title: Cell internalization and traffic pathway of Clostridium botulinum type C neurotoxin in HT-29 cells.
abstract: The bacterium Clostridium botulinum type C produces a progenitor toxin (C16S toxin) that binds to O-linked sugar chains terminating with sialic acid on the surface of HT-29 cells prior to internalization [A. Nishikawa, N. Uotsu, H. Arimitsu, J.C. Lee, Y. Miura, Y. Fujinaga, H. Nakada, T. Watanabe, T. Ohyama, Y. Sakano, K. Oguma, Biochem. Biophys. Res. Commun. 319 (2004) 327-333] [21]. Based on this, it was hypothesized that the C16S toxin is internalized via clathrin-coated pits. To examine this possibility, the internalized toxin was observed with a fluorescent antibody using confocal laser-scanning microscopy. The confocal images clearly indicated that the C16S toxin was internalized mainly via clathrin-coated pits and localized in early endosomes. The toxin was colocalized with caveolin-1 which is one of the components of caveolae, however, implying the toxin was also internalized via caveolae. The confocal images also showed that the neurotoxin transported to the endosome was transferred to the Golgi apparatus. However, the non-toxic components were not merged with the Golgi marker protein, TGN38, implying the neurotoxin was dissociated from progenitor toxin in endosomes. These results suggested that the C16S toxin was separated to the neurotoxin and other proteins in endosome and the neurotoxin was further transferred to the Golgi apparatus which is the center for protein sorting.
authors.affiliation: Department of Applied Biological Science, and Department of Biotechnology, United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology, Fuchu-shi, 183-8509 Tokyo, Japan.
authors.forename: Nobuo
authors.initials: N
authors.lastname: Uotsu
authors.forename: Atsushi
authors.initials: A
authors.lastname: Nishikawa
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Watanabe
authors.forename: Tohru
authors.initials: T
authors.lastname: Ohyama
authors.forename: Takashi
authors.initials: T
authors.lastname: Tonozuka
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Sakano
authors.forename: Keiji
authors.initials: K
authors.lastname: Oguma
mesh_terms: D001692:Biological Transport; D001905:Botulinum Toxins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism; D006023:Glycoproteins / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism; D019073:HT29 Cells; D006801:Humans; D021962:Membrane Microdomains / Q000378:metabolism; D021381:Protein Transport; D011956:Receptors, Cell Surface / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D006023:Glycoproteins; D011956:Receptors, Cell Surface; D002784:Cholesterol; D001905:Botulinum Toxins; C096324:botulinum toxin type C