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Journal of Lipid Research, Vol. 47, 2781-2788, December 2006 Ceramide structural features required to stimulate ABCA1-mediated cholesterol efflux to apolipoprotein A-I
Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, OH 45237-0507 Published, JLR Papers in Press, September 21, 2006.
1 To whom correspondence should be addressed. e-mail: sean.davidson{at}uc.edu
Ceramide is a component of the sphingomyelin cycle and a well-established lipid signaling molecule. We recently reported that ceramide specifically increased ABCA1-mediated cholesterol efflux to apolipoprotein A-I (apoA-I), a critical process that leads to the formation of cardioprotective HDL. In this report, we characterize the structural features of ceramide required for this effect. C2 dihydroceramide, which contains a fully saturated acyl chain and is commonly used as a negative control for ceramide apoptotic signaling, stimulated a 2- to 5-fold increase in ABCA1-mediated cholesterol efflux to apoA-I over a 060 µM concentration range without the cell toxicity apparent with native C2 ceramide. Compared with C2 ceramide, C6 and C8 ceramides with medium-length N-acyl chains showed a similar extent of efflux stimulation (a 2- to 5-fold increase) but at a higher onset concentration than the less hydrophobic C2 ceramide. In contrast, the reduced and methylated ceramide analogs, N,N-dimethyl sphingosine and N,N,N-trimethyl sphingosine, failed to stimulate cholesterol efflux. We found that changes in the native spatial orientation at either of two chiral carbon centers (or both) resulted in an
Supplementary key words chemical structure stereochemistry ATP binding cassette type A1 Abbreviations: apoA-I, apolipoprotein A-I; CAPK, ceramide-activated protein kinase; CAPP, ceramide-activated protein phosphatase; DMS, N,N-dimethyl sphingosine; PVDF, polyvinylidene difluoride; TMS, N,N,N-trimethyl sphingosine
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