121 research outputs found
mRNPs, polysomes or granules: FMRP in neuronal protein synthesis
No full textmRNA localization and regulated translation play central roles in neurite outgrowth and synaptic plasticity. A key molecule in these processes is the Fragile X mental retardation protein, FMRP, which is involved in the metabolism of neuronal mRNAs. Absence or mutation of FMRP leads to spine dysmorphogenesis and impairs synaptic plasticity. Studies that have mainly been performed on the mouse and Drosophila models for Fragile X Syndrome showed that FMRP is involved in translational regulation at synapses, but even 15 years after discovery of the FMR1 gene, the precise working mechanisms remain elusive.status: Publishe
Molecular dynamics simulations show how the FMRP Ile304Asn mutation destabilizes the KH2 domain structure and affects its function
No full textMutations or deletions of FMRP, involved in the regulation of mRNA metabolism in brain, lead to the Fragile X syndrome (FXS), the most frequent form of inherited intellectual disability. A severe manifestation of the disease has been associated with the Ile304Asn mutation, located on the KH2 domain of the protein. Several hypotheses have been proposed to explain the possible molecular mechanism responsible for the drastic effect of this mutation in humans. Here, we performed a molecular dynamics simulation and show that the Ile304Asn mutation destabilizes the hydrophobic core producing a partial unfolding of two α-helices and a displacement of a third one. The affected regions show increased residue flexibility and motion. Molecular docking analysis revealed strongly reduced binding to a model single-stranded nucleic acid in agreement with known data that the two partially unfolded helices form the RNA-binding surface. The third helix, which we show here to be also affected, is involved in the PAK1 protein interaction. These two functional binding sites on the KH2 domain do not overlap spatially, and therefore, they can simultaneously bind their targets. Since the Ile304Asn mutation affects both binding sites, this may justify the severe clinical manifestation observed in the patient in which both mRNA metabolism activity and cytoskeleton remodeling would be affected
MD and Docking Studies Reveal That the Functional Switch of CYFIP1 is Mediated by a Butterfly-like Motion
No full textCytoplasmic FMRP
interacting protein 1 (CYFIP1), also known as
specifically RAC1 activated protein 1 (Sra1), plays a dual role: together
with fragile X mental retardation protein (FMRP) and eIF4E it forms
a complex that inhibits mRNA translation, while together with WAVE1,
NCKAP1, ABI2, and HSPC300 it forms the WAVE regulatory complex (WRC)
that upon RAC1 activation initiates actin polymerization. Here we
performed a molecular dynamics (MD) simulation on CYFIP1 extracted
from the known WRC structure, which shows that, in the absence of
its WRC partners, a butterfly-like motion brings the two ends of CYFIP1
closer together, enabling the interaction with eIF4E. Our MD simulation
is supported by available data showing that binding of CYFIP1 to eIF4E
and binding to the WRC are mutually exclusive and that there is fluorescence
resonance energy transfer between the N- and C-termini of CYFIP1.
The differential interaction of RAC1–GTP with the two CYFIP1
structures predicts that RAC1 is directly responsible for the switch
between these conformations
The intriguing case of motor neuron disease: ALS and SMA come closer
No full textMNDs (motor neuron diseases) form a heterogeneous group of pathologies characterized by the progressive degeneration of motor neurons. More and more genetic factors associated with MND encode proteins that have a function in RNA metabolism, suggesting that disturbed RNA metabolism could be a common underlying problem in several, perhaps all, forms of MND. In the present paper we review recent developments showing a functional link between SMN (survival of motor neuron), the causative factor of SMA (spinal muscular atrophy), and FUS (fused in sarcoma), a genetic factor in ALS (amyotrophic lateral sclerosis). SMN is long known to have a crucial role in the biogenesis and localization of the spliceosomal snRNPs (small nuclear ribonucleoproteins), which are essential assembly modules of the splicing machinery. Now we know that FUS interacts with SMN and pathogenic FUS mutations have a significant effect on snRNP localization. Together with other recently published evidence, this finding potentially links ALS pathogenesis to disturbances in the splicing machinery, and implies that pre-mRNA splicing may be the common weak point in MND, although other steps in mRNA metabolism could also play a role. Certainly, further comparison of the RNA metabolism in different MND will greatly help our understanding of the molecular causes of these devastating diseases
