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van den Akker GGH, Zacchini F, Housmans BAC, van der Vloet L, Caron MMJ, Montanaro L, Welting TJM. Current Practice in Bicistronic IRES Reporter Use: A Systematic Review. Int J Mol Sci 2021; 22:5193. [PMID: 34068921 PMCID: PMC8156625 DOI: 10.3390/ijms22105193] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 05/05/2021] [Accepted: 05/12/2021] [Indexed: 12/26/2022] Open
Abstract
Bicistronic reporter assays have been instrumental for transgene expression, understanding of internal ribosomal entry site (IRES) translation, and identification of novel cap-independent translational elements (CITE). We observed a large methodological variability in the use of bicistronic reporter assays and data presentation or normalization procedures. Therefore, we systematically searched the literature for bicistronic IRES reporter studies and analyzed methodological details, data visualization, and normalization procedures. Two hundred fifty-seven publications were identified using our search strategy (published 1994-2020). Experimental studies on eukaryotic adherent cell systems and the cell-free translation assay were included for further analysis. We evaluated the following methodological details for 176 full text articles: the bicistronic reporter design, the cell line or type, transfection methods, and time point of analyses post-transfection. For the cell-free translation assay, we focused on methods of in vitro transcription, type of translation lysate, and incubation times and assay temperature. Data can be presented in multiple ways: raw data from individual cistrons, a ratio of the two, or fold changes thereof. In addition, many different control experiments have been suggested when studying IRES-mediated translation. In addition, many different normalization and control experiments have been suggested when studying IRES-mediated translation. Therefore, we also categorized and summarized their use. Our unbiased analyses provide a representative overview of bicistronic IRES reporter use. We identified parameters that were reported inconsistently or incompletely, which could hamper data reproduction and interpretation. On the basis of our analyses, we encourage adhering to a number of practices that should improve transparency of bicistronic reporter data presentation and improve methodological descriptions to facilitate data replication.
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Affiliation(s)
- Guus Gijsbertus Hubert van den Akker
- Department of Orthopedic Surgery, Maastricht University, Medical Center+, 6229 ER Maastricht, The Netherlands; (G.G.H.v.d.A.); (B.A.C.H.); (L.v.d.V.); (M.M.J.C.)
| | - Federico Zacchini
- Department of Experimental, Diagnostic and Specialty Medicine, Bologna University, I-40138 Bologna, Italy; (F.Z.); (L.M.)
- Centro di Ricerca Biomedica Applicata—CRBA, Bologna University, Policlinico di Sant’Orsola, I-40138 Bologna, Italy
| | - Bas Adrianus Catharina Housmans
- Department of Orthopedic Surgery, Maastricht University, Medical Center+, 6229 ER Maastricht, The Netherlands; (G.G.H.v.d.A.); (B.A.C.H.); (L.v.d.V.); (M.M.J.C.)
| | - Laura van der Vloet
- Department of Orthopedic Surgery, Maastricht University, Medical Center+, 6229 ER Maastricht, The Netherlands; (G.G.H.v.d.A.); (B.A.C.H.); (L.v.d.V.); (M.M.J.C.)
| | - Marjolein Maria Johanna Caron
- Department of Orthopedic Surgery, Maastricht University, Medical Center+, 6229 ER Maastricht, The Netherlands; (G.G.H.v.d.A.); (B.A.C.H.); (L.v.d.V.); (M.M.J.C.)
| | - Lorenzo Montanaro
- Department of Experimental, Diagnostic and Specialty Medicine, Bologna University, I-40138 Bologna, Italy; (F.Z.); (L.M.)
- Centro di Ricerca Biomedica Applicata—CRBA, Bologna University, Policlinico di Sant’Orsola, I-40138 Bologna, Italy
- Programma Dipartimentale in Medicina di Laboratorio, IRCCS Azienda Ospedaliero-Universitaria di Bologna, Via Albertoni 15, I-40138 Bologna, Italy
| | - Tim Johannes Maria Welting
- Department of Orthopedic Surgery, Maastricht University, Medical Center+, 6229 ER Maastricht, The Netherlands; (G.G.H.v.d.A.); (B.A.C.H.); (L.v.d.V.); (M.M.J.C.)
