Assay of G Protein-Coupled Receptor Kinase Activity by Rhodopsin Phosphorylation

Agonist occupation of G protein-coupled receptors (GPCRs) leads to a cellular response that wanes, or desensitizes, with prolonged agonist exposure. Different cellular mechanisms contribute to desensitization, including the altered function and/or expression of receptors, G proteins, and effecters. Phosphorylation plays a major role in the rapid (seconds to minutes) desensitization of responses generated by these receptors (1 ).