Endocrine Abstracts (2011) 26 S7.1

How to visualize G-protein-coupled receptor signaling by FRET

D Calebiro1,2

1Bioimaging Center/Rudolf Virchow Center, Wuerzburg, Germany; 2Institute of Pharmacology and Toxicology, University of Würzburg, Wuerzburg, Germany.

G-protein-coupled receptors (GPCRs) constitute the major family of cell surface receptors. They comprise receptors for light, taste and smell as well as ions, small transmitters, peptides and large protein hormones. Given their involvement in fundamental biological processes and their accessibility, GPCRs serve as targets for many classes of drugs, including beta-blockers, antihistamines and opiates.

Whereas many biochemical steps involved in GPCR signaling have been described in good details, their spatio-temporal dynamics in living cells is still largely unknown. This is because biochemical techniques have limited temporal and, generally, no spatial resolution.

The recent introduction of a series genetically encoded fluorescent sensors allows for the first time to monitor key steps of GPCR signaling, such as ligand binding, receptor activation, G-protein coupling and second messenger generation, directly in living cells1. These sensors are largely based on the physical phenomenon of fluorescence resonance energy transfer (FRET), which can be measured by different microscopy techniques. Since the temporal and spatial resolution are those of fluorescence microscopy, i.e. up to a few milliseconds in time and a few hundred nanometers in space, these techniques can capture fast signaling events and, at the same time, define their subcellular location. These methods have been instrumental for new and important advances in the field, including the recent finding that GPCRs can continue to signal to cAMP after agonist-dependent internalization into endosomes2–4.


1. Lohse MJ et al. Trends Pharmacol Sci 2008 29 159–165.

2. Calebiro et al. PLoS Biol 2009 7 e1000172.

3. Ferrandon et al. Nat Chem Biol 2009 5 734–742.

4. Mullershausen et al. Nat Chem Biol 2009 5 428–434.

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