Design and synthesis of novel fluorescent ligands for the Beta-3 adrenoceptor

The Beta-3 adrenoceptor (B3AR) is an attractive therapeutic target for obesity, overactive bladder (OAB) and type-2 diabetes and belongs to the G protein-coupled receptor (GPCR) superfamily. GPCRs are complex and flexible membrane-bound proteins comprising ~800 family members. The B3AR is activated by endogenous catecholamines, such as epinephrine/norephinephrine and mediates critical homeostatic processes such as lipolysis and thermogenesis. Though the B3AR was identified >40 years ago, there is much to be learnt about its pharmacology and to-date only a handful of therapeutics for OAB have been clinically approved. In particular, most desired B3AR drugs are agonists (activating the receptors), and the real time binding behaviour of these ligands is a key component of how well they stimulate target cell types such as adipocytes and smooth muscle to provide an anti-obesity or bladder relaxation effect.
Recently, the structure of the canine B3AR bound to the OAB drug mirabegron has been published (Nagiri et al, 2021, PDB: 7DH5). Whilst the human and canine protein sequences share ~83% overall similarity, their differences may confer significant variation in their three-dimensional shape and ligand interaction. Therefore, there is a need to develop a reliable human B3AR model to inform the design of new B3AR-selective ligands.
The modelling work will allow the design and synthesis of a library of fluorescent ligands which will undergo pharmacological characterisation. Furthermore, effective fluorescent ligands will allow powerful fluorescence-based B3AR assays to be established, mapping more detailed analysis of ligand-binding kinetics to the desired functional responses.
Specific aims of the project will be:
1. To generate optimised computational models of the human B3AR and use these to design, synthesise and characterise a library of novel fluorescent ligands.
2. To pharmacologically characterise the new fluorescent ligands at all beta-adrenoceptor subtypes
3. To use the computational model of the human receptor to conduct a virtual screen for leads to develop novel, selective ligand scaffolds for the B3AR.
4. To apply the new multidisciplinary knowledge (structures, chemistry, pharmacology) to the development of selected leads into potent and subtype-selective ligands for the B3AR.
This chemical biology-focused project will span the disciplines of synthetic chemistry, modelling and pharmacology to increase our understanding of B3AR biology. The importance of the adrenoceptor family as prototypical GPCRs and key therapeutic targets means this project will be of direct relevance to future drug discovery efforts.