Inhibitory coupling of hormone and neurotransmitter receptors to adenylate cyclase.

The last few years have provided evidence that beside the familiar and partially well characterized stimulation of the adenylate cyclase the enzyme is also subject to a hormone and neurotransmitter-induced inhibition serving as a general information-transfer system. Similar to hormonal stimulation, the coupling of the inhibitory hormone receptors to adenylate cyclase is mediated by a GTP-dependent process. In some membrane systems, the inhibitory coupling is additionally amplified by sodium ions. Inhibitory hormones stimulate a high affinity GTPase in plasma membranes. The observed correlation suggests that there is a close connection between the hormone-induced adenylate cyclase inhibition and GTPase stimulation. Several lines of evidence are presented suggesting that the guanine nucleotide-dependent component apparently involved in adenylate cyclase inhibition and apparently exhibiting GTPase activity is at least partially different from that involved in adenylate cyclase stimulation by hormones.