A purine-sensitive pathway regulates multiple genes involved in axon regeneration in goldfish retinal ganglion cells.
In lower vertebrates, retinal ganglion cells (RGCs) can regenerate their axons and reestablish functional connections after optic nerve injury. We show here that in goldfish RGCs, the effects of several trophic factors converge on a purine-sensitive signaling mechanism that controls axonal outgrowth and the expression of multiple growth-associated proteins. In culture, goldfish RGCs regenerate their axons in response to two molecules secreted by optic nerve glia, axogenesis factor-1 (AF-1) and AF-2, along with ciliary neurotrophic factor. The purine analog 6-thioguanine (6-TG) blocked outgrowth induced by each of these factors. Previous studies in PC12 cells have shown that the effects of 6-TG on neurite outgrowth may be mediated via inhibition of a 47 kDa protein kinase. Growth factor-induced axogenesis in RGCs was accompanied by many of the molecular changes that characterize regenerative growth in vivo, e.g. , increased expression of GAP-43 and certain cell surface glycoproteins. 6-TG inhibited all of these changes but not those associated with axotomy per se, e.g., induction of jun family transcription factors, nor did it affect cell survival. Additional studies using RGCs from transgenic zebrafish showed that expression of Talpha-1 tubulin is likewise stimulated by AF-1 and blocked by 6-TG. The purine nucleoside inosine had effects opposite to those of 6-TG. Inosine stimulated outgrowth and the characteristic pattern of molecular changes in RGCs and competitively reversed the inhibitory effects of 6-TG. We conclude that axon regeneration and the underlying program of gene expression in goldfish RGCs are mediated via a common, purine-sensitive pathway.
Petrausch
B
B
Laboratories for Neuroscience Research in Neurosurgery, Children's Hospital, Boston, Massachusetts, USA.
Tabibiazar
R
R
Roser
T
T
Jing
Y
Y
Goldman
D
D
Stuermer
C A
CA
Irwin
N
N
Benowitz
L I
LI
D020410:Activated-Leukocyte Cell Adhesion Molecule / Q000096:biosynthesis; D000818:Animals; D000954:Antigens, Surface; D001369:Axons / Q000187:drug effects / Q000378:metabolism*; D001667:Binding, Competitive / Q000187:drug effects; D015816:Cell Adhesion Molecules, Neuronal / Q000096:biosynthesis; D002478:Cells, Cultured; D020934:Ciliary Neurotrophic Factor / Q000378:metabolism / Q000494:pharmacology; D029941:Fish Proteins; D019922:GAP-43 Protein / Q000096:biosynthesis; D015870:Gene Expression / Q000187:drug effects; D006054:Goldfish; D006133:Growth Substances / Q000378:metabolism / Q000494:pharmacology; D006150:Guanine Nucleotides / Q000494:pharmacology; D007288:Inosine / Q000378:metabolism / Q000494:pharmacology; D008565:Membrane Proteins / Q000378:metabolism; D009416:Nerve Regeneration / Q000235:genetics*; D009419:Nerve Tissue Proteins / Q000378:metabolism; D016501:Neurites / Q000187:drug effects / Q000378:metabolism; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D011687:Purines / Q000378:metabolism* / Q000494:pharmacology; D012165:Retinal Ganglion Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013873:Thionucleotides / Q000494:pharmacology; D014404:Tubulin / Q000096:biosynthesis
D020410:Activated-Leukocyte Cell Adhesion Molecule; D000954:Antigens, Surface; D015816:Cell Adhesion Molecules, Neuronal; D020934:Ciliary Neurotrophic Factor; C105524:E587 protein, Carassius auratus; D029941:Fish Proteins; D019922:GAP-43 Protein; D006133:Growth Substances; D006150:Guanine Nucleotides; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D016755:Proto-Oncogene Proteins c-jun; D011687:Purines; D013873:Thionucleotides; D014404:Tubulin; C104436:reggie-2 protein, Carassius auratus; C003964:6-thioguanylic acid; D007288:Inosine