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Péladeau C, Jasmin BJ. Targeting IRES-dependent translation as a novel approach for treating Duchenne muscular dystrophy. RNA Biol 2020; 18:1238-1251. [PMID: 33164678 DOI: 10.1080/15476286.2020.1847894] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Internal-ribosomal entry sites (IRES) are translational elements that allow the initiation machinery to start protein synthesis via internal initiation. IRESs promote tissue-specific translation in stress conditions when conventional cap-dependent translation is inhibited. Since many IRES-containing mRNAs are relevant to diseases, this cellular mechanism is emerging as an attractive therapeutic target for pharmacological and genetic modulations. Indeed, there has been growing interest over the past years in determining the therapeutic potential of IRESs for several disease conditions such as cancer, neurodegeneration and neuromuscular diseases including Duchenne muscular dystrophy (DMD). IRESs relevant for DMD have been identified in several transcripts whose protein product results in functional improvements in dystrophic muscles. Together, these converging lines of evidence indicate that activation of IRES-mediated translation of relevant transcripts in DMD muscle represents a novel and appropriate therapeutic strategy for DMD that warrants further investigation, particularly to identify agents that can modulate their activity.
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Affiliation(s)
- Christine Péladeau
- Department of Cellular and Molecular Medicine, and the Eric Poulin Centre for Neuromuscular Disease, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada
| | - Bernard J Jasmin
- Department of Cellular and Molecular Medicine, and the Eric Poulin Centre for Neuromuscular Disease, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada
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Pacheco A, Merianda TT, Twiss JL, Gallo G. Mechanism and role of the intra-axonal Calreticulin translation in response to axonal injury. Exp Neurol 2019; 323:113072. [PMID: 31669485 DOI: 10.1016/j.expneurol.2019.113072] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Revised: 09/17/2019] [Accepted: 09/27/2019] [Indexed: 12/12/2022]
Abstract
Following injury, sensory axons locally translate mRNAs that encode proteins needed for the response to injury, locally and through retrograde signaling, and for regeneration. In this study, we addressed the mechanism and role of axotomy-induced intra-axonal translation of the ER chaperone Calreticulin. In vivo peripheral nerve injury increased Calreticulin levels in sensory axons. Using an in vitro model system of sensory neurons amenable to mechanistic dissection we provide evidence that axotomy induces local translation of Calreticulin through PERK (protein kinase RNA-like endoplasmic reticulum kinase) mediated phosphorylation of eIF2α by a mechanism that requires both 5' and 3'UTRs (untranslated regions) elements in Calreticulin mRNA. ShRNA mediated depletion of Calreticulin or inhibition of PERK signaling increased axon retraction following axotomy. In contrast, expression of axonally targeted, but not somatically restricted, Calreticulin mRNA decreased retraction and promoted axon regeneration following axotomy in vitro. Collectively, these data indicate that the intra-axonal translation of Calreticulin in response to axotomy serves to minimize the ensuing retraction, and overexpression of axonally targeted Calreticulin mRNA promotes axon regeneration.
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Affiliation(s)
- Almudena Pacheco
- Temple University School of Medicine, Shriners Pediatric Research Center, Department of Anatomy and Cell Biology, 3500 North Broad St, Philadelphia, PA 19140, United States of America.
| | - Tanuja T Merianda
- Drexel University, Department of Biology, Philadelphia, PA 19104, United States of America
| | - Jeffery L Twiss
- University of South Carolina, Department of Biological Sciences, Columbia 29208, SC, United States of America.
| | - Gianluca Gallo
- Temple University School of Medicine, Shriners Pediatric Research Center, Department of Anatomy and Cell Biology, 3500 North Broad St, Philadelphia, PA 19140, United States of America.
