1
|
Detering NT, Schüning T, Hensel N, Claus P. The phospho-landscape of the survival of motoneuron protein (SMN) protein: relevance for spinal muscular atrophy (SMA). Cell Mol Life Sci 2022; 79:497. [PMID: 36006469 PMCID: PMC11071818 DOI: 10.1007/s00018-022-04522-9] [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: 03/21/2022] [Revised: 07/27/2022] [Accepted: 08/09/2022] [Indexed: 11/03/2022]
Abstract
Spinal muscular atrophy (SMA) is caused by low levels of the survival of motoneuron (SMN) Protein leading to preferential degeneration of lower motoneurons in the ventral horn of the spinal cord and brain stem. However, the SMN protein is ubiquitously expressed and there is growing evidence of a multisystem phenotype in SMA. Since a loss of SMN function is critical, it is important to decipher the regulatory mechanisms of SMN function starting on the level of the SMN protein itself. Posttranslational modifications (PTMs) of proteins regulate multiple functions and processes, including activity, cellular trafficking, and stability. Several PTM sites have been identified within the SMN sequence. Here, we map the identified SMN PTMs highlighting phosphorylation as a key regulator affecting localization, stability and functions of SMN. Furthermore, we propose SMN phosphorylation as a crucial factor for intracellular interaction and cellular distribution of SMN. We outline the relevance of phosphorylation of the spinal muscular atrophy (SMA) gene product SMN with regard to basic housekeeping functions of SMN impaired in this neurodegenerative disease. Finally, we compare SMA patient mutations with putative and verified phosphorylation sites. Thus, we emphasize the importance of phosphorylation as a cellular modulator in a clinical perspective as a potential additional target for combinatorial SMA treatment strategies.
Collapse
Affiliation(s)
- Nora Tula Detering
- SMATHERIA gGmbH - Non-Profit Biomedical Research Institute, Hannover, Germany
- Center for Systems Neuroscience (ZSN), Hannover, Germany
| | - Tobias Schüning
- SMATHERIA gGmbH - Non-Profit Biomedical Research Institute, Hannover, Germany
- Center for Systems Neuroscience (ZSN), Hannover, Germany
| | - Niko Hensel
- Ottawa Hospital Research Institute (OHRI), Ottawa, Canada
- Center for Systems Neuroscience (ZSN), Hannover, Germany
| | - Peter Claus
- SMATHERIA gGmbH - Non-Profit Biomedical Research Institute, Hannover, Germany.
- Center for Systems Neuroscience (ZSN), Hannover, Germany.
| |
Collapse
|
2
|
Sluzalska KD, Slawski J, Sochacka M, Lampart A, Otlewski J, Zakrzewska M. Intracellular partners of fibroblast growth factors 1 and 2 - implications for functions. Cytokine Growth Factor Rev 2020; 57:93-111. [PMID: 32475760 DOI: 10.1016/j.cytogfr.2020.05.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2020] [Revised: 05/04/2020] [Accepted: 05/07/2020] [Indexed: 01/01/2023]
Abstract
Fibroblast growth factors 1 and 2 (FGF1 and FGF2) are mainly considered as ligands of surface receptors through which they regulate a broad spectrum of biological processes. They are secreted in non-canonical way and, unlike other growth factors, they are able to translocate from the endosome to the cell interior. These unique features, as well as the role of the intracellular pool of FGF1 and FGF2, are far from being fully understood. An increasing number of reports address this problem, focusing on the intracellular interactions of FGF1 and 2. Here, we summarize the current state of knowledge of the FGF1 and FGF2 binding partners inside the cell and the possible role of these interactions. The partner proteins are grouped according to their function, including proteins involved in secretion, cell signaling, nucleocytoplasmic transport, binding and processing of nucleic acids, ATP binding, and cytoskeleton assembly. An in-depth analysis of the network of these binding partners could indicate novel, non-classical functions of FGF1 and FGF2 and uncover an additional level of a fine control of the well-known FGF-regulated cellular processes.
Collapse
Affiliation(s)
- Katarzyna Dominika Sluzalska
- Department of Protein Engineering, Faculty of Biotechnology, University of Wroclaw, ul. F. Joliot-Curie 14a, 50-383 Wroclaw, Poland
| | - Jakub Slawski
- Department of Biophysics, Faculty of Biotechnology, University of Wroclaw, ul. F. Joliot-Curie 14a, 50-383 Wroclaw, Poland
| | - Martyna Sochacka
- Department of Protein Engineering, Faculty of Biotechnology, University of Wroclaw, ul. F. Joliot-Curie 14a, 50-383 Wroclaw, Poland
| | - Agata Lampart
- Department of Protein Engineering, Faculty of Biotechnology, University of Wroclaw, ul. F. Joliot-Curie 14a, 50-383 Wroclaw, Poland
| | - Jacek Otlewski
- Department of Protein Engineering, Faculty of Biotechnology, University of Wroclaw, ul. F. Joliot-Curie 14a, 50-383 Wroclaw, Poland
| | - Malgorzata Zakrzewska
- Department of Protein Engineering, Faculty of Biotechnology, University of Wroclaw, ul. F. Joliot-Curie 14a, 50-383 Wroclaw, Poland.
| |
Collapse
|
3
|
Figueroa V, Rodríguez MS, Lanari C, Lamb CA. Nuclear action of FGF members in endocrine-related tissues and cancer: Interplay with steroid receptor pathways. Steroids 2019; 152:108492. [PMID: 31513818 DOI: 10.1016/j.steroids.2019.108492] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Revised: 08/27/2019] [Accepted: 09/05/2019] [Indexed: 01/09/2023]
Abstract
Dysregulation of the fibroblast growth factors/fibroblast growth factor receptor (FGF/FGFR) pathway has been implicated in a wide range of human disorders and several members have been localized in the nuclear compartment. Hormone-activated steroid receptors or ligand independent activated receptors form nuclear complexes that activate gene transcription. This review aims to highlight the interplay between the steroid receptor and the FGF/FGFR pathways and focuses on the current knowledge on nuclear action of FGF members in endocrine-related tissues and cancer. The nuclear trafficking and targets of FGF/FGFR members and the available evidence on the interplay with steroid hormones and receptors is described. Finally, the data on aberrant FGF/FGFR signaling is summarized and the nuclear action of FGF members on endocrine resistant breast cancer is highlighted. Identifying the mechanisms underlying FGF-induced endocrine resistance will be important to understand how to efficiently target endocrine-related diseases and even enhance or restore endocrine sensitivity in hormone receptor positive tumors.
