title: Modulation of Reelin signaling by Cyclin-dependent kinase 5.
abstract: The Reelin signaling and Cyclin-dependent kinase 5 (Cdk5) both regulate neuronal positioning in the developing brain. Using double-transgenic mice, we have previously shown that these two signaling pathways lie in parallel fashion and have a genetic interaction. Disabled-1 (Dab1), an adapter protein, mediates Reelin signaling and becomes tyrosine-phosphorylated on the binding of Reelin to its receptors. Several isoforms of Dab1 are expressed in embryonic mouse brain, and p80 [Dab1(555)] is the major protein translated. In the present study, we investigated whether Cdk5-mediated phosphorylation of Dab1 modulates Reelin signaling. Cdk5 phosphorylates p80 Dab1 at multiple sites in its carboxyl-terminal region, and tyrosine phosphorylation of p80 Dab1 by Fyn tyrosine kinase is attenuated by this Cdk5-mediated phosphorylation in vitro. Tyrosine phosphorylation of p80 Dab1 induced by exogenous Reelin is enhanced in Cdk5-deficient neurons, corroborating the inhibitory effect of Cdk5-mediated Ser/Thr phosphorylation on tyrosine phosphorylation of p80 Dab1. Another isoform, p45 Dab1 [Dab1(271)], however, is phosphorylated by Cdk5 at one serine residue within a unique carboxyl-terminal region, and its serine phosphorylation enhances tyrosine phosphorylation by Fyn and results in progressive degradation of p45 Dab1. These results indicate that Cdk5 modulates Reelin signaling through the Ser/Thr phosphorylation of Dab1 differently in an isoform-specific manner.
authors.affiliation: Laboratory for Developmental Neurobiology, Brain Science Institute, RIKEN, Wako, Saitama, Japan. ohshima@brain.riken.go.jp
authors.forename: Toshio
authors.initials: T
authors.lastname: Ohshima
authors.forename: Hiromi
authors.initials: H
authors.lastname: Suzuki
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Morimura
authors.forename: Masaharu
authors.initials: M
authors.lastname: Ogawa
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Mikoshiba
mesh_terms: D000818:Animals; D015816:Cell Adhesion Molecules, Neuronal / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology; D002522:Chlorocebus aethiops; D051360:Cyclin-Dependent Kinase 5 / Q000235:genetics / Q000502:physiology*; D004622:Embryo, Mammalian; D016326:Extracellular Matrix Proteins / Q000235:genetics / Q000378:metabolism*; D005260:Female; D006801:Humans; D047468:Immunoprecipitation / Q000379:methods; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008970:Molecular Weight; D016296:Mutagenesis / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism; D010766:Phosphorylation; D000091042:Reelin Protein; D012694:Serine / Q000378:metabolism; D012697:Serine Endopeptidases / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D013912:Threonine / Q000378:metabolism; D014162:Transfection
chemical_list: D015816:Cell Adhesion Molecules, Neuronal; C103773:Dab1 protein, mouse; D016326:Extracellular Matrix Proteins; D009419:Nerve Tissue Proteins; D000091042:Reelin Protein; D013912:Threonine; D012694:Serine; D051360:Cyclin-Dependent Kinase 5; C000717127:RELN protein, human; C000717128:Reln protein, mouse; D012697:Serine Endopeptidases