1
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Rhodes SD, McCormick F, Cagan RL, Bakker A, Staedtke V, Ly I, Steensma MR, Lee SY, Romo CG, Blakeley JO, Sarin KY. RAS Signaling Gone Awry in the Skin: The Complex Role of RAS in Cutaneous Neurofibroma Pathogenesis, Emerging Biological Insights. J Invest Dermatol 2023; 143:1358-1368. [PMID: 37245145 PMCID: PMC10409534 DOI: 10.1016/j.jid.2023.01.043] [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: 09/20/2022] [Revised: 01/13/2023] [Accepted: 01/20/2023] [Indexed: 05/29/2023]
Abstract
Cutaneous neurofibromas (cNFs) are the most common tumor in people with the rasopathy neurofibromatosis type 1. They number in hundreds or even thousands throughout the body, and currently, there are no effective interventions to prevent or treat these skin tumors. To facilitate the identification of novel and effective therapies, essential studies including a more refined understanding of cNF biology and the role of RAS signaling and downstream effector pathways responsible for cNF initiation, growth, and maintenance are needed. This review highlights the current state of knowledge of RAS signaling in cNF pathogenesis and therapeutic development for cNF treatment.
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Affiliation(s)
- Steven D Rhodes
- Division of Hematology-Oncology, Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana, USA; Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, Indiana, USA; Herman B Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, Indiana, USA; Melvin and Bren Simon Comprehensive Cancer Center, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Frank McCormick
- Helen Diller Family Comprehensive Cancer Center, University of California San Francisco, San Francisco, California, USA; Frederick National Laboratory for Cancer Research, Frederick, Maryland, USA
| | - Ross L Cagan
- School of Cancer Sciences, University of Glasgow, Glasgow, Scotland
| | | | - Verena Staedtke
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Ina Ly
- Stephen E. and Catherine Pappas Center for Neuro-Oncology, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Matthew R Steensma
- Center for Cancer and Cell Biology, Van Andel Research Institute, Grand Rapids, Michigan, USA; Helen DeVos Children's Hospital, Spectrum Health System, Grand Rapids, Michigan, USA; College of Human Medicine, Michigan State University, Grand Rapids, Michigan, USA
| | - Sang Y Lee
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Carlos G Romo
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Jaishri O Blakeley
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Kavita Y Sarin
- Department of Dermatology, Stanford University School of Medicine, Stanford, California, USA.
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2
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Montag K, Ivanov R, Bauer P. Role of SEC14-like phosphatidylinositol transfer proteins in membrane identity and dynamics. FRONTIERS IN PLANT SCIENCE 2023; 14:1181031. [PMID: 37255567 PMCID: PMC10225987 DOI: 10.3389/fpls.2023.1181031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Accepted: 04/05/2023] [Indexed: 06/01/2023]
Abstract
Membrane identity and dynamic processes, that act at membrane sites, provide important cues for regulating transport, signal transduction and communication across membranes. There are still numerous open questions as to how membrane identity changes and the dynamic processes acting at the surface of membranes are regulated in diverse eukaryotes in particular plants and which roles are being played by protein interaction complexes composed of peripheral and integral membrane proteins. One class of peripheral membrane proteins conserved across eukaryotes comprises the SEC14-like phosphatidylinositol transfer proteins (SEC14L-PITPs). These proteins share a SEC14 domain that contributes to membrane identity and fulfills regulatory functions in membrane trafficking by its ability to sense, bind, transport and exchange lipophilic substances between membranes, such as phosphoinositides and diverse other lipophilic substances. SEC14L-PITPs can occur as single-domain SEC14-only proteins in all investigated organisms or with a modular domain structure as multi-domain proteins in animals and streptophytes (comprising charales and land plants). Here, we present an overview on the functional roles of SEC14L-PITPs, with a special focus on the multi-domain SEC14L-PITPs of the SEC14-nodulin and SEC14-GOLD group (PATELLINs, PATLs in plants). This indicates that SEC14L-PITPs play diverse roles from membrane trafficking to organism fitness in plants. We concentrate on the structure of SEC14L-PITPs, their ability to not only bind phospholipids but also other lipophilic ligands, and their ability to regulate complex cellular responses through interacting with proteins at membrane sites.
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Affiliation(s)
- Karolin Montag
- Institute of Botany, Heinrich Heine University, Düsseldorf, Germany
| | - Rumen Ivanov
- Institute of Botany, Heinrich Heine University, Düsseldorf, Germany
| | - Petra Bauer
- Institute of Botany, Heinrich Heine University, Düsseldorf, Germany
- Center of Excellence on Plant Sciences (CEPLAS), Germany
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3
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Fernández-García P, Malet-Engra G, Torres M, Hanson D, Rosselló CA, Román R, Lladó V, Escribá PV. Evolving Diagnostic and Treatment Strategies for Pediatric CNS Tumors: The Impact of Lipid Metabolism. Biomedicines 2023; 11:biomedicines11051365. [PMID: 37239036 DOI: 10.3390/biomedicines11051365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2023] [Revised: 04/21/2023] [Accepted: 04/27/2023] [Indexed: 05/28/2023] Open
Abstract
Pediatric neurological tumors are a heterogeneous group of cancers, many of which carry a poor prognosis and lack a "standard of care" therapy. While they have similar anatomic locations, pediatric neurological tumors harbor specific molecular signatures that distinguish them from adult brain and other neurological cancers. Recent advances through the application of genetics and imaging tools have reshaped the molecular classification and treatment of pediatric neurological tumors, specifically considering the molecular alterations involved. A multidisciplinary effort is ongoing to develop new therapeutic strategies for these tumors, employing innovative and established approaches. Strikingly, there is increasing evidence that lipid metabolism is altered during the development of these types of tumors. Thus, in addition to targeted therapies focusing on classical oncogenes, new treatments are being developed based on a broad spectrum of strategies, ranging from vaccines to viral vectors, and melitherapy. This work reviews the current therapeutic landscape for pediatric brain tumors, considering new emerging treatments and ongoing clinical trials. In addition, the role of lipid metabolism in these neoplasms and its relevance for the development of novel therapies are discussed.
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Affiliation(s)
- Paula Fernández-García
- Laboratory of Molecular Cell Biomedicine, University of the Balearic Islands, 07122 Palma de Mallorca, Spain
- Laminar Pharmaceuticals, Isaac Newton, 07121 Palma de Mallorca, Spain
| | - Gema Malet-Engra
- Laboratory of Molecular Cell Biomedicine, University of the Balearic Islands, 07122 Palma de Mallorca, Spain
- Laminar Pharmaceuticals, Isaac Newton, 07121 Palma de Mallorca, Spain
| | - Manuel Torres
- Laboratory of Molecular Cell Biomedicine, University of the Balearic Islands, 07122 Palma de Mallorca, Spain
| | - Derek Hanson
- Hackensack Meridian Health, 343 Thornall Street, Edison, NJ 08837, USA
| | - Catalina A Rosselló
- Laboratory of Molecular Cell Biomedicine, University of the Balearic Islands, 07122 Palma de Mallorca, Spain
- Laminar Pharmaceuticals, Isaac Newton, 07121 Palma de Mallorca, Spain
| | - Ramón Román
- Laboratory of Molecular Cell Biomedicine, University of the Balearic Islands, 07122 Palma de Mallorca, Spain
- Laminar Pharmaceuticals, Isaac Newton, 07121 Palma de Mallorca, Spain
| | - Victoria Lladó
- Laboratory of Molecular Cell Biomedicine, University of the Balearic Islands, 07122 Palma de Mallorca, Spain
- Laminar Pharmaceuticals, Isaac Newton, 07121 Palma de Mallorca, Spain
| | - Pablo V Escribá
- Laboratory of Molecular Cell Biomedicine, University of the Balearic Islands, 07122 Palma de Mallorca, Spain
- Laminar Pharmaceuticals, Isaac Newton, 07121 Palma de Mallorca, Spain
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4
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Báez-Flores J, Rodríguez-Martín M, Lacal J. The therapeutic potential of neurofibromin signaling pathways and binding partners. Commun Biol 2023; 6:436. [PMID: 37081086 PMCID: PMC10119308 DOI: 10.1038/s42003-023-04815-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Accepted: 04/05/2023] [Indexed: 04/22/2023] Open
Abstract
Neurofibromin controls many cell processes, such as growth, learning, and memory. If neurofibromin is not working properly, it can lead to health problems, including issues with the nervous, skeletal, and cardiovascular systems and cancer. This review examines neurofibromin's binding partners, signaling pathways and potential therapeutic targets. In addition, it summarizes the different post-translational modifications that can affect neurofibromin's interactions with other molecules. It is essential to investigate the molecular mechanisms that underlie neurofibromin variants in order to provide with functional connections between neurofibromin and its associated proteins for possible therapeutic targets based on its biological function.
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Affiliation(s)
- Juan Báez-Flores
- Laboratory of Functional Genetics of Rare Diseases, Department of Microbiology and Genetics, University of Salamanca (USAL), 37007, Salamanca, Spain
- Institute of Biomedical Research of Salamanca (IBSAL), 37007, Salamanca, Spain
| | - Mario Rodríguez-Martín
- Laboratory of Functional Genetics of Rare Diseases, Department of Microbiology and Genetics, University of Salamanca (USAL), 37007, Salamanca, Spain
- Institute of Biomedical Research of Salamanca (IBSAL), 37007, Salamanca, Spain
| | - Jesus Lacal
- Laboratory of Functional Genetics of Rare Diseases, Department of Microbiology and Genetics, University of Salamanca (USAL), 37007, Salamanca, Spain.
- Institute of Biomedical Research of Salamanca (IBSAL), 37007, Salamanca, Spain.
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5
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Functional Assays Combined with Pre-mRNA-Splicing Analysis Improve Variant Classification and Diagnostics for Individuals with Neurofibromatosis Type 1 and Legius Syndrome. Hum Mutat 2023. [DOI: 10.1155/2023/9628049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
Neurofibromatosis type 1 (NF1) and Legius syndrome (LS) are caused by inactivating variants in NF1 and SPRED1. NF1 encodes neurofibromin (NF), a GTPase-activating protein (GAP) for RAS that interacts with the SPRED1 product, Sprouty-related protein with an EVH (Ena/Vasp homology) domain 1 (SPRED1). Obtaining a clinical and molecular diagnosis of NF1 or LS can be challenging due to the phenotypic diversity, the size and complexity of the NF1 and SPRED1 loci, and uncertainty over the effects of some NF1 and SPRED1 variants on pre-mRNA splicing and/or protein expression and function. To improve NF1 and SPRED1 variant classification and establish pathogenicity for NF1 and SPRED1 variants identified in individuals with NF1 or LS, we analyzed patient RNA by RT-PCR and performed in vitro exon trap experiments and estimated NF and SPRED1 protein expression, RAS GAP activity, and interaction. We obtained evidence to support pathogenicity according to American College of Medical Genetics guidelines for 73/114 variants tested, demonstrating the utility of functional approaches for NF1 and SPRED1 variant classification and NF and LS diagnostics.
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6
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Modica R, Altieri B, D’Aniello F, Benevento E, Cannavale G, Minotta R, Liccardi A, Colao A, Faggiano A. Vitamin D and Bone Metabolism in Adult Patients with Neurofibromatosis Type 1. Metabolites 2023; 13:metabo13020255. [PMID: 36837874 PMCID: PMC9966600 DOI: 10.3390/metabo13020255] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2022] [Revised: 01/27/2023] [Accepted: 02/02/2023] [Indexed: 02/12/2023] Open
Abstract
Neurofibromatosis type 1 (NF1) is a genetic multisystemic autosomal dominant disorder determining reduced life expectancy due to higher risk of developing benign and malignant tumors. Low levels of vitamin D and reduced bone mineral density (BMD) have been reported in young patients with NF1. However, correlation between vitamin D and NF1 phenotype needs to be elucidated. Aim of this study was to assess vitamin D levels and bone metabolism in NF1 patients, analyzing potential correlations with clinical phenotype. A cross-sectional study was carried out in a monocentric series of NF1 patients, evaluating genotype, clinical phenotype, BMD, biochemical evaluation with focus on serum 25OH-vitamin D, parathyroid hormone (PTH), calcium and phosphate levels. Correlations between clinical manifestations, neurofibromas, and vitamin D status have been studied in comparison with healthy controls. 31 NF1 adult patients were matched for sex, age and body mass index with 31 healthy controls. A significantly difference in vitamin D level emerged in NF1 patients compared to controls. Interestingly low vitamin D levels correlated with a more aggressive phenotype and with a bigger size of neurofibromas. These data underline that vitamin D deficiency/insufficiency may play a role in clinical severity of neurofibromas in patients with NF1, suggesting the need to check bone status and replace vitamin D in these patients.
