The Lipid Moiety of the GPI-Anchor of the Major Plasma Membrane Proteins in Paramecium primaurelia is a Ceramide: Variation of the Amide-Linked Fatty Acid Composition as a Function of Growth Temperature

• Published in: Protist Vol. 149; no. 1; pp. 39 - 50
• Main Authors: Benwakrim, Abdellatif, Trémolière, Antoine, Labarre, Jean, Capdeville, Yvonne
• Format: Journal Article
• Language: English
• Published: Germany Elsevier GmbH 01.02.1998
• Subjects: Paramecium primaurelia; GPI; GPI-PLC; FAME; pCMPSA; SAg; LCB; PI-PLC; SGP
• ISSN: 1434-4610; 1618-0941
• DOI: 10.1016/S1434-4610(98)70008-2

The major membrane proteins of Paramecium are anchored in the plasma membrane via a glycosylphosphatidylinositol (GPI). The expression of these GPI-proteins, the surface antigen (SAg) and the surface GPI-proteins (SGPs), is temperature-dependent, different sets are expressed at 23 °C and at 32 °C. To characterize the GPI-anchor lipid moieties of these proteins, a new strategy of biosynthetic radiolabeling was developed. Cells of Paramecium primaurelia, grown at 23 °C or at 32 °C, were fed with [ 14C]-labeled cyanobacteria. The paramecia metabolized the cyanobacteria lipids and synthesized fatty acids with longer and more unsaturated chains. The SAg and SGPs from [ 14C]-labeled paramecia, were purified and the lipid moieties of their GPI-anchors were cleaved by a Bacillus thuringiensis phosphatidylinositol-specific phospholipase C and identified as ceramides. The GPI-anchor ceramides, from the SAg and SGPs expressed at both temperatures, contained long-chain bases which did not display variations detectable upon thin layer chromatography analysis. In contrast, the amide-linked fatty acid component varied: palmitic acid was identified as the major amidelinked fatty acid in the GPI-protein anchors from paramecia grown at 23 °C, while at 32 °C a C 14 fatty acid could be the prominent fatty acid. This modulation in the fatty acid composition could playa role in the antigenic variation process.