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Selectivity of mTOR-Phosphatidic Acid Interactions Is Driven by Acyl Chain Structure and Cholesterol. Cells 2021; 11:cells11010119. [PMID: 35011681 PMCID: PMC8750377 DOI: 10.3390/cells11010119] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Revised: 12/24/2021] [Accepted: 12/27/2021] [Indexed: 11/24/2022] Open
Abstract
The need to gain insights into the molecular details of peripheral membrane proteins’ specificity towards phosphatidic acid (PA) is undeniable. The variety of PA species classified in terms of acyl chain length and saturation translates into a complicated, enigmatic network of functional effects that exert a critical influence on cell physiology. As a consequence, numerous studies on the importance of phosphatidic acid in human diseases have been conducted in recent years. One of the key proteins in this context is mTOR, considered to be the most important cellular sensor of essential nutrients while regulating cell proliferation, and which also appears to require PA to build stable and active complexes. Here, we investigated the specific recognition of three physiologically important PA species by the mTOR FRB domain in the presence or absence of cholesterol in targeted membranes. Using a broad range of methods based on model lipid membrane systems, we elucidated how the length and saturation of PA acyl chains influence specific binding of the mTOR FRB domain to the membrane. We also discovered that cholesterol exerts a strong modulatory effect on PA-FRB recognition. Our data provide insight into the molecular details of some physiological effects reported previously and reveal novel mechanisms of fine-tuning the signaling cascades dependent on PA.
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2
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Liposomes Loaded with Unsaponifiable Matter from Amaranthus hypochondriacus as a Source of Squalene and Carrying Soybean Lunasin Inhibited Melanoma Cells. NANOMATERIALS 2021; 11:nano11081960. [PMID: 34443791 PMCID: PMC8397957 DOI: 10.3390/nano11081960] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/27/2021] [Revised: 07/23/2021] [Accepted: 07/23/2021] [Indexed: 02/06/2023]
Abstract
Amaranthus hypochondriacus is a source of molecules with reported health benefits such as antioxidant activity and cancer prevention. The objective of this research was to optimize the conditions for preparing a liposome formulation using amaranth unsaponifiable matter as a source of squalene in order to minimize the particle size and to maximize the encapsulation efficiency of liposomes for carrying and delivering soybean lunasin into melanoma cell lines. Amaranth oil was extracted using supercritical dioxide carbon extraction (55.2 MPa pressure, 80 °C temperature, solvent (CO2)-to-feed (oil) ratio of 20). The extracted oil from amaranth was used to obtain the unsaponifiable enriched content of squalene, which was incorporated into liposomes. A Box–Behnken response surface methodology design was used to optimize the liposome formulation containing the unsaponifiable matter, once liposomes were optimized. Soybean lunasin was loaded into the liposomes and tested on A-375 and B16-F10 melanoma cells. The squalene concentration in the extracted oil was 36.64 ± 0.64 g/ 100 g of oil. The particle size in liposomes was between 115.8 and 163.1 nm; the squalene encapsulation efficiency ranged from 33.14% to 76.08%. The optimized liposome formulation contained 15.27 mg of phospholipids and 1.1 mg of unsaponifiable matter. Cell viability was affected by the liposome formulation with a half-maximum inhibitory concentration (IC50) equivalent to 225 μM in B16-F10 and 215 μM in A-375. The liposomes formulated with lunasin achieved 82.14 ± 3.34% lunasin encapsulation efficiency and improved efficacy by decreasing lunasin IC50 by 31.81% in B16-F10 and by 41.89% in A-375 compared with unencapsulated lunasin.
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3
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Clapis JR, Fan MJ, Kovarik ML. Supported bilayer membranes for reducing cell adhesion in microfluidic devices. ANALYTICAL METHODS : ADVANCING METHODS AND APPLICATIONS 2021; 13:1535-1540. [PMID: 33690748 DOI: 10.1039/d0ay01992e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The high surface area-to-volume ratio of microfluidic channels makes them susceptible to fouling and clogging when used for biological analyses, including cell-based assays. We evaluated the role of electrostatic and van der Waals interactions in cell adhesion in PDMS microchannels coated with supported lipid bilayers and identified conditions that resulted in minimal cell adhesion. For low ionic strength buffer, optimum results were obtained for a zwitterionic coating of pure egg phosphatidylcholine; for a rich growth medium, the best results were obtained for zwitterionic bilayers or those with slight negative or moderate positive charge from the incorporation of 5-10 mol% egg phosphatidylglycerol or 30 mol% ethylphosphocholine. In both solutions, the presence of 10 g L-1 glucose in the cell suspension reduced cell adhesion. Under optimum conditions, all cells were consistently removed from the channels, demonstrating the utility of these coatings for whole-cell microfluidic assays. These results provide practical information for immediate application and suggest future research areas on cell-lipid interactions.
