Are we beta-ARKing up the wrong tree? Casein kinase 1 alpha provides an additional pathway for GPCR phosphorylation.

Although originally linked to receptor desensitization, G-protein-coupled receptor (GPCR) phosphorylation has now been implicated in coupling receptors to specific signalling pathways. Generally, this phosphorylation event is thought to be mediated by one of the members of the GPCR kinase (GRK) family. However, recent studies have indicated that protein kinases distinct from the GRK family might also be involved in agonist-mediated GPCR phosphorylation. This review analyses the approaches employed to investigate the nature of GPCR phosphorylation and discusses recent developments implicating other kinases, particularly casein kinase 1 alpha, in the phosphorylation of GPCRs.