title: Nerve growth factor stimulates axon outgrowth through negative regulation of growth cone actomyosin restraint of microtubule advance.
abstract: Nerve growth factor (NGF) promotes growth, differentiation, and survival of sensory neurons in the mammalian nervous system. Little is known about how NGF elicits faster axon outgrowth or how growth cones integrate and transform signal input to motor output. Using cultured mouse dorsal root ganglion neurons, we found that myosin II (MII) is required for NGF to stimulate faster axon outgrowth. From experiments inducing loss or gain of function of MII, specific MII isoforms, and vinculin-dependent adhesion-cytoskeletal coupling, we determined that NGF causes decreased vinculin-dependent actomyosin restraint of microtubule advance. Inhibition of MII blocked NGF stimulation, indicating the central role of restraint in directed outgrowth. The restraint consists of myosin IIB- and IIA-dependent processes: retrograde actin network flow and transverse actin bundling, respectively. The processes differentially contribute on laminin-1 and fibronectin due to selective actin tethering to adhesions. On laminin-1, NGF induced greater vinculin-dependent adhesion-cytoskeletal coupling, which slowed retrograde actin network flow (i.e., it regulated the molecular clutch). On fibronectin, NGF caused inactivation of myosin IIA, which negatively regulated actin bundling. On both substrates, the result was the same: NGF-induced weakening of MII-dependent restraint led to dynamic microtubules entering the actin-rich periphery more frequently, giving rise to faster elongation.
authors.affiliation: Center for Brain Science and Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138.
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Turney
authors.affiliation: Department of Neuroscience, Washington University School of Medicine, St. Louis, MO 63110.
authors.forename: Mostafa
authors.initials: M
authors.lastname: Ahmed
authors.affiliation: Department of Neuroscience, Washington University School of Medicine, St. Louis, MO 63110.
authors.forename: Indra
authors.initials: I
authors.lastname: Chandrasekar
authors.affiliation: Department of Neurobiology and Anatomy, West Virginia University School of Medicine, Morgantown, WV 26506.
authors.forename: Robert B
authors.initials: RB
authors.lastname: Wysolmerski
authors.affiliation: Department of Neurobiology and Anatomy, West Virginia University School of Medicine, Morgantown, WV 26506.
authors.forename: Zoe M
authors.initials: ZM
authors.lastname: Goeckeler
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138.
authors.forename: Robert M
authors.initials: RM
authors.lastname: Rioux
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138.
authors.forename: George M
authors.initials: GM
authors.lastname: Whitesides
authors.affiliation: Department of Neuroscience, Washington University School of Medicine, St. Louis, MO 63110 bridgmap@pcg.wustl.edu.
authors.forename: Paul C
authors.initials: PC
authors.lastname: Bridgman
mesh_terms: D000205:Actomyosin / Q000378:metabolism*; D000818:Animals; D049108:Cell Enlargement; D005260:Female; D005353:Fibronectins / Q000502:physiology; D005727:Ganglia, Spinal / Q000166:cytology; D020439:Growth Cones / Q000502:physiology*; D007797:Laminin / Q000502:physiology; D008297:Male; D018345:Mice, Knockout; D008870:Microtubules / Q000378:metabolism*; D020932:Nerve Growth Factor / Q000502:physiology*; D024507:Nonmuscle Myosin Type IIA / Q000378:metabolism; D024501:Nonmuscle Myosin Type IIB / Q000378:metabolism; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D046509:Tissue Culture Techniques; D020741:rho GTP-Binding Proteins / Q000378:metabolism; D020742:rhoA GTP-Binding Protein
chemical_list: D005353:Fibronectins; D007797:Laminin; D000205:Actomyosin; D020932:Nerve Growth Factor; D024507:Nonmuscle Myosin Type IIA; D024501:Nonmuscle Myosin Type IIB; C526380:RhoA protein, mouse; D020741:rho GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein