ARPP-39, A MEMBRANE-ASSOCIATED SUBSTRATE FOR CYCLIC-AMP-DEPENDENT PROTEIN-KINASE PRESENT IN NEOSTRIATAL NEURONS

This study describes a cyclic AMP-regulated phosphoprotein that displa ys a distinct cellular and regional distribution in rat brain. The pro tein is found only in neostriatal regions, where it is enriched in ner ve cells and not in afferent or efferent axons or in glial cells. On s ubcellular fractionation, it appears tightly associated with particula te components, possibly the synaptic plasma membrane fraction. The pro tein may therefore be specifically enriched in dendrites and/or somata of neostriatal neurons. Following phosphorylation in vitro with [gamm a-P-32]ATP and cyclic AMP-dependent protein kinase, the protein contai ns phosphoseryl residues on multiple thermolytic peptides. The specifi c cellular and subcellular localization we have observed suggests that this protein, termed ARPP-39 (cyclic AMP-regulated phosphoprotein, M( r) = 39,000) may be important in receptor-regulated, cyclic AMP-mediat ed functions in distinct neostriatal neurons.