title: Nerve growth factor and semaphorin 3A signaling pathways interact in regulating sensory neuronal growth cone motility.
abstract: Neurotrophins and semaphorin 3A are present along pathways and in targets of developing axons of dorsal root ganglion (DRG) sensory neurons. Growth cones of sensory axons are probably regulated by interaction of cytoplasmic signaling triggered coincidentally by both types of guidance molecules. We investigated the in vitro interactions of neurotrophins and semaphorin 3A (Sema3A) in modulating growth cone behaviors of axons extended from DRGs of embryonic day 7 chick embryos. Growth cones of DRGs raised in media containing 10(-9) m NGF or BDNF were more resistant to Sema3A-induced growth cone collapse than when DRGs were raised in 10(-11) m NGF. After overnight culture in 10(-11) m NGF, a 1 hr treatment with 10(-9) m NGF or BDNF was sufficient to increase growth cone resistance to Sema3A-induced collapse. This neurotrophin-mediated decrease in the collapse response of DRG growth cones was not associated with reduced expression on growth cones of the Sema3A-binding protein neuropilin-1. A series of pharmacological studies followed. Phosphatidylinositol 3 kinase activity is not required for these effects of NGF. The effects of inhibitors and activators of protein kinase A (PKA) indicate that PKA activity is involved in NGF modulation of Sema3A-induced growth cone collapse. The effects of inhibitors and activators of PKG indicate that PKG activity is involved in Sema3A-induced growth cone collapse. The effects of inhibitors also indicate that Rho-kinase activity is involved in Sema3A-induced growth cone collapse. These results are consistent with the idea that growth cone responses to an individual guidance cue depend on coincident signaling by other guidance cues and by other regulatory pathways.
authors.affiliation: Department of Anatomy and Histology, Medical University-Sofia, Sofia, 1431 Bulgaria.
authors.forename: Vassil D
authors.initials: VD
authors.lastname: Dontchev
authors.forename: Paul C
authors.initials: PC
authors.lastname: Letourneau
mesh_terms: D000818:Animals; D019208:Brain-Derived Neurotrophic Factor / Q000494:pharmacology; D002478:Cells, Cultured; D002642:Chick Embryo; D017868:Cyclic AMP-Dependent Protein Kinases / Q000187:drug effects / Q000378:metabolism; D017869:Cyclic GMP-Dependent Protein Kinases / Q000187:drug effects / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D020536:Enzyme Activators / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005727:Ganglia, Spinal / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D006023:Glycoproteins / Q000378:metabolism* / Q000494:pharmacology; D020439:Growth Cones / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D007668:Kidney / Q000166:cytology / Q000378:metabolism; D020932:Nerve Growth Factor / Q000378:metabolism* / Q000494:pharmacology; D009419:Nerve Tissue Proteins / Q000096:biosynthesis; D009475:Neurons, Afferent / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D039942:Neuropilin-1; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases / Q000187:drug effects / Q000378:metabolism; D015290:Second Messenger Systems / Q000502:physiology; D040121:Semaphorin-3A; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D054460:rho-Associated Kinases
chemical_list: D019208:Brain-Derived Neurotrophic Factor; D017868:Cyclic AMP-Dependent Protein Kinases; D017869:Cyclic GMP-Dependent Protein Kinases; D020536:Enzyme Activators; D004791:Enzyme Inhibitors; D006023:Glycoproteins; D047908:Intracellular Signaling Peptides and Proteins; D020932:Nerve Growth Factor; D009419:Nerve Tissue Proteins; D039942:Neuropilin-1; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D040121:Semaphorin-3A; D054460:rho-Associated Kinases