LDL Receptor Function and Life Cycle
LDL receptor complexes are present in clathrin-coated pits, regions of the plasma membrane that are transiently coated with the protein clathrin. These regions invaginate and pinch off to form intracellular clathrin-coated vesicles. When LDL cholesterol is bound to the LDL receptor, LDL cholesterol is internalised via endocytosis along with the LDL receptor. This process occurs mainly in the liver, which removes ~70% of LDL from the circulation.
Once the coated vesicle is internalised it will soon shed its clathrin coat and fuse with an acidic late endosome. The change in pH causes a conformational change in the receptor that releases the bound LDL particle. The LDL particle is then delivered to lysosomes, where LDL is degraded to release free cholesterol. The free cholesterol becomes available to the cell for new membrane synthesis. The LDL receptors can be recycled after transportation back to the plasma membrane via transport vesicles. When at the cell surface, the neutral pH will cause the receptor to revert to its native conformation; ready to receive another LDL particle.
This cartoon animation is part of a new slide lecture serie, currently in development