Novel Tools for G protein‐coupled receptor: GPCR Biosensors

Importance of Biosensors

Since GPCRs are among the most effective targets in drug development, contextualizing these interactions holds considerable promise for increasing the number of druggable GPCRs. This might result in the creation of innovative therapeutic approaches. GPCR activity has been assessed in cellular scenarios where enzymatic transduction cascades can be utilized to amplify and detect signals, such as the accumulation of second messengers or long-lasting changes in cellular activity. Conventional second-messenger and transcriptional reporter assays can yield a variety of functional readouts of GPCR activity. However, because of their layout and positioning in the intermediate or terminal phases of the transduction cascade, feedback loops, kinetic variables, and interactions with other cellular machinery can all lead to interference.

Biosensors are pharmacology tools. Because of their position in the signaling cascade, there is less doubt in the interpretation of results such as their linkage to a GPCR or the conformational changes associated with their activation.

Classification of GPCR Biosensors

• Binding extracellular ligand to GPCR

Binding to the extracellular ligand of the GPCR is the initial step in its activation. Increased ligand concentrations in the extracellular space cause GPCR activation, which is why fluorescent biosensors that detect extracellular GPCR ligands have been developed, with a response that can signal when GPCR activation begins. The extracellular GPCR ligands are detected by FRET-based biosensors, which consist of a ligand-binding protein and a FRET pair of FPs. Since they are visible outside of the plasma membrane, when they bind to ligands, they can alter the FRET signals. The glutamate-sensing fluorescent reporter, or GluSnFR, is made up of the platelet-derived growth factor receptor's TM domain-containing pDisplay vector and the glutamate periplasmic binding protein, GltI, sandwiched between cyan and yellow fluorescent probes.

Table 1. Product list of GluSnFR

• Conformational change of GPCR

GPCRs experience conformational changes upon ligand binding, which can stabilize the connection with heterotrimeric G proteins. Although they are unable to completely establish GPCR activation, biosensors that detect GPCR ligands can provide information about changes in the amounts of extracellular GPCR ligands. The two strategies that best illustrate this approach are dLight and GRAB-DA, which are designed to detect conformational changes in GPCRs between TM5 and TM6. These DRD biosensors were created by introducing cpGFP into the DRDs' ICL3 region. The conformational change of the DRD can boost the biosensor's inserted cpFP's fluorescence intensity.

Table 2. Product list of dLight and GRAB-DA

Biosensors in Creative Biolabs

Biosensors are innovative tools for studying membrane proteins. Fluorescence sensors hold great potential for researching biochemical processes inside the complex biological environment. Creative Biolabs can provide a range of biosensors, such as cAMP indicator, calcium indicator, dopamine indicator, and others. We provide stable cell lines, viruses, and plasmids for these biosensors. If you don't find the right product, please contact us for customization.

Table 3. Genetically Encoded Sensors List

Reference

1. Olsen, Reid HJ, and Justin G. English. "Advancements in G protein-coupled receptor biosensors to study GPCR-G protein coupling." British Journal of Pharmacology 180.11 (2023): 1433-1443.