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Affiliation(s)
- Julia R Clapis
- Department of Chemistry, Trinity College, 300 Summit St., Hartford, CT 06106, USA.
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4
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Zhukovsky MA, Filograna A, Luini A, Corda D, Valente C. Phosphatidic acid in membrane rearrangements. FEBS Lett 2019; 593:2428-2451. [PMID: 31365767 DOI: 10.1002/1873-3468.13563] [Citation(s) in RCA: 99] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Revised: 07/25/2019] [Accepted: 07/26/2019] [Indexed: 12/16/2022]
Abstract
Phosphatidic acid (PA) is the simplest cellular glycerophospholipid characterized by unique biophysical properties: a small headgroup; negative charge; and a phosphomonoester group. Upon interaction with lysine or arginine, PA charge increases from -1 to -2 and this change stabilizes protein-lipid interactions. The biochemical properties of PA also allow interactions with lipids in several subcellular compartments. Based on this feature, PA is involved in the regulation and amplification of many cellular signalling pathways and functions, as well as in membrane rearrangements. Thereby, PA can influence membrane fusion and fission through four main mechanisms: it is a substrate for enzymes producing lipids (lysophosphatidic acid and diacylglycerol) that are involved in fission or fusion; it contributes to membrane rearrangements by generating negative membrane curvature; it interacts with proteins required for membrane fusion and fission; and it activates enzymes whose products are involved in membrane rearrangements. Here, we discuss the biophysical properties of PA in the context of the above four roles of PA in membrane fusion and fission.
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Affiliation(s)
- Mikhail A Zhukovsky
- Institute of Protein Biochemistry and Institute of Biochemistry and Cell Biology, National Research Council, Naples, Italy
| | - Angela Filograna
- Institute of Protein Biochemistry and Institute of Biochemistry and Cell Biology, National Research Council, Naples, Italy
| | - Alberto Luini
- Institute of Protein Biochemistry and Institute of Biochemistry and Cell Biology, National Research Council, Naples, Italy
| | - Daniela Corda
- Institute of Protein Biochemistry and Institute of Biochemistry and Cell Biology, National Research Council, Naples, Italy
| | - Carmen Valente
- Institute of Protein Biochemistry and Institute of Biochemistry and Cell Biology, National Research Council, Naples, Italy
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5
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Kulig W, Korolainen H, Zatorska M, Kwolek U, Wydro P, Kepczynski M, Róg T. Complex Behavior of Phosphatidylcholine-Phosphatidic Acid Bilayers and Monolayers: Effect of Acyl Chain Unsaturation. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:5944-5956. [PMID: 30942590 DOI: 10.1021/acs.langmuir.9b00381] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Phosphatidic acids (PAs) have many biological functions in biomembranes, e.g., they are involved in the proliferation, differentiation, and transformation of cells. Despite decades of research, the molecular understanding of how PAs affect the properties of biomembranes remains elusive. In this study, we explored the properties of lipid bilayers and monolayers composed of PAs and phosphatidylcholines (PCs) with various acyl chains. For this purpose, the Langmuir monolayer technique and atomistic molecular dynamics (MD) simulations were used to study the miscibility of PA and PC lipids and the molecular organization of mixed bilayers. The monolayer experiments demonstrated that the miscibility of membrane components strongly depends on the structure of the hydrocarbon chains and thus on the overall lipid shape. Interactions between PA and PC molecules vary from repulsive, for systems containing lipids with saturated and unsaturated acyl tails (strongly positive values of the excess free energy of mixing), to attractive, for systems in which all lipid tails are saturated (negative values of the excess free energy of mixing). The MD simulations provided atomistic insight into polar interactions (formation of hydrogen bonds and charge pairs) in PC-PA systems. H-bonding between PA monoanions and PCs in mixed bilayers is infrequent, and the lipid molecules interact mainly via electrostatic interactions. However, the number of charge pairs significantly decreases with the number of unsaturated lipid chains in the PA-PC system. The PA dianions weakly interact with the zwitterionic lipids, but their headgroups are more hydrated as compared to the monoanionic form. The acyl chains in all PC-PA bilayers are more ordered compared to single-component PC systems. In addition, depending on the combination of lipids, we observed a deeper location of the PA phosphate groups compared to the PC phosphate groups, which can alter the presentation of PAs for the peripheral membrane proteins, affecting their accessibility for binding.
