Study of g protein-coupled receptor (gpcr) homo- and heteroreceptor complexes interactions in the central nervous system through proximity labelling techniques

Abstract

There exists substantial evidence for the existence of GPCR homo and heteroreceptor complexes with allosteric receptor-receptor interactions in the Central Nervous System (CNS). Through the receptor heteromerization the allosteric receptor-receptor interactions can develop and produce alterations in recognition including novel allosteric binding sites, pharmacology, signaling, and trafficking of the participating receptors (receptor protomers). However, there is also lack of knowledge on the stoichiometry of the participating receptor protomers in GPCR heteroeceptor complexes. Therefore, the overall aim of this thesis was to gain insight into molecular aspects of several adenosine A2AR and dopamine D2R heteroreceptor complexes and their allosteric receptor-receptor interaction in the Central Nervous System, with special emphasis on the role of the balance between their homo and heteroreceptor complexes. As a proof of concept, we optimized and used the situ Proximity Ligation Assays methods to study A2AR and D2R iso, homo and heteroreceptor complexes. Our findings from our in situ PLA analysis revealed the highest densities of A2AR-A1R isoreceptor complexes and A2AR-A2AR homoreceptor complexes in the pyramidal cell layers of CA1-CA3 and the polymorphic cell layer in the hilus of the dentate gyrus in the hippocampus. Based on these observations, we propose that the regulation of adenosine A2AR signaling in the hippocampus relies on a balance between A2AR-A2AR homoreceptor complexes and A1R-A2AR isoreceptor complexes. Dysregulation of adenosine signaling within these complexes, particularly in the CA3-CA1 regions, may contribute to pathological outcomes such as psychosis or depression by modulating the interactions of the GABA-glutamate network.