GPCR Oligomerisation Modulation by Conformational State and Lipid Interactions Revealed by MD Simulations and Markov Models

G protein coupled receptors (GPCRs) play key roles in cellular signalling pathways. GPCRs are suggested to form dimers and higher order oligomers in response to activation and other stimuli. However, a lack of structural details of the involvement of GPCR oligomerisation in receptor activation has held back our understanding of GPCR signalling in an in vivo context. Here, we combined extensive molecular dynamics simulations with Markov state modelling in order to understand the oligomerisation process of the Adenosine A2a receptor in response to receptor activation. The Markov state models reveal that activation leads to an increased propensity for oligomerisation, accompanied by a more interconnected oligomerisation network, when compared to the receptor in the inactive state. Coupling of the active state to a mini Gs protein shifted the oligomerisation pattern. Oligomerisation is also sensitive to changes in local membrane environment, such as the packing density of GPCRs in a membrane patch, which enhanced oligomerisation, and removal of PIP2 from the lipid bilayer membrane which disfavoured oligomerisation. These results support combinatory allosteric modulation of GPCR oligomerisation whereby the receptor may generate a specific oligomerisation profile in response to its local environment in order to favour the formation of a specific supra-molecular signalling complex.