Opossum Kidney Cells Expressing EGFP-Endosomes
A variety of materials are incorporated into an organelle known as the endosome through receptor-mediated endocytosis. In addition, several extracellular molecules bind to transmembrane receptor proteins that efficiently accumulate in coated pits. Receptor-mediated endocytosis, which is important in human physiology, is the main mechanism by which cholesterol is taken up by cells, in particular, liver cells. Cholesterol is carried in the blood primarily by low density lipoproteins (LDL). In many individuals, the LDL receptor is defective, so uptake of cholesterol-containing LDL from the blood into liver cells is reduced and LDL-cholesterol accumulates in the blood. This artifact is thought to be the cause of damage to blood vessel walls, as elevated LDL levels result in their penetration into the wall of arteries and causes atherosclerosis, the primary cause of heart attacks and strokes. In the digital videos presented above, normal opossum kidney epithelial cells (OK line) are imaged expressing enhanced green fluorescent protein (EGFP) fused to a peptide targeting signal for the endosomes.