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Affiliation(s)
- Roberta Modica
- Endocrinology, Diabetology and Andrology Unit, Department of Clinical Medicine and Surgery, Federico II University of Naples, 80131 Naples, Italy
- Correspondence:
| | - Barbara Altieri
- Division of Endocrinology and Diabetes, Department of Internal Medicine, University Hospital of Würzburg, 97080 Würzburg, Germany
| | - Francesco D’Aniello
- Pediatric University Department, Bambino Gesù Children’s Hospital, University of Rome “Tor Vergata”, 00165 Rome, Italy
| | - Elio Benevento
- Endocrinology, Diabetology and Andrology Unit, Department of Clinical Medicine and Surgery, Federico II University of Naples, 80131 Naples, Italy
| | - Giuseppe Cannavale
- Endocrinology, Diabetology and Andrology Unit, Department of Clinical Medicine and Surgery, Federico II University of Naples, 80131 Naples, Italy
| | - Roberto Minotta
- Endocrinology, Diabetology and Andrology Unit, Department of Clinical Medicine and Surgery, Federico II University of Naples, 80131 Naples, Italy
| | - Alessia Liccardi
- Endocrinology, Diabetology and Andrology Unit, Department of Clinical Medicine and Surgery, Federico II University of Naples, 80131 Naples, Italy
| | - Annamaria Colao
- Endocrinology, Diabetology and Andrology Unit, Department of Clinical Medicine and Surgery, Federico II University of Naples, 80131 Naples, Italy
- UNESCO Chair, Education for Health and Sustainable Development, Federico II University, 80131 Naples, Italy
| | - Antongiulio Faggiano
- Endocrinology Unit, Department of Clinical and Molecular Medicine, Sant’Andrea Hospital, ENETS Center of Excellence, Sapienza University of Rome, 00189 Rome, Italy
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7
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Miller AH, Halloran MC. Mechanistic insights from animal models of neurofibromatosis type 1 cognitive impairment. Dis Model Mech 2022; 15:276464. [PMID: 36037004 PMCID: PMC9459395 DOI: 10.1242/dmm.049422] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Neurofibromatosis type 1 (NF1) is an autosomal-dominant neurogenetic disorder caused by mutations in the gene neurofibromin 1 (NF1). NF1 predisposes individuals to a variety of symptoms, including peripheral nerve tumors, brain tumors and cognitive dysfunction. Cognitive deficits can negatively impact patient quality of life, especially the social and academic development of children. The neurofibromin protein influences neural circuits via diverse cellular signaling pathways, including through RAS, cAMP and dopamine signaling. Although animal models have been useful in identifying cellular and molecular mechanisms that regulate NF1-dependent behaviors, translating these discoveries into effective treatments has proven difficult. Clinical trials measuring cognitive outcomes in patients with NF1 have mainly targeted RAS signaling but, unfortunately, resulted in limited success. In this Review, we provide an overview of the structure and function of neurofibromin, and evaluate several cellular and molecular mechanisms underlying neurofibromin-dependent cognitive function, which have recently been delineated in animal models. A better understanding of neurofibromin roles in the development and function of the nervous system will be crucial for identifying new therapeutic targets for the various cognitive domains affected by NF1. Summary: Neurofibromin influences neural circuits through RAS, cAMP and dopamine signaling. Exploring the mechanisms underlying neurofibromin-dependent behaviors in animal models might enable future treatment of the various cognitive deficits that are associated with neurofibromatosis type 1.
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Affiliation(s)
- Andrew H Miller
- Department of Integrative Biology, University of Wisconsin-Madison, Madison, WI 53706, USA.,Department of Neuroscience, University of Wisconsin-Madison, Madison, WI 53705, USA.,Neuroscience Training Program, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Mary C Halloran
- Department of Integrative Biology, University of Wisconsin-Madison, Madison, WI 53706, USA.,Department of Neuroscience, University of Wisconsin-Madison, Madison, WI 53705, USA
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8
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Molecular Dynamics Simulations Reveal Structural Interconnections within Sec14-PH Bipartite Domain from Human Neurofibromin. Int J Mol Sci 2022; 23:ijms23105707. [PMID: 35628517 PMCID: PMC9147397 DOI: 10.3390/ijms23105707] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Revised: 05/18/2022] [Accepted: 05/19/2022] [Indexed: 12/10/2022] Open
Abstract
Neurofibromin, the main RasGAP in the nervous system, is a 2818 aa protein with several poorly characterized functional domains. Mutations in the NF1-encoding gene lead to an autosomal dominant syndrome, neurofibromatosis, with an incidence of 1 out of 3000 newborns. Missense mutations spread in the Sec14-PH-encoding sequences as well. Structural data could not highlight the defect in mutant Sec14-PH functionality. By performing molecular dynamics simulations at different temperatures, we found that the lid-lock is fundamental for the structural interdependence of the NF1 bipartite Sec14-PH domain. In fact, increased flexibility in the lid-lock loop, observed for the K1750Δ mutant, leads to disconnection of the two subdomains and can affect the stability of the Sec14 subdomain.
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9
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Anastasaki C, Mo J, Chen JK, Chatterjee J, Pan Y, Scheaffer SM, Cobb O, Monje M, Le LQ, Gutmann DH. Neuronal hyperexcitability drives central and peripheral nervous system tumor progression in models of neurofibromatosis-1. Nat Commun 2022; 13:2785. [PMID: 35589737 PMCID: PMC9120229 DOI: 10.1038/s41467-022-30466-6] [Citation(s) in RCA: 32] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Accepted: 05/03/2022] [Indexed: 11/16/2022] Open
Abstract
Neuronal activity is emerging as a driver of central and peripheral nervous system cancers. Here, we examined neuronal physiology in mouse models of the tumor predisposition syndrome Neurofibromatosis-1 (NF1), with different propensities to develop nervous system cancers. We show that central and peripheral nervous system neurons from mice with tumor-causing Nf1 gene mutations exhibit hyperexcitability and increased secretion of activity-dependent tumor-promoting paracrine factors. We discovered a neurofibroma mitogen (COL1A2) produced by peripheral neurons in an activity-regulated manner, which increases NF1-deficient Schwann cell proliferation, establishing that neurofibromas are regulated by neuronal activity. In contrast, mice with the Arg1809Cys Nf1 mutation, found in NF1 patients lacking neurofibromas or optic gliomas, do not exhibit neuronal hyperexcitability or develop these NF1-associated tumors. The hyperexcitability of tumor-prone Nf1-mutant neurons results from reduced NF1-regulated hyperpolarization-activated cyclic nucleotide-gated (HCN) channel function, such that neuronal excitability, activity-regulated paracrine factor production, and tumor progression are attenuated by HCN channel activation. Collectively, these findings reveal that NF1 mutations act at the level of neurons to modify tumor predisposition by increasing neuronal excitability and activity-regulated paracrine factor production. Neuronal activity is emerging as a driver of nervous system tumors. Here, the authors show in mouse models of Neurofibromatosis-1 (NF1) that Nf1 mutations differentially drive both central and peripheral nervous system tumor growth in mice through reduced hyperpolarization-activated cyclic nucleotide-gated (HCN) channel function.
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Affiliation(s)
- Corina Anastasaki
- Department of Neurology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Juan Mo
- Department of Dermatology, University of Texas, Southwestern, Dallas, TX, 75390, USA
| | - Ji-Kang Chen
- Department of Neurology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Jit Chatterjee
- Department of Neurology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Yuan Pan
- Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, 94305, USA
| | - Suzanne M Scheaffer
- Department of Neurology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Olivia Cobb
- Department of Neurology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Michelle Monje
- Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, 94305, USA.,Howard Hughes Medical Institute, Stanford University, Stanford, CA, 94305, USA
| | - Lu Q Le
- Department of Dermatology, University of Texas, Southwestern, Dallas, TX, 75390, USA
| | - David H Gutmann
- Department of Neurology, Washington University School of Medicine, St. Louis, MO, 63110, USA.
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10
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Chaker-Margot M, Werten S, Dunzendorfer-Matt T, Lechner S, Ruepp A, Scheffzek K, Maier T. Structural basis of activation of the tumor suppressor protein neurofibromin. Mol Cell 2022; 82:1288-1296.e5. [PMID: 35353986 DOI: 10.1016/j.molcel.2022.03.011] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Revised: 01/14/2022] [Accepted: 03/03/2022] [Indexed: 12/15/2022]
Abstract
Mutations in the NF1 gene cause the familial genetic disease neurofibromatosis type I, as well as predisposition to cancer. The NF1 gene product, neurofibromin, is a GTPase-activating protein and acts as a tumor suppressor by negatively regulating the small GTPase, Ras. However, structural insights into neurofibromin activation remain incompletely defined. Here, we provide cryoelectron microscopy (cryo-EM) structures that reveal an extended neurofibromin homodimer in two functional states: an auto-inhibited state with occluded Ras-binding site and an asymmetric open state with an exposed Ras-binding site. Mechanistically, the transition to the active conformation is stimulated by nucleotide binding, which releases a lock that tethers the catalytic domain to an extended helical repeat scaffold in the occluded state. Structure-guided mutational analysis supports functional relevance of allosteric control. Disease-causing mutations are mapped and primarily impact neurofibromin stability. Our findings suggest a role for nucleotides in neurofibromin regulation and may lead to therapeutic modulation of Ras signaling.
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Affiliation(s)
| | - Sebastiaan Werten
- Institute of Biological Chemistry, Biocenter, Medical University of Innsbruck, Innsbruck 6020, Austria
| | | | - Stefan Lechner
- Institute of Biological Chemistry, Biocenter, Medical University of Innsbruck, Innsbruck 6020, Austria
| | - Angela Ruepp
- Institute of Biological Chemistry, Biocenter, Medical University of Innsbruck, Innsbruck 6020, Austria
| | - Klaus Scheffzek
- Institute of Biological Chemistry, Biocenter, Medical University of Innsbruck, Innsbruck 6020, Austria.
| | - Timm Maier
- Biozentrum, University of Basel, 4056 Basel, Switzerland.
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11
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Mo J, Moye SL, McKay RM, Le LQ. Neurofibromin and suppression of tumorigenesis: beyond the GAP. Oncogene 2022; 41:1235-1251. [PMID: 35066574 PMCID: PMC9063229 DOI: 10.1038/s41388-021-02156-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Revised: 12/01/2021] [Accepted: 12/13/2021] [Indexed: 12/15/2022]
Abstract
Neurofibromatosis type 1 (NF1) is an autosomal dominant genetic disease and one of the most common inherited tumor predisposition syndromes, affecting 1 in 3000 individuals worldwide. The NF1 gene encodes neurofibromin, a large protein with RAS GTP-ase activating (RAS-GAP) activity, and loss of NF1 results in increased RAS signaling. Neurofibromin contains many other domains, and there is considerable evidence that these domains play a role in some manifestations of NF1. Investigating the role of these domains as well as the various signaling pathways that neurofibromin regulates and interacts with will provide a better understanding of how neurofibromin acts to suppress tumor development and potentially open new therapeutic avenues. In this review, we discuss what is known about the structure of neurofibromin, its interactions with other proteins and signaling pathways, its role in development and differentiation, and its function as a tumor suppressor. Finally, we discuss the latest research on potential therapeutics for neurofibromin-deficient neoplasms.
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Affiliation(s)
- Juan Mo
- Department of Dermatology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390-9069, USA
| | - Stefanie L. Moye
- Department of Dermatology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390-9069, USA
| | - Renee M. McKay
- Department of Dermatology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390-9069, USA
| | - Lu Q. Le
- Department of Dermatology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390-9069, USA,Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390-9069, USA,UTSW Comprehensive Neurofibromatosis Clinic, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390-9069, USA,Hamon Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390-9069, USA,O’Donnell Brain Institute, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390-9069, USA,Correspondence and requests for materials should be addressed to Lu Q. Le.
