title: Glial cell line-derived neurotrophic factor and target-dependent regulation of large-conductance KCa channels in developing chick lumbar motoneurons.
abstract: The functional expression of large-conductance Ca2+-activated K+ (K(Ca)) channels in lumbar motoneurons (LMNs) of the developing chick embryo is regulated in part by interactions with striated muscle target tissues. Here we show that the functional expression of K(Ca) channels in LMNs developing in vitro can be stimulated by application of a skeletal muscle extract (MEX) or by coculture with hindlimb myotubes. A similar stimulation of K(Ca) channels in vitro can be produced by the trophic factors glial cell line-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor but not by neurotrophin (NT)-3 or NT-4. The actions of MEX and hindlimb myotubes are blocked by a GDNF-neutralizing antiserum. Moreover, injection of this same antiserum into the embryonic hindlimb reduced the functional expression of K(Ca) channels in vivo to levels seen in LMNs deprived of interactions with the hindlimb. The effects of GDNF on K(Ca) channel expression in LMNs require 24 hr of continuous exposure to reach maximum and are blocked by the translation inhibitor anisomycin, indicating the need for synthesis of new proteins. GDNF actions are also blocked by the farnesyl transferase inhibitor manumycin, suggesting a role for Ras in the actions of GDNF. Finally, the actions of GDNF are inhibited by PP2, an inhibitor of Src family tyrosine kinases, and by LY29003, an inhibitor of phosphatidylinositol 3 kinases, but not by PD98059, an inhibitor of the Erk signaling cascade. None of these treatments alter expression of voltage-activated Ca2+ channels. Thus, the actions of GDNF on LMN K(Ca) channel expression appear to use a transduction pathway similar to that used for regulation of apoptosis.
authors.affiliation: Department of Biology and Biochemistry, University of Houston, Houston, Texas 77204-5513, USA.
authors.forename: Miguel
authors.initials: M
authors.lastname: Martin-Caraballo
authors.forename: Stuart E
authors.initials: SE
authors.lastname: Dryer
mesh_terms: D000818:Animals; D019208:Brain-Derived Neurotrophic Factor / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism; D002457:Cell Extracts / Q000494:pharmacology; D002478:Cells, Cultured; D002642:Chick Embryo; D018920:Coculture Techniques; D004791:Enzyme Inhibitors / Q000494:pharmacology; D051100:Glial Cell Line-Derived Neurotrophic Factor; D006614:Hindlimb / Q000187:drug effects / Q000196:embryology / Q000378:metabolism; D007106:Immune Sera / Q000494:pharmacology; D051036:Large-Conductance Calcium-Activated Potassium Channels; D008161:Lumbosacral Region; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors; D009046:Motor Neurons / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000378:metabolism; D018482:Muscle, Skeletal / Q000737:chemistry / Q000166:cytology; D009414:Nerve Growth Factors / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D020933:Neurotrophin 3 / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D000081082:Phosphoinositide-3 Kinase Inhibitors; D024681:Potassium Channels, Calcium-Activated / Q000187:drug effects* / Q000378:metabolism*; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013116:Spinal Cord / Q000166:cytology / Q000196:embryology; D019061:src-Family Kinases / Q000037:antagonists & inhibitors
chemical_list: D019208:Brain-Derived Neurotrophic Factor; D015220:Calcium Channels; D002457:Cell Extracts; D004791:Enzyme Inhibitors; D051100:Glial Cell Line-Derived Neurotrophic Factor; D007106:Immune Sera; D051036:Large-Conductance Calcium-Activated Potassium Channels; D009414:Nerve Growth Factors; D020933:Neurotrophin 3; D000081082:Phosphoinositide-3 Kinase Inhibitors; D024681:Potassium Channels, Calcium-Activated; D011500:Protein Synthesis Inhibitors; D019061:src-Family Kinases; D020928:Mitogen-Activated Protein Kinases; C073922:neurotrophin 4