Collapse
Affiliation(s)
- Virginia Figueroa
- Instituto de Biología y Medicina Experimental (IBYME-CONICET), Vuelta de Obligado 2490, Buenos Aires 1428, Argentina
| | - María Sol Rodríguez
- Instituto de Biología y Medicina Experimental (IBYME-CONICET), Vuelta de Obligado 2490, Buenos Aires 1428, Argentina
| | - Claudia Lanari
- Instituto de Biología y Medicina Experimental (IBYME-CONICET), Vuelta de Obligado 2490, Buenos Aires 1428, Argentina
| | - Caroline Ana Lamb
- Instituto de Biología y Medicina Experimental (IBYME-CONICET), Vuelta de Obligado 2490, Buenos Aires 1428, Argentina.
| |
Collapse
|
4
|
Boshoff EL, Fletcher EJR, Duty S. Fibroblast growth factor 20 is protective towards dopaminergic neurons in vivo in a paracrine manner. Neuropharmacology 2018; 137:156-163. [PMID: 29698669 PMCID: PMC6063078 DOI: 10.1016/j.neuropharm.2018.04.017] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Revised: 04/18/2018] [Accepted: 04/19/2018] [Indexed: 01/01/2023]
Abstract
Neuroprotective strategies are an unmet medical need for Parkinson's disease. Fibroblast growth factor 20 (FGF20) enhances survival of cultured dopaminergic neurons but little is known about its in vivo potential. We set out to examine whether manipulation of the FGF20 system affected nigrostriatal tract integrity in rats, to identify which fibroblast growth factor receptors (FGFRs) might reside on dopaminergic neurons and to discover the source of endogenous FGF20 in the substantia nigra (SN). Male Sprague Dawley rats were subject to a partial 6-OHDA lesion alongside treatment with exogenous FGF20 or an FGFR antagonist. Behavioural readouts and tyrosine-hydroxylase (TH) immunohistochemistry were used to evaluate nigrostriatal tract integrity. Fluorescent immunohistochemistry was used to examine FGFR subtype expression on TH-positive dopamine neurons and FGF20 cellular localisation within the SN. FGF20 (2.5 μg/day) significantly protected TH-positive cells in the SN and terminals in the striatum, while reducing the development of motor asymmetry at 5, 8 and 11 days post lesion. Conversely, the FGFR antagonist PD173074 (2 mg/kg) significantly worsened both the 6-OHDA lesion and resultant motor asymmetry. Within the SN, TH-positive cells expressed FGFR1, 3 and 4 while FGF20 co-localised with GFAP-positive astrocytes. In conclusion, FGF20 protects dopaminergic neurons in vivo, an action likely mediated through activation of FGFRs1, 3 or 4 found on these neurons. Given FGF20 is localised to astrocytes in the adult SN, endogenous FGF20 provides its protection of dopamine neurons through a paracrine action. Boosting the endogenous FGF20 production might offer potential as a future therapeutic strategy in Parkinson's disease. FGF20 infusion protects against a partial 6-OHDA nigrostriatal tract lesion in rats. Dopaminergic cells in the SNc express FGFR1, 3 and 4 upon which FGF20 can act. FGFR blockade exacerbates a partial 6-OHDA nigrostriatal tract lesion in rats. Endogenous FGF20 is expressed by astrocytes in the SN, not by dopaminergic neurons. Endogenous FGF20 most likely provides protection in a paracrine manner.
Collapse
Affiliation(s)
- Eugene L Boshoff
- King's College London, Institute of Psychiatry, Psychology & Neuroscience, Wolfson Centre for Age-Related Diseases, Guy's Campus, London SE1 1UL, UK
| | - Edward J R Fletcher
- King's College London, Institute of Psychiatry, Psychology & Neuroscience, Wolfson Centre for Age-Related Diseases, Guy's Campus, London SE1 1UL, UK
| | - Susan Duty
- King's College London, Institute of Psychiatry, Psychology & Neuroscience, Wolfson Centre for Age-Related Diseases, Guy's Campus, London SE1 1UL, UK.
| |
Collapse
|
5
|
Förthmann B, Grothe C, Claus P. A nuclear odyssey: fibroblast growth factor-2 (FGF-2) as a regulator of nuclear homeostasis in the nervous system. Cell Mol Life Sci 2015; 72:1651-62. [PMID: 25552245 PMCID: PMC11113852 DOI: 10.1007/s00018-014-1818-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Revised: 12/10/2014] [Accepted: 12/19/2014] [Indexed: 01/07/2023]
Abstract
Nuclear localization of classical growth factors is a well-known phenomenon but still remains a molecular and cellular conundrum. Fibroblast growth factor-2 (FGF-2) is an excellent example of a protein which functions as an extracellular molecule involved in canonical receptor tyrosine kinase signaling as well as displaying intracellular functions. Paracrine and nuclear functions are two important sides of the same protein. FGF-2 is expressed in isoforms with different molecular weights from one mRNA species. In rodents, all of these isoforms become imported to the nucleus. In this review, we discuss structural and functional aspects of FGF-2 isoforms in the nervous system. The nuclear odyssey of FGF-2 is reflected by nuclear dynamics, localization to nuclear bodies such as nucleoli, binding to chromatin and engagement in various protein interactions. Recently discovered molecular partnerships of the isoforms shed light on their nuclear functions, thereby greatly extending our knowledge of the multifaceted functions of FGF-2.