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12
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Lutz S, Van Dyke K, Feraru MA, Albert FW. Multiple epistatic DNA variants in a single gene affect gene expression in trans. Genetics 2022; 220:iyab208. [PMID: 34791209 PMCID: PMC8733636 DOI: 10.1093/genetics/iyab208] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Accepted: 11/09/2021] [Indexed: 01/08/2023] Open
Abstract
DNA variants that alter gene expression in trans are important sources of phenotypic variation. Nevertheless, the identity of trans-acting variants remains poorly understood. Single causal variants in several genes have been reported to affect the expression of numerous distant genes in trans. Whether these simple molecular architectures are representative of trans-acting variation is unknown. Here, we studied the large RAS signaling regulator gene IRA2, which contains variants with extensive trans-acting effects on gene expression in the yeast Saccharomyces cerevisiae. We used systematic CRISPR-based genome engineering and a sensitive phenotyping strategy to dissect causal variants to the nucleotide level. In contrast to the simple molecular architectures known so far, IRA2 contained at least seven causal nonsynonymous variants. The effects of these variants were modulated by nonadditive, epistatic interactions. Two variants at the 5'-end affected gene expression and growth only when combined with a third variant that also had no effect in isolation. Our findings indicate that the molecular basis of trans-acting genetic variation may be considerably more complex than previously appreciated.
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Affiliation(s)
- Sheila Lutz
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN 55455, USA
| | - Krisna Van Dyke
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN 55455, USA
| | - Matthew A Feraru
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN 55455, USA
| | - Frank W Albert
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN 55455, USA
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13
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Shirota M, Kinoshita K. Current status and future perspectives of the evaluation of missense variants by using three-dimensional structures of proteins. Biophys Physicobiol 2022; 19:e190023. [PMID: 36071878 PMCID: PMC9402263 DOI: 10.2142/biophysico.bppb-v19.0023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Accepted: 07/12/2022] [Indexed: 12/01/2022] Open
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14
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Neurofibromatosis Type 1 Gene Alterations Define Specific Features of a Subset of Glioblastomas. Int J Mol Sci 2021; 23:ijms23010352. [PMID: 35008787 PMCID: PMC8745708 DOI: 10.3390/ijms23010352] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2021] [Revised: 12/14/2021] [Accepted: 12/24/2021] [Indexed: 02/08/2023] Open
Abstract
Neurofibromatosis type 1 (NF1) gene mutations or alterations occur within neurofibromatosis type 1 as well as in many different malignant tumours on the somatic level. In glioblastoma, NF1 loss of function plays a major role in inducing the mesenchymal (MES) subtype and, therefore defining the most aggressive glioblastoma. This is associated with an immune signature and mediated via the NF1–MAPK–FOSL1 axis. Specifically, increased invasion seems to be regulated via mutations in the leucine-rich domain (LRD) of the NF1 gene product neurofibromin. Novel targets for therapy may arise from neurofibromin deficiency-associated cellular mechanisms that are summarised in this review.
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15
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The cryo-EM structure of the human neurofibromin dimer reveals the molecular basis for neurofibromatosis type 1. Nat Struct Mol Biol 2021; 28:982-988. [PMID: 34887559 DOI: 10.1038/s41594-021-00687-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Accepted: 10/14/2021] [Indexed: 12/18/2022]
Abstract
Neurofibromin (NF1) mutations cause neurofibromatosis type 1 and drive numerous cancers, including breast and brain tumors. NF1 inhibits cellular proliferation through its guanosine triphosphatase-activating protein (GAP) activity against rat sarcoma (RAS). In the present study, cryo-electron microscope studies reveal that the human ~640-kDa NF1 homodimer features a gigantic 30 × 10 nm array of α-helices that form a core lemniscate-shaped scaffold. Three-dimensional variability analysis captured the catalytic GAP-related domain and lipid-binding SEC-PH domains positioned against the core scaffold in a closed, autoinhibited conformation. We postulate that interaction with the plasma membrane may release the closed conformation to promote RAS inactivation. Our structural data further allow us to map the location of disease-associated NF1 variants and provide a long-sought-after structural explanation for the extreme susceptibility of the molecule to loss-of-function mutations. Collectively these findings present potential new routes for therapeutic modulation of the RAS pathway.
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16
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Naschberger A, Baradaran R, Rupp B, Carroni M. The structure of neurofibromin isoform 2 reveals different functional states. Nature 2021; 599:315-319. [PMID: 34707296 PMCID: PMC8580823 DOI: 10.1038/s41586-021-04024-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Accepted: 09/13/2021] [Indexed: 01/20/2023]
Abstract
The autosomal dominant monogenetic disease neurofibromatosis type 1 (NF1) affects approximately one in 3,000 individuals and is caused by mutations in the NF1 tumour suppressor gene, leading to dysfunction in the protein neurofibromin (Nf1)1,2. As a GTPase-activating protein, a key function of Nf1 is repression of the Ras oncogene signalling cascade. We determined the human Nf1 dimer structure at an overall resolution of 3.3 Å. The cryo-electron microscopy structure reveals domain organization and structural details of the Nf1 exon 23a splicing3 isoform 2 in a closed, self-inhibited, Zn-stabilized state and an open state. In the closed conformation, HEAT/ARM core domains shield the GTPase-activating protein-related domain (GRD) so that Ras binding is sterically inhibited. In a distinctly different, open conformation of one protomer, a large-scale movement of the GRD occurs, which is necessary to access Ras, whereas Sec14-PH reorients to allow interaction with the cellular membrane4. Zn incubation of Nf1 leads to reduced Ras-GAP activity with both protomers in the self-inhibited, closed conformation stabilized by a Zn binding site between the N-HEAT/ARM domain and the GRD–Sec14-PH linker. The transition between closed, self-inhibited states of Nf1 and open states provides guidance for targeted studies deciphering the complex molecular mechanism behind the widespread neurofibromatosis syndrome and Nf1 dysfunction in carcinogenesis. Cryo-EM structure of Nf1 protein is reported, revealing closed and open conformations that regulate interaction with Ras oncogene, setting the stage for understanding the mechanistic action of Nf1 and how disease mutations lead to dysfunction.
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Affiliation(s)
- Andreas Naschberger
- SciLifeLab, Department of Biochemistry and Biophysics, Stockholm University, Solna, Sweden.,Institute of Genetic Epidemiology, Medical University Innsbruck, Innsbruck, Austria
| | - Rozbeh Baradaran
- SciLifeLab, Department of Biochemistry and Biophysics, Stockholm University, Solna, Sweden
| | - Bernhard Rupp
- Institute of Genetic Epidemiology, Medical University Innsbruck, Innsbruck, Austria. .,k.-k. Hofkristallamt, San Diego, CA, USA.
| | - Marta Carroni
- SciLifeLab, Department of Biochemistry and Biophysics, Stockholm University, Solna, Sweden.
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17
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Rabab’h O, Gharaibeh A, Al-Ramadan A, Ismail M, Shah J. Pharmacological Approaches in Neurofibromatosis Type 1-Associated Nervous System Tumors. Cancers (Basel) 2021; 13:cancers13153880. [PMID: 34359780 PMCID: PMC8345673 DOI: 10.3390/cancers13153880] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Revised: 07/28/2021] [Accepted: 07/28/2021] [Indexed: 12/11/2022] Open
Abstract
Simple Summary Neurofibromatosis type 1 (NF1) is a common cancer predisposition genetic disease that is associated with significant morbidity and mortality. In this literature review, we discuss the major pathways in the nervous system that are affected by NF1, tumors that are associated with NF1, drugs that target these pathways, and genetic models of NF1. We also summarize the latest updates from clinical trials that are evaluating pharmacological agents to treat these tumors and discuss the efforts that are being made to cure the disease in the future Abstract Neurofibromatosis type 1 is an autosomal dominant genetic disease and a common tumor predisposition syndrome that affects 1 in 3000 to 4000 patients in the USA. Although studies have been conducted to better understand and manage this disease, the underlying pathogenesis of neurofibromatosis type 1 has not been completely elucidated, and this disease is still associated with significant morbidity and mortality. Treatment options are limited to surgery with chemotherapy for tumors in cases of malignant transformation. In this review, we summarize the advances in the development of targeted pharmacological interventions for neurofibromatosis type 1 and related conditions.
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Affiliation(s)
- Omar Rabab’h
- Insight Research Institute, Flint, MI 48507, USA; (O.R.); (A.G.); (A.A.-R.); (M.I.)
- Center for Cognition and Neuroethics, University of Michigan-Flint, Flint, MI 48502, USA
| | - Abeer Gharaibeh
- Insight Research Institute, Flint, MI 48507, USA; (O.R.); (A.G.); (A.A.-R.); (M.I.)
- Center for Cognition and Neuroethics, University of Michigan-Flint, Flint, MI 48502, USA
- Insight Institute of Neurosurgery & Neuroscience, Flint, MI 48507, USA
- Insight Surgical Hospital, Warren, MI 48091, USA
| | - Ali Al-Ramadan
- Insight Research Institute, Flint, MI 48507, USA; (O.R.); (A.G.); (A.A.-R.); (M.I.)
- Center for Cognition and Neuroethics, University of Michigan-Flint, Flint, MI 48502, USA
| | - Manar Ismail
- Insight Research Institute, Flint, MI 48507, USA; (O.R.); (A.G.); (A.A.-R.); (M.I.)
| | - Jawad Shah
- Insight Research Institute, Flint, MI 48507, USA; (O.R.); (A.G.); (A.A.-R.); (M.I.)
- Center for Cognition and Neuroethics, University of Michigan-Flint, Flint, MI 48502, USA
- Insight Institute of Neurosurgery & Neuroscience, Flint, MI 48507, USA
- Insight Surgical Hospital, Warren, MI 48091, USA
- Department of Medicine, College of Human Medicine, Michigan State University, East Lansing, MI 48824, USA
- Correspondence:
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18
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Bergoug M, Doudeau M, Godin F, Mosrin C, Vallée B, Bénédetti H. Neurofibromin Structure, Functions and Regulation. Cells 2020; 9:cells9112365. [PMID: 33121128 PMCID: PMC7692384 DOI: 10.3390/cells9112365] [Citation(s) in RCA: 55] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Revised: 10/21/2020] [Accepted: 10/26/2020] [Indexed: 12/13/2022] Open
Abstract
Neurofibromin is a large and multifunctional protein encoded by the tumor suppressor gene NF1, mutations of which cause the tumor predisposition syndrome neurofibromatosis type 1 (NF1). Over the last three decades, studies of neurofibromin structure, interacting partners, and functions have shown that it is involved in several cell signaling pathways, including the Ras/MAPK, Akt/mTOR, ROCK/LIMK/cofilin, and cAMP/PKA pathways, and regulates many fundamental cellular processes, such as proliferation and migration, cytoskeletal dynamics, neurite outgrowth, dendritic-spine density, and dopamine levels. The crystallographic structure has been resolved for two of its functional domains, GRD (GAP-related (GTPase-activating protein) domain) and SecPH, and its post-translational modifications studied, showing it to be localized to several cell compartments. These findings have been of particular interest in the identification of many therapeutic targets and in the proposal of various therapeutic strategies to treat the symptoms of NF1. In this review, we provide an overview of the literature on neurofibromin structure, function, interactions, and regulation and highlight the relationships between them.
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Nuclear Isoforms of Neurofibromin Are Required for Proper Spindle Organization and Chromosome Segregation. Cells 2020; 9:cells9112348. [PMID: 33114250 PMCID: PMC7690890 DOI: 10.3390/cells9112348] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2020] [Revised: 10/20/2020] [Accepted: 10/22/2020] [Indexed: 12/30/2022] Open
Abstract
Mitotic spindles are highly organized, microtubule (MT)-based, transient structures that serve the fundamental function of unerring chromosome segregation during cell division and thus of genomic stability during tissue morphogenesis and homeostasis. Hence, a multitude of MT-associated proteins (MAPs) regulates the dynamic assembly of MTs in preparation for mitosis. Some tumor suppressors, normally functioning to prevent tumor development, have now emerged as significant MAPs. Among those, neurofibromin, the product of the Neurofibromatosis-1 gene (NF1), a major Ras GTPase activating protein (RasGAP) in neural cells, controls also the critical function of chromosome congression in astrocytic cellular contexts. Cell type- and development-regulated splicings may lead to the inclusion or exclusion of NF1exon51, which bears a nuclear localization sequence (NLS) for nuclear import at G2; yet the functions of the produced NLS and ΔNLS neurofibromin isoforms have not been previously addressed. By using a lentiviral shRNA system, we have generated glioblastoma SF268 cell lines with conditional knockdown of NLS or ΔNLS transcripts. In dissecting the roles of NLS or ΔNLS neurofibromins, we found that NLS-neurofibromin knockdown led to increased density of cytosolic MTs but loss of MT intersections, anastral spindles featuring large hollows and abnormal chromosome positioning, and finally abnormal chromosome segregation and increased micronuclei frequency. Therefore, we propose that NLS neurofibromin isoforms exert prominent mitotic functions.
