GRK4

G protein-coupled receptor kinase 4 (GRK4) is an enzyme that in humans is encoded by the "GRK4" gene.
This gene encodes a member of the G protein-coupled receptor kinase subfamily of the Ser/Thr protein kinase family, and is most highly similar to GRK5 and GRK6.
G protein-coupled receptor kinases phosphorylate activated G protein-coupled receptors, which promotes the binding of an arrestin protein to the receptor. Arrestin binding to phosphorylated, active receptor prevents receptor stimulation of heterotrimeric G protein transducer proteins, blocking their cellular signaling and resulting in receptor desensitization. Arrestin binding to phosphorylated, active receptor also enables receptor signaling through arrestin partner proteins. Thus the GRK/arrestin system serves as a signaling switch for G protein-coupled receptors.
GRK4 is most highly expressed in the testes, with low amounts in brain and kidney and other tissues, and has four alternatively-spliced variants.
Polymorphisms in the GRK4 gene have been linked to both genetic and acquired hypertension, acting in part through kidney dopamine receptors.