There are two genetic mutations that cause either no uptake of LDL receptors or uptake and accumulation of cholesterol in late endosomes. We will look at these diseases to learn more the importance of Key elements in receptor mediated endocytosis are. First, this cartoon summarizes the entire process of endocytosis of LDL-cholesterol bound to LDL receptors. To review, after the ligand and receptors are collected in the coated pits, which then form coated vesicles, the clathrin coat is removed and the vesicle fuses with forming endosomes. The early endosome allows recycling of the LDL receptor.
Free cholesterol is then available to be used by the cell.
This requires a specific LDL receptor and a working receptor mediated endocytosis process. Some families have a defect in the Adaptin-2 binding site on the LDL receptor. Recall that this site helped concentrate the LDL receptor in the coated pit. In fact, binding to the Adaptor protein actually helped recruit the clathrin to the site. The defect is shown in the above cartoon from your text.