1
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Lee JY, Gala DS, Kiourlappou M, Olivares-Abril J, Joha J, Titlow JS, Teodoro RO, Davis I. Murine glial protrusion transcripts predict localized Drosophila glial mRNAs involved in plasticity. J Cell Biol 2024; 223:e202306152. [PMID: 39037431 PMCID: PMC11262410 DOI: 10.1083/jcb.202306152] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 06/14/2024] [Accepted: 07/03/2024] [Indexed: 07/23/2024] Open
Abstract
The polarization of cells often involves the transport of specific mRNAs and their localized translation in distal projections. Neurons and glia are both known to contain long cytoplasmic processes, while localized transcripts have only been studied extensively in neurons, not glia, especially in intact nervous systems. Here, we predict 1,740 localized Drosophila glial transcripts by extrapolating from our meta-analysis of seven existing studies characterizing the localized transcriptomes and translatomes of synaptically associated mammalian glia. We demonstrate that the localization of mRNAs in mammalian glial projections strongly predicts the localization of their high-confidence Drosophila homologs in larval motor neuron-associated glial projections and are highly statistically enriched for genes associated with neurological diseases. We further show that some of these localized glial transcripts are specifically required in glia for structural plasticity at the nearby neuromuscular junction synapses. We conclude that peripheral glial mRNA localization is a common and conserved phenomenon and propose that it is likely to be functionally important in disease.
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Affiliation(s)
- Jeffrey Y. Lee
- School of Molecular Biosciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
- Department of Biochemistry, University of Oxford, Oxford, UK
| | - Dalia S. Gala
- Department of Biochemistry, University of Oxford, Oxford, UK
| | | | | | - Jana Joha
- Department of Biochemistry, University of Oxford, Oxford, UK
| | | | - Rita O. Teodoro
- iNOVA4Health, NOVA Medical School | Faculdade de Ciências Médicas, Universidade Nova de Lisboa, Lisboa, Portugal
| | - Ilan Davis
- School of Molecular Biosciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
- Department of Biochemistry, University of Oxford, Oxford, UK
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2
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Brandão-Teles C, Antunes ASLM, de Moraes Vrechi TA, Martins-de-Souza D. The Roles of hnRNP Family in the Brain and Brain-Related Disorders. Mol Neurobiol 2024; 61:3578-3595. [PMID: 37999871 DOI: 10.1007/s12035-023-03747-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Accepted: 10/25/2023] [Indexed: 11/25/2023]
Abstract
Heterogeneous nuclear ribonucleoproteins (hnRNPs) belong to a complex family of RNA-binding proteins that are essential to control alternative splicing, mRNA trafficking, synaptic plasticity, stress granule formation, cell cycle regulation, and axonal transport. Over the past decade, hnRNPs have been associated with different brain disorders such as Alzheimer's disease, multiple sclerosis, and schizophrenia. Given their essential role in maintaining cell function and integrity, it is not surprising that dysregulated hnRNP levels lead to neurological implications. This review aims to explore the primary functions of hnRNPs in neurons, oligodendrocytes, microglia, and astrocytes, and their roles in brain disorders. We also discuss proteomics and other technologies and their potential for studying and evaluating hnRNPs in brain disorders, including the discovery of new therapeutic targets and possible pharmacological interventions.
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Affiliation(s)
- Caroline Brandão-Teles
- Laboratory of Neuroproteomics, Department of Biochemistry and Tissue Biology, Institute of Biology, University of Campinas, Campinas, Brazil.
| | - André S L M Antunes
- Brazilian Biosciences National Laboratory (LNBio), Brazilian Center for Research in Energy and Materials (CNPEM), Campinas, Brazil
| | - Talita Aparecida de Moraes Vrechi
- Laboratory of Neuroproteomics, Department of Biochemistry and Tissue Biology, Institute of Biology, University of Campinas, Campinas, Brazil
| | - Daniel Martins-de-Souza
- Laboratory of Neuroproteomics, Department of Biochemistry and Tissue Biology, Institute of Biology, University of Campinas, Campinas, Brazil.
- D'Or Institute for Research and Education (IDOR), São Paulo, Brazil.
- Experimental Medicine Research Cluster (EMRC), University of Campinas, Campinas, SP, 13083-862, Brazil.
- INCT in Modelling Human Complex Diseases with 3D Platforms (Model3D), São Paulo, Brazil.
- Conselho Nacional de Desenvolvimento Científico e Tecnológico, Instituto Nacional de Biomarcadores em Neuropsiquiatria, São Paulo, Brazil.
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3
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Gould R, Brady S. Identifying mRNAs Residing in Myelinating Oligodendrocyte Processes as a Basis for Understanding Internode Autonomy. Life (Basel) 2023; 13:life13040945. [PMID: 37109474 PMCID: PMC10142070 DOI: 10.3390/life13040945] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2023] [Revised: 03/28/2023] [Accepted: 03/31/2023] [Indexed: 04/07/2023] Open
Abstract
In elaborating and maintaining myelin sheaths on multiple axons/segments, oligodendrocytes distribute translation of some proteins, including myelin basic protein (MBP), to sites of myelin sheath assembly, or MSAS. As mRNAs located at these sites are selectively trapped in myelin vesicles during tissue homogenization, we performed a screen to identify some of these mRNAs. To confirm locations, we used real-time quantitative polymerase chain reaction (RT-qPCR), to measure mRNA levels in myelin (M) and ‘non-myelin’ pellet (P) fractions, and found that five (LPAR1, TRP53INP2, TRAK2, TPPP, and SH3GL3) of thirteen mRNAs were highly enriched in myelin (M/P), suggesting residences in MSAS. Because expression by other cell-types will increase p-values, some MSAS mRNAs might be missed. To identify non-oligodendrocyte expression, we turned to several on-line resources. Although neurons express TRP53INP2, TRAK2 and TPPP mRNAs, these expressions did not invalidate recognitions as MSAS mRNAs. However, neuronal expression likely prevented recognition of KIF1A and MAPK8IP1 mRNAs as MSAS residents and ependymal cell expression likely prevented APOD mRNA assignment to MSAS. Complementary in situ hybridization (ISH) is recommended to confirm residences of mRNAs in MSAS. As both proteins and lipids are synthesized in MSAS, understanding myelination should not only include efforts to identify proteins synthesized in MSAS, but also the lipids.
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Affiliation(s)
- Robert Gould
- Whitman Research Center, Marine Biology Laboratory, Woods Hole, MA 02543, USA
| | - Scott Brady
- Departments of Anatomy and Cell Biology, University of Illinois at Chicago, Chicago, IL 60612, USA
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4
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Le P, Ahmed N, Yeo GW. Illuminating RNA biology through imaging. Nat Cell Biol 2022; 24:815-824. [PMID: 35697782 PMCID: PMC11132331 DOI: 10.1038/s41556-022-00933-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2021] [Accepted: 05/06/2022] [Indexed: 12/14/2022]
Abstract
RNA processing plays a central role in accurately transmitting genetic information into functional RNA and protein regulators. To fully appreciate the RNA life-cycle, tools to observe RNA with high spatial and temporal resolution are critical. Here we review recent advances in RNA imaging and highlight how they will propel the field of RNA biology. We discuss current trends in RNA imaging and their potential to elucidate unanswered questions in RNA biology.
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Affiliation(s)
- Phuong Le
- Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, CA, USA
- Stem Cell Program, University of California San Diego, La Jolla, CA, USA
- Institute for Genomic Medicine, University of California San Diego, La Jolla, CA, USA
| | - Noorsher Ahmed
- Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, CA, USA
- Stem Cell Program, University of California San Diego, La Jolla, CA, USA
- Institute for Genomic Medicine, University of California San Diego, La Jolla, CA, USA
- Biomedical Sciences Graduate Program, University of California San Diego, La Jolla, CA, USA
| | - Gene W Yeo
- Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, CA, USA.
- Stem Cell Program, University of California San Diego, La Jolla, CA, USA.
- Institute for Genomic Medicine, University of California San Diego, La Jolla, CA, USA.
- Biomedical Sciences Graduate Program, University of California San Diego, La Jolla, CA, USA.
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5
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Nihonmatsu-Kikuchi N, Yu XJ, Matsuda Y, Ozawa N, Ito T, Satou K, Kaname T, Iwasaki Y, Akagi A, Yoshida M, Toru S, Hirokawa K, Takashima A, Hasegawa M, Uchihara T, Tatebayashi Y. Essential roles of plexin-B3 + oligodendrocyte precursor cells in the pathogenesis of Alzheimer's disease. Commun Biol 2021; 4:870. [PMID: 34267322 PMCID: PMC8282672 DOI: 10.1038/s42003-021-02404-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Accepted: 06/09/2021] [Indexed: 02/06/2023] Open
Abstract
The role of oligodendrocyte lineage cells, the largest glial population in the adult central nervous system (CNS), in the pathogenesis of Alzheimer's disease (AD) remains elusive. Here, we developed a culture method for adult oligodendrocyte progenitor cells (aOPCs). Fibroblast growth factor 2 (FGF2) promotes survival and proliferation of NG2+ aOPCs in a serum-free defined medium; a subpopulation (~5%) of plexin-B3+ aOPCs was also found. FGF2 withdrawal decreased NG2+, but increased plexin-B3+ aOPCs and Aβ1-42 secretion. Plexin-B3+ aOPCs were distributed throughout the adult rat brain, although less densely than NG2+ aOPCs. Spreading depolarization induced delayed cortical plexin-B3+ aOPC gliosis in the ipsilateral remote cortex. Furthermore, extracellular Aβ1-42 accumulation was occasionally found around plexin-B3+ aOPCs near the lesions. In AD brains, virtually all cortical SPs were immunostained for plexin-B3, and plexin-B3 levels increased significantly in the Sarkosyl-soluble fractions. These findings suggest that plexin-B3+ aOPCs may play essential roles in AD pathogenesis, as natural Aβ-secreting cells.
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Affiliation(s)
- Naomi Nihonmatsu-Kikuchi
- Affective Disorders Research Project, Tokyo Metropolitan Institute of Medical Science, Setagaya, Tokyo, Japan
| | - Xiu-Jun Yu
- Affective Disorders Research Project, Tokyo Metropolitan Institute of Medical Science, Setagaya, Tokyo, Japan
- Department of Neurology, Key Laboratory of Neurology of Hebei Province, Second Hospital of Hebei Medical University, Shijiazhuang, China
| | - Yoshiki Matsuda
- Affective Disorders Research Project, Tokyo Metropolitan Institute of Medical Science, Setagaya, Tokyo, Japan
| | - Nobuyuki Ozawa
- Affective Disorders Research Project, Tokyo Metropolitan Institute of Medical Science, Setagaya, Tokyo, Japan
| | - Taeko Ito
- Affective Disorders Research Project, Tokyo Metropolitan Institute of Medical Science, Setagaya, Tokyo, Japan
| | - Kazuhito Satou
- Department of Genome Medicine, National Center for Child Health and Development, Setagaya, Tokyo, Japan
| | - Tadashi Kaname
- Department of Genome Medicine, National Center for Child Health and Development, Setagaya, Tokyo, Japan
| | - Yasushi Iwasaki
- Institute for Medical Science for Aging, Aichi Medical University, Nagakute, Aichi, Japan
| | - Akio Akagi
- Institute for Medical Science for Aging, Aichi Medical University, Nagakute, Aichi, Japan
| | - Mari Yoshida
- Institute for Medical Science for Aging, Aichi Medical University, Nagakute, Aichi, Japan
| | - Shuta Toru
- Department of Neurology, Nitobe Memorial Nakano General Hospital, Nakano, Tokyo, Japan
| | - Katsuiku Hirokawa
- Department of Neurology, Nitobe Memorial Nakano General Hospital, Nakano, Tokyo, Japan
| | - Akihiko Takashima
- Department of Life Science, Gakushuin University Graduate School of Science, Toshima, Tokyo, Japan
| | - Masato Hasegawa
- Dementia Research Project, Tokyo Metropolitan Institute of Medical Science, Setagaya, Tokyo, Japan
| | - Toshiki Uchihara
- Affective Disorders Research Project, Tokyo Metropolitan Institute of Medical Science, Setagaya, Tokyo, Japan
- Department of Neurology, Nitobe Memorial Nakano General Hospital, Nakano, Tokyo, Japan
| | - Yoshitaka Tatebayashi
- Affective Disorders Research Project, Tokyo Metropolitan Institute of Medical Science, Setagaya, Tokyo, Japan.
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6
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Colliva A, Tongiorgi E. Distinct role of 5'UTR sequences in dendritic trafficking of BDNF mRNA: additional mechanisms for the BDNF splice variants spatial code. Mol Brain 2021; 14:10. [PMID: 33436052 PMCID: PMC7805101 DOI: 10.1186/s13041-020-00680-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Accepted: 10/02/2020] [Indexed: 01/07/2023] Open
Abstract
The neurotrophin Brain-derived neurotrophic factor (BDNF) is encoded by multiple bipartite transcripts. Each BDNF transcript is composed by one out of 11 alternatively spliced exons containing the 5'untranslated region (UTR), and one common exon encompassing the coding sequence (CDS) and the 3'UTR with two variants (short and long). In neurons, BDNF mRNA variants have a distinct subcellular distribution, constituting a "spatial code", with exon 1, 3, 5, 7 and 8 located in neuronal somata, exon 4 extending into proximal dendrites, and exon 2 and 6 reaching distal dendrites. We previously showed that the CDS encodes constitutive dendritic targeting signals (DTS) and that both the 3'UTR-short and the 3'UTR-long contain activity-dependent DTS. However, the role of individual 5'UTR exons in mRNA sorting remains unclear. Here, we tested the ability of each different BDNF 5'UTRs to affect the subcellular localization of the green fluorescent protein (GFP) reporter mRNA. We found that exon 2 splicing isoforms (2a, 2b, and 2c) induced a constitutive dendritic targeting of the GFP reporter mRNA towards distal dendritic segments. The other isoforms did not affect GFP-mRNA dendritic trafficking. Through a bioinformatic analysis, we identified five unique cis-elements in exon 2a, 2b, and 2c which might contribute to building a DTS. This study provides additional information on the mechanism regulating the cellular sorting of BDNF mRNA variants.
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Affiliation(s)
- Andrea Colliva
- Department of Life Sciences (Q Building), University of Trieste, Via Licio Giorgieri, 5, 34127, Trieste, Italy
| | - Enrico Tongiorgi
- Department of Life Sciences (Q Building), University of Trieste, Via Licio Giorgieri, 5, 34127, Trieste, Italy.
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7
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Association of microtubules and axonal RNA transferred from myelinating Schwann cells in rat sciatic nerve. PLoS One 2020; 15:e0233651. [PMID: 32469980 PMCID: PMC7259579 DOI: 10.1371/journal.pone.0233651] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Accepted: 05/09/2020] [Indexed: 01/19/2023] Open
Abstract
Transference of RNAs and ribosomes from Schwann cell-to-axon was demonstrated in normal and regenerating peripheral nerves. Previously, we have shown that RNAs transfer is dependent on F-actin cytoskeleton and Myosin Va. Here, we explored the contribution of microtubules to newly synthesized RNAs transport from Schwann cell nuclei up to nodal microvilli in sciatic nerves. Results using immunohistochemistry and quantitative confocal FRET analysis indicate that Schwann cell-derived RNAs co-localize with microtubules in Schwann cell cytoplasm. Additionally, transport of Schwann cell-derived RNAs is nocodazole and colchicine sensitive demonstrating its dependence on microtubule network integrity. Moreover, mRNAs codifying neuron-specific proteins are among Schwann cell newly synthesized RNAs population, and some of them are associated with KIF1B and KIF5B microtubules-based motors.
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8
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Langille JJ, Ginzberg K, Sossin WS. Polysomes identified by live imaging of nascent peptides are stalled in hippocampal and cortical neurites. ACTA ACUST UNITED AC 2019; 26:351-362. [PMID: 31416908 PMCID: PMC6699411 DOI: 10.1101/lm.049965.119] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Accepted: 06/10/2019] [Indexed: 12/18/2022]
Abstract
In neurons, mRNAs can be repressed postinitiation and assembled into granules enabling the transport and later, regulated reactivation of the paused mRNAs. It has been suggested that a large percentage of transcripts in neuronal processes are stored in these stalled polysomes. Given this, it is predicted that nascent peptides should be abundant in these granules. Nascent peptides can be visualized in real time by the SunTag system. Using this system, we observe nascent peptides in neuronal processes that are resistant to runoff with the initiation inhibitor homoharringtonin (HHT) and to release by puromycin, properties expected from RNA granules consisting of stalled polysomes. In contrast, nascent peptides in nonneuronal cells and neuronal cell bodies were not resistant to HHT or puromycin. Stalled polysomes can also be visualized after runoff with ribopuromycylation and the RNA granules imaged with ribopuromycylation were the same as those with SunTag visualized nascent peptides. Accordingly, the ribopuromycylated puncta in neuronal dendrites were also resistant to puromycin. Thus, the SunTag technique corroborates in situ evidence of stalled polysomes and will allow for the live examination of these translational structures as a mechanism for mRNA transport and regulated protein synthesis.
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Affiliation(s)
- Jesse J Langille
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal H3A-2B4, Quebec, Canada
| | - Keren Ginzberg
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal H3A-2B4, Quebec, Canada
| | - Wayne S Sossin
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal H3A-2B4, Quebec, Canada
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9
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Moissoglu K, Yasuda K, Wang T, Chrisafis G, Mili S. Translational regulation of protrusion-localized RNAs involves silencing and clustering after transport. eLife 2019; 8:44752. [PMID: 31290739 PMCID: PMC6639073 DOI: 10.7554/elife.44752] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2018] [Accepted: 07/08/2019] [Indexed: 02/06/2023] Open
Abstract
Localization of RNAs to various subcellular destinations is a widely used mechanism that regulates a large proportion of transcripts in polarized cells. In many cases, such localized transcripts mediate spatial control of gene expression by being translationally silent while in transit and locally activated at their destination. Here, we investigate the translation of RNAs localized at dynamic cellular protrusions of human and mouse, migrating, mesenchymal cells. In contrast to the model described above, we find that protrusion-localized RNAs are not locally activated solely at protrusions, but can be translated with similar efficiency in both internal and peripheral locations. Interestingly, protrusion-localized RNAs are translated at extending protrusions, they become translationally silenced in retracting protrusions and this silencing is accompanied by coalescence of single RNAs into larger heterogeneous RNA clusters. This work describes a distinct mode of translational regulation of localized RNAs, which we propose is used to regulate protein activities during dynamic cellular responses.
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Affiliation(s)
- Konstadinos Moissoglu
- Laboratory of Cellular and Molecular Biology,Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, United States
| | - Kyota Yasuda
- Laboratory of Cellular and Molecular Biology,Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, United States.,Program of Mathematical and Life Sciences, Graduate School of Integrated Science for Life, Hiroshima University, Higashi-Hiroshima, Japan.,Laboratory for Comprehensive Bioimaging, RIKEN Center for Biosystems Dynamics Research, Suita, Japan
| | - Tianhong Wang
- Laboratory of Cellular and Molecular Biology,Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, United States
| | - George Chrisafis
- Laboratory of Cellular and Molecular Biology,Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, United States
| | - Stavroula Mili
- Laboratory of Cellular and Molecular Biology,Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, United States
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10
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Hoch-Kraft P, Trotter J, Gonsior C. Missing in Action: Dysfunctional RNA Metabolism in Oligodendroglial Cells as a Contributor to Neurodegenerative Diseases? Neurochem Res 2019; 45:566-579. [PMID: 30843138 DOI: 10.1007/s11064-019-02763-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Revised: 02/22/2019] [Accepted: 02/23/2019] [Indexed: 12/14/2022]
Abstract
The formation of myelin around axons by oligodendrocytes (OL) poses an enormous synthetic and energy challenge for the glial cell. Local translation of transcripts, including the mRNA for the essential myelin protein Myelin Basic Protein (MBP) at the site of myelin deposition has been recognised as an efficient mechanism to assure proper myelin sheath assembly. Oligodendroglial precursor cells (OPCs) form synapses with neurons and may localise many additional mRNAs in a similar fashion to synapses between neurons. In some diseases in which demyelination occurs, an abundance of OPCs is present but there is a failure to efficiently remyelinate and to synthesise MBP. This compromises axonal survival and function. OPCs are especially sensitive to cellular stress as occurring in neurodegenerative diseases, which can impinge on their ability to translate mRNAs into protein. Stress causes the build up of cytoplasmic stress granules (SG) in which many RNAs are sequestered and translationally stalled until the stress ceases. Chronic stress in particular could convert this initially protective reaction of the cell into damage, as persistence of SG may lead to pathological aggregate formation or long-term translation block of SG-associated RNAs. The recent recognition that many neurodegenerative diseases often exhibit an early white matter pathology with a proliferation of surviving OPCs, renders a study of the stress-associated processes in oligodendrocytes and OPCs especially relevant. Here, we discuss a potential dysfunction of RNA regulation in myelin diseases such as Multiple Sclerosis (MS) and Vanishing white matter disease (VWM) and potential contributions of OL dysfunction to neurodegenerative diseases such as Amyotrophic lateral sclerosis (ALS), Alzheimer's disease (AD) and Fragile X syndrome (FXS).
