Affiliation: | a Howard Hughes Medical Institute, Duke University Medical Center, Box 3821, Durham, NC 27710, USA b Department of Medicine, Duke University Medical Center, Durham, NC 27710, USA c Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA |
Abstract: | Recently, it has been shown that PKA-mediated phosphorylation of the β2-adrenergic receptor (β2-AR) by the cyclic AMP-dependent protein kinase (PKA) reduces its affinity for Gs and increases its affinity for Gi. Here we demonstrate that, like the β2-AR, the β1-AR is also capable of “switching” its coupling from Gs to Gi in a PKA-dependent manner. The β1-AR is capable of activating adenylate cyclase via Gs, and can also activate the extracellular-regulated kinases, p44 and p42 (ERK1/2). In transfected CHO cells, the observed β1-AR-mediated activation of ERK is both sensitive to pertussis toxin (PTX), indicating involvement of Gi/Go, and to the PKA inhibitor, H-89. β1-ARs with PKA phosphorylation sites mutated to alanines are unable to activate ERK. Mutating these same residues to aspartic acid, mimicking PKA phosphorylation, leads to a decrease in Gs-stimulated cAMP accumulation and an increase in PTX-sensitive ERK activation. These results strongly support the hypothesis that the β1-AR, like the β2-AR, can undergo PKA-dependent “Gs/Gi switching”. |