The Third Intracellular Loop of α2-Adrenergic Receptors Determines Subtype Specificity of Arrestin Interaction

摘要: Nonvisual arrestins (arrestin-2 and -3) serve as adaptors to link agonist-activated G protein-coupled receptors the endocytic machinery. Although many bind arrestins, molecular determinants involved in binding remain largely unknown. Because selectively promote internalization of α2b- α2c-adrenergic (ARs) while having no effect on α2aAR, here we used α2ARs identify arrestin binding. Initially, assessed ability purified glutathioneS-transferase fusions containing third intracellular loops α2bAR, or α2cAR. These studies revealed that arrestin-3 directly binds α2bAR α2cAR but not whereas arrestin-2 only α2bAR. Truncation mutagenesis identified two domains loop, one at N-terminal end (residues 194–214) other C-terminal 344–368). Site-directed further a critical role for several basic residues loop. Mutation these holo-α2bAR subsequent expression HEK 293 cells mutations had receptor activate ERK1/2. However, agonist-promoted mutant was significantly attenuated compared with wild type receptor. results demonstrate discrete regions within loop disruption abrogates internalization.