Nerve growth cones isolated from fetal rat brain. II. Cyclic adenosine 3':5'-monophosphate (cAMP)-binding proteins and cAMP-dependent protein phosphorylation.
Cyclic adenosine 3':5'-monophosphate (cAMP)-binding proteins and cAMP-dependent protein phosphorylation were examined in growth cone particles (GCPs) prepared from fetal rat brain. Several major proteins which specifically bind a photoactivatable analogue of cAMP are observed in GCPs and correspond to isoelectric variants of the regulatory subunits of the cAMP-dependent protein kinase described in adult brain. We found no evidence for differential compartmentalization of specific cAMP-binding proteins in subcellular fractions of fetal brain or within GCPs. cAMP-stimulated phosphoproteins of GCPs are similar to cAMP-dependent protein kinase substrates characterized in nerve terminals (synaptosomes) of adult brain and include the nerve terminal-specific protein, synapsin I. However, as shown in the companion paper (Katz, F., L. Ellis, and K. H. Pfenninger (1985) J. Neurosci. 5: 1402-1411), this synaptic phosphoprotein is not the major kinase substrate in the GCP fraction. The finding of synapsin I in a subcellular fraction prepared from fetal brain suggests that components of the mature nerve terminal are already present in fetal brain during neuronal sprouting and prior to synaptogenesis.
D000818:Animals; D001921:Brain / Q000378:metabolism; D001923:Brain Chemistry; D002352:Carrier Proteins / Q000032:analysis* / Q000378:metabolism; D002373:Cyclic AMP Receptor Protein; D004591:Electrophoresis, Polyacrylamide Gel; D005333:Fetus / Q000032:analysis; D010750:Phosphoproteins / Q000032:analysis; D010766:Phosphorylation; D011494:Protein Kinases / Q000032:analysis / Q000378:metabolism; D051381:Rats; D013574:Synaptosomes / Q000032:analysis / Q000378:metabolism
D002352:Carrier Proteins; D002373:Cyclic AMP Receptor Protein; D010750:Phosphoproteins; D011494:Protein Kinases