title: Inhibition of CRMP2 phosphorylation repairs CNS by regulating neurotrophic and inhibitory responses.
abstract: Central nervous system (CNS) regeneration is restricted by both the lack of neurotrophic responses and the presence of inhibitory factors. As of yet, a common mediator of these two pathways has not been identified. Microtubule dynamics is responsible for several key processes after CNS injuries: intracellular trafficking of receptors for neurotrophic factors, axonal retraction by inhibitory factors, and secondary tissue damages by inflammation and scarring. Kinases regulating microtubule organization, such as Cdk5 or GSK3β, may play pivotal roles during CNS recovery, but the molecular mechanisms remain to be elucidated. Collapsin response mediator protein 2 (CRMP2) stabilizes cytoskeletal polymerization, while CRMP2 phosphorylation by Cdk5 and GSK3β loses its affinity for cytoskeleton proteins, leading to the inhibition of axonal growth. Here, we characterized CRMP2 phosphorylation as the first crucial factor regulating neurotrophic and inhibitory responses after spinal cord injury (SCI). We found that pharmacological inhibition of GSK3β enhanced brain-derived neurotrophic factor (BDNF)-induced axonal growth response in cultured dorsal root ganglion (DRG) neurons. DRG neurons from CRMP2 knock-in (Crmp2KI/KI) mice, where CRMP2 phosphorylation was eliminated, showed elevated sensitivity to BDNF as well. Additionally, cultured Crmp2KI/KI neurons exhibited suppressed axonal growth inhibition by chondroitin sulfate proteoglycan (CSPG). These data suggest a couple of new molecular insights: the BDNF/GSK3β/CRMP2 and CSPG/GSK3β/CRMP2 pathways. Next, we tested the significance of CRMP2 phosphorylation after CNS injury in vivo. The phosphorylation level of CRMP2 was enhanced in the injured spinal cord. Crmp2KI/KI mice exhibited prominent recovery of locomotive and nociceptive functions after SCI, which correlated with the enhanced axonal growth of the motor and sensory neurons. Neuroprotective effects against SCI, such as microtubule stabilization, reduced inflammation, and suppressed scarring were also observed by inhibiting CRMP2 phosphorylation. Therefore, inhibition of CRMP2 phosphorylation demonstrates the unique potential to repair SCI by both enhancing sensitivity to BDNF and reducing inhibitory responses.
authors.affiliation: Department of Life Science and Medical Bioscience, Graduate School of Advanced Science and Engineering, TWIns, Waseda University, Tokyo 162-8480, Japan; Research Fellow of Japan Society for the Promotion of Science, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Nagai
authors.affiliation: Department of Life Science and Medical Bioscience, Graduate School of Advanced Science and Engineering, TWIns, Waseda University, Tokyo 162-8480, Japan.
authors.forename: Kazuki
authors.initials: K
authors.lastname: Owada
authors.affiliation: Department of Life Science and Medical Bioscience, Graduate School of Advanced Science and Engineering, TWIns, Waseda University, Tokyo 162-8480, Japan.
authors.forename: Yoshiteru
authors.initials: Y
authors.lastname: Kitamura
authors.affiliation: Department of Molecular Pharmacology and Neurobiology, Graduate School of Medicine, Yokohama City University, Yokohama 236-0004, Japan.
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Goshima
authors.affiliation: Department of Life Science and Medical Bioscience, Graduate School of Advanced Science and Engineering, TWIns, Waseda University, Tokyo 162-8480, Japan. Electronic address: ohshima@waseda.jp.
authors.forename: Toshio
authors.initials: T
authors.lastname: Ohshima
mesh_terms: D000818:Animals; D001369:Axons / Q000378:metabolism / Q000473:pathology; D019208:Brain-Derived Neurotrophic Factor / Q000378:metabolism / Q000494:pharmacology; D002478:Cells, Cultured; D002490:Central Nervous System / Q000378:metabolism*; D011508:Chondroitin Sulfate Proteoglycans / Q000378:metabolism; D004195:Disease Models, Animal; D005727:Ganglia, Spinal / Q000166:cytology; D005786:Gene Expression Regulation / Q000235:genetics / Q000502:physiology*; D006614:Hindlimb / Q000503:physiopathology; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D008870:Microtubules / Q000378:metabolism / Q000473:pathology; D000068079:Motor Disorders / Q000209:etiology*; D009154:Mutation / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation / Q000502:physiology; D013119:Spinal Cord Injuries / Q000150:complications* / Q000473:pathology*; D015054:Zymosan / Q000494:pharmacology
chemical_list: D019208:Brain-Derived Neurotrophic Factor; D011508:Chondroitin Sulfate Proteoglycans; D036341:Intercellular Signaling Peptides and Proteins; D009419:Nerve Tissue Proteins; C095114:collapsin response mediator protein-2; D015054:Zymosan
keywords: Axonal growth inhibitors; Cytoskeleton; Inflammation; Neurotrophin; Regeneration; Scar; Spinal cord injury