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Affiliation(s)
- Peter Hoch-Kraft
- Cellular Neurobiology, Institute for Developmental Biology and Neurobiology, Johannes Gutenberg-University of Mainz, Anselm-Franz-von-Bentzelweg 3, 55128, Mainz, Germany
| | - Jacqueline Trotter
- Cellular Neurobiology, Institute for Developmental Biology and Neurobiology, Johannes Gutenberg-University of Mainz, Anselm-Franz-von-Bentzelweg 3, 55128, Mainz, Germany
| | - Constantin Gonsior
- Cellular Neurobiology, Institute for Developmental Biology and Neurobiology, Johannes Gutenberg-University of Mainz, Anselm-Franz-von-Bentzelweg 3, 55128, Mainz, Germany.
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11
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Higher-Order Organization Principles of Pre-translational mRNPs. Mol Cell 2018; 72:715-726.e3. [PMID: 30415953 DOI: 10.1016/j.molcel.2018.09.012] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Revised: 06/20/2018] [Accepted: 09/12/2018] [Indexed: 11/21/2022]
Abstract
Compared to noncoding RNAs (ncRNAs), such as rRNAs and ribozymes, for which high-resolution structures abound, little is known about the tertiary structures of mRNAs. In eukaryotic cells, newly made mRNAs are packaged with proteins in highly compacted mRNA particles (mRNPs), but the manner of this mRNA compaction is unknown. Here, we developed and implemented RIPPLiT (RNA immunoprecipitation and proximity ligation in tandem), a transcriptome-wide method for probing the 3D conformations of RNAs stably associated with defined proteins, in this case, exon junction complex (EJC) core factors. EJCs multimerize with other mRNP components to form megadalton-sized complexes that protect large swaths of newly synthesized mRNAs from endonuclease digestion. Unlike ncRNPs, wherein strong locus-specific structures predominate, mRNPs behave more like flexible polymers. Polymer analysis of proximity ligation data for hundreds of mRNA species demonstrates that nascent and pre-translational mammalian mRNAs are compacted by their associated proteins into linear rod-like structures.
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12
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Aguilera-Gomez A, Zacharogianni M, van Oorschot MM, Genau H, Grond R, Veenendaal T, Sinsimer KS, Gavis ER, Behrends C, Rabouille C. Phospho-Rasputin Stabilization by Sec16 Is Required for Stress Granule Formation upon Amino Acid Starvation. Cell Rep 2018; 20:935-948. [PMID: 28746877 DOI: 10.1016/j.celrep.2017.06.042] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Revised: 04/22/2017] [Accepted: 06/16/2017] [Indexed: 12/15/2022] Open
Abstract
Most cellular stresses induce protein translation inhibition and stress granule formation. Here, using Drosophila S2 cells, we investigate the role of G3BP/Rasputin in this process. In contrast to arsenite treatment, where dephosphorylated Ser142 Rasputin is recruited to stress granules, we find that, upon amino acid starvation, only the phosphorylated Ser142 form is recruited. Furthermore, we identify Sec16, a component of the endoplasmic reticulum exit site, as a Rasputin interactor and stabilizer. Sec16 depletion results in Rasputin degradation and inhibition of stress granule formation. However, in the absence of Sec16, pharmacological stabilization of Rasputin is not enough to rescue the assembly of stress granules. This is because Sec16 specifically interacts with phosphorylated Ser142 Rasputin, the form required for stress granule formation upon amino acid starvation. Taken together, these results demonstrate that stress granule formation is fine-tuned by specific signaling cues that are unique to each stress. These results also expand the role of Sec16 as a stress response protein.
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Affiliation(s)
- Angelica Aguilera-Gomez
- Hubrecht Institute-KNAW & University Medical Center (UMC) Utrecht, Uppsalalaan 8, 3584 CT Utrecht, the Netherlands
| | - Margarita Zacharogianni
- Hubrecht Institute-KNAW & University Medical Center (UMC) Utrecht, Uppsalalaan 8, 3584 CT Utrecht, the Netherlands
| | - Marinke M van Oorschot
- Hubrecht Institute-KNAW & University Medical Center (UMC) Utrecht, Uppsalalaan 8, 3584 CT Utrecht, the Netherlands
| | - Heide Genau
- Institute of Biochemistry II, Medical School Goethe University, 60323 Frankfurt am Main, Germany
| | - Rianne Grond
- Hubrecht Institute-KNAW & University Medical Center (UMC) Utrecht, Uppsalalaan 8, 3584 CT Utrecht, the Netherlands
| | - Tineke Veenendaal
- Department of Cell Biology, UMC Utrecht, 3584 CT Utrecht, the Netherlands
| | - Kristina S Sinsimer
- Department of Molecular Biology, Princeton University, Washington Road, Princeton, NJ 08544, USA
| | - Elizabeth R Gavis
- Department of Molecular Biology, Princeton University, Washington Road, Princeton, NJ 08544, USA
| | - Christian Behrends
- Institute of Biochemistry II, Medical School Goethe University, 60323 Frankfurt am Main, Germany
| | - Catherine Rabouille
- Hubrecht Institute-KNAW & University Medical Center (UMC) Utrecht, Uppsalalaan 8, 3584 CT Utrecht, the Netherlands; Department of Cell Biology, UMC Utrecht, 3584 CT Utrecht, the Netherlands; Department of Cell Biology, UMC Groningen, 9713 GZ Groningen, the Netherlands.
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13
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Banerjee A, Ifrim MF, Valdez AN, Raj N, Bassell GJ. Aberrant RNA translation in fragile X syndrome: From FMRP mechanisms to emerging therapeutic strategies. Brain Res 2018; 1693:24-36. [PMID: 29653083 PMCID: PMC7377270 DOI: 10.1016/j.brainres.2018.04.008] [Citation(s) in RCA: 76] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Revised: 03/30/2018] [Accepted: 04/06/2018] [Indexed: 02/07/2023]
Abstract
Research in the past decades has unfolded the multifaceted role of Fragile X mental retardation protein (FMRP) and how its absence contributes to the pathophysiology of Fragile X syndrome (FXS). Excess signaling through group 1 metabotropic glutamate receptors is commonly observed in mouse models of FXS, which in part is attributed to dysregulated translation and downstream signaling. Considering the wide spectrum of cellular and physiologic functions that loss of FMRP can affect in general, it may be advantageous to pursue disease mechanism based treatments that directly target translational components or signaling factors that regulate protein synthesis. Various FMRP targets upstream and downstream of the translational machinery are therefore being investigated to further our understanding of the molecular mechanism of RNA and protein synthesis dysregulation in FXS as well as test their potential role as therapeutic interventions to alleviate FXS associated symptoms. In this review, we will broadly discuss recent advancements made towards understanding the role of FMRP in translation regulation, new pre-clinical animal models with FMRP targets located at different levels of the translational and signal transduction pathways for therapeutic intervention as well as future use of stem cells to model FXS associated phenotypes.
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Affiliation(s)
- Anwesha Banerjee
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322, USA.
| | - Marius F Ifrim
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Arielle N Valdez
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Nisha Raj
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Gary J Bassell
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322, USA; Department of Neurology, Emory University School of Medicine, Atlanta, GA 30322, USA.
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14
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Hoch-Kraft P, White R, Tenzer S, Krämer-Albers EM, Trotter J, Gonsior C. Dual role of the RNA helicase DDX5 in post-transcriptional regulation of Myelin Basic Protein in oligodendrocytes. J Cell Sci 2018; 131:jcs.204750. [DOI: 10.1242/jcs.204750] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Accepted: 03/28/2018] [Indexed: 01/11/2023] Open
Abstract
In the central nervous system, oligodendroglial expression of Myelin Basic Protein (MBP) is crucial for the assembly and structure of the myelin sheath. MBP synthesis is tightly regulated in space and time, particularly on the post-transcriptional level. We have identified the DEAD-box RNA helicase DDX5 (alias p68) in a complex with Mbp mRNA in oligodendroglial cells. Expression of DDX5 is highest in progenitor cells and immature oligodendrocytes, where it localizes to heterogeneous populations of cytoplasmic ribonucleoprotein (RNP) complexes associated with Mbp mRNA in the cell body and processes. Manipulation of DDX5 protein amounts inversely affects levels of MBP protein. We present evidence that DDX5 is involved in post-transcriptional regulation of MBP protein synthesis, with implications for oligodendroglial development. In addition, DDX5 knockdown results in an increased abundance of MBP exon 2-positive isoforms in immature oligodendrocytes, most likely by regulating alternative splicing of Mbp. Our findings contribute to the understanding of the complex nature of MBP post-transcriptional control in immature oligodendrocytes where DDX5 appears to affect the abundance of MBP proteins via distinct but converging mechanisms.
