Biochem/physiol Actions

Low-density lipoprotein (LDL) is a lipoprotein that carries cholesterol throughout the body via blood circulation. LDL has a role in dispositioning cholesterol to tissues and organs of the body. Colloquially deemed as the "bad cholesterol", having high levels of LDL can lead to plaque formation in arteries.LDL and HDL transport both dietary and endogenous cholesterol in the plasma. LDL is the main transporter of cholesterol and cholesteryl esters, and makes up more than half of the total lipoprotein in plasma. LDL is absorbed by the liver and other tissues via receptor mediated endocytosis. The cytoplasmic domain of the LDL receptor facilitates the formation of coated pits; receptor-rich regions of the membrane. The ligand binding domain of the receptor recognizes apo-B100 on LDL, resulting in the formation of a clathrin-coated vesicle. ATP-dependent proton pumps lower the pH inside the vesicle, resulting in dissociation of LDL from its receptor. After loss of the clathrin coat, the vesicles fuse with lysozomes, resulting in peptide and cholesteryl ester enzymatic hydrolysis. The LDL receptor can be recycled to the cell membrane. Insulin, tri-iodothyronine and dexamethasome have shown to be involved with the regulation of LDL receptor mediated uptake