title: Regulation of neurotrophin-induced axonal responses via Rho GTPases.
abstract: Nerve growth factor (NGF) and related neurotrophins induce differential axon growth patterns from embryonic sensory neurons (Lentz et al. [1999] J. Neurosci. 19:1038-1048; Ulupinar et al. [2000a] J. Comp. Neurol 425:622-630). In wholemount explant cultures of embryonic rat trigeminal ganglion and brainstem or in dissociated cell cultures of the trigeminal ganglion, exogenous supply of NGF leads to axonal elongation, whereas neurotrophin-3 (NT-3) treatment leads to short branching and arborization (Ulupinar et al. [2000a] J. Comp. Neurol. 425:622-630). Axonal responses to neurotrophins might be mediated via the Rho GTPases. To investigate this possibility, we prepared wholemount trigeminal pathway cultures from E15 rats. We infected the ganglia with recombinant vaccinia viruses that express GFP-tagged dominant negative Rac, Rho, or constitutively active Rac or treated the cultures with lysophosphatitic acid (LPA) to activate Rho. We then examined axonal responses to NGF by use of the lipophilic tracer DiI. Rac activity induced longer axonal growth from the central trigeminal tract, whereas the dominant negative construct of Rac eliminated NGF-induced axon outgrowth. Rho activity also significantly reduced, and the Rho dominant negative construct increased, axon growth from the trigeminal tract. Similar alterations in axonal responses to NT-3 and brain-derived neurotrophic factor were also noted. Our results demonstrate that Rho GTPases play a major role in neurotrophin-induced axonal differentiation of embryonic trigeminal axons.
authors.affiliation: Department of Cell Biology and Anatomy, LSUHSC, New Orleans, Louisiana 70112, USA.
authors.forename: P H
authors.initials: PH
authors.lastname: Ozdinler
authors.forename: R S
authors.initials: RS
authors.lastname: Erzurumlu
mesh_terms: D000344:Afferent Pathways / Q000187:drug effects / Q000196:embryology / Q000201:enzymology; D000818:Animals; D019208:Brain-Derived Neurotrophic Factor / Q000378:metabolism / Q000494:pharmacology; D002232:Carbocyanines / Q000493:pharmacokinetics; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D048429:Cell Size / Q000187:drug effects / Q000502:physiology; D005333:Fetus; D005456:Fluorescent Dyes / Q000494:pharmacology; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects / Q000502:physiology; D005822:Genetic Vectors / Q000502:physiology*; D020439:Growth Cones / Q000187:drug effects / Q000201:enzymology / Q000648:ultrastructure*; D007150:Immunohistochemistry; D008246:Lysophospholipids / Q000494:pharmacology; D020932:Nerve Growth Factor / Q000378:metabolism / Q000494:pharmacology; D009414:Nerve Growth Factors / Q000378:metabolism / Q000494:pharmacology*; D009475:Neurons, Afferent / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology; D020933:Neurotrophin 3 / Q000378:metabolism / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D014162:Transfection; D012668:Trigeminal Ganglion / Q000187:drug effects / Q000196:embryology* / Q000201:enzymology; D014278:Trigeminal Nuclei / Q000187:drug effects / Q000196:embryology / Q000201:enzymology; D014616:Vaccinia virus / Q000235:genetics; D020744:rac GTP-Binding Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*
chemical_list: C035005:3,3'-dihexadecylindocarbocyanine; D019208:Brain-Derived Neurotrophic Factor; D002232:Carbocyanines; D005456:Fluorescent Dyes; D008246:Lysophospholipids; D009414:Nerve Growth Factors; D020933:Neurotrophin 3; D020932:Nerve Growth Factor; D020744:rac GTP-Binding Proteins; D020741:rho GTP-Binding Proteins