Differential interaction of the Pafah1b alpha subunits with the Reelin transducer Dab1.
The Reelin signaling pathway controls radial neuronal migration and maturation in the developing brain. The platelet activating factor (PAF) acetyl hydrolase 1b (Pafah1b) complex is also involved in multiple aspects of brain development. We previously showed that the Reelin pathway and the Pafah1b complex interact genetically and biochemically. Lis1, the regulatory subunit of Pafah1b interacts with phosphoDab1, an essential mediator of Reelin signaling. Compound mutants carrying mutations in both, the Reelin pathway and Lis1 exhibit hydrocephalus, a phenotype that is suppressed by mutations in the gene encoding the Alpha2 subunit of Pafah1b. This subunit, like the Alpha1 catalytic subunit of Pafah1b also binds the Reelin receptor VLDLR. Here we investigated the molecular interactions of the Pafah1b catalytic subunits with Dab1. We found that Alpha2 coprecipitates with Dab1 from brain extracts of normal and reeler mutant mice lacking Reelin, and from cell-free extracts containing normal or a phosphorylation mutant form of Dab1, suggesting that Dab1 phosphorylation is not necessary for binding to Alpha2. This interaction is specific for Alpha2 and not Alpha1, and depends on a unique tyrosine residue of Alpha2. Biochemical assays using mutant mice lacking Alpha2 further demonstrated that this subunit is not required for Reelin-induced Dab1 phosphorylation. However, increasing amounts of Alpha2 in a cell-free system disrupted the formation of Dab1-Lis1 complexes without affecting the association of Dab1 with VLDLR. Our data suggest that the Alpha2 subunit may play a modulatory role in the formation of protein complexes that affect brain development and hydrocephalus.
Zhang
Guangcheng
G
The Cain Foundation Laboratories, Texas Children's Hospital, Houston, TX 77030, USA.
Assadi
Amir H
AH
Roceri
Mila
M
Clark
Gary D
GD
D'Arcangelo
Gabriella
G
D043203:1-Alkyl-2-acetylglycerophosphocholine Esterase / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D015153:Blotting, Western; D001921:Brain / Q000378:metabolism*; D019556:COS Cells; D015816:Cell Adhesion Molecules, Neuronal / Q000235:genetics / Q000378:metabolism; D002540:Cerebral Cortex / Q000378:metabolism; D002522:Chlorocebus aethiops; D016326:Extracellular Matrix Proteins / Q000235:genetics / Q000378:metabolism; D047468:Immunoprecipitation; D051379:Mice; D008822:Mice, Transgenic; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D011973:Receptors, LDL / Q000378:metabolism; D000091042:Reelin Protein; D012697:Serine Endopeptidases / Q000235:genetics / Q000378:metabolism
D015816:Cell Adhesion Molecules, Neuronal; C103773:Dab1 protein, mouse; D016326:Extracellular Matrix Proteins; D008869:Microtubule-Associated Proteins; D009419:Nerve Tissue Proteins; D011973:Receptors, LDL; D000091042:Reelin Protein; C036053:VLDL receptor; D043203:1-Alkyl-2-acetylglycerophosphocholine Esterase; C513190:Pafah1b1 protein, mouse; C000717128:Reln protein, mouse; D012697:Serine Endopeptidases