Homo-oligomerization of the human adenosine A(2A) receptor is driven by the intrinsically disordered C-terminus

G protein-coupled receptors (GPCRs) have long been shown to exist as oligomers with functional properties distinct from those of the monomeric counterparts, but the driving factors of oligomerization remain relatively unexplored. Herein, we focus on the human adenosine A(2A) receptor (A(2A)R), a model GPCR that forms oligomers both in vitro and in vivo. Combining experimental and computational approaches, we discover that the intrinsically disordered C-terminus of A(2A)R drives receptor homo-oligomerization. The formation of A(2A)R oligomers declines progressively with the shortening of the C-terminus. Multiple interaction types are responsible for A(2A)R oligomerization, including disulfide linkages, hydrogen bonds, electrostatic interactions, and hydrophobic interactions. These interactions are enhanced by depletion interactions, giving rise to a tunable network of bonds that allow A(2A)R oligomers to adopt multiple interfaces. This study uncovers the disordered C-terminus as a prominent driving factor for the oligomerization of a GPCR, offering important insight into the effect of C-terminus modification on receptor oligomerization of A(2A)R and other GPCRs reconstituted in vitro for biophysical studies.