the mechanism of receptor mediated endocytosis explained
The Mechanism of Receptor-mediated Endocytosis Explained
Receptor-mediated endocytosis is a process in which receptors are used for importing material from extra-cellular matrix into the cells. The following Buzzle article elaborates more on this cellular process critical for the growth and development of cells.
Did You Know?
If endocytosis, an important cellular process is not taking place properly, it may cause chronic ailments like leukemia and Alzheimer's disease.- Whenever a receptor (molecule) that is embedded within the plasma membrane, detects a molecule (that it can bind to) outside the cell, it immediately hooks onto it. The molecule (ligand) attached to the receptor then travels all the way to the clathrin-coated pit.
- A clathrin-coated pit is a special area located on the plasma membrane that initiates the uptake of molecules present in the extracellular region. The pit shows a distinct polygonal lattice of clathrin chains on its inner surface. When the receptor-molecule reaches the clathrin-coated pit, it is observed that the pit folds inwards and then that part of the membrane detaches itself to form a closed coated vesicle.
- These vesicles act as tools to move molecules inside the cells. Simply put, they transport molecules within the cells. If the receptor-bound molecule is a pathogen, opsonization mechanism is activated, meaning the molecule is tagged as a pathogen for subsequent destruction. After opsonization, the protein coat of clathrin is shaken off to allow the vesicle to merge with an early endosome.
- An early endosome is an organelle, a sorting compartment that helps separate the molecule from its receptor. Once the vesicle fuses with the endosome, multiple compartments are formed within the endosome and at the same time the molecule detaches itself from the receptor.
- Chemical changes occur within the endosome to form a late endosome. The late endosome splits into two, in which one endosome contains the molecule, while the other contains the receptor.
- The molecule-containing endosome then combines with a lysosome, which is essentially a membrane-bound cell organelle that stores digestive enzymes. The main job of the lysosome (also referred as the stomach of the cell) is to promote breakdown of the molecule, which can either be a protein or fat. The lysosome can also ingest pathogens including bacteria and viruses, in turn helping to clear cellular debris.
- The lysosome is essentially involved in digesting the material present in the endosome. The receptor in the other endosome is then recycled and sent back to the cell surface.