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Affiliation(s)
- Peter Hoch-Kraft
- Molecular Cell Biology, Institute for Developmental Biology and Neurobiology, Johannes Gutenberg-University of Mainz, Anselm-Franz-von-Bentzelweg 3, 55128 Mainz, Germany
| | - Robin White
- Molecular Cell Biology, Institute for Developmental Biology and Neurobiology, Johannes Gutenberg-University of Mainz, Anselm-Franz-von-Bentzelweg 3, 55128 Mainz, Germany
- Institute of Physiology and Pathophysiology, University Medical Center of the Johannes Gutenberg-University, Duesbergweg 6, 55128 Mainz, Germany
| | - Stefan Tenzer
- Institute for Immunology, University Medical Center Mainz, Langenbeckstr. 1, 55131 Mainz, Germany
| | - Eva-Maria Krämer-Albers
- Molecular Cell Biology, Institute for Developmental Biology and Neurobiology, Johannes Gutenberg-University of Mainz, Anselm-Franz-von-Bentzelweg 3, 55128 Mainz, Germany
| | - Jacqueline Trotter
- Molecular Cell Biology, Institute for Developmental Biology and Neurobiology, Johannes Gutenberg-University of Mainz, Anselm-Franz-von-Bentzelweg 3, 55128 Mainz, Germany
| | - Constantin Gonsior
- Molecular Cell Biology, Institute for Developmental Biology and Neurobiology, Johannes Gutenberg-University of Mainz, Anselm-Franz-von-Bentzelweg 3, 55128 Mainz, Germany
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15
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Manduca Contactin Regulates Amyloid Precursor Protein-Dependent Neuronal Migration. J Neurosci 2017; 36:8757-75. [PMID: 27535920 DOI: 10.1523/jneurosci.0729-16.2016] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2016] [Accepted: 07/12/2016] [Indexed: 01/06/2023] Open
Abstract
UNLABELLED Amyloid precursor protein (APP) was originally identified as the source of β-amyloid peptides that accumulate in Alzheimer's disease (AD), but it also has been implicated in the control of multiple aspects of neuronal motility. APP belongs to an evolutionarily conserved family of transmembrane proteins that can interact with a variety of adapter and signaling molecules. Recently, we showed that both APP and its insect ortholog [APPL (APP-Like)] directly bind the heterotrimeric G-protein Goα, supporting the model that APP can function as an unconventional Goα-coupled receptor. We also adapted a well characterized assay of neuronal migration in the hawkmoth, Manduca sexta, to show that APPL-Goα signaling restricts ectopic growth within the developing nervous system, analogous to the role postulated for APP family proteins in controlling migration within the mammalian cortex. Using this assay, we have now identified Manduca Contactin (MsContactin) as an endogenous ligand for APPL, consistent with previous work showing that Contactins interact with APP family proteins in other systems. Using antisense-based knockdown protocols and fusion proteins targeting both proteins, we have shown that MsContactin is selectively expressed by glial cells that ensheath the migratory neurons (expressing APPL), and that MsContactin-APPL interactions normally prevent inappropriate migration and outgrowth. These results provide new evidence that Contactins can function as authentic ligands for APP family proteins that regulate APP-dependent responses in the developing nervous system. They also support the model that misregulated Contactin-APP interactions might provoke aberrant activation of Goα and its effectors, thereby contributing to the neurodegenerative sequelae that typify AD. SIGNIFICANCE STATEMENT Members of the amyloid precursor protein (APP) family participate in many aspects of neuronal development, but the ligands that normally activate APP signaling have remained controversial. This research provides new evidence that members of the Contactin family function as authentic ligands for APP and its orthologs, and that this evolutionarily conserved class of membrane-attached proteins regulates key aspects of APP-dependent migration and outgrowth in the embryonic nervous system. By defining the normal role of Contactin-APP signaling during development, these studies also provide the framework for investigating how the misregulation of Contactin-APP interactions might contribute to neuronal dysfunction in the context of both normal aging and neurodegenerative conditions, including Alzheimer's disease.
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16
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Falkenberg CV, Carson JH, Blinov ML. Multivalent Molecules as Modulators of RNA Granule Size and Composition. Biophys J 2017; 113:235-245. [PMID: 28242011 DOI: 10.1016/j.bpj.2017.01.031] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Revised: 01/20/2017] [Accepted: 01/24/2017] [Indexed: 01/22/2023] Open
Abstract
RNA granules are ensembles of specific RNA and protein molecules that mediate localized translation in eukaryotic cells. The mechanisms for formation and selectivity of RNA granules are unknown. Here we present a model for assembly of one type of RNA granule based on experimentally measured binding interactions among three core multivalent molecular components necessary for such assembly: specific RNA molecules that contain a cis-acting sequence called the A2 response element (A2RE), hnRNP A2 proteins that bind specifically (with high affinity) to A2RE sequences or nonspecifically (with lower affinity) to other RNA sequences, and heptavalent protein cytoskeleton-associated protein 5 (CKAP5, an alternative name for TOG protein) that binds both hnRNP A2 molecules and RNA. Non-A2RE RNA molecules (RNA without the A2RE sequence) that may be recruited to the granules through nonspecific interactions are also considered in the model. Modeling multivalent molecular interactions in granules is challenging because of combinatorial complexity in the number of potential molecular complexes among these core components and dynamic changes in granule composition and structure in response to changes in local intracellular environment. We use a hybrid modeling approach (deterministic-stochastic-statistical) that is appropriate when the overall compositions of multimolecular ensembles are of greater importance than the specific interactions among individual molecular components. Modeling studies titrating the concentrations of various granule components and varying effective site pair affinities and RNA valency demonstrate that interactions between multivalent components (TOG and RNA) are modulated by a bivalent adaptor molecule (hnRNP A2). Formation and disruption of granules, as well as RNA selectivity in granule composition are regulated by distinct concentration regimes of A2. Our results suggest that granule assembly is tightly controlled by multivalent molecular interactions among RNA molecules, adaptor proteins, and scaffold proteins.
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Affiliation(s)
- Cibele Vieira Falkenberg
- Mechanical Engineering Department, Samuel Ginn College of Engineering, Auburn University, Auburn, Alabama.
| | - John H Carson
- Center for Cell Analysis and Modeling, University of Connecticut School of Medicine, Farmington, Connecticut; Department of Molecular Biology and Biophysics, University of Connecticut School of Medicine, Farmington, Connecticut
| | - Michael L Blinov
- Center for Cell Analysis and Modeling, University of Connecticut School of Medicine, Farmington, Connecticut.
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17
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Thakurela S, Garding A, Jung RB, Müller C, Goebbels S, White R, Werner HB, Tiwari VK. The transcriptome of mouse central nervous system myelin. Sci Rep 2016; 6:25828. [PMID: 27173133 PMCID: PMC4865983 DOI: 10.1038/srep25828] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Accepted: 04/21/2016] [Indexed: 01/03/2023] Open
Abstract
Rapid nerve conduction in the CNS is facilitated by insulation of axons with myelin, a specialized oligodendroglial compartment distant from the cell body. Myelin is turned over and adapted throughout life; however, the molecular and cellular basis of myelin dynamics remains elusive. Here we performed a comprehensive transcriptome analysis (RNA-seq) of myelin biochemically purified from mouse brains at various ages and find a surprisingly large pool of transcripts enriched in myelin. Further computational analysis showed that the myelin transcriptome is closely related to the myelin proteome but clearly distinct from the transcriptomes of oligodendrocytes and brain tissues, suggesting a highly selective incorporation of mRNAs into the myelin compartment. The mRNA-pool in myelin displays maturation-dependent dynamic changes of composition, abundance, and functional associations; however ageing-dependent changes after 6 months were minor. We suggest that this transcript pool enables myelin turnover and the local adaptation of individual pre-existing myelin sheaths.
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Affiliation(s)
| | - Angela Garding
- Institute of Molecular Biology (IMB), 55128 Mainz, Germany
| | - Ramona B. Jung
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Christina Müller
- Institute of Physiology, University Medical Center of the Johannes Gutenberg-University, 55128 Mainz, Germany
| | - Sandra Goebbels
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Robin White
- Institute of Physiology, University Medical Center of the Johannes Gutenberg-University, 55128 Mainz, Germany
| | - Hauke B. Werner
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
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18
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Schäfer I, Müller C, Luhmann HJ, White R. MOBP levels are regulated by Fyn kinase and affect the morphological differentiation of oligodendrocytes. J Cell Sci 2016; 129:930-42. [PMID: 26801084 DOI: 10.1242/jcs.172148] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2015] [Accepted: 01/20/2016] [Indexed: 01/24/2023] Open
Abstract
Oligodendrocytes are the myelinating glial cells of the central nervous system (CNS). Myelin is formed by extensive wrapping of oligodendroglial processes around axonal segments, which ultimately allows a rapid saltatory conduction of action potentials within the CNS and sustains neuronal health. The non-receptor tyrosine kinase Fyn is an important signaling molecule in oligodendrocytes. It controls the morphological differentiation of oligodendrocytes and is an integrator of axon-glial signaling cascades leading to localized synthesis of myelin basic protein (MBP), which is essential for myelin formation. The abundant myelin-associated oligodendrocytic basic protein (MOBP) resembles MBP in several aspects and has also been reported to be localized as mRNA and translated in the peripheral myelin compartment. The signals initiating local MOBP synthesis are so far unknown and the cellular function of MOBP remains elusive. Here, we show, by several approaches in cultured primary oligodendrocytes, that MOBP synthesis is stimulated by Fyn activity. Moreover, we reveal a new function for MOBP in oligodendroglial morphological differentiation.
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Affiliation(s)
- Isabelle Schäfer
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University, Duesbergweg 6, Mainz 55128, Germany
| | - Christina Müller
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University, Duesbergweg 6, Mainz 55128, Germany
| | - Heiko J Luhmann
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University, Duesbergweg 6, Mainz 55128, Germany
| | - Robin White
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University, Duesbergweg 6, Mainz 55128, Germany
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19
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Singh G, Pratt G, Yeo GW, Moore MJ. The Clothes Make the mRNA: Past and Present Trends in mRNP Fashion. Annu Rev Biochem 2015; 84:325-54. [PMID: 25784054 DOI: 10.1146/annurev-biochem-080111-092106] [Citation(s) in RCA: 272] [Impact Index Per Article: 30.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Throughout their lifetimes, messenger RNAs (mRNAs) associate with proteins to form ribonucleoproteins (mRNPs). Since the discovery of the first mRNP component more than 40 years ago, what is known as the mRNA interactome now comprises >1,000 proteins. These proteins bind mRNAs in myriad ways with varying affinities and stoichiometries, with many assembling onto nascent RNAs in a highly ordered process during transcription and precursor mRNA (pre-mRNA) processing. The nonrandom distribution of major mRNP proteins observed in transcriptome-wide studies leads us to propose that mRNPs are organized into three major domains loosely corresponding to 5' untranslated regions (UTRs), open reading frames, and 3' UTRs. Moving from the nucleus to the cytoplasm, mRNPs undergo extensive remodeling as they are first acted upon by the nuclear pore complex and then by the ribosome. When not being actively translated, cytoplasmic mRNPs can assemble into large multi-mRNP assemblies or be permanently disassembled and degraded. In this review, we aim to give the reader a thorough understanding of past and current eukaryotic mRNP research.
