Regulation of hemicholinium binding sites in isolated nerve terminals.
High-affinity uptake of choline, the rate-limiting, regulatory step for the synthesis of acetylcholine is regulated via presynaptic auto- and heteroreceptors. Binding studies using tritiated hemicholinium-3 ([3H]HCh-3) as the specific ligand for the choline carrier revealed that the number of hemicholinium binding sites in nerve terminals isolated from insect brain changes corresponding to the activity of synaptosomal kinase A and kinase C. Activation of kinase A apparently increases the total number of hemicholinium binding sites by recruiting additional occult carriers, whereas the effect of kinase C activity is most appropriately explained by preventing a down-regulation of carrier proteins. The kinase-mediated regulation of choline transporters is obviously due to a phosphorylation of the carrier protein itself.
Knipper
M
M
University of Stuttgart-Hohenheim, Institute of Zoophysiology, Federal Republic of Germany.
Kahle
C
C
Breer
H
H
D000818:Animals; D002352:Carrier Proteins / Q000302:isolation & purification; D002794:Choline / Q000378:metabolism; D000242:Cyclic AMP / Q000494:pharmacology; D006110:Grasshoppers / Q000502:physiology*; D066298:In Vitro Techniques; D009411:Nerve Endings / Q000378:metabolism*; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism; D011869:Radioligand Assay; D011956:Receptors, Cell Surface / Q000502:physiology*; D013574:Synaptosomes / Q000378:metabolism*
D002352:Carrier Proteins; D011956:Receptors, Cell Surface; D015240:Phorbol 12,13-Dibutyrate; D000242:Cyclic AMP; D011494:Protein Kinases; D011493:Protein Kinase C; D002794:Choline