Understanding spatial and temporal control of GPCR signalling using high resolution imaging
Monash Institute of Pharmaceutical Sciences, Monash University, 399 Royal Parade, Parkville, VIC 3052, Australia.
Cells endogenously express many different receptors that can activate the same second messenger, but with remarkably diverse physiological outcomes. This suggests a high degree of organisation and regulation of intracellular signalling, which is achieved by the spatiotemporal compartmentalisation of signals – the restriction of second messengers in space and time. The development of targeted Forster Resonance Energy Transfer (FRET)-based biosensors has increased the resolution at which we can measure the spatial and temporal signalling of GPCRs. Moreover, single molecule imaging techniques such as Total Internal Reflection Fluorescence (TIRF) and Fluorescence Correlation Spectroscopy (FCS) now allow us to correlate subtle changes in receptor organisation at the plasma membrane with large changes in spatiotemporal signalling. The complementary use of single cell and molecule imaging has revealed that GPCRs can activate very defined signals in limited sub-cellular compartments by assembling focused protein complexes. These complexes facilitate second messenger production, the organisation and scaffolding of effectors, and co-ordination of regulatory elements.