Temperature-dependent changes in plasma-membrane lipid order and the phagocytotic activity of the amoeba Acanthamoeba castellanii are closely correlated. 1995

S V Avery, and D Lloyd, and J L Harwood
School of Molecular and Medical Biosciences, School of Pure and Applied Biology, University of Wales College of Cardiff, U.K.

The relationship between temperature-dependent changes in phagocytotic activity of Acanthamoeba castellanii and the fatty acid composition and physical properties of plasma membrane-enriched fractions were determined in cultures acclimated to 30 degrees C and 15 degrees C. Chilling (from 30 degrees C to 15 degrees C) had a very pronounced short-term inhibitory effect on phagocytosis only in stationary-phase cultures, which displayed a low degree of fatty acid unsaturation. A subsequent increase in phagocytosis by these cells was correlated with a low-temperature-induced increase in fatty acid unsaturation (shown previously [Jones, Lloyd and Harwood (1993) Biochem. J. 296, 183-188] to be due to n-6 desaturase induction). Plasma membrane-enriched fractions from 15 degrees C-acclimated cells also showed a marked increase in the relative proportion of polyunsaturated fatty acids. Steady-state fluorescence depolarization studies, using the membrane probe diphenylhexatriene, revealed increases in plasma membrane order with decreasing assay temperature. Over the upper assay-temperature range (25-40 degrees C), fluorescence anisotropy values were higher in membranes from 30 degrees C-acclimated cells; a 3.3 degrees C relative displacement of plots indicated that temperature-induced changes in membrane lipid composition compensated for approx. 22% of the ordering effect of low temperature. Changes in the temperature-dependence of fluorescence anisotropy, possibly corresponding to lateral phase separations or alterations in other bulk physical properties of membranes, occurred between 20 and 25 degrees C in membranes from 30 degrees C-acclimated cells and between 15 and 20 degrees C in membranes from 15 degrees C-acclimated cells. Fluorescence anisotropy plots were superimposed at assay temperatures between 5 and 15 degrees C. Short-term phagocytotic rates in whole cells decreased with assay temperature. Arrhenius discontinuities in rates of phagocytosis occurred at approx. 25.0 degrees C and 17.5 degrees C in 30 degrees C- and 15 degrees C-acclimated cells respectively, and in each case were thus within the temperature ranges of slope-change in the corresponding fluorescence anisotropy plots. The results show a direct correlation between plasma membrane fatty acid unsaturation, membrane physical properties and phagocytotic activity in A. castellanii. Therefore, a specific integrated physiological process has been correlated with fatty acid desaturase induction for the first time.

UI MeSH Term Description Entries
D008563 Membrane Lipids Lipids, predominantly phospholipids, cholesterol and small amounts of glycolipids found in membranes including cellular and intracellular membranes. These lipids may be arranged in bilayers in the membranes with integral proteins between the layers and peripheral proteins attached to the outside. Membrane lipids are required for active transport, several enzymatic activities and membrane formation. Cell Membrane Lipid,Cell Membrane Lipids,Membrane Lipid,Lipid, Cell Membrane,Lipid, Membrane,Lipids, Cell Membrane,Lipids, Membrane,Membrane Lipid, Cell,Membrane Lipids, Cell
D010587 Phagocytosis The engulfing and degradation of microorganisms; other cells that are dead, dying, or pathogenic; and foreign particles by phagocytic cells (PHAGOCYTES). Phagocytoses
D002462 Cell Membrane The lipid- and protein-containing, selectively permeable membrane that surrounds the cytoplasm in prokaryotic and eukaryotic cells. Plasma Membrane,Cytoplasmic Membrane,Cell Membranes,Cytoplasmic Membranes,Membrane, Cell,Membrane, Cytoplasmic,Membrane, Plasma,Membranes, Cell,Membranes, Cytoplasmic,Membranes, Plasma,Plasma Membranes
D002627 Chemistry, Physical The study of CHEMICAL PHENOMENA and processes in terms of the underlying PHYSICAL PHENOMENA and processes. Physical Chemistry,Chemistries, Physical,Physical Chemistries
D003080 Cold Temperature An absence of warmth or heat or a temperature notably below an accustomed norm. Cold,Cold Temperatures,Temperature, Cold,Temperatures, Cold
D004161 Diphenylhexatriene A fluorescent compound that emits light only in specific configurations in certain lipid media. It is used as a tool in the study of membrane lipids. 1,6-Diphenyl-1,3,5-hexatriene,1,6-Diphenylhexatriene,1,6 Diphenylhexatriene
D005227 Fatty Acids Organic, monobasic acids derived from hydrocarbons by the equivalent of oxidation of a methyl group to an alcohol, aldehyde, and then acid. Fatty acids are saturated and unsaturated (FATTY ACIDS, UNSATURATED). (Grant & Hackh's Chemical Dictionary, 5th ed) Aliphatic Acid,Esterified Fatty Acid,Fatty Acid,Fatty Acids, Esterified,Fatty Acids, Saturated,Saturated Fatty Acid,Aliphatic Acids,Acid, Aliphatic,Acid, Esterified Fatty,Acid, Saturated Fatty,Esterified Fatty Acids,Fatty Acid, Esterified,Fatty Acid, Saturated,Saturated Fatty Acids
D005231 Fatty Acids, Unsaturated FATTY ACIDS in which the carbon chain contains one or more double or triple carbon-carbon bonds. Fatty Acids, Polyunsaturated,Polyunsaturated Fatty Acid,Unsaturated Fatty Acid,Polyunsaturated Fatty Acids,Acid, Polyunsaturated Fatty,Acid, Unsaturated Fatty,Acids, Polyunsaturated Fatty,Acids, Unsaturated Fatty,Fatty Acid, Polyunsaturated,Fatty Acid, Unsaturated,Unsaturated Fatty Acids
D005454 Fluorescence Polarization Measurement of the polarization of fluorescent light from solutions or microscopic specimens. It is used to provide information concerning molecular size, shape, and conformation, molecular anisotropy, electronic energy transfer, molecular interaction, including dye and coenzyme binding, and the antigen-antibody reaction. Anisotropy, Fluorescence,Fluorescence Anisotropy,Polarization, Fluorescence,Anisotropies, Fluorescence,Fluorescence Anisotropies,Fluorescence Polarizations,Polarizations, Fluorescence
D005456 Fluorescent Dyes Chemicals that emit light after excitation by light. The wave length of the emitted light is usually longer than that of the incident light. Fluorochromes are substances that cause fluorescence in other substances, i.e., dyes used to mark or label other compounds with fluorescent tags. Flourescent Agent,Fluorescent Dye,Fluorescent Probe,Fluorescent Probes,Fluorochrome,Fluorochromes,Fluorogenic Substrates,Fluorescence Agents,Fluorescent Agents,Fluorogenic Substrate,Agents, Fluorescence,Agents, Fluorescent,Dyes, Fluorescent,Probes, Fluorescent,Substrates, Fluorogenic

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