title: Activation of ADF/cofilin mediates attractive growth cone turning toward nerve growth factor and netrin-1.
abstract: Proper neural circuitry requires that growth cones, motile tips of extending axons, respond to molecular guidance cues expressed in the developing organism. However, it is unclear how guidance cues modify the cytoskeleton to guide growth cone pathfinding. Here, we show acute treatment with two attractive guidance cues, nerve growth factor (NGF) and netrin-1, for embryonic dorsal root ganglion and temporal retinal neurons, respectively, results in increased growth cone membrane protrusion, actin polymerization, and filamentous actin (F-actin). ADF/cofilin (AC) family proteins facilitate F-actin dynamics, and we found the inactive phosphorylated form of AC is decreased in NGF- or netrin-1-treated growth cones. Directly increasing AC activity mimics addition of NGF or netrin-1 to increase growth cone protrusion and F-actin levels. Extracellular gradients of NGF, netrin-1, and a cell-permeable AC elicit attractive growth cone turning and increased F-actin barbed ends, F-actin accumulation, and active AC in growth cone regions proximal to the gradient source. Reducing AC activity blunts turning responses to NGF and netrin. Our results suggest that gradients of NGF and netrin-1 locally activate AC to promote actin polymerization and subsequent growth cone turning toward the side containing higher AC activity.
authors.affiliation: Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota 55455, USA.
authors.forename: Bonnie M
authors.initials: BM
authors.lastname: Marsick
authors.forename: Kevin C
authors.initials: KC
authors.lastname: Flynn
authors.forename: Miguel
authors.initials: M
authors.lastname: Santiago-Medina
authors.forename: James R
authors.initials: JR
authors.lastname: Bamburg
authors.forename: Paul C
authors.initials: PC
authors.lastname: Letourneau
mesh_terms: D051339:Actin Depolymerizing Factors / Q000378:metabolism*; D000199:Actins / Q000378:metabolism; D029845:Amphibian Proteins / Q000378:metabolism; D000818:Animals; D030161:Avian Proteins / Q000378:metabolism; D002462:Cell Membrane / Q000502:physiology; D002465:Cell Movement / Q000502:physiology; D002478:Cells, Cultured; D002633:Chemotaxis / Q000502:physiology*; D002642:Chick Embryo; D005110:Extracellular Space / Q000378:metabolism; D005727:Ganglia, Spinal / Q000196:embryology / Q000502:physiology; D020439:Growth Cones / Q000502:physiology*; D066298:In Vitro Techniques; D020932:Nerve Growth Factor / Q000378:metabolism*; D009414:Nerve Growth Factors / Q000378:metabolism*; D000075388:Netrin-1; D009474:Neurons / Q000502:physiology*; D010766:Phosphorylation; D055503:Protein Multimerization; D055351:Retinal Neurons / Q000502:physiology; D013116:Spinal Cord / Q000196:embryology / Q000502:physiology; D025521:Tumor Suppressor Proteins / Q000378:metabolism*; D014982:Xenopus laevis
chemical_list: D051339:Actin Depolymerizing Factors; D000199:Actins; D029845:Amphibian Proteins; D030161:Avian Proteins; D009414:Nerve Growth Factors; D025521:Tumor Suppressor Proteins; D000075388:Netrin-1; D020932:Nerve Growth Factor