The search for a functional thrombin receptor, using expression cloning methods, led to the discovery of a G protein-coupled receptor that mediates the actions of thrombin on platelets and endothelial cells.
The amount of cholesterol that is synthesized in the liver is tightly regulated by dietary cholesterol levels. LDL receptors regulate the cellular transport of lipid rich low density lipoprotein (LDL) particles.
Adenylyl cyclases occur throughout the animal kingdom and play diverse roles in cell regulation. In bacteria, the enzyme may be regulated in response to nutrients or it may constitute a toxic factor in mammals, as with adenylyl cyclases of B.