Signal Transduction via Glycosyl Phosphatidylinositol-anchored Proteins in T Cells Is Inhibited by Lowering Cellular Cholesterol*
- Thomas M. Stulnig‡§,
- Markus Berger‡,
- Thomas Sigmund‡,
- Hannes Stockinger¶,
- Václav Hořejšı́‖ and
- Werner Waldhäusl‡
- From the ‡Department of Internal Medicine III, University of Vienna, Währinger Gürtel 18-20, A-1090 Vienna, Austria, ¶Institute of Immunology, Vienna International Research Cooperation Center, University of Vienna, Brunnerstrasse 59, A-1235 Vienna, Austria and ‖Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Vı́deňská1083, 14220 Prague 4, Czech Republic
Abstract
Glycosylphosphatidylinositol (GPI)-anchored proteins can deliver costimulatory signals to lymphocytes, but the exact pathway of signal transduction involved is not yet characterized. GPI-anchored proteins are fixed to the cell surface solely by a phospholipid moiety and are clustered in distinct membrane domains that are formed by an unique lipid composition requiring cholesterol. To elucidate the role of membrane lipids for signal transduction via GPI-anchored proteins, we studied the influence of reduced cellular cholesterol content on calcium signaling via GPI-anchored CD59 and CD48 in Jurkat T cells. Lowering cholesterol by different inhibitors of cellular cholesterol synthesis suppressed calcium response via GPI-anchored proteins by about 50%, whereas stimulation via CD3 was only minimally affected (<10%). The decrease in overall calcium response via GPI-anchored proteins was reflected by inhibition of calcium release from intracellular stores. Cell surface expression of GPI-anchored proteins was not changed quantitatively by lowering cellular cholesterol, and neither was the pattern of immunofluorescence in microscopic examination. In addition, the distribution of GPI-anchored proteins in detergent-insoluble complexes remained unaltered. These results suggest that cellular cholesterol is an important prerequisite for signal transduction via GPI-anchored proteins beyond formation of membrane domains.
Footnotes
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↵* This work was supported by the Austrian Science Foundation, project P11404-Med.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵§ To whom correspondence should be addressed. Tel.: 43-1-40400-4338; Fax: 43-1-40400-7790; E-mail: Thomas.Stulnig{at}akh-wien.ac.at.
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↵1 The abbreviations used are: GPI, glycosylphosphatidylinositol; GAM, goat anti-mouse; PI-PLC, phosphatidylinositol-specific phospholipase C; TCR, T cell receptor; FR, fluorescence ratio.
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- Received April 22, 1997.
- Revision received May 28, 1997.
