title: Outgrowth of neurites from NIE-115 neuroblastoma cells is prevented on repulsive substrates through the action of PAK.
abstract: In the central nervous system (CNS), damaged axons are inhibited from regeneration by glial scars, where secreted chondroitin sulfate proteoglycan (CSPG) and tenascin repulse outgrowth of neurites, the forerunners of axons and dendrites. During differentiation, these molecules are thought to form boundaries for guiding neurons to their correct targets. In neuroblastoma NIE-115 cells, outgrowth of neurites on laminin could be induced by serum starvation or inhibition of RhoA by Clostridium botulinum C3 toxin. The outgrowing neurites avoided crossing onto the repulsive substrate CSPG or tenascin. This avoidance response was partially overcome on expression of membrane-targeted and kinase-inactive forms of PAK. In these cells, the endogenous PAK isoforms colocalized with actin in distinctive sites, alphaPAK in the cell center as small clusters and along the neurite shaft and betaPAK and gammaPAK in areas with membrane ruffles and filopodia, respectively. When isoform-specific N-terminal PAK sequences were introduced to interfere with PAK function, substantially more neurites crossed onto CSPG when cells contained a gammaPAK-derived peptide but not the corresponding alphaPAK- or betaPAK-derived peptide. Thus, while neurite outgrowth can be promoted by RhoA inhibition, overcoming the accompanying repulsive guidance response will require modulation of PAK activity. These results have therapeutic implications for CNS repair processes.
authors.affiliation: Department of Molecular Neuroscience, Institute of Neurology, University College London, 1 Wakefield St., London WC1N 1PJ, United Kingdom.
authors.forename: Katharine J M
authors.initials: KJ
authors.lastname: Marler
authors.forename: Robert
authors.initials: R
authors.lastname: Kozma
authors.forename: Sohail
authors.initials: S
authors.lastname: Ahmed
authors.forename: Jing-Ming
authors.initials: JM
authors.lastname: Dong
authors.forename: Christine
authors.initials: C
authors.lastname: Hall
authors.forename: Louis
authors.initials: L
authors.lastname: Lim
mesh_terms: D036002:ADP Ribose Transferases / Q000378:metabolism; D000199:Actins / Q000378:metabolism; D000818:Animals; D001905:Botulinum Toxins / Q000378:metabolism; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000502:physiology*; D048430:Cell Shape; D047908:Intracellular Signaling Peptides and Proteins; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism*; D007797:Laminin / Q000378:metabolism; D051379:Mice; D016501:Neurites / Q000378:metabolism* / Q000648:ultrastructure*; D009447:Neuroblastoma; D010455:Peptides / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D013499:Surface Properties; D019063:Tenascin / Q000378:metabolism; D013997:Time Factors; D054462:p21-Activated Kinases; D020830:rac1 GTP-Binding Protein / Q000378:metabolism; D054460:rho-Associated Kinases; D020742:rhoA GTP-Binding Protein / Q000235:genetics / Q000378:metabolism
chemical_list: D000199:Actins; D047908:Intracellular Signaling Peptides and Proteins; D007527:Isoenzymes; D007797:Laminin; D010455:Peptides; D019063:Tenascin; D036002:ADP Ribose Transferases; C063007:exoenzyme C3, Clostridium botulinum; D017346:Protein Serine-Threonine Kinases; D054462:p21-Activated Kinases; D054460:rho-Associated Kinases; D001905:Botulinum Toxins; D020830:rac1 GTP-Binding Protein; D020742:rhoA GTP-Binding Protein