title: Mammalian target of rapamycin (mTOR) activation increases axonal growth capacity of injured peripheral nerves.
abstract: Unlike neurons in the central nervous system (CNS), injured neurons in the peripheral nervous system (PNS) can regenerate their axons and reinnervate their targets. However, functional recovery in the PNS often remains suboptimal, especially in cases of severe damage. The lack of regenerative ability of CNS neurons has been linked to down-regulation of the mTOR (mammalian target of rapamycin) pathway. We report here that PNS dorsal root ganglial neurons (DRGs) activate mTOR following damage and that this activity enhances axonal growth capacity. Furthermore, genetic up-regulation of mTOR activity by deletion of tuberous sclerosis complex 2 (TSC2) in DRGs is sufficient to enhance axonal growth capacity in vitro and in vivo. We further show that mTOR activity is linked to the expression of GAP-43, a crucial component of axonal outgrowth. However, although TSC2 deletion in DRGs facilitates axonal regrowth, it leads to defects in target innervation. Thus, whereas manipulation of mTOR activity could provide new strategies to stimulate nerve regeneration in the PNS, fine control of mTOR activity is required for proper target innervation.
authors.affiliation: Department of Anatomy and Neurobiology, Washington University in St. Louis, School of Medicine, St. Louis, Missouri 63110, USA.
authors.forename: Namiko
authors.initials: N
authors.lastname: Abe
authors.forename: Steven H
authors.initials: SH
authors.lastname: Borson
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Gambello
authors.forename: Fan
authors.initials: F
authors.lastname: Wang
authors.forename: Valeria
authors.initials: V
authors.lastname: Cavalli
mesh_terms: D000818:Animals; D001369:Axons / Q000378:metabolism*; D005260:Female; D019922:GAP-43 Protein / Q000378:metabolism; D005727:Ganglia, Spinal / Q000378:metabolism / Q000473:pathology; D017353:Gene Deletion; D005786:Gene Expression Regulation; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D051379:Mice; D059348:Peripheral Nerve Injuries; D010525:Peripheral Nerves / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D020127:Recovery of Function; D012038:Regeneration; D058570:TOR Serine-Threonine Kinases; D000077005:Tuberous Sclerosis Complex 2 Protein; D025521:Tumor Suppressor Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism
chemical_list: D019922:GAP-43 Protein; D047908:Intracellular Signaling Peptides and Proteins; C000624653:TSC2 protein, human; C000624654:Tsc2 protein, mouse; D000077005:Tuberous Sclerosis Complex 2 Protein; D025521:Tumor Suppressor Proteins; C546842:MTOR protein, human; C546843:mTOR protein, mouse; D017346:Protein Serine-Threonine Kinases; D058570:TOR Serine-Threonine Kinases