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Chang CY, Pearce G, Betaneli V, Kapustsenka T, Hosseini K, Fischer-Friedrich E, Corbeil D, Karbanová J, Taubenberger A, Dahncke B, Rauner M, Furesi G, Perner S, Rost F, Jessberger R. The F-actin bundler SWAP-70 promotes tumor metastasis. Life Sci Alliance 2024; 7:e202302307. [PMID: 38760173 PMCID: PMC11101836 DOI: 10.26508/lsa.202302307] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2023] [Revised: 05/08/2024] [Accepted: 05/09/2024] [Indexed: 05/19/2024] Open
Abstract
Dynamic rearrangements of the F-actin cytoskeleton are a hallmark of tumor metastasis. Thus, proteins that govern F-actin rearrangements are of major interest for understanding metastasis and potential therapies. We hypothesized that the unique F-actin binding and bundling protein SWAP-70 contributes importantly to metastasis. Orthotopic, ectopic, and short-term tail vein injection mouse breast and lung cancer models revealed a strong positive dependence of lung and bone metastasis on SWAP-70. Breast cancer cell growth, migration, adhesion, and invasion assays revealed SWAP-70's key role in these metastasis-related cell features and the requirement for SWAP-70 to bind F-actin. Biophysical experiments showed that tumor cell stiffness and deformability are negatively modulated by SWAP-70. Together, we present a hitherto undescribed, unique F-actin modulator as an important contributor to tumor metastasis.
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Affiliation(s)
- Chao-Yuan Chang
- https://ror.org/042aqky30 Institute for Physiological Chemistry, Medical Faculty Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
| | - Glen Pearce
- https://ror.org/042aqky30 Institute for Physiological Chemistry, Medical Faculty Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
| | - Viktoria Betaneli
- https://ror.org/042aqky30 Institute for Physiological Chemistry, Medical Faculty Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
| | - Tatsiana Kapustsenka
- https://ror.org/042aqky30 Institute for Physiological Chemistry, Medical Faculty Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
| | - Kamran Hosseini
- https://ror.org/042aqky30 Cluster of Excellence Physics of Life, Technische Universität Dresden, Dresden, Germany
| | - Elisabeth Fischer-Friedrich
- https://ror.org/042aqky30 Cluster of Excellence Physics of Life, Technische Universität Dresden, Dresden, Germany
| | - Denis Corbeil
- Biotechnology Center (BIOTEC) and Center for Molecular and Cellular Bioengineering, Dresden, Germany
- https://ror.org/042aqky30 Medical Faculty Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
| | - Jana Karbanová
- Biotechnology Center (BIOTEC) and Center for Molecular and Cellular Bioengineering, Dresden, Germany
- https://ror.org/042aqky30 Medical Faculty Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
| | - Anna Taubenberger
- Biotechnology Center (BIOTEC) and Center for Molecular and Cellular Bioengineering, Dresden, Germany
- https://ror.org/042aqky30 Medical Faculty Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
| | - Björn Dahncke
- https://ror.org/042aqky30 Institute for Physiological Chemistry, Medical Faculty Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
| | - Martina Rauner
- https://ror.org/042aqky30 Department of Medicine III and Center for Healthy Aging, Medical Faculty Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
| | - Giulia Furesi
- https://ror.org/042aqky30 Department of Medicine III and Center for Healthy Aging, Medical Faculty Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
| | - Sven Perner
- Institute of Pathology, University of Lübeck and University Hospital Schleswig-Holstein, Lübeck, Germany
- Institute of Pathology, Research Center Borstel, Leibniz Lung Center, Borstel, Germany
| | - Fabian Rost
- https://ror.org/042aqky30 DRESDEN-concept Genome Center, Technology Platform at the Center for Molecular and Cellular Bioengineering (CMCB), Technische Universität Dresden, Dresden, Germany
| | - Rolf Jessberger
- https://ror.org/042aqky30 Institute for Physiological Chemistry, Medical Faculty Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
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Alzahrani AS, Alswailem M, Murugan AK, Alghamdi B, Al-Hindi H. Papillary thyroid cancer and a TERT promotor mutation-positive paraganglioma in a patient with a germline SDHB mutation. J Endocr Soc 2022; 6:bvac076. [PMID: 35673401 PMCID: PMC9165429 DOI: 10.1210/jendso/bvac076] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Indexed: 11/19/2022] Open
Abstract
Abstract
Purpose
About 40% of paragangliomas (PGL) are due to germline mutations in one of several susceptibility genes. These genes rarely predispose to other non-PGL tumors. Here, we describe and functionally characterize a germline SDHB mutation in a patient who developed a BRAFV600E mutation-positive papillary thyroid cancer (PTC) and a TERT promotor mutation-positive PGL.
