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Borkúti P, Kristó I, Szabó A, Kovács Z, Vilmos P. FERM domain-containing proteins are active components of the cell nucleus. Life Sci Alliance 2024; 7:e202302489. [PMID: 38296350 PMCID: PMC10830384 DOI: 10.26508/lsa.202302489] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2023] [Revised: 01/20/2024] [Accepted: 01/22/2024] [Indexed: 02/05/2024] Open
Abstract
The FERM domain is a conserved and widespread protein module that appeared in the common ancestor of amoebae, fungi, and animals, and is therefore now found in a wide variety of species. The primary function of the FERM domain is localizing to the plasma membrane through binding lipids and proteins of the membrane; thus, for a long time, FERM domain-containing proteins (FDCPs) were considered exclusively cytoskeletal. Although their role in the cytoplasm has been extensively studied, the recent discovery of the presence and importance of cytoskeletal proteins in the nucleus suggests that FDCPs might also play an important role in nuclear function. In this review, we collected data on their nuclear localization, transport, and possible functions, which are still scattered throughout the literature, with special regard to the role of the FERM domain in these processes. With this, we would like to draw attention to the exciting, new dimension of the role of FDCPs, their nuclear activity, which could be an interesting novel direction for future research.
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Affiliation(s)
| | | | - Anikó Szabó
- HUN-REN Biological Research Centre, Szeged, Hungary
| | - Zoltán Kovács
- HUN-REN Biological Research Centre, Szeged, Hungary
- Doctoral School of Multidisciplinary Medical Science, University of Szeged, Szeged, Hungary
| | - Péter Vilmos
- HUN-REN Biological Research Centre, Szeged, Hungary
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2
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NF2 Gene Participates in Regulation of the Cell Cycle of Meningiomas by Restoring Spindle Assembly Checkpoint Function and Inhibiting the Binding of Cdc20 Protein to Anaphase Promoting Complex/Cyclosome. World Neurosurg 2021; 158:e245-e255. [PMID: 34728400 DOI: 10.1016/j.wneu.2021.10.163] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2021] [Revised: 10/24/2021] [Accepted: 10/25/2021] [Indexed: 11/23/2022]
Abstract
BACKGROUND The neurofibromatosis type 2 (NF2) gene mutation is the leading genetic event in meningiomas, usually accompanied by malignant features. Dysfunction of the spindle assembly checkpoint (SAC) induces tumorigenesis. However, the crosstalk between NF2 and SAC in meningiomas remains unclear. METHODS Cell proliferation, invasion, apoptosis, and cell cycle of meningiomas were determined by cell counting kit-8 assay, transwell assay, and flow cytometry, respectively. The expression of SAC in meningioma cells was detected by quantitative real-time polymerase chain reaction and Western blot. The interaction between anaphase promoting complex/cyclosome (APC/C) and cell division cycle 20 (Cdc20) protein in meningioma cells was further explored by co-immunoprecipitation. RESULTS We found that the expression of NF2/merlin was low or absent in malignant meningiomas. Overexpression of NF2 suppressed the proliferation and invasion of meningioma cells, prolonged the G2/M phase, and elevated the expression of SAC proteins at posttranscription. Furthermore, the interaction between APC/C and Cdc20 was inhibited by NF2. CONCLUSIONS Our findings suggested that NF2 might restore SAC function by impairing the binding of APC/C and Cdc20, thereby limiting the mitotic rate and inhibiting proliferation of meningiomas.
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Roehrig AE, Klupsch K, Oses-Prieto JA, Chaib S, Henderson S, Emmett W, Young LC, Surinova S, Blees A, Pfeiffer A, Tijani M, Brunk F, Hartig N, Muñoz-Alegre M, Hergovich A, Jennings BH, Burlingame AL, Rodriguez-Viciana P. Cell-cell adhesion regulates Merlin/NF2 interaction with the PAF complex. PLoS One 2021; 16:e0254697. [PMID: 34424918 PMCID: PMC8382200 DOI: 10.1371/journal.pone.0254697] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Accepted: 07/01/2021] [Indexed: 12/14/2022] Open
Abstract
The PAF complex (PAFC) coordinates transcription elongation and mRNA processing and its CDC73/parafibromin subunit functions as a tumour suppressor. The NF2/Merlin tumour suppressor functions both at the cell cortex and nucleus and is a key mediator of contact inhibition but the molecular mechanisms remain unclear. In this study we have used affinity proteomics to identify novel Merlin interacting proteins and show that Merlin forms a complex with multiple proteins involved in RNA processing including the PAFC and the CHD1 chromatin remodeller. Tumour-derived inactivating mutations in both Merlin and the CDC73 PAFC subunit mutually disrupt their interaction and growth suppression by Merlin requires CDC73. Merlin interacts with the PAFC in a cell density-dependent manner and we identify a role for FAT cadherins in regulating the Merlin-PAFC interaction. Our results suggest that in addition to its function within the Hippo pathway, Merlin is part of a tumour suppressor network regulated by cell-cell adhesion which coordinates post-initiation steps of the transcription cycle of genes mediating contact inhibition.
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Affiliation(s)
- Anne E. Roehrig
- UCL Cancer Institute, University College London, London, United Kingdom
| | - Kristina Klupsch
- UCL Cancer Institute, University College London, London, United Kingdom
| | - Juan A. Oses-Prieto
- Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, California, United States of America
| | - Selim Chaib
- UCL Cancer Institute, University College London, London, United Kingdom
| | - Stephen Henderson
- UCL Cancer Institute, University College London, London, United Kingdom
| | - Warren Emmett
- University College London Genetics Institute, London, United Kingdom
| | - Lucy C. Young
- UCL Cancer Institute, University College London, London, United Kingdom
| | - Silvia Surinova
- UCL Cancer Institute, University College London, London, United Kingdom
| | - Andreas Blees
- UCL Cancer Institute, University College London, London, United Kingdom
| | - Anett Pfeiffer
- UCL Cancer Institute, University College London, London, United Kingdom
| | - Maha Tijani
- UCL Cancer Institute, University College London, London, United Kingdom
| | - Fabian Brunk
- UCL Cancer Institute, University College London, London, United Kingdom
| | - Nicole Hartig
- UCL Cancer Institute, University College London, London, United Kingdom
| | | | | | | | - Alma L. Burlingame
- Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, California, United States of America
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4
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Primi MC, Rangarajan ES, Patil DN, Izard T. Conformational flexibility determines the Nf2/merlin tumor suppressor functions. Matrix Biol Plus 2021; 12:100074. [PMID: 34337379 PMCID: PMC8318988 DOI: 10.1016/j.mbplus.2021.100074] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Revised: 06/14/2021] [Accepted: 06/15/2021] [Indexed: 10/26/2022] Open
Abstract
The Neurofibromatosis type 2 gene encodes the Nf2/merlin tumor suppressor protein that is responsible for the regulation of cell proliferation. Once activated, Nf2/merlin modulates adhesive signaling pathways and thereby inhibits cell growth. Nf2/merlin controls oncogenic gene expression by modulating the Hippo pathway. By responding to several physical and biochemical stimuli, Hippo signaling determines contact inhibition of proliferation as well as organ size. The large tumor suppressor (LATS) serine/threonine-protein kinase is the key enzyme in the highly conserved kinase cascade that negatively regulates the activity and localization of the transcriptional coactivators Yes-associated protein (YAP) and its paralogue transcriptional coactivator with PDZ-binding motif (TAZ). Nf2/merlin belongs to the band 4.1, ezrin, radixin, moesin (FERM) gene family that links the actin cytoskeleton to adherens junctions, remodels adherens junctions during epithelial morphogenesis and maintains organized apical surfaces on the plasma cell membrane. Nf2/merlin and ERM proteins have a globular N-terminal cloverleaf head domain, the FERM domain, that binds to the plasma membrane, a central α-helical domain, and a tail domain that binds to its head domain. Here we present the high-resolution crystal structure of Nf2/merlin bound to LATS1 which shows that LATS1 binding to Nf2/merlin displaces the Nf2/merlin tail domain and causes an allosteric shift in the Nf2/merlin α-helix that extends from its FERM domain. This is consistent with the fact that full-length Nf2/merlin binds LATS1 ~10-fold weaker compared to LATS1 binding to the Nf2/merlin-PIP2 complex. Our data increase our understanding of Nf2/merlin biology by providing mechanistic insights into the Hippo pathway that are relevant to several diseases in particular oncogenic features that are associated with cancers.
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Affiliation(s)
- Marina C Primi
- Cell Adhesion Laboratory, Department of Integrative Structural and Computational Biology, The Scripps Research Institute, Jupiter 33458, FL, United States
| | - Erumbi S Rangarajan
- Cell Adhesion Laboratory, Department of Integrative Structural and Computational Biology, The Scripps Research Institute, Jupiter 33458, FL, United States
| | - Dipak N Patil
- Cell Adhesion Laboratory, Department of Integrative Structural and Computational Biology, The Scripps Research Institute, Jupiter 33458, FL, United States
| | - Tina Izard
- Cell Adhesion Laboratory, Department of Integrative Structural and Computational Biology, The Scripps Research Institute, Jupiter 33458, FL, United States
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5
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Lyons Rimmer J, Ercolano E, Baiz D, Makhija M, Berger A, Sells T, Stroud S, Hilton D, Adams CL, Hanemann CO. The Potential of MLN3651 in Combination with Selumetinib as a Treatment for Merlin-Deficient Meningioma. Cancers (Basel) 2020; 12:cancers12071744. [PMID: 32629964 PMCID: PMC7407567 DOI: 10.3390/cancers12071744] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Revised: 06/16/2020] [Accepted: 06/29/2020] [Indexed: 11/30/2022] Open
Abstract
Meningioma is the most common primary intracranial tumour, and surgical resection is the main therapeutic option. Merlin is a tumour suppressor protein that is frequently mutated in meningioma. The activity of the E3 ubiquitin ligase complex, CRL4-DCAF1, and the Raf/MEK/ERK scaffold protein Kinase suppressor of Ras 1 (KSR1) are upregulated in Merlin-deficient tumours, which drives tumour growth. Identifying small molecules that inhibit these key pathways may provide an effective treatment option for patients with meningioma. We used meningioma tissue and primary cells derived from meningioma tumours to investigate the expression of DDB1 and Cullin 4-associated factor 1 (DCAF1) and KSR1, and confirmed these proteins were overexpressed. We then used primary cells to assess the therapeutic potential of MLN3651, a neddylation inhibitor which impacts the activity of the CRL family of E3 ubiquitin ligases and the MAPK/ERK kinase (MEK1/2) inhibitor selumetinib. MLN3651 treatment reduced proliferation and activated apoptosis, whilst increasing Raf/MEK/ERK pathway activation. The combination of MLN3651 and the MEK1/2 inhibitor selumetinib prevented the increase in Raf/MEK/ERK activity, and had an additive effect compared with either treatment alone. Therefore, the combined targeting of CRL4-DCAF1 and Raf/MEK/ERK activity represents an attractive novel strategy in the treatment of Merlin-deficient meningioma.