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Affiliation(s)
- Waldemar Kulig
- Computational Physics Laboratory , Tampere University , P.O. Box 692, FI-33014 Tampere , Finland
- Department of Physics , University of Helsinki , P.O. Box 64, FI-00014 Helsinki , Finland
| | - Hanna Korolainen
- Department of Physics , University of Helsinki , P.O. Box 64, FI-00014 Helsinki , Finland
| | - Maria Zatorska
- Faculty of Chemistry , Jagiellonian University , Gronostajowa 2 , 30-387 Kraków , Poland
| | - Urszula Kwolek
- Faculty of Chemistry , Jagiellonian University , Gronostajowa 2 , 30-387 Kraków , Poland
| | - Paweł Wydro
- Faculty of Chemistry , Jagiellonian University , Gronostajowa 2 , 30-387 Kraków , Poland
| | - Mariusz Kepczynski
- Faculty of Chemistry , Jagiellonian University , Gronostajowa 2 , 30-387 Kraków , Poland
| | - Tomasz Róg
- Computational Physics Laboratory , Tampere University , P.O. Box 692, FI-33014 Tampere , Finland
- Department of Physics , University of Helsinki , P.O. Box 64, FI-00014 Helsinki , Finland
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6
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Hu X, Kang F, Yang B, Zhang W, Qin C, Gao Y. Extracellular Polymeric Substances Acting as a Permeable Barrier Hinder the Lateral Transfer of Antibiotic Resistance Genes. Front Microbiol 2019; 10:736. [PMID: 31057498 PMCID: PMC6479211 DOI: 10.3389/fmicb.2019.00736] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Accepted: 03/25/2019] [Indexed: 12/15/2022] Open
Abstract
Antibiotic resistance genes (ARGs) in bacteria are emerging contaminants as their proliferation in the environment poses significant threats to human health. It is well recognized that extracellular polymeric substances (EPS) can protect microorganisms against stress or damage from exogenous contaminants. However, it is not clear whether EPS could affect the lateral transfer of ARGs into bacteria, which is one of the major processes for the dissemination of ARGs. This study investigated the lateral transfer of ARGs carried by plasmids (pUC19, pHSG298, and pHSG396) into competent Escherichia coli cells with and without EPS. Transformant numbers and transformation efficiency for E. coli without EPS were up to 29 times of those with EPS at pH 7.0 in an aqueous system. The EPS removal further increased cell permeability in addition to the enhanced cell permeability by Ca2+, which could be responsible for the enhanced lateral transfer of ARGs. The fluorescence quenching experiments showed that EPS could strongly bind to plasmid DNA in the presence of Ca2+ and the binding strength (LogKA = 10.65–15.80 L mol-1) between EPS and plasmids was positively correlated with the enhancement percentage of transformation efficiency resulting from the EPS removal. X-ray photoelectron spectroscopy (XPS) analyses and model computation further showed that Ca2+ could electrostatically bind with EPS mainly through the carboxyl group, hydroxyl group, and RC-O-CR in glucoside, thus bridging the plasmid and EPS. As a result, the binding of plasmids with EPS hindered the lateral transfer of plasmid-borne ARGs. This study improved our understanding on the function of EPS in controlling the fate and transport of ARGs on the molecular and cellular scales.
