title: Role of purpurin as a retinol-binding protein in goldfish retina during the early stage of optic nerve regeneration: its priming action on neurite outgrowth.
abstract: Unlike mammals, the fish optic nerve can regenerate after injury. So far, many growth or trophic factors have been shown as an axon-regenerating molecule. However, it is totally unknown what substance regulates or triggers the activity of these factors on axonal elongation. Therefore, we constructed a goldfish retina cDNA library prepared from the retina treated with optic nerve transection 5 d previously, when it was just before regrowing optic axons after injury. A cDNA clone for goldfish purpurin for which expression was upregulated during the early stage of optic nerve regeneration was isolated from the retina cDNA library. Purpurin was discovered as a secretory retinol-binding protein in developing chicken retinas. Levels of purpurin mRNA and protein transiently increased and rapidly decreased 2-5 d and 10 d after axotomy, respectively. Purpurin mRNA was localized to the photoreceptor cells, whereas the protein was diffusely found in all of the retinal layers. A recombinant purpurin alone did not affect any change of neurite outgrowth in explant culture of the control retina, whereas a concomitant addition of the recombinant purpurin and retinol first induced a drastic enhancement of neurite outgrowth. Furthermore, the action of retinol-bound purpurin was effective only in the control (untreated) retinas but not in those primed (treated) with a previous optic nerve transection. Thus, purpurin with retinol is the first candidate molecule of priming neurite outgrowth in the early stage of optic nerve regeneration in fish.
authors.affiliation: Department of Molecular Neurobiology, Graduate School of Medicine, Faculty of Medicine, Kanazawa University, Kanazawa, Ishikawa 920-8640, Japan.
authors.forename: Toru
authors.initials: T
authors.lastname: Matsukawa
authors.forename: Kayo
authors.initials: K
authors.lastname: Sugitani
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Mawatari
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Koriyama
authors.forename: Zhongwu
authors.initials: Z
authors.lastname: Liu
authors.forename: Masayuki
authors.initials: M
authors.lastname: Tanaka
authors.forename: Satoru
authors.initials: S
authors.lastname: Kato
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D004357:Drug Synergism; D006054:Goldfish / Q000502:physiology*; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008969:Molecular Sequence Data; D009416:Nerve Regeneration / Q000235:genetics / Q000502:physiology*; D016501:Neurites / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D009900:Optic Nerve / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis; D012160:Retina / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D012177:Retinol-Binding Proteins / Q000235:genetics / Q000494:pharmacology / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D014801:Vitamin A / Q000494:pharmacology
chemical_list: D018076:DNA, Complementary; D012333:RNA, Messenger; D012177:Retinol-Binding Proteins; D014801:Vitamin A