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Robert C. Murphy – One of the best experts on this subject based on the ideXlab platform.

  • analysis of polyunsaturated Aminophospholipid molecular species using isotope tagged derivatives and tandem mass spectrometry mass spectrometry mass spectrometry
    Analytical Biochemistry, 2006
    Co-Authors: Karin Zemski A Berry, Robert C. Murphy

    Abstract:

    Abstract When Aminophospholipids with only saturated and monounsaturated fatty acids esterified to the glycerol backbone were labeled with isotopically enriched N-methylpiperazine acetic acid N-hydroxysuccinimide ester reagents, it was found that they could be readily detected as N-methylpiperazine-amide-tagged Aminophospholipids using a precursor scan of the stable isotope reporter ion (m/z 114–117) formed by tandem mass spectrometry/mass spectrometry. However, it was found in the current study that these precursor ion scans are not useful in determining the changes of Aminophospholipids with polyunsaturated fatty acids (PUFAs) esterified to the glycerol backbone due to the presence of interfering ions in the reporter ion region. Therefore, a method was developed using tandem mass spectrometry/mass spectrometry/mass spectrometry (MS3) to obtain reporter ion ratios that were not distorted by interfering ions present in the collision-induced dissociation spectra of nontagged Aminophospholipids with PUFAs. This new MS3 method for N-methylpiperazine- amide-tagged Aminophospholipids was used to examine the fate of diacyl, ether, or plasmalogen glycerophosphoethanolamine (GPEtn) species after exposure of human polymorphonuclear leukocytes to A23187 and granulocyte macrophage–colony-stimulating factor/formyl-methionyl-leucyl-phenylalanine stimuli, which can induce eicosanoid biosynthesis, to follow those GPEtn molecular species which were the source of arachidonic acid released. Upon stimulation of the human polymorphonuclear leukocyte, it was found that the abundant arachidonoyl GPEtn plasmalogen molecular species were uniquely reduced in relative content compared to ether or diacyl species and this subclass of GPEtn may be a source of the arachidonic acid converted to leukotrienes by the 5-lipoxygenase pathway activated in this cell.

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  • Analysis of polyunsaturated Aminophospholipid molecular species using isotope-tagged derivatives and tandem mass spectrometry/mass spectrometry/mass spectrometry
    Analytical Biochemistry, 2005
    Co-Authors: Karin A. Zemski Berry, Robert C. Murphy

    Abstract:

    Abstract When Aminophospholipids with only saturated and monounsaturated fatty acids esterified to the glycerol backbone were labeled with isotopically enriched N -methylpiperazine acetic acid N -hydroxysuccinimide ester reagents, it was found that they could be readily detected as N -methylpiperazine-amide-tagged Aminophospholipids using a precursor scan of the stable isotope reporter ion ( m / z 114–117) formed by tandem mass spectrometry/mass spectrometry. However, it was found in the current study that these precursor ion scans are not useful in determining the changes of Aminophospholipids with polyunsaturated fatty acids (PUFAs) esterified to the glycerol backbone due to the presence of interfering ions in the reporter ion region. Therefore, a method was developed using tandem mass spectrometry/mass spectrometry/mass spectrometry (MS 3 ) to obtain reporter ion ratios that were not distorted by interfering ions present in the collision-induced dissociation spectra of nontagged Aminophospholipids with PUFAs. This new MS 3 method for N -methylpiperazine- amide-tagged Aminophospholipids was used to examine the fate of diacyl, ether, or plasmalogen glycerophosphoethanolamine (GPEtn) species after exposure of human polymorphonuclear leukocytes to A23187 and granulocyte macrophage–colony-stimulating factor/formyl-methionyl-leucyl-phenylalanine stimuli, which can induce eicosanoid biosynthesis, to follow those GPEtn molecular species which were the source of arachidonic acid released. Upon stimulation of the human polymorphonuclear leukocyte, it was found that the abundant arachidonoyl GPEtn plasmalogen molecular species were uniquely reduced in relative content compared to ether or diacyl species and this subclass of GPEtn may be a source of the arachidonic acid converted to leukotrienes by the 5-lipoxygenase pathway activated in this cell.

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  • Analysis of cell membrane Aminophospholipids as isotope-tagged derivatives
    Journal of lipid research, 2005
    Co-Authors: Karin A. Zemski Berry, Robert C. Murphy

    Abstract:

