Heterodimerization of α2A- and β1-adrenergic receptors

Abstract

β- and α2-adrenergic receptors are known to exhibit substantial cross-talk and mutual regulation in tissues where they are expressed together. We have found that the β1-adrenergic receptor (β1AR) and α2A-adrenergic receptor (α2AAR) heterodimerize when coexpressed in cells. Immunoprecipitation studies with differentially tagged β1AR and α2AAR expressed in HEK-293 cells revealed robust co-immunoprecipitation of the two receptors. Moreover, agonist stimulation of α2AAR was found to induce substantial internalization of coexpressed β1AR, providing further evidence for a physical association between the two receptors in a cellular environment. Ligand binding assays examining displacement of [3H]dihydroalprenolol binding to the β1AR by various ligands revealed that β1AR pharmacological properties were significantly altered when the receptor was coexpressed with α2AAR. Finally, β1AR/α2A heterodimerization was found to be markedly enhanced by β1AR point mutation (N15A) that blocks N-linked glycosylation of the β1AR as well as by point mutations (N10A/ N14A) that block N-linked glycosylation of the α2AAR. These data reveal an interaction between β1AR and a2AAR that is regulated by glycosylation and that may play a key role in cross-talk and mutual regulation between these receptors.