title: Truncated trkB.T1 is dominant negative inhibitor of trkB.TK+-mediated cell survival.
abstract: Truncated trkB.T1 (T1) neurotrophin receptor inhibits full-length trkB.TK+ (TK+) signaling. At least two possible mechanisms have been proposed for this action: T1 could trap the ligand or function as a dominant negative receptor. To differentiate between these possibilities we have studied survival of serum-deprived PC12-trkB cells stably expressing TK+. PC12-trkB cells were observed to display constitutive trkB kinase activity which leads to survival of a cell subpopulation in the absence of added brain-derived neurotrophic factor (BDNF) and serum. Exogenous BDNF significantly increased cell survival, and this increase was inhibited by BDNF neutralizing antibody. The antibody treatment had no effect on the constitutive TK+ activity. Transfected T1 completely inhibited survival by BDNF or constitutive trkB kinase activity in PC12-trkB cells similarly to tyrosine kinase inhibitor K252a. In addition, T1 coimmunoprecipitated with TK+ and inhibited its autophosphorylation by BDNF. These data suggest that truncated T1 inhibits TK+ signaling by dominant negative action.
authors.affiliation: A. I. Virtanen Institute for Molecular Sciences, University of Kuopio, Kuopio, 70211, Finland.
authors.forename: A
authors.initials: A
authors.lastname: Haapasalo
authors.forename: E
authors.initials: E
authors.lastname: Koponen
authors.forename: E
authors.initials: E
authors.lastname: Hoppe
authors.forename: G
authors.initials: G
authors.lastname: Wong
authors.forename: E
authors.initials: E
authors.lastname: Castrén
mesh_terms: D000818:Animals; D001665:Binding Sites / Q000235:genetics; D019208:Brain-Derived Neurotrophic Factor / Q000494:pharmacology; D002227:Carbazoles / Q000494:pharmacology; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D049452:Green Fluorescent Proteins; D026121:Indole Alkaloids; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D016716:PC12 Cells; D010766:Phosphorylation / Q000187:drug effects; D051381:Rats; D020813:Receptor, trkB / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D013997:Time Factors; D014162:Transfection
chemical_list: D019208:Brain-Derived Neurotrophic Factor; D002227:Carbazoles; D004791:Enzyme Inhibitors; D026121:Indole Alkaloids; D008164:Luminescent Proteins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; C049985:staurosporine aglycone; D020813:Receptor, trkB