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4
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Ghosh DK, Ranjan A. An IRES-dependent translation of HYPK mRNA generates a truncated isoform of the protein that lacks the nuclear localization and functional ability. RNA Biol 2019; 16:1604-1621. [PMID: 31397627 DOI: 10.1080/15476286.2019.1650612] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
Different mechanisms of translation initiation process exist to start the protein synthesis from various viral and eukaryotic mRNA. The cap-independent and tertiary structure directed translation initiation of mRNAs forms the basis of internal ribosome entry site (IRES) mediated translation initiation that helps in cellular protein production in different conditions. HYPK protein sequesters different aggregation-prone proteins to help in the cellular proteostasis. HYPK mRNA is differentially translated from an internal start/initiation codon to generate an amino terminal-truncated isoform (HSPC136) of HYPK protein. In this study, we report that an IRES-dependent translation initiation of HYPK mRNA results in the formation of the HSPC136/HYPK-ΔN isoform of HYPK protein. The IRES-driven translation product, HYPK-ΔN, lacks the N-terminal tri-arginine motif that acts as the nuclear localization signal (NLS) in the full-length HYPK protein. While the full-length HYPK protein translocates to the nucleus and prevents the aggregation of the mutant p53 (p53-R248Q) protein, the HYPK-ΔN lacks this activity. The NLS of HYPK is not evolutionarily conserved and its exclusive presence in the HYPK of higher eukaryotic animals imparts additional advantage to the HYPK protein in tackling the cytosolic as well as nuclear protein aggregates. The presence of the NLS in full-length HYPK also allows this protein to modulate the cell cycle. These results provide a mechanistic detail of HYPK mRNA's translation initiation control by an IRES that dictates the formation of HYPC136/HYPK-ΔN which lacks the nuclear localization and functional ability.
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Affiliation(s)
- Debasish Kumar Ghosh
- Computational and Functional Genomics Group, Centre for DNA Fingerprinting and Diagnostics , Hyderabad , Telangana , India.,Graduate studies, Manipal Academy of Higher Education , Manipal , Karnataka , India
| | - Akash Ranjan
- Computational and Functional Genomics Group, Centre for DNA Fingerprinting and Diagnostics , Hyderabad , Telangana , India
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Koley S, Rozenbaum M, Fainzilber M, Terenzio M. Translating regeneration: Local protein synthesis in the neuronal injury response. Neurosci Res 2019; 139:26-36. [DOI: 10.1016/j.neures.2018.10.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Revised: 09/13/2018] [Accepted: 10/02/2018] [Indexed: 12/21/2022]
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Seo JY, Jung Y, Kim DY, Ryu HG, Lee J, Kim SW, Kim KT. DAP5 increases axonal outgrowth of hippocampal neurons by enhancing the cap-independent translation of DSCR1.4 mRNA. Cell Death Dis 2019; 10:49. [PMID: 30718468 PMCID: PMC6362140 DOI: 10.1038/s41419-018-1299-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Revised: 11/30/2018] [Accepted: 12/19/2018] [Indexed: 12/18/2022]
Abstract
Proper wiring between neurons is indispensable for proper brain function. From the early developmental stage, axons grow and navigate to connect to targets according to specific guidance cues. The accuracy of axonal outgrowth and navigation are controlled by a variety of genes, and mutations and/or deficiencies in these genes are closely related to several brain disorders, such as autism. DSCR1 is one of these genes and regulates actin filament formation in axons. Thus, identifying the detailed regulatory mechanisms of DSCR1 expression is crucial for the understanding of the axon development of neurons; however, these regulatory mechanisms of DSCR1 remain unknown. Here, we discovered that mRNA encoding the DSCR1 isoform DSCR1.4 is present and mainly translated by the cap-independent initiation mechanisms in both the soma and axons of hippocampal neurons. We found that translation of DSCR1.4 mRNA is enhanced by death-associated protein 5 (DAP5), which can bind to DSCR1.4 5'UTR. BDNF-stimulus induced an increase in DAP5 expression and the cap-independent translation efficiency of DSCR1.4 mRNA in axon as well as soma. Furthermore, we showed the importance of the cap-independent translation of DSCR1.4 on enhancement of DSCR1.4 expression by BDNF-stimulus and axonal outgrowth of hippocampal neurons. Our findings suggest a new translational regulatory mechanism for DSCR1.4 expressions and a novel function of DAP5 as a positive regulator of DSCR1.4 mRNA translation induced in soma and axon of hippocampal neurons.