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Affiliation(s)
- Jade Lyons Rimmer
- Peninsula Schools of Medicine and Dentistry, Institute of Translational and Stratified Medicine, Plymouth University, Plymouth PL68BU, UK; (J.L.R.); (E.E.); (D.B.); (C.L.A.)
| | - Emanuela Ercolano
- Peninsula Schools of Medicine and Dentistry, Institute of Translational and Stratified Medicine, Plymouth University, Plymouth PL68BU, UK; (J.L.R.); (E.E.); (D.B.); (C.L.A.)
| | - Daniele Baiz
- Peninsula Schools of Medicine and Dentistry, Institute of Translational and Stratified Medicine, Plymouth University, Plymouth PL68BU, UK; (J.L.R.); (E.E.); (D.B.); (C.L.A.)
| | | | - Allison Berger
- Millennium Pharmaceuticals, Inc. a Wholly Owned Subsidiary of Takeda Pharmaceutical Company Limited, Cambridge, MA 02139, USA; (A.B.); (T.S.); (S.S.)
| | - Todd Sells
- Millennium Pharmaceuticals, Inc. a Wholly Owned Subsidiary of Takeda Pharmaceutical Company Limited, Cambridge, MA 02139, USA; (A.B.); (T.S.); (S.S.)
| | - Steve Stroud
- Millennium Pharmaceuticals, Inc. a Wholly Owned Subsidiary of Takeda Pharmaceutical Company Limited, Cambridge, MA 02139, USA; (A.B.); (T.S.); (S.S.)
| | - David Hilton
- Department of Histopathology, University Hospitals Plymouth NHS Trust, Plymouth, Devon PL6 8DH, UK;
| | - Claire L. Adams
- Peninsula Schools of Medicine and Dentistry, Institute of Translational and Stratified Medicine, Plymouth University, Plymouth PL68BU, UK; (J.L.R.); (E.E.); (D.B.); (C.L.A.)
| | - C Oliver Hanemann
- Peninsula Schools of Medicine and Dentistry, Institute of Translational and Stratified Medicine, Plymouth University, Plymouth PL68BU, UK; (J.L.R.); (E.E.); (D.B.); (C.L.A.)
- Correspondence: ; Tel.: +44-1752-437-418
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6
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Allegra A, Innao V, Allegra AG, Leanza R, Musolino C. Selective Inhibitors of Nuclear Export in the Treatment of Hematologic Malignancies. CLINICAL LYMPHOMA, MYELOMA & LEUKEMIA 2019; 19:689-698. [PMID: 31543372 DOI: 10.1016/j.clml.2019.08.011] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2019] [Revised: 07/08/2019] [Accepted: 08/22/2019] [Indexed: 02/07/2023]
Abstract
The correct localization of molecules between nucleus and cytoplasm is fundamental for cellular homeostasis and is controlled by a bidirectional transport system. Exportin 1 (XPO1) regulates the passage of numerous cancer-related proteins. In this review, we summarize the development of a novel class of antitumor agents, known as selective inhibitors of nuclear export (SINEs). We report results of preclinical studies and clinical trials, and discuss the mechanism of action of SINEs and their effects in multiple myeloma, non-Hodgkin lymphomas, lymphoblastic leukemia, and acute and chronic myeloid leukemia. In the future, the numerous experimental studies currently underway will allow us to define the role of SINEs and will possibly permit these substances to be introduced into daily clinical practice.
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Affiliation(s)
- Alessandro Allegra
- Division of Hematology, Department of Human Pathology in Adulthood and Childhood "Gaetano Barresi," University of Messina, Messina, Italy.
| | - Vanessa Innao
- Division of Hematology, Department of Human Pathology in Adulthood and Childhood "Gaetano Barresi," University of Messina, Messina, Italy
| | - Andrea Gaetano Allegra
- Division of Hematology, Department of Human Pathology in Adulthood and Childhood "Gaetano Barresi," University of Messina, Messina, Italy
| | - Rossana Leanza
- Division of Hematology, Department of Human Pathology in Adulthood and Childhood "Gaetano Barresi," University of Messina, Messina, Italy
| | - Caterina Musolino
- Division of Hematology, Department of Human Pathology in Adulthood and Childhood "Gaetano Barresi," University of Messina, Messina, Italy
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7
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Mandati V, Del Maestro L, Dingli F, Lombard B, Loew D, Molinie N, Romero S, Bouvard D, Louvard D, Gautreau AM, Pasmant E, Lallemand D. Phosphorylation of Merlin by Aurora A kinase appears necessary for mitotic progression. J Biol Chem 2019; 294:12992-13005. [PMID: 31296571 DOI: 10.1074/jbc.ra118.006937] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 06/25/2019] [Indexed: 01/01/2023] Open
Abstract
Although Merlin's function as a tumor suppressor and regulator of mitogenic signaling networks such as the Ras/rac, Akt, and Hippo pathways is well-documented, in mammals as well as in insects, its role during cell cycle progression remains unclear. In this study, using a combination of approaches, including FACS analysis, time-lapse imaging, immunofluorescence microscopy, and co-immunoprecipitation, we show that Ser-518 of Merlin is a substrate of the Aurora protein kinase A during mitosis and that its phosphorylation facilitates the phosphorylation of a newly discovered site, Thr-581. We found that the expression in HeLa cells of a Merlin variant that is phosphorylation-defective on both sites leads to a defect in centrosomes and mitotic spindles positioning during metaphase and delays the transition from metaphase to anaphase. We also show that the dual mitotic phosphorylation not only reduces Merlin binding to microtubules but also timely modulates ezrin interaction with the cytoskeleton. Finally, we identify several point mutants of Merlin associated with neurofibromatosis type 2 that display an aberrant phosphorylation profile along with defective α-tubulin-binding properties. Altogether, our findings of an Aurora A-mediated interaction of Merlin with α-tubulin and ezrin suggest a potential role for Merlin in cell cycle progression.
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Affiliation(s)
- Vinay Mandati
- CNRS, UMR144, Institute Curie, PSL Research University, F-75005 Paris, France
| | | | - Florent Dingli
- Laboratoire de Spectrométrie de Masse Protéomique, Institute Curie, PSL Research University, Paris, France
| | - Bérangère Lombard
- Laboratoire de Spectrométrie de Masse Protéomique, Institute Curie, PSL Research University, Paris, France
| | - Damarys Loew
- Laboratoire de Spectrométrie de Masse Protéomique, Institute Curie, PSL Research University, Paris, France
| | - Nicolas Molinie
- BIOC, CNRS UMR7654, Institut Polytechnique de Paris, F-91128 Palaiseau, France
| | - Stephane Romero
- BIOC, CNRS UMR7654, Institut Polytechnique de Paris, F-91128 Palaiseau, France
| | - Daniel Bouvard
- INSERM, Institut Albert Bonniot U823, F-38042 Grenoble, France
| | - Daniel Louvard
- CNRS, UMR144, Institute Curie, PSL Research University, F-75005 Paris, France
| | - Alexis M Gautreau
- BIOC, CNRS UMR7654, Institut Polytechnique de Paris, F-91128 Palaiseau, France
| | - Eric Pasmant
- Institut Cochin, INSERM U1016, Université Paris Descartes, Sorbonne Paris Cité, 75014 Paris, France
| | - Dominique Lallemand
- CNRS, UMR144, Institute Curie, PSL Research University, F-75005 Paris, France.
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8
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Hennigan RF, Fletcher JS, Guard S, Ratner N. Proximity biotinylation identifies a set of conformation-specific interactions between Merlin and cell junction proteins. Sci Signal 2019; 12:12/578/eaau8749. [PMID: 31015291 DOI: 10.1126/scisignal.aau8749] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Neurofibromatosis type 2 is an inherited, neoplastic disease associated with schwannomas, meningiomas, and ependymomas and that is caused by inactivation of the tumor suppressor gene NF2 The NF2 gene product, Merlin, has no intrinsic catalytic activity; its tumor suppressor function is mediated through the proteins with which it interacts. We used proximity biotinylation followed by mass spectrometry and direct binding assays to identify proteins that associated with wild-type and various mutant forms of Merlin in immortalized Schwann cells. We defined a set of 52 proteins in close proximity to wild-type Merlin. Most of the Merlin-proximal proteins were components of cell junctional signaling complexes, suggesting that additional potential interaction partners may exist in adherens junctions, tight junctions, and focal adhesions. With mutant forms of Merlin that cannot bind to phosphatidylinositol 4,5-bisphosphate (PIP2) or that constitutively adopt a closed conformation, we confirmed a critical role for PIP2 binding in Merlin function and identified a large cohort of proteins that specifically interacted with Merlin in the closed conformation. Among these proteins, we identified a previously unreported Merlin-binding protein, apoptosis-stimulated p53 protein 2 (ASPP2, also called Tp53bp2), that bound to closed-conformation Merlin predominately through the FERM domain. Our results demonstrate that Merlin is a component of cell junctional mechanosensing complexes and defines a specific set of proteins through which it acts.
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Affiliation(s)
- Robert F Hennigan
- Division of Experimental Hematology and Cancer Biology, Cincinnati Children's Hospital, Cincinnati, OH 45229, USA.
| | - Jonathan S Fletcher
- Division of Experimental Hematology and Cancer Biology, Cincinnati Children's Hospital, Cincinnati, OH 45229, USA
| | - Steven Guard
- Department of Molecular, Cellular & Developmental Biology, University of Colorado Boulder, Boulder, CO 80309, USA
| | - Nancy Ratner
- Division of Experimental Hematology and Cancer Biology, Cincinnati Children's Hospital, Cincinnati, OH 45229, USA
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9
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Gandhi UH, Senapedis W, Baloglu E, Unger TJ, Chari A, Vogl D, Cornell RF. Clinical Implications of Targeting XPO1-mediated Nuclear Export in Multiple Myeloma. CLINICAL LYMPHOMA, MYELOMA & LEUKEMIA 2018; 18:335-345. [PMID: 29610030 DOI: 10.1016/j.clml.2018.03.003] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2017] [Revised: 02/26/2018] [Accepted: 03/08/2018] [Indexed: 12/30/2022]
Abstract
Multiple myeloma (MM) is a malignancy of plasma cells that is typically chronic, and relapse is common. Current therapeutic strategies include combination and sequential treatments with corticosteroids, alkylating agents, proteasomal inhibitors, immunomodulators, and monoclonal antibodies. These drugs prolong survival but ultimately become ineffective. Exportin 1 (XPO1), a nuclear export protein, is overexpressed in MM cells, and knockdown studies have suggested that XPO1 is essential for MM cell survival. Selective inhibitor of nuclear export (SINE) compounds are novel, orally bioavailable class of agents that specifically inhibit XPO1. Selinexor (KPT-330) is the first-in-human SINE compound. Early phase clinical trials have established the safety profile of this agent and have shown promising efficacy in combination with low-dose dexamethasone and other anti-MM agents. The combination of selinexor and dexamethasone has demonstrated activity in "penta-refractory" MM, (ie, MM refractory to the 5 most active anti-MM agents currently used in treatment). We have reviewed the available data on the molecular implications of XPO1 inhibition in MM. We also reviewed the pertinent early phase clinical data with SINE compounds and discuss management strategies for common toxicities encountered with use of selinexor.
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Affiliation(s)
- Ujjawal H Gandhi
- Division of Hematology and Oncology, Vanderbilt University Medical Center, Nashville, TN
| | | | | | | | - Ajai Chari
- Division of Hematology and Oncology, Mount Sinai Hospital, New York, NY
| | - Dan Vogl
- Division of Hematology and Oncology, University of Pennsylvania, Philadelphia, PA
| | - Robert F Cornell
- Division of Hematology and Oncology, Vanderbilt University Medical Center, Nashville, TN.