Experimental design
A 28-year-old asymptomatic man was discovered incidentally to have a large left-sided mid abdominal PGL and PTC. He underwent resection of the PGL and total thyroidectomy and neck dissection followed by I-131 adjuvant therapy for PTC. The histopathology revealed a high-grade PGL and a tall cell variant PTC with lymph node metastases (T1b N1b M0). He soon developed PGL spinal metastases that have been rapidly progressing and is currently being treated with Lu 177-dotatate therapy. Family screening revealed a positive SDHB mutation in the mother, a son and a brother.
Results
In addition to the heterozygous SDHB germline mutation (c.688C>T, p.Arg230Cys), molecular analysis revealed a somatic TERT promotor mutation (C228T) in PGL (negative in PTC), and a somatic BRAFV600E mutation in PTC (negative in PGL). Functional studies showed a higher proliferation rate in the mutant compared to the wild type SDHB.
Conclusion
Germline SDHB mutations rarely occur in patients with PTC and may contribute to the its aggressiveness. Somatic TERT promotor mutations rarely occur in PGL and contribute to its aggressiveness and metastatic potential.
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Affiliation(s)
- Ali S Alzahrani
- Department of Molecular Oncology, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia
- Department of Medicine, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia
| | - Meshael Alswailem
- Department of Molecular Oncology, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia
| | | | - Balgees Alghamdi
- Department of Molecular Oncology, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia
| | - Hindi Al-Hindi
- Department of Pathology and Laboratory Medicine, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia
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Shi L, Liu H, Wang Y, Chong Y, Wang J, Liu G, Zhang X, Chen X, Li H, Niu M, Liang J, Yu R, Liu X. SWAP-70 promotes glioblastoma cellular migration and invasion by regulating the expression of CD44s. Cancer Cell Int 2019; 19:305. [PMID: 31832018 PMCID: PMC6873484 DOI: 10.1186/s12935-019-1035-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Accepted: 11/15/2019] [Indexed: 12/24/2022] Open
Abstract
BACKGROUND Switch-associated protein 70 (SWAP-70) is a guanine nucleotide exchange factor that is involved in cytoskeletal rearrangement and regulation of migration and invasion of malignant tumors. However, the mechanism by which SWAP-70 regulates the migration and invasion of glioblastoma (GB) cells has not been fully elucidated. METHODS This study used an online database to analyze the relationship between SWAP-70 expression and prognosis in GB patients. The in vitro wound healing assay and transwell invasion assay were used to determine the role of SWAP-70 in GB cell migration and invasion as well as the underlying mechanism. RESULTS We found that patients with high SWAP-70 expression in the GB had a poor prognosis. Downregulation of SWAP-70 inhibited GB cell migration and invasion, whereas SWAP-70 overexpression had an opposite effect. Interestingly, SWAP-70 expression was positively correlated with the expression of the standard form of CD44 (CD44s) in GB tissues. Downregulation of SWAP-70 also reduced CD44s protein expression, whereas SWAP-70 overexpression enhanced CD44s protein expression. However, downregulation of SWAP-70 expression did not affect the mRNA expression of CD44s. Reversal experiments showed that overexpressing CD44s in cell lines with downregulated SWAP-70 partially abolished the inhibitory effects of downregulated SWAP-70 on GB cell migration and invasion. CONCLUSIONS These results suggest that SWAP-70 may promote GB cell migration and invasion by regulating the expression of CD44s. SWAP-70 may serve as a new biomarker and a potential therapeutic target for GB.
