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Batchu KC, Hänninen S, Jha SK, Jeltsch M, Somerharju P. Factors regulating the substrate specificity of cytosolic phospholipase A 2 -alpha in vitro. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1861:1597-1604. [DOI: 10.1016/j.bbalip.2016.06.022] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2016] [Revised: 06/28/2016] [Accepted: 06/30/2016] [Indexed: 10/21/2022]
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2
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Sarmento MJ, Pinto SN, Coutinho A, Prieto M, Fernandes F. Accurate quantification of inter-domain partition coefficients in GUVs exhibiting lipid phase coexistence. RSC Adv 2016. [DOI: 10.1039/c6ra13170k] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Giant unilamellar vesicles (GUVs) with phase coexistence allow for the recovery of inter-domain partition coefficients (Kp) of fluorescent molecules through comparison of fluorescence intensities in each phase.
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Affiliation(s)
- M. J. Sarmento
- Centro de Química-Física Molecular and Institute of Nanoscience and Nanotechnology
- Instituto Superior Técnico
- University of Lisbon
- Lisbon
- Portugal
| | - S. N. Pinto
- Centro de Química-Física Molecular and Institute of Nanoscience and Nanotechnology
- Instituto Superior Técnico
- University of Lisbon
- Lisbon
- Portugal
| | - A. Coutinho
- Centro de Química-Física Molecular and Institute of Nanoscience and Nanotechnology
- Instituto Superior Técnico
- University of Lisbon
- Lisbon
- Portugal
| | - M. Prieto
- Centro de Química-Física Molecular and Institute of Nanoscience and Nanotechnology
- Instituto Superior Técnico
- University of Lisbon
- Lisbon
- Portugal
| | - F. Fernandes
- Centro de Química-Física Molecular and Institute of Nanoscience and Nanotechnology
- Instituto Superior Técnico
- University of Lisbon
- Lisbon
- Portugal
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3
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Synthesis and validation of novel cholesterol-based fluorescent lipids designed to observe the cellular trafficking of cationic liposomes. Bioorg Med Chem Lett 2015; 25:3893-6. [PMID: 26243368 DOI: 10.1016/j.bmcl.2015.07.051] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Revised: 07/02/2015] [Accepted: 07/18/2015] [Indexed: 11/23/2022]
Abstract
Cholesterol-based fluorescent lipids with ether linker were synthesized using NBD (Chol-E-NBD) or Rhodamine B (Chol-E-Rh), and the usefulnesses as fluorescent probes for tracing cholesterol-based liposomes were validated. The fluorescent intensities of liposomes containing these modified lipids were measured and observed under a microscope. Neither compound interfered with the expression of GFP plasmid, and live cell images were obtained without interferences. Changes in the fluorescent intensity of liposomes containing Chol-E-NBD were followed by flow cytometry for up to 24h. These fluorescent lipids could be useful probes for trafficking of cationic liposome-mediated gene delivery.
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4
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Batchu KC, Hokynar K, Jeltsch M, Mattonet K, Somerharju P. Substrate efflux propensity is the key determinant of Ca2+-independent phospholipase A-β (iPLAβ)-mediated glycerophospholipid hydrolysis. J Biol Chem 2015; 290:10093-103. [PMID: 25713085 DOI: 10.1074/jbc.m115.642835] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2015] [Indexed: 12/13/2022] Open
Abstract
The A-type phospholipases (PLAs) are key players in glycerophospholipid (GPL) homeostasis and in mammalian cells; Ca(2+)-independent PLA-β (iPLAβ) in particular has been implicated in this essential process. However, the regulation of this enzyme, which is necessary to avoid futile competition between synthesis and degradation, is not understood. Recently, we provided evidence that the efflux of the substrate molecules from the bilayer is the rate-limiting step in the hydrolysis of GPLs by some secretory (nonhomeostatic) PLAs. To study whether this is the case with iPLAβ as well, a mass spectrometric assay was employed to determine the rate of hydrolysis of multiple saturated and unsaturated GPL species in parallel using micelles or vesicle bilayers as the macrosubstrate. With micelles, the hydrolysis decreased with increasing acyl chain length independent of unsaturation, and modest discrimination between acyl positional isomers was observed, presumably due to the differences in the structure of the sn-1 and sn-2 acyl-binding sites of the protein. In striking contrast, no significant discrimination between positional isomers was observed with bilayers, and the rate of hydrolysis decreased with the acyl chain length logarithmically and far more than with micelles. These data provide compelling evidence that efflux of the substrate molecule from the bilayer, which also decreases monotonously with acyl chain length, is the rate-determining step in iPLAβ-mediated hydrolysis of GPLs in membranes. This finding is intriguing as it may help to understand how homeostatic PLAs are regulated and how degradation and biosynthesis are coordinated.
