Measurement of Intracellular Sterol Transport in Yeast.

Intracellular sterol transport occurs largely by non-vesicular mechanisms in which sterol transport proteins extract sterol from one membrane and transfer it to another across the cytoplasm. Here we describe a suite of complementary assays to measure intracellular sterol transport in the model eukaryote Saccharomyces cerevisiae, as well as to quantify protein-mediated sterol transport between populations of vesicles in vitro. The in vivo assays can be adapted to study sterol transport in other cell types.

Regulation of ABCA1-mediated cholesterol efflux by sphingosine-1-phosphate signaling in macrophages.

Sphingolipid and cholesterol metabolism are closely associated at the structural, biochemical, and functional levels. Although HDL-associated sphingosine-1-phosphate (S1P) contributes to several HDL functions, and S1P signaling regulates glucose and lipid metabolism, no study has addressed the involvement of S1P in cholesterol efflux. Here, we show that sphingosine kinase (Sphk) activity was induced by the LXR agonist 22(R)-hydroxycholesterol and required for the stimulation of ABCA1-mediated cholesterol efflux to apolipoprotein A-I.