Protein kinase cross-talk: Membrane targeting of the beta-adrenergic receptor kinase by protein kinase C

The beta-adrenergic receptor kinase (PARK) is the prototypical member of the family of cytosolic kinases that phosphorylate guanine nucleotide binding-protein-coupled receptors and thereby trigger uncoupling between receptors and guanine nucleotide binding proteins. Herein we show that this kinase is subject to phosphorylation and regulation by protein kinase C (PKC). In cell lines stably expressing alpha(1 beta)-adrenergic receptors, activation of these receptors by epinephrine resulted in an activation of cytosolic beta ARK. Similar data were obtained in 293 cells transiently coexpressing alpha(1 beta)-adrenergic receptors and beta ARK-1. Direct activation of PKC with phorbol esters in these cells caused not only an activation of cytosolic beta ARK-1 but also a translocation of beta ARK immunoreactivity from the cytosol to the membrane fraction. A PKC preparation purified from rat brain phosphorylated purified recombinant beta ARK-1 to a stoichiometry of 0.86 phosphate per beta ARK-1. This phosphorylation resulted in an Increased activity of beta ARK-1 when membrane-bound rhodopsin served as its substrate but in no increase of its activity toward a soluble peptide substrate. The site of phosphorylation was mapped to the C terminus of beta ARK-1. We conclude that PKC activates PARK by enhancing its translocation to the plasma membrane.