Current methods used to investigate G protein coupled receptor oligomerisation

Classical models of G protein coupled receptor (GPCR) signalling assume that each receptor functions as a single unit. However, evidence is increasing that GPCRs may form functional assemblies of dimeric or oligomeric units. There are several methods that can be used to give evidence of GPCR oligomerisation that will be discussed in this review. These include co-immunoprecipitation and Western blotting, resonance energy transfer methods and transactivation / complementation of partially functional receptors. One definitive method currently does not exist and there are various advantages and disadvantages to each method depending upon the system considered. Although co-immunoprecipitation and Western blot studies require disruption of the cellular environment and require specific antibodies, they are a good starting point to show that receptor oligomerisation occurs in native systems. Resonance energy transfer techniques provide evidence that receptors are in close proximity, are measured in living cells and some formats may be used for imaging applications. Transactivation / complementation requires extensive modification of the GPCR, but provides evidence that the receptors are in physical contact. Despite great advances being made using these techniques, future challenges involve the development of other methodologies to determine the role of receptor complexes in the pharmacology and physiology of native systems.