A dopamine- and cyclic AMP-regulated phosphoprotein enriched in dopamine-innervated brain regions

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Abstract
Several mammalian neurotransmitter candidates, for example, serotonin1, dopamine2,3 and noradrenaline4,5, may exert some of their synaptic effects by regulating protein phosphorylation systems6,7. Comparison of the regional distribution of brain phosphoproteins with neurotransmitter systems may help to identify the specific phosphoproteins involved in the functions of particular neurotransmitters. Here we report the association of one such phosphoprotein with the dopamine pathways in brain. This protein, of apparent molecular weight (MW) 32,000 (32K), seems to be present only in nervous tissue. Its regional distribution within the brain is very similar to the pattern of dopamine-containing nerve terminals; more specifically, the protein appears to be enriched in those dopaminoceptive neurones which possess D-1 receptors (dopamine receptors coupled to adenylate cyclase8). The state of phosphorylation of the protein in these dopaminoceptive neurones can be regulated by both dopamine and cyclic AMP. These results suggest that the phosphoprotein may mediate certain of the transsynaptic effects of dopamine acting on dopaminoceptive neurones.