Organisation of G-protein-coupled receptor signalling complexes by scaffolding proteins.

Signalling by receptors coupled to heterotrimeric G proteins primarily involves intermediates (G-protein subunits and second messengers) that can reach their targets by diffusion either through the cytosol or within the plane of the membrane. However, in many cases additional proteins have been identified which, by providing a scaffold, link several components of a signal transduction pathway in order to control speed and specificity of signalling. Scaffolding proteins such as PSD-95 or shank/ProSAP proteins organise rather large signalling complexes. Recent proteomic approaches have now been used to study the molecular composition of receptor complexes in detail, for example glutamate receptors and 5HT(2C) receptors, providing a much more complicated picture of G-protein-coupled receptor signalling than previously anticipated.