Figure 1.
Non-vesicular sterol transport pathways in cells. Pathways that are only speculative are marked with a “?”. Non-vesicular sterol transport pathways probably move sterols between the ER and many organelles, perhaps at membrane contact sites. Organelles shown: endoplasmic reticulum (ER), plasma membrane (PM), inner mitochondrial membrane (IMM), outer mitochondrial membrane (OMM), endocytic recycling compartment (ERC), lipid droplet (LD), and external acceptor, which could be a lipoproteins or detergent micelle depending on cell type. Some of the proteins mentioned in the text are shown in blue. It should be noted that all of these proteins are not expressed in the same cells.