title: Synthesis of disialyl Lewis a (Le(a)) structure in colon cancer cell lines by a sialyltransferase, ST6GalNAc VI, responsible for the synthesis of alpha-series gangliosides.
abstract: Biosynthesis of disialyl Lewis a (Lea) was analyzed using previously cloned ST6GalNAc V and ST6GalNAc VI, which were responsible for the synthesis of alpha-series gangliosides. Among lactotetraosylceramide (Lc4), neolactotetraosylceramide, and their sialyl forms, only sialyl Lc4 was sialylated with ST6GalNAc V and ST6GalNAc VI. The products were confirmed to be disialyl Lea in TLC-immunostaining. Compared with the original substrate GM1b, the synthetic rates of disialyl Lea were 22 and 38% with ST6GalNAc V and ST6GalNAc VI, respectively. Since sialyl Lea could not be converted to disialyl Lea, disialyl Lea was produced only from disialyl Lc4. Therefore, it appears that ST6GalNAc V/VI and fucosyltransferase III (FUT-3) compete for sialyl Lc4, their common substrate. The results of either one transfection or co-transfection of two genes into COS1 cells revealed that both ST6GalNAc VI and FUT-3 contributed in the synthesis of disialyl Lea but partly compete with each other. Many colon cancer cell lines expressed the ST6GalNAc VI gene more or less, and some of them actually expressed disialyl Lea. None of them expressed ST6GalNAc V. These results suggested the novel substrate specificity of ST6GalNAc VI, which is responsible for the synthesis of disialyl Lea but not for alpha-series gangliosides in human colon tissues.
authors.affiliation: Department of Biochemistry II, Nagoya University School of Medicine, 65 Tsurumai, Showa-ku, Nagoya, 466-0065, Japan.
authors.forename: Akiko
authors.initials: A
authors.lastname: Tsuchida
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Okajima
authors.forename: Keiko
authors.initials: K
authors.lastname: Furukawa
authors.forename: Takayuki
authors.initials: T
authors.lastname: Ando
authors.forename: Hideharu
authors.initials: H
authors.lastname: Ishida
authors.forename: Aruto
authors.initials: A
authors.lastname: Yoshida
authors.forename: Yoko
authors.initials: Y
authors.lastname: Nakamura
authors.forename: Reiji
authors.initials: R
authors.lastname: Kannagi
authors.forename: Makoto
authors.initials: M
authors.lastname: Kiso
authors.forename: Koichi
authors.initials: K
authors.lastname: Furukawa
mesh_terms: D000818:Animals; D015295:Antigens, Tumor-Associated, Carbohydrate / Q000096:biosynthesis*; D018395:CA-19-9 Antigen; D019556:COS Cells; D002240:Carbohydrate Sequence; D002522:Chlorocebus aethiops; D003001:Cloning, Molecular; D003110:Colonic Neoplasms; D005732:Gangliosides / Q000096:biosynthesis*; D006801:Humans; D007739:L Cells; D051379:Mice; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000378:metabolism; D012799:Sialyltransferases / Q000378:metabolism*; D013379:Substrate Specificity; D014407:Tumor Cells, Cultured
chemical_list: D015295:Antigens, Tumor-Associated, Carbohydrate; D018395:CA-19-9 Antigen; D005732:Gangliosides; D011994:Recombinant Proteins; C476448:disialyl Lewis a antigen; C064564:sialyl Le(a) ganglioside; C476449:GalNAc sialyltransferase VI; D012799:Sialyltransferases