Papers by Daniel Larocque
Mutant quaking viable mice (qkV) develop a tremor phenotype in their hind limbs 10 days after bir... more Mutant quaking viable mice (qkV) develop a tremor phenotype in their hind limbs 10 days after birth, likely resulting from severe myelination defects. Genetically, quaking viable mice contain a deletion in the promoter/enhancer region of the quaking gene. The quaking gene is alternatively spliced, producing QUAKING isoforms that differ in their C-terminal amino acid sequence. The QKI-5 isoform is nuclear, whereas the QKI-6 and QKI-7 isoforms are predominantly cytoplasmic. The QKI isoforms contain a single KH RNA-binding domain, which suggests a role in RNA metabolism. Although the dysmyelinating phenotype of the mutant mice suggests a role in myelination, the function of the protein remains largely unknown. The objective of this thesis is to characterize the role of the RNA binding proteins QKI in the differentiation of glial cells and their involvement in the process of myelination. Moreover, this study describes the quaking viable defects and how the isoforms contribute to the obs...
Gene Therapy for Neurological Disorders, 2006
RNA Biology, 2005
The quaking viable (qk v ) mice have attracted attention because of their characteristic tremor c... more The quaking viable (qk v ) mice have attracted attention because of their characteristic tremor caused by their dysmyelination. In the central nervous system, qk v mice fail to develop mature myelinating oligodendrocytes and display uncompacted myelin. The genetic defect in the qk v mice prevents the proper expression of alternatively spliced KH-type QKI RNA binding proteins. Thus qk v mice provide a unique animal model linking RNA binding proteins to defects in oligodendrocyte cell fate and myelination. The fact that QKI proteins are modified post-translationally makes them Signal Transduction Activiators of RNA (STAR) proteins. We have used a gain-of-function approach with the ectopic expression of the separate QKI isoforms using adenoviruses and retroviruses to determine their separate roles in cell fate and myelination. Herein, we discuss the recent advances in characterizing the QKI KH-type proteins as glial cell fate and myelin regulators.
PLoS ONE, 2011
The INhibitor of Growth tumor suppressors (ING1-ING5) affect aging, apoptosis, DNA repair and tum... more The INhibitor of Growth tumor suppressors (ING1-ING5) affect aging, apoptosis, DNA repair and tumorigenesis. Plant homeodomains (PHD) of ING proteins bind histones in a methylation-sensitive manner to regulate chromatin structure. ING1 and ING2 contain a polybasic region (PBR) adjacent to their PHDs that binds stress-inducible phosphatidylinositol monophosphate (PtIn-MP) signaling lipids to activate these INGs. ING1 induces apoptosis independently of p53 but other studies suggest proapoptotic interdependence of ING1 and p53 leaving their functional relationship unclear. Here we identify a novel ubiquitin-binding domain (UBD) that overlaps with the PBR of ING1 and shows similarity to previously described UBDs involved in DNA damage responses. The ING1 UBD binds ubiquitin with high affinity (K d ,100 nM) and ubiquitin competes with PtIn-MPs for ING1 binding. ING1 expression stabilized wild-type, but not mutant p53 in an MDM2independent manner and knockdown of endogenous ING1 depressed p53 levels in a transcription-independent manner. ING1 stabilized unmodified and six multimonoubiquitinated forms of wild-type p53 that were also seen upon DNA damage, but not p53 mutants lacking the six known sites of ubiquitination. We also find that ING1 physically interacts with herpesvirus-associated ubiquitin-specific protease (HAUSP), a p53 and MDM2 deubiquitinase (DUB), and knockdown of HAUSP blocks the ability of ING1 to stabilize p53. These data link lipid stress signaling to ubiquitin-mediated proteasomal degradation through the PBR/UBD of ING1 and further indicate that ING1 stabilizes p53 by inhibiting polyubiquitination of multimonoubiquitinated forms via interaction with and colocalization of the HAUSP-deubiquitinase with p53.