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20
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Sherekar M, Han SW, Ghirlando R, Messing S, Drew M, Rabara D, Waybright T, Juneja P, O'Neill H, Stanley CB, Bhowmik D, Ramanathan A, Subramaniam S, Nissley DV, Gillette W, McCormick F, Esposito D. Biochemical and structural analyses reveal that the tumor suppressor neurofibromin (NF1) forms a high-affinity dimer. J Biol Chem 2020. [DOI: 10.1016/s0021-9258(17)49919-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
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21
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Sherekar M, Han SW, Ghirlando R, Messing S, Drew M, Rabara D, Waybright T, Juneja P, O'Neill H, Stanley CB, Bhowmik D, Ramanathan A, Subramaniam S, Nissley DV, Gillette W, McCormick F, Esposito D. Biochemical and structural analyses reveal that the tumor suppressor neurofibromin (NF1) forms a high-affinity dimer. J Biol Chem 2019; 295:1105-1119. [PMID: 31836666 PMCID: PMC6983858 DOI: 10.1074/jbc.ra119.010934] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Revised: 12/10/2019] [Indexed: 12/28/2022] Open
Abstract
Neurofibromin is a tumor suppressor encoded by the NF1 gene, which is mutated in Rasopathy disease neurofibromatosis type I. Defects in NF1 lead to aberrant signaling through the RAS–mitogen-activated protein kinase pathway due to disruption of the neurofibromin GTPase-activating function on RAS family small GTPases. Very little is known about the function of most of the neurofibromin protein; to date, biochemical and structural data exist only for its GAP domain and a region containing a Sec-PH motif. To better understand the role of this large protein, here we carried out a series of biochemical and biophysical experiments, including size-exclusion chromatography–multiangle light scattering (SEC-MALS), small-angle X-ray and neutron scattering, and analytical ultracentrifugation, indicating that full-length neurofibromin forms a high-affinity dimer. We observed that neurofibromin dimerization also occurs in human cells and likely has biological and clinical implications. Analysis of purified full-length and truncated neurofibromin variants by negative-stain EM revealed the overall architecture of the dimer and predicted the potential interactions that contribute to the dimer interface. We could reconstitute structures resembling high-affinity full-length dimers by mixing N- and C-terminal protein domains in vitro. The reconstituted neurofibromin was capable of GTPase activation in vitro, and co-expression of the two domains in human cells effectively recapitulated the activity of full-length neurofibromin. Taken together, these results suggest how neurofibromin dimers might form and be stabilized within the cell.
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Affiliation(s)
- Mukul Sherekar
- NCI RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, Maryland 21702
| | - Sae-Won Han
- Helen Diller Comprehensive Cancer Center, University of California San Francisco, San Francisco, California 94158.,Department of Internal Medicine, Seoul National University Hospital, Seoul 03080, Republic of Korea
| | - Rodolfo Ghirlando
- Laboratory of Molecular Biology, NIDDK, National Institutes of Health, Bethesda, Maryland 20892
| | - Simon Messing
- NCI RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, Maryland 21702
| | - Matthew Drew
- NCI RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, Maryland 21702
| | - Dana Rabara
- NCI RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, Maryland 21702
| | - Timothy Waybright
- NCI RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, Maryland 21702
| | - Puneet Juneja
- Robert P. Apkarian Integrated Electron Microscopy Core, Emory University, Atlanta, Georgia 30322
| | - Hugh O'Neill
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830
| | | | | | | | - Sriram Subramaniam
- Frederick National Laboratory for Cancer Research, Frederick, Maryland 21702.,Department of Biochemistry, Life Sciences Center, University of British Columbia, Vancouver, British Columbia V6T1Z3, Canada
| | - Dwight V Nissley
- NCI RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, Maryland 21702
| | - William Gillette
- NCI RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, Maryland 21702
| | - Frank McCormick
- NCI RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, Maryland 21702.,Helen Diller Comprehensive Cancer Center, University of California San Francisco, San Francisco, California 94158
| | - Dominic Esposito
- NCI RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, Maryland 21702
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22
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Nishimura T, Stefan CJ. Specialized ER membrane domains for lipid metabolism and transport. Biochim Biophys Acta Mol Cell Biol Lipids 2019; 1865:158492. [PMID: 31349025 DOI: 10.1016/j.bbalip.2019.07.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2019] [Revised: 07/02/2019] [Accepted: 07/03/2019] [Indexed: 11/15/2022]
Abstract
The endoplasmic reticulum (ER) is a highly organized organelle that performs vital functions including de novo membrane lipid synthesis and transport. Accordingly, numerous lipid biosynthesis enzymes are localized in the ER membrane. However, it is now evident that lipid metabolism is sub-compartmentalized within the ER and that lipid biosynthetic enzymes engage with lipid transfer proteins (LTPs) to rapidly shuttle newly synthesized lipids from the ER to other organelles. As such, intimate relationships between lipid metabolism and lipid transfer pathways exist within the ER network. Notably, certain LTPs enhance the activities of lipid metabolizing enzymes; likewise, lipid metabolism can ensure the specificity of LTP transfer/exchange reactions. Yet, our understanding of these mutual relationships is still emerging. Here, we highlight past and recent key findings on specialized ER membrane domains involved in efficient lipid metabolism and transport and consider unresolved issues in the field.
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Affiliation(s)
- Taki Nishimura
- MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London WC1E 6BT, UK.
| | - Christopher J Stefan
- MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London WC1E 6BT, UK.
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23
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Fadhlullah SFB, Halim NBA, Yeo JYT, Ho RLY, Um P, Ang BT, Tang C, Ng WH, Virshup DM, Ho IAW. Pathogenic mutations in neurofibromin identifies a leucine-rich domain regulating glioma cell invasiveness. Oncogene 2019; 38:5367-5380. [PMID: 30967630 PMCID: PMC6755990 DOI: 10.1038/s41388-019-0809-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Revised: 03/14/2019] [Accepted: 03/23/2019] [Indexed: 12/25/2022]
Abstract
Glioblastoma (GBM) is the most aggressive tumor of the brain. NF1, a tumor suppressor gene and RAS-GTPase, is one of the highly mutated genes in GBM. Dysregulated NF1 expression promotes cell invasion, proliferation, and tumorigenesis. Loss of NF1 expression in glioblastoma is associated with increased aggressiveness of the tumor. Here, we show that NF1-loss in patient-derived glioma cells using shRNA increases self-renewal, heightens cell invasion, and promotes mesenchymal subtype and epithelial mesenchymal transition-specific gene expression that enhances tumorigenesis. The neurofibromin protein contains at least four major domains, with the GAP-related domain being the most well-studied. In this study, we report that the leucine-rich domain (LRD) of neurofibromin inhibits invasion of human glioblastoma cells without affecting their proliferation. Moreover, under conditions tested, the NF1-LRD fails to hydrolyze Ras-GTP to Ras-GDP, suggesting that its suppressive function is independent of Ras signaling. We further demonstrate that rare variants within the NF1-LRD domain found in a subset of the patients are pathogenic and reduce NF1-LRD’s invasion suppressive function. Taken together, our results show, for the first time, that NF1-LRD inhibits glioma invasion, and provides evidence of a previously unrecognized function of NF1-LRD in glioma biology.
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Affiliation(s)
- Siti Farah Bte Fadhlullah
- Molecular Neurotherapeutics Laboratory, National Neuroscience Institute, Singapore, 308433, Singapore.,Lucence Diagnostics Pte Ltd., Singapore, Singapore
| | | | - Jacqueline Y T Yeo
- Molecular Neurotherapeutics Laboratory, National Neuroscience Institute, Singapore, 308433, Singapore
| | - Rachel L Y Ho
- Molecular Neurotherapeutics Laboratory, National Neuroscience Institute, Singapore, 308433, Singapore
| | - Phoebe Um
- Molecular Neurotherapeutics Laboratory, National Neuroscience Institute, Singapore, 308433, Singapore.,University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Beng Ti Ang
- Department of Neurosurgery, National Neuroscience Institute, Singapore, 308433, Singapore.,Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 119228, Singapore.,Singapore Institute for Clinical Sciences, A*STAR, Singapore, 117609, Singapore.,Duke-NUS Medical School, Singapore, 169857, Singapore
| | - Carol Tang
- Department of Research, National Neuroscience Institute, Singapore, 308433, Singapore.,Program in Cancer and Stem Cell Biology, Duke-NUS Medical School, Singapore, 169857, Singapore.,Division of Cellular and Molecular Research, National Cancer Centre, Singapore, 169610, Singapore
| | - Wai H Ng
- Department of Neurosurgery, National Neuroscience Institute, Singapore, 308433, Singapore
| | - David M Virshup
- Program in Cancer and Stem Cell Biology, Duke-NUS Medical School, Singapore, 169857, Singapore.,Department of Pediatrics, Duke University School of Medicine, Durham, NC, 27703, USA
| | - Ivy A W Ho
- Molecular Neurotherapeutics Laboratory, National Neuroscience Institute, Singapore, 308433, Singapore. .,Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 119228, Singapore. .,Duke-NUS Medical School, Singapore, 169857, Singapore.
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24
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Scheffzek K, Shivalingaiah G. Ras-Specific GTPase-Activating Proteins-Structures, Mechanisms, and Interactions. Cold Spring Harb Perspect Med 2019; 9:cshperspect.a031500. [PMID: 30104198 DOI: 10.1101/cshperspect.a031500] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Ras-specific GTPase-activating proteins (RasGAPs) down-regulate the biological activity of Ras proteins by accelerating their intrinsic rate of GTP hydrolysis, basically by a transition state stabilizing mechanism. Oncogenic Ras is commonly not sensitive to RasGAPs caused by interference of mutants with the electronic or steric requirements of the transition state, resulting in up-regulation of activated Ras in respective cells. RasGAPs are modular proteins containing a helical catalytic RasGAP module surrounded by smaller domains that are frequently involved in the subcellular localization or contributing to regulatory features of their host proteins. In this review, we summarize current knowledge about RasGAP structure, mechanism, regulation, and dual-substrate specificity and discuss in some detail neurofibromin, one of the most important negative Ras regulators in cellular growth control and neuronal function.
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Affiliation(s)
- Klaus Scheffzek
- Division of Biological Chemistry (Biocenter), Medical University of Innsbruck, A-6020 Innsbruck, Austria
| | - Giridhar Shivalingaiah
- Division of Biological Chemistry (Biocenter), Medical University of Innsbruck, A-6020 Innsbruck, Austria
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25
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Frayling IM, Mautner VF, van Minkelen R, Kallionpaa RA, Aktaş S, Baralle D, Ben-Shachar S, Callaway A, Cox H, Eccles DM, Ferkal S, LaDuca H, Lázaro C, Rogers MT, Stuenkel AJ, Summerour P, Varan A, Yap YS, Zehou O, Peltonen J, Evans DG, Wolkenstein P, Upadhyaya M. Breast cancer risk in neurofibromatosis type 1 is a function of the type of NF1 gene mutation: a new genotype-phenotype correlation. J Med Genet 2018; 56:209-219. [DOI: 10.1136/jmedgenet-2018-105599] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Revised: 10/30/2018] [Accepted: 11/15/2018] [Indexed: 01/19/2023]
Abstract
BackgroundNeurofibromatosis type 1 (NF1) predisposes to breast cancer (BC), but no genotype-phenotype correlations have been described.MethodsConstitutional NF1 mutations in 78 patients with NF1 with BC (NF1-BC) were compared with the NF1 Leiden Open Variation Database (n=3432).ResultsNo cases were observed with whole or partial gene deletions (HR 0.10; 95% CI 0.006 to 1.63; p=0.014, Fisher’s exact test). There were no gross relationships with mutation position. Forty-five (64.3%; HR 6.4–83) of the 70 different mutations were more frequent than expected (p<0.05), while 52 (74.3%; HR 5.3–83) were significant when adjusted for multiple comparisons (adjusted p≤0.125; Benjamini-Hochberg). Higher proportions of both nonsense and missense mutations were also observed (adjusted p=0.254; Benjamini-Hochberg). Ten of the 11 missense cases with known age of BC occurred at <50 years (p=0.041). Eighteen cases had BRCA1/2 testing, revealing one BRCA2 mutation.DiscussionThese data strongly support the hypothesis that certain constitutional mutation types, and indeed certain specific variants in NF1 confer different risks of BC. The lack of large deletions and excess of nonsenses and missenses is consistent with gain of function mutations conferring risk of BC, and also that neurofibromin may function as a dimer. The observation that somatic NF1 amplification can occur independently of ERBB2 amplification in sporadic BC supports this concept. A prospective clinical-molecular study of NF1-BC needs to be established to confirm and build on these findings, but regardless of NF1 mutation status patients with NF1-BC warrant testing of other BC-predisposing genes.
