title: Regulation of protein tyrosine kinase signaling by substrate degradation during brain development.
abstract: Disabled-1 (Dab1) is a cytoplasmic adaptor protein that regulates neuronal migrations during mammalian brain development. Dab1 function in vivo depends on tyrosine phosphorylation, which is stimulated by extracellular Reelin and requires Src family kinases. Reelin signaling also negatively regulates Dab1 protein levels in vivo, and reduced Dab1 levels may be part of the mechanism that regulates neuronal migration. We have made use of mouse embryo cortical neuron cultures in which Reelin induces Dab1 tyrosine phosphorylation and Src family kinase activation. We have found that Dab1 is normally stable, but in response to Reelin it becomes polyubiquitinated and degraded via the proteasome pathway. We have established that tyrosine phosphorylation of Dab1 is required for its degradation. Dab1 molecules lacking phosphotyrosine are not degraded in neurons in which the Dab1 degradation pathway is active. The requirements for Reelin-induced degradation of Dab1 in vitro correctly predict Dab1 protein levels in vivo in different mutant mice. We also provide evidence that Dab1 serine/threonine phosphorylation may be important for Dab1 tyrosine phosphorylation. Our data provide the first evidence for how Reelin down-regulates Dab1 protein expression in vivo. Dab1 degradation may be important for ensuring a transient Reelin response and may play a role in normal brain development.
authors.affiliation: Division of Basic Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue N., Seattle, WA 98109, USA.
authors.forename: Lionel
authors.initials: L
authors.lastname: Arnaud
authors.forename: Bryan A
authors.initials: BA
authors.lastname: Ballif
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Cooper
mesh_terms: D000818:Animals; D001921:Brain / Q000196:embryology* / Q000378:metabolism*; D015816:Cell Adhesion Molecules, Neuronal / Q000378:metabolism / Q000494:pharmacology; D002478:Cells, Cultured; D003546:Cysteine Endopeptidases / Q000378:metabolism; D004789:Enzyme Activation; D016326:Extracellular Matrix Proteins / Q000378:metabolism / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D008959:Models, Neurological; D009097:Multienzyme Complexes / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D000091042:Reelin Protein; D012697:Serine Endopeptidases; D015398:Signal Transduction; D013379:Substrate Specificity; D014443:Tyrosine / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism; D019061:src-Family Kinases / Q000378:metabolism
chemical_list: D015816:Cell Adhesion Molecules, Neuronal; C103773:Dab1 protein, mouse; D016326:Extracellular Matrix Proteins; D009097:Multienzyme Complexes; D009419:Nerve Tissue Proteins; D000091042:Reelin Protein; D025801:Ubiquitin; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D019061:src-Family Kinases; C000717128:Reln protein, mouse; D012697:Serine Endopeptidases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex