G-protein coupled receptors (GPCRs) play a central role in a range of physiological
and pathophysiological processes, making them key drug targets. D2 dopamine
receptors (D2R) are class A GPCRs which are expressed primarily in the central
nervous system (CNS) and are known to have fundamental role in reward
reinforcement mechanisms and the regulation of locomotion. D2Rs can form
homomers and heteromers with other GPCRs, which can influence the function of
receptors and diversify receptor signalling. D2R di/oligomeric complexes may also be
important therapeutic targets and have been implicated in several neurological
diseases, including schizophrenia and Parkinson’s disease. This thesis aimed to
stabilise D2R dimers for subsequent high-resolution structural analysis. Molecular
models of D2R dimers facilitated the identification of mutations to be identified which
had the potential to stabilise the dimer complex. Assessing the impact of these
mutations on dimer stability in cell lines using biophysical, biochemical and single
molecule super-resolution cell surface imaging, revealed that some mutations
increased dimer stability, with the largest effect seen with the V96S/V97C double
mutation. Interestingly, the mutants which exhibited increased di/oligomerisation also
showed a bias towards β-arrestin-2 associated pathways, including increased β-
arrestin-2 recruitment, internalisation and reprogrammed extracellular-signalregulated
kinase (ERK) signalling. Progress towards optimising expression and
purification protocols of D2R V96S/V97C for structural analysis was also made in this
thesis. Most significantly, this thesis suggests a novel link between D2R dimerisation
and β-arrestin-2 biased signalling. This could be fundamental for understanding D2R
di/oligomerisation and impacts how these complexes may be exploited therapeutically.