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26
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Rozza-de-Menezes RE, Brum CDAI, Gaglionone NC, de Sousa Almeida LM, Andrade-Losso RM, Paiva BVB, Faveret PLS, da Silva AV, Siqueira OHK, Riccardi VM, Cunha KS. Prevalence and clinicopathological characteristics of lipomatous neurofibromas in neurofibromatosis 1: An investigation of 229 cutaneous neurofibromas and a systematic review of the literature. J Cutan Pathol 2018; 45:743-753. [PMID: 29959804 DOI: 10.1111/cup.13315] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Revised: 06/10/2018] [Accepted: 06/25/2018] [Indexed: 12/26/2022]
Abstract
BACKGROUND Lipomatous neurofibroma (Lnf) is a histopathological variant with adipocytes noted among cells of cutaneous neurofibromas. We aimed to investigate the prevalence and clinicopathological features of Lnfs of neurofibromatosis 1 (NF1)-associated cutaneous neurofibromas and to review the literature systematically. We also evaluated the expression of leptin (a hormone involved in lipid metabolism) in neurofibromas to better understand the pathogenesis of Lnfs. METHODS A prospective histologic study was conducted on 229 cutaneous neurofibromas from 85 NF1 individuals. Leptin expression was immunohistochemically evaluated in 111 cutaneous neurofibromas. To systematically review the literature, two authors independently performed literature searches without year restriction. RESULTS Forty (17.5%) neurofibromas were lipomatous. Lnfs were significantly larger lesions and associated with females. Eighteen (7.9%) of all neurofibromas had multinucleated floret-like giant cells, and these were associated with Lnfs. All neurofibromas expressed leptin. We systematically reviewed 13 articles. Three large studies investigated Lnfs mainly in sporadic neurofibromas and suggested that 0.3% to 8.0% of tumors (NF1 and sporadic) are Lnfs. CONCLUSION In NF1, Lnfs are common, mainly in larger tumors and women. All cutaneous NF1-neurofibromas express leptin. It is unknown if the expression of leptin accounts for the lipomatous variant, but it may have a role in the pathogenesis of cutaneous neurofibroma.
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Affiliation(s)
- Rafaela Elvira Rozza-de-Menezes
- Department of Pathology, School of Medicine, Universidade Federal Fluminense, Niterói, Brazil
- Neurofibromatosis National Center (Centro Nacional de Neurofibromatose, CNNF), Rio de Janeiro, Brazil
| | | | | | - Lilian Machado de Sousa Almeida
- Neurofibromatosis National Center (Centro Nacional de Neurofibromatose, CNNF), Rio de Janeiro, Brazil
- Graduate Program in Pathology, School of Medicine, Universidade Federal Fluminense, Niterói, Brazil
| | - Raquel Machado Andrade-Losso
- Neurofibromatosis National Center (Centro Nacional de Neurofibromatose, CNNF), Rio de Janeiro, Brazil
- Graduate Program in Pathology, School of Medicine, Universidade Federal Fluminense, Niterói, Brazil
| | | | | | - André Vallejo da Silva
- Breast Surgery Service, Antônio Pedro University Hospital, Universidade Federal Fluminense, Niterói, Brazil
| | | | | | - Karin Soares Cunha
- Department of Pathology, School of Medicine, Universidade Federal Fluminense, Niterói, Brazil
- Neurofibromatosis National Center (Centro Nacional de Neurofibromatose, CNNF), Rio de Janeiro, Brazil
- Graduate Program in Pathology, School of Medicine, Universidade Federal Fluminense, Niterói, Brazil
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Recent Advances in the Diagnosis and Pathogenesis of Neurofibromatosis Type 1 (NF1)-associated Peripheral Nervous System Neoplasms. Adv Anat Pathol 2018; 25:353-368. [PMID: 29762158 DOI: 10.1097/pap.0000000000000197] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The diagnosis of a neurofibroma or a malignant peripheral nerve sheath tumor (MPNST) often raises the question of whether the patient has the genetic disorder neurofibromatosis type 1 (NF1) as well as how this will impact the patient's outcome, what their risk is for developing additional neoplasms and whether treatment options differ for NF1-associated and sporadic peripheral nerve sheath tumors. Establishing a diagnosis of NF1 is challenging as this disorder has numerous neoplastic and non-neoplastic manifestations which are variably present in individual patients. Further, other genetic diseases affecting the Ras signaling cascade (RASopathies) mimic many of the clinical features of NF1. Here, we review the clinical manifestations of NF1 and compare and contrast them with those of the RASopathies. We also consider current approaches to genetic testing for germline NF1 mutations. We then focus on NF1-associated neurofibromas, considering first the complicated clinical behavior and pathology of these neoplasms and then discussing our current understanding of the genomic abnormalities that drive their pathogenesis, including the mutations encountered in atypical neurofibromas. As several neurofibroma subtypes are capable of undergoing malignant transformation to become MPNSTs, we compare and contrast patient outcomes in sporadic, NF1-associated and radiation-induced MPNSTs, and review the challenging pathology of these lesions. The mutations involved in neurofibroma-MPNST progression, including the recent identification of mutations affecting epigenetic regulators, are then considered. Finally, we explore how our current understanding of neurofibroma and MPNST pathogenesis is informing the design of new therapies for these neoplasms.
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Xu M, Xiong H, Han Y, Li C, Mai S, Huang Z, Ai X, Guo Z, Zeng F, Guo Q. Identification of Mutation Regions on NF1 Responsible for High- and Low-Risk Development of Optic Pathway Glioma in Neurofibromatosis Type I. Front Genet 2018; 9:270. [PMID: 30087692 PMCID: PMC6066643 DOI: 10.3389/fgene.2018.00270] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Accepted: 07/03/2018] [Indexed: 12/30/2022] Open
Abstract
Neurofibromatosis type I is a rare neurocutaneous syndrome resulting from loss-of-function mutations of NF1. The present study sought to determine a correlation between mutation regions on NF1 and the risk of developing optic pathway glioma (OPG) in patients with neurofibromatosis type I. A total of 215 patients with neurofibromatosis type I, from our clinic or previously reported literature, were included in the study after applying strict inclusion and exclusion criteria. Of these, 100 patients with OPG were classified into the OPG group and 115 patients without OPG (aged ≥ 10 years) were assigned to the Non-OPG group. Correlation between different mutation regions and risk of OPG was analyzed. The mutation clustering in the 5′ tertile of NF1 was not significantly different between OPG and Non-OPG groups (P = 0.131). Interestingly, patients with mutations in the cysteine/serine-rich domain of NF1 had a higher risk of developing OPG than patients with mutations in other regions [P = 0.019, adjusted odds ratio (OR) = 2.587, 95% confidence interval (CI) = 1.167–5.736], whereas those in the HEAT-like repeat region had a lower risk (P = 0.036, adjusted OR = 0.396, 95% CI = 0.166–0.942). This study confirms a new correlation between NF1 genotype and OPG phenotype in patients with neurofibromatosis type I, and provides novel insights into molecular functions of neurofibromin.
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Affiliation(s)
- Min Xu
- Department of Dermatology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China
| | - Hui Xiong
- Department of Dermatology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China
| | - Yanfang Han
- Department of Dermatology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China
| | - Chijun Li
- Department of Dermatology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China
| | - Shaozhen Mai
- Department of Dermatology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China.,Department of Dermatology, The Eighth Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
| | - Zhongzhou Huang
- Department of Dermatology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China
| | - Xuechen Ai
- Department of Dermatology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China
| | - Zhixuan Guo
- Department of Dermatology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China
| | - Fanqin Zeng
- Department of Dermatology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China
| | - Qing Guo
- Department of Dermatology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China
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Abstract
In Neurofibromatosis 1 (NF1) germ line loss of function mutations result in reduction of cellular neurofibromin content (NF1+/-, NF1 haploinsufficiency). The Ras-GAP neurofibromin is a very large cytoplasmic protein (2818 AA, 319 kDa) involved in the RAS-MAPK pathway. Aside from regulation of proliferation, it is involved in mechanosensoric of cells. We investigated neurofibromin replacement in cultured human fibroblasts showing reduced amount of neurofibromin. Full length neurofibromin was produced recombinantly in insect cells and purified. Protein transduction into cultured fibroblasts was performed employing cell penetrating peptides along with photochemical internalization. This combination of transduction strategies ensures the intracellular uptake and the translocation to the cytoplasm of neurofibromin. The transduced neurofibromin is functional, indicated by functional rescue of reduced mechanosensoric blindness and reduced RasGAP activity in cultured fibroblasts of NF1 patients or normal fibroblasts treated by NF1 siRNA. Our study shows that recombinant neurofibromin is able to revert cellular effects of NF1 haploinsuffiency in vitro, indicating a use of protein transduction into cells as a potential treatment strategy for the monogenic disease NF1.
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Robinet G, Rioux-Leclercq N, Manunta A, Mathieu R, Tissier F, Peyronnet B, Kammerer-Jacquet SF. [Composite pheochromocytoma: A rare adrenal tumor]. Ann Pathol 2017; 37:158-161. [PMID: 28285811 DOI: 10.1016/j.annpat.2016.10.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Revised: 07/06/2016] [Accepted: 10/04/2016] [Indexed: 11/18/2022]
Abstract
INTRODUCTION Composite pheochromocytoma is a rare tumor of the adrenal medulla composed of pheochromocytoma and neuroblastic tumor. We report the case of a composite pheochromocytoma detected in a patient with neurofibromatosis type 1. CASE REPORT A 61-year-old male patient presented occasional sweats with palpitation and moderate high blood pressure. Urinary catecholamine level was increased. CT scan showed a heterogeneous tumor limited to the adrenal gland. Histologically, the tumor showed two components: pheochromocytoma and ganglioneuroma and was diagnosed as a composite pheochromocytoma. This tumor is particularly associated with neurofibromatosis type 1, the NF1 germline gene mutation may be involved in its physiopathology. CONCLUSION Composite pheochromocytoma is a rare tumor whose pheochromocytoma component is suspected clinically but the final diagnosis is assessed by pathological examination. Prognosis is still difficult to establish due to the rarity of these tumors.
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Affiliation(s)
- Gwladys Robinet
- Service d'anatomie et cytologie pathologiques, CHU Pontchaillou, 2, rue Henri-le-Guilloux, 35033 Rennes cedex 9, France.
| | - Nathalie Rioux-Leclercq
- Service d'anatomie et cytologie pathologiques, CHU Pontchaillou, 2, rue Henri-le-Guilloux, 35033 Rennes cedex 9, France
| | - Andréa Manunta
- Service d'urologie, CHU Pontchaillou, 2, rue Henri-le-Guilloux, 35033 Rennes cedex 9, France
| | - Romain Mathieu
- Service d'urologie, CHU Pontchaillou, 2, rue Henri-le-Guilloux, 35033 Rennes cedex 9, France
| | - Frédérique Tissier
- Service d'anatomie et cytologie pathologiques, hôpital universitaire de La-Pitié-Salpêtrière, 47-83, boulevard de l'Hôpital, 75651 Paris cedex 13, France
| | - Benoit Peyronnet
- Service d'urologie, CHU Pontchaillou, 2, rue Henri-le-Guilloux, 35033 Rennes cedex 9, France
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Xie K, Colgan LA, Dao MT, Muntean BS, Sutton LP, Orlandi C, Boye SL, Boye SE, Shih CC, Li Y, Xu B, Smith RG, Yasuda R, Martemyanov KA. NF1 Is a Direct G Protein Effector Essential for Opioid Signaling to Ras in the Striatum. Curr Biol 2016; 26:2992-3003. [PMID: 27773571 DOI: 10.1016/j.cub.2016.09.010] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Revised: 08/24/2016] [Accepted: 09/07/2016] [Indexed: 01/19/2023]
Abstract
It is well recognized that G-protein-coupled receptors (GPCRs) can activate Ras-regulated kinase pathways to produce lasting changes in neuronal function. Mechanisms by which GPCRs transduce these signals and their relevance to brain disorders are not well understood. Here, we identify a major Ras regulator, neurofibromin 1 (NF1), as a direct effector of GPCR signaling via Gβγ subunits in the striatum. We find that binding of Gβγ to NF1 inhibits its ability to inactivate Ras. Deletion of NF1 in striatal neurons prevents the opioid-receptor-induced activation of Ras and eliminates its coupling to Akt-mTOR-signaling pathway. By acting in the striatal medium spiny neurons of the direct pathway, NF1 regulates opioid-induced changes in Ras activity, thereby sensitizing mice to psychomotor and rewarding effects of morphine. These results delineate a novel mechanism of GPCR signaling to Ras pathways and establish a critical role of NF1 in opioid addiction.
