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 side of the receptor initially blocks G-protein activation (desensitization). Second, it links the receptor to machinery that promotes its internalization, including clathrin and AP2 adaptor, which facilitates this process through coated pits and transport to endosomal compartments.