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Affiliation(s)
- Xiaojie Hu
- Institute of Organic Contaminant Control and Soil Remediation, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, China
| | - Fuxing Kang
- Institute of Organic Contaminant Control and Soil Remediation, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, China
| | - Bing Yang
- Institute of Organic Contaminant Control and Soil Remediation, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, China
| | - Wei Zhang
- Environmental Science and Policy Program, Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, MI, United States
| | - Chao Qin
- Institute of Organic Contaminant Control and Soil Remediation, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, China
| | - Yanzheng Gao
- Institute of Organic Contaminant Control and Soil Remediation, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, China
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7
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Zhong Y, Wang G. Three-Dimensional Heterogeneous Structure Formation on a Supported Lipid Bilayer Disclosed by Single-Particle Tracking. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:11857-11865. [PMID: 30170491 DOI: 10.1021/acs.langmuir.8b01690] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Three-dimensional (3D) single-particle tracking was employed to study the lipid membrane morphology change at different pHs on glass supported lipid bilayers (SLBs) [1,2-dioleoyl- sn-glycero-3-phosphoethanolamine/1,2-dioleoyl- sn-glycero-3-phospho-l-serine (sodium salt)/1,2-dioleoyl- sn-glycero-3-phosphocholine = 5:3:2]. Fluorescently tagged, carboxylated polystyrene nanoparticles (of 100 nm) were used as the probes. At neutral pHs, the particles' diffusion was close to two-dimensional Brownian motion, indicating a mainly planar structure of the SLBs. When the environmental pH was tuned to be basic at 10.0, transiently confined diffusions within small areas were frequently observed. These confinements had a lateral dimension of 100-200 nm. Most interestingly, they showed 3D bulged structures protruding from the planar lipid bilayer. The particles were trapped by these 3D structures for a short period of time (∼0.75 s), with an estimated escape activation energy of ∼4.2 kB T. Nonuniform distribution of pH-sensitive lipids in the membrane was proposed to explain the formation of these 3D heterogeneous structures. This work suggests that the geometry of the 3D lipid structures can play a role in tuning the particle-lipid surface interactions. It sheds new light on the origin of lateral heterogeneity on the lipid membrane.
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Affiliation(s)
- Yaning Zhong
- Department of Chemistry , North Carolina State University , Raleigh , North Carolina 27695-8204 , United States
| | - Gufeng Wang
- Department of Chemistry , North Carolina State University , Raleigh , North Carolina 27695-8204 , United States
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8
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Peruzzi J, Gutierrez MG, Mansfield K, Malmstadt N. Dynamics of Hydrogel-Assisted Giant Unilamellar Vesicle Formation from Unsaturated Lipid Systems. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:12702-12709. [PMID: 27934517 DOI: 10.1021/acs.langmuir.6b01889] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
While current research is centered on observing biophysical properties and phenomena in giant unilamellar vesicles (GUVs), little is known about fabrication parameters that control GUV formation. Using different lipids and rehydration buffers, we directly observe varying dynamics of hydrogel-assisted GUV formation via fluorescence microscopy. We observe the effects of buffer ionic strength, osmolarity, agarose density, and pH on the formation of GUVs using neutral and charged lipids. We find that increasing rehydration buffer ionic strength correlates with increased vesicle size and rate of GUV formation. Increasing buffer acidity increased the rate of GUV formation, while more basic environments slowed the rate. For buffers containing 500 mM sucrose, GUV formation was overall inhibited and only tubules formed. Observations of GUV formation dynamics elucidate parametric effects of charge, ionic strength, pH, and osmolarity, demonstrating the versatility of this biomimetic platform.