Journal of Biological Chemistry, 2005
The breast tumor kinase (BRK) is a growth promoting non-receptor tyrosine kinase overexpressed in... more The breast tumor kinase (BRK) is a growth promoting non-receptor tyrosine kinase overexpressed in the majority of human breast tumors. BRK is known to potentiate the epidermal growth factor (EGF) response in these cells. Although BRK is known to phosphorylate the RNA-binding protein Sam68, the specific tyrosines phosphorylated and the exact role of this phosphorylation remains unknown. Herein, we have generated Sam68 phospho-specific antibodies against C-terminal phosphorylated tyrosine residues within the Sam68 nuclear localization signal. We show that BRK phosphorylates Sam68 on all three tyrosines in the nuclear localization signal. By indirect immunofluorescence we observed that BRK and EGF treatment not only phosphorylates Sam68 but also induces its relocalization. Tyrosine 440 was identified as a principal modulator of Sam68 localization and this site was phosphorylated in response to EGF treatment in human breast tumor cell lines. Moreover, this phosphorylation event was inhibited by BRK small interfering RNA treatment, consistent with Sam68 being a physiological substrate of BRK downstream of the EGF receptor in breast cancer cells. Finally, we observed that Sam68 suppressed BRK-induced cell proliferation, suggesting that Sam68 does indeed contain anti-proliferative properties that may be neutralized in breast cancer cells by phosphorylation. . 5 The abbreviations used are: BRK, breast tumor kinase; SH, Src homology domain; ERK, extracellular signal-regulated kinase; EGF, epidermal growth factor; siRNA, small interfering RNA; SNB, Sam68 nuclear bodies; NLS, nuclear localization signal; ELISA, enzyme-linked immunosorbent assay; PBS, phosphate-buffered saline; GFP, green fluorescent protein; BrdUrd, bromodeoxyuridine; PTP1B, protein-tyrosine phosphatase 1B; IDC, infiltrating ductal carcinomas; mSNB, multiple Sam68 nuclear bodies.
Genes & Development, 2001
The quaking viable mice have myelination defects and develop a characteristic tremor 10 d after b... more The quaking viable mice have myelination defects and develop a characteristic tremor 10 d after birth. The quaking gene encodes at least five alternatively spliced QUAKING (QKI) isoforms that differ in their C-terminal 8-30-amino-acid sequence. The reason for the existence of the different QKI isoforms and their function are unknown. Here we show that only one QKI isoform, QKI-7, can induce apoptosis in fibroblasts and primary rat oligodendrocytes. Heterodimerization of the QKI isoforms results in the nuclear translocation of QKI-7 and the suppression of apoptosis. The unique C-terminal 14 amino acids of QKI-7 confers the ability to induce apoptosis to heterologous proteins such as the green fluorescent protein and a QKI-related protein, Caenorhabditis elegans GLD-1. Thus, the unique C-terminal sequences of QKI-7 may function as a life-or-death 'sensor' that monitors the balance between the alternatively spliced QKI isoforms. Moreover, our findings suggest that nuclear translocation is a novel mechanism of inactivating apoptotic inducers.
Clinical and Developmental Immunology, 2013
Handbook of Neurochemistry and Molecular Neurobiology, 2008
ABSTRACT Researchers have conducted numerous pre‐clinical and clinical gene transfer studies usin... more ABSTRACT Researchers have conducted numerous pre‐clinical and clinical gene transfer studies using recombinant viral vectors modified from a wide range of pathogenic viruses such as adenovirus, adeno‐associated virus, herpes simplex 1 virus, and lentivurus. Herein, we examine the utility of each vector system to treat disorders of the nervous system as well as offer a summary of various strategies and clinical outcomes of gene therapy approaches to treat neurological disorders such as Parkinson's disease, Alzheimer's disease, and glioma. As viral vectors are derived from pathogenic viruses, they have an inherit ability to induce a vector specific immune response. The role of the immune response against the viral vector gene delivery vehicle has been implicated in the inconsistent and unpredictable translation of pre‐clinical success into therapeutic efficacy in human clinical trials using gene therapy to treat neurological disorders. The effects of the innate and adaptive immune responses on therapeutic gene expression mediated by viral vectors are discussed. Furthermore, the immune responses against gene therapy vectors and the resulting loss of therapeutic gene expression are examined in the context of the architecture and neuroanatomy of the brain immune system.
