Oligomerization of opioid receptors: generation of novel signaling units

G-protein-coupled receptors such as opioid receptors exist in oligomeric complexes. Homo-oligomerization of mu, delta, and kappa opioid receptors has been demonstrated, suggesting a critical functional role for receptor-receptor interactions. Hetero-oligomerization creates delta-kappa and mu-delta receptor complexes, which display novel pharmacology, coupling to effector systems and signaling regulation properties. Exciting new opportunities are arising from the recent characterization of these oligomeric receptors, with the potential to revolutionize opioid research and therapeutic targeting.