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10
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Janse van Rensburg HJ, Yang X. Essential signaling in NF2 loss-related tumours: the therapeutic potential of CRL4 DCAF1 and mTOR combined inhibition. J Thorac Dis 2017; 9:3533-3536. [PMID: 29268334 DOI: 10.21037/jtd.2017.09.34] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
| | - Xiaolong Yang
- Department of Pathology and Molecular Medicine, Queen's University, Kingston, Ontario, K7L 3N6, Canada
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11
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The conformation change and tumor suppressor role of Merlin are both independent of Serine 518 phosphorylation. Biochem Biophys Res Commun 2017; 493:46-51. [PMID: 28919412 DOI: 10.1016/j.bbrc.2017.09.077] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Accepted: 09/14/2017] [Indexed: 10/18/2022]
Abstract
Merlin functions as a tumor suppressor and suppresses malignant activity of cancer cells through multiple mechanisms. However, whether Serine 518 phosphorylation regulates the conformation of Merlin as well as the open-closed conformational changes affect Merlin's tumor inhibitory activity remain controversial. In this study, we used different mutants to mimic related conformational states of Merlin and investigated its physiological functions. Our results showed that the phosphorylation at Serine 518 has no influence on Merlin's conformation, subcellular localization, or cell proliferation inhibitory activity. As a fully closed conformational state, the A585W mutant loses the ability to recruit Lats2 to the cell membrane, but it does not affect its subcellular distribution or cell proliferation inhibitory activity. As a fully open conformational state, mimicking the conformation of Merlin isoform II, the ΔEL mutant has the same physiological function as the wild type Merlin isoform I. Collectively, we provide for the first time in vivo evidence that the function of Merlin, as a tumor suppressor is independent of its conformational change.
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12
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Li X, Chen H, Xue L, Pang X, Zhang X, Zhu Z, Zhu W, Wang Z, Wu H. p53 performs an essential role in mediating the oncogenic stimulus triggered by loss of expression of neurofibromatosis type 2 during in vitro tumor progression. Oncol Lett 2017; 14:2223-2231. [PMID: 28789444 PMCID: PMC5530008 DOI: 10.3892/ol.2017.6445] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Accepted: 03/10/2017] [Indexed: 02/04/2023] Open
Abstract
The loss of the tumor suppressor neurofibromatosis type 2 gene, encoding merlin, has been considered to be a fundamental event during the malignant progression of various cell types. However, a consensus for the mainstream mechanism, by which merlin deficiency contributes to uncontrolled cellular proliferation, has not been reached. The present study aimed to determine whether silencing of merlin using lentivirus-based short hairpin RNA potentiates cellular proliferation and cell cycle progression in human colon carcinoma HCT116 cell lines, expressing p53. The present results demonstrated that merlin knockdown contributed to cellular proliferation and G1/S cell cycle progression to a greater extent in HCT116 cells wide-type for p53 (p53wt) compared with p53-null (p53−/−) cells. This was supported by overexpression experiments which demonstrated a significant inhibitory effect of excess merlin on cellular proliferation only in HCT116 p53wt cells. In order to investigate the underlying mechanisms of action, the expression of p53-involved G1/S transition genes was evaluated by western blot analysis. For HCT116 p53wt cells, merlin loss suppressed p53 expression, and therefore the dysregulation of cell cycle regulatory proteins, including p21, cyclin D1/cyclin-dependent kinase (CDK)4 and cyclin E1/CDK2 complexes. However, merlin knockdowns had no impact on the expression of any of the aforementioned molecules in p53−/− cells, indicating that lack of merlin resulted in G1/S cell cycle progression, and thereby uncontrolled cellular proliferation mainly via the regulation of p53-mediated pathways. Taken together, it was proposed that p53 performs an essential role in mediating the oncogenic stimulus triggered by merlin loss, and p53 is a molecule that should be investigated for its potential in targeted drug therapy for merlin-deficient malignancies.
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Affiliation(s)
- Xiye Li
- Department of Otolaryngology Head and Neck Surgery, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200092, P.R. China.,Ear Institute, School of Medicine, Shanghai Jiao Tong University, Shanghai 200092, P.R. China.,Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai 200092, P.R. China
| | - Hongsai Chen
- Department of Otolaryngology Head and Neck Surgery, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200092, P.R. China.,Ear Institute, School of Medicine, Shanghai Jiao Tong University, Shanghai 200092, P.R. China.,Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai 200092, P.R. China
| | - Lu Xue
- Department of Otolaryngology Head and Neck Surgery, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200092, P.R. China.,Ear Institute, School of Medicine, Shanghai Jiao Tong University, Shanghai 200092, P.R. China.,Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai 200092, P.R. China
| | - Xiuhong Pang
- Department of Otolaryngology Head and Neck Surgery, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200092, P.R. China.,Ear Institute, School of Medicine, Shanghai Jiao Tong University, Shanghai 200092, P.R. China.,Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai 200092, P.R. China
| | - Xiaoman Zhang
- Department of Otolaryngology Head and Neck Surgery, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200092, P.R. China.,Ear Institute, School of Medicine, Shanghai Jiao Tong University, Shanghai 200092, P.R. China.,Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai 200092, P.R. China
| | - Zhengjie Zhu
- Department of Otolaryngology Head and Neck Surgery, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200092, P.R. China.,Ear Institute, School of Medicine, Shanghai Jiao Tong University, Shanghai 200092, P.R. China.,Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai 200092, P.R. China
| | - Weidong Zhu
- Department of Otolaryngology Head and Neck Surgery, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200092, P.R. China.,Ear Institute, School of Medicine, Shanghai Jiao Tong University, Shanghai 200092, P.R. China.,Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai 200092, P.R. China
| | - Zhaoyan Wang
- Department of Otolaryngology Head and Neck Surgery, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200092, P.R. China.,Ear Institute, School of Medicine, Shanghai Jiao Tong University, Shanghai 200092, P.R. China.,Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai 200092, P.R. China
| | - Hao Wu
- Department of Otolaryngology Head and Neck Surgery, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200092, P.R. China.,Ear Institute, School of Medicine, Shanghai Jiao Tong University, Shanghai 200092, P.R. China.,Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai 200092, P.R. China
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13
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Meerang M, Bérard K, Friess M, Bitanihirwe BKY, Soltermann A, Vrugt B, Felley-Bosco E, Bueno R, Richards WG, Seifert B, Stahel R, Weder W, Opitz I. Low Merlin expression and high Survivin labeling index are indicators for poor prognosis in patients with malignant pleural mesothelioma. Mol Oncol 2016; 10:1255-65. [PMID: 27378628 DOI: 10.1016/j.molonc.2016.06.005] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Revised: 06/17/2016] [Accepted: 06/20/2016] [Indexed: 11/25/2022] Open
Abstract
INTRODUCTION Alterations of the tumor suppressor Neurofibromatosis type II (NF2) have been reported in about 40% of Malignant pleural mesothelioma (MPM) patients. NF2 (Merlin) deficiency leads to alterations of the Hippo pathway; resulting in activation of the oncogenic Yes Associated Protein-1 (YAP1). Our aim was to investigate the association between these alterations and clinical outcomes. MATERIAL AND METHODS Tissue microarrays composed of MPM tumors derived from 2 independent MPM cohorts were employed for this study. Immunohistochemical expression of Merlin, YAP1 and its target genes, Survivin and connective tissue growth factor (CTGF) were assessed in nuclear and cytoplasmic fractions. Cohort 1 was comprised of 145 patients intended to be treated with chemotherapy (CTX) followed by extrapleural pneumonectomy (EPP), thus both pre- and post-CTX tissues were available. Cohort 2 was comprised of 59 patients treated with EPP followed by intraoperative hyperthermic cisplatin and/or adjuvant CTX and/or radiotherapy. Marker expression was quantified by means of labeling index (%) for nuclear Survivin and by H-score for the other markers. The dichotomized marker expression was tested for the association with overall survival (OS) and freedom from recurrence (FFR). RESULTS Kaplan-Meier survival curves revealed a significant association between low cytoplasmic Merlin expression in pre-induction CTX tissues of cohort 1 with shorter FFR (p = 0.02) and OS (p = 0.03). The same tendency was observed in the chemotherapy naïve tissues obtained during EPP of cohort 2. Low nuclear Merlin expression in post-CTX tissues (available from cohort 1 only) was associated with shorter FFR (p = 0.04) and OS (p = 0.05). High nuclear Survivin labeling indices in both pre- and post-CTX tissues of cohort 1 was associated with shorter FFR (p = 0.02). In cohort 2, this was associated with both FFR and OS (p = 0.046 and p = 0.002, respectively). In multivariate analysis, low expression of cytoplasmic Merlin remained an independent prognosticator for shorter FFR of cohort 1 [hazard ratio (HR) = 0.5, 95% confidence interval (CI) = 0.3-0.9, p = 0.001] and OS [HR = 0.5, 95% CI = 0.3-1, p = 0.04]. High Survivin labeling index was an independent prognostic factor for shorter FFR in patients from cohort 1 [HR = 3.4, 95% CI = 1.7-6.8, p = 0.006] and shorter OS in patients from cohort 2 [HR = 2.35, 95% CI = 1.27-4.33, p = 0.006]. CONCLUSIONS Our findings uncover the significance of Merlin protein expression and Survivin labeling index as prognosticators for poor clinical outcome in two independent MPM cohorts. If confirmed, these markers may be used to identify subgroups of patients benefitting from additional treatment.
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Affiliation(s)
- Mayura Meerang
- Division of Thoracic Surgery, University Hospital Zürich, Zürich 8091, Switzerland
| | - Karima Bérard
- Division of Thoracic Surgery, University Hospital Zürich, Zürich 8091, Switzerland
| | - Martina Friess
- Division of Thoracic Surgery, University Hospital Zürich, Zürich 8091, Switzerland
| | | | - Alex Soltermann
- Institute of Surgical Pathology, University Hospital Zürich, Zürich 8091, Switzerland
| | - Bart Vrugt
- Institute of Surgical Pathology, University Hospital Zürich, Zürich 8091, Switzerland
| | - Emanuela Felley-Bosco
- Laboratory of Molecular Oncology, University Hospital Zürich, Zürich 8091, Switzerland
| | - Raphael Bueno
- Thoracic Surgery, Harvard Medical School, Brigham and Women's Hospital, Boston, MA 02115, USA
| | - William G Richards
- Thoracic Surgery, Harvard Medical School, Brigham and Women's Hospital, Boston, MA 02115, USA
| | - Burkhardt Seifert
- Department of Biostatistics, Epidemiology, Biostatistics, and Prevention Institute (EBPI), University of Zürich, Zürich 8001, Switzerland
| | - Rolf Stahel
- Laboratory of Molecular Oncology, University Hospital Zürich, Zürich 8091, Switzerland
| | - Walter Weder
- Division of Thoracic Surgery, University Hospital Zürich, Zürich 8091, Switzerland
| | - Isabelle Opitz
- Division of Thoracic Surgery, University Hospital Zürich, Zürich 8091, Switzerland.