Collapse
Affiliation(s)
- Benjamin Förthmann
- Department of Neuroanatomy, Institute of Neuroanatomy, Hannover Medical School, OE 4140, Carl-Neuberg-Str.1, 30625 Hannover, Germany
| | - Claudia Grothe
- Department of Neuroanatomy, Institute of Neuroanatomy, Hannover Medical School, OE 4140, Carl-Neuberg-Str.1, 30625 Hannover, Germany
- Center for Systems Neuroscience, 30625 Hannover, Germany
| | - Peter Claus
- Department of Neuroanatomy, Institute of Neuroanatomy, Hannover Medical School, OE 4140, Carl-Neuberg-Str.1, 30625 Hannover, Germany
- Center for Systems Neuroscience, 30625 Hannover, Germany
| |
Collapse
|
6
|
Förthmann B, van Bergeijk J, Lee YW, Lübben V, Schill Y, Brinkmann H, Ratzka A, Stachowiak MK, Hebert M, Grothe C, Claus P. Regulation of neuronal differentiation by proteins associated with nuclear bodies. PLoS One 2013; 8:e82871. [PMID: 24358231 PMCID: PMC3866168 DOI: 10.1371/journal.pone.0082871] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Accepted: 11/06/2013] [Indexed: 12/17/2022] Open
Abstract
Nuclear bodies are large sub-nuclear structures composed of RNA and protein molecules. The Survival of Motor Neuron (SMN) protein localizes to Cajal bodies (CBs) and nuclear gems. Diminished cellular concentration of SMN is associated with the neurodegenerative disease Spinal Muscular Atrophy (SMA). How nuclear body architecture and its structural components influence neuronal differentiation remains elusive. In this study, we analyzed the effects of SMN and two of its interaction partners in cellular models of neuronal differentiation. The nuclear 23 kDa isoform of Fibroblast Growth Factor - 2 (FGF-2(23)) is one of these interacting proteins - and was previously observed to influence nuclear bodies by destabilizing nuclear gems and mobilizing SMN from Cajal bodies (CBs). Here we demonstrate that FGF-2(23) blocks SMN-promoted neurite outgrowth, and also show that SMN disrupts FGF-2(23)-dependent transcription. Our results indicate that FGF-2(23) and SMN form an inactive complex that interferes with neuronal differentiation by mutually antagonizing nuclear functions. Coilin is another nuclear SMN binding partner and a marker protein for Cajal bodies (CBs). In addition, coilin is essential for CB function in maturation of small nuclear ribonucleoprotein particles (snRNPs). The role of coilin outside of Cajal bodies and its putative impacts in tissue differentiation are poorly defined. The present study shows that protein levels of nucleoplasmic coilin outside of CBs decrease during neuronal differentiation. Overexpression of coilin has an inhibitory effect on neurite outgrowth. Furthermore, we find that nucleoplasmic coilin inhibits neurite outgrowth independent of SMN binding revealing a new function for coilin in neuronal differentiation.
Collapse
Affiliation(s)
- Benjamin Förthmann
- Institute of Neuroanatomy, Hannover Medical School, Hannover, Germany
- Center for Systems Neuroscience, University of Veterinary Medicine Hannover, Hannover, Germany
| | | | - Yu-Wei Lee
- Department of Pathology and Anatomical Sciences, State University of New York, Buffalo, New York, United States of America
| | - Verena Lübben
- Institute of Neuroanatomy, Hannover Medical School, Hannover, Germany
| | - Yvonne Schill
- Institute of Neuroanatomy, Hannover Medical School, Hannover, Germany
| | - Hella Brinkmann
- Institute of Neuroanatomy, Hannover Medical School, Hannover, Germany
| | - Andreas Ratzka
- Institute of Neuroanatomy, Hannover Medical School, Hannover, Germany
| | - Michal K. Stachowiak
- Department of Pathology and Anatomical Sciences, State University of New York, Buffalo, New York, United States of America
| | - Michael Hebert
- Department of Biochemistry, The University of Mississippi Medical Center, Jackson, Mississippi, United States of America
| | - Claudia Grothe
- Institute of Neuroanatomy, Hannover Medical School, Hannover, Germany
- Center for Systems Neuroscience, University of Veterinary Medicine Hannover, Hannover, Germany
| | - Peter Claus
- Institute of Neuroanatomy, Hannover Medical School, Hannover, Germany
- Center for Systems Neuroscience, University of Veterinary Medicine Hannover, Hannover, Germany
- * E-mail:
| |
Collapse
|
7
|
Förthmann B, Brinkmann H, Ratzka A, Stachowiak MK, Grothe C, Claus P. Immobile survival of motoneuron (SMN) protein stored in Cajal bodies can be mobilized by protein interactions. Cell Mol Life Sci 2013; 70:2555-68. [PMID: 23334184 PMCID: PMC11113639 DOI: 10.1007/s00018-012-1242-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2012] [Revised: 11/29/2012] [Accepted: 12/10/2012] [Indexed: 12/25/2022]
Abstract
Reduced levels of survival of motoneuron (SMN) protein lead to spinal muscular atrophy, but it is still unknown how SMN protects motoneurons in the spinal cord against degeneration. In the nucleus, SMN is associated with two types of nuclear bodies denoted as gems and Cajal bodies (CBs). The 23 kDa isoform of fibroblast growth factor-2 (FGF-2(23)) is a nuclear protein that binds to SMN and destabilizes the SMN-Gemin2 complex. In the present study, we show that FGF-2(23) depletes SMN from CBs without affecting their general structure. FRAP analysis of SMN-EGFP in CBs demonstrated that the majority of SMN in CBs remained mobile and allowed quantification of fast, slow and immobile nuclear SMN populations. The potential for SMN release was confirmed by in vivo photoconversion of SMN-Dendra2, indicating that CBs concentrate immobile SMN that could have a specialized function in CBs. FGF-2(23) accelerated SMN release from CBs, accompanied by a conversion of immobile SMN into a mobile population. Furthermore, FGF-2(23) caused snRNP accumulation in CBs. We propose a model in which Cajal bodies store immobile SMN that can be mobilized by its nuclear interaction partner FGF-2(23), leading to U4 snRNP accumulation in CBs, indicating a role for immobile SMN in tri-snRNP assembly.
