Catecholamines signal through the beta2-adrenergic receptor by promoting production of the second messenger adenosine 3',5'-monophosphate (cAMP). The magnitude of this signal is restricted by desensitization of the receptors through their binding to beta-arrestins and by cAMP degradation by phosphodiesterase (PDE) enzymes. We show that beta-arrestins coordinate both processes by recruiting PDEs to activated beta2-adrenergic receptors in the plasma membrane of mammalian cells. In doing so, the beta-arrestins limit activation of membrane-associated cAMP-activated protein kinase by simultaneously slowing the rate of cAMP production through receptor desensitization and increasing the rate of its degradation at the membrane.

Phosphorylation of the ␤2 adrenoreceptor (␤2AR) by cAMP-activated protein kinase A (PKA) switches its predominant coupling from stimulatory guanine nucleotide regulatory protein (Gs) to inhibitory guanine nucleotide regulatory protein (G i). ␤-Arrestins recruit the cAMP-degrading PDE4 phosphodiesterases to the ␤2AR, thus controlling PKA activity at the membrane. Here we investigate a role for PDE4 recruitment in regulating G protein switching by the ␤2AR. In human embryonic kidney 293 cells overexpressing a recombinant ␤2AR, stimulation with isoprenaline recruits ␤-arrestins 1 and 2 as well as both PDE4D3 and PDE4D5 to the receptor and stimulates receptor phosphorylation by PKA. The PKA phosphorylation status of the ␤2AR is enhanced markedly when cells are treated with the selective PDE4-inhibitor rolipram or when they are transfected with a catalytically inactive PDE4D mutant (PDE4D5-D556A) that competitively inhibits isoprenaline-stimulated recruitment of native PDE4 to the ␤2AR. Rolipram and PDE4D5-D556A also enhance ␤2AR-mediated activation of extracellular signal-regulated kinases ERK1͞2. This is consistent with a switch in coupling of the receptor from G s to Gi, because the ERK1͞2 activation is sensitive to both inhibitors of PKA (H89) and G i (pertussis toxin). In cardiac myocytes, the ␤2AR also switches from G s to Gi coupling. Treating primary cardiac myocytes with isoprenaline induces recruitment of PDE4D3 and PDE4D5 to membranes and activates ERK1͞2. Rolipram robustly enhances this activation in a manner sensitive to both pertussis toxin and H89. Adenovirus-mediated expression of PDE4D5-D556A also potentiates ERK1͞2 activation. Thus, receptor-stimulated ␤-arrestinmediated recruitment of PDE4 plays a central role in the regulation of G protein switching by the ␤2AR in a physiological system, the cardiac myocyte.