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14
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Vilmos P, Kristó I, Szikora S, Jankovics F, Lukácsovich T, Kari B, Erdélyi M. The actin-binding ERM protein Moesin directly regulates spindle assembly and function during mitosis. Cell Biol Int 2016; 40:696-707. [PMID: 27006187 DOI: 10.1002/cbin.10607] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Accepted: 03/19/2016] [Indexed: 12/21/2022]
Abstract
Ezrin-Radixin-Moesin proteins are highly conserved, actin-binding cytoskeletal proteins that play an essential role in microvilli formation, T-cell activation, and tumor metastasis by linking actin filaments to the plasma membrane. Recent studies demonstrated that the only Ezrin-Radixin-Moesin protein of Drosophila melanogaster, Moesin, is involved in mitotic spindle function through stabilizing cell shape and microtubules at the cell cortex. We previously observed that Moesin localizes to the mitotic spindle; hence, we tested for the biological significance of this surprising localization and investigated whether it plays a direct role in spindle function. To separate the cortical and spindle functions of Moesin during mitosis we combined cell biological and genetic methods. We used early Drosophila embryos, in which mitosis occurs in the absence of a cell cortex, and found in vivo evidence for the direct requirement of Moesin in mitotic spindle assembly and function. We also found that the accumulation of Moesin precedes the construction of the microtubule spindle, and the fusiform structure formed by Moesin persists even after the microtubules have disassembled.
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Affiliation(s)
- Péter Vilmos
- Biological Research Center of the Hungarian Academy of Sciences, 6726 Szeged, Temesvári krt. 62., Hungary
| | - Ildikó Kristó
- Biological Research Center of the Hungarian Academy of Sciences, 6726 Szeged, Temesvári krt. 62., Hungary
| | - Szilárd Szikora
- Biological Research Center of the Hungarian Academy of Sciences, 6726 Szeged, Temesvári krt. 62., Hungary
| | - Ferenc Jankovics
- Biological Research Center of the Hungarian Academy of Sciences, 6726 Szeged, Temesvári krt. 62., Hungary
| | - Tamás Lukácsovich
- Department of Developmental and Cell Biology, University of California Irvine, Irvine, CA, 92697, USA
| | - Beáta Kari
- Biological Research Center of the Hungarian Academy of Sciences, 6726 Szeged, Temesvári krt. 62., Hungary
| | - Miklós Erdélyi
- Biological Research Center of the Hungarian Academy of Sciences, 6726 Szeged, Temesvári krt. 62., Hungary
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15
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Hikasa H, Sekido Y, Suzuki A. Merlin/NF2-Lin28B-let-7 Is a Tumor-Suppressive Pathway that Is Cell-Density Dependent and Hippo Independent. Cell Rep 2016; 14:2950-61. [PMID: 26997273 DOI: 10.1016/j.celrep.2016.02.075] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Revised: 12/20/2015] [Accepted: 02/18/2016] [Indexed: 01/24/2023] Open
Abstract
Contact inhibition of proliferation is critical for tissue organization, and its dysregulation contributes to tumorigenesis. Merlin/NF2 is a tumor suppressor that governs contact inhibition. Although Merlin/NF2 inhibits YAP1 and TAZ, which are paralogous Hippo pathway transcriptional co-activators and oncoproteins, it is not fully understood how Merlin/NF2-mediated signal transduction triggered by cell-cell contact exerts tumor suppression. Here, we identify Lin28B, an inhibitor of let-7 microRNAs (miRNAs), as an important downstream target of Merlin/NF2. Functional studies revealed that, at low cell density, Merlin/NF2 is phosphorylated and does not bind to Lin28B, allowing Lin28B to enter the nucleus, bind to pri-let-7 miRNAs, and inhibit their maturation in a YAP1/TAZ-independent manner. This inhibition of pri-let-7 maturation then promotes cell growth. However, cell-cell contact triggers Merlin/NF2 dephosphorylation, which sequesters Lin28B in the cytoplasm and permits pri-let-7 maturation. Our results reveal that Merlin/NF2-mediated signaling drives a tumor-suppressive pathway that is cell-density dependent and Hippo independent.
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Affiliation(s)
- Hiroki Hikasa
- Division of Cancer Genetics, Medical Institute of Bioregulation, Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan
| | - Yoshitaka Sekido
- Division of Molecular Oncology, Aichi Cancer Center Research Institute, Nagoya 464-8681, Japan
| | - Akira Suzuki
- Division of Cancer Genetics, Medical Institute of Bioregulation, Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan.
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16
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Koliou X, Fedonidis C, Kalpachidou T, Mangoura D. Nuclear import mechanism of neurofibromin for localization on the spindle and function in chromosome congression. J Neurochem 2015; 136:78-91. [PMID: 26490262 DOI: 10.1111/jnc.13401] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2015] [Revised: 10/12/2015] [Accepted: 10/15/2015] [Indexed: 12/28/2022]
Abstract
Neurofibromatosis type-1 (NF-1) is caused by mutations in the tumor suppressor gene NF1; its protein product neurofibromin is a RasGTPase-activating protein, a property that has yet to explain aneuploidy, most often observed in astrocytes in NF-1. Here, we provide a mechanistic model for the regulated nuclear import of neurofibromin during the cell cycle and for a role in chromosome congression. Specifically, we demonstrate that neurofibromin, phosphorylated on Ser2808, a residue adjacent to a nuclear localization signal in the C-terminal domain (CTD), by Protein Kinase C-epsilon (PKC-ε), accumulates in a Ran-dependent manner and through binding to lamin in the nucleus at G2 in glioblastoma cells. Furthermore, we identify CTD as a tubulin-binding domain and show that a phosphomimetic substitution of its Ser2808 results in a predominantly nuclear localization. Confocal analysis shows that endogenous neurofibromin localizes on the centrosomes at interphase, as well as on the mitotic spindle, through direct associations with tubulins, in glioblastoma cells and primary astrocytes. More importantly, analysis of mitotic phenotypes after siRNA-mediated depletion shows that acute loss of this tumor suppressor protein leads to aberrant chromosome congression at the metaphase plate. Therefore, neurofibromin protein abundance and nuclear import are mechanistically linked to an error-free chromosome congression. Concerned with neurofibromin's, a tumor suppressor, mechanism of action, we demonstrate in astrocytic cells that its synthesis, phosphorylation by Protein Kinase C-ε on Ser2808 (a residue adjacent to a nuclear localization sequence), and nuclear import are cell cycle-dependent, being maximal at G2. During mitosis, neurofibromin is an integral part of the spindle, while its depletion leads to aberrant chromosome congression, possibly explaining the development of chromosomal instability in Neurofibromatosis type-1. Read the Editorial Highlight for this article on page 11. Cover Image for this issue: doi: 10.1111/jnc.13300.
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Affiliation(s)
- Xeni Koliou
- Basic Research Center, Biomedical Research Foundation of the Academy of Athens, Athens, Greece
| | - Constantinos Fedonidis
- Basic Research Center, Biomedical Research Foundation of the Academy of Athens, Athens, Greece
| | - Theodora Kalpachidou
- Basic Research Center, Biomedical Research Foundation of the Academy of Athens, Athens, Greece
| | - Dimitra Mangoura
- Basic Research Center, Biomedical Research Foundation of the Academy of Athens, Athens, Greece
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17
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Abstract
Cell division relies on coordinated regulation of the cell cycle. A process including a well-defined series of strictly regulated molecular mechanisms involving cyclin-dependent kinases, retinoblastoma protein, and polo-like kinases. Dysfunctions in cell cycle regulation are associated with disease such as cancer, diabetes, and neurodegeneration. Compartmentalization of cellular signaling is a common strategy used to ensure the accuracy and efficiency of cellular responses. Compartmentalization of intracellular signaling is maintained by scaffolding proteins, such as A-kinase anchoring proteins (AKAPs). AKAPs are characterized by their ability to anchor the regulatory subunits of protein kinase A (PKA), and thereby achieve guidance to different cellular locations via various targeting domains. Next to PKA, AKAPs also associate with several other signaling elements including receptors, ion channels, protein kinases, phosphatases, small GTPases, and phosphodiesterases. Taking the amount of possible AKAP signaling complexes and their diverse localization into account, it is rational to believe that such AKAP-based complexes regulate several critical cellular events of the cell cycle. In fact, several AKAPs are assigned as tumor suppressors due to their vital roles in cell cycle regulation. Here, we first briefly discuss the most important players of cell cycle progression. After that, we will review our recent knowledge of AKAPs linked to the regulation and progression of the cell cycle, with special focus on AKAP12, AKAP8, and Ezrin. At last, we will discuss this specific AKAP subset in relation to diseases with focus on a diverse subset of cancer.
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Affiliation(s)
- B Han
- Department of Molecular Pharmacology, University of Groningen, Groningen, The Netherlands. .,Groningen Research Institute for Asthma and COPD, GRIAC, Groningen, The Netherlands.
| | - W J Poppinga
- Department of Molecular Pharmacology, University of Groningen, Groningen, The Netherlands.,Groningen Research Institute for Asthma and COPD, GRIAC, Groningen, The Netherlands
| | - M Schmidt
- Department of Molecular Pharmacology, University of Groningen, Groningen, The Netherlands.,Groningen Research Institute for Asthma and COPD, GRIAC, Groningen, The Netherlands
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18
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Guerrero PA, Yin W, Camacho L, Marchetti D. Oncogenic role of Merlin/NF2 in glioblastoma. Oncogene 2015; 34:2621-30. [PMID: 25043298 PMCID: PMC4302072 DOI: 10.1038/onc.2014.185] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Revised: 04/23/2014] [Accepted: 05/16/2014] [Indexed: 02/07/2023]
Abstract
Glioblastoma is the most common and aggressive primary brain tumor in adults, with a poor prognosis because of its resistance to radiotherapy and chemotherapy. Merlin/NF2 (moesin-ezrin-radixin-like protein/neurofibromatosis type 2) is a tumor suppressor found to be mutated in most nervous system tumors; however, it is not mutated in glioblastomas. Merlin associates with several transmembrane receptors and intracellular proteins serving as an anchoring molecule. Additionally, it acts as a key component of cell motility. By selecting sub-populations of U251 glioblastoma cells, we observed that high expression of phosphorylated Merlin at serine 518 (S518-Merlin), NOTCH1 and epidermal growth factor receptor (EGFR) correlated with increased cell proliferation and tumorigenesis. These cells were defective in cell-contact inhibition with changes in Merlin phosphorylation directly affecting NOTCH1 and EGFR expression, as well as downstream targets HES1 (hairy and enhancer of split-1) and CCND1 (cyclin D1). Of note, we identified a function for S518-Merlin, which is distinct from what has been reported when the expression of Merlin is diminished in relation to EGFR and NOTCH1 expression, providing first-time evidence that demonstrates that the phosphorylation of S518-Merlin in glioblastoma promotes oncogenic properties that are not only the result of inactivation of the tumor suppressor role of Merlin but also an independent process implicating a Merlin-driven regulation of NOTCH1 and EGFR.