Collapse
Affiliation(s)
- Benjamin Förthmann
- Institute of Neuroanatomy, Hannover Medical School, OE 4140, Carl-Neuberg-Str.1, 30625 Hannover, Germany
- Center for Systems Neuroscience, 30625 Hannover, Germany
| | - Hella Brinkmann
- Institute of Neuroanatomy, Hannover Medical School, OE 4140, Carl-Neuberg-Str.1, 30625 Hannover, Germany
| | - Andreas Ratzka
- Institute of Neuroanatomy, Hannover Medical School, OE 4140, Carl-Neuberg-Str.1, 30625 Hannover, Germany
| | - Michal K. Stachowiak
- Department of Pathology and Anatomical Sciences, State University of New York, Buffalo, NY 14214 USA
| | - Claudia Grothe
- Institute of Neuroanatomy, Hannover Medical School, OE 4140, Carl-Neuberg-Str.1, 30625 Hannover, Germany
- Center for Systems Neuroscience, 30625 Hannover, Germany
| | - Peter Claus
- Institute of Neuroanatomy, Hannover Medical School, OE 4140, Carl-Neuberg-Str.1, 30625 Hannover, Germany
- Center for Systems Neuroscience, 30625 Hannover, Germany
| |
Collapse
|
8
|
Genetic circuitry of Survival motor neuron, the gene underlying spinal muscular atrophy. Proc Natl Acad Sci U S A 2013; 110:E2371-80. [PMID: 23757500 DOI: 10.1073/pnas.1301738110] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The clinical severity of the neurodegenerative disorder spinal muscular atrophy (SMA) is dependent on the levels of functional Survival Motor Neuron (SMN) protein. Consequently, current strategies for developing treatments for SMA generally focus on augmenting SMN levels. To identify additional potential therapeutic avenues and achieve a greater understanding of SMN, we applied in vivo, in vitro, and in silico approaches to identify genetic and biochemical interactors of the Drosophila SMN homolog. We identified more than 300 candidate genes that alter an Smn-dependent phenotype in vivo. Integrating the results from our genetic screens, large-scale protein interaction studies, and bioinformatic analysis, we define a unique interactome for SMN that provides a knowledge base for a better understanding of SMA.
Collapse
|
9
|
Baron O, Ratzka A, Grothe C. Fibroblast growth factor 2 regulates adequate nigrostriatal pathway formation in mice. J Comp Neurol 2013; 520:3949-61. [PMID: 22592787 DOI: 10.1002/cne.23138] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Fibroblast growth factor 2 (FGF-2) is an important neurotrophic factor that promotes survival of adult mesencephalic dopaminergic (mDA) neurons and regulates their adequate development. Since mDA neurons degenerate in Parkinson's disease, a comprehensive understanding of their development and maintenance might contribute to the development of causative therapeutic approaches. The current analysis addressed the role of FGF-2 in mDA axonal outgrowth, pathway formation, and innervation of respective forebrain targets using organotypic explant cocultures of ventral midbrain (VM) and forebrain (FB). An enhanced green fluorescent protein (EGFP) transgenic mouse strain was used for the VM explants, which allowed combining and distinguishing of individual VM and FB tissue from wildtype and FGF-2-deficient embryonic day (E)14.5 embryos, respectively. These cocultures provided a suitable model to study the role of target-derived FB and intrinsic VM-derived FGF-2. In fact, we show that loss of FGF-2 in both FB and VM results in significantly increased mDA fiber outgrowth compared to wildtype cocultures, proving a regulatory role of FGF-2 during nigrostriatal wiring. Further, we found in heterogeneous cocultures deficient for FGF-2 in FB and VM, respectively, similar phenotypes with wider fiber tracts compared to wildtype cocultures and shorter fiber outgrowth distance than cocultures completely deficient for FGF-2. Additionally, the loss of target-derived FGF-2 in FB explants resulted in decreased caudorostral glial migration. Together these findings imply an intricate interplay of target-derived and VM-derived FGF signaling, which assures an adequate nigrostriatal pathway formation and target innervation.
Collapse
Affiliation(s)
- Olga Baron
- Institute of Neuroanatomy, Hannover Medical School, 30625 Hannover, Germany
| | | | | |
Collapse
|
10
|
Baron O, Förthmann B, Lee YW, Terranova C, Ratzka A, Stachowiak EK, Grothe C, Claus P, Stachowiak MK. Cooperation of nuclear fibroblast growth factor receptor 1 and Nurr1 offers new interactive mechanism in postmitotic development of mesencephalic dopaminergic neurons. J Biol Chem 2012; 287:19827-40. [PMID: 22514272 DOI: 10.1074/jbc.m112.347831] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Experiments in mice deficient for Nurr1 or expressing the dominant-negative FGF receptor (FGFR) identified orphan nuclear receptor Nurr1 and FGFR1 as essential factors in development of mesencephalic dopaminergic (mDA) neurons. FGFR1 affects brain cell development by two distinct mechanisms. Activation of cell surface FGFR1 by secreted FGFs stimulates proliferation of neural progenitor cells, whereas direct integrative nuclear FGFR1 signaling (INFS) is associated with an exit from the cell cycle and neuronal differentiation. Both Nurr1 and INFS activate expression of neuronal genes, such as tyrosine hydroxylase (TH), which is the rate-limiting enzyme in dopamine synthesis. Here, we show that nuclear FGFR1 and Nurr1 are expressed in the nuclei of developing TH-positive cells in the embryonic ventral midbrain. Both nuclear receptors were effectively co-immunoprecipitated from the ventral midbrain of FGF-2-deficient embryonic mice, which previously showed an increase of mDA neurons and enhanced nuclear FGFR1 accumulation. Immunoprecipitation and co-localization experiments showed the presence of Nurr1 and FGFR1 in common nuclear protein complexes. Fluorescence recovery after photobleaching and chromatin immunoprecipitation experiments demonstrated the Nurr1-mediated shift of nuclear FGFR1-EGFP mobility toward a transcriptionally active population and that both Nurr1 and FGFR1 bind to a common region in the TH gene promoter. Furthermore, nuclear FGFR1 or its 23-kDa FGF-2 ligand (FGF-2(23)) enhances Nurr1-dependent activation of the TH gene promoter. Transcriptional cooperation of FGFR1 with Nurr1 was confirmed on isolated Nurr1-binding elements. The proposed INFS/Nurr1 nuclear partnership provides a novel mechanism for TH gene regulation in mDA neurons and a potential therapeutic target in neurodevelopmental and neurodegenerative disorders.