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Affiliation(s)
| | - Kati Hokynar
- From the Departments of Biochemistry and Developmental Biology and
| | - Michael Jeltsch
- Biomedicine, Faculty of Medicine, University of Helsinki, Helsinki 00014, Finland
| | - Kenny Mattonet
- Biomedicine, Faculty of Medicine, University of Helsinki, Helsinki 00014, Finland
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5
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Wang X, Quinn PJ. Preferential interaction of alpha-tocopherol with phosphatidylcholines in mixed aqueous dispersions of phosphatidylcholine and phosphatidylethanolamine. EUROPEAN JOURNAL OF BIOCHEMISTRY 2000; 267:6362-8. [PMID: 11029578 DOI: 10.1046/j.1432-1327.2000.01720.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The effect of alpha-tocopherol on the structure and phase behaviour of mixed aqueous dispersions of phosphatidylcholine and phosphatidylethanolamine has been examined by synchrotron X-ray diffraction and freeze-fracture electron microscopy. Equimolar mixtures of fully saturated derivatives of phospholipids that show gel phase immiscibility were examined including dimyristoylglycerophosphocholine/dipalmitoylglycerophosphoethanolamin e and distearoylglycerophosphocholine/dilauroylglycerophosphoethanolamine++ +. Analysis of the X-ray scattering intensities recorded at wide angles during heating scans of mixed aqueous dispersions containing 2.5 or 5 mol% alpha-tocopherol showed that alpha-tocopherol disordered the acyl chain packing of the phosphatidylcholine to a greater extent than the phosphatidylethanolamine component of the mixture. This suggested that alpha-tocopherol preferentially interacts with phosphatidylcholine rather than phosphatidylethanolamine, irrespective of whether this was the high or low melting point component of the mixture. The presence of 20 mol% alpha-tocopherol in either phospholipid mixture prevented gel phase separation during the prior cooling scan and no conclusions could be drawn as to the distribution of alpha-tocopherol in these mixtures.
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Affiliation(s)
- X Wang
- Division of Life Sciences, King's College London, UK
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6
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Wang TY, Silvius JR. Different sphingolipids show differential partitioning into sphingolipid/cholesterol-rich domains in lipid bilayers. Biophys J 2000; 79:1478-89. [PMID: 10969009 PMCID: PMC1301041 DOI: 10.1016/s0006-3495(00)76399-5] [Citation(s) in RCA: 117] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Two fluorescence-based approaches have been applied to examine the differential partitioning of fluorescent phospho- and sphingolipid molecules into sphingolipid-enriched domains modeling membrane "lipid rafts." Fluorescence-quenching measurements reveal that N-(diphenylhexatrienyl)propionyl- (DPH3:0-)-labeled gluco- and galactocerebroside partition into sphingolipid-enriched domains in sphingolipid/phosphatidylcholine/cholesterol bilayers with substantially higher affinity than do analogous sphingomyelin, ceramide, or phosphatidylcholine molecules. By contrast, the affinity of sphingomyelin and ceramide for such domains is only marginally greater than that of a phosphatidylcholine with similar hydrocarbon chains. By using direct measurements of molecular partitioning between vesicles of different compositions, we show that the relative affinities of different C(6)-NBD- and C(5)-Bodipy-labeled sphingolipids for sphingolipid-enriched domains are quantitatively, and in most circumstances even qualitatively, quite different from those found for species whose N-acyl chains more closely resemble the long saturated chains of cellular sphingolipids. These findings lend support in principle to previous suggestions that differential partitioning of different sphingolipids into "raft" domains could contribute to the differential trafficking of these species in eukaryotic cells. However, our findings also indicate that short-chain sphingolipid probes previously used to examine this phenomenon are in general ill-suited for such applications.