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Affiliation(s)
- Paola A. Guerrero
- Department of Pathology & Immunology, Baylor College of Medicine, One Baylor Plaza, Houston, TX, 77030
| | - Wei Yin
- Department of Pathology & Immunology, Baylor College of Medicine, One Baylor Plaza, Houston, TX, 77030
| | - Laura Camacho
- Department of Pathology & Immunology, Baylor College of Medicine, One Baylor Plaza, Houston, TX, 77030
| | - Dario Marchetti
- Department of Pathology & Immunology, Baylor College of Medicine, One Baylor Plaza, Houston, TX, 77030
- Department of Molecular & Cellular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX, 77030
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19
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Turner JG, Dawson J, Cubitt CL, Baz R, Sullivan DM. Inhibition of CRM1-dependent nuclear export sensitizes malignant cells to cytotoxic and targeted agents. Semin Cancer Biol 2014; 27:62-73. [PMID: 24631834 PMCID: PMC4108511 DOI: 10.1016/j.semcancer.2014.03.001] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2014] [Revised: 02/25/2014] [Accepted: 03/01/2014] [Indexed: 10/25/2022]
Abstract
Nuclear-cytoplasmic trafficking of proteins is a significant factor in the development of cancer and drug resistance. Subcellular localization of exported proteins linked to cancer development include those involved in cell growth and proliferation, apoptosis, cell cycle regulation, transformation, angiogenesis, cell adhesion, invasion, and metastasis. Here, we examined the basic mechanisms involved in the export of proteins from the nucleus to the cytoplasm. All proteins over 40kDa use the nuclear pore complex to gain entry or exit from the nucleus, with the primary nuclear export molecule involved in these processes being chromosome region maintenance 1 (CRM1, exportin 1 or XPO1). Proteins exported from the nucleus must possess a hydrophobic nuclear export signal (NES) peptide that binds to a hydrophobic groove containing an active-site Cys528 in the CRM1 protein. CRM1 inhibitors function largely by covalent modification of the active site Cys528 and prevent binding to the cargo protein NES. In the absence of a CRM1 inhibitor, CRM1 binds cooperatively to the NES of the cargo protein and RanGTP, forming a trimer that is actively transported out of the nucleus by facilitated diffusion. Nuclear export can be blocked by CRM1 inhibitors, NES peptide inhibitors or by preventing post-translational modification of cargo proteins. Clinical trials using the classic CRM1 inhibitor leptomycin B proved too toxic for patients; however, a new generation of less toxic small molecule inhibitors is being used in clinical trials in patients with both hematological malignancies and solid tumors. Additional trials are being initiated using small-molecule CRM1 inhibitors in combination with chemotherapeutics such as pegylated liposomal doxorubicin. In this review, we present evidence that combining the new CRM1 inhibitors with other classes of therapeutics may prove effective in the treatment of cancer. Potential combinatorial therapies discussed include the use of CRM1 inhibitors and the addition of alkylating agents (melphalan), anthracyclines (doxorubicin and daunomycin), BRAF inhibitors, platinum drugs (cisplatin and oxaliplatin), proteosome inhibitors (bortezomib and carfilzomib), or tyrosine-kinase inhibitors (imatinib). Also, the sequence of treatment may be important for combination therapy. We found that the most effective treatment regimen involved first priming the cancer cells with the CRM1 inhibitor followed by doxorubicin, bortezomib, carfilzomib, or melphalan. This order sensitized both de novo and acquired drug-resistant cancer cell lines.
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Affiliation(s)
- Joel G Turner
- Department of Blood and Marrow Transplantation and Chemical Biology and Molecular Medicine Program, H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL 33612, USA
| | - Jana Dawson
- Department of Blood and Marrow Transplantation and Chemical Biology and Molecular Medicine Program, H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL 33612, USA
| | - Christopher L Cubitt
- Translational Research Core Laboratory, H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL 33612, USA
| | - Rachid Baz
- Department of Malignant Hematology, H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL 33612, USA
| | - Daniel M Sullivan
- Department of Blood and Marrow Transplantation and Chemical Biology and Molecular Medicine Program, H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL 33612, USA.
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20
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Schulz A, Zoch A, Morrison H. A neuronal function of the tumor suppressor protein merlin. Acta Neuropathol Commun 2014; 2:82. [PMID: 25012216 PMCID: PMC4149232 DOI: 10.1186/s40478-014-0082-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Accepted: 06/30/2014] [Indexed: 02/07/2023] Open
Abstract
Mutagenic loss of the NF2 tumor suppressor gene encoded protein merlin is known to provoke the hereditary neoplasia syndrome, Neurofibromatosis type 2 (NF2). In addition to glial cell-derived tumors in the PNS and CNS, disease-related lesions also affect the skin and the eyes. Furthermore, 60% of NF2 patients suffer from peripheral nerve damage, clinically referred to as peripheral neuropathy. Strikingly, NF2-associated neuropathy often occurs in the absence of nerve damaging tumors, suggesting tumor-independent events. Recent findings indicate an important role of merlin in neuronal cell types concerning neuromorphogenesis, axon structure maintenance and communication between axons and Schwann cells. In this review, we compile clinical and experimental evidences for the underestimated role of the tumor suppressor merlin in the neuronal compartment.
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21
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Molecular insights into NF2/Merlin tumor suppressor function. FEBS Lett 2014; 588:2743-52. [PMID: 24726726 DOI: 10.1016/j.febslet.2014.04.001] [Citation(s) in RCA: 128] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Revised: 04/01/2014] [Accepted: 04/02/2014] [Indexed: 02/07/2023]
Abstract
The FERM domain protein Merlin, encoded by the NF2 tumor suppressor gene, regulates cell proliferation in response to adhesive signaling. The growth inhibitory function of Merlin is induced by intercellular adhesion and inactivated by joint integrin/receptor tyrosine kinase signaling. Merlin contributes to the formation of cell junctions in polarized tissues, activates anti-mitogenic signaling at tight-junctions, and inhibits oncogenic gene expression. Thus, inactivation of Merlin causes uncontrolled mitogenic signaling and tumorigenesis. Merlin's predominant tumor suppressive functions are attributable to its control of oncogenic gene expression through regulation of Hippo signaling. Notably, Merlin translocates to the nucleus where it directly inhibits the CRL4(DCAF1) E3 ubiquitin ligase, thereby suppressing inhibition of the Lats kinases. A dichotomy in NF2 function has emerged whereby Merlin acts at the cell cortex to organize cell junctions and propagate anti-mitogenic signaling, whereas it inhibits oncogenic gene expression through the inhibition of CRL4(DCAF1) and activation of Hippo signaling. The biochemical events underlying Merlin's normal function and tumor suppressive activity will be discussed in this Review, with emphasis on recent discoveries that have greatly influenced our understanding of Merlin biology.
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22
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Hilton DA, Hanemann CO. Schwannomas and their pathogenesis. Brain Pathol 2014; 24:205-20. [PMID: 24450866 DOI: 10.1111/bpa.12125] [Citation(s) in RCA: 110] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Accepted: 01/16/2014] [Indexed: 12/18/2022] Open
Abstract
Schwannomas may occur spontaneously, or in the context of a familial tumor syndrome such as neurofibromatosis type 2 (NF2), schwannomatosis and Carney's complex. Schwannomas have a variety of morphological appearances, but they behave as World Health Organization (WHO) grade I tumors, and only very rarely undergo malignant transformation. Central to the pathogenesis of these tumors is loss of function of merlin, either by direct genetic change involving the NF2 gene on chromosome 22 or secondarily to merlin inactivation. The genetic pathways and morphological features of schwannomas associated with different genetic syndromes will be discussed. Merlin has multiple functions, including within the nucleus and at the cell membrane, and this review summarizes our current understanding of the mechanisms by which merlin loss is involved in schwannoma pathogenesis, highlighting potential areas for therapeutic intervention.
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Affiliation(s)
- David A Hilton
- Department of Cellular and Anatomical Pathology, Derriford Hospital, Plymouth, UK
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23
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Qi Q, Liu X, Brat DJ, Ye K. Merlin sumoylation is required for its tumor suppressor activity. Oncogene 2013; 33:4893-903. [PMID: 24166499 DOI: 10.1038/onc.2013.438] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Revised: 08/01/2013] [Accepted: 08/12/2013] [Indexed: 12/11/2022]
Abstract
Merlin, encoded by the Neurofibromatosis 2 (NF2) gene, is a multifunctional tumor suppressor that integrates and regulates extracellular cues and intracellular signaling pathways, both at the plasma membrane and in the nucleus, to control cell proliferation, migration and invasion. Molecular mechanisms regulating merlin's tumor-suppressive activity have not been clearly defined. Here we report that merlin can be sumoylated on Lysine residue (K76) in vitro and in vivo. Sumoylation mediates merlin's intramolecular and intermolecular binding activities and regulates its cytoplasm/nucleus trafficking. Interestingly, sumoylation of merlin is regulated by its phosphorylation via Akt and PAK2 kinases. Mutation of K76 into arginine (R) abolishes its sumoylation, disrupts merlin cortical cytoskeleton residency and attenuates its stability. Using a K76R mutant merlin in a subcutaneous U87MG xenograft model, we demonstrate that merlin sumoylation is required for tumor-suppressive activity. Taken together, our findings indicate that merlin is sumoylated and that this post-translational modification is essential for tumor suppression.
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Affiliation(s)
- Q Qi
- Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, GA, USA
| | - X Liu
- Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, GA, USA
| | - D J Brat
- Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, GA, USA
| | - K Ye
- Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, GA, USA
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24
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Neurofibromatosis type 2 tumor suppressor protein, NF2, induces proteasome-mediated degradation of JC virus T-antigen in human glioblastoma. PLoS One 2013; 8:e53447. [PMID: 23308224 PMCID: PMC3538535 DOI: 10.1371/journal.pone.0053447] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2012] [Accepted: 11/28/2012] [Indexed: 12/02/2022] Open
Abstract
Neurofibromatosis type 2 protein (NF2) has been shown to act as tumor suppressor primarily through its functions as a cytoskeletal scaffold. However, NF2 can also be found in the nucleus, where its role is less clear. Previously, our group has identified JC virus (JCV) tumor antigen (T-antigen) as a nuclear binding partner for NF2 in tumors derived from JCV T-antigen transgenic mice. The association of NF2 with T-antigen in neuronal origin tumors suggests a potential role for NF2 in regulating the expression of the JCV T-antigen. Here, we report that NF2 suppresses T-antigen protein expression in U-87 MG human glioblastoma cells, which subsequently reduces T-antigen-mediated regulation of the JCV promoter. When T-antigen mRNA was quantified, it was determined that increasing expression of NF2 correlated with an accumulation of T-antigen mRNA; however, a decrease in T-antigen at the protein level was observed. NF2 was found to promote degradation of ubiquitin bound T-antigen protein via a proteasome dependent pathway concomitant with the accumulation of the JCV early mRNA encoding T-antigen. The interaction between T-antigen and NF2 maps to the FERM domain of NF2, which has been shown previously to be responsible for its tumor suppressor activity. Co-immunoprecipitation assays revealed a ternary complex among NF2, T-antigen, and the tumor suppressor protein, p53 within a glioblastoma cell line. Further, these proteins were detected in various degrees in patient tumor tissue, suggesting that these associations may occur in vivo. Collectively, these results demonstrate that NF2 negatively regulates JCV T-antigen expression by proteasome-mediated degradation, and suggest a novel role for NF2 as a suppressor of JCV T-antigen-induced cell cycle regulation.