Collapse
Affiliation(s)
- Olga Baron
- Institute of Neuroanatomy, Hannover Medical School, 30625 Hannover, Germany
| | | | | | | | | | | | | | | | | |
Collapse
|
11
|
Hensel N, Ratzka A, Brinkmann H, Klimaschewski L, Grothe C, Claus P. Analysis of the fibroblast growth factor system reveals alterations in a mouse model of spinal muscular atrophy. PLoS One 2012; 7:e31202. [PMID: 22348054 PMCID: PMC3278439 DOI: 10.1371/journal.pone.0031202] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2011] [Accepted: 01/04/2012] [Indexed: 12/02/2022] Open
Abstract
The monogenetic disease Spinal Muscular Atrophy (SMA) is characterized by a progressive loss of motoneurons leading to muscle weakness and atrophy due to severe reduction of the Survival of Motoneuron (SMN) protein. Several models of SMA show deficits in neurite outgrowth and maintenance of neuromuscular junction (NMJ) structure. Survival of motoneurons, axonal outgrowth and formation of NMJ is controlled by neurotrophic factors such as the Fibroblast Growth Factor (FGF) system. Besides their classical role as extracellular ligands, some FGFs exert also intracellular functions controlling neuronal differentiation. We have previously shown that intracellular FGF-2 binds to SMN and regulates the number of a subtype of nuclear bodies which are reduced in SMA patients. In the light of these findings, we systematically analyzed the FGF-system comprising five canonical receptors and 22 ligands in a severe mouse model of SMA. In this study, we demonstrate widespread alterations of the FGF-system in both muscle and spinal cord. Importantly, FGF-receptor 1 is upregulated in spinal cord at a pre-symptomatic stage as well as in a mouse motoneuron-like cell-line NSC34 based model of SMA. Consistent with that, phosphorylations of FGFR-downstream targets Akt and ERK are increased. Moreover, ERK hyper-phosphorylation is functionally linked to FGFR-1 as revealed by receptor inhibition experiments. Our study shows that the FGF system is dysregulated at an early stage in SMA and may contribute to the SMA pathogenesis.
Collapse
Affiliation(s)
- Niko Hensel
- Institute of Neuroanatomy, Hannover Medical School, Hannover, Germany
- Center for Systems Neuroscience, Hannover, Germany
| | - Andreas Ratzka
- Institute of Neuroanatomy, Hannover Medical School, Hannover, Germany
| | - Hella Brinkmann
- Institute of Neuroanatomy, Hannover Medical School, Hannover, Germany
| | - Lars Klimaschewski
- Division of Neuroanatomy, Innsbruck Medical University, Innsbruck, Austria
| | - Claudia Grothe
- Institute of Neuroanatomy, Hannover Medical School, Hannover, Germany
- Center for Systems Neuroscience, Hannover, Germany
| | - Peter Claus
- Institute of Neuroanatomy, Hannover Medical School, Hannover, Germany
- Center for Systems Neuroscience, Hannover, Germany
- * E-mail:
| |
Collapse
|
12
|
Hebert MD. Phosphorylation and the Cajal body: modification in search of function. Arch Biochem Biophys 2010; 496:69-76. [PMID: 20193656 PMCID: PMC2850958 DOI: 10.1016/j.abb.2010.02.012] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2010] [Accepted: 02/24/2010] [Indexed: 12/25/2022]
Abstract
The Cajal body (CB) is a subnuclear domain that contains proteins and factors involved in a diverse range of activities including ribonucleoprotein maturation, histone gene transcription and telomerase assembly. Among these activities, the CBs' role in small nuclear ribonucleoprotein (snRNP) biogenesis is best characterized. Although CBs are found in plants, flies and mammals, not all cell types contain CBs. Rather, CBs are most prominent in transcriptionally active cells, such as cancer and neuronal cells. Many CB components, including the CB marker protein coilin, are phosphorylated in humans. The functional consequence of phosphorylation on CB assembly, activity and disassembly is largely unknown. Also unknown are the signaling pathways, kinases and phosphatases that act upon proteins which localize in the CB. The goal of this review is to demonstrate the need for a concerted effort towards elucidating the functional consequence of phosphorylation on CB formation and activity.
Collapse
Affiliation(s)
- Michael D Hebert
- Department of Biochemistry, The University of Mississippi Medical Center, Jackson, MS 39216-4505, USA
| |
Collapse
|
13
|
Fibroblast growth factor-2 regulates the stability of nuclear bodies. Proc Natl Acad Sci U S A 2009; 106:12747-52. [PMID: 19617559 DOI: 10.1073/pnas.0900122106] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Nuclear bodies are distinct subnuclear structures. The survival of motoneuron (SMN) gene is mutated or deleted in patients with the neurodegenerative disease spinal muscular atrophy (SMA). The gene product SMN is a marker protein for one class of nuclear bodies denoted as nuclear gems. SMN has also been found in Cajal bodies, which co-localize with gems in many cell types. Interestingly, SMA patients display a reduced number of gems. Little is known about the regulation of nuclear body formation and stabilization. We have previously shown that a nuclear isoform of the fibroblast growth factor-2 (FGF-2(23)) binds directly to SMN. In this study, we analyzed the consequences of FGF-2(23) binding to SMN with regard to nuclear body formation. On a molecular level, we showed that FGF-2(23) competed with Gemin2 (a component of the SMN complex that is necessary for gem stabilization) for binding to SMN. Down-regulation of Gemin2 by siRNA caused destabilization of SMN-positive nuclear bodies. This process is reflected in both cellular and in vivo systems by a negative regulatory function of FGF-2 in nuclear body formation: in HEK293 cells, FGF-2(23) decreased the number of SMN-positive nuclear bodies. The same effect could be observed in motoneurons of FGF-2 transgenic mice. This study demonstrates the functional role of a growth factor in the regulation of structural entities of the nucleus.