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Affiliation(s)
- T Y Wang
- Department of Biochemistry, McGill University, Montréal, Québec H3G 1Y6, Canada
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7
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Wongkajornsilp A, Rosenberry TL. Uptake of exogenous sn-1-acyl-2-lyso-phosphatidylinositol into HeLa S3 cells. Reacylation on the cell surface and metabolism to glucosaminyl(acyl)phosphatidylinositol. J Biol Chem 1995; 270:9147-53. [PMID: 7721829 DOI: 10.1074/jbc.270.16.9147] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
A HeLa S3 subline is unusual in accumulating relatively large amounts of glucosaminyl(acyl)phosphatidylinositol (GlcN(acyl)PI), a derivative of phosphatidylinositol (PI) in which both GlcN and a fatty acid are linked to inositol hydroxyl groups (D. Sevlever, D. Humphrey, and T.L. Rosenberry, submitted for publication). This lipid is a proposed intermediate on the biosynthetic pathway for glycosyl-PI (GPI) anchors of membrane proteins. In this study we demonstrate for the first time that exogenous inositol phospholipids can enter this biosynthetic pathway and be metabolized to GlcN(acyl)PI. When HeLa S3 cells were incubated for 24 h with exogenous PI or sn-1-acyl-2-lyso-phosphatidyl-inositol (lyso-PI) labeled with 3H in the inositol group, 25-30% of the label was recovered in cell-associated lipids and most of the remaining 70-75% in hydrophilic metabolites in the medium. The predominant labeled lipid was PI, with smaller amounts of lyso-PI, phosphatidylinositol 4-phosphate (PIP), and GlcN(acyl)PI. Both exogenous lipid precursors gave the same distribution of labeled lipids, and a similar distribution was observed for endogenous inositol phospholipids metabolically labeled with [3H]inositol. Addition of excess inositol had no effect on the conversion of [3H]lyso-PI to [3H]GlcN(acyl)PI, indicating that the conversion did not result from breakdown to [3H]inositol followed by resynthesis. The cellular orientation of incorporated PI and lyso-PI was determined by incubating cells at 4 degrees C with PI-specific phospholipase C (PI-PLC). This enzyme cleaves only PI and lyso-PI on the outer leaflet of the cell membrane. After 24-h incubation with either precursor, only about 15% of cell-associated [3H]PI or [3H]lyso-PI was on the outer leaflet. However, more than 60% of the [3H]PI was on the outer leaflet after 1-h incubation with either precursor, suggesting that substantial sn-2 acylation of exogenous [3H]lyso-PI occurred in the outer leaflet. This suggestion was confirmed by examining labeled lipids in cells after uptake of [3H]lyso-PI at 4 degrees C. No transmembrane translocation of lyso-PI, PI phosphorylation, or PI glycosylation occurred at this temperature, but some sn-2 acylation was apparent and more than 90% of the [3H]PI formed was on the outer leaflet. These data indicate that sn-2 acylation can occur in the outer leaflet of the cell membrane, perhaps by transacylation from other cell surface phospholipids.
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Affiliation(s)
- A Wongkajornsilp
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA
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8
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Fluorescence techniques for probing water penetration into lipid bilayers. J Fluoresc 1995; 5:19-28. [DOI: 10.1007/bf00718779] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/1994] [Accepted: 09/27/1994] [Indexed: 10/26/2022]
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9
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Affiliation(s)
- E M Kosower
- Biophysical Organic Chemistry Unit, Tel-Aviv University, Raymond and Beverly Sackler Faculty of Exact Sciences, Ramat-Aviv, Israel
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10
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Ott S, Wunderli-Allenspach H. Liposomes and influenza viruses as an in vitro model for membrane interactions I. Kinetics of membrane fusion and lipid transfer. Eur J Pharm Sci 1994. [DOI: 10.1016/0928-0987(94)90041-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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11
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Affiliation(s)
- F Paltauf
- Institut für Biochemie und Lebensmittelchemie der Technischen Universität Graz, Austria
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12
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Leventis R, Silvius JR. Intermembrane lipid-mixing assays using acyl chain-labeled coumarinyl phospholipids. Methods Enzymol 1993; 220:32-42. [PMID: 8350761 DOI: 10.1016/0076-6879(93)20071-a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- R Leventis
