beta-Arrestins are proteins that bind phosphorylated heterotrimeric GTP-binding protein (G protein)-coupled receptors (GPCRs) and contribute to the desensitization of GPCRs by uncoupling the signal transduction process. Resensitization of GPCR responsiveness involves agonist-mediated receptor sequestration. Overexpression of beta-arrestins in human embryonic kidney cells rescued the sequestration of beta(2)-adrenergic receptor (beta(2)AR) mutants defective in their ability to sequester, an effect enhanced by simultaneous overexpression of beta-adrenergic receptor kinase 1, Wild-type beta(2)AR sequestration was inhibited by the overexpression of two beta-arrestin mutants. These findings suggest that beta-arrestins play an integral role in GPCR internalization and thus serve a dual role in the regulation of GPCR function.