Collapse
|
14
|
Burghes AHM, Beattie CE. Spinal muscular atrophy: why do low levels of survival motor neuron protein make motor neurons sick? Nat Rev Neurosci 2009; 10:597-609. [PMID: 19584893 DOI: 10.1038/nrn2670] [Citation(s) in RCA: 537] [Impact Index Per Article: 35.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Many neurogenetic disorders are caused by the mutation of ubiquitously expressed genes. One such disorder, spinal muscular atrophy, is caused by loss or mutation of the survival motor neuron1 gene (SMN1), leading to reduced SMN protein levels and a selective dysfunction of motor neurons. SMN, together with partner proteins, functions in the assembly of small nuclear ribonucleoproteins (snRNPs), which are important for pre-mRNA splicing. It has also been suggested that SMN might function in the assembly of other ribonucleoprotein complexes. Two hypotheses have been proposed to explain the molecular dysfunction that gives rise to spinal muscular atrophy (SMA) and its specificity to a particular group of neurons. The first hypothesis states that the loss of SMN's well-known function in snRNP assembly causes an alteration in the splicing of a specific gene (or genes). The second hypothesis proposes that SMN is crucial for the transport of mRNA in neurons and that disruption of this function results in SMA.
Collapse
Affiliation(s)
- Arthur H M Burghes
- Department of Molecular and Cellular Biochemistry, The Ohio State University, Columbus, Ohio 43210, USA.
| | | |
Collapse
|
15
|
Bruns AF, Grothe C, Claus P. Fibroblast growth factor 2 (FGF-2) is a novel substrate for arginine methylation by PRMT5. Biol Chem 2009; 390:59-65. [PMID: 19086919 DOI: 10.1515/bc.2009.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Fibroblast growth factor 2 (FGF-2) is expressed in isoforms of different molecular masses from one mRNA species by alternative start of translation. The higher molecular mass isoforms (FGF-2(21) and (23)) contain an arginine-rich N-terminus organized in RG-motifs followed by the 18 kDa FGF-2 (FGF-2(18)) core which is common to all isoforms. Both isoforms localize differentially to the nucleus. Here, we analyzed the nuclear localization of FGF-2(21). Surprisingly, the lack of one RG-motif in FGF-2(21) resulted in the nucleolar distribution characteristic of FGF-2(18). We have previously shown that 23 kDa FGF-2 (FGF-2(23)) interacts specifically with the survival of motoneuron (SMN) protein, an assembly protein for small nuclear ribonucleoprotein particles. For this assembly, Sm-proteins methylated by protein arginine methyltransferase 5 (PRMT5) are required. In our study, we aimed to analyze whether FGF-2(23) is also a substrate for symmetrical methylation by PRMT5. We could confirm that both proteins exist in a common complex. Moreover, PRMT5 methylates FGF-2(23) in vitro, whereas mutated inactive PRMT5 does not. FGF-2(23) is therefore a new substrate of PRMT5. With regard to function, inhibition of methyltransferase activity in HEK293T cells leads to cytoplasmic enrichment of FGF-2, indicating the importance of arginine methylation for shuttling of FGF-2(23) to the nucleus.
Collapse
Affiliation(s)
- Alexander-Francisco Bruns
- Hannover Medical School, Institute of Neuroanatomy, OE 4140, Carl-Neuberg-Str. 1, D-30625 Hannover, Germany
| | | | | |
Collapse
|
16
|
Chlebova K, Bryja V, Dvorak P, Kozubik A, Wilcox WR, Krejci P. High molecular weight FGF2: the biology of a nuclear growth factor. Cell Mol Life Sci 2009; 66:225-35. [PMID: 18850066 PMCID: PMC3229932 DOI: 10.1007/s00018-008-8440-4] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Fibroblast growth factor 2 (FGF2) is one of the most studied growth factors to date. Most attention has been dedicated to the smallest, 18 kDa FGF2 variant that is released by cells and acts through activation of cell-surface FGF-receptor tyrosine kinases. There are, however, several higher molecular weight (HMW) variants of FGF2 that rarely leave their producing cells, are retained in the nucleus and act independently of FGF-receptors (FGFR). Despite significant evidence documenting the expression and intracellular trafficking of HMW FGF2, many important questions remain about the physiological roles and mechanisms of action of HMW FGF2. In this review, we summarize the current knowledge about the biology of HMW FGF2, its role in disease and areas for future investigation.
Collapse
Affiliation(s)
- K. Chlebova
- Institute of Experimental Biology, Masaryk University, Kotlarska 2, 61137 Brno, Czech Republic
| | - V. Bryja
- Institute of Experimental Biology, Masaryk University, Kotlarska 2, 61137 Brno, Czech Republic
- Department of Cytokinetics, Institute of Biophysics ASCR, 61265 Brno, Czech Republic
| | - P. Dvorak
- Department of Biology, Faculty of Medicine of Masaryk University, 625 00 Brno, Czech Republic
- Department of Molecular Embryology, Institute of Experimental Medicine ASCR, 625 00 Brno, Czech Republic
| | - A. Kozubik
- Institute of Experimental Biology, Masaryk University, Kotlarska 2, 61137 Brno, Czech Republic
- Department of Cytokinetics, Institute of Biophysics ASCR, 61265 Brno, Czech Republic
| | - W. R. Wilcox
- Medical Genetics Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048 USA
- Department of Pediatrics, UCLA School of Medicine, Los Angeles, CA 90095 USA
| | - P. Krejci
- Institute of Experimental Biology, Masaryk University, Kotlarska 2, 61137 Brno, Czech Republic
- Department of Cytokinetics, Institute of Biophysics ASCR, 61265 Brno, Czech Republic
- Medical Genetics Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048 USA
| |
Collapse
|
17
|
van Bergeijk J, Rydel-Könecke K, Grothe C, Claus P. The spinal muscular atrophy gene product regulates neurite outgrowth: importance of the C terminus. FASEB J 2007; 21:1492-502. [PMID: 17317728 DOI: 10.1096/fj.06-7136com] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Spinal muscular atrophy is a neurodegenerative disease accompanied by a loss of motoneurons. Either mutations or deletions in the survival of motoneuron (SMN) gene are responsible for this defect. SMN is an assembly protein for RNA-protein complexes in the nucleus and is also found in axons of neurons. However, it is unclear which dysfunctions of SMN are important for disease progression. In this study we analyzed the contributions of different SMN regions for localization and neuronal differentiation associated with outgrowth of neurites. Suppression of endogenous SMN protein levels significantly decreased the growth of neurites. Down-regulation of the interacting protein gemin2 had the opposite effect. Surprisingly, selective overexpression of the SMN C-terminal domain promoted neurite outgrowth similar to full-length protein and could rescue the SMN knock-down effects. The knock-down led to a significant change in the G-/F-actin ratio, indicating a role for SMN in actin dynamics. Therefore, our data suggest a functional role for SMN in microfilament metabolism in axons of motoneurons.
