Regulation of the phosphorylation and dephosphorylation of a 96,000 dalton phosphoprotein (P96) in intact synaptosomes.
When intact rat brain synaptosomes are depolarized there is a significant increase in the phosphorylation of many proteins, and a rapid dephosphorylation of a 96,000 dalton protein termed P96. The mechanisms governing dephosphorylation are shown to be distinct from the mechanisms leading to increased phosphorylation of proteins such as synapsin I. Depolarization-dependent P96 dephosphorylation was found to be rapid (preceding the phosphorylation of synapsin I) and fully reversible, and required both depolarization and calcium entry. The phosphorylation of P96 was specifically increased by fluphenazine and by the calcium channel agonist (BAY K 8644) and antagonist (verapamil) by unknown mechanisms. Phosphorylation was also increased in the presence of dibutyryl cAMP indicating some role for cAMP-dependent protein kinase in P96 labeling. Preliminary evidence also raises the possibility of a role for protein kinase C. The characteristics of this unique synaptosomal protein suggest that it may play an important role in nerve terminal function.
Merrell Dow Research Institute, Cincinnati, OH 45215.
P J
PJ
Robinson
D000818:Animals; D001921:Brain / Q000378:metabolism*; D002540:Cerebral Cortex / Q000378:metabolism; D003342:Corpus Striatum / Q000378:metabolism; D006706:Homeostasis; D007700:Kinetics; D008970:Molecular Weight; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D051381:Rats; D013574:Synaptosomes / Q000378:metabolism*
D009419:Nerve Tissue Proteins; D010750:Phosphoproteins; D011494:Protein Kinases