamellar-forming lipids with the effects of these lipids on an amphitropic protein, protein kinase C. Among these diverse systems it is frequently observed that the modulation of biological activity can be described in terms of the effect of the peptide or protein on the relative stability of lamellar and non-lamellar structures.
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Affiliation(s)
- R M Epand
- Department of Biochemistry, McMaster University Health Sciences Centre, Hamilton, Ont. L8N 3Z5, Canada.
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38
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Chapter 7 Membrane Properties and the Activation of Protein Kinase C and Phospholipase A2. CURRENT TOPICS IN MEMBRANES 1997. [DOI: 10.1016/s0070-2161(08)60211-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
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