Both the phosphoinositide and receptor binding activities of Dab1 are required for Reelin-stimulated Dab1 tyrosine phosphorylation.
Reelin-stimulated tyrosine phosphorylation of the Dab1 adaptor protein is required during brain development for Reelin-dependent neuron positioning in the cerebral cortex and various other laminated regions. Dab1 contains an amino-terminal PTB/PI domain through which it can bind to Reelin receptors and membrane phosphoinositides. The relative contributions of these binding activities were unknown. Here, we identify a mutation in the PTB domain of Dab1 that inhibits membrane localization without inhibiting receptor binding. In neurons, this mutation reduces both basal and Reelin-stimulated Dab1 tyrosine phosphorylation. In contrast, a mutation that inhibits receptor binding reduces Reelin-stimulated but not basal tyrosine phosphorylation. These results support a model in which phospholipids recruit Dab1 to membranes but do not play a direct role in relaying the Reelin signal, while direct Dab1-receptor interaction is responsible for relaying the Reelin signal but not for membrane recruitment.
Xu
Mei
M
Division of Basic Sciences, Fred Hutchinson Cancer Research Center (FHCRC), 1100 Fairview Avenue North, Seattle, WA 98109, USA.
Arnaud
Lionel
L
Cooper
Jonathan A
JA
D000818:Animals; D015153:Blotting, Western / Q000379:methods; D015816:Cell Adhesion Molecules, Neuronal / Q000494:pharmacology*; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology; D004622:Embryo, Mammalian; D004847:Epithelial Cells; D016326:Extracellular Matrix Proteins / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects*; D049452:Green Fluorescent Proteins / Q000096:biosynthesis; D006801:Humans; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D016296:Mutagenesis / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000378:metabolism* / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects*; D010716:Phosphatidylinositols / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding / Q000187:drug effects / Q000502:physiology; D011956:Receptors, Cell Surface / Q000378:metabolism*; D000091042:Reelin Protein; D012697:Serine Endopeptidases / Q000494:pharmacology*; D014162:Transfection / Q000379:methods; D014443:Tyrosine / Q000378:metabolism*
D015816:Cell Adhesion Molecules, Neuronal; C103773:Dab1 protein, mouse; D016326:Extracellular Matrix Proteins; D008869:Microtubule-Associated Proteins; C079240:Mtap2 protein, mouse; D009419:Nerve Tissue Proteins; D010716:Phosphatidylinositols; D011956:Receptors, Cell Surface; D000091042:Reelin Protein; C469363:reelin receptor; D049452:Green Fluorescent Proteins; D014443:Tyrosine; C000717127:RELN protein, human; C000717128:Reln protein, mouse; D012697:Serine Endopeptidases