Cholesterol processing, illustration. Cholesterol molecules (yellow) are transported by low-density lipoprotein (LDL) particles. The particles bind to LDL receptors on a cell's membrane, resulting in their endocytosis through the cell membrane into clathrin-coated endosomes. Once inside the cell the cholesterol is transported to a lysosome where Niemann-Pick C2 (NPC2) proteins transport the cholesterol molecules to NPC1 proteins embedded in the membrane. NPC1 moves the cholesterol out of the lysosome and delivers it to the endoplasmic reticulum for further processing. For an unlabelled version of this image see F032/7640.