Essential roles for GSK-3s and GSK-3-primed substrates in neurotrophin-induced and hippocampal axon growth.
Glycogen synthase kinase-3beta (GSK-3beta) is thought to mediate morphological responses to a variety of extracellular signals. Surprisingly, we found no gross morphological deficits in nervous system development in GSK-3beta null mice. We therefore designed an shRNA that targeted both GSK-3 isoforms. Strong knockdown of both GSK-3alpha and beta markedly reduced axon growth in dissociated cultures and slice preparations. We then assessed the role of different GSK-3 substrates in regulating axon morphology. Elimination of activity toward primed substrates only using the GSK-3 R96A mutant was associated with a defect in axon polarity (axon branching) compared to an overall reduction in axon growth induced by a kinase-dead mutant. Consistent with this finding, moderate reduction of GSK-3 activity by pharmacological inhibitors induced axon branching and was associated primarily with effects on primed substrates. Our results suggest that GSK-3 is a downstream convergent point for many axon growth regulatory pathways and that differential regulation of primed versus all GSK-3 substrates is associated with a specific morphological outcome.
Kim
Woo-Yang
WY
UNC Neuroscience Center, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
Zhou
Feng-Quan
FQ
Zhou
Jiang
J
Yokota
Yukako
Y
Wang
Yan-Min
YM
Yoshimura
Takeshi
T
Kaibuchi
Kozo
K
Woodgett
James R
JR
Anton
E S
ES
Snider
William D
WD
D000818:Animals; D001369:Axons / Q000187:drug effects* / Q000502:physiology; D015153:Blotting, Western; D002452:Cell Count / Q000379:methods; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004622:Embryo, Mammalian; D005455:Fluorescent Antibody Technique / Q000379:methods; D005727:Ganglia, Spinal / Q000166:cytology / Q000187:drug effects; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects / Q000502:physiology; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors / Q000502:physiology*; D006624:Hippocampus / Q000166:cytology*; D066298:In Vitro Techniques; D007211:Indoles / Q000494:pharmacology; D051379:Mice; D018345:Mice, Knockout; D008869:Microtubule-Associated Proteins / Q000502:physiology; D008954:Models, Biological; D009154:Mutation / Q000502:physiology; D019579:Neocortex / Q000166:cytology / Q000187:drug effects; D020932:Nerve Growth Factor / Q000494:pharmacology*; D009474:Neurons / Q000166:cytology* / Q000187:drug effects; D010091:Oximes / Q000494:pharmacology; D014162:Transfection / Q000379:methods
C483321:6-bromoindirubin-3'-oxime; D007211:Indoles; D008869:Microtubule-Associated Proteins; D010091:Oximes; D020932:Nerve Growth Factor; D038362:Glycogen Synthase Kinase 3