Protein phosphorylation and synaptic transmission: receptor mediated modulation of protein kinase C in a rat brain fraction enriched in synaptosomes.
Aspects of protein phosphorylation related to events occurring during synaptic transmission were briefly reviewed. High resolution two-dimensional electrophoresis was used to study protein phosphorylation catalysed by protein kinase C in a fraction from rat brain enriched in synaptosomes. Incubation of 32P-labelled synaptosomes with 4 beta-phorbol 12 beta-myristate 13 alpha-acetate resulted in an increase in the phosphorylation of a 45 K polypeptide (generally known as B-50) and an 82 K polypeptide; other major phosphoproteins in the preparation were unaffected by this treatment. It appears therefore that the 45 K and 82 K polypeptides are the only significant substrates for protein kinase C in synaptosomes. Depolarisation of labelled synaptosomes by high K+ increased the phosphorylation of the 82 K polypeptide, synapsin I and several unknown phosphoproteins. Incubation of labelled synaptosomes with the cholinergic agonist carbachol resulted in a modest, but statistically significant, increase in the phosphorylation of the 45 K (B-50) and 82 K polypeptides. This effect was blocked by atropine. The results are discussed in relation to a possible role for the B-50 phosphoprotein in regulating the resynthesis of polyphosphoinositides following cholinergic stimulation.
D000818:Animals; D001921:Brain / Q000502:physiology*; D002217:Carbachol / Q000494:pharmacology; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D010766:Phosphorylation; D011188:Potassium / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D017981:Receptors, Neurotransmitter / Q000502:physiology; D013569:Synapses / Q000502:physiology*; D009435:Synaptic Transmission; D013574:Synaptosomes / Q000502:physiology*
D009419:Nerve Tissue Proteins; D017981:Receptors, Neurotransmitter; D002217:Carbachol; D011493:Protein Kinase C; D011188:Potassium