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 nucleoti de binding-protein-coupled receptors and thereby trigger uncoupling be tween receptors and guanine nucleotide binding proteins. Herein we sho w that this kinase is subject to phosphorylation and regulation by pro tein kinase C (PKC). In cell lines stably expressing alpha(1 beta)-adr energic receptors, activation of these receptors by epinephrine result ed in an activation of cytosolic beta ARK. Similar data were obtained in 293 cells transiently coexpressing alpha(1 beta)-adrenergic recepto rs and beta ARK-1. Direct activation of PKC with phorbol esters in the se cells caused not only an activation of cytosolic beta ARK-1 but als o a translocation of beta ARK immunoreactivity from the cytosol to the membrane fraction. A PKC preparation purified from rat brain phosphor ylated purified recombinant beta ARK-1 to a stoichiometry of 0.86 phos phate per beta ARK-1. This phosphorylation resulted in an Increased ac tivity of beta ARK-1 when membrane-bound rhodopsin served as its subst rate but in no increase of its activity toward a soluble peptide subst rate. The site of phosphorylation was mapped to the C terminus of beta ARK-1. We conclude that PKC activates PARK by enhancing its transloca tion to the plasma membrane.