title: Promotion of Functional Nerve Regeneration by Inhibition of Microtubule Detyrosination.
abstract: Functional recovery of injured peripheral neurons often remains incomplete, but the clinical outcome can be improved by increasing the axonal growth rate. Adult transgenic GSK3α(S/A)/β(S/A) knock-in mice with sustained GSK3 activity show markedly accelerated sciatic nerve regeneration. Here, we unraveled the molecular mechanism underlying this phenomenon, which led to a novel pharmacological approach for the promotion of functional recovery after nerve injury.In vitroandin vivoanalysis of GSK3 single knock-in mice revealed the unexpected contribution of GSK3α in addition to GSK3β, as both GSK3(S/A) knock-ins improved axon regeneration. Moreover, growth stimulation depended on overall GSK3 activity, correlating with increased phosphorylation of microtubule-associated protein 1B and reduced microtubule detyrosination in axonal tips. Pharmacological inhibition of detyrosination by parthenolide or cnicin mimicked this axon growth promotion in wild-type animals, although it had no effect in GSK3α(S/A)/β(S/A) mice. These results support the conclusion that sustained GSK3 activity primarily targets microtubules in growing axons, maintaining them in a more dynamic state to facilitate growth. Accordingly, further manipulation of microtubule stability using either paclitaxel or nocodazole compromised the effects of parthenolide. Strikingly, either local or systemic application of parthenolide in wild-type mice dose-dependently acceleratedin vivoaxon regeneration and functional recovery similar to GSK3α(S/A)/β(S/A) mice. Thus, reducing microtubule detyrosination in axonal tips may be a novel, clinically suitable strategy to treat nerve damage.
  
  
  CONCLUSIONS
  Peripheral nerve regeneration often remains incomplete, due to an insufficient growth rate of injured axons. Transgenic mice with sustained GSK3 activity showed markedly accelerated nerve regeneration upon injury. Here, we identified the molecular mechanism underlying this phenomenon and provide a novel therapeutic principle for promoting nerve repair. Analysis of transgenic mice revealed a dependence on overall GSK3 activity and reduction of microtubule detyrosination in axonal tips. Pharmacological inhibition of detyrosination by parthenolide fully mimicked this axon growth promotion in wild-type mice. Strikingly, local or systemic treatment with parthenolidein vivomarkedly accelerated axon regeneration and functional recovery. Thus, pharmacological inhibition of microtubule detyrosination may be a novel, clinically suitable strategy for nerve repair with potential relevance for human patients.
authors.affiliation: Division of Experimental Neurology, Department of Neurology, Medical Faculty, Heinrich Heine University of Düsseldorf, 40225 Düsseldorf, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Gobrecht
authors.affiliation: Division of Experimental Neurology, Department of Neurology, Medical Faculty, Heinrich Heine University of Düsseldorf, 40225 Düsseldorf, Germany.
authors.forename: Anastasia
authors.initials: A
authors.lastname: Andreadaki
authors.affiliation: Division of Experimental Neurology, Department of Neurology, Medical Faculty, Heinrich Heine University of Düsseldorf, 40225 Düsseldorf, Germany.
authors.forename: Heike
authors.initials: H
authors.lastname: Diekmann
authors.affiliation: Division of Experimental Neurology, Department of Neurology, Medical Faculty, Heinrich Heine University of Düsseldorf, 40225 Düsseldorf, Germany.
authors.forename: Annemarie
authors.initials: A
authors.lastname: Heskamp
authors.affiliation: Division of Experimental Neurology, Department of Neurology, Medical Faculty, Heinrich Heine University of Düsseldorf, 40225 Düsseldorf, Germany.
authors.forename: Marco
authors.initials: M
authors.lastname: Leibinger
authors.affiliation: Division of Experimental Neurology, Department of Neurology, Medical Faculty, Heinrich Heine University of Düsseldorf, 40225 Düsseldorf, Germany dietmar.fischer@uni-duesseldorf.de.
authors.forename: Dietmar
authors.initials: D
authors.lastname: Fischer
mesh_terms: D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D001369:Axons / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D055879:Gene Knock-In Techniques; D038362:Glycogen Synthase Kinase 3 / Q000235:genetics; D000071679:Glycogen Synthase Kinase 3 beta; D051379:Mice; D008810:Mice, Inbred C57BL; D008870:Microtubules / Q000187:drug effects* / Q000378:metabolism*; D009416:Nerve Regeneration / Q000187:drug effects*; D015739:Nocodazole / Q000494:pharmacology; D017239:Paclitaxel / Q000494:pharmacology; D010525:Peripheral Nerves / Q000187:drug effects / Q000254:growth & development; D010766:Phosphorylation; D012584:Sciatic Nerve / Q000473:pathology; D012717:Sesquiterpenes / Q000494:pharmacology; D014443:Tyrosine / Q000378:metabolism*
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D000972:Antineoplastic Agents, Phytogenic; D012717:Sesquiterpenes; C002669:parthenolide; D014443:Tyrosine; C012849:cnicin; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; D038362:Glycogen Synthase Kinase 3; C448021:glycogen synthase kinase 3 alpha; D017239:Paclitaxel; D015739:Nocodazole
keywords: DRG neuron; GSK3; PNS; axon regeneration; microtubules; therapy