title: Localization in mammalian brain of G-substrate, a specific substrate for guanosine 3',5'-cyclic monophosphate-dependent protein kinase.
abstract: The regional and cellular distribution of G-substrate, a 23,000-dalton protein substrate specific for guanosine 3',5'-cyclic monophosphate-dependent protein kinase, has been examined in mammalian brain using immunoprecipitation, radioimmunoassay, and peptide-mapping techniques. In rabbit brain, G-substrate was found to be highly concentrated in the cerebellum. The concentration of G-substrate in cerebellar cytosol was 27.2 pmol/mg. The concentrations of G-substrate in cortex, hippocampus, and caudate were only 1 to 2% of that found in cerebellum. Studies of neurological mutant mice lacking either Purkinje cells (PCD and nervous) or granule cells (weaver) suggested that, within the cerebellum, G-substrate is localized almost exclusively in Purkinje cells. A phosphoprotein present in noncerebellar brain regions, which co-migrated with G-substrate on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, was shown by peptide mapping to consist predominantly of phosphatase inhibitor-1. Phosphatase inhibitor-1, a potent inhibitor of protein phosphatase-1, is known to share several physicochemical properties with G-substrate. In contrast to the results obtained with G-substrate, the concentration of phosphatase inhibitor-1 was significantly lower in cerebellum than in other major brain regions. These and other data suggest that G-substrate may be a Purkinje cell-specific protein phosphatase inhibitor.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001921:Brain / Q000378:metabolism*; D002352:Carrier Proteins; D002421:Caudate Nucleus / Q000378:metabolism; D002531:Cerebellum / Q000378:metabolism; D002540:Cerebral Cortex / Q000378:metabolism; D006152:Cyclic GMP / Q000494:pharmacology*; D006624:Hippocampus / Q000378:metabolism; D007163:Immunosorbent Techniques; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D008818:Mice, Neurologic Mutants; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism; D011817:Rabbits; D011863:Radioimmunoassay; D013379:Substrate Specificity; D014018:Tissue Distribution
chemical_list: D000596:Amino Acids; D002352:Carrier Proteins; C029152:G-substrate; D047908:Intracellular Signaling Peptides and Proteins; D009419:Nerve Tissue Proteins; D011506:Proteins; C021042:protein phosphatase inhibitor-1; D011494:Protein Kinases; D006152:Cyclic GMP