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Biophys. J. BioFAST: First Published January 14, 2005. doi:10.1529/biophysj.104.057059
© 2005 by the Biophysical Society.

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MEMBRANES

The 3-Hydroxy Group and 4,5-trans Double Bond of Sphingomyelin are Essential for Modulation of Galactosylceramide Transmembrane Asymmetry

Barbara Malewicz 1, Jacob T. Valiyaveettil 2, Kochurani Jacob 2, Hoe-Sup Byun 2, Peter Mattjus 1, Wolfgang J. Baumann 1, Robert Bittman 2 and Rhoderick E. Brown 1*

1 University of Minnesota
2 Queens College of CUNY

* To whom correspondence should be addressed. E-mail: reb{at}umn.edu.

Submitted on November 24, 2004
Revised on December 21, 2004
Accepted on 10 January 2005


  Abstract
The structural features of sphingomyelin (SPM) that control the transbilayer distribution of â galactosylceramide(GalCer) in 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC)vesicles were investigated by 13C and 31P NMR spectroscopy using lipid analogs that share physical similarities with GalCer or SPM. The SPM analogs included N-palmitoyl-4,5-dihydro-SPM, 3-deoxy-SPM, 1 alkyl-2-amidophosphatidylcholine, and dipalmitoylphosphatidylcholine, a popular model 'raft lipid.' The transbilayer distributions of the SPM analogs and SPM in POPC vesicles were similar by 31P NMR. To observe the dramatic change in GalCer transbilayer distribution that occurs when SPM is included in POPC vesicles [Mattjus et al., J. Biol. Chem. 277, 19476-19481 (2002)], the 3 OH group, 4,5-trans double bond, and amide linkage all were required in SPM. However, inclusion of 2 and 10 mol% dihydroSPM in SPM/POPC (1:1) vesicles mitigated and completely abrogated the effect of SPM on the transbilayer distribution of GalCer. Despite sharing some structural features with GalCer and localizing preferentially to the inner leaflet of POPC vesicles, dimyristoylphosphatidylethanolamine did not undergo a change in transbilayer distribution when SPM was incorporated into the vesicles. The results support the hypothesis that specific interactions may be favored among select sphingolipids in high-curvature membranes and emphasize the potential importance of the SPM-dihydroSPM ratio in membrane fission and fusion processes associated with vesicle biogenesis and trafficking.

Key Words: 13C-NMR of glycolipid, 31P-NMR of phospholipids, cerebroside, dihydrosphingomyelin, membrane curvature stress, phosphatidylethanolamine




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C. D. Blanchette, W.-C. Lin, T. V. Ratto, and M. L. Longo
Galactosylceramide Domain Microstructure: Impact of Cholesterol and Nucleation/Growth Conditions
Biophys. J., June 15, 2006; 90(12): 4466 - 4478.
[Abstract] [Full Text] [PDF]


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Copyright © 2005 by the Biophysical Society.