Functional alpha 2-adrenergic receptor-Gs coupling undergoes agonist-promoted desensitization in a subtype-selective...

Recently it has become clear that alpha 2-adrenergic receptors (alpha 2AR) functionally couple to Gs as well as Gi, thus inducing a complex modulation of adenylyl cyclase activity. It is unknown whether alpha 2AR-Gs coupling undergoes agonist-promoted desensitization. Therefore, in CHO cells expressing the three cloned human alpha 2AR subtypes (alpha 2C10, alpha 2C4, and alpha 2C2), we assessed the ability of alpha 2AR-mediated stimulation of adenylyl cyclase activity to undergo short-term agonist-promoted desensitization. To isolate alpha 2AR-Gs coupling, cells were pretreated with pertussis toxin, which ablates Gi coupling. Following agonist exposure, both alpha 2C10- and alpha 2C2-mediated stimulation of adenylyl cyclase activity underwent marked desensitization. In distinct contrast, alpha 2C4-mediated stimulation of adenylyl cyclase activity underwent no agonist-promoted desensitization. Thus, alpha 2AR-Gs coupling undergoes agonist-promoted desensitization and does so in a subtype-selective manner.