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Affiliation(s)
- Keqiang Xie
- Department of Neuroscience, The Scripps Research Institute, 130 Scripps Way, Jupiter, FL 33458, USA
| | - Lesley A Colgan
- Max Planck Florida Institute for Neuroscience, 1 Max Planck Way, Jupiter, FL 33458, USA
| | - Maria T Dao
- Department of Metabolism and Aging, The Scripps Research Institute, 120 Scripps Way, Jupiter, FL 33458, USA
| | - Brian S Muntean
- Department of Neuroscience, The Scripps Research Institute, 130 Scripps Way, Jupiter, FL 33458, USA
| | - Laurie P Sutton
- Department of Neuroscience, The Scripps Research Institute, 130 Scripps Way, Jupiter, FL 33458, USA
| | - Cesare Orlandi
- Department of Neuroscience, The Scripps Research Institute, 130 Scripps Way, Jupiter, FL 33458, USA
| | - Sanford L Boye
- Department of Ophthalmology, University of Florida, 1395 Center Drive, Gainesville, FL 32610, USA
| | - Shannon E Boye
- Department of Ophthalmology, University of Florida, 1395 Center Drive, Gainesville, FL 32610, USA
| | - Chien-Cheng Shih
- Department of Neuroscience, The Scripps Research Institute, 130 Scripps Way, Jupiter, FL 33458, USA
| | - Yuqing Li
- Department of Neurology, University of Florida, 1600 SW Archer Road, Gainesville, FL 32610, USA
| | - Baoji Xu
- Department of Neuroscience, The Scripps Research Institute, 130 Scripps Way, Jupiter, FL 33458, USA
| | - Roy G Smith
- Department of Metabolism and Aging, The Scripps Research Institute, 120 Scripps Way, Jupiter, FL 33458, USA
| | - Ryohei Yasuda
- Max Planck Florida Institute for Neuroscience, 1 Max Planck Way, Jupiter, FL 33458, USA
| | - Kirill A Martemyanov
- Department of Neuroscience, The Scripps Research Institute, 130 Scripps Way, Jupiter, FL 33458, USA.
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Physical interaction between neurofibromin and serotonin 5-HT6 receptor promotes receptor constitutive activity. Proc Natl Acad Sci U S A 2016; 113:12310-12315. [PMID: 27791021 DOI: 10.1073/pnas.1600914113] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Active G protein-coupled receptor (GPCR) conformations not only are promoted by agonists but also occur in their absence, leading to constitutive activity. Association of GPCRs with intracellular protein partners might be one of the mechanisms underlying GPCR constitutive activity. Here, we show that serotonin 5 hydroxytryptamine 6 (5-HT6) receptor constitutively activates the Gs/adenylyl cyclase pathway in various cell types, including neurons. Constitutive activity is strongly reduced by silencing expression of the Ras-GTPase activating protein (Ras-GAP) neurofibromin, a 5-HT6 receptor partner. Neurofibromin is a multidomain protein encoded by the NF1 gene, the mutation of which causes Neurofibromatosis type 1 (NF1), a genetic disorder characterized by multiple benign and malignant nervous system tumors and cognitive deficits. Disrupting association of 5-HT6 receptor with neurofibromin Pleckstrin Homology (PH) domain also inhibits receptor constitutive activity, and PH domain expression rescues 5-HT6 receptor-operated cAMP signaling in neurofibromin-deficient cells. Furthermore, PH domains carrying mutations identified in NF1 patients that prevent interaction with the 5-HT6 receptor fail to rescue receptor constitutive activity in neurofibromin-depleted cells. Further supporting a role of neurofibromin in agonist-independent Gs signaling elicited by native receptors, the phosphorylation of cAMP-responsive element-binding protein (CREB) is strongly decreased in prefrontal cortex of Nf1+/- mice compared with WT mice. Moreover, systemic administration of a 5-HT6 receptor inverse agonist reduces CREB phosphorylation in prefrontal cortex of WT mice but not Nf1+/- mice. Collectively, these findings suggest that disrupting 5-HT6 receptor-neurofibromin interaction prevents agonist-independent 5-HT6 receptor-operated cAMP signaling in prefrontal cortex, an effect that might underlie neuronal abnormalities in NF1 patients.
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33
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Fidler DR, Murphy SE, Courtis K, Antonoudiou P, El-Tohamy R, Ient J, Levine TP. Using HHsearch to tackle proteins of unknown function: A pilot study with PH domains. Traffic 2016; 17:1214-1226. [PMID: 27601190 PMCID: PMC5091641 DOI: 10.1111/tra.12432] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Revised: 08/30/2016] [Accepted: 08/30/2016] [Indexed: 01/08/2023]
Abstract
Advances in membrane cell biology are hampered by the relatively high proportion of proteins with no known function. Such proteins are largely or entirely devoid of structurally significant domain annotations. Structural bioinformaticians have developed profile‐profile tools such as HHsearch (online version called HHpred), which can detect remote homologies that are missed by tools used to annotate databases. Here we have applied HHsearch to study a single structural fold in a single model organism as proof of principle. In the entire clan of protein domains sharing the pleckstrin homology domain fold in yeast, systematic application of HHsearch accurately identified known PH‐like domains. It also predicted 16 new domains in 13 yeast proteins many of which are implicated in intracellular traffic. One of these was Vps13p, where we confirmed the functional importance of the predicted PH‐like domain. Even though such predictions require considerable work to be corroborated, they are useful first steps. HHsearch should be applied more widely, particularly across entire proteomes of model organisms, to significantly improve database annotations.
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Affiliation(s)
- David R Fidler
- Department of Cell Biology, UCL Institute of Ophthalmology, London, UK
| | - Sarah E Murphy
- Department of Cell Biology, UCL Institute of Ophthalmology, London, UK
| | - Katherine Courtis
- Department of Cell Biology, UCL Institute of Ophthalmology, London, UK
| | | | - Rana El-Tohamy
- Department of Cell Biology, UCL Institute of Ophthalmology, London, UK
| | - Jonathan Ient
- Department of Cell Biology, UCL Institute of Ophthalmology, London, UK
| | - Timothy P Levine
- Department of Cell Biology, UCL Institute of Ophthalmology, London, UK.
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34
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Lipid transfer proteins and the tuning of compartmental identity in the Golgi apparatus. Chem Phys Lipids 2016; 200:42-61. [DOI: 10.1016/j.chemphyslip.2016.06.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2016] [Revised: 06/21/2016] [Accepted: 06/22/2016] [Indexed: 11/23/2022]
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35
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The neurofibromin recruitment factor Spred1 binds to the GAP related domain without affecting Ras inactivation. Proc Natl Acad Sci U S A 2016; 113:7497-502. [PMID: 27313208 DOI: 10.1073/pnas.1607298113] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Neurofibromatosis type 1 (NF1) and Legius syndrome are related diseases with partially overlapping symptoms caused by alterations of the tumor suppressor genes NF1 (encoding the protein neurofibromin) and SPRED1 (encoding sprouty-related, EVH1 domain-containing protein 1, Spred1), respectively. Both proteins are negative regulators of Ras/MAPK signaling with neurofibromin functioning as a Ras-specific GTPase activating protein (GAP) and Spred1 acting on hitherto undefined components of the pathway. Importantly, neurofibromin has been identified as a key protein in the development of cancer, as it is genetically altered in a large number of sporadic human malignancies unrelated to NF1. Spred1 has previously been demonstrated to interact with neurofibromin via its N-terminal Ena/VASP Homology 1 (EVH1) domain and to mediate membrane translocation of its target dependent on its C-terminal Sprouty domain. However, the region of neurofibromin required for the interaction with Spred1 has remained unclear. Here we show that the EVH1 domain of Spred1 binds to the noncatalytic (GAPex) portion of the GAP-related domain (GRD) of neurofibromin. Binding is compatible with simultaneous binding of Ras and does not interfere with GAP activity. Our study points to a potential targeting function of the GAPex subdomain of neurofibromin that is present in all known canonical RasGAPs.
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36
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Fitzpatrick ER, Hu T, Ciccarelli BT, Whitehead IP. Regulation of vesicle transport and cell motility by Golgi-localized Dbs. Small GTPases 2015; 5:1-12. [PMID: 25483302 DOI: 10.4161/sgtp.28570] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
DBS/MCF2L has been recently identified as a risk locus for osteoarthritis. It encodes a guanine nucleotide exchange factor (Dbs) that has been shown to regulate both normal and tumor cell motility. In the current study, we have determined that endogenous Dbs is predominantly expressed as 2 isoforms, a 130 kDa form (Dbs-130) that is localized to the Golgi complex, and an 80 kDa form (Dbs-80) that is localized to the endoplasmic reticulum (ER). We have previously described an inhibitor that binds to the RhoGEF domain of Dbs and blocks its transforming activity. Here we show that the inhibitor localizes to the Golgi, where it specifically interacts with Dbs-130. Inhibition of endogenous Dbs-130 activity is associated with reduced levels of activated Cdc42, enlarged Golgi, and resistance to Brefeldin A-mediated Golgi dispersal, suggesting a role for Dbs in vesicle transport. Cells treated with the inhibitor exhibit normal protein transport from the ER to the Golgi, but are defective in transport from the Golgi to the plasma membrane. Inhibition of Dbs-130 in MDA-MB-231 human breast tumor cells limits motility in both transwell and wound healing assays, but appears to have no effect on the organization of the microtubule cytoskeleton. The reduced motility is associated with a failure to reorient the Golgi toward the leading edge. This is consistent with the Golgi localization, and suggests that the Dbs-130 regulates aspects of the secretory pathway that are required to support cell polarization during directed migration.
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Key Words
- BFA, Brefeldin A
- COP1, coat protein
- DAPI, 4’, 6-diamidino-2-phenylindole
- DH, Dbl homology
- Dbs
- Dbs, Dbl's big sister
- ECL, electrochemiluminescence
- ER, endoplasmic reticulum
- FACS, fluorescence-activated cell sorting
- FGD1, faciogenital dysplasia 1 protein
- GEF, guanine nucleotide exchange factor
- GFP, green fluorescent protein
- HA, hemagglutinin
- HM, homogenization medium
- MCF2L
- MTOC, microtubule organizing center
- NF-1, neurofibromatosis type 1
- PAK3, p21 protein-activated kinase 3
- PBS, phosphate buffered saline
- PH, pleckstrin homology
- Rho
- SH3, Src homology 3
- VSVG, vesicular stomatitis virus-G
- WGA, wheat germ agglutinin
- breast cancer
- cell motility
- golgi complex
- guanine nucleotide exchange factor
- osteoarthritis
- rtPCR, real-time polymerase chain reaction
- siRNA, small inhibitory RNA
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Affiliation(s)
- Ethan R Fitzpatrick
- a Department of Microbiology and Molecular Genetics; The New Jersey Medical School-Cancer Center; Rutgers Biomedical and Health Sciences ; Newark , NJ USA
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Structural insights on cholesterol endosynthesis: Binding of squalene and 2,3-oxidosqualene to supernatant protein factor. J Struct Biol 2015; 190:261-70. [DOI: 10.1016/j.jsb.2015.05.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2015] [Revised: 05/08/2015] [Accepted: 05/11/2015] [Indexed: 11/24/2022]
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38
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Arg(1809) substitution in neurofibromin: further evidence of a genotype-phenotype correlation in neurofibromatosis type 1. Eur J Hum Genet 2015; 23:1460-1. [PMID: 25966637 DOI: 10.1038/ejhg.2015.93] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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Ratner N, Miller SJ. A RASopathy gene commonly mutated in cancer: the neurofibromatosis type 1 tumour suppressor. Nat Rev Cancer 2015; 15:290-301. [PMID: 25877329 PMCID: PMC4822336 DOI: 10.1038/nrc3911] [Citation(s) in RCA: 292] [Impact Index Per Article: 32.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Neurofibromatosis type 1 (NF1) is a common genetic disorder that predisposes affected individuals to tumours. The NF1 gene encodes a RAS GTPase-activating protein called neurofibromin and is one of several genes that (when mutant) affect RAS-MAPK signalling, causing related diseases collectively known as RASopathies. Several RASopathies, beyond NF1, are cancer predisposition syndromes. Somatic NF1 mutations also occur in 5-10% of human sporadic cancers and may contribute to resistance to therapy. To highlight areas for investigation in RASopathies and sporadic tumours with NF1 mutations, we summarize current knowledge of NF1 disease, the NF1 gene and neurofibromin, neurofibromin signalling pathways and recent developments in NF1 therapeutics.
