Journal
BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES
Volume 1778, Issue 12, Pages 2727-2739Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.bbamem.2008.07.025
Keywords
Ceramide; Cholesterol; Sphingomyelin; Lipid signaling pathways
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Funding
- Human Frontier Science Programme [RGP0016/2005C]
- Bulgarian Ministry of Education and Science
- National Programme for Development of Scientific Potential
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egg phosphatidylcholine, egg sphingomyelin, egg ceramide and cholesterol have been determined. The coexistence of gel, liquid-ordered and liquid-disordered structure has been determined by peak fitting analysis of synchrotron X-ray powder patterns. order parameters and extent of distribution of 16-doxyl-stearic acid spin probe between ordered and disordered environments has been estimated by ESR spectral simulation methods. The presence of ceramide in proportions up to 20 mol% in phosphatidylcholine is characterized by gel-fluid phase coexistence at temperatures up to 46 degrees C depending on the amount of ceramide. Cholesterol tends to destabilize the ceramide-rich domains formed in phosphatidylcholine while sphingomyelin, by formation of stable complexes with ceramide, tends to stabilize these domains. The stability of sphingomyelin-ceramide complexes is evident from the persistence of highly ordered structure probed by ESR spectroscopy and appearance of a sharp wide-angle X-ray reflection at temperatures higher than the gel-fluid transition of ceramide alone in egg phosphatidylcholine bilayers. The competition between ceramide and cholesterol for interaction with sphingomyelin is discussed in terms of control of lipid-mediated signaling pathways by sphingomyelinase and phospholipase A(2). Crown Copyright (C) 2008 Published by Elsevier B.V. All rights reserved.
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