title: ARPP-21, a cAMP-regulated phosphoprotein enriched in dopamine-innervated brain regions: tissue distribution and regulation of phosphorylation in rat brain.
abstract: ARPP-21 (cAMP-regulated phosphoprotein, Mr = 21,000 as determined by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate), a phosphoprotein substrate for cAMP-dependent protein kinase, is unevenly distributed in adult rat brain. Using immunoblotting and phosphorylation in vitro followed by immunoprecipitation, ARPP-21 was found to be enriched in caudate-putamen, substantia nigra, nucleus accumbens and olfactory tubercle. Intermediate levels were found in cerebral cortex and hippocampus. ARPP-21 was very low in most other brain areas and was not detected in any of the peripheral tissues studied. Following unilateral lesion of the caudate-putamen with quinolinic acid, a marked decrease in the levels of ARPP-21 was observed in both the lesioned caudate-putamen (-75%) and the ipsilateral substantia nigra (-70%) compared with the unlesioned side. This result demonstrates the enrichment of ARPP-21 in striatonigral neurons. In slices of caudate-putamen, substantia nigra or cerebral cortex incubated in vitro, the phosphorylation of ARPP-21 was enhanced by 8-Br-cAMP, a stable analog of cAMP. In striatal slices, forskolin, a compound which stimulates adenylate cyclase directly, enhanced the phosphorylation of ARPP-21 with an EC50 of 0.5 microM. In conclusion, ARPP-21 is a neuron-specific phosphoprotein enriched in specific brain areas which are known to receive a rich dopaminergic innervation and to contain high levels of D1 dopamine receptors. The phosphorylation of ARPP-21 is likely to mediate some of the intracellular effects of neurotransmitters which stimulate adenylate cyclase in these regions, in particular dopamine and vasoactive intestinal peptide.
authors.affiliation: Laboratory of Molecular and Cellular Neuroscience, Rockefeller University, New York, NY 10021.
authors.forename: J A
authors.initials: JA
authors.lastname: Girault
authors.forename: S I
authors.initials: SI
authors.lastname: Walaas
authors.forename: H C
authors.initials: HC
authors.lastname: Hemmings
authors.forename: P
authors.initials: P
authors.lastname: Greengard
mesh_terms: D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D001923:Brain Chemistry / Q000502:physiology*; D002421:Caudate Nucleus / Q000187:drug effects / Q000378:metabolism; D000242:Cyclic AMP / Q000502:physiology*; D004298:Dopamine / Q000502:physiology*; D066298:In Vitro Techniques; D008297:Male; D009419:Nerve Tissue Proteins / Q000502:physiology*; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D010750:Phosphoproteins / Q000502:physiology*; D010766:Phosphorylation; D011699:Putamen / Q000187:drug effects / Q000378:metabolism; D017378:Quinolinic Acid; D011805:Quinolinic Acids / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013378:Substantia Nigra / Q000187:drug effects / Q000502:physiology
chemical_list: D009419:Nerve Tissue Proteins; D010750:Phosphoproteins; D011805:Quinolinic Acids; C061368:cyclic AMP-regulated phosphoprotein ARPP-21; D015124:8-Bromo Cyclic Adenosine Monophosphate; D000242:Cyclic AMP; D017378:Quinolinic Acid; D004298:Dopamine