Intracellular cholesterol transport.

The intracellular movement of cholesterol in mammalian cells may involve complex pathways by which the sterol moves to various cellular sites and mediates transcriptional regulation, enzyme activation, and protein degradation. Current evidence indicates that there are three distinct pathways modulating intracellular cholesterol trafficking. The movement of endogenously synthesized cholesterol from the endoplasmic reticulum appears to be distinct from movement of exogenous, low density lipoprotein (LDL)-derived cholesterol to the plasma membrane. In addition, steroidogenic cells possess a third mechanism by which cholesterol is transported to the mitochondria to initiate steroid hormone synthesis. In this review, we have outlined the current knowledge of cholesterol transport mechanisms and pathways and have described approaches that may help define cholesterol trafficking mechanisms in molecular detail. The use of genetic and molecular biologic techniques can potentially reveal gene products that are involved in intracellular cholesterol transport and regulation as well as those that may secondarily affect this process.