Nuclear receptors, cholesterol homeostasis and the immune system.

Cholesterol is essential for maintaining membrane fluidity in eukaryotes. Additionally, the synthetic cascade of cholesterol results in precursor molecules important for cellular function such as lipid raft formation and protein prenylation. As such, cholesterol homeostasis is tightly regulated. Interestingly, it is now known that some cholesterol precursors and many metabolites serve as active signaling molecules, binding to different classes of receptors including the nuclear receptors. Furthermore, many cholesterol metabolites or their nuclear receptors have been implicated in the regulation of the immune system in normal physiology and disease. Therefore, in this focused review, cholesterol homeostasis and nuclear receptors involved in this regulation will be discussed, with particular emphasis on how these cascades influence the immune system.