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Affiliation(s)
- Justin Peruzzi
- Mork Family Department of Chemical Engineering and Materials Science, University of Southern California , 925 Bloom Walk, Los Angeles, California 90089, United States
| | - M Gertrude Gutierrez
- Mork Family Department of Chemical Engineering and Materials Science, University of Southern California , 925 Bloom Walk, Los Angeles, California 90089, United States
| | - Kylee Mansfield
- Mork Family Department of Chemical Engineering and Materials Science, University of Southern California , 925 Bloom Walk, Los Angeles, California 90089, United States
| | - Noah Malmstadt
- Mork Family Department of Chemical Engineering and Materials Science, University of Southern California , 925 Bloom Walk, Los Angeles, California 90089, United States
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9
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Kwolek U, Kulig W, Wydro P, Nowakowska M, Róg T, Kepczynski M. Effect of Phosphatidic Acid on Biomembrane: Experimental and Molecular Dynamics Simulations Study. J Phys Chem B 2015; 119:10042-51. [DOI: 10.1021/acs.jpcb.5b03604] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Urszula Kwolek
- Faculty
of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Kraków, Poland
| | - Waldemar Kulig
- Department
of Physics, Tampere University of Technology, P.O. Box 692, FI-33101 Tampere, Finland
| | - Paweł Wydro
- Faculty
of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Kraków, Poland
| | - Maria Nowakowska
- Faculty
of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Kraków, Poland
| | - Tomasz Róg
- Department
of Physics, Tampere University of Technology, P.O. Box 692, FI-33101 Tampere, Finland
| | - Mariusz Kepczynski
- Faculty
of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Kraków, Poland
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10
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Bohdanowicz M, Grinstein S. Role of Phospholipids in Endocytosis, Phagocytosis, and Macropinocytosis. Physiol Rev 2013; 93:69-106. [DOI: 10.1152/physrev.00002.2012] [Citation(s) in RCA: 198] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Endocytosis, phagocytosis, and macropinocytosis are fundamental processes that enable cells to sample their environment, eliminate pathogens and apoptotic bodies, and regulate the expression of surface components. While a great deal of effort has been devoted over many years to understanding the proteins involved in these processes, the important contribution of phospholipids has only recently been appreciated. This review is an attempt to collate and analyze the rapidly emerging evidence documenting the role of phospholipids in clathrin-mediated endocytosis, phagocytosis, and macropinocytosis. A primer on phospholipid biosynthesis, catabolism, subcellular distribution, and transport is presented initially, for reference, together with general considerations of the effects of phospholipids on membrane curvature and charge. This is followed by a detailed analysis of the critical functions of phospholipids in the internalization processes and in the maturation of the resulting vesicles and vacuoles as they progress along the endo-lysosomal pathway.
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Affiliation(s)
- Michal Bohdanowicz
- Division of Cell Biology, Hospital for Sick Children, and Institute of Medical Sciences, University of Toronto, Toronto, Canada
| | - Sergio Grinstein
- Division of Cell Biology, Hospital for Sick Children, and Institute of Medical Sciences, University of Toronto, Toronto, Canada
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11
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Coordination forces between lipid bilayers produced by ferricyanide and Ca2+. Colloids Surf B Biointerfaces 2012; 91:26-33. [DOI: 10.1016/j.colsurfb.2011.10.046] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2011] [Accepted: 10/17/2011] [Indexed: 11/18/2022]
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12
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Goertz MP, Goyal N, Montano GA, Bunker BC. Lipid bilayer reorganization under extreme pH conditions. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:5481-5491. [PMID: 21462990 DOI: 10.1021/la2001305] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Supported lipid bilayers containing phosphatidylcholine headgroups are observed to undergo reorganization from a 2D fluid, lipid bilayer assembly into an array of complex 3D structures upon exposure to extreme pH environments. These conditions induce a combination of molecular packing and electrostatic interactions that can create dynamic morphologies of highly curved lipid membrane structures. This work demonstrates that fluid, single-component lipid bilayer assemblies can create complex morphologies, a phenomenon typically only associated with lipid bilayers of mixed composition.
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Affiliation(s)
- Matthew P Goertz
- Center for Integrated Nanotechnologies, Sandia National Laboratories, Albuquerque, New Mexico 87185, United States.
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13
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Pucadyil TJ, Schmid SL. Supported bilayers with excess membrane reservoir: a template for reconstituting membrane budding and fission. Biophys J 2010; 99:517-25. [PMID: 20643070 DOI: 10.1016/j.bpj.2010.04.036] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2010] [Revised: 04/08/2010] [Accepted: 04/19/2010] [Indexed: 10/19/2022] Open
Abstract
A complete mechanistic understanding of membrane-localized processes in vesicular transport, such as membrane budding and fission, requires their reconstitution with biochemically-defined components from a biochemically-defined substrate. Supported bilayers formed by vesicle fusion represent an attractive substrate for this purpose. However, conventional supported bilayers lack a sufficient membrane reservoir to recreate membrane budding and fission events. We describe the formation of supported bilayers with excess membrane reservoir (SUPER) templates from the fusion of liposomes containing negatively charged lipids on silica beads under high-ionic-strength conditions. Using a fluorescence microscopy-based assay to monitor early and late stages of supported bilayer formation, we show that an increase in ionic strength leads to an increase in the rates of liposome adsorption and subsequent fusion during formation of supported bilayers. The two rates, however, increase disproportionally, leading to accumulation of excess reservoir with an increase in ionic strength. SUPER templates allow the seamless application of microscopy-based assays to analyze membrane-localized processes together with sedimentation-based assays to isolate vesicular and nonvesicular products released from the membrane. The results presented here emphasize the general utility of these templates for analyzing vesicular and nonvesicular transport processes.
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Affiliation(s)
- Thomas J Pucadyil
- Department of Cell Biology, Scripps Research Institute, La Jolla, California, USA.
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14
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Vogtt K, Jeworrek C, Garamus VM, Winter R. Microdomains in lipid vesicles: structure and distribution assessed by small-angle neutron scattering. J Phys Chem B 2010; 114:5643-8. [PMID: 20369805 DOI: 10.1021/jp101167n] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
We examined the structure and distribution of microdomains in ternary multilamellar and unilamellar vesicles representing a canonical model raft mixture consisting of dioleoylphosphatidylcholine (DOPC), dipalmitoylphosphatidylcholine (DPPC), and cholesterol via contrast matched small-angle neutron scattering (SANS). The impetus of the work was to reveal the size and distribution of microdomains consistent with the form factor and intermolecular structure factor S(Q) of the scattering pattern of unilamellar and multilamellar vesicles prepared from this ternary lipid system. The data are consistent with the presence of cylindrically shaped microdomains with an average radius of approximately 15 nm assembled in a fractal-like geometry, and with corresponding modeling studies. In the multilamellar vesicle system, coupling of domains across the interlamellar water layer is observed.
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Affiliation(s)
- Karsten Vogtt
- Helmholtz-Zentrum Berlin, Hahn-Meitner-Platz 100, D-14109 Berlin, Germany
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15
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Haberl S, Miklavcic D, Pavlin M. Effect of Mg ions on efficiency of gene electrotransfer and on cell electropermeabilization. Bioelectrochemistry 2010; 79:265-71. [PMID: 20580903 DOI: 10.1016/j.bioelechem.2010.04.001] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2009] [Revised: 04/13/2010] [Accepted: 04/14/2010] [Indexed: 11/24/2022]
Abstract
Gene electrotransfer is a promising nonviral method that enables DNA to be transferred into living cells with electric pulses. However, there are many parameters that determine gene electrotransfer efficiency. One of the steps involved in gene electrotransfer is interaction of DNA with the cell membrane. Divalent cations in the electroporative media can influence the anchoring of DNA to the cell membrane and by that gene electrotransfer efficiency. Here we report the effect of different concentrations of Mg2+ on electropermeabilization for small molecule (propidium iodide), gene electrotransfer and viability of the cells. We also used TOTO-1 dye to visualize DNA-cell membrane interaction for different [Mg]. For this purpose, we used different electroporative media with increasing [Mg]. Our study shows that higher [Mg] lead to higher electropermeabilization for propidium iodide and higher viability, while causing lower gene electrotransfer efficiency. Because we observed higher TOTO-1 labeled DNA at cell surface when using higher [Mg], we suggest that Mg2+ ions can bind DNA at cell surface at such strength that cannot pass into the cell during application of electric pulses, which can lead to lower gene transfection. There may also be other mechanisms involved, since there are many steps of gene electrotransfer on which Mg2+ ions can have an effect on. Our results also imply that membrane permeability changes are not sufficient for an efficient gene electrotransfer.
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Affiliation(s)
- Sasa Haberl
- University of Ljubljana, Faculty of Electrical Engineering, Trzaska 25, SI-1000 Ljubljana, Slovenia
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16
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Haque F, Pandey AP, Cambrea LR, Rochet JC, Hovis JS. Adsorption of alpha-synuclein on lipid bilayers: modulating the structure and stability of protein assemblies. J Phys Chem B 2010; 114:4070-81. [PMID: 20187615 PMCID: PMC2855901 DOI: 10.1021/jp1006704] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The interaction of alpha-synuclein with phospholipid membranes has been examined using supported lipid bilayers and epi-fluorescence microscopy. The membranes contained phosphatidylcholine (PC) and phosphatidic acid (PA), which mix at physiological pH. Upon protein adsorption, the lipids undergo fluid-fluid phase separation into PC-rich and PA-rich regions. The protein preferentially adsorbs to the PA-rich regions. The adsorption and subsequent aggregation of alpha-synuclein was probed by tuning several parameters: the charge on the lipids, the charge on the protein, and the screening environment. Conditions which promoted the greatest extent of adsorption resulted in structurally heterogeneous aggregates, while comparatively homogeneous aggregates were observed under conditions whereby adsorption did not occur as readily. Our observation that different alterations to the system lead to different degrees of aggregation and different aggregate structures poses a challenge for drug discovery. Namely, therapies aimed at neutralizing alpha-synuclein must target a broad range of potentially toxic, membrane-bound assemblies.
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Affiliation(s)
- Farzin Haque
- Department of Chemistry, Purdue University, West Lafayette, IN 47907
| | - Anjan P. Pandey
- Department of Chemistry, Purdue University, West Lafayette, IN 47907
| | - Lee R. Cambrea
- Department of Chemistry, Purdue University, West Lafayette, IN 47907
| | - Jean-Christophe Rochet
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN 47907
| | - Jennifer S. Hovis
- Department of Chemistry, Purdue University, West Lafayette, IN 47907
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17
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Majd S, Yusko EC, MacBriar AD, Yang J, Mayer M. Gramicidin pores report the activity of membrane-active enzymes. J Am Chem Soc 2010; 131:16119-26. [PMID: 19886696 DOI: 10.1021/ja904072s] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Phospholipases constitute a ubiquitous class of membrane-active enzymes that play a key role in cellular signaling, proliferation, and membrane trafficking. Aberrant phospholipase activity is implicated in a range of diseases including cancer, inflammation, and myocardial disease. Characterization of these enzymes is therefore important, both for improving the understanding of phospholipase catalysis and for accelerating pharmaceutical and biotechnological applications. This paper describes a novel approach to monitor, in situ and in real-time, the activity of phospholipase D (PLD) and phospholipase C (PLC) on planar lipid bilayers. This method is based on lipase-induced changes in the electrical charge of lipid bilayers and on the concomitant change in ion concentration near lipid membranes. The approach reports these changes in local ion concentration by a measurable change in the single channel ion conductance through pores of the ion channel-forming peptide gramicidin A. This enzyme assay takes advantage of the amplification characteristics of gramicidin pores to sense the activity of picomolar to nanomolar concentrations of membrane-active enzymes without requiring labeled substrates or products. The resulting method proceeds on lipid bilayers without the need for detergents, quantifies enzyme activity on native lipid substrates within minutes, and provides unique access to both leaflets of well-defined lipid bilayers; this method also makes it possible to generate planar lipid bilayers with transverse lipid asymmetry.
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Affiliation(s)
- Sheereen Majd
- Department of Chemical Engineering, University of Michigan, 1101 Beal Avenue, Ann Arbor, Michigan 48109-2110, USA
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Greiner AJ, Pillman HA, Worden RM, Blanchard GJ, Ofoli RY. Effect of hydrogen bonding on the rotational and translational dynamics of a headgroup-bound chromophore in bilayer lipid membranes. J Phys Chem B 2009; 113:13263-8. [PMID: 19761197 DOI: 10.1021/jp9057862] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We have studied the interactions of the chromophore 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-7-nitro-2-1,3-benzoxadiazol-4-yl (18:1 NBD-PE) imbedded in the headgroup region of bilayer lipid membranes consisting of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and 1,2-dioleoyl-sn-glycero-3-[phospho-rac-(1-glycerol)] (DOPG). We have examined the molecular and mesoscale dynamics of the chromophore using time-correlated single photon counting (TCSPC) to measure rotational diffusion dynamics in lipid vesicles and fluorescence recovery after pattern photobleaching (FRAPP) to determine translational diffusion coefficients and mobile fractions in supported lipid bilayers. TCSPC data reveal that chromophore rotational diffusion rates in DOPG vesicles are statistically the same as in DOPC and mixed DOPC/DOPG vesicles, suggesting that the NBD-PE chromophore does not interact strongly with the headgroup region of these bilayers; however, FRAPP experiments show that lateral diffusion is statistically lower in mixed DOPC/DOPG-supported bilayers than in DOPC-supported bilayers. These results suggest that bilayers containing DOPG likely undergo interlipid headgroup hydrogen bonding interactions that suppress translational diffusion.