Collapse
Affiliation(s)
- Jeroen van Bergeijk
- Department of Neuroanatomy, Hannover Medical School, Carl-Neuberg-Str.1, 30625 Hannover, Germany
| | | | | | | |
Collapse
|
18
|
Sabayan B, Bagheri M, Borhani Haghighi A. Possible joint origin of restless leg syndrome (RLS) and migraine. Med Hypotheses 2007; 69:64-6. [PMID: 17258401 DOI: 10.1016/j.mehy.2006.10.060] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2006] [Accepted: 10/03/2006] [Indexed: 11/15/2022]
Abstract
Sleep disorders have been described in migraine patients. Among sleep disorders RLS has been reported in up to one-third of migraineurs. Adverse effects of anti migraine therapy by dopamine antagonists can not fully explain this association. Therefore we present the hypothesis that RLS and migraine may have a joint origin. The hypothesis is supported by: (1) the same genetic origin for migraine without aura and RLS in single Italian family on chromosome 14q21; this gene codes survival motor neuron-interacting protein 1 (SIP1) which can play role in both diseases. (2) Correlation of both RLS and migraine with fibromyalgia. (3) Alteration of cortical excitability in both migraine and RLS.
Collapse
Affiliation(s)
- Behnam Sabayan
- Student Research Committee, Nemazee Hospital, Shiraz University of Medical Sciences, Shiraz, Iran
| | | | | |
Collapse
|
19
|
Cesnulevicius K, Timmer M, Wesemann M, Thomas T, Barkhausen T, Grothe C. Nucleofection is the most efficient nonviral transfection method for neuronal stem cells derived from ventral mesencephali with no changes in cell composition or dopaminergic fate. Stem Cells 2006; 24:2776-91. [PMID: 16902196 DOI: 10.1634/stemcells.2006-0176] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Neuronal progenitor cells (NPCs) play an important role in potential regenerative therapeutic strategies for neurodegenerative diseases, such as Parkinson disease. However, survival of transplanted cells is, as yet, limited, and the identification of grafted cells in situ remains difficult. The use of NPCs could be more effective with regard to a better survival and maturation when transfected with one or more neurotrophic factors. Therefore, we investigated the possibility of transfecting mesencephalic neuronal progenitors with different constructs carrying neurotrophic factors or the expression reporters enhanced green fluorescence protein (EGFP) and red fluorescent protein (DsRed). Different techniques for transfection were compared, and the highest transfection rate of up to 47% was achieved by nucleofection. Mesencephalic neuronal progenitors survived the transfection procedure; 6 hours after transfection, viability was approximately 40%, and the transfected cells differentiated into, for example, tyrosine hydroxylase-positive neurons. Within the group of transfected cells, many progenitors and several neurons were found. To provide the progenitor cells with a neurotrophic factor, different isoforms of fibroblast growth factor-2 were introduced. To follow the behavior of the transfected cells in vitro, functional tests such as the cell viability assay (water-soluble tetrazolium salt assay [WST-1]) and the cell proliferation assay (5-bromo-2'-deoxyuridine-enzyme-linked immunosorbent assay) were performed. In addition, these transfected NPCs were viable after transplantation, expressed tyrosine hydroxylase in vivo, and could easily be detected within the host striatum because of their EGFP expression. This study shows that genetic modification of neural progenitors could provide attractive perspectives for new therapeutic concepts in neurodegenerative diseases.
Collapse
|
20
|
Tetzlaff JE, Huppenbauer CB, Tanzer L, Alexander TD, Jones KJ. Motoneuron injury and repair: New perspectives on gonadal steroids as neurotherapeutics. J Mol Neurosci 2006; 28:53-64. [PMID: 16632875 DOI: 10.1385/jmn:28:1:53] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2005] [Revised: 11/30/1999] [Accepted: 06/28/2005] [Indexed: 12/26/2022]
Abstract
In this review, we will summarize recent work from our laboratory on the role of gonadal steroids as neuroprotective agents in motoneuron viability following cell stress. Three motoneuron models will be discussed: developing axotomized hamster facial motoneurons (FMNs); adult axotomized mouse FMNs; and immortalized, cultured mouse spinal motoneurons subjected to heat shock. New work on two relevant motoneuron proteins, the survival of motor neuron protein, and neuritin or candidate plasticity-related gene 15, indicates differential steroid regulation of these two proteins after axotomy. The concept of gonadal steroids as cellular stress correction factors and the implications of this for acute neurological injury situations will be presented as well.
Collapse
Affiliation(s)
- Julie E Tetzlaff
- Department of Cell Biology, Neurobiology, and Anatomy, Loyola University of Chicago, Stritch School of Medicine, Maywood, IL 60153, USA
| | | | | | | | | |
Collapse
|
21
|
Sørensen V, Nilsen T, Wiedłocha A. Functional diversity of FGF-2 isoforms by intracellular sorting. Bioessays 2006; 28:504-14. [PMID: 16615083 DOI: 10.1002/bies.20405] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Regulation of the subcellular localization of certain proteins is a mechanism for the regulation of their biological activities. FGF-2 can be produced as distinct isoforms by alternative initiation of translation on a single mRNA and the isoforms are differently sorted in cells. High molecular weight FGF-2 isoforms are not secreted from the cell, but are transported to the nucleus where they regulate cell growth or behavior in an intracrine fashion. 18 kDa FGF-2 can be secreted to the extracellular medium where it acts as a conventional growth factor by binding to and activation of cell-surface receptors. Furthermore, following receptor-mediated endocytosis, the exogenous FGF-2 can be transported to the nuclei of target cells, and this is of importance for the transmittance of a mitogenic signal. The growth factor is able to interact with several intracellular proteins. Here, the mode of action and biological role of intracellular FGF-2 are discussed.