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada
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13
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Brown RE. Spontaneous lipid transfer between organized lipid assemblies. BIOCHIMICA ET BIOPHYSICA ACTA 1992; 1113:375-89. [PMID: 1450207 PMCID: PMC4026044 DOI: 10.1016/0304-4157(92)90007-w] [Citation(s) in RCA: 80] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- R E Brown
- Hormel Institute, University of Minnesota, Austin 55912
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14
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van't Hof W, Silvius J, Wieland F, van Meer G. Epithelial sphingolipid sorting allows for extensive variation of the fatty acyl chain and the sphingosine backbone. Biochem J 1992; 283 ( Pt 3):913-7. [PMID: 1590779 PMCID: PMC1130974 DOI: 10.1042/bj2830913] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
In kidney MDCK and intestinal Caco-2 epithelial cells, glucosylceramide (GlcCer) and sphingomyelin (SPH) synthesized from the short-chain sphingolipid analogue N-6-[7-nitro-2,1,3-benzoxadiazol-4-yl]aminodecanoyl (C6-NBD)-ceramide are delivered to the cell surface with apical/basolateral polarities of 2-4 and 0.6-0.9 respectively. We have tested how variations in the lipid backbone affect these polarities. First, the C6-NBD moiety was replaced by a bare [14C]octanoyl chain or by the even more bulky fluorophores 8-bimanoylthio-octanoyl (C8-bimane) and 8-diethylaminocoumarin-octanoyl (C8-DECA). In addition, the sphingosine in C6-NBD-ceramide was changed in stereoconfiguration (L-threo) or saturation (dihydro). In all cases, GlcCer and SPH were produced and appeared on the cell surface at 37 degrees C, as assayed by back-exchange. The apical/basolateral polarity of the delivery of GlcCer was variable, but always exceeded 1. GlcCer was apically enriched over SPH (2-6 times for MDCK and 3-9 times for Caco-2). Even GlcCer synthesized from a highly water-soluble truncated ceramide (octanoyl-D-erythro-sphingosine analogue with C8 backbone) was enriched apically by a factor of greater than or equal to 2 both in absolute polarity and compared with SPH. Sphingolipid sorting was quantitatively but not qualitatively affected by dramatic changes in the lipid backbone.
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Affiliation(s)
- W van't Hof
- Department of Cell Biology, Medical School, University of Utrecht, The Netherlands
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15
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Shin TB, Leventis R, Silvius JR. Partitioning of fluorescent phospholipid probes between different bilayer environments. Estimation of the free energy of interlipid hydrogen bonding. Biochemistry 1991; 30:7491-7. [PMID: 1854750 DOI: 10.1021/bi00244a018] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Fluorescence spectroscopy has been used to monitor the partitioning of a series of exchangeable neutral phospholipid probes, labeled with carbazole, indolyl or diphenylhexatrienyl moieties, between large unilamellar vesicles containing 1-palmitoyl-2-oleoylphosphatidylcholine (POPC), 1,2-dioleoyloxy-3-(trimethylammonio) propane (DOTAP) or N-hexadecyl-N-(9-octadecenyl)-N,N-dimethylammonium chloride (HODMA). Phosphatidylethanolamine (PE) probes desorb from POPC-containing vesicles at markedly slower rates than do phosphatidylcholine (PC) probes with the same acyl chains. The rate of probe desorption from such vesicles is progressively enhanced by successive N-methylations of the amino group but not by methylation of C-2 of the ethanolamine moiety, a modification that leaves unaltered the hydrogen-bonding capacity of the polar headgroup. By contrast, the rates of desorption of different probes (with the same acyl chains) from HODMA or from DOTAP vesicles are much more comparable and reflect no clear systematic influence of the headgroup hydrogen-bonding capacity. Equilibrium-partitioning measurements indicate that the relative affinities of different probes for PC-rich vesicles, in competition with HODMA or DOTAP vesicles, increase with increasing hydrogen-bonding capacity of the probe headgroup in the order PC less than N,N-dimethyl PE less than N-methyl PE less than PE approximately phosphatidyl-2-amino-1-propanol. From such partitioning data, we estimate that interlipid hydrogen-bonding interactions (in competition with lipid-water interactions) contribute roughly -300 cal mol-1 to the free energy of a PE molecule in a hydrated liquid-crystalline phospholipid bilayer; this free-energy contribution is somewhat smaller, but still significant, for N-mono- and dimethylated PE's.
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Affiliation(s)
- T B Shin
- Department of Biochemistry, McGill University, Montréal, Québec, Canada
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16
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Beck A, Heissler D, Duportail G. 1-Palmitoyl-2-[3-(diphenylhexatrienyl) propanoyl]-sn-glycero-3-phosphoethanolamine as a fluorescent membrane probe. Synthesis and partitioning properties. Chem Phys Lipids 1990. [DOI: 10.1016/0009-3084(90)90144-g] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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17
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Brown PM, Silvius JR. Mechanisms of delivery of liposome-encapsulated cytosine arabinoside to CV-1 cells in vitro. Fluorescence-microscopic and cytotoxicity studies. BIOCHIMICA ET BIOPHYSICA ACTA 1990; 1023:341-51. [PMID: 2110480 DOI: 10.1016/0005-2736(90)90125-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Fluorescence microscopy and assays of the cytotoxicity of liposome-encapsulated cytosine arabinoside (araC) have been used to examine the interactions of CV-1 cells with pH-sensitive liposomes, combining phosphatidylethanolamine (PE) with oleic acid or with double-chain protonatable amphiphiles, and with pH-insensitive liposomes combining phosphatidylcholine (PC) and phosphatidylglycerol (PG). Fluorescence-microscopic observations indicate that double-chain protonatable amphiphiles remain tightly associated with pH-sensitive liposomes during incubations with CV-1 cell monolayers, and that cellular uptake of liposomes is strongly promoted by transferrin coupled to the liposome surface. Liposome-encapsulated araC showed much greater cytotoxicity toward CV-1 cells than did the free drug at equivalent concentrations under the same conditions. The cytotoxicity of encapsulated araC was strongly enhanced by liposome-conjugated transferrin and was maximal using pH-sensitive liposomes combining PE with the double-chain protonatable amphiphile N-(N'-oleoyl-2-aminopalmitoyl)serine. However, the drug was also markedly more cytotoxic when encapsulated in other types of transferrin-conjugated liposomes, including pH-insensitive PC/PG/cholesterol liposomes, than in the free form. The cytotoxicity of liposome-encapsulated araC is significantly attenuated by the nucleoside transport inhibitor nitrobenzothioinosine, and fluorescence microscopy using calcein-containing liposomes provides no evidence for efficient fusion between cellular membranes and any of the types of liposomes examined here. Based on these observations, we suggest that the major mechanism for cytoplasmic delivery of liposome-encapsulated araC is the carrier-mediated transport of drug that has been released from liposomes into the endosomal and/or the lysosomal compartments.
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Affiliation(s)
- P M Brown
- Department of Biochemistry, McGill University, Montréal, Canada
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18
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Wunderli-Allenspach H, Ott S. Kinetics of fusion and lipid transfer between virus receptor containing liposomes and influenza viruses as measured with the octadecylrhodamine B chloride assay. Biochemistry 1990; 29:1990-7. [PMID: 2328232 DOI: 10.1021/bi00460a005] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Octadecylrhodamine B chloride (R18) and ganglioside GD1a (virus receptor) were incorporated into small unilamellar liposomes [Hoekstra et al. (1984) Biochemistry 23, 5675-5681]. Upon interaction of these liposomes with PR8 influenza viruses without prebinding, two types of dequenching were observed at 37 degrees C, both second-order processes: a fast reaction at pH 5.3, 2k = 17.53 x 10(-3) (Q.s)-1, and a slow reaction at pH 7.4, 2k = 0.335 x 10(-3) (Q.s)-1. The maximal level of dequenching was the same for both. Upon prebinding of liposomes to PR8 viruses (30 min, 0 degrees C, pH 7.4) at high concentrations, a very fast dequenching occurred when the prebinding mixture was diluted into prewarmed (37 degrees C) 10 mM PBS, pH 5.3. For the initial phase, a first-order rate constant of 0.5 s-1 could be extrapolated. After a quick drop in velocity during the first 30 s, the reaction was kinetically indistinguishable from the one found without prebinding. A second-order process with 2k = 16.52 x 10(-3) (Q.s)-1 became rate-limiting. The fast reactions at pH 5.3 can be abolished by inactivation or removal of the virus hemagglutinin. We conclude that the reaction at pH 5.3 reflects the hemagglutinin-dependent fusion process known to occur between influenza viruses and partner membranes at low pH; however, second-order kinetics indicate that specific binding rather than fusion is the rate-limiting step. For the slow dequenching, which is not affected by prebinding, the rate constant is 20 times lower than for the fast reaction, and the process is independent of viral hemagglutinin.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- H Wunderli-Allenspach
- Department of Pharmacy, Biopharmacy, Federal Institute of Technology, Zürich, Switzerland
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19
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Affiliation(s)
- R E Brown
- Hormel Institute University of Minnesota, Austin 55912
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