Neuron, May 12, 2002
Quaking viable (qk(v)) mice fail to properly compact myelin in their central nervous systems. Alt... more Quaking viable (qk(v)) mice fail to properly compact myelin in their central nervous systems. Although the defect in the qk(v) mice involves a mutation affecting the expression of the alternatively spliced qk gene products, their roles in myelination are unknown. We show that the QKI RNA binding proteins regulate the nuclear export of MBP mRNAs. Disruption of the QKI nucleocytoplasmic equilibrium in oligodendrocytes results in nuclear and perikaryal retention of the MBP mRNAs and lack of export to cytoplasmic processes, as it occurs in qk(v) mice. MBP mRNA export defect leads to a reduction in the MBP levels and their improper cellular targeting to the periphery. Our findings suggest that QKI participates in myelination by regulating the mRNA export of key protein components.
The Faseb Journal, Mar 1, 2008
The Faseb Journal, Mar 1, 2008
La maladie d'Alzheimer (MA) est une maladie neurodégénérative caractérisée par l'accumula... more La maladie d'Alzheimer (MA) est une maladie neurodégénérative caractérisée par l'accumulation extracellulaire du peptide β-amyloïde (Aβ), formant des dépôts dans le parenchyme et la vasculature du système nerveux central (SNC). Des études ont suggéré que cette accumulation serait associée à un défaut dans le processus d'élimination de l'Aβ. Il n'y a présentement aucun traitement curatif de la maladie. Il a été proposé que la barrière hémato-encéphalique (BHE) jouerait un rôle crucial dans l'élimination des peptides d'Aβ, et conséquemment sur la réduction des dépôts dans le cerveau. ABCB1 est un transporteur de type « ATP-binding cassette » (ABC) exprimé du côté luminal de l'endothélium cérébral, qui contribue à l'élimination des éléments toxiques. Chez la souris APP/PS1, un modèle murin de la MA, le traitement chronique avec un dérivé détoxifié du Lipopolysaccharide (LPS), le Monophosphoryl Lipid A (MPL), a démontré une réduction des dépôts d'...
Journal of Immunological Methods, 2015
Antibody-mediated capture of amyloid-beta (Aβ) in peripheral blood was identified as an attractiv... more Antibody-mediated capture of amyloid-beta (Aβ) in peripheral blood was identified as an attractive strategy to eliminate cerebral toxic amyloid in Alzheimer's disease (AD) patients and murine models. Alternatively, defective capacity of peripheral monocytes to engulf Aβ was reported in individuals with AD. In this report, we developed different approaches to investigate cellular uptake and phagocytosis of Aβ, and to examine how two immunological devices - an immunostimulatory Adjuvant System and different amyloid specific antibodies - may affect these biological events. Between one and thirteen months of age, APPswe X PS1.M146V (TASTPM) AD model mice had decreasing concentrations of Aβ in their plasma. In contrast, the proportion of blood monocytes containing Aβ tended to increase with age. Importantly, the TLR-agonist containing Adjuvant System AS01B primed monocytes to promote de novo Aβ uptake capacity, particularly in the presence of anti-Aβ antibodies. Biochemical experiments demonstrated that cells achieved Aβ uptake and internalization followed by Aβ degradation via mechanisms that required effective actin polymerization and proteolytic enzymes such as insulin-degrading enzyme. We further demonstrated that both Aβ-specific monoclonal antibodies and plasma from Aβ-immunized mice enhanced the phagocytosis of 1μm Aβ-coated particles. Together, our data highlight a new biomarker testing to follow amyloid clearance within the blood and a mechanism of Aβ uptake by peripheral monocytes in the context of active or passive immunization, and emphasize on novel approaches to investigate this phenomenon.
Uploads
Papers by Daniel Larocque