title: TACE-induced cleavage of NgR and p75NTR in dorsal root ganglion cultures disinhibits outgrowth and promotes branching of neurites in the presence of inhibitory CNS myelin.
abstract: After binding, central nervous system (CNS) myelin-derived axon growth inhibitory ligands, the Nogo-66 receptor (NgR), complexes with LINGO-1 and either the low-affinity neurotrophin receptor (p75(NTR)) or TROY to initiate growth cone collapse via a Rho-A inhibitory signaling pathway and/or Ca(2+)-dependent activation of epidermal growth factor receptor (EGFR) through an unknown signaling pathway. We have shown that axon growth through CNS myelin is disinhibited after neurotrophic factor administration by 1) initiating intramembranous proteolysis (RIP) of p75(NTR), leading to cleavage of the extracellular (p75(ECD)) and intracellular domains (p75(ICD)) by alpha- and gamma-secretase, respectively, thereby paralyzing inhibitory signaling; 2) shedding of soluble NgR(ECD), which acts as a competitive antagonist to NgR for binding of inhibitory ligands; and 3) antagonizing NgR/p75(NTR) clustering by competitive p75(ECD)/NgR interaction. Here, we report that TNF-alpha converting enzyme (TACE) (a disintegrin and metalloproteinase 17, ADAM17) induces disinhibition of FGF2-stimulated neurite outgrowth of dorsal root ganglion neurons (DRGN) cultured in the presence of a predetermined concentration of inhibitory CNS myelin-derived ligands. After addition of TACE (which has alpha-secretase activity) to mitotically arrested adult rat mixed DRG cultures, we demonstrate 1) NgR(ECD) shedding; 2) release of p75(ECD) and p75(ICD) by RIP of p75(NTR); 3) blockade of Rho-A activation; 4) reduced EGFR phosphorylation; and 5) increased FGF2-stimulated DRGN neurite outgrowth and branching in the presence of CNS myelin-derived inhibitory ligands. Thus, TACE-induced cleavage of NgR and RIP of p75(NTR) abrogates axon growth inhibitory signaling, thereby disinhibiting CNS axon/neurite growth.
authors.affiliation: Molecular Neuroscience Group, Division of Medical Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
authors.forename: Zubair
authors.initials: Z
authors.lastname: Ahmed
authors.forename: Gordon
authors.initials: G
authors.lastname: Mazibrada
authors.forename: Ruth J
authors.initials: RJ
authors.lastname: Seabright
authors.forename: Russell G
authors.initials: RG
authors.lastname: Dent
authors.forename: Martin
authors.initials: M
authors.lastname: Berry
authors.forename: Ann
authors.initials: A
authors.lastname: Logan
mesh_terms: D051722:ADAM Proteins / Q000378:metabolism* / Q000494:pharmacology; D000072198:ADAM17 Protein; D000818:Animals; D002478:Cells, Cultured; D002490:Central Nervous System / Q000502:physiology; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology; D058851:GPI-Linked Proteins; D005727:Ganglia, Spinal / Q000166:cytology / Q000502:physiology*; D007150:Immunohistochemistry; D009185:Myelin Proteins / Q000494:pharmacology* / Q000502:physiology; D016501:Neurites / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D000070816:Nogo Receptor 1; D051381:Rats; D017207:Rats, Sprague-Dawley; D020800:Receptor, Nerve Growth Factor / Q000502:physiology*; D011956:Receptors, Cell Surface / Q000502:physiology*
chemical_list: D058851:GPI-Linked Proteins; D009185:Myelin Proteins; D000070816:Nogo Receptor 1; D020800:Receptor, Nerve Growth Factor; D011956:Receptors, Cell Surface; C486581:Rtn4r protein, rat; D016222:Fibroblast Growth Factor 2; D051722:ADAM Proteins; D000072198:ADAM17 Protein; C000606464:Adam17 protein, rat