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Affiliation(s)
- Ji-Young Seo
- Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, Republic of Korea
| | - Youngseob Jung
- Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, Republic of Korea
| | - Do-Yeon Kim
- Department of Pharmacology, School of Dentistry, Kyungpook National University (KNU), Daegu, Republic of Korea
| | - Hye Guk Ryu
- Department of Life Sciences, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, Republic of Korea
| | - Juhyun Lee
- Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, Republic of Korea
| | - Sung Wook Kim
- Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, Republic of Korea
| | - Kyong-Tai Kim
- Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, Republic of Korea. .,Department of Life Sciences, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, Republic of Korea.
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7
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Sahoo PK, Smith DS, Perrone-Bizzozero N, Twiss JL. Axonal mRNA transport and translation at a glance. J Cell Sci 2018; 131:jcs196808. [PMID: 29654160 PMCID: PMC6518334 DOI: 10.1242/jcs.196808] [Citation(s) in RCA: 82] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Localization and translation of mRNAs within different subcellular domains provides an important mechanism to spatially and temporally introduce new proteins in polarized cells. Neurons make use of this localized protein synthesis during initial growth, regeneration and functional maintenance of their axons. Although the first evidence for protein synthesis in axons dates back to 1960s, improved methodologies, including the ability to isolate axons to purity, highly sensitive RNA detection methods and imaging approaches, have shed new light on the complexity of the transcriptome of the axon and how it is regulated. Moreover, these efforts are now uncovering new roles for locally synthesized proteins in neurological diseases and injury responses. In this Cell Science at a Glance article and the accompanying poster, we provide an overview of how axonal mRNA transport and translation are regulated, and discuss their emerging links to neurological disorders and neural repair.
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Affiliation(s)
- Pabitra K Sahoo
- Department of Biological Sciences, University of South Carolina, 715 Sumter St., CLS 401, Columbia, SC 29208, USA
| | - Deanna S Smith
- Department of Biological Sciences, University of South Carolina, 715 Sumter St., CLS 401, Columbia, SC 29208, USA
| | - Nora Perrone-Bizzozero
- Department of Neurosciences, University of New Mexico School of Medicine, 1 University of New Mexico, MSC08 4740, Albuquerque, NM 87131, USA
| | - Jeffery L Twiss
- Department of Biological Sciences, University of South Carolina, 715 Sumter St., CLS 401, Columbia, SC 29208, USA
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8
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Vaklavas C, Grizzle WE, Choi H, Meng Z, Zinn KR, Shrestha K, Blume SW. IRES inhibition induces terminal differentiation and synchronized death in triple-negative breast cancer and glioblastoma cells. Tumour Biol 2016; 37:13247-13264. [PMID: 27460074 PMCID: PMC5097113 DOI: 10.1007/s13277-016-5161-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Accepted: 07/12/2016] [Indexed: 01/07/2023] Open
Abstract
Internal ribosome entry site (IRES)-mediated translation is a specialized mode of protein synthesis which malignant cells depend on to survive adverse microenvironmental conditions. Our lab recently reported the identification of a group of compounds which selectively interfere with IRES-mediated translation, completely blocking de novo IGF1R synthesis, and differentially modulating synthesis of the two c-Myc isoforms. Here, we examine the phenotypic consequences of sustained IRES inhibition in human triple-negative breast carcinoma and glioblastoma cells. A sudden loss of viability affects the entire tumor cell population after ∼72-h continuous exposure to the lead compound. The extraordinarily steep dose-response relationship (Hill-Slope coefficients −15 to −35) and extensive physical connections established between the cells indicate that the cells respond to IRES inhibition collectively as a population rather than as individual cells. Prior to death, the treated cells exhibit prominent features of terminal differentiation, with marked gains in cytoskeletal organization, planar polarity, and formation of tight junctions or neuronal processes. In addition to IGF1R and Myc, specific changes in connexin 43, BiP, CHOP, p21, and p27 also correlate with phenotypic outcome. This unusual mode of tumor cell death is absolutely dependent on exceeding a critical threshold in cell density, suggesting that a quorum-sensing mechanism may be operative. Death of putative tumor stem cells visualized in situ helps to explain the inability of tumor cells to recover and repopulate once the compound is removed. Together, these findings support the concept that IRES-mediated translation is of fundamental importance to maintenance of the undifferentiated phenotype and survival of undifferentiated malignant cells.
