Development of Novel Neuroprotective Agents Targeting GPCR Using in Vitro Assays

This chapter aims to elucidate an example of the drug development process for a G protein-coupled receptor (GPCR), focusing specifically on the cannabinoid receptors CB₁ and CB₂. Various techniques can be employed for different purposes when characterizing a new compound targeting these receptors.Initially, the compound affinity for both cannabinoid receptors is assessed through binding competition assays. Subsequently, the compound's functionality on cannabinoid receptors at intracellular signaling levels is investigated. Cannabinoid receptors predominantly interact with G proteins, although other interactors such as β-arrestins, SGIP1, CRIP1a/b, BiP, and GAP43 have been identified. So, selective functionality or biased agonism, favoring one signaling pathway over another, has been a focus of recent research efforts. The ability of compounds to activate the α subunit of G-proteins is assessed through a [³⁵S]-GTPγS binding assays.With the above experimental tools, it is possible to investigate cannabinoids in relation to their interaction with cannabinoid receptors, which may be useful in understanding their pharmacological effects on numerous biological processes. Of high interest is the role of these receptors in the control of cell integrity and survival, which explains the study of cannabinoids and, in general, of the modulation of the endocannabinoid system (ECS) as a therapeutic strategy on neurodegenerative diseases due to its involvement in mitigating neuroinflammation, excitotoxicity, and oxidative stress. In vitro models employing cell lines and toxin mimics of neurodegenerative disease pathology are utilized to evaluate the compounds' potential therapeutic effects.In summary, the drug discovery process for GPCRs involves a comprehensive assessment of compound affinity, functionality, and physiological effects, ultimately aiming to identify novel therapeutic strategies for various human disorders.