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Laulajainen M, Melikova M, Muranen T, Carpén O, Grönholm M. Distinct overlapping sequences at the carboxy-terminus of merlin regulate its tumour suppressor and morphogenic activity. J Cell Mol Med 2013; 16:2161-75. [PMID: 22325036 PMCID: PMC3822986 DOI: 10.1111/j.1582-4934.2012.01525.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The Neurofibromatosis 2 (NF2) gene product merlin is a tumour suppressor, which in addition to inhibiting cell proliferation regulates cell morphology. The morphogenic properties of merlin may play a role in tumour suppression, as patient-derived tumour cells demonstrate cytoskeletal abnormalities. However, it is still unclear how these functions are linked. The N-terminal FERM-domain of merlin is highly homologous to the oncogenic protein ezrin, while the C-termini are less conserved, suggesting that the opposite effect of the proteins on proliferation could be mediated by their distinct C-terminal regions. In this study we characterize the role of the most C-terminal residues of merlin in the regulation of proliferation, cytoskeletal organization, phosphorylation and intramolecular associations. In addition to the two full-length merlin isoforms and truncating mutations found in patients, we focused on the evolutionally conserved C-terminal residues 545-547, also harbouring disease-causing mutations. We demonstrate that merlin induces cell extensions, which result from impaired retraction of protrusions rather than from increased formation of filopodia. The residues 538-568 were found particularly important for this morphogenic activity. The results further show that both merlin isoforms are able to equally inhibit proliferation, whereas C-terminal mutants affecting residues 545-547 are less effective in growth suppression. This study demonstrates that the C-terminus contains distinct but overlapping functional domains important for regulation of the morphogenic activity, intramolecular associations and cell proliferation.
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Affiliation(s)
- Minja Laulajainen
- Biomedicum Helsinki, Department of Pathology, University of Helsinki, Helsinki, Finland.
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Li W, Cooper J, Karajannis MA, Giancotti FG. Merlin: a tumour suppressor with functions at the cell cortex and in the nucleus. EMBO Rep 2012; 13:204-15. [PMID: 22482125 DOI: 10.1038/embor.2012.11] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Inhibition of proliferation by cell-to-cell contact is essential for tissue organization, and its disruption contributes to tumorigenesis. The FERM domain protein Merlin, encoded by the NF2 tumour suppressor gene, is an important mediator of contact inhibition. Merlin was thought to inhibit mitogenic signalling and activate the Hippo pathway by interacting with diverse target-effectors at or near the plasma membrane. However, recent studies highlight that Merlin pleiotropically affects signalling by migrating into the nucleus and inducing a growth-suppressive programme of gene expression through its direct inhibition of the CRL4DCAF1 E3 ubiquitin ligase. In addition, Merlin promotes the establishment of epithelial adhesion and polarity by recruiting Par3 and aPKC to E-cadherin-dependent junctions, and by ensuring the assembly of tight junctions. These recent advances suggest that Merlin acts at the cell cortex and in the nucleus in a similar, albeit antithetic, manner to the oncogene β-catenin.
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Affiliation(s)
- Wei Li
- Cell Biology Program, Sloan–Kettering Institute for Cancer Research, Memorial Sloan–Kettering Cancer Center, 1275 York Avenue, Box 216, New York, New York 10065, USA
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Boratkó A, Gergely P, Csortos C. Cell cycle dependent association of EBP50 with protein phosphatase 2A in endothelial cells. PLoS One 2012; 7:e35595. [PMID: 22523604 PMCID: PMC3327649 DOI: 10.1371/journal.pone.0035595] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2011] [Accepted: 03/19/2012] [Indexed: 12/19/2022] Open
Abstract
Ezrin-radixin-moesin (ERM)-binding phosphoprotein 50 (EBP50) is a phosphorylatable PDZ domain-containing adaptor protein that is abundantly expressed in epithelium but was not yet studied in the endothelium. We report unusual nuclear localization of EBP50 in bovine pulmonary artery endothelial cells (BPAEC). Immunofluorescent staining and cellular fractionation demonstrated that EBP50 is present in the nuclear and perinuclear region in interphase cells. In the prophase of mitosis EBP50 redistributes to the cytoplasmic region in a phosphorylation dependent manner and during mitosis EBP50 co-localizes with protein phosphatase 2A (PP2A). Furthermore, in vitro wound healing of BPAEC expressing phospho-mimic mutant of EBP50 was accelerated indicating that EBP50 is involved in the regulation of the cell division. Cell cycle dependent specific interactions were detected between EBP50 and the subunits of PP2A (A, C, and Bα) with immunoprecipitation and pull-down experiments. The interaction of EBP50 with the Bα containing form of PP2A suggests that this holoenzyme of PP2A can be responsible for the dephosphorylation of EBP50 in cytokinesis. Moreover, the results underline the significance of EBP50 in cell division via reversible phosphorylation of the protein with cyclin dependent kinase and PP2A in normal cells.
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Affiliation(s)
- Anita Boratkó
- Department of Medical Chemistry, University of Debrecen Medical and Health Science Center, Debrecen, Hungary
| | - Pál Gergely
- Department of Medical Chemistry, University of Debrecen Medical and Health Science Center, Debrecen, Hungary
- Cell Biology and Signaling Research Group of the Hungarian Academy of Sciences, University of Debrecen Medical and Health Science Center, Debrecen, Hungary
| | - Csilla Csortos
- Department of Medical Chemistry, University of Debrecen Medical and Health Science Center, Debrecen, Hungary
- * E-mail:
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Turner JG, Dawson J, Sullivan DM. Nuclear export of proteins and drug resistance in cancer. Biochem Pharmacol 2012; 83:1021-32. [PMID: 22209898 PMCID: PMC4521586 DOI: 10.1016/j.bcp.2011.12.016] [Citation(s) in RCA: 281] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2011] [Revised: 12/09/2011] [Accepted: 12/12/2011] [Indexed: 12/14/2022]
Abstract
The intracellular location of a protein is crucial to its normal functioning in a cell. Cancer cells utilize the normal processes of nuclear-cytoplasmic transport through the nuclear pore complex of a cell to effectively evade anti-neoplastic mechanisms. CRM1-mediated export is increased in various cancers. Proteins that are exported in cancer include tumor-suppressive proteins such as retinoblastoma, APC, p53, BRAC1, FOXO proteins, INI1/hSNF5, galectin-3, Bok, nucleophosmin, RASSF2, Merlin, p21(CIP), p27(KIP1), N-WASP/FAK, estradiol receptor and Tob, drug targets topoisomerase I and IIα and BCR-ABL, and the molecular chaperone protein Hsp90. Here, we review in detail the current processes and known structures involved in the export of a protein through the nuclear pore complex. We also discuss the export receptor molecule CRM1 and its binding to the leucine-rich nuclear export signal of the cargo protein and the formation of a nuclear export trimer with RanGTP. The therapeutic potential of various CRM1 inhibitors will be addressed, including leptomycin B, ratjadone, KOS-2464, and specific small molecule inhibitors of CRM1, N-azolylacrylate analogs, FOXO export inhibitors, valtrate, acetoxychavicol acetate, CBS9106, and SINE inhibitors. We will also discuss examples of how drug resistance may be reversed by targeting the exported proteins topoisomerase IIα, BCR-ABL, and galectin-3. As effective and less toxic CRM1 export inhibitors become available, they may be used as both single agents and in combination with current chemotherapeutic drugs. We believe that the future development of low-toxicity, small-molecule CRM1 inhibitors may provide a new approach to treating cancer.
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Affiliation(s)
- Joel G. Turner
- Blood and Marrow Transplant Department and Experimental Therapeutics Program, H. Lee Moffitt Cancer Center and Research Institute, 12902 Magnolia Drive, Tampa, FL 33612, USA
| | - Jana Dawson
- Blood and Marrow Transplant Department and Experimental Therapeutics Program, H. Lee Moffitt Cancer Center and Research Institute, 12902 Magnolia Drive, Tampa, FL 33612, USA
| | - Daniel M. Sullivan
- Blood and Marrow Transplant Department and Experimental Therapeutics Program, H. Lee Moffitt Cancer Center and Research Institute, 12902 Magnolia Drive, Tampa, FL 33612, USA
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Molecular Pathogenesis of Vestibular Schwannomas: Insights for the Development of Novel Medical Therapies. Otolaryngol Pol 2012; 66:84-95. [DOI: 10.1016/s0030-6657(12)70754-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2012] [Accepted: 02/13/2012] [Indexed: 11/21/2022]
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Lacroix B, Maddox AS. Cytokinesis, ploidy and aneuploidy. J Pathol 2011; 226:338-51. [DOI: 10.1002/path.3013] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2011] [Revised: 09/22/2011] [Accepted: 09/24/2011] [Indexed: 12/21/2022]
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Abstract
Focal adhesion kinase (FAK) is a scaffold and tyrosine kinase protein that binds to itself and cellular partners through its four-point-one, ezrin, radixin, moesin (FERM) domain. Recent structural work reveals that regulatory protein partners convert auto-inhibited FAK into its active state by binding to its FERM domain. Further, the identity of FAK FERM domain-interacting proteins yields clues as to how FAK coordinates diverse cellular responses, including cell adhesion, polarization, migration, survival and death, and suggests that FERM domains might mediate information transfer between the cell cortex and nucleus. Importantly, the FAK FERM domain might act as a paradigm for the actions of other FERM domain-containing proteins.
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Li W, You L, Cooper J, Schiavon G, Pepe-Caprio A, Zhou L, Ishii R, Giovannini M, Hanemann CO, Long SB, Erdjument-Bromage H, Zhou P, Tempst P, Giancotti FG. Merlin/NF2 suppresses tumorigenesis by inhibiting the E3 ubiquitin ligase CRL4(DCAF1) in the nucleus. Cell 2010; 140:477-90. [PMID: 20178741 DOI: 10.1016/j.cell.2010.01.029] [Citation(s) in RCA: 252] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2009] [Revised: 08/07/2009] [Accepted: 01/16/2010] [Indexed: 11/29/2022]
Abstract
Current models imply that the FERM domain protein Merlin, encoded by the tumor suppressor NF2, inhibits mitogenic signaling at or near the plasma membrane. Here, we show that the closed, growth-inhibitory form of Merlin accumulates in the nucleus, binds to the E3 ubiquitin ligase CRL4(DCAF1), and suppresses its activity. Depletion of DCAF1 blocks the promitogenic effect of inactivation of Merlin. Conversely, enforced expression of a Merlin-insensitive mutant of DCAF1 counteracts the antimitogenic effect of Merlin. Re-expression of Merlin and silencing of DCAF1 implement a similar, tumor-suppressive program of gene expression. Tumor-derived mutations invariably disrupt Merlin's ability to interact with or inhibit CRL4(DCAF1). Finally, depletion of DCAF1 inhibits the hyperproliferation of Schwannoma cells from NF2 patients and suppresses the oncogenic potential of Merlin-deficient tumor cell lines. We propose that Merlin suppresses tumorigenesis by translocating to the nucleus to inhibit CRL4(DCAF1).