Collapse
Affiliation(s)
- Vigdis Sørensen
- Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, University of Oslo, Norway
| | | | | |
Collapse
|
22
|
Popovici C, Berda Y, Conchonaud F, Harbis A, Birnbaum D, Roubin R. Direct and heterologous approaches to identify the LET-756/FGF interactome. BMC Genomics 2006; 7:105. [PMID: 16672054 PMCID: PMC1513213 DOI: 10.1186/1471-2164-7-105] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2006] [Accepted: 05/03/2006] [Indexed: 11/16/2022] Open
Abstract
Background Fibroblast growth factors (FGFs) are multifunctional proteins that play important roles in cell communication, proliferation and differentiation. However, many aspects of their activities are not well defined. LET-756, one of the two C. elegans FGFs, is expressed throughout development and is essential for worm development. It is both expressed in the nucleus and secreted. Results To identify nuclear factors associated with LET-756, we used three approaches. First, we screened a two-hybrid cDNA library derived from mixed stages worms and from a normalized library, using LET-756 as bait. This direct approach allowed the identification of several binding partners that play various roles in the nucleus/nucleolus, such as PAL-1, a transcription regulator, or RPS-16, a component of the small ribosomal subunit. The interactions were validated by co-immunoprecipitation and determination of their site of occurrence in mammalian cells. Second, because patterns of protein interactions may be conserved throughout species, we searched for orthologs of known mammalian interactors and measured binary interaction with these predicted candidates. We found KIN-3 and KIN-10, the orthologs of CK2α and CK2β, as new partners of LET-756. Third, following the assumption that recognition motifs mediating protein interaction may be conserved between species, we screened a two-hybrid cDNA human library using LET-756 as bait. Among the few FGF partners detected was 14-3-3β. In support of this interaction we showed that the two 14-3-3β orthologous proteins, FTT-1 and FTT-2/PAR-5, interacted with LET-756. Conclusion We have conducted the first extensive search for LET-756 interactors using a multi-directional approach and established the first interaction map of LET-756/FGF with other FGF binding proteins from other species. The interactors identified play various roles in developmental process or basic biochemical events such as ribosome biogenesis.
Collapse
Affiliation(s)
- Cornel Popovici
- Institut de Cancérologie de Marseille, Laboratoire d'Oncologie Moléculaire, Institut Paoli-Calmettes et UMR599 INSERM, 27 Bd. Leï Roure, 13009 Marseille, France
| | - Yael Berda
- Institut de Cancérologie de Marseille, Laboratoire d'Oncologie Moléculaire, Institut Paoli-Calmettes et UMR599 INSERM, 27 Bd. Leï Roure, 13009 Marseille, France
| | - Fabien Conchonaud
- Institut de Cancérologie de Marseille, Laboratoire d'Oncologie Moléculaire, Institut Paoli-Calmettes et UMR599 INSERM, 27 Bd. Leï Roure, 13009 Marseille, France
| | - Aurélie Harbis
- Institut de Cancérologie de Marseille, Laboratoire d'Oncologie Moléculaire, Institut Paoli-Calmettes et UMR599 INSERM, 27 Bd. Leï Roure, 13009 Marseille, France
| | - Daniel Birnbaum
- Institut de Cancérologie de Marseille, Laboratoire d'Oncologie Moléculaire, Institut Paoli-Calmettes et UMR599 INSERM, 27 Bd. Leï Roure, 13009 Marseille, France
| | - Régine Roubin
- Institut de Cancérologie de Marseille, Laboratoire d'Oncologie Moléculaire, Institut Paoli-Calmettes et UMR599 INSERM, 27 Bd. Leï Roure, 13009 Marseille, France
| |
Collapse
|
23
|
Renvoisé B, Khoobarry K, Gendron MC, Cibert C, Viollet L, Lefebvre S. Distinct domains of the spinal muscular atrophy protein SMN are required for targeting to Cajal bodies in mammalian cells. J Cell Sci 2006; 119:680-92. [PMID: 16449324 DOI: 10.1242/jcs.02782] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Mutations of the survival motor neuron gene SMN1 cause the inherited disease spinal muscular atrophy (SMA). The ubiquitous SMN protein facilitates the biogenesis of spliceosomal small nuclear ribonucleoproteins (snRNPs). The protein is detected in the cytoplasm, nucleoplasm and enriched with snRNPs in nuclear Cajal bodies. It is structurally divided into at least an amino-terminal region rich in basic amino acid residues, a central Tudor domain, a self-association tyrosine-glycine-box and an exon7-encoded C-terminus. To examine the domains required for the intranuclear localization of SMN, we have used fluorescently tagged protein mutants transiently overexpressed in mammalian cells. The basic amino acid residues direct nucleolar localization of SMN mutants. The Tudor domain promotes localization of proteins in the nucleus and it cooperates with the basic amino acid residues and the tyrosine-glycine-box for protein localization in Cajal bodies. Moreover, the most frequent disease-linked mutant SMNΔex7 reduces accumulation of snRNPs in Cajal bodies, suggesting that the C-terminus of SMN participates in targeting to Cajal bodies. A reduced number of Cajal bodies in patient fibroblasts associates with the absence of snRNPs in Cajal bodies, revealing that intranuclear snRNA organization is modified in disease. These results indicate that direct and indirect mechanisms regulate localization of SMN in Cajal bodies.
Collapse
Affiliation(s)
- Benoît Renvoisé
- Laboratoire de Biologie Cellulaire des Membranes, Institut Jacques Monod (IJM), UMR 7592 CNRS/Universités Paris 6 et 7, 2 Place Jussieu, 75251 Paris Cedex 05, France
| | | | | | | | | | | |
Collapse
|