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Affiliation(s)
- Guramrit Singh
- Department of Molecular Genetics, Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210;
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20
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Smith R, Rathod RJ, Rajkumar S, Kennedy D. Nervous translation, do you get the message? A review of mRNPs, mRNA-protein interactions and translational control within cells of the nervous system. Cell Mol Life Sci 2014; 71:3917-37. [PMID: 24952431 PMCID: PMC11113408 DOI: 10.1007/s00018-014-1660-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2014] [Revised: 05/22/2014] [Accepted: 05/30/2014] [Indexed: 01/01/2023]
Abstract
In neurons, translation of a message RNA can occur metres away from its transcriptional origin and in normal cells this is orchestrated with perfection. The life of an mRNA will see it pass through multiple steps of processing in the nucleus and the cytoplasm before it reaches its final destination. Processing of mRNA is determined by a myriad of RNA-binding proteins in multi-protein complexes called messenger ribonucleoproteins; however, incorrect processing and delivery of mRNA can cause several human neurological disorders. This review takes us through the life of mRNA from the nucleus to its point of translation in the cytoplasm. The review looks at the various cis and trans factors that act on the mRNA and discusses their roles in different cells of the nervous system and human disorders.
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Affiliation(s)
- Ross Smith
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD, 4072, Australia,
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21
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Falkenberg CV, Blinov ML, Loew LM. Pleomorphic ensembles: formation of large clusters composed of weakly interacting multivalent molecules. Biophys J 2014; 105:2451-60. [PMID: 24314076 DOI: 10.1016/j.bpj.2013.10.016] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2013] [Revised: 10/07/2013] [Accepted: 10/18/2013] [Indexed: 01/31/2023] Open
Abstract
Molecular interactions of importance to cell biology are subject to sol-gel transitions: large clusters of weakly interacting multivalent molecules (gel phase) are produced at a critical concentration of monomers. Examples include cell-cell and cell-matrix adhesions, nucleoprotein bodies, and cell signaling platforms. We use the term pleomorphic ensembles (PEs) to describe these clusters, because they have dynamic compositions and sizes and have rapid turnover of their molecular constituents; this plasticity can be highly responsive to cellular signals. The classical polymer physical chemistry theory developed by Flory and Stockmayer provides a brilliant framework for treating multivalent interactions for simple idealized systems. But the complexity and variability of PEs challenges existing modeling approaches. Here we describe and validate a computational algorithm that extends the Flory-Stockmayer formalism to overcome the limitations of analytic theories. We divide the problem by deterministically calculating the fraction of bound sites for each type of binding site, followed by the stochastic assignment of the bonds to a finite number of molecules. The method allows for high valency within many different kinds of interacting molecules and site types, permits simulation of steady-state distributions, as well as assembly kinetics, and can treat cooperative binding within one of the interacting molecules. We then apply our method to the analysis of interactions in the nephrin-Nck-N-Wasp signaling system, demonstrating how multivalent layered scaffolds produce PEs at low monomer concentrations despite weak binding interactions. We show how the experimental data for this system are most consistent with synergistic cooperative interactions between Nck and N-Wasp.
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Affiliation(s)
- Cibele V Falkenberg
- Richard D. Berlin Center for Cell Analysis and Modeling, University of Connecticut Health Center, Farmington, Connecticut, United States of America.
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22
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Czaplinski K. Understanding mRNA trafficking: Are we there yet? Semin Cell Dev Biol 2014; 32:63-70. [DOI: 10.1016/j.semcdb.2014.04.025] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2014] [Accepted: 04/17/2014] [Indexed: 10/25/2022]
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23
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Amor S, Peferoen LAN, Vogel DYS, Breur M, van der Valk P, Baker D, van Noort JM. Inflammation in neurodegenerative diseases--an update. Immunology 2014; 142:151-66. [PMID: 24329535 DOI: 10.1111/imm.12233] [Citation(s) in RCA: 360] [Impact Index Per Article: 36.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2013] [Revised: 12/09/2013] [Accepted: 12/11/2013] [Indexed: 12/12/2022] Open
Abstract
Neurodegeneration, the progressive dysfunction and loss of neurons in the central nervous system (CNS), is the major cause of cognitive and motor dysfunction. While neuronal degeneration is well-known in Alzheimer's and Parkinson's diseases, it is also observed in neurotrophic infections, traumatic brain and spinal cord injury, stroke, neoplastic disorders, prion diseases, multiple sclerosis and amyotrophic lateral sclerosis, as well as neuropsychiatric disorders and genetic disorders. A common link between these diseases is chronic activation of innate immune responses including those mediated by microglia, the resident CNS macrophages. Such activation can trigger neurotoxic pathways leading to progressive degeneration. Yet, microglia are also crucial for controlling inflammatory processes, and repair and regeneration. The adaptive immune response is implicated in neurodegenerative diseases contributing to tissue damage, but also plays important roles in resolving inflammation and mediating neuroprotection and repair. The growing awareness that the immune system is inextricably involved in mediating damage as well as regeneration and repair in neurodegenerative disorders, has prompted novel approaches to modulate the immune system, although it remains whether these approaches can be used in humans. Additional factors in humans include ageing and exposure to environmental factors such as systemic infections that provide additional clues that may be human specific and therefore difficult to translate from animal models. Nevertheless, a better understanding of how immune responses are involved in neuronal damage and regeneration, as reviewed here, will be essential to develop effective therapies to improve quality of life, and mitigate the personal, economic and social impact of these diseases.
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Affiliation(s)
- Sandra Amor
- Department of Pathology, VU University Medical Centre, Amsterdam, the Netherlands; Neuroimmunology Unit, Blizard Institute of Cell and Molecular Science, Barts and The London School of Medicine and Dentistry, London, UK
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24
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White R, Krämer-Albers EM. Axon-glia interaction and membrane traffic in myelin formation. Front Cell Neurosci 2014; 7:284. [PMID: 24431989 PMCID: PMC3880936 DOI: 10.3389/fncel.2013.00284] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2013] [Accepted: 12/18/2013] [Indexed: 12/12/2022] Open
Abstract
In vertebrate nervous systems myelination of neuronal axons has evolved to increase conduction velocity of electrical impulses with minimal space and energy requirements. Myelin is formed by specialized glial cells which ensheath axons with a lipid-rich insulating membrane. Myelination is a multi-step process initiated by axon-glia recognition triggering glial polarization followed by targeted myelin membrane expansion and compaction. Thereby, a myelin sheath of complex subdomain structure is established. Continuous communication between neurons and glial cells is essential for myelin maintenance and axonal integrity. A diverse group of diseases, from multiple sclerosis to schizophrenia, have been linked to malfunction of myelinating cells reflecting the physiological importance of the axon-glial unit. This review describes the mechanisms of axonal signal integration by oligodendrocytes emphasizing the central role of the Src-family kinase Fyn during central nervous system (CNS) myelination. Furthermore, we discuss myelin membrane trafficking with particular focus on endocytic recycling and the control of proteolipid protein (PLP) transport by soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins. Finally, PLP mistrafficking is considered in the context of myelin diseases.
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Affiliation(s)
- Robin White
- Institute of Physiology and Pathophysiology, University Medical Center of the Johannes Gutenberg University Mainz, Germany
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25
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Iwata K, Café-Mendes CC, Schmitt A, Steiner J, Manabe T, Matsuzaki H, Falkai P, Turck CW, Martins-de-Souza D. The human oligodendrocyte proteome. Proteomics 2013; 13:3548-53. [DOI: 10.1002/pmic.201300201] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2013] [Revised: 08/28/2013] [Accepted: 10/07/2013] [Indexed: 11/08/2022]
Affiliation(s)
- Keiko Iwata
- Department of Psychiatry and Psychotherapy; Ludwig Maximilians University of Munich (LMU); Munich Germany
- Research Center for Child Mental Development; University of Fukui; Japan
- Department of Development of Functional Brain Activities; United Graduate School of Child Development; Osaka University, Kanazawa University, Hamamatsu University School of Medicine; Chiba University and University of Fukui; Fukui Japan
| | - Cecilia C. Café-Mendes
- Max Planck Institute for Psychiatry; Proteomics and Biomarkers; Munich Germany
- Lab. de Neurobiologia Celular, Inst. Ciências Biomédicas; Universidade de São Paulo (USP); São Paulo SP Brazil
| | - Andrea Schmitt
- Department of Psychiatry and Psychotherapy; Ludwig Maximilians University of Munich (LMU); Munich Germany
- Lab. de Neurociências (LIM-27); Inst. de Psiquaitria, Faculdade de Medicina da Universidade de Sao Paulo; São Paulo Brazil
| | - Johann Steiner
- Department of Psychiatry; University of Magdeburg; Magdeburg Germany
| | - Takayuki Manabe
- Division of Gene Expression Mechanism; Institute for Comprehensive Medical Science; Fujita Health University; Aichi Japan
| | - Hideo Matsuzaki
- Research Center for Child Mental Development; University of Fukui; Japan
- Department of Development of Functional Brain Activities; United Graduate School of Child Development; Osaka University, Kanazawa University, Hamamatsu University School of Medicine; Chiba University and University of Fukui; Fukui Japan
| | - Peter Falkai
- Department of Psychiatry and Psychotherapy; Ludwig Maximilians University of Munich (LMU); Munich Germany
| | - Christoph W. Turck
- Max Planck Institute for Psychiatry; Proteomics and Biomarkers; Munich Germany
| | - Daniel Martins-de-Souza
- Department of Psychiatry and Psychotherapy; Ludwig Maximilians University of Munich (LMU); Munich Germany
- Max Planck Institute for Psychiatry; Proteomics and Biomarkers; Munich Germany
- Lab. de Neurociências (LIM-27); Inst. de Psiquaitria, Faculdade de Medicina da Universidade de Sao Paulo; São Paulo Brazil
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26
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Harauz G, Boggs JM. Myelin management by the 18.5-kDa and 21.5-kDa classic myelin basic protein isoforms. J Neurochem 2013; 125:334-61. [PMID: 23398367 DOI: 10.1111/jnc.12195] [Citation(s) in RCA: 103] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Revised: 02/05/2013] [Accepted: 02/05/2013] [Indexed: 12/15/2022]
Abstract
The classic myelin basic protein (MBP) splice isoforms range in nominal molecular mass from 14 to 21.5 kDa, and arise from the gene in the oligodendrocyte lineage (Golli) in maturing oligodendrocytes. The 18.5-kDa isoform that predominates in adult myelin adheres the cytosolic surfaces of oligodendrocyte membranes together, and forms a two-dimensional molecular sieve restricting protein diffusion into compact myelin. However, this protein has additional roles including cytoskeletal assembly and membrane extension, binding to SH3-domains, participation in Fyn-mediated signaling pathways, sequestration of phosphoinositides, and maintenance of calcium homeostasis. Of the diverse post-translational modifications of this isoform, phosphorylation is the most dynamic, and modulates 18.5-kDa MBP's protein-membrane and protein-protein interactions, indicative of a rich repertoire of functions. In developing and mature myelin, phosphorylation can result in microdomain or even nuclear targeting of the protein, supporting the conclusion that 18.5-kDa MBP has significant roles beyond membrane adhesion. The full-length, early-developmental 21.5-kDa splice isoform is predominantly karyophilic due to a non-traditional P-Y nuclear localization signal, with effects such as promotion of oligodendrocyte proliferation. We discuss in vitro and recent in vivo evidence for multifunctionality of these classic basic proteins of myelin, and argue for a systematic evaluation of the temporal and spatial distributions of these protein isoforms, and their modified variants, during oligodendrocyte differentiation.
