| Heterotrimeric guanine nucleotide-binding proteins (G proteins) consist of α, β and γ subunits and mediate the effects of hormones, neurotransmitters, chemokines and sensory stimuli. To date, over 20 known Gα subunits have been classified into four families, Gα(s), Gα(i/o), Gα(q) and Gα(12), based on structural and functional similarities (1,2). Phosphorylation of Tyr356 of Gα(q)/Gα(11) is essential for activation of the G protein, since phenylalanine substitution for Tyr356 changes the interaction of Gα with receptors and abolishes ligand-induced IP3 formation (3).Gα(o) is the most abundant G protein in the brain and couples to serotonin, dopamine, GABA (B), opioid, glutamate and cholinergic receptors (4). Gα(o) -/- mice have neurological defects such as tremors, seizures and poor motor coordination (5). |