Cancer drug repurposing in autism spectrum disorder
No full textautism spectrum disorder (ASD) is a complex neurodevelopmental condition with uncertain origins. Understanding of the mechanisms underlying ASD re-mains limited, and treatments are lacking. genetic diversity complicates drug development. given the complexity and severity of ASD symptoms and the rising number of diagnoses, exploring novel therapeutic strategies is essential. here, we focus on shared molecular pathways between ASD and cancer and highlight recent progress on the repurposing of cancer drugs for ASD treatment, such as mTOR inhibitors, histone deacetylase inhibitors, and anti-inflammatory agents. we discuss how to improve trial design considering drug dose and patient age. lastly, the discussion explores the critical aspects of side effects, commercial factors, and the efficiency of drug-screening pipelines; all of which are essential considerations in the pursuit of repurposing cancer drugs for addressing core features of ASD
Modelling Learning and Memory in <i>Drosophila</i> to Understand Intellectual Disabilities
No full textNeurodevelopmental disorders (NDDs) include a large number of conditions such as Fragile X syndrome, autism spectrum disorders and Down syndrome, among others. They are characterized by limitations in adaptive and social behaviors, as well as intellectual disability (ID). Whole-exome and whole-genome sequencing studies have highlighted a large number of NDD/ID risk genes. To dissect the genetic causes and underlying biological pathways, in vivo experimental validation of the effects of these mutations is needed. The fruit fly, Drosophila melanogaster, is an ideal model to study NDDs, with highly tractable genetics, combined with simple behavioral and circuit assays, permitting rapid medium-throughput screening of NDD/ID risk genes. Here, we review studies where the use of well-established assays to study mechanisms of learning and memory in Drosophila has permitted insights into molecular mechanisms underlying IDs. We discuss how technologies in the fly model, combined with a high degree of molecular and physiological conservation between flies and mammals, highlight the Drosophila system as an ideal model to study neurodevelopmental disorders, from genetics to behavior.sponsorship: We apologize to our colleagues whose work could not be included due to limited space. This work was supported by KU Leuven Funds Opening the Future (Belgium), SNSF NCCR Synapsy 51NF40-158776, SNSF 310030182651 (Switzerland), Novartis Foundation for Medical Biological Researchand Canton Etat de Vaud (Switzerland), Fondazione Roma Terzo Pilastro Internazionale and Associazione Italiana Sindrome X Fragile to CB. AKK was a recipient of the Autism Speaks Meixner Translational Postdoctoral Fellowship (USA) and supported by the Autism Research Institute (USA) and the Fondation Sophie Afenduli (Switzerland). We acknowledge the Flybase for essential information and constant support of the fly community. We are grateful to Annick Crevoisier for administrative support and to Kris Dickson for suggestions and manuscript proofreading. We thank Gaia Tavosanis, Eleonora Rosina, Nuria Dominguez-Iturza and Adrian Lo for critical reading of the manuscript. (KU Leuven Funds Opening the Future (Belgium), SNSF NCCR Synapsy|51NF40-158776, SNSF (Switzerland)|310030182651, Novartis Foundation for Medical Biological Researchand Canton Etat de Vaud (Switzerland), Fondazione Roma Terzo Pilastro Internazionale, Associazione Italiana Sindrome X Fragile, Autism Speaks Meixner Translational Postdoctoral Fellowship (USA), Autism Research Institute (USA), Fondation Sophie Afenduli (Switzerland))status: Publishe
Pat1b en LSm14 PROTEINS: regulateurs van neuronale mRNA metabolisme met mogelijke rol bij spinale musculaire atrofie
No full textThe central nervous system isprobably the most complex structure present in the human body. Such complexityis also a drawback since the central nervous system may be affected by severaldiseases, many of which are extremely complex and difficult to understand. Onefeature that many neurological diseases have in common is some perturbation inthe metabolism of neuronal messenger RNA. Despite all the studies and the progress that has been achieved in thisfield, the exact relation between dysfunction of mRNA metabolism andneurological disease remains elusive. In fact, for many severe diseases stillno precise molecular pathway has been identified.In particular motor neurons seem to beextremely vulnerable to perturbations of their mRNA metabolism as shown by thefact that mutations in genes encoding RNA-binding proteins can cause devastatingdiseases like Amyotrophic Lateral Sclerosis and Spinal Muscular Atrophy. SpinalMuscular Atrophy in particular is caused by shortage of the Survival of MotorNeuron protein, which is fundamental