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Nelson J, Diehl II, Palfreeman AF, Gibby J, Bell JD. Ultraslow dynamics of a complex amphiphile within the phospholipid bilayer: Effect of the lipid pre-transition. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2017; 1859:2068-2075. [PMID: 28751091 DOI: 10.1016/j.bbamem.2017.07.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 07/01/2017] [Accepted: 07/23/2017] [Indexed: 06/07/2023]
Abstract
The shape and intensity of fluorescence emission spectra of Merocyanine 540 embedded in dipalmitoylphosphatidylcholine bilayers differ depending on the thermal history of the sample. This apparent hysteresis in fluorescence emission was most prominent in the temperature range of 20 to 35°C. Analysis of kinetic and temperature cycling experiments suggested that Merocyanine 540 slowly (half time of about 30min) assumes a metastable configuration as temperature is raised above the phospholipid pre-transition point. When the sample was cooled below the pre-transition temperature, the metastable state slowly depopulated (half time of about 15min). The rate of merocyanine exchange among these states was influenced more by membrane lipid mobility than by lipid order since cholesterol increased the rate of transition to the metastable state by a factor of 11.
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Affiliation(s)
- Jennifer Nelson
- Department of Physiology and Developmental Biology, Brigham Young University, United States
| | - Izadora I Diehl
- Department of Physiology and Developmental Biology, Brigham Young University, United States
| | - Alyssa F Palfreeman
- Department of Physiology and Developmental Biology, Brigham Young University, United States
| | - Jared Gibby
- Department of Physiology and Developmental Biology, Brigham Young University, United States
| | - John D Bell
- Department of Physiology and Developmental Biology, Brigham Young University, United States.
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Degrelle SA, Gerbaud P, Leconte L, Ferreira F, Pidoux G. Annexin-A5 organized in 2D-network at the plasmalemma eases human trophoblast fusion. Sci Rep 2017; 7:42173. [PMID: 28176826 PMCID: PMC5297248 DOI: 10.1038/srep42173] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Accepted: 11/30/2016] [Indexed: 12/13/2022] Open
Abstract
Only a limited number of human cells can fuse to form a multinucleated syncytium. Cell fusion occurs as part of the differentiation of some cell types, including myotubes in muscle and osteoclasts in remodeling bone. In the differentiation of the human placenta, mononuclear cytotrophoblasts aggregate and fuse to form endocrinologically active, non-proliferative, multinucleated syncytia. These syncytia allow the exchange of nutrients and gases between the maternal and fetal circulation. Alteration of syncytial formation during pregnancy affects fetal growth and the outcome of the pregnancy. Here, we demonstrate the role of annexin A5 (AnxA5) in syncytial formation by cellular delivery of recombinant AnxA5 and RNA interference. By a variety of co-immunoprecipitation, immunolocalization and proximity experiments, we show that a pool of AnxA5 organizes at the inner-leaflet of the plasma membrane in the vicinity of a molecular complex that includes E-Cadherin, α-Catenin and β-Catenin, three proteins previously shown to form adherens junctions implicated in cell fusion. A combination of knockdown and reconstitution experiments with AnxA5, with or without the ability to self-assemble in 2D-arrays, demonstrate that this AnxA5 2D-network mediates E-Cadherin mobility in the plasmalemma that triggers human trophoblasts aggregation and thereby cell fusion.
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Affiliation(s)
- Severine A Degrelle
- INSERM, U767, Cell fusion, Paris, F-75006 France.,Université Paris Descartes, Paris, F-75006 France.,PremUp, Paris, F-75006 France
| | - Pascale Gerbaud
- INSERM, U767, Cell fusion, Paris, F-75006 France.,Université Paris Descartes, Paris, F-75006 France.,UMR-S1180, Inserm, Univ. Paris-Sud, Université Paris-Saclay, Châtenay-Malabry, France
| | - Ludovic Leconte
- UMR144, Institut Curie/CNRS, Cell and Tissue Imaging Platform, Paris, France
| | - Fatima Ferreira
- INSERM, U767, Cell fusion, Paris, F-75006 France.,Université Paris Descartes, Paris, F-75006 France
| | - Guillaume Pidoux
- INSERM, U767, Cell fusion, Paris, F-75006 France.,Université Paris Descartes, Paris, F-75006 France.,PremUp, Paris, F-75006 France.,UMR-S1180, Inserm, Univ. Paris-Sud, Université Paris-Saclay, Châtenay-Malabry, France
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Djaldetti M, Bessler H. High temperature affects the phagocytic activity of human peripheral blood mononuclear cells. Scandinavian Journal of Clinical and Laboratory Investigation 2015; 75:482-6. [PMID: 26067609 DOI: 10.3109/00365513.2015.1052550] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
BACKGROUND The ability for engulfment of pathogens and inert particles is the key hallmark of the phagocytic cells. Phagocytes play a significant role in the modulation of local or extended inflammation. Since fever activates a number of factors linked with the immune response it was the goal of this study to examine the in vitro effect of hyperthermia on the phagocytic capacity, the number of phagocytic cells and the viability of human peripheral blood mononuclear cells (PBMC) at 37 and 40°C. METHODS PBMC were incubated with 0.8 μm polysterene latex beads, for 2 hours at 37 and 40°C. The number of phagocytic cells, and that of latex particles internalized by each individual cell was counted with a light microscope. In addition, the percentage of viable cells and the number of active metabolic cells was evaluated. RESULTS A temperature of 40°C significantly increased the number of phagocytic cells and the phagocytic index by 41 and 37% respectively, as compared to cells incubated at 37°C. While the number of vital cells (trypan blue test) did not differ statistically at both temperatures, the number of active metabolic cells (XTT test) after 2 h of incubation at 40°C was 17% higher as compared with that at 37°C. However, the number of active metabolic cells after 24 h of incubation at 40°C was 51% lower compared with cells incubated at 37°C. CONCLUSIONS The increased phagocytic capacity of human peripheral blood monocytes at high temperature further enlightens the immunomodulatory effect of fever in the immune responses during inflammation.
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Affiliation(s)
- Meir Djaldetti
- Laboratory for Immunology and Hematology Research, Rabin Medical Center, Hasharon Hospital,Petah-Tiqva, and the Sackler School of Medicine, Tel-Aviv University , Ramat-Aviv , Israel
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