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Affiliation(s)
- Nancy Ratner
- Division of Experimental Hematology and Cancer Biology, Cancer and Blood Diseases Institute, Cincinnati Children's Hospital, 3333 Burnet Avenue, Cincinnati, Ohio 45229, USA
| | - Shyra J Miller
- Division of Experimental Hematology and Cancer Biology, Cancer and Blood Diseases Institute, Cincinnati Children's Hospital, 3333 Burnet Avenue, Cincinnati, Ohio 45229, USA
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Miller MB, Vishwanatha KS, Mains RE, Eipper BA. An N-terminal Amphipathic Helix Binds Phosphoinositides and Enhances Kalirin Sec14 Domain-mediated Membrane Interactions. J Biol Chem 2015; 290:13541-55. [PMID: 25861993 DOI: 10.1074/jbc.m115.636746] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Indexed: 11/06/2022] Open
Abstract
Previous studies revealed an essential role for the lipid-binding Sec14 domain of kalirin (KalSec14), but its mechanism of action is not well understood. Because alternative promoter usage appends unique N-terminal peptides to the KalSec14 domain, we used biophysical, biochemical, and cell biological approaches to examine the two major products, bKalSec14 and cKalSec14. Promoter B encodes a charged, unstructured peptide, whereas promoter C encodes an amphipathic helix (Kal-C-helix). Both bKalSec14 and cKalSec14 interacted with lipids in PIP strip and liposome flotation assays, with significantly greater binding by cKalSec14 in both assays. Disruption of the hydrophobic face of the Kal-C-helix in cKalSec14KKED eliminated its increased liposome binding. Although cKalSec14 showed significantly reduced binding to liposomes lacking phosphatidylinositol phosphates or cholesterol, liposome binding by bKalSec14 and cKalSec14KKED was not affected. When expressed in AtT-20 cells, bKalSec14-GFP was diffusely localized, whereas cKalSec14-GFP localized to the trans-Golgi network and secretory granules. The amphipathic C-helix was sufficient for this localization. When AtT-20 cells were treated with a cell-permeant derivative of the Kal-C-helix (Kal-C-helix-Arg9), we observed increased secretion of a product stored in mature secretory granules, with no effect on basal secretion; a cell-permeant control peptide (Kal-C-helixKKED-Arg9) did not have this effect. Through its ability to control expression of a novel, phosphoinositide-binding amphipathic helix, Kalrn promoter usage is expected to affect function.
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Affiliation(s)
| | | | | | - Betty A Eipper
- From the Departments of Neuroscience and Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, Connecticut 06030
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Bloomfield G, Traynor D, Sander SP, Veltman DM, Pachebat JA, Kay RR. Neurofibromin controls macropinocytosis and phagocytosis in Dictyostelium. eLife 2015; 4. [PMID: 25815683 PMCID: PMC4374526 DOI: 10.7554/elife.04940] [Citation(s) in RCA: 95] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2014] [Accepted: 03/06/2015] [Indexed: 02/06/2023] Open
Abstract
Cells use phagocytosis and macropinocytosis to internalise bulk material, which in phagotrophic organisms supplies the nutrients necessary for growth. Wildtype Dictyostelium amoebae feed on bacteria, but for decades laboratory work has relied on axenic mutants that can also grow on liquid media. We used forward genetics to identify the causative gene underlying this phenotype. This gene encodes the RasGAP Neurofibromin (NF1). Loss of NF1 enables axenic growth by increasing fluid uptake. Mutants form outsized macropinosomes which are promoted by greater Ras and PI3K activity at sites of endocytosis. Relatedly, NF1 mutants can ingest larger-than-normal particles using phagocytosis. An NF1 reporter is recruited to nascent macropinosomes, suggesting that NF1 limits their size by locally inhibiting Ras signalling. Our results link NF1 with macropinocytosis and phagocytosis for the first time, and we propose that NF1 evolved in early phagotrophs to spatially modulate Ras activity, thereby constraining and shaping their feeding structures. DOI:http://dx.doi.org/10.7554/eLife.04940.001 Dictyostelium amoebae are microbes that feed on bacteria living in the soil. They are unusual in that the amoebae can survive and grow in a single-celled form, but when food is scarce, many individual cells can gather together to form a simple multicellular organism. To feed on bacteria, the amoebae use a process called phagocytosis, which starts with the membrane that surrounds the cell growing outwards to completely surround the bacteria. This leads to the bacteria entering the amoeba within a membrane compartment called a vesicle, where they are broken down into small molecules by enzymes. The cells can also take up fluids and dissolved molecules using a similar process called macropinocytosis. With its short and relatively simple lifestyle, Dictyostelium is often used in research to study phagocytosis, cell movement and other processes that are also found in larger organisms. For example, some immune cells in animals use phagocytosis to capture and destroy invading microbes. Most studies using Dictyostelium as a model have used amoebae with genetic mutations that allow them to be grown in liquid cultures in the laboratory without needing to feed on bacteria. The mutations allow the ‘mutant’ amoebae to take up more liquid and dissolved nutrients by macropinocytosis, but it is not known where in the genome these mutations are. Here, Bloomfield et al. used genome sequencing to reveal that these mutations alter a gene that encodes a protein called Neurofibromin. The experiments show that the loss of Neurofibromin increases the amount of fluid taken up by the amoebae through macropinocytosis, and also enables the amoebae to take up larger-than-normal particles during phagocytosis. The experiments suggest that Neurofibromin controls both phagocytosis and macropinocytosis by inhibiting the activity of another protein called Ras. Neurofibromin is found in animals and many other organisms so Bloomfield et al. propose that it is an ancient protein that evolved in early single-celled organisms to control the size and shape of their feeding structures. In humans, mutations in the gene that encodes the Neurofibromin protein can lead to the development of a severe disorder—called Neurofibromatosis type 1—in which tumours form in the nervous system. Given that tumour cells can use phagocytosis and macropinocytosis to gain nutrients as they grow, understanding how this protein works in the Dictyostelium amoebae may help to inform future efforts to develop treatments for this human disease. DOI:http://dx.doi.org/10.7554/eLife.04940.002
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Affiliation(s)
| | - David Traynor
- MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Sophia P Sander
- MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Douwe M Veltman
- MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Justin A Pachebat
- Department of Plant Sciences, University of Cambridge, Cambridge, United Kingdom
| | - Robert R Kay
- MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
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Pinna V, Lanari V, Daniele P, Consoli F, Agolini E, Margiotti K, Bottillo I, Torrente I, Bruselles A, Fusilli C, Ficcadenti A, Bargiacchi S, Trevisson E, Forzan M, Giustini S, Leoni C, Zampino G, Digilio MC, Dallapiccola B, Clementi M, Tartaglia M, De Luca A. p.Arg1809Cys substitution in neurofibromin is associated with a distinctive NF1 phenotype without neurofibromas. Eur J Hum Genet 2014; 23:1068-71. [PMID: 25370043 DOI: 10.1038/ejhg.2014.243] [Citation(s) in RCA: 95] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2014] [Revised: 09/26/2014] [Accepted: 10/01/2014] [Indexed: 02/05/2023] Open
Abstract
Analysis of 786 NF1 mutation-positive subjects with clinical diagnosis of neurofibromatosis type 1 (NF1) allowed to identify the heterozygous c.5425C>T missense variant (p.Arg1809Cys) in six (0.7%) unrelated probands (three familial and three sporadic cases), all exhibiting a mild form of disease. Detailed clinical characterization of these subjects and other eight affected relatives showed that all individuals had multiple cafè-au-lait spots, frequently associated with skinfold freckling, but absence of discrete cutaneous or plexiform neurofibromas, Lisch nodules, typical NF1 osseous lesions or symptomatic optic gliomas. Facial features in half of the individuals were suggestive of Noonan syndrome. Our finding and revision of the literature consistently indicate that the c.5425C>T change is associated with a distinctive, mild form of NF1, providing new data with direct impact on genetic counseling and patient management.
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Affiliation(s)
- Valentina Pinna
- IRCCS-Casa Sollievo della Sofferenza Hospital, Mendel Institute, Rome, Italy
| | - Valentina Lanari
- IRCCS-Casa Sollievo della Sofferenza Hospital, Mendel Institute, Rome, Italy
| | - Paola Daniele
- IRCCS-Casa Sollievo della Sofferenza Hospital, Mendel Institute, Rome, Italy
| | - Federica Consoli
- IRCCS-Casa Sollievo della Sofferenza Hospital, Mendel Institute, Rome, Italy
| | - Emanuele Agolini
- IRCCS-Casa Sollievo della Sofferenza Hospital, Mendel Institute, Rome, Italy
| | - Katia Margiotti
- 1] IRCCS-Casa Sollievo della Sofferenza Hospital, Mendel Institute, Rome, Italy [2] PRABB-Centro Integrato di Ricerca, Campus Bio-Medico University, Rome, Italy
| | - Irene Bottillo
- 1] IRCCS-Casa Sollievo della Sofferenza Hospital, Mendel Institute, Rome, Italy [2] Division of Medical Genetics, Department of Molecular Medicine, San Camillo-Forlanini Hospital, Sapienza University, Rome, Italy
| | - Isabella Torrente
- 1] IRCCS-Casa Sollievo della Sofferenza Hospital, Mendel Institute, Rome, Italy [2] San Camillo-Forlanini Hospital, Rome, Italy
| | - Alessandro Bruselles
- Dipartimento di Ematologia, Oncologia e Medicina Molecolare, Istituto Superiore di Sanità, Rome, Italy
| | - Caterina Fusilli
- IRCCS-Casa Sollievo della Sofferenza Hospital, Mendel Institute, Rome, Italy
| | - Anna Ficcadenti
- Pediatric Division, Department of Clinical Sciences, Rare Diseases Regional Centre, Polytechnic University of Marche Ospedali Riuniti, Ancona, Italy
| | - Sara Bargiacchi
- Genetics and Molecular Medicine Unit, Anna Meyer Children's University Hospital, Florence, Italy
| | - Eva Trevisson
- Clinical Genetics Unit, Department of Woman and Child Health, University of Padova, Padova, Italy
| | - Monica Forzan
- Clinical Genetics Unit, Department of Woman and Child Health, University of Padova, Padova, Italy
| | - Sandra Giustini
- Department of Dermatology, Sapienza University of Rome, Policlinico Umberto I, Rome, Italy
| | - Chiara Leoni
- Istituto di Clinica Pediatrica, Università Cattolica del Sacro Cuore, Rome, Italy
| | - Giuseppe Zampino
- Istituto di Clinica Pediatrica, Università Cattolica del Sacro Cuore, Rome, Italy
| | | | | | - Maurizio Clementi
- Clinical Genetics Unit, Department of Woman and Child Health, University of Padova, Padova, Italy
| | - Marco Tartaglia
- Dipartimento di Ematologia, Oncologia e Medicina Molecolare, Istituto Superiore di Sanità, Rome, Italy
| | - Alessandro De Luca
- IRCCS-Casa Sollievo della Sofferenza Hospital, Mendel Institute, Rome, Italy
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Maertens O, Cichowski K. An expanding role for RAS GTPase activating proteins (RAS GAPs) in cancer. Adv Biol Regul 2014; 55:1-14. [PMID: 24814062 DOI: 10.1016/j.jbior.2014.04.002] [Citation(s) in RCA: 119] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2014] [Revised: 04/16/2014] [Accepted: 04/16/2014] [Indexed: 10/25/2022]
Abstract
The RAS pathway is one of the most commonly deregulated pathways in human cancer. Mutations in RAS genes occur in nearly 30% of all human tumors. However in some tumor types RAS mutations are conspicuously absent or rare, despite the fact that RAS and downstream effector pathways are hyperactivated. Recently, RAS GTPase Activating Proteins (RAS GAPs) have emerged as an expanding class of tumor suppressors that, when inactivated, provide an alternative mechanism of activating RAS. RAS GAPs normally turn off RAS by catalyzing the hydrolysis of RAS-GTP. As such, the loss of a RAS GAP would be expected to promote excessive RAS activation. Indeed, this is the case for the NF1 gene, which plays an established role in a familial tumor predisposition syndrome and a variety of sporadic cancers. However, there are 13 additional RAS GAP family members in the human genome. We are only now beginning to understand why there are so many RAS GAPs, how they differentially function, and what their potential role(s) in human cancer are. This review will focus on our current understanding of RAS GAPs in human disease and will highlight important outstanding questions.