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Affiliation(s)
- Aaron J Greiner
- Department of Chemical Engineering and Materials Science and Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, USA
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Filippov A, Orädd G, Lindblom G. Effect of NaCl and CaCl2 on the lateral diffusion of zwitterionic and anionic lipids in bilayers. Chem Phys Lipids 2009; 159:81-7. [DOI: 10.1016/j.chemphyslip.2009.03.007] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2008] [Revised: 02/05/2009] [Accepted: 03/26/2009] [Indexed: 11/28/2022]
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Lamberson ER, Cambrea LR, Rochet JC, Hovis JS. Path dependence of three-phase or two-phase end points in fluid binary lipid mixtures. J Phys Chem B 2009; 113:3431-6. [PMID: 19243147 DOI: 10.1021/jp810326w] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The phase behavior of anionic/zwitterionic mixtures can be controlled by tuning the charge state of the anionic lipid. In the case of dioleoylphosphatidic acid (DOPA)/dioleoylphosphatidylcholine (DOPC) mixtures, demixing occurs either when DOPA is protonated or when DOPA(2-):Ca(2+) complexes form. Herein it will be shown that the final end point, a three-phase or two-phase system, depends on the order in which the charge state is manipulated. The facile accessibility of different end points is a clear demonstration of the inherent flexibility of biological systems.
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Affiliation(s)
- Emily R Lamberson
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, USA
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Charging and structure of zwitterionic supported bilayer lipid membranes studied by streaming current measurements, fluorescence microscopy, and attenuated total reflection Fourier transform infrared spectroscopy. Biointerphases 2009; 4:1-6. [DOI: 10.1116/1.3082042] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Giger K, Lamberson ER, Hovis JS. Formation of complex three-dimensional structures in supported lipid bilayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:71-74. [PMID: 19067589 DOI: 10.1021/la8033269] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Cell membranes are continually undergoing a wide range of shape transformations. Here, we demonstrate the formation of several structures in supported bilayers, including tubules, caps, and giant multivesicular structures. The key elements required for these transformations are osmotic pressure imbalances, insertion of lipids with positive curvature, and lipids whose curvature is dependent on the screening environment. With these elements, a wide variety of transformations can be achieved in the absence of protein.
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Affiliation(s)
- Katie Giger
- Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907, USA
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Renner L, Osaki T, Chiantia S, Schwille P, Pompe T, Werner C. Supported lipid bilayers on spacious and pH-responsive polymer cushions with varied hydrophilicity. J Phys Chem B 2008; 112:6373-8. [PMID: 18426235 DOI: 10.1021/jp711479f] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We report the successful formation of supported multicomponent lipid bilayer membranes (sLBMs) on polymer cushions consisting of a set of alternating maleic acid copolymers. The formation of sLBMs was triggered by a transient reduction of the electrostatic repulsion between the polymer cushions and the lipid vesicles by lowering the solution's pH to 4. Upon formation, the stability of the sLBMs was not affected by subsequent variations of the environmental pH. The degree of hydrophilicity and swelling of the anionic polymer cushions was found to determine both the kinetics of the membrane formation and the mobility of the lipid bilayer with lipid diffusion coefficients in the range from 0.26 to 2.6 microm2s(-1). The introduced polymer cushion system is concluded to provide a versatile base for the integration of active transmembrane proteins in sLBMs.
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Affiliation(s)
- Lars Renner
- Leibniz Institute of Polymer Research Dresden, Max Bergmann Center of Biomaterials Dresden, Hohe Str. 56, 01069 Dresden, Germany
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Lamberson ER, Cambrea LR, Hovis JS. Controlling the charge and organization of anionic lipid bilayers: effect of monovalent and divalent ions. J Phys Chem B 2007; 111:13664-7. [PMID: 18001085 DOI: 10.1021/jp076306a] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
It is shown that the organization of lipid bilayers containing phosphatidic acid (PA) and phosphatidlycholine (PC) can be controlled by altering the monovalent and divalent ion concentrations. At high pH and/or calcium concentration, 1:1 Ca(2+)-PA(2-) complexes form; these complexes demix, and PA-rich and PC-rich regions are observable with epifluorescence microscopy. The results are compared with predictions from electrostatic theory. It is noted that the complex formation correlates in a roughly linear fashion with the monovalent/divalent ion ratio, a parameter that cells adjust.
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Affiliation(s)
- Emily R Lamberson
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, USA
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