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Affiliation(s)
- George Harauz
- Department of Molecular and Cellular Biology, Biophysics Interdepartmental Group and Collaborative Program in Neuroscience, University of Guelph, Guelph, Ontario, Canada.
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27
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Abstract
The fundamental roles of Schwann cells during peripheral nerve formation and regeneration have been recognized for more than 100 years, but the cellular and molecular mechanisms that integrate Schwann cell and axonal functions continue to be elucidated. Derived from the embryonic neural crest, Schwann cells differentiate into myelinating cells or bundle multiple unmyelinated axons into Remak fibers. Axons dictate which differentiation path Schwann cells follow, and recent studies have established that axonal neuregulin1 signaling via ErbB2/B3 receptors on Schwann cells is essential for Schwann cell myelination. Extracellular matrix production and interactions mediated by specific integrin and dystroglycan complexes are also critical requisites for Schwann cell-axon interactions. Myelination entails expansion and specialization of the Schwann cell plasma membrane over millimeter distances. Many of the myelin-specific proteins have been identified, and transgenic manipulation of myelin genes have provided novel insights into myelin protein function, including maintenance of axonal integrity and survival. Cellular events that facilitate myelination, including microtubule-based protein and mRNA targeting, and actin based locomotion, have also begun to be understood. Arguably, the most remarkable facet of Schwann cell biology, however, is their vigorous response to axonal damage. Degradation of myelin, dedifferentiation, division, production of axonotrophic factors, and remyelination all underpin the substantial regenerative capacity of the Schwann cells and peripheral nerves. Many of these properties are not shared by CNS fibers, which are myelinated by oligodendrocytes. Dissecting the molecular mechanisms responsible for the complex biology of Schwann cells continues to have practical benefits in identifying novel therapeutic targets not only for Schwann cell-specific diseases but other disorders in which axons degenerate.
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Affiliation(s)
- Grahame J Kidd
- Department of Neuroscience, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA.
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Tolino M, Köhrmann M, Kiebler MA. RNA-binding proteins involved in RNA localization and their implications in neuronal diseases. Eur J Neurosci 2012; 35:1818-36. [PMID: 22708593 DOI: 10.1111/j.1460-9568.2012.08160.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Very often, developmental abnormalities or subtle disturbances of neuronal function may yield brain diseases even if they become obvious only late in life. It is therefore our intention to highlight fundamental mechanisms of neuronal cell biology with a special emphasis on dendritic mRNA localization including local protein synthesis at the activated synapse. Furthermore, we would like to point out possible links to neuronal or synaptic dysfunction. In particular, we will focus on a series of well-known RNA-binding proteins that are involved in these processes and outline how their dysfunction might yield neurodevelopmental, neurodegenerative or neuropsychiatric disorders. We are convinced that increasing our understanding of RNA biology in general and the mechanisms underlying mRNA transport and subsequent translation at the synapse will ultimately generate important novel RNA-based tools in the near future that will allow us to hopefully treat some of these devastating diseases.
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Affiliation(s)
- Marco Tolino
- Center for Brain Research, Medical University of Vienna, Vienna, Austria
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Milev MP, Ravichandran M, Khan MF, Schriemer DC, Mouland AJ. Characterization of staufen1 ribonucleoproteins by mass spectrometry and biochemical analyses reveal the presence of diverse host proteins associated with human immunodeficiency virus type 1. Front Microbiol 2012; 3:367. [PMID: 23125841 PMCID: PMC3486646 DOI: 10.3389/fmicb.2012.00367] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2012] [Accepted: 09/27/2012] [Indexed: 12/02/2022] Open
Abstract
The human immunodeficiency virus type 1 (HIV-1) unspliced, 9 kb genomic RNA (vRNA) is exported from the nucleus for the synthesis of viral structural proteins and enzymes (Gag and Gag/Pol) and is then transported to sites of virus assembly where it is packaged into progeny virions. vRNA co-exists in the cytoplasm in the context of the HIV-1 ribonucleoprotein (RNP) that is currently defined by the presence of Gag and several host proteins including the double-stranded RNA-binding protein, Staufen1. In this study we isolated Staufen1 RNP complexes derived from HIV-1-expressing cells using tandem affinity purification and have identified multiple host protein components by mass spectrometry. Four viral proteins, including Gag, Gag/Pol, Env and Nef as well as >200 host proteins were identified in these RNPs. Moreover, HIV-1 induces both qualitative and quantitative differences in host protein content in these RNPs. 22% of Staufen1-associated factors are virion-associated suggesting that the RNP could be a vehicle to achieve this. In addition, we provide evidence on how HIV-1 modulates the composition of cytoplasmic Staufen1 RNPs. Biochemical fractionation by density gradient analyses revealed new facets on the assembly of Staufen1 RNPs. The assembly of dense Staufen1 RNPs that contain Gag and several host proteins were found to be entirely RNA-dependent but their assembly appeared to be independent of Gag expression. Gag-containing complexes fractionated into a lighter and another, more dense pool. Lastly, Staufen1 depletion studies demonstrated that the previously characterized Staufen1 HIV-1-dependent RNPs are most likely aggregates of smaller RNPs that accumulate at juxtanuclear domains. The molecular characterization of Staufen1 HIV-1 RNPs will offer important information on virus-host cell interactions and on the elucidation of the function of these RNPs for the transport of Gag and the fate of the unspliced vRNA in HIV-1-producing cells.
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Affiliation(s)
- Miroslav P Milev
- HIV-1 Trafficking Laboratory, Lady Davis Institute at the Jewish General Hospital Montréal, QC, Canada ; Division of Experimental Medicine, Department of Medicine, McGill University Montreal, QC, Canada
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The 21.5-kDa isoform of myelin basic protein has a non-traditional PY-nuclear-localization signal. Biochem Biophys Res Commun 2012; 422:670-5. [PMID: 22609403 DOI: 10.1016/j.bbrc.2012.05.051] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2012] [Accepted: 05/09/2012] [Indexed: 12/16/2022]
Abstract
The predominant 18.5-kDa classic myelin basic protein (MBP) is mainly responsible for compaction of the myelin sheath in the central nervous system, but is multifunctional, having numerous interactions with Ca(2+)-calmodulin, actin, tubulin, and SH3-domains, and can tether these proteins to a lipid membrane in vitro. The full-length 21.5-kDa MBP isoform has an additional 26 residues encoded by exon-II of the classic gene, which causes it to be trafficked to the nucleus of oligodendrocytes (OLGs). We have performed site-directed mutagenesis of selected residues within this segment in red fluorescent protein (RFP)-tagged constructs, which were then transfected into the immortalized N19-OLG cell line to view protein localization using epifluorescence microscopy. We found that 21.5-kDa MBP contains two non-traditional PY-nuclear-localization signals, and that arginine and lysine residues within these motifs were involved in subcellular trafficking of this protein to the nucleus, where it may have functional roles during myelinogenesis.
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Abstract
RNA transport granules deliver translationally repressed mRNAs to synaptic sites in dendrites, where synaptic activity promotes their localized translation. Although the identity of many proteins that make up the neuronal granules is known, the stoichiometry of their core component, the mRNA, is poorly understood. By imaging nine different dendritically localized mRNA species with single-molecule sensitivity and subdiffraction-limit resolution in cultured hippocampal neurons, we show that two molecules of the same or different mRNA species do not assemble in common structures. Even mRNA species with a common dendritic localization element, the sequence that is believed to mediate the incorporation of these mRNAs into common complexes, do not colocalize. These results suggest that mRNA molecules traffic to the distal reaches of dendrites singly and independently of others, a model that permits a finer control of mRNA content within a synapse for synaptic plasticity.
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Smith GST, Homchaudhuri L, Boggs JM, Harauz G. Classic 18.5- and 21.5-kDa myelin basic protein isoforms associate with cytoskeletal and SH3-domain proteins in the immortalized N19-oligodendroglial cell line stimulated by phorbol ester and IGF-1. Neurochem Res 2012; 37:1277-95. [PMID: 22249765 DOI: 10.1007/s11064-011-0700-2] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2011] [Revised: 11/17/2011] [Accepted: 12/31/2011] [Indexed: 01/10/2023]
Abstract
The 18.5-kDa classic myelin basic protein (MBP) is an intrinsically disordered protein arising from the Golli (Genes of Oligodendrocyte Lineage) gene complex and is responsible for compaction of the myelin sheath in the central nervous system. This MBP splice isoform also has a plethora of post-translational modifications including phosphorylation, deimination, methylation, and deamidation, that reduce its overall net charge and alter its protein and lipid associations within oligodendrocytes (OLGs). It was originally thought that MBP was simply a structural component of myelin; however, additional investigations have demonstrated that MBP is multi-functional, having numerous protein-protein interactions with Ca²⁺-calmodulin, actin, tubulin, and proteins with SH3-domains, and it can tether these proteins to a lipid membrane in vitro. Here, we have examined cytoskeletal interactions of classic 18.5-kDa MBP, in vivo, using early developmental N19-OLGs transfected with fluorescently-tagged MBP, actin, tubulin, and zonula occludens 1 (ZO-1). We show that MBP redistributes to distinct 'membrane-ruffled' regions of the plasma membrane where it co-localizes with actin and tubulin, and with the SH3-domain-containing proteins cortactin and ZO-1, when stimulated with PMA, a potent activator of the protein kinase C pathway. Moreover, using phospho-specific antibody staining, we show an increase in phosphorylated Thr98 MBP (human sequence numbering) in membrane-ruffled OLGs. Previously, Thr98 phosphorylation of MBP has been shown to affect its conformation, interactions with other proteins, and tethering of other proteins to the membrane in vitro. Here, MBP and actin were also co-localized in new focal adhesion contacts induced by IGF-1 stimulation in cells grown on laminin-2. This study supports a role for classic MBP isoforms in cytoskeletal and other protein-protein interactions during membrane and cytoskeletal remodeling in OLGs.
