First, arrestin binding to the cytoplasmic face of the receptor occludes the binding site for heterotrimeric G-protein, preventing its activation (desensitization). Second, arrestin links the receptor to elements of the internalization machinery, clathrin and clathrin adaptor AP2, which promotes receptor internalization via coated pits and subsequent transport to internal compartments, called endosomes.
The binding of arrestin to the cytoplasmic face of the receptor initially prevents the activation of heterotrimeric G-protein, a process known as desensitization. Subsequently, arrestin facilitates the connection between the receptor and internalization machinery, including clathrin and AP2 adaptor, which leads to the receptor's internalization through coated pits and transport to endosomal compartments.