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Affiliation(s)
- Wei Li
- Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA
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Moore CJ, Winder SJ. Dystroglycan versatility in cell adhesion: a tale of multiple motifs. Cell Commun Signal 2010; 8:3. [PMID: 20163697 PMCID: PMC2834674 DOI: 10.1186/1478-811x-8-3] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2009] [Accepted: 02/17/2010] [Indexed: 12/02/2022] Open
Abstract
Dystroglycan is a ubiquitously expressed heterodimeric adhesion receptor. The extracellular α-subunit makes connections with a number of laminin G domain ligands including laminins, agrin and perlecan in the extracellular matrix and the transmembrane β-subunit makes connections to the actin filament network via cytoskeletal linkers including dystrophin, utrophin, ezrin and plectin, depending on context. Originally discovered as part of the dystrophin glycoprotein complex of skeletal muscle, dystroglycan is an important adhesion molecule and signalling scaffold in a multitude of cell types and tissues and is involved in several diseases. Dystroglycan has emerged as a multifunctional adhesion platform with many interacting partners associating with its short unstructured cytoplasmic domain. Two particular hotspots are the cytoplasmic juxtamembrane region and at the very carboxy terminus of dystroglycan. Regions which between them have several overlapping functions: in the juxtamembrane region; a nuclear localisation signal, ezrin/radixin/moesin protein, rapsyn and ERK MAP Kinase binding function, and at the C terminus a regulatory tyrosine governing WW, SH2 and SH3 domain interactions. We will discuss the binding partners for these motifs and how their interactions and regulation can modulate the involvement of dystroglycan in a range of different adhesion structures and functions depending on context. Thus dystroglycan presents as a multifunctional scaffold involved in adhesion and adhesion-mediated signalling with its functions under exquisite spatio-temporal regulation.
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Affiliation(s)
- Chris J Moore
- Department of Biomedical Science, University of Sheffield, Firth Court, Western Bank, Sheffield, S10 2TN, UK.
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Lü J, Zou J, Wu H, Cai L. Compensative Shuttling of Merlin to Phosphorylation on Serine 518 in Vestibular Schwannoma. Laryngoscope 2008; 118:169-74. [DOI: 10.1097/mlg.0b013e3181566594] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Svensson P, Williams C, Lundeberg J, Rydén P, Bergqvist I, Edlund H. Gene array identification of Ipf1/Pdx1-/- regulated genes in pancreatic progenitor cells. BMC DEVELOPMENTAL BIOLOGY 2007; 7:129. [PMID: 18036209 PMCID: PMC2212654 DOI: 10.1186/1471-213x-7-129] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/15/2007] [Accepted: 11/23/2007] [Indexed: 01/29/2023]
Abstract
Background The homeodomain transcription factor IPF1/PDX1 exerts a dual role in the pancreas; Ipf1/Pdx1 global null mutants fail to develop a pancreas whereas conditional inactivation of Ipf1/Pdx1 in β-cells leads to impaired β-cell function and diabetes. Although several putative target genes have been linked to the β-cell function of Ipf1/Pdx1, relatively little is known with respect to genes regulated by IPF1/PDX1 in early pancreatic progenitor cells. Results Microarray analyses identified a total of 111 genes that were differentially expressed in e10.5 pancreatic buds of Ipf1/Pdx1-/- embryos. The expression of one of these, Spondin 1, which encodes an extracellular matrix protein, has not previously been described in the pancreas. Quantitative real-time RT-PCR analyses and immunohistochemical analyses also revealed that the expression of FgfR2IIIb, that encodes the receptor for FGF10, was down-regulated in Ipf1/Pdx1-/- pancreatic progenitor cells. Conclusion This microarray analysis has identified a number of candidate genes that are differentially expressed in Ipf1/Pdx1-/- pancreatic buds. Several of the differentially expressed genes were known to be important for pancreatic progenitor cell proliferation and differentiation whereas others have not previously been associated with pancreatic development.
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Affiliation(s)
- Per Svensson
- Umeå Center for Molecular Medicine, Umeå University, SE-901 87 Umeå, Sweden.
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Scoles DR. The merlin interacting proteins reveal multiple targets for NF2 therapy. Biochim Biophys Acta Rev Cancer 2007; 1785:32-54. [PMID: 17980164 DOI: 10.1016/j.bbcan.2007.10.001] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2007] [Revised: 09/29/2007] [Accepted: 10/03/2007] [Indexed: 01/20/2023]
Abstract
The neurofibromatosis 2 (NF2) tumor suppressor protein merlin is commonly mutated in human benign brain tumors. The gene altered in NF2 was located on human chromosome 22q12 in 1993 and the encoded protein named merlin and schwannomin. Merlin has homology to ERM family proteins, ezrin, radixin, and moesin, within the protein 4.1 superfamily. In efforts to determine merlin function several groups have discovered 34 merlin interacting proteins, including ezrin, radixin, moesin, CD44, layilin, paxillin, actin, N-WASP, betaII-spectrin, microtubules, TRBP, eIF3c, PIKE, NHERF, MAP, RalGDS, RhoGDI, EG1/magicin, HEI10, HRS, syntenin, caspr/paranodin, DCC, NGB, CRM1/exportin, SCHIP1, MYPT-1-PP1delta, RIbeta, PKA, PAK (three types), calpain and Drosophila expanded. Many of the proteins that interact with the merlin N-terminal domain also bind ezrin, while other merlin interacting proteins do not bind other members of the ERM family. Merlin also interacts with itself. This review describes these proteins, their possible roles in NF2, and the resultant hypothesized merlin functions. Review of all of the merlin interacting proteins and functional consequences of losses of these interactions reveals multiple merlin actions in PI3-kinase, MAP kinase and small GTPase signaling pathways that might be targeted to inhibit the proliferation of NF2 tumors.
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Affiliation(s)
- Daniel R Scoles
- Women's Cancer Research Institute, CSMC Burns and Allen Research Institute, Cedars-Sinai Medical Center, 8700 Beverly Boulevard, Los Angeles, CA 90048, USA.
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Muranen T, Grönholm M, Lampin A, Lallemand D, Zhao F, Giovannini M, Carpén O. The tumor suppressor merlin interacts with microtubules and modulates Schwann cell microtubule cytoskeleton. Hum Mol Genet 2007; 16:1742-51. [PMID: 17566081 DOI: 10.1093/hmg/ddm122] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The lack of neurofibromatosis 2 tumor suppressor protein merlin leads to the formation of nervous system tumors, specifically schwannomas and meningiomas. Merlin is considered to act as a tumor suppressor at the cell membrane, where it links transmembrane receptors to the actin cytoskeleton. Several tumor suppressors interact with another component of the cytoskeleton, the microtubules, in a regulated manner and control their dynamics. In this work, we identify merlin as a novel microtubule-organizing protein. We identify two tubulin-binding sites in merlin, one residing at the N-terminal FERM-domain and another at the C-terminal domain. Merlin's intramolecular association and phosphorylation of serine 518 regulate the interaction between merlin and tubulin. Analysis of cultured glioma cells indicates colocalization between merlin and microtubules especially during cell division. In primary mouse Schwann cells only minor colocalization at the cell periphery of interphase cells is seen. However, these cells drastically change their microtubule organization upon loss of merlin indicating a functional association of the proteins. Both in vitro assays and in vivo studies in Schwann cells indicate that merlin promotes tubulin polymerization. The results show that merlin plays a key role in the regulation of the Schwann cell microtubule cytoskeleton and suggest a mechanism by which loss of merlin leads to cytoskeletal defects observed in human schwannomas.
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Affiliation(s)
- Taru Muranen
- Program of Neuroscience, Department of Pathology, University of Helsinki, Biomedicum Helsinki C511, PL 63, 0014, Finland.
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Madan R, Brandwein-Gensler M, Schlecht NF, Elias K, Gorbovitsky E, Belbin TJ, Mahmood R, Breining D, Qian H, Childs G, Locker J, Smith R, Haigentz M, Gunn-Moore F, Prystowsky MB. Differential tissue and subcellular expressionof ERM proteins in normal and malignant tissues: cytoplasmic ezrin expression has prognostic signficance for head and neck squamous cell carcinoma. Head Neck 2007; 28:1018-27. [PMID: 16783828 DOI: 10.1002/hed.20435] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
BACKGROUND Members of the ezrin-radixin-moesin (ERM) protein family regulate cellular shape, motility, and proliferation and potentially influence ability to metastasize. We investigated the correlation between ERM subcellular localization and survival in patients with squamous cell carcinoma (SCC) METHODS: Tissue microarrays (TMAs) were constructed from paraffin-embedded tissue. TMA sections were evaluated for ERM protein expression immunohistochemically. The results were compared across clinical and histopathologic variables RESULTS ERM staining results for 47 patients showed that cytoplasmic ERM expression was prevalent in tumors (>92%). Whereas ezrin and moesin also localized to the membrane, only willin was found in the nucleus of tumors. Multivariable Cox regression analysis demonstrated that strong cytoplasmic ezrin expression was independently associated with poorer survival (p = .04, hazard ratio 1.82) CONCLUSIONS Both level of expression and subcellular localization of ERM proteins may be important indicators of clinical outcome in SCC. This pilot study justifies the need for an expanded validation study of ERM proteins and clinical outcome.
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Affiliation(s)
- Rashna Madan
- Department of Pathology, Albert Einstein College of Medicine, Montefiore Medical Center, 1300 Morris Park Avenue, Bronx, New York 10461, USA
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Poulikakos PI, Xiao GH, Gallagher R, Jablonski S, Jhanwar SC, Testa JR. Re-expression of the tumor suppressor NF2/merlin inhibits invasiveness in mesothelioma cells and negatively regulates FAK. Oncogene 2006; 25:5960-8. [PMID: 16652148 DOI: 10.1038/sj.onc.1209587] [Citation(s) in RCA: 144] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The neurofibromatosis type 2 NF2 gene product, merlin, is a tumor suppressor frequently inactivated in malignant mesothelioma (MM). To investigate a possible correlation between merlin inactivation and MM invasiveness, we restored merlin expression in NF2-deficient MM cells. Re-expression of merlin markedly inhibited cell motility, spreading and invasiveness, properties connected with the malignant phenotype of MM cells. To test directly whether merlin inactivation promotes invasion in a nonmalignant system, we used small interfering RNA to silence Nf2 in mouse embryonic fibroblasts (MEFs) and found that downregulation of merlin resulted in enhanced cell spreading and invasion. To delineate signaling events connected with this phenotype, we investigated the effect of merlin expression on focal adhesion kinase (FAK), a key component of cellular pathways affecting migration and invasion. Expression of merlin attenuated FAK phosphorylation at the critical phosphorylation site Tyr397 and disrupted the interaction of FAK with its binding partners Src and p85, the regulatory subunit of phosphatidylinositol-3-kinase. In addition, NF2-null MM cells stably overexpressing FAK showed increased invasiveness, which decreased significantly when merlin expression was restored. Collectively, these findings suggest that merlin inactivation is a critical step in MM pathogenesis and is related, at least in part, with upregulation of FAK activity.
