Heterologous Inhibition of G Protein-coupled Receptor Endocytosis Mediated by Receptor-specific Trafficking of β-Arrestins *

We have observed an unexpected type of nonreciprocal “cross-regulation” of the agonist-induced endocytosis of G protein-coupled receptors by clathrin-coated pits. Isoproterenol-dependent internalization of β 2 -adrenergic receptors in stably transfected HEK293 cells was specifically blocked (>65% inhibition) by vasopressin-induced activation of V2 vasopressin receptors co-expressed at similar levels. In contrast, activation of β 2 receptors caused no detectable effect on V2 receptor internalization in the same cells. Several pieces of evidence suggest that this nonreciprocal inhibition of endocytosis is mediated by receptor-specific intracellular trafficking of β-arrestins. First, previous studies showed that the activation of V2 but not β 2 receptors caused pronounced recruitment of β-arrestins to endocytic membranes (Oakley, R. H., Laporte, S. A., Holt, J. A., Barak, L. S., and Caron, M. G. (1999) J. Biol. Chem. 274, 32248–32257). Second, overexpression of arrestin 2 or 3 (β-arrestin 1 or 2) abolished the V2 receptor-mediated inhibition of β 2 receptor internalization. Third, mutations of the V2 receptor that block endomembrane recruitment of β-arrestins eliminated the V2 receptor-dependent blockade of β 2 receptor internalization. These results identify a novel type of heterologous regulation of G protein-coupled receptors, define a new functional role of receptor-specific intracellular trafficking of β-arrestins, and suggest an experimental method to rapidly modulate the functional activity of β-arrestins in intact cells.