title: Structural determinants of Trk receptor specificities using BDNF-based neurotrophin chimeras.
abstract: Neurotrophins play very important roles in the development and maintenance of the vertebrate nervous system. In mammals, there are four members of the family: NGF, BDNF, NT-3 and NT-4/5. Members of the neurotrophin family activate different receptors that belong to a class of receptor tyrosine kinases known as "Trks." For example, NGF is the specific ligand of TrkA, while BDNF activates TrkB. To elucidate which regions of the two neurotrophins determine the receptor specificities, chimeric neurotrophins were constructed using BDNF as the backbone, with various regions being substituted by the corresponding regions of NGF. The activity of the chimeras on the Trk receptors was assayed in transfected fibroblasts ectopically expressing the Trk receptors. Our findings revealed that, although BDNF is absolutely conserved in mammals, substitution of several small variable regions from NGF into the BDNF backbone did not lead to significant loss in TrkB activity or gain in TrkA activity. Moreover, important determinants of TrkB activation might be located in the carboxy-terminal half of BDNF. On the other hand, critical elements for TrkA activation might be located within the amino-terminal half of the mature NGF molecule.
authors.affiliation: Department of Biology, Hong Kong University of Science and Technology, Clear Water Bay.
authors.forename: K O
authors.initials: KO
authors.lastname: Lai
authors.forename: D J
authors.initials: DJ
authors.lastname: Glass
authors.forename: D
authors.initials: D
authors.lastname: Geis
authors.forename: G D
authors.initials: GD
authors.lastname: Yancopoulos
authors.forename: N Y
authors.initials: NY
authors.lastname: Ip
mesh_terms: D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D019208:Brain-Derived Neurotrophic Factor / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019556:COS Cells; D002470:Cell Survival; D018076:DNA, Complementary / Q000235:genetics; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D009414:Nerve Growth Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D020801:Receptor, Ciliary Neurotrophic Factor; D020917:Receptor, trkA; D017475:Receptors, Nerve Growth Factor / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism*; D016415:Sequence Alignment; D013329:Structure-Activity Relationship; D014162:Transfection
chemical_list: D019208:Brain-Derived Neurotrophic Factor; D018076:DNA, Complementary; D008565:Membrane Proteins; D009414:Nerve Growth Factors; D011518:Proto-Oncogene Proteins; D020801:Receptor, Ciliary Neurotrophic Factor; D017475:Receptors, Nerve Growth Factor; D011993:Recombinant Fusion Proteins; D020794:Receptor Protein-Tyrosine Kinases; D020917:Receptor, trkA