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The Pafah1b complex interacts with the Reelin receptor VLDLR

The Cain Foundation Laboratories, Texas Children's Hospital, Houston, Texas, United States of America.
PLoS ONE (Impact Factor: 3.23). 02/2007; 2(2):e252. DOI: 10.1371/journal.pone.0000252
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ABSTRACT Reelin is an extracellular protein that directs the organization of cortical structures of the brain through the activation of two receptors, the very low-density lipoprotein receptor (VLDLR) and the apolipoprotein E receptor 2 (ApoER2), and the phosphorylation of Disabled-1 (Dab1). Lis1, the product of the Pafah1b1 gene, is a component of the brain platelet-activating factor acetylhydrolase 1b (Pafah1b) complex, and binds to phosphorylated Dab1 in response to Reelin. Here we investigated the involvement of the whole Pafah1b complex in Reelin signaling and cortical layer formation and found that catalytic subunits of the Pafah1b complex, Pafah1b2 and Pafah1b3, specifically bind to the NPxYL sequence of VLDLR, but not to ApoER2. Compound Pafah1b1(+/-);Apoer2(-/-) mutant mice exhibit a reeler-like phenotype in the forebrain consisting of the inversion of cortical layers and hippocampal disorganization, whereas double Pafah1b1(+/-);Vldlr(-/-) mutants do not. These results suggest that a cross-talk between the Pafah1b complex and Reelin occurs downstream of the VLDLR receptor.

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    • "Reelin induces binding of Lis1, encoded by the Pafah1b1 gene, to Dab1, an essential component of the reelin signaling cascade. The Pafah1b complex interacts with the reelin receptor VLDLR, and compound mutant mice deficient for Pafah1b1 and apoER2 exhibit a reeler like phenotype (Zhang et al. 2007). Migrating interneurons in Lis ± mice exhibit reduced leading process stability and reduced a-tubulin acetylation in leading processes (Gopal et al. 2010). "
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    ABSTRACT: The extracellular matrix protein reelin controls radial migration and layer formation of cortical neurons, in part by modulation of cytoskeletal dynamics. A stabilizing effect of reelin on the actin cytoskeleton has been described recently. However, it is poorly understood how reelin modulates microtubule dynamics. Here, we provide evidence that reelin increases microtubule assembly. This effect is mediated, at least in part, by promoting microtubule plus end dynamics in processes of developing neurons. Thus, we treated primary neuronal cultures with nocodazole to disrupt microtubules. After nocodazole washout, we found microtubule reassembly to be accelerated in the presence of reelin. Moreover, we show that reelin treatment promoted the formation of microtubule plus end binding protein 3 (EB3) comets in developing dendrites, and that EB3 immunostaining in the developing wild-type neocortex is most intense in the reelin-rich marginal zone where leading processes of radially migrating neurons project to. This characteristic EB3 staining pattern was absent in reeler. Also reassembly of nocodazole-dispersed dendritic Golgi apparati, which are closely associated to microtubules, was accelerated by reelin treatment, though with a substantially slower time course when compared to microtubule reassembly. In support of our in vitro results, we found that the subcellular distribution of α-tubulin and acetylated tubulin in reeler cortical sections differed from wild-type and from mice lacking the very low density lipoprotein receptor (VLDLR), known to bind reelin. Taken together, our results suggest that reelin promotes microtubule assembly, at least in part, by increasing microtubule plus end dynamics.
    Histochemie 09/2012; 139(2). DOI:10.1007/s00418-012-1025-1 · 2.93 Impact Factor
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    • "Reelin was induced by TsA in the CgCx of rats taking cocaine, indicating that reelin protein was regulated in an opposite way by TsA between cortex and NAc. Reelin is known to enhance synaptic plasticity by binding to its constituent receptors coupled to the intracellular signaling machinery that involves the protein Dab1 controlling Lis1, PI3K, Crk, N-WASP and Nckb proteins (Zhang et al. 2007). Interestingly, among the genes regulated by TsA in the microarray experiment, we also found Nck1 and the phosphatidylinositol 3-kinase PIK3CA genes. "
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    ABSTRACT: Injection of the histone deacetylase inhibitor trichostatin A (TsA) to rats has been shown to decrease their motivation to self-administer cocaine. In the present study, we investigated alterations in gene expression patterns in the anterior cingulate cortex and nucleus accumbens of rats self-administering cocaine and treated with TsA. Using oligonucleotide microarrays, we identified 722 probe sets in the cortex and 136 probe sets in the nucleus accumbens that were differentially expressed between vehicle and TsA-treated rats that self-administered cocaine. Microarray data were validated by real-time PCR for seven genes. Using immunohistochemistry, we further investigated the expression of Lis1 and reelin genes, because (i) they were similarly regulated by TsA at the mRNA level; (ii) they belong to the same signal transduction pathway; (iii) mutations within both genes cause lissencephaly. Cocaine self-injection was sufficient to activate the two genes at both the mRNA and protein levels. TsA treatment was found to up-regulate both Lis1 and reelin protein expression in the cortex and to down-regulate it in the nucleus accumbens of rats self-administering cocaine. The data suggest that the two proteins contribute to establish neurobiological mechanisms underlying brain plasticity whereby TsA lowers the motivation for cocaine.
    Journal of Neurochemistry 04/2010; 113(1):236-47. DOI:10.1111/j.1471-4159.2010.06591.x · 4.24 Impact Factor
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    • "In vitro translations of Pafah1b1, Pafah1b2, VLDLR and Dab1 cDNAs were performed using the TnT Quick Couple Transcription/Translation System (Promega), according to the manufacturer instructions using 35 S-labeled methionine. Antibodies were added for immunoprecipitation (IP) for 1–2 hours at 4°C followed by addition of protein A/G agarose beads (Pierce) as described previously (Zhang et al., 2007). Beads were washed three times with PBS. "
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    ABSTRACT: 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.
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