title: Rat choline acetyltransferase of the peripheral type differs from that of the common type in intracellular translocation.
abstract: Choline acetyltransferase (ChAT), the synthesizing enzyme for acetylcholine, has been implicated to involve multiple isoforms of ChAT mRNA in several animals. Since these isoforms are mostly non-coding splice variants, only a homologous ChAT protein of about 68 kDa has been shown to be produced in vivo. Recent evidence indicates the existence of a protein coding splice variant of ChAT mRNA, which lacks exons 6-9 of the rat ChAT gene. The encoded protein was designated ChAT of a peripheral type (pChAT), because of its preferential expression in the peripheral nervous system as confirmed by Western blot and immunohistochemistry. However, functional significance of pChAT is unknown. To obtain a clue to this question, we examined a possible difference in intracellular trafficking between pChAT and the well-known ChAT of the common type (cChAT) using green fluorescent protein (GFP) in living human embryonic kidney cells. Confocal laser scanning microscopy revealed that pChAT-GFP was detectable in the cytoplasm but not in the nucleus, whereas cChAT-GFP was found in both cytoplasm and nucleus. Following treatment with leptomycin B, a nuclear export pathway inhibitor, pChAT-GFP became detectable in both cytoplasm and nucleus, indicating that pChAT can be translocated to the nucleus. In contrast, the leptomycin B treatment did not seem to affect the content of intranuclear cChAT-GFP. After incubation with protein kinase C inhibitors, enhanced accumulation of pChAT-GFP but not cChAT-GFP occurred in the nucleus. These results clearly indicate that pChAT varies from cChAT in intracellular transportation, probably reflecting the difference in physiological roles between pChAT and cChAT.
authors.affiliation: Molecular Neuroscience Research Center, Shiga University of Medical Science, Seta Tsukinowa-cho, Otsu, Shiga 520-2192, Japan.
authors.forename: Akinori
authors.initials: A
authors.lastname: Matsuo
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Bellier
authors.forename: Tadashi
authors.initials: T
authors.lastname: Hisano
authors.forename: Yoshinari
authors.initials: Y
authors.lastname: Aimi
authors.forename: Osamu
authors.initials: O
authors.lastname: Yasuhara
authors.forename: Ikuo
authors.initials: I
authors.lastname: Tooyama
authors.forename: Naoaki
authors.initials: N
authors.lastname: Saito
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kimura
mesh_terms: D000109:Acetylcholine / Q000096:biosynthesis*; D021581:Active Transport, Cell Nucleus / Q000187:drug effects / Q000502:physiology; D017398:Alternative Splicing / Q000502:physiology*; D000818:Animals; D002467:Cell Nucleus / Q000201:enzymology; D002478:Cells, Cultured; D002490:Central Nervous System / Q000201:enzymology*; D002795:Choline O-Acetyltransferase / Q000235:genetics / Q000378:metabolism*; D003342:Corpus Striatum / Q000201:enzymology; D003593:Cytoplasm / Q000201:enzymology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D005726:Ganglia, Parasympathetic / Q000201:enzymology; D049452:Green Fluorescent Proteins; D006801:Humans; D008297:Male; D017933:Peripheral Nervous System / Q000201:enzymology*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology; D051381:Rats
chemical_list: D004791:Enzyme Inhibitors; D005231:Fatty Acids, Unsaturated; D020033:Protein Isoforms; D049452:Green Fluorescent Proteins; D002795:Choline O-Acetyltransferase; D011493:Protein Kinase C; D000109:Acetylcholine; C038753:leptomycin B