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Affiliation(s)
- Ophélia Maertens
- Genetics Division, Department of Medicine, Brigham and Women's Hospital, Boston, MA 02115, USA; Harvard Medical School, Boston, MA 02115, USA
| | - Karen Cichowski
- Genetics Division, Department of Medicine, Brigham and Women's Hospital, Boston, MA 02115, USA; Harvard Medical School, Boston, MA 02115, USA; Ludwig Center at Dana-Farber/Harvard Cancer Center, Boston, MA 02115, USA.
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Abstract
Small GTPases use GDP/GTP alternation to actuate a variety of functional switches that are pivotal for cell dynamics. The GTPase switch is turned on by GEFs, which stimulate dissociation of the tightly bound GDP, and turned off by GAPs, which accelerate the intrinsically sluggish hydrolysis of GTP. For Ras, Rho, and Rab GTPases, this switch incorporates a membrane/cytosol alternation regulated by GDIs and GDI-like proteins. The structures and core mechanisms of representative members of small GTPase regulators from most families have now been elucidated, illuminating their general traits combined with scores of unique features. Recent studies reveal that small GTPase regulators have themselves unexpectedly sophisticated regulatory mechanisms, by which they process cellular signals and build up specific cell responses. These mechanisms include multilayered autoinhibition with stepwise release, feedback loops mediated by the activated GTPase, feed-forward signaling flow between regulators and effectors, and a phosphorylation code for RhoGDIs. The flipside of these highly integrated functions is that they make small GTPase regulators susceptible to biochemical abnormalities that are directly correlated with diseases, notably a striking number of missense mutations in congenital diseases, and susceptible to bacterial mimics of GEFs, GAPs, and GDIs that take command of small GTPases in infections. This review presents an overview of the current knowledge of these many facets of small GTPase regulation.
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Affiliation(s)
- Jacqueline Cherfils
- Laboratoire d’Enzymologie et Biochimie Structurales, Centre National de la Recherche Scientifique, Centre deRecherche de Gif, Gif-sur-Yvette, France
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King PD, Lubeck BA, Lapinski PE. Nonredundant functions for Ras GTPase-activating proteins in tissue homeostasis. Sci Signal 2013; 6:re1. [PMID: 23443682 DOI: 10.1126/scisignal.2003669] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Inactivation of the small guanosine triphosphate-binding protein Ras during receptor signal transduction is mediated by Ras guanosine triphosphatase (GTPase)-activating proteins (RasGAPs). Ten different RasGAPs have been identified and have overlapping patterns of tissue distribution. However, genetic analyses are revealing critical nonredundant functions for each RasGAP in tissue homeostasis and as regulators of disease processes in mouse and man. Here, we discuss advances in understanding the role of RasGAPs in the maintenance of tissue integrity.
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Affiliation(s)
- Philip D King
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
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Curwin AJ, LeBlanc MA, Fairn GD, McMaster CR. Localization of lipid raft proteins to the plasma membrane is a major function of the phospholipid transfer protein Sec14. PLoS One 2013; 8:e55388. [PMID: 23383173 PMCID: PMC3559501 DOI: 10.1371/journal.pone.0055388] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2012] [Accepted: 12/28/2012] [Indexed: 11/30/2022] Open
Abstract
The Sec14 protein domain is a conserved tertiary structure that binds hydrophobic ligands. The Sec14 protein from Saccharomyces cerevisiae is essential with studies of S. cerevisiae Sec14 cellular function facilitated by a sole temperature sensitive allele, sec14ts. The sec14ts allele encodes a protein with a point mutation resulting in a single amino acid change, Sec14G266D. In this study results from a genome-wide genetic screen, and pharmacological data, provide evidence that the Sec14G266D protein is present at a reduced level compared to wild type Sec14 due to its being targeted to the proteosome. Increased expression of the sec14ts allele ameliorated growth arrest, but did not restore the defects in membrane accumulation or vesicular transport known to be defective in sec14ts cells. We determined that trafficking and localization of two well characterized lipid raft resident proteins, Pma1 and Fus-Mid-GFP, were aberrant in sec14ts cells. Localization of both lipid raft proteins was restored upon increased expression of the sec14ts allele. We suggest that a major function provided by Sec14 is trafficking and localization of lipid raft proteins.
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Affiliation(s)
- Amy J. Curwin
- Department of Pharmacology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Marissa A. LeBlanc
- Department of Pharmacology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Gregory D. Fairn
- Department of Pharmacology, Dalhousie University, Halifax, Nova Scotia, Canada
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In silico prediction and in vitro characterization of multifunctional human RNase3. BIOMED RESEARCH INTERNATIONAL 2013; 2013:170398. [PMID: 23484086 PMCID: PMC3581242 DOI: 10.1155/2013/170398] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/31/2012] [Accepted: 12/02/2012] [Indexed: 12/18/2022]
Abstract
Human ribonucleases A (hRNaseA) superfamily consists of thirteen members with high-structure similarities but exhibits divergent physiological functions other than RNase activity. Evolution of hRNaseA superfamily has gained novel functions which may be preserved in a unique region or domain to account for additional molecular interactions. hRNase3 has multiple functions including ribonucleolytic, heparan sulfate (HS) binding, cellular binding, endocytic, lipid destabilization, cytotoxic, and antimicrobial activities. In this study, three putative multifunctional regions, 34RWRCK38 (HBR1), 75RSRFR79 (HBR2), and 101RPGRR105 (HBR3), of hRNase3 have been identified employing in silico sequence analysis and validated employing in vitro activity assays. A heparin binding peptide containing HBR1 is characterized to act as a key element associated with HS binding, cellular binding, and lipid binding activities. In this study, we provide novel insights to identify functional regions of hRNase3 that may have implications for all hRNaseA superfamily members.
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Vallée B, Doudeau M, Godin F, Gombault A, Tchalikian A, de Tauzia ML, Bénédetti H. Nf1 RasGAP inhibition of LIMK2 mediates a new cross-talk between Ras and Rho pathways. PLoS One 2012; 7:e47283. [PMID: 23082153 PMCID: PMC3474823 DOI: 10.1371/journal.pone.0047283] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2012] [Accepted: 09/13/2012] [Indexed: 01/03/2023] Open
Abstract
BACKGROUND Ras GTPases mediate numerous biological processes through their ability to cycle between an inactive GDP-bound form and an active GTP-bound form. Guanine nucleotide exchange factors (GEFs) favor the formation of the active Ras-GTP, whereas GTPase activating proteins (GAPs) promote the formation of inactive Ras-GDP. Numerous studies have established complex signaling cross-talks between Ras GTPases and other members of the superfamily of small GTPases. GEFs were thought to play a major role in these cross-talks. However, recently GAPs were also shown to play crucial roles in these processes. Among RasGAPs, Nf1 is of special interest. Nf1 is responsible for the genetic disease Neurofibromatosis type I, and recent data strongly suggest that this RasGAP connects different signaling pathways. METHODOLOGY/PRINCIPAL FINDINGS In order to know if the RasGAP Nf1 might play a role in connecting Ras GTPases to other small GTPase pathways, we systematically looked for new partners of Nf1, by performing a yeast two-hybrid screening on its SecPH domain. LIMK2, a major kinase of the Rho/ROCK/LIMK2/cofilin pathway, was identified in this screening. We confirmed this interaction by co-immunoprecipitation experiments, and further characterized it. We also demonstrated its specificity: the close related homolog of LIMK2, LIMK1, does not interact with the SecPH domain of Nf1. We then showed that SecPH partially inhibits the kinase activity of LIMK2 on cofilin. Our results furthermore suggest a precise mechanism for this inhibition: in fact, SecPH would specifically prevent LIMK2 activation by ROCK, its upstream regulator. CONCLUSIONS/SIGNIFICANCE Although previous data had already connected Nf1 to actin cytoskeleton dynamics, our study provides for the first time possible detailed molecular requirements of this involvement. Nf1/LIMK2 interaction and inhibition allows to directly connect neurofibromatosis type I to actin cytoskeleton remodeling, and provides evidence that the RasGAP Nf1 mediates a new cross-talk between Ras and Rho signaling pathways within the superfamily of small GTPases.
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Affiliation(s)
- Béatrice Vallée
- Centre de Biophysique Moléculaire, Centre Nationale de la Recherche Scientifique (CNRS), University of Orléans and Institut National de la Santé et de la Recherche Médicale (INSERM), Orléans, France
| | - Michel Doudeau
- Centre de Biophysique Moléculaire, Centre Nationale de la Recherche Scientifique (CNRS), University of Orléans and Institut National de la Santé et de la Recherche Médicale (INSERM), Orléans, France
| | - Fabienne Godin
- Centre de Biophysique Moléculaire, Centre Nationale de la Recherche Scientifique (CNRS), University of Orléans and Institut National de la Santé et de la Recherche Médicale (INSERM), Orléans, France
| | | | | | | | - Hélène Bénédetti
- Centre de Biophysique Moléculaire, Centre Nationale de la Recherche Scientifique (CNRS), University of Orléans and Institut National de la Santé et de la Recherche Médicale (INSERM), Orléans, France
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Abstract
Mutations in the SPRED1 (Sprouty-related protein with an EVH [Ena/Vasp homology] domain 1) and NF1 (neurofibromatosis 1) genes underlie clinically related human disorders. The NF1-encoded protein neurofibromin is a Ras GTPase-activating protein (GAP) and can directly limit Ras activity. Spred proteins also negatively regulate Ras signaling, but the mechanism by which they do so is not clear. In the July 1, 2012, issue of Genes & Development, Stowe and colleagues (pp. 1421-1426) present evidence that Spred1 recruits neurofibromin to the membrane, where it dampens growth factor-induced Ras activity, providing a satisfying explanation for the overlapping features of two human diseases.
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Affiliation(s)
- Andrea I McClatchey
- Massachusetts General Hospital Center for Cancer Research, Department of Pathology, Harvard Medical School, Charlestown, Massachusetts 02129, USA.
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Shin J, Padmanabhan A, de Groh ED, Lee JS, Haidar S, Dahlberg S, Guo F, He S, Wolman MA, Granato M, Lawson ND, Wolfe SA, Kim SH, Solnica-Krezel L, Kanki JP, Ligon KL, Epstein JA, Look AT. Zebrafish neurofibromatosis type 1 genes have redundant functions in tumorigenesis and embryonic development. Dis Model Mech 2012; 5:881-94. [PMID: 22773753 PMCID: PMC3484870 DOI: 10.1242/dmm.009779] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Neurofibromatosis type 1 (NF1) is a common, dominantly inherited genetic disorder that results from mutations in the neurofibromin 1 (NF1) gene. Affected individuals demonstrate abnormalities in neural-crest-derived tissues that include hyperpigmented skin lesions and benign peripheral nerve sheath tumors. NF1 patients also have a predisposition to malignancies including juvenile myelomonocytic leukemia (JMML), optic glioma, glioblastoma, schwannoma and malignant peripheral nerve sheath tumors (MPNSTs). In an effort to better define the molecular and cellular determinants of NF1 disease pathogenesis in vivo, we employed targeted mutagenesis strategies to generate zebrafish harboring stable germline mutations in nf1a and nf1b, orthologues of NF1. Animals homozygous for loss-of-function alleles of nf1a or nf1b alone are phenotypically normal and viable. Homozygous loss of both alleles in combination generates larval phenotypes that resemble aspects of the human disease and results in larval lethality between 7 and 10 days post fertilization. nf1-null larvae demonstrate significant central and peripheral nervous system defects. These include aberrant proliferation and differentiation of oligodendrocyte progenitor cells (OPCs), dysmorphic myelin sheaths and hyperplasia of Schwann cells. Loss of nf1 contributes to tumorigenesis as demonstrated by an accelerated onset and increased penetrance of high-grade gliomas and MPNSTs in adult nf1a+/−; nf1b−/−; p53e7/e7 animals. nf1-null larvae also demonstrate significant motor and learning defects. Importantly, we identify and quantitatively analyze a novel melanophore phenotype in nf1-null larvae, providing the first animal model of the pathognomonic pigmentation lesions of NF1. Together, these findings support a role for nf1a and nf1b as potent tumor suppressor genes that also function in the development of both central and peripheral glial cells as well as melanophores in zebrafish.
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Affiliation(s)
- Jimann Shin
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, and Children's Hospital Boston, Harvard Medical School, Boston, MA 02115, USA
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