PKA-mediated phosphorylation of the β1-adrenergic receptor promotes Gs/Gi switching

Abstract Recently, it has been shown that PKA-mediated phosphorylation of the β 2 -adrenergic receptor (β 2 -AR) by the cyclic AMP-dependent protein kinase (PKA) reduces its affinity for G s and increases its affinity for G i . Here we demonstrate that, like the β 2 -AR, the β 1 -AR is also capable of “switching” its coupling from G s to G i in a PKA-dependent manner. The β 1 -AR is capable of activating adenylate cyclase via G s , and can also activate the extracellular-regulated kinases, p44 and p42 (ERK1/2). In transfected CHO cells, the observed β 1 -AR-mediated activation of ERK is both sensitive to pertussis toxin (PTX), indicating involvement of G i /G o , and to the PKA inhibitor, H-89. β 1 -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 G s -stimulated cAMP accumulation and an increase in PTX-sensitive ERK activation. These results strongly support the hypothesis that the β 1 -AR, like the β 2 -AR, can undergo PKA-dependent “G s /G i switching”.