OpenStax Biology 2e
A targeted variation of endocytosis employs receptor proteins in the plasma membrane that have a specific binding affinity for certain substances.
In receptor-mediated endocytosis, as in phagocytosis, clathrin attaches to the plasma membrane’s cytoplasmic side. If a compound’s uptake is dependent on receptor-mediated endocytosis and the process is ineffective, the material will not be removed from the tissue fluids or blood. Instead, it will stay in those fluids and increase in concentration. The failure of receptor-mediated endocytosis causes some human diseases. For example, receptor mediated endocytosis removes low density lipoprotein or LDL (or “bad” cholesterol) from the blood. In the human genetic disease familial hypercholesterolemia, the LDL receptors are defective or missing entirely. People with this condition have life-threatening levels of cholesterol in their blood, because their cells cannot clear LDL particles.
Although receptor-mediated endocytosis is designed to bring specific substances that are normally in the extracellular fluid into the cell, other substances may gain entry into the cell at the same site. Flu viruses, diphtheria, and cholera toxin all have sites that cross-react with normal receptor-binding sites and gain entry into cells.– What is an intermediate or end product of metabolism?
Clathrin-mediated endocytosis is the main portal of entry into the cell for many soluble and membrane molecules. Clathrin-coated vesicles are formed from the plasma membrane in a sequence of coordinated protein-lipid and protein-protein interactions, starting with adaptor-mediated recruitment of clathrin to the membrane, proceeding to clathrin polymerization and assembly into deeply curved coated buds, and ending with the dynamin-dependent scission of a coated vesicle. Clathrin coats trap and concentrate endocytic cargo by using a multitude of adaptor proteins that recognize specific sequence motifs in the cytosolic domains of receptors and other transmembrane cargo molecules. Endocytic cargo that is concentrated in this manner, such as signaling receptors, may regulate the stability, size, and dynamics of individual clathrin coats and thereby influence endocytosis.
Clark, M., Douglas, M., Choi, J. Biology 2e. Houston, Texas: OpenStax. Access for free at: https://openstax.org/details/books/biology-2e