Poster Presentation 2014 International Biophysics Congress

Membrane permeabilization induced by sphingosine: Effect of negatively-charged lipids (#299)

Alicia Alonso 1 , Noemi Jimenez-Rojo 1 , Jesús Sot 1 , Ana R. Viguera 1 , M. Isabel Collado 2 , Alejandro Torrecillas 3 , Juan C. Gomez-Fernandez 4 , Feliz M Goni 1
  1. Biophysics Unit CSIC-UPV/EHU, Deparment of Biochemistry and Molecular Biology, University of the Basque Country, Leioa, Bizkaia, Spain
  2. SGiker, University of the Basque Country, Leioa, Bizkaia, Spain
  3. Molecular Biology, Research Support Service, University of Murcia, Murcia, Spain
  4. Department of Biochemistry and Molecular Biology-A, Faculty of Veterinary, University of Murcia, Regional Campus of International Excellence Campus Mare Nostrum, Murcia, Spain

Sphingosine [(2S, 3R, 4E)-2-amino-4-octadecen-1, 3-diol] is the most common sphingoid long chain base in sphingolipids. It is the precursor of important cell signalling molecules, such as ceramides. In the last decade it has been shown to act itself as a potent metabolic signalling molecule, by activating a number of protein kinases. Moreover, sphingosine has been found to permeabilize phospholipid bilayers, giving rise to vesicle leakage. The present contribution intends to analyze the mechanism by which this bioactive lipid induces vesicle contents release, and the effect of negatively charged bilayers in the release process. Fluorescence lifetime measurements and confocal fluorescence microscopy have been applied to observe the mechanism of sphingosine efflux from large and giant unilamellar vesicles, a graded-release efflux has been detected. Additionally, stopped-flow measurements have shown that the rate of vesicle permeabilization increases with sphingosine concentration. Since at the physiological pH sphingosine has a net positive charge, its interaction with negatively charged phospholipids (e.g. bilayers containing phosphatidic acid together with sphingomyelins, phosphatidylethanolamine and cholesterol) gives rise to a release of vesicular contents, faster than with electrically neutral bilayers. Furthermore, 31P-NMR and X-ray data show the capacity of sphingosine to facilitate the formation of non-bilayer (cubic phase) intermediates in negatively charged membranes. The data might explain the pathogenesis of Niemann-Pick type C1 disease.

This work was supported in part by grants from the Spanish Ministerio de Economia (BFU 2012-36241 to FMG, BFU 2011-28566 to AA) and from the Basque Government (N.F.-R. was predoctoral student supported by the Basque Government).