Antibodies directed against ubiquitin inhibit high affinity [3H]choline uptake in rat cerebral cortical synaptosomes.
Sodium-dependent [3H]choline uptake and coupled [3H]acetylcholine synthesis were inhibited in rat cerebral cortical synaptosomes in a dose- (1-10 micrograms/ml) and time-dependent manner by affinity-purified antibodies directed against ubiquitin (anti-Ub). Neither sodium-independent [3H]choline uptake nor [3H]acetylcholine release was affected by up to 10 micrograms/ml anti-Ub, indicating that the cholinergic terminals were not depolarized by the anti-Ub. Binding of anti-Ub to synaptosomes, as measured with 125I-protein A, was saturable and occurred over the same concentration range (1-10 micrograms/ml) at which uptake inhibition was observed. Although preimmune IgG bound to the synaptosome preparation to a greater extent and was apparently not readily saturable, this fortuitous binding was without effect on high affinity choline uptake and conversion to acetylcholine. The results suggest the presence of a ubiquitin-protein conjugate on the synaptosomal surface and a functional relationship between this protein conjugate and the sodium-dependent choline transport system.
D000818:Animals; D000906:Antibodies; D000936:Antigen-Antibody Complex; D001692:Biological Transport; D002540:Cerebral Cortex / Q000378:metabolism*; D002794:Choline / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D013574:Synaptosomes / Q000378:metabolism*; D014316:Tritium; D014452:Ubiquitins / Q000276:immunology / Q000378:metabolism*
D000906:Antibodies; D000936:Antigen-Antibody Complex; D014452:Ubiquitins; D014316:Tritium; D002794:Choline