for pre-mRNA splicing by affecting thematuration of the Sm proteins, the major players of splicing. Despite the factthat the function of SMN is well known, nobody could so far provide a directexplanation for the pathogenesis of SMA. The Like-Sm protein 1 (LSm1), a memberof the Like-Sm protein family which is structurally related to the Sm proteinfamily, has been demonstrated to play an important role in neuronal mRNA processing.Considering the similarities between LSm proteins and Sm proteins, a potentialrole for SMN in the metabolism of LSm proteins can be hypothesized. A lack ofSMN, as observed in SMA, could lead to misfunction of the mRNA processescarried by LSm1 or other members of the family. The aim of the work of mythesis is to investigate a potential role of LSm proteins and proteinsassociated with them in neuronal mRNA metabolism and eventually, look for apossible role in the pathogenesis of SMA. We identified in mammalian cells aninteractor of LSm1, Pat1b, known to be involved in mRNA turnover in yeast. As apartner of LSm1, Pat1b could be necessary for its action or for specific mRNAtarget recognition. In the first part of this work we studied the role of Pat1bin mammalian cells and in neuronal mRNA metabolism. We found that Pat1b affectsmRNA turnover through deadenylation of the target. Plus, we observed that inmammalian cells Pat1b does not generally act on mRNA molecules but insteadaffects specific transcripts. However, when we extended our analysis toneurons, we observed a prevalent nuclear localization of the protein,suggesting that in neurons Pat1b has evolved a different function. This study beingfocused on mRNA metabolism (cytoplasmic event), we decided to look at otherpotential players of neuronal mRNA and SMA. We studied two members of the Like-Smfamily that share structural features with LSm1 and LSm4 which make themcandidates as SMN partners. We show that LSm14a and LSm14b can represstranslation of mRNA and affect its stability and that they bind specific mRNAsin neurons that are involved in cytoskeleton remodelling and axonal growth. Inagreement with these findings, knock-down of LSm14b in primary neurons causedan axonal phenotype. At last, we extended our analysis of LSm14 proteins to SMAand found that a SMA mouse model has dramatically reduced levels of both proteinssuggesting a link between the proteins and the disease. This work sheds lighton the function and importance of three different proteins in neuronal mRNAmetabolism, and increases our knowledge of neuronal molecular physiology.status: Publishe
The fragile X mental retardation protein-RNP granules show an mGluR-dependent localization in the post-synaptic spines
No full textThe localization of RNA/mRNA in dendrites plays a role in both local and temporal regulation of protein synthesis, which is required for certain forms of synaptic plasticity. A key molecule in these processes is the fragile X mental retardation protein (FMRP). Using in situ hybridization coupled to immunofluorescence confocal microscopy, we find that the FMRP-RNP particle contains ceCaMKII and BC1 RNAs as well as Staufen and CPEB proteins. Furthermore, following mGluR activation, the FMRP-mRNP complex moves into spines as shown by co-localization with the PSD-95 and Shank proteins. This study shows, for the first time, that the translationally inactive FMRP-mRNP complex relocates into neuronal spines after stimulation and that de novo protein synthesis mainly contributes to the pool of FMRP at synapses. (c) 2006 Elsevier Inc. All rights reserved
Factors involved in the activation of pre-mRNA splicing from downstream splicing enhancers
No full textThe excision of introns with weak polypyrimidine tracts at their 3 ' splice sites can be enhanced by sequence elements in the downstream exon or by a downstream 5 ' splice site. The enhancers inside the exon do not conform to a strict consensus, but they are generally rich in purines. Here, we show that members of the family of SR proteins recognize these elements. Not only does SF2/ASF activate many different polypurine enhancers, but also at least one other SR protein, most likely SC35, is active as well. The degree of splicing activation varies with the polypurine enhancers and the SR proteins. Further, we show that the similar activation by downstream 5 ' splice sites requires Ul snRNP, which is not the case with purine-rich enhancers. These results are consistent with a model showing that Ul snRNP binds to the 5 ' splice site and SR proteins to exonic sequences upstream of the 5' splice site. Both interact with U2AF at the 3 ' splice site. This represents a molecular explanation for the exon recognition which is important for splice site selection in mammals. Key words: exonic enhancer, pre-mRNA splicing, SR proteins, transacting factors, Ul snRNP
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