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Affiliation(s)
- Lin Shi
- Institute of Nervous System Diseases, Affiliated Hospital of Xuzhou Medical University, Xuzhou Medical University, Xuzhou, Jiangsu China
| | - Huize Liu
- Institute of Nervous System Diseases, Affiliated Hospital of Xuzhou Medical University, Xuzhou Medical University, Xuzhou, Jiangsu China
| | - Yifeng Wang
- Institute of Nervous System Diseases, Affiliated Hospital of Xuzhou Medical University, Xuzhou Medical University, Xuzhou, Jiangsu China
| | - Yulong Chong
- Institute of Nervous System Diseases, Affiliated Hospital of Xuzhou Medical University, Xuzhou Medical University, Xuzhou, Jiangsu China
- Nanjing Durm Tower Hospital Group, Suqian City People’s Hospital, Suqian, Jiangsu China
| | - Jie Wang
- Institute of Nervous System Diseases, Affiliated Hospital of Xuzhou Medical University, Xuzhou Medical University, Xuzhou, Jiangsu China
| | - Guanzheng Liu
- Institute of Nervous System Diseases, Affiliated Hospital of Xuzhou Medical University, Xuzhou Medical University, Xuzhou, Jiangsu China
| | - Xu Zhang
- Department of Neurosurgery, Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu China
| | - Xiangyu Chen
- Institute of Nervous System Diseases, Affiliated Hospital of Xuzhou Medical University, Xuzhou Medical University, Xuzhou, Jiangsu China
| | - Huan Li
- Institute of Nervous System Diseases, Affiliated Hospital of Xuzhou Medical University, Xuzhou Medical University, Xuzhou, Jiangsu China
| | - Mingshan Niu
- Institute of Nervous System Diseases, Affiliated Hospital of Xuzhou Medical University, Xuzhou Medical University, Xuzhou, Jiangsu China
- Blood Diseases Institute, Xuzhou Medical University, Xuzhou, Jiangsu China
| | - Jun Liang
- Department of Neurosurgery, Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu China
| | - Rutong Yu
- Institute of Nervous System Diseases, Affiliated Hospital of Xuzhou Medical University, Xuzhou Medical University, Xuzhou, Jiangsu China
- Department of Neurosurgery, Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu China
| | - Xuejiao Liu
- Institute of Nervous System Diseases, Affiliated Hospital of Xuzhou Medical University, Xuzhou Medical University, Xuzhou, Jiangsu China
- Department of Neurosurgery, Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu China
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Ijuin T. Phosphoinositide phosphatases in cancer cell dynamics-Beyond PI3K and PTEN. Semin Cancer Biol 2019; 59:50-65. [PMID: 30922959 DOI: 10.1016/j.semcancer.2019.03.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2018] [Revised: 03/18/2019] [Accepted: 03/18/2019] [Indexed: 12/16/2022]
Abstract
Phosphoinositides are a group of lipids that regulate intracellular signaling and subcellular biological events. The signaling by phosphatidylinositol-3,4,5-trisphosphate and Akt mediates the action of growth factors that are essential for cell proliferation, gene transcription, cell migration, and polarity. The hyperactivation of this signaling has been identified in different cancer cells; and, it has been implicated in oncogenic transformation and cancer cell malignancy. Recent studies have argued the role of phosphoinositides in cancer cell dynamics, including actin cytoskeletal rearrangement at the plasma membrane and the organization of intracellular compartments. The focus of this review is to summarize the impact of the activities of phosphoinositide phosphatases on intracellular signaling related to cancer cell dynamics and to discuss how the abnormalities in the activities of the enzymes alter the levels of phosphoinositides in cancer cells.
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Affiliation(s)
- Takeshi Ijuin
- Division of Biochemistry, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki, Chu-o, Kobe 650-0017, Japan.
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5
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Kriplani N, Duncan RR, Leslie NR. SWAP70 undergoes dynamic conformational regulation at the leading edge of migrating cells. FEBS Lett 2019; 593:395-405. [PMID: 30636036 DOI: 10.1002/1873-3468.13326] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2018] [Revised: 12/19/2018] [Accepted: 12/23/2018] [Indexed: 01/01/2023]
Abstract
Rearrangements of the actin cytoskeleton are regulated in part by dynamic localised activation and inactivation of Rho family small GTPases. SWAP70 binds to and activates the small GTPase RAC1 as well as binding to filamentous actin and PIP3 . We have developed an encoded biosensor, which uses Forster resonance energy transfer to reveal conformational changes in SWAP70 in live cells. SWAP70 adopts a distinct conformation at the plasma membrane, which in migrating glioma cells is enriched at the leading edge but does not always associate with its PIP3 -dependent translocation to the membrane. This supports a role for SWAP70 in positive feedback activation of RAC1 at sites of filamentous actin, PIP3 and active RAC1.
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Affiliation(s)
- Nisha Kriplani
- Institute of Biological Chemistry, Biophysics and Bioengineering, School of Engineering and Physical Sciences, Heriot Watt