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Affiliation(s)
- Christos Vaklavas
- Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, AL, 35294, USA.,Department of Medicine, Division of Hematology/Oncology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - William E Grizzle
- Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, AL, 35294, USA.,Department of Pathology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Hyoungsoo Choi
- Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, AL, 35294, USA.,Department of Medicine, Division of Hematology/Oncology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA.,Department of Pediatrics, Seoul National University Bundang Hospital, Gyeonggi-do, 463-707, South Korea
| | - Zheng Meng
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Bevill Biomedical Research Bldg Room 765, 845 19th Street S, Birmingham, AL, 35294, USA.,Analytical Development Division, Novavax Inc., Rockville, MD, 20850, USA
| | - Kurt R Zinn
- Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, AL, 35294, USA.,Department of Pathology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA.,Department of Radiology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Kedar Shrestha
- Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, AL, 35294, USA.,Department of Medicine, Division of Hematology/Oncology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Scott W Blume
- Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, AL, 35294, USA. .,Department of Medicine, Division of Hematology/Oncology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA. .,Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Bevill Biomedical Research Bldg Room 765, 845 19th Street S, Birmingham, AL, 35294, USA.
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mRNAs and Protein Synthetic Machinery Localize into Regenerating Spinal Cord Axons When They Are Provided a Substrate That Supports Growth. J Neurosci 2015; 35:10357-70. [PMID: 26180210 DOI: 10.1523/jneurosci.1249-15.2015] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
UNLABELLED Although intra-axonal protein synthesis is well recognized in cultured neurons and during development in vivo, there have been few reports of mRNA localization and/or intra-axonal translation in mature CNS axons. Indeed, previous work indicated that mature CNS axons contain much lower quantities of translational machinery than PNS axons, leading to the conclusion that the capacity for intra-axonal protein synthesis is linked to the intrinsic capacity of a neuron for regeneration, with mature CNS neurons showing much less growth after injury than PNS neurons. However, when regeneration by CNS axons is facilitated, it is not known whether the intra-axonal content of translational machinery changes or whether mRNAs localize into these axons. Here, we have used a peripheral nerve segment grafted into the transected spinal cord of adult rats as a supportive environment for regeneration by ascending spinal axons. By quantitative fluorescent in situ hybridization combined with immunofluorescence to unambiguously distinguish intra-axonal mRNAs, we show that regenerating spinal cord axons contain β-actin, GAP-43, Neuritin, Reg3a, Hamp, and Importin β1 mRNAs. These axons also contain 5S rRNA, phosphorylated S6 ribosomal protein, eIF2α translation factor, and 4EBP1 translation factor inhibitory protein. Different levels of these mRNAs in CNS axons from regenerating PNS axons may relate to differences in the growth capacity of these neurons, although the presence of mRNA transport and likely local translation in both CNS and PNS neurons suggests an active role in the regenerative process. SIGNIFICANCE STATEMENT Although peripheral nerve axons retain the capacity to locally synthesize proteins into adulthood, previous studies have argued that mature brain and spinal cord axons cannot synthesize proteins. Protein synthesis in peripheral nerve axons is increased during regeneration, and intra-axonally synthesized proteins have been shown to contribute to nerve regeneration. Here, we show that mRNAs and translational machinery are transported into axons regenerating from the spinal cord into the permissive environment of a peripheral nerve graft. Our data raise the possibility that spinal cord axons may make use of localized protein synthesis for regeneration.
