Figure 2.

Transubiquitination between GPCRs: Activation of one GPCR can promote ubiquitination of another GPCR. (1) Agonist stimulation of dopamine D₅ receptor (D₅R) leads to the ubiquitination of angiotensin-II type 1 receptor (AT₁R), disruption of the interaction between the two receptors, and subsequent proteasomal degradation of AT₁R. The precise mechanism is poorly understood; (2) Activation of δ-opioid receptor (DOR) with its specific agonist leads to the ubiquitination of μ-opioid receptor (MOR) and co-internalization of both receptors which are in the next steps targeted for lysosomal degradation. This causes a decrease in cell responsiveness to opiate agonists.