Competitive inhibition of the high-affinity choline transporter by tetrahydropyrimidine anthelmintics.
The high-affinity choline transporter CHT1 mediates choline uptake, the rate-limiting and regulatory step in acetylcholine synthesis at cholinergic presynaptic terminals. CHT1-medated choline uptake is specifically inhibited by hemicholinium-3, which is a type of choline analog that acts as a competitive inhibitor. Although the substrate choline and the inhibitor hemicholinium-3 are well-established ligands of CHT1, few potent ligands other than choline analogs have been reported. Here we show that tetrahydropyrimidine anthelmintics, known as nicotinic acetylcholine receptor agonists, act as competitive inhibitors of CHT1. A ligand-dependent trafficking assay in cell lines expressing human CHT1 was designed to search for CHT1 ligands from a collection of biologically active compounds. We found that morantel as well as other tetrahydropyrimidines, pyrantel and oxantel, potently inhibits the high-affinity choline uptake activity of CHT1 in a competitive manner similar to the inhibitor hemicholinium-3. They also inhibit the high-affinity choline transporter from the nematode Caenorhabditis elegans. Finally, tetrahydropyrimidines potently inhibit the high-affinity choline uptake in rat brain synaptosomes at a low micromolar level, resulting in the inhibition of acetylcholine synthesis. The rank order of potency in synaptosomes is as follows: morantel > pyarantel > oxantel (Ki = 1.3, 5.7, and 8.3 μM, respectively). Our results reveal that tetrahydropyrimidine anthelmintics are novel CHT1 ligands that inhibit the high-affinity choline uptake for acetylcholine synthesis in cholinergic neurons.
['Okuda|Takashi|T|', 'Nomura|Yuki|Y|', 'Konishi|Asami|A|', 'Misawa|Hidemi|H|']
D000818:Animals D000871:Anthelmintics D001667:Binding, Competitive D001692:Biological Transport D001921:Brain D027682:Cation Transport Proteins D002794:Choline D005260:Female D057809:HEK293 Cells D006801:Humans D008024:Ligands D051379:Mice D009015:Morantel D011485:Protein Binding D021381:Protein Transport D011715:Pyrantel D011743:Pyrimidines D027981:Symporters D013574:Synaptosomes
High-affinity choline transporter Tetrahydropyrimidine anthelmintics CHT1 Acetylcholine Competitive inhibitor Ligand screening