Functional coupling of Gi subtype with GABAB receptor/adenylyl cyclase system: analysis using a reconstituted system with purified GTP-binding protein from bovine cerebral cortex.

Abstract A single molecular species of GTP-binding protein (G protein) has been purified from the bovine cerebral cortex. The immunoblot analysis indicated that the isolated G protein might be Gi 1 or Gi 2 but not Go, since it was reacted by specific antibodies, anti-Giα 1–2 and anti-Giα 1ν3 , but not anti-Goα. When the Gi protein was reconstituted into phospholipid vesicles with partially purified GABA B receptor and adenylyl cyclase, the stimulation of GABA B receptor by its agonists induced the inhibition of forskolin-stimulated cAMP accumulation. This GABA-induced inhibition was abolished by CGP 55845A, an antagonist of GABA B receptor. These results suggest that a Gi subtype, which was suggested to correspond to Gi 1 or Gi 2 may be functionally coupled with GABA B receptor/adenylyl cyclase system. © 1997 Elsevier Science Ltd