IRIC - Institute for Research in Immunology and Cancer

Published on October 16, 2024

A new study by the laboratory of Michel Bouvier, Director of IRIC’s Molecular Pharmacology Research Unit, compares the advantages and disadvantages of various biosensors used to analyze G protein-coupled receptor signaling. The research project was conducted jointly by postdoctoral fellow Shane Wright, research advisor Charlotte Avet and postdoctoral fellow Supriya Gaitonde. It is published in the journal Science Signaling.

Analyze conformation or activation?

G protein-coupled receptors (GPCRs) are cell-surface proteins that act as transmission towers, receiving signals from the outside and converting them into intracellular signals. In humans, hundreds of GPCRs regulate numerous biological processes such as metabolism, inflammation and vision. Given their multiple implications, GPCRs are key therapeutic targets: almost a third of drugs on the market target them.

GPCRs transmit their signals by recruiting G proteins, each made up of three subunits, which in turn relay the information. To identify which G proteins are recruited by a given GPCR, biosensors using bioluminescence resonance energy transfer (BRET) technology are commonly used in the laboratory. Some of these BRET biosensors measure a conformational change (i.e. the three-dimensional arrangement) caused by an extracellular signal between the GPCR and the associated G protein subunits. Others measure the signal transmission activity of G proteins. Michel Bouvier’s team set out to compare these two types of biosensor, analyzing the advantages and disadvantages of each.

A biosensor for every experiment

Using cell culture assays, the team compared the ability of biosensors to detect the coupling of different GPCRs to specific G proteins. Their observations revealed certain differences in the signaling profiles detected by the two types of biosensor. The researchers found that these differences in profiles could be caused by several aspects of experimental design.

First, the type of biosensor employed impacts, through their difference in sensitivity, the ability to (i) detect couplings, (ii) measure activity in specific cellular compartments and (iii) precisely study the quantities of proteins involved. Furthermore, modification of GPCRs or G proteins (for conformational biosensors) by the addition of tags can affect coupling selectivity and stoichiometry, i.e. the proportion of each protein involved. Finally, the nature of the G protein subunits used in the assays can influence GPCR selectivity.

The results from the Bouvier laboratory underline the importance of the choice of biosensor according to the context, as well as the impact of this choice on the interpretation of the data generated. This work has the potential to improve the design of assays using BRET technology, enabling the most physiologically relevant conclusions to be drawn.

Cited study

Wright SC, Avet C, Gaitonde SA, Muneta-Arrate I, Le Gouill C, Hogue M, Breton B, Koutsilieri S, Diez-Alarcia R, Héroux M, Lauschke CV, Bouvier M. Conformation- and activation-based BRET sensors differentially report on GPCR–G protein coupling. Science Signaling. 17, eadi4747 (2024). DOI: 10.1126/scisignal.adi4747