Are fluorescent ligands the best tool to characterise GPCRs ?

G protein-coupled receptors (GPCRs) represent the largest protein family encoded by the human genome. Located on the cell membrane, they transduce extracellular signals into key physiological effects.[1]
Considering this feature, they have become highly studied drug targets.

Some GPCRs have known radioligands available. However, in most cases, they are orphan receptors, which means that no ligands are known, or there are only primary antibodies available for their study.

Primary Abs can be used to detect the GPCRs expression through a wide range of techniques, including immunohistochemistry, proximity ligation assays and immunoblotting.

However, The widely used primary antibody detection method shows some limits and disadvantages:

  1. Not all GPCRs have specific subtype-selective antibodies
  2. Lack of batch-to-batch consistency: leads to poor experimental reproducibility
  3. Low specificity: due to their big size, they can bind only to GPCRs exposed regions

Another method radioligands also has its disadvantages. In addition to the lack of available radioligands on the market, it also shows safety and supply concerns and they are quite expensive compare to others.

So, how can you overcome these hurdles ?

Is there a versatile tool for GPCR pharmacological studies? Yes, there is!

Make the move to fluorescent ligands, the new method to label your GPCRs.

Fluorescent ligands have clear advantages over radioactivity and antibodies methods:

In comparison to the radioligands method:

In comparison to the antibody method:

  1. Visualise receptor localisation in-vitro/ ex-vivo
  2. Possibility to perform HTS assays
  3. Perform ligand binding assays via microscopy or via FRET/BRET donor
  4. Use to study receptor internalisation
fluorescent ligqnds

Besides, one of the biggest advantages of using FL is the possibility to combine different techniques in the same experiment. An example is the combination of FRET and flow cytometry. Read this other post on our blog “Fluorescent ligands, a new method to label your GPCRs to see how they perform with more detailed examples.

How to find reliable fluorescent ligand products ?

Tebubio brings you access to a source of new fluorescent ligands solutions by Celtarys, who have acquired more than 20 years of experience in GPCRs, and who have developed fluorescent ligands for different GPCR families, filling the gaps in the available tools ready to use in HTS and other applications.


  1. Yang, D., Zhou, Q., Labroska, V. et al. G protein-coupled receptors: structure- and function-based drug discovery. Sig Transduct Target Ther 6, 7 (2021).
Written by Xiyu Qian
Xiyu Qian is a Marketing Specialist at tebu-bio, also actively involved in our Digital communication tools and website.