Hetero-oligomerization and specificity changes of G protein-coupled purinergic receptors: novel insight into diversification of signal transduction.

The formation of homo- and hetero-oligomers between various G protein-coupled receptors (GPCRs) has been demonstrated over the past decade. In most cases, GPCR heterodimerization increases the diversity of intracellular signaling. GPCR-type purinergic receptors (adenosine and P2Y receptors) are actively reported to form hetero-oligomers with each other, with GPCRs belonging to the same group (type 1, rhodopsin-like), and even with GPCRs from another group. This chapter describes common strategies to identify dimerization of purinergic receptors (coimmunoprecipitation, bioluminescence resonance energy transfer (BRET), and immunoelectron microscopy) and to assess the alteration of their pharmacology (ligand binding, intracellular cAMP, and intracellular Ca(2+) assays). We have reported dimerization of purinergic receptors using these strategies in transfected human embryonic kidney 293T cells and native brain tissue. Our data suggest that homo- and hetero-oligomerization between purinergic receptors exert unique pharmacology in this receptor group. According to these discoveries, heterodimerization is likely to be employed for the "fine-tuning" of purinergic receptor signaling.