Phosphorylation of phospholipase C-coupled receptors

Early work on G-protein-coupled receptor (GPCR) phosphorylation focused on the adenylyl cyclase-linked beta-adrenoceptor, where phosphorylation at sites on the C-terminal tail and within the third intracellular loop results in receptor desensitisation. In recent years, intense research activity has revealed that a large number of GPCR subtypes exist as phosphoproteins, where the level of phosphorylation is dramatically increased subsequent to receptor stimulation. Among these receptor subtypes are those receptors coupled to phospholipase C (PLC). It appears, therefore, that regulation via receptor phosphorylation is a mechanism employed by all but a few GPCRs, including those coupled to PLC. Because the majority of GPCRs are coupled to the phosphoinositide signalling pathway, receptor phosphorylation of PLC-coupled receptors is a regulatory process with profound physiological significance for a huge array of biological responses. This review discusses the properties of homologous and heterologous phosphorylation of PLC-coupled receptors, together with the receptor kinases involved and the functional significance of receptor phosphorylation.