Dimerization of β₂-adrenergic receptor is responsible for the constitutive activity subjected to inverse agonism

Dimerization of beta 2-adrenergic receptor (β₂-AR) has been observed across various physiologies. However, the function of dimeric β₂-AR is still elusive. Here, we revealed that dimerization of β₂-AR is responsible for the constitutive activity of β₂-AR generating inverse agonism. Using a co-immunoimmobilization assay, we found that transient β₂-AR dimers exist in a resting state, and the dimer was disrupted by the inverse agonists. A Gα_s preferentially interacts with dimeric β₂-AR, but not monomeric β₂-AR, in a resting state, resulting in the production of a resting cAMP level. The formation of β₂-AR dimers requires cholesterol on the plasma membrane. The cholesterol did not interfere with the agonist-induced activation of monomeric β₂-AR, unlike the inverse agonists, implying that the cholesterol is a specific factor regulating the dimerization of β₂-AR. Our model not only shows the function of dimeric β₂-AR but also provides a molecular insight into the mechanism of the inverse agonism of β₂-AR.