Heterologous inhibition of G protein-coupled receptor endocytosis mediated by receptor-specific trafficking of beta-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 beta2-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 beta2 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 beta-arrestins. First, previous studies showed that the activation of V2 but not beta2 receptors caused pronounced recruitment of beta-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 (beta-arrestin 1 or 2) abolished the V2 receptor-mediated inhibition of beta2 receptor internalization. Third, mutations of the V2 receptor that block endomembrane recruitment of beta-arrestins eliminated the V2 receptor-dependent blockade of beta2 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 beta-arrestins, and suggest an experimental method to rapidly modulate the functional activity of beta-arrestins in intact cells.