Expression of a putative vesicular acetylcholine transporter facilitates quantal transmitter packaging.
A putative vesicular acetylcholine transporter (VAChT) was overexpressed in developing Xenopus spinal neurons by injection of rat VAChT cDNA or synthetic mRNA into Xenopus embryos. This resulted in a marked increase in the amplitude and frequency of miniature excitatory postsynaptic currents at neuromuscular synapses, reflecting an over 10-fold increase in the vesicular packaging of acetylcholine (ACh). The effect appeared in developing neurons even before synaptogenesis and was blocked by L-vesamicol, a specific blocker of ACh uptake into synaptic vesicles. Mutational studies showed that two highly conserved aspartate residues within putative transmembrane domains 4 and 10 are essential for the transport activity. These results provide direct evidence for the physiological function of a putative VAChT and demonstrate that quantal size can be regulated by changes in vesicular transporter activity.
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Department of Biology, University of California at San Diego, La Jolla 92093, USA.
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Bellocchio
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Edwards
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D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D001224:Aspartic Acid / Q000235:genetics; D001757:Blastomeres; D002352:Carrier Proteins / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D002478:Cells, Cultured; D004625:Embryo, Nonmammalian / Q000737:chemistry / Q000502:physiology; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D026901:Membrane Transport Proteins; D008845:Microinjections; D009132:Muscles / Q000166:cytology; D016296:Mutagenesis / Q000502:physiology; D009420:Nervous System / Q000166:cytology; D009467:Neuromuscular Depolarizing Agents / Q000494:pharmacology; D009474:Neurons / Q000737:chemistry / Q000502:physiology / Q000648:ultrastructure; D018408:Patch-Clamp Techniques; D010880:Piperidines / Q000494:pharmacology; D051381:Rats; D013569:Synapses / Q000737:chemistry / Q000502:physiology; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D016708:Synaptophysin / Q000032:analysis; D050494:Vesicular Acetylcholine Transport Proteins; D033921:Vesicular Transport Proteins; D014982:Xenopus laevis
D002352:Carrier Proteins; D026901:Membrane Transport Proteins; D009467:Neuromuscular Depolarizing Agents; D010880:Piperidines; C493461:Slc18a3 protein, rat; D016708:Synaptophysin; D050494:Vesicular Acetylcholine Transport Proteins; D033921:Vesicular Transport Proteins; D001224:Aspartic Acid; C006189:vesamicol; D000109:Acetylcholine