Assembly of an A kinase-anchoring protein–β2-adrenergic receptor complex facilitates receptor phosphorylation and signaling

Phosphorylation of G-protein-coupled receptors by second-messenger-stimulated kinases is central to the process of receptor desensitization [1–3]. Phosphorylation of the β2-adrenergic receptor (β2-AR) by protein kinase A (PKA), in addition to uncoupling adenylate cyclase activation, is obligatory for receptormediated activation of mitogen-activated protein kinase (MAP kinase) cascades [4,5]. Although mechanisms for linking G-protein-coupled receptor kinases to the activated receptor are well established, analogous mechanisms for targeting second messenger kinases to the β2-AR at the plasma membrane have not been elucidated. Here we show that the A-kinase-anchoring protein, AKAP79/150, co-precipitates with the β2-AR in cell and tissue extracts, nucleating a signaling complex that includes PKA, protein kinase C (PKC) and protein phosphatase PP2B. The anchoring protein directly and constitutively interacts with the β2-AR and promotes receptor phosphorylation following agonist stimulation. Functional studies show that PKA anchoring is required to enhance β2-AR phosphorylation and to facilitate downstream activation of the MAP kinase pathway. This defines a role for AKAP79/150 in the recruitment of second-messenger-regulated signaling enzymes to a G-protein-coupled receptor.