The family of guanosine triphosphate—binding proteins (G proteins) plays a key role in the transmembrane signaling pathway in a variety of cells: Gs and Gi stimulate and inhibit adenylate cyclase, respectively; Gp activates polyphosphoinositide phosphodiesterase; Gk activates K+ channels; and Go inhibits the voltage-dependent Ca2+ channel.1 Recently, Hepler and Gilman2 reviewed further advances of G protein research; they described how the task of unraveling the complexity of the G protein—regulated cellular switchboard expands exponentially as the number of identified G protein subunits continues to grow.
Measurements of the level of Gi/Go in the schizophrenic brain utilizing pertussis toxin (islet-activating protein)-catalyzed adenosine diphosphate (ADP) ribosylation showed that the amount of Gi/Go was significantly decreased in the putamen3 and hippocampus4 of the left hemisphere in schizophrenic patients compared with controls. Unfortunately, these experiments with isletactivating protein could not distinguish multiple species of subunits of pertussis toxin—sensitive G
Okada F, Murakami T, Tokumitsu Y. Low Levels of Pertussis Toxin Adenosine Diphosphate Ribosylation in the Schizophrenic Brain. Arch Gen Psychiatry. 1995;52(4):319. doi:10.1001/archpsyc.1995.03950160069016