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Affiliation(s)
- Graham S T Smith
- Department of Molecular and Cellular Biology, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada
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33
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Smith GS, De Avila M, Paez PM, Spreuer V, Wills MK, Jones N, Boggs JM, Harauz G. Proline substitutions and threonine pseudophosphorylation of the SH3 ligand of 18.5-kDa myelin basic protein decrease its affinity for the Fyn-SH3 domain and alter process development and protein localization in oligodendrocytes. J Neurosci Res 2012; 90:28-47. [PMID: 21887699 PMCID: PMC3527418 DOI: 10.1002/jnr.22733] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2011] [Revised: 06/02/2011] [Accepted: 06/06/2011] [Indexed: 12/28/2022]
Abstract
The developmentally regulated myelin basic proteins (MBPs), which arise from the golli (gene of oligodendrocyte lineage) complex, are highly positively charged, intrinsically disordered, multifunctional proteins having several alternatively spliced isoforms and posttranslational modifications, and they play key roles in myelin compaction. The classic 18.5-kDa MBP isoform has a proline-rich region comprising amino acids 92-99 (murine sequence -T(92)PRTPPPS(99)-) that contains a minimal SH3 ligand domain. We have previously shown that 18.5-kDa MBP binds to several SH3 domains, including that of Fyn, a member of the Src family of tyrosine kinases involved in a number of signaling pathways during CNS development. To determine the physiological role of this binding as well as the role of phosphorylation of Thr92 and Thr95, in the current study we have produced several MBP variants specifically targeting phosphorylation sites and key structural regions of MBP's SH3 ligand domain. Using isothermal titration calorimetry, we have demonstrated that, compared with the wild-type protein, these variants have lower affinity for the SH3 domain of Fyn. Moreover, overexpression of N-terminal-tagged GFP versions in immortalized oligodendroglial N19 and N20.1 cell cultures results in aberrant elongation of membrane processes and increased branching complexity and inhibits the ability of MBP to decrease Ca(2+) influx. Phosphorylation of Thr92 can also cause MBP to traffic to the nucleus, where it may participate in additional protein-protein interactions. Coexpression of MBP with a constitutively active form of Fyn kinase resulted in membrane process elaboration, a phenomenon that was abolished by point amino acid substitutions in MBP's SH3 ligand domain. These results suggest that MBP's SH3 ligand domain plays a key role in intracellular protein interactions in vivo and may be required for proper membrane elaboration of developing oligodendrocytes and, further, that phosphorylation of Thr92 and Thr95 can regulate this function.
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Affiliation(s)
- Graham S.T. Smith
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - Miguel De Avila
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - Pablo M. Paez
- Semel Institute for Neuroscience and Human Behavior, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California
| | - Vilma Spreuer
- Semel Institute for Neuroscience and Human Behavior, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California
| | - Melanie K.B. Wills
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - Nina Jones
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - Joan M. Boggs
- Molecular Structure and Function, Hospital for Sick Children, and Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada
| | - George Harauz
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
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Roig B, Moyano S, Martorell L, Costas J, Vilella E. The discoidin domain receptor 1 gene has a functional A2RE sequence. J Neurochem 2011; 120:408-18. [PMID: 22077590 DOI: 10.1111/j.1471-4159.2011.07580.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Discoidin domain receptor 1 (DDR1) is expressed in myelin oligodendrocytes and co-localizes with myelin basic protein (MBP). Alternative splicing of DDR1 generates five isoforms designated DDR1a-e. The MBP mRNA contains an hnRNP A2 response element (A2RE) sequence that is recognized by heterogeneous nuclear ribonucleoprotein (hnRNP) A2/B1, which is responsible for transport of the MBP mRNA to oligodendrocyte processes. We hypothesized that DDR1 could have a functional A2RE sequence. By in silico analysis, we identified an A2RE-like sequence in the human DDR1 mRNA. We observed nuclear and dendrite cytoplasmic immunofluorescence, indicating that DDR1 and hnRNP A2/B1 co-localize in human oligodendrocytes and in differentiated HOG16 cells. The A2RE-like sequence of DDR1 contains the single nucleotide polymorphism rs2267641, and we found that in the human brain, the minor allele is associated with lower and higher levels DDR1b and DDR1c mRNA expression, respectively. Moreover, a positive correlation between DDR1c and the myelin genes myelin-associated glycoprotein and oligodendrocyte lineage transcription factor 2 was found. Differentiated HOG16 cells transfected with an hnRNP A2/B1 siRNA simultaneously show a decrease and an increase in the DDR1c and DDR1b mRNA expression levels, respectively, which was accompanied by a decrease in DDR1 protein levels at the cytoplasmic edges. These results suggest that the DDR1 A2RE sequence is functionally involved in the hnRNP A2/B1-mediated splicing and transport of the DDR1c mRNA.
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Affiliation(s)
- Barbara Roig
- Hospital Universitari Psiquiàtric Institut Pere Mata, IISPV, Universitat Rovira i Virgili, Reus, Spain.
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35
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Kunde SA, Musante L, Grimme A, Fischer U, Muller E, Wanker EE, Kalscheuer VM. The X-chromosome-linked intellectual disability protein PQBP1 is a component of neuronal RNA granules and regulates the appearance of stress granules. Hum Mol Genet 2011; 20:4916-31. [DOI: 10.1093/hmg/ddr430] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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36
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Spatial segregation of BDNF transcripts enables BDNF to differentially shape distinct dendritic compartments. Proc Natl Acad Sci U S A 2011; 108:16813-8. [PMID: 21933955 DOI: 10.1073/pnas.1014168108] [Citation(s) in RCA: 152] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
BDNF is produced from many transcripts that display distinct subcellular localization, suggesting that spatially restricted effects occur as a function of genetic and physiological regulation. Different BDNF 5' splice variants give a restricted localization in the cell body or the proximal and distal compartments of dendrites; however, the functional consequences are not known. Silencing individual endogenous transcripts or overexpressing BDNF-GFP transcripts in cultured neurons demonstrated that whereas some transcripts (1 and 4) selectively affected proximal dendrites, others (2C and 6) affected distal dendrites. Moreover, segregation of BDNF transcripts resulted in a highly selective activation of the BDNF TrkB receptor. These studies indicate that spatial segregation of BDNF transcripts enables BDNF to differentially shape distinct dendritic compartments.
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37
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Sinnamon JR, Czaplinski K. mRNA trafficking and local translation: the Yin and Yang of regulating mRNA localization in neurons. Acta Biochim Biophys Sin (Shanghai) 2011; 43:663-70. [PMID: 21749992 DOI: 10.1093/abbs/gmr058] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Localized translation and the requisite trafficking of the mRNA template play significant roles in the nervous system including the establishment of dendrites and axons, axon path-finding, and synaptic plasticity. We provide a brief review on the regulation of localizing mRNA in mammalian neurons through critical post-translational modifications of the factors involved. These examples highlight the relationship between mRNA trafficking and the translational regulation of trafficked mRNAs and provide insight into how extracellular signals target these events during signal transduction.
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Affiliation(s)
- John R Sinnamon
- Program in Neuroscience, Stony Brook University, NY 11794, USA
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38
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Lebeau G, Miller LC, Tartas M, McAdam R, Laplante I, Badeaux F, DesGroseillers L, Sossin WS, Lacaille JC. Staufen 2 regulates mGluR long-term depression and Map1b mRNA distribution in hippocampal neurons. Learn Mem 2011; 18:314-26. [PMID: 21508097 DOI: 10.1101/lm.2100611] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The two members of the Staufen family of RNA-binding proteins, Stau1 and Stau2, are present in distinct ribonucleoprotein complexes and associate with different mRNAs. Stau1 is required for protein synthesis-dependent long-term potentiation (L-LTP) in hippocampal pyramidal cells. However, the role of Stau2 in synaptic plasticity remains unexplored. We found that unlike Stau1, Stau2 is not required for L-LTP. In contrast, Stau2, but not Stau1, is necessary for DHPG-induced protein synthesis-dependent long-term depression (mGluR-LTD). While Stau2 is involved in early development of spines, its down-regulation does not alter spine morphology or spontaneous miniature synaptic activity in older cultures where LTD occurs. In addition, Stau2, but not Stau1, knockdown reduces the dendritic localization of Map1b mRNA, a specific transcript involved in mGluR-LTD. Moreover, mGluR stimulation with DHPG induces Map1b, but not Map2, mRNA dissociation from mRNA granules containing Stau2 and the ribosomal protein P0. This dissociation was not observed in cells in which Stau2 was depleted. Finally, Stau2 knockdown reduces basal Map1b protein expression in dendrites and prevents DHPG-induced increases in dendritic Map1b protein level. We suggest a role for Stau2 in the generation and regulation of Map1b mRNA containing granules that are required for mGluR-LTD.
