Exposure of C6 glioma cells to 1 μM isoproterenol leads to fast desensitization of the β-adrenergic receptor/adenylyl cyclase system and transient receptor sequestration. It also triggers a very rapid and transient translocation to the plasma membrane or β-adrenergic receptor kinase (βARK), a specific cytoplasmic kinase that phosphorylates only the agonist-occupied form of several G protein-coupled receptors. βARK-mediated receptor phosphorylation appears to be a suitable mechanism for the rapid regulation or adrenergic receptor function in the nervous tissue.