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Yoo S, Kim HH, Kim P, Donnelly CJ, Kalinski AL, Vuppalanchi D, Park M, Lee SJ, Merianda TT, Perrone-Bizzozero NI, Twiss JL. A HuD-ZBP1 ribonucleoprotein complex localizes GAP-43 mRNA into axons through its 3' untranslated region AU-rich regulatory element. J Neurochem 2013; 126:792-804. [PMID: 23586486 DOI: 10.1111/jnc.12266] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2012] [Revised: 04/01/2013] [Accepted: 04/01/2013] [Indexed: 11/29/2022]
Abstract
Localized translation of axonal mRNAs contributes to developmental and regenerative axon growth. Although untranslated regions (UTRs) of many different axonal mRNAs appear to drive their localization, there has been no consensus RNA structure responsible for this localization. We recently showed that limited expression of ZBP1 protein restricts axonal localization of both β-actin and GAP-43 mRNAs. β-actin 3'UTR has a defined element for interaction with ZBP1, but GAP-43 mRNA shows no homology to this RNA sequence. Here, we show that an AU-rich regulatory element (ARE) in GAP-43's 3'UTR is necessary and sufficient for its axonal localization. Axonal GAP-43 mRNA levels increase after in vivo injury, and GAP-43 mRNA shows an increased half-life in regenerating axons. GAP-43 mRNA interacts with both HuD and ZBP1, and HuD and ZBP1 co-immunoprecipitate in an RNA-dependent fashion. Reporter mRNA with the GAP-43 ARE competes with endogenous β-actin mRNA for axonal localization and decreases axon length and branching similar to the β-actin 3'UTR competing with endogenous GAP-43 mRNA. Conversely, over-expressing GAP-43 coding sequence with its 3'UTR ARE increases axonal elongation and this effect is lost when just the ARE is deleted from GAP-43's 3'UTR. We have recently found that over-expression of GAP-43 using an axonally targeted construct with the 3'UTRs of GAP-43 promoted elongating growth of axons, while restricting the mRNA to the cell body with the 3'UTR of γ-actin had minimal effect on axon length. In this study, we show that the ARE in GAP-43's 3'UTR is responsible for localization of GAP-43 mRNA into axons and is sufficient for GAP-43 protein's role in elongating axonal growth.
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Affiliation(s)
- Soonmoon Yoo
- Nemours Biomedical Research, Alfred I. duPont Hosp. for Children, Wilmington, Delaware, USA.
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Kroeger H, Messah C, Ahern K, Gee J, Joseph V, Matthes MT, Yasumura D, Gorbatyuk MS, Chiang WC, LaVail MM, Lin JH. Induction of endoplasmic reticulum stress genes, BiP and chop, in genetic and environmental models of retinal degeneration. Invest Ophthalmol Vis Sci 2012; 53:7590-9. [PMID: 23074209 DOI: 10.1167/iovs.12-10221] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
PURPOSE Endoplasmic reticulum (ER) stress has been observed in animal models of retinitis pigmentosa expressing P23H rhodopsin. We compared levels of tightly induced ER stress genes, Binding of immunoglobulin protein (BiP) and CCAAT/enhancer-binding protein homologous protein (Chop), in seven additional models of retinal degeneration arising from genetic or environmental causes. METHODS Retinas from transgenic S334ter rhodopsin (lines 3, 4, and 5) and Royal College of Surgeons (RCS and RCS-p+) rats from postnatal (P) days 10 to 120 were analyzed. In a constant light (CL) model of retinal degeneration, BALB/c mice were exposed to 15,000 lux of CL for 0 to 8 hours. Retinal tissues from three to eight animals per experimental condition were collected for histologic and molecular analyses. RESULTS S334ter animals revealed significant increases in BiP, S334ter-3 (3.3× at P15), S334ter-4 (4× at P60), and S334ter-5 (2.2× at P90), and Chop, S334ter-3 (1.3× at P15), S334ter-4 (1.5× at P30), and S334ter-5 (no change), compared with controls. P23H-3 rats showed significant increase of BiP at P60 (2.3×) and Chop (1.6×). RCS and RCS-p+ rats showed significant increases in BiP at P60 (2.4×) and P20 (1.8×), respectively, but no statistically significant changes in Chop. BALB/c mice showed increases in BiP (1.5×) and Chop (1.3×) after 4 hours of CL. Increased levels of these ER stress markers correlated with photoreceptor cell loss. CONCLUSIONS Our study reveals surprising increases in BiP and to a lesser degree Chop in retinal degenerations arising from diverse causes. We propose that manipulation of ER stress responses may be helpful in treating many environmental and heritable forms of retinal degeneration.
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Affiliation(s)
- Heike Kroeger
- Department of Pathology, University of California, San Diego, La Jolla, California, USA
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