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Affiliation(s)
- Geneviève Lebeau
- Département de physiologie, GRSNC, Université de Montréal, Montréal, Québec H3C 3J7, Canada
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39
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Identification of a gene regulatory network necessary for the initiation of oligodendrocyte differentiation. PLoS One 2011; 6:e18088. [PMID: 21490970 PMCID: PMC3072388 DOI: 10.1371/journal.pone.0018088] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2010] [Accepted: 02/20/2011] [Indexed: 11/19/2022] Open
Abstract
Differentiation of oligodendrocyte progenitor cells (OPCs) into mature oligodendrocytes requires extensive changes in gene expression, which are partly mediated by post-translational modifications of nucleosomal histones. An essential modification for oligodendrocyte differentiation is the removal of acetyl groups from lysine residues which is catalyzed by histone deacetylases (HDACs). The transcriptional targets of HDAC activity within OPCs however, have remained elusive and have been identified in this study by interrogating the oligodendrocyte transcriptome. Using a novel algorithm that allows clustering of gene transcripts according to expression kinetics and expression levels, we defined major waves of co-regulated genes. The initial overall decrease in gene expression was followed by the up-regulation of genes involved in lipid metabolism and myelination. Functional annotation of the down-regulated gene clusters identified transcripts involved in cell cycle regulation, transcription, and RNA processing. To define whether these genes were the targets of HDAC activity, we cultured rat OPCs in the presence of trichostatin A (TSA), an HDAC inhibitor previously shown to inhibit oligodendrocyte differentiation. By overlaying the defined oligodendrocyte transcriptome with the list of 'TSA sensitive' genes, we determined that a high percentage of 'TSA sensitive' genes are part of a normal program of oligodendrocyte differentiation. TSA treatment increased the expression of genes whose down-regulation occurs very early after induction of OPC differentiation, but did not affect the expression of genes with a slower kinetic. Among the increased 'TSA sensitive' genes we detected several transcription factors including Id2, Egr1, and Sox11, whose down-regulation is critical for OPC differentiation. Thus, HDAC target genes include clusters of co-regulated genes involved in transcriptional repression. These results support a de-repression model of oligodendrocyte lineage progression that relies on the concurrent down-regulation of several inhibitors of differentiation.
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40
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Abstract
RNA localisation is an important mode of delivering proteins to their site of function. Cis-acting signals within the RNAs, which can be thought of as zip-codes, determine the site of localisation. There are few examples of fully characterised RNA signals, but the signals are thought to be defined through a combination of primary, secondary, and tertiary structures. In this chapter, we describe a selection of computational methods for predicting RNA secondary structure, identifying localisation signals, and searching for similar localisation signals on a genome-wide scale. The chapter is aimed at the biologist rather than presenting the details of each of the individual methods.
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Doukhanine E, Gavino C, Haines JD, Almazan G, Richard S. The QKI-6 RNA binding protein regulates actin-interacting protein-1 mRNA stability during oligodendrocyte differentiation. Mol Biol Cell 2010; 21:3029-40. [PMID: 20631256 PMCID: PMC2929996 DOI: 10.1091/mbc.e10-04-0305] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The quaking viable (qk(v)) mice represent an animal model of dysmyelination. The absence of expression of the QKI-6 and QKI-7 cytoplasmic isoforms in oligodendrocytes (OLs) during CNS myelination causes the qk(v) mouse phenotype. The QKI RNA-binding proteins are known to regulate RNA metabolism of cell cycle proteins and myelin components in OLs; however, little is known of their role in reorganizing the cytoskeleton or process outgrowth during OL maturation and differentiation. Here, we identify the actin-interacting protein (AIP)-1 mRNA as a target of QKI-6 by using two-dimensional differential gel electrophoresis. The AIP-1 mRNA contains a consensus QKI response element within its 3'-untranslated region that, when bound by QKI-6, decreases the half-life of the AIP-1 mRNA. Although the expression of QKI-6 is known to increase during OL differentiation and CNS myelination, we show that this increase is paralleled with a corresponding decrease in AIP-1 expression in rat brains. Furthermore, qk(v)/qk(v) mice that lack QKI-6 and QKI-7 within its OLs had an increased level of AIP-1 in OLs. Moreover, primary rat OL precursors harboring an AIP-1 small interfering RNA display defects in OL process outgrowth. Our findings suggest that the QKI RNA-binding proteins regulate OL differentiation by modulating the expression of AIP-1.
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Affiliation(s)
- Evgueni Doukhanine
- Terry Fox Molecular Oncology Group, Bloomfield Center for Research on Aging, Lady Davis Institute for Medical Research and Departments of Oncology and Medicine, McGill University, Montréal, Québec H3T1E2, Canada
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42
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Francone VP, Ifrim MF, Rajagopal C, Leddy CJ, Wang Y, Carson JH, Mains RE, Eipper BA. Signaling from the secretory granule to the nucleus: Uhmk1 and PAM. Mol Endocrinol 2010; 24:1543-58. [PMID: 20573687 DOI: 10.1210/me.2009-0381] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Neurons and endocrine cells package peptides in secretory granules (large dense-core vesicles) for storage and stimulated release. Studies of peptidylglycine alpha-amidating monooxygenase (PAM), an essential secretory granule membrane enzyme, revealed a pathway that can relay information from secretory granules to the nucleus, resulting in alterations in gene expression. The cytosolic domain (CD) of PAM, a type 1 membrane enzyme essential for the production of amidated peptides, is basally phosphorylated by U2AF homology motif kinase 1 (Uhmk1) and other Ser/Thr kinases. Proopiomelanocortin processing in AtT-20 corticotrope tumor cells was increased when Uhmk1 expression was reduced. Uhmk1 was concentrated in the nucleus, but cycled rapidly between nucleus and cytosol. Endoproteolytic cleavage of PAM releases a soluble CD fragment that localizes to the nucleus. Localization of PAM-CD to the nucleus was decreased when PAM-CD with phosphomimetic mutations was examined and when active Uhmk1 was simultaneously overexpressed. Membrane-tethering Uhmk1 did not eliminate its ability to exclude PAM-CD from the nucleus, suggesting that cytosolic Uhmk1 could cause this response. Microarray analysis demonstrated the ability of PAM to increase expression of a small subset of genes, including aquaporin 1 (Aqp1) in AtT-20 cells. Aqp1 mRNA levels were higher in wild-type mice than in mice heterozygous for PAM, indicating that a similar relationship occurs in vivo. Expression of PAM-CD also increased Aqp1 levels whereas expression of Uhmk1 diminished Aqp1 expression. The outlines of a pathway that ties secretory granule metabolism to the transcriptome are thus apparent.
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Affiliation(s)
- Victor P Francone
- Department of Neuroscience, University of Connecticut Health Center, Farmington, Connecticut 06032, USA
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43
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A novel 65 kDa RNA-binding protein in squid presynaptic terminals. Neuroscience 2010; 166:73-83. [DOI: 10.1016/j.neuroscience.2009.12.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2009] [Accepted: 12/01/2009] [Indexed: 11/22/2022]
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44
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Bauer NG, Richter-Landsberg C, Ffrench-Constant C. Role of the oligodendroglial cytoskeleton in differentiation and myelination. Glia 2010; 57:1691-705. [PMID: 19455583 DOI: 10.1002/glia.20885] [Citation(s) in RCA: 141] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Oligodendrocytes, the myelin-forming cells of the central nervous system, are in culture characterized by an elaborate process network, terminating in flat membranous sheets that are rich in myelin-specific proteins and lipids, and spirally wrap axons forming a compact insulating layer in vivo. By analogy with other cell types, maintenance and stability of these processes, as well as the formation of the myelin sheath, likely rely on a pronounced cytoskeleton consisting of microtubules and microfilaments. While the specialized process of wrapping and compaction forming the myelin sheath is not well understood, considerably more is known about how cytoskeletal organization is mediated by extracellular and intracellular signals and other interaction partners during oligodendrocyte differentiation and myelination. Here, we review the current state of knowledge on the role of the oligodendrocyte cytoskeleton in differentiation with an emphasis on signal transduction mechanisms and will attempt to draw out implications for its significance in myelination.
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Affiliation(s)
- Nina G Bauer
- MRC Centre for Regenerative Medicine, Centre for Multiple Sclerosis Research, The University of Edinburgh, Queen's Medical Research Institute, Edinburgh EH16 4TJ, United Kingdom.
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45
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Bestman JE, Cline HT. The Relationship between Dendritic Branch Dynamics and CPEB-Labeled RNP Granules Captured in Vivo. Front Neural Circuits 2009; 3:10. [PMID: 19753328 PMCID: PMC2742666 DOI: 10.3389/neuro.04.010.2009] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2009] [Accepted: 08/15/2009] [Indexed: 11/13/2022] Open
Abstract
Cytoplasmic Polyadenylation Element Binding protein (CPEB) is an RNA binding protein involved in dendritic delivery of mRNA and activity-dependent, polyadenylation-induced translation of mRNAs in the dendritic arbor. CPEB affects learning and memory and impacts neuronal morphological and synaptic plasticity. In neurons, CPEB is concentrated in ribonucleoprotein (RNP) granules that distribute throughout the dendritic arbor and localize near synapses, suggesting that the trafficking of RNP granules is important for CPEB function. We tagged full-length CPEB and an inactive mutant CPEB with fluorescent proteins, then imaged rapid dendritic branch dynamics and RNP distribution using two-photon time-lapse microscopy of neurons in the optic tectum of living Xenopus laevis tadpoles. Though the inactive CPEB mutant transports mRNA in the dendritic arbor, its expression interferes with CPEB-dependent translation because it is incapable of activity-triggered mRNA polyadenylation. In dendrites, the distributions of the active and inactive CPEB-containing RNP granules do not differ; the RNP granules are dense and their positions do not correlate with sites of rapid dendritic branch dynamics or the eventual fate of the dendritic branches. Because CPEB's sensitivity to activity-dependent signaling does not alter its dendritic distribution, it indicates that active sites in the dendritic arbor are not targeted for RNP granule localization. Nevertheless, inactive CPEB accumulates in granules in terminal dendritic branches, supporting the hypothesis that upon activation CPEB and its mRNA cargo are released from granules and are then available for dendritic translation.
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Affiliation(s)
- Jennifer E Bestman
- Department of Cell Biology, The Scripps Research Institute La Jolla, CA, USA
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Post-transcriptional regulation of myelin formation. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2008; 1779:486-94. [PMID: 18590840 DOI: 10.1016/j.bbagrm.2008.06.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2008] [Revised: 05/15/2008] [Accepted: 06/03/2008] [Indexed: 12/21/2022]
Abstract
Myelin is a specialized structure of the nervous system that both enhances electrical conductance and protects neurons from degeneration. In the central nervous system, extensively polarized oligodendrocytes form myelin by wrapping cellular processes in a spiral pattern around neuronal axons. Myelin formation requires the oligodendrocyte to regulate gene expression in response to changes in its extracellular environment. Because these changes occur at a distance from the cell body, post-transcriptional control of gene expression allows the cell to fine-tune its response. Here, we review the RNA-binding proteins that control myelin formation in the brain, highlighting the molecular mechanisms by which they control gene expression and drawing parallels from studies in other cell types.
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