title: Cytoskeletal dynamics underlying collateral membrane protrusions induced by neurotrophins in cultured Xenopus embryonic neurons.
abstract: The establishment and refinement of neuronal connections depend on dynamic modification of the morphology and physiology of developing axons in response to extrinsic factors. In embryonic cultures of Xenopus spinal neurons, acute application of brain-derived neurotrophic factor (BDNF) induced rapid collateral protrusion of filopodium-like microspikes and lamellipodia along the neurite processes, leading to a morphologic alternation of the neuron. Both types of membrane protrusions contained high concentrations of actin filaments and depended on the polymerization of the actin cytoskeleton. Immunofluorescent staining, however, revealed the presence of microtubules (MTs) in lamellipodia induced by BDNF. These MTs appeared to have arisen from debundling of MTs in the neurite shaft at the protrusion sites, splaying and extending in the rapidly protruding lamellipodia. Inhibition of microtubule polymerization by nocodazole largely abolished the formation of lamellipodia but not of microspikes. Taken together, our results suggest that collateral sprouting of microspikes and lamellipodia involve distinctly different cytoskeletal mechanisms. Although the actin cytoskeleton is solely responsible for microspike formation, cooperative efforts by microtubules and actin filaments are essential for lamellipodial protrusion in response to extrinsic factors.
authors.affiliation: Department of Neuroscience and Cell Biology, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, 675 Hoes Lane, Piscataway, New Jersey 08854, USA.
authors.forename: Jean
authors.initials: J
authors.lastname: Gibney
authors.forename: James Q
authors.initials: JQ
authors.lastname: Zheng
mesh_terms: D008841:Actin Cytoskeleton / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D019208:Brain-Derived Neurotrophic Factor / Q000494:pharmacology; D022081:Cell Surface Extensions / Q000187:drug effects* / Q000502:physiology; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000187:drug effects* / Q000502:physiology; D004625:Embryo, Nonmammalian / Q000187:drug effects / Q000502:physiology; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism; D008954:Models, Biological; D009414:Nerve Growth Factors / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D011554:Pseudopodia / Q000187:drug effects / Q000502:physiology; D013997:Time Factors; D014981:Xenopus / Q000196:embryology
chemical_list: D019208:Brain-Derived Neurotrophic Factor; D009414:Nerve Growth Factors