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Affiliation(s)
- P I Poulikakos
- Human Genetics Program, Fox Chase Cancer Center, Philadelphia, PA 19111-2497, USA
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Perez OD, Nolan GP. Phospho-proteomic immune analysis by flow cytometry: from mechanism to translational medicine at the single-cell level. Immunol Rev 2006; 210:208-28. [PMID: 16623773 DOI: 10.1111/j.0105-2896.2006.00364.x] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Understanding a molecular basis for cellular function is a common goal of biomedicine. The complex and dynamic cellular processes underlying physiological processes become subtly or grossly perturbed in human disease. A primary objective is to demystify this complexity by creating and establishing relevant model systems to study important aspects of human disease. Although significant technological advancements over the last decade in both genomic and proteomic arenas have enabled progress, accessing the complexity of cellular interactions that occur in vivo has been a difficult arena in which to make progress. Moreover, there are extensive challenges in translating research tools to clinical applications. Flow cytometry, over the course of the last 40 years, has revolutionized the field of immunology, in both the basic science and clinical settings, as well as having been instrumental to new and exciting areas of discovery such as stem cell biology. Multiparameter machinery and systems exist now to access the heterogeneity of cellular subsets and enable phenotypic characterization and functional assays to be performed on material from both animal models and humans. This review focuses primarily on the development and application of using activation-state readouts of intracellular activity for phospho-epitopes. We present recent work on how a flow cytometric platform is used to obtain mechanistic insight into cellular processes as well as highlight the clinical applications that our laboratory has explored. Furthermore, this review discusses the challenges faced with processing high-content multidimensional and multivariate data sets. Flow cytometry, as a platform that is well situated in both the research and clinical settings, can contribute to drug discovery as well as having utility for both biomarker and patient-stratification.
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Affiliation(s)
- Omar D Perez
- The Baxter Laboratory for Genetic Pharmacology, Department of Microbiology and Immunology, Stanford University, School of Medicine, Stanford, CA 94305, USA.
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Grönholm M, Muranen T, Toby GG, Utermark T, Hanemann CO, Golemis EA, Carpén O. A functional association between merlin and HEI10, a cell cycle regulator. Oncogene 2006; 25:4389-98. [PMID: 16532029 DOI: 10.1038/sj.onc.1209475] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Merlin and ezrin are homologous proteins with opposite effects on neoplastic growth. Merlin is a tumor suppressor inactivated in the neurofibromatosis 2 disease, whereas upregulated ezrin expression is associated with increased malignancy. Merlin's tumor suppressor mechanism is not known, although participation in cell cycle regulation has been suggested. To characterize merlin's biological activities, we screened for molecules that would interact with merlin but not ezrin. We identified the cyclin B-binding protein and cell cycle regulator HEI10 as a novel merlin-binding partner. The interaction is mediated by the alpha-helical domain in merlin and the coiled-coil domain in HEI10 and requires conformational opening of merlin. The two proteins show partial subcellular colocalization, which depends on cell cycle stage and cell adhesion. Comparison of Schwann cells and schwannoma cultures demonstrated that the distribution of HEI10 depends on merlin expression. In transfected cells, a constitutively open merlin construct affected HEI10 protein integrity. These results link merlin to the cell cycle control machinery and may help to understand its tumor suppressor function.
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Affiliation(s)
- M Grönholm
- Neuroscience Program, Biomedicum Helsinki, Department of Pathology, University of Helsinki and Helsinki University Central Hospital, Helsinki, Finland.
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43
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Wolff H, Hadian K, Ziegler M, Weierich C, Kramer-Hammerle S, Kleinschmidt A, Erfle V, Brack-Werner R. Analysis of the influence of subcellular localization of the HIV Rev protein on Rev-dependent gene expression by multi-fluorescence live-cell imaging. Exp Cell Res 2006; 312:443-56. [PMID: 16368434 DOI: 10.1016/j.yexcr.2005.11.020] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2005] [Revised: 10/10/2005] [Accepted: 11/09/2005] [Indexed: 10/21/2022]
Abstract
The human immunodeficiency virus Rev protein is a post-transcriptional activator of HIV gene expression. Rev is a nucleocytoplasmic shuttle protein that displays characteristic nuclear/nucleolar subcellular localization in various cell lines. Cytoplasmic localization of Rev occurs under various conditions disrupting Rev function. The goal of this study was to investigate the relationship between localization of Rev and its functional activity in living cells. A triple-fluorescent imaging assay, called AQ-FIND, was established for automatic quantitative evaluation of nucleocytoplasmic distribution of fluorescently tagged proteins. This assay was used to screen 500 rev genes generated by error-prone PCR for Rev mutants with different localization phenotypes. Activities of the Rev mutants were determined with a second quantitative, dual-fluorescent reporter assay. In HeLa cells, the majority of nuclear Rev mutants had activities similar to wild-type Rev. The activities of Rev mutants with abnormal cytoplasmic localization ranged from moderately impaired to nonfunctional. There was no linear correlation between subcellular distribution and levels of Rev activity. In astrocytes, nuclear Rev mutants showed similar impaired activities as the cytoplasmic wild-type Rev. Our data suggest that steady-state subcellular localization is not a primary regulator of Rev activity but may change as a secondary consequence of altered Rev function. The methodologies described here have potential for studying the significance of subcellular localization for functions of other regulatory factors.
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MESH Headings
- Active Transport, Cell Nucleus
- Amino Acid Sequence
- Astrocytes/metabolism
- Astrocytes/virology
- Bacterial Proteins/genetics
- Bacterial Proteins/metabolism
- Cell Line, Tumor
- Cell Nucleus/metabolism
- Cytophotometry/methods
- Cytoplasm/metabolism
- Fatty Acids, Unsaturated/pharmacology
- Gene Expression Regulation, Viral
- Gene Products, gag/metabolism
- Gene Products, rev/genetics
- Gene Products, rev/metabolism
- Gene Products, rev/physiology
- HIV/genetics
- HIV/metabolism
- HeLa Cells
- Humans
- Image Processing, Computer-Assisted/methods
- Karyopherins/antagonists & inhibitors
- Luminescent Proteins/genetics
- Luminescent Proteins/metabolism
- Molecular Sequence Data
- Mutation/genetics
- Plasmids/genetics
- Protein Precursors/metabolism
- Receptors, Cytoplasmic and Nuclear/antagonists & inhibitors
- Sequence Homology, Amino Acid
- Transcriptional Activation/genetics
- Transfection
- Viral Structural Proteins/metabolism
- rev Gene Products, Human Immunodeficiency Virus
- Red Fluorescent Protein
- Exportin 1 Protein
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Affiliation(s)
- Horst Wolff
- Institute of Molecular Virology, GSF-National Research Center for Environment and Health, Ingolstaedterlandstr. 1, 85764 Neuherberg, Germany
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44
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McClatchey AI, Giovannini M. Membrane organization and tumorigenesis--the NF2 tumor suppressor, Merlin. Genes Dev 2005; 19:2265-77. [PMID: 16204178 DOI: 10.1101/gad.1335605] [Citation(s) in RCA: 190] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The NF2 tumor-suppressor gene was cloned more than a decade ago, but the function of its encoded protein, Merlin, remains elusive. Merlin, like the closely related ERM proteins, appears to provide regulated linkage between membrane-associated proteins and the actin cytoskeleton and is therefore poised to function in receiving and interpreting signals from the extracellular milieu. Recent studies suggest that Merlin may coordinate the processes of growth-factor receptor signaling and cell adhesion. Varying use of this organizing activity by different types of cells could provide an explanation for the unique spectrum of tumors associated with NF2 deficiency in mammals.
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Affiliation(s)
- Andrea I McClatchey
- Massachusetts General Hospital, Center for Cancer Research and Harvard Medical School, Department of Pathology, Charlestown, Massachusetts 02129, USA.
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45
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Chung JH, Eng C. Nuclear-cytoplasmic partitioning of phosphatase and tensin homologue deleted on chromosome 10 (PTEN) differentially regulates the cell cycle and apoptosis. Cancer Res 2005; 65:8096-100. [PMID: 16166282 DOI: 10.1158/0008-5472.can-05-1888] [Citation(s) in RCA: 147] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Phosphatase and tensin homologue deleted on chromosome 10 (PTEN), a tumor suppressor phosphatase that dephosphorylates both protein and lipid substrates, is found to be mutated in both heritable and sporadic breast cancer. Cellular PTEN has been shown to regulate Akt phosphorylation, mitogen-activated protein kinase (MAPK) phosphorylation, p27(kip1), and cyclin D1 protein levels. Additionally, we and others have shown that PTEN can regulate not only the cell cycle but also cellular apoptosis. Until recently, the functions of PTEN have been thought to occur through cytoplasmic PTEN. However, we have shown that PTEN localizes to the nucleus and that this localization coincides with the G0-G1 phases of the cell cycle. Furthermore, we have shown that PTEN has bipartite nuclear localization sequence (NLS)-like sequences that are required for major vault protein-mediated nuclear import. These findings suggest that subcellular localization of PTEN may regulate its function and that nuclear-localized PTEN may regulate unique cellular functions that have been attributed to cytoplasmic PTEN. To examine this possibility, we analyzed downstream PTEN readouts using MCF-7 Tet-Off breast cancer cell lines stably transfected with two different NLS mutant PTEN constructs, which do not localize to the nucleus, and compared these with cells transfected with wild-type PTEN and empty vector control cells. We found that cytoplasmic PTEN down-regulates phosphorylation of Akt and up-regulates p27(kip1), whereas nuclear PTEN down-regulates cyclin D1 and prevents the phosphorylation of MAPK. Additionally, whereas we observe that nuclear PTEN is required for cell cycle arrest, we found that cytoplasmic PTEN is required for apoptosis. Our observations show that nuclear-cytoplasmic partitioning differentially regulates the cell cycle and apoptosis and, in this manner, provide further evidence that nuclear import of PTEN should play a role in carcinogenesis.
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Affiliation(s)
- Ji-Hyun Chung
- Clinical Cancer Genetics Program, Comprehensive Cancer Center, Ohio State University, Columbus, USA
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Kuns R, Kissil JL, Newsham IF, Jacks T, Gutmann DH, Sherman LS. Protein 4.1B expression is induced in mammary epithelial cells during pregnancy and regulates their proliferation. Oncogene 2005; 24:6502-15. [PMID: 16007173 DOI: 10.1038/sj.onc.1208813] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
4.1B is a member of the protein 4.1 superfamily of proteins that link transmembrane proteins to the actin cytoskeleton. The 4.1B gene localizes to chromosome 18p11.3, which undergoes loss of heterozygosity in mammary tumors. Here, we examine the expression of 4.1B in murine mammary epithelium and find that 4.1B is dramatically upregulated in mammary epithelial cells during pregnancy when there is extensive cell proliferation. In contrast, 4.1B is not expressed in virgin, lactating, or involuting mammary epithelium. To examine the consequence of 4.1B loss on mammary epithelial cell proliferation, we analysed mammary glands in 4.1B-null mice. 4.1B loss results in a significant increase in mammary epithelial cell proliferation during pregnancy, but has no effect on mammary epithelial cell proliferation, in virgin or involuting mice. Furthermore, we show that 4.1B inhibits the proliferation of mammary epithelial cell lines by inducing a G1 cell cycle arrest, characterized by decreased cyclin A expression and reduced Rb phosphorylation, and accompanied by reduced erbB2 phosphorylation. This cell cycle arrest does not involve alterations in the activities of MAPK, JNK, or Akt. Collectively, our findings demonstrate that 4.1B regulates mammary epithelial cell proliferation during pregnancy and suggest that its loss may influence mammary carcinoma pathogenesis in multiparous women.
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Affiliation(s)
- Robin Kuns
- Division of Neuroscience, Oregon National Primate Research Center, Oregon Health & Science University, 505 NW 185th Ave., Beaverton, OR 97006, USA
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