    Glycerophosphoethanolamine (GPEtn) and glyc- erophosphoserine (GPSer) lipids were reacted with a multi- plexed set of differentially isotopically enriched N -methylpiper- azine acetic acid N -hydroxysuccinimide ester reagents, which place isobaric mass labels at a primary amino group. The re- sulting derivatized Aminophospholipids were isobaric and chromatographically indistinguishable but yielded positive reporter ions ( m/z 114 or 117) after collisional activation that could be used to identify and quantify individual members of the multiplex set. The chromatographic and mass spectro- metric response of N -methylpiperazine amide-tagged amino- phospholipids was probed using glycerophosphoethanol- amine and glycerophosphoserine lipid standards. The (MH) � of each tagged Aminophospholipid shifted 144 Da, and dur- ing collision-induced dissociation the major fragmentation ion was either m/z 114 or 117. This mode of detecting ami- nophospholipids was useful for an unbiased analysis of plas- malogen GPEtn lipids. Molecular species information on the esterified fatty acyl substituents was obtained by collisional activation of the (M-H) � ions. The isotope-tagged re- agents were used to assess changes in the distribution of GPEtn lipids after exposure of liposomes made from phos- pholipids extracted from RAW 264.7 cells to Cu 2 � /H 2 O 2 to illustrate the ability of these reagents to aid in the mass spec- trometric identification of Aminophospholipid changes that occur during biological stimuli. —Zemski Berry, K. A., and R. C. Murphy. Analysis of cell membrane Aminophospholipids as isotope-tagged derivatives. J. Lipid Res. 2005. 46: 1038-1046.

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Philippe F. Devaux – One of the best experts on this subject based on the ideXlab platform.

  • RECONSTITUTION OF FLIPPASE ACTIVITY INTO LIPOSOMES
    , 2014
    Co-Authors: Philippe F. Devaux

    Abstract:

    Phospholipids are asymmetrically distributed in the plasma membrane of eucaryotic cells, the Aminophospholipids being mostly on the cytosolic leaflet, whilst the choline containing phospholipids (phosphatidylcholine and sphingomyelin) are predominantly exposed on the outer leaflet [1]. There is strong evidence in support of the role of specific proteins ( ” flippases„) that are involved in the transmembrane segregation of phospholipids [1-3]. Among these proteins, some are active transporters. The Aminophospholipid translocase is a ubiquitous protein that transports selectively phosphatidylserine (PS) and phosphatidyl-ethanolamine (PE) from the outer to the inner monolayer of the plasma membranes of eucaryotic cells [1]. In the same cells, the P-glycoprotein (P-gp) and several proteins of the ABC family have been reported to transport phospholipids from the inner monolayer to the outer monolayer [2, 4]. Finally a calcium dependent ” scramblase „ plays a key role in the ATP-independent rapid lipid randomization, which takes place in stimulated platelets or during apoptotis, leading in particular to phosphatidylserine exposure on the outer cel

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  • Aminophospholipids Have No Access to the Luminal Side of the Biliary Canaliculus IMPLICATIONS FOR THE SPECIFIC LIPID COMPOSITION OF THE BILE FLUID
    The Journal of biological chemistry, 2003
    Co-Authors: Astrid Tannert, Philippe F. Devaux, Daniel Wüstner, Josefine Bechstein, Peter Müller, Andreas Herrmann

    Abstract:

    About 95% of the bile phospholipids are phosphatidylcholine. Although the fractions of phosphatidylcholine and of both Aminophospholipids phosphatidylserine and phosphatidylethanolamine in the canalicular membrane are in the same order of about 35% of total lipids, both Aminophospholipids are almost absent from the bile. To rationalize this observation, we studied the intracellular uptake of various fluorescent phospholipid analogues and their subsequent enrichment in the bile canaliculus (BC) of HepG2 cells. DiacylAminophospholipid analogues but not phosphatidylcholine analogues became rapidly internalized by an Aminophospholipid translocase (APLT) activity in the plasma membrane of HepG2 cells. We observed only low labeling of BC by diacylAminophospholipids but extensive staining by phosphatidylcholine analogues. In the presence of suramin, known to inhibit APLT, a strong labeling of BC by diacylAminophospholipid analogues was found that declined to a level observed for control cells after removal of suramin. Unlike diacylphosphatidylserine, diether phosphatidylserine analogue, which is not an appropriate substrate of APLT, accumulated in the BC. The correlation between low labeling of BC and an APLT-mediated transbilayer movement suggests the presence of an APLT activity in the canalicular membrane that prevents exposure of Aminophospholipids to the bile.

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  • drs2p related p type atpases dnf1p and dnf2p are required for phospholipid translocation across the yeast plasma membrane and serve a role in endocytosis
    Molecular Biology of the Cell, 2003
    Co-Authors: Thomas Günther Pomorski, Philippe F. Devaux, Ruben Lombardi, Howard Riezman, Gerrit Van Meer, Joost C. M. Holthuis

    Abstract:

    Plasma membranes in eukaryotic cells display asymmetric lipid distributions with Aminophospholipids concentrated in the inner and sphingolipids in the outer leaflet. This asymmetry is maintained by…

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Peter Ott – One of the best experts on this subject based on the ideXlab platform.

  • Characterization of the Correlation Between ATP‐Dependent Aminophospholipid Translocation and Mg2+‐ATPase Activity in Red Blood Cell Membranes
    European journal of biochemistry, 1997
    Co-Authors: Zsuzsa Beleznay, Alain Zachowski, Philippe F. Devaux, Peter Ott

    Abstract:

    Pseudosubstrates and inhibitors of ATPases were studied with respect to their capability to modulate the kinetic behavior of Mg2+-ATPase and Aminophospholipid translocation in red blood cell ghosts. ATP was substituted by the pseudosubstrates of P-type ATPases acetyl phosphate and p-nitrophenyl phosphate. With both pseudosubstrates, Aminophospholipid translocation from the outer to the inner leaflets of re-sealed erythrocyte ghosts could be observed, although with a significantly decreased velocity compared to that in presence of ATP, both with respect to phosphate hydrolysis and translocation. Similarly, the apparent affinities for the pseudosubstrates were much lower than for ATP. Among the inhibitors studied, suramin acted as a competitive inhibitor of ATP towards both Mg2+-ATPase activity and Aminophospholipid translocation. However, the inhibition of translocation occurred at a higher inhibitor concentration than the inhibition of Mg2+-ATPase activity. With elaiophylin, only a partial inhibition of Mg2+-ATPase activity could be detected, but translocation of labeled phosphatidylserine was almost completely abolished. With eosin Y, an almost complete inhibition of both Mg2+-ATPase activity and translocation could be achieved. The observed responses of Aminophospholipid translocation to ATPase inhibitors strongly suggest that a P-type ATPase, part of which displays a Mg2+-ATPase activity, is involved in Aminophospholipid translocation.

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  • characterization of the correlation between atp dependent Aminophospholipid translocation and mg2 atpase activity in red blood cell membranes
    FEBS Journal, 1997
    Co-Authors: Zsuzsa Beleznay, Alain Zachowski, Philippe F. Devaux, Peter Ott

    Abstract:

    Pseudosubstrates and inhibitors of ATPases were studied with respect to their capability to modulate the kinetic behavior of Mg2+-ATPase and Aminophospholipid translocation in red blood cell ghosts. ATP was substituted by the pseudosubstrates of P-type ATPases acetyl phosphate and p-nitrophenyl phosphate. With both pseudosubstrates, Aminophospholipid translocation from the outer to the inner leaflets of re-sealed erythrocyte ghosts could be observed, although with a significantly decreased velocity compared to that in presence of ATP, both with respect to phosphate hydrolysis and translocation. Similarly, the apparent affinities for the pseudosubstrates were much lower than for ATP. Among the inhibitors studied, suramin acted as a competitive inhibitor of ATP towards both Mg2+-ATPase activity and Aminophospholipid translocation. However, the inhibition of translocation occurred at a higher inhibitor concentration than the inhibition of Mg2+-ATPase activity. With elaiophylin, only a partial inhibition of Mg2+-ATPase activity could be detected, but translocation of labeled phosphatidylserine was almost completely abolished. With eosin Y, an almost complete inhibition of both Mg2+-ATPase activity and translocation could be achieved. The observed responses of Aminophospholipid translocation to ATPase inhibitors strongly suggest that a P-type ATPase, part of which displays a Mg2+-ATPase activity, is involved in Aminophospholipid translocation.

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  • ATP-dependent Aminophospholipid translocation in erythrocyte vesicles: stoichiometry of transport.
    Biochemistry, 1993
    Co-Authors: Zsuzsa Beleznay, Alain Zachowski, Philippe F. Devaux, Marta Puente Navazo, Peter Ott

    Abstract:

    Vesicles released from human red blood cells by incubation with a suspension of sonicated dimyristoylphosphatidylcholine were purified by gel filtration. Purified vesicles and intact red cells had a very similar composition with respect to phospholipids and integral membrane proteins, but spectrin, the major component of the membrane skeleton, was not found in vesicles. Comparison of red cell and vesicle ATP levels (expressed as micromolar ATP per millimolar hemoglobin) showed a marked difference with a reduced content of only about 30% in vesicles, whatever the initial concentration in the erythrocytes. Spin-labeled Aminophospholipids (phosphatidylserine and phosphatidylethanolamine) were translocated to the inner vesicle membrane layer at a comparable rate as in intact red cells provided that vesicles contained enough ATP. The maximum fraction of spin-labeled phospholipids translocated to the inner membrane layer was 84% for phosphatidylserine, 65% for phosphatidylethanolamine, 20-40% for phosphatidylcholine, and below 20% for sphingomyelin. The apparent Km of translocation, expressed as percent of total membrane phospholipid, was 0.14% for spin-labeled phosphatidylserine and 1.19% for spin-labeled phosphatidylethanolamine. This compares well to values established earlier for intact red blood cells. The fact that no ATP was synthesized in vesicles allowed determination of ATP consumption by Aminophospholipid transport. The basic ATP hydrolysis rate was increased upon the addition of labeled Aminophospholipids but not of labeled phosphatidylcholine or sphingomyelin. The stoichiometry between lipid translocation and ATP consumption, calculated from the respective initial velocities, was 1.13 +/- 0.2 for phosphatidylserine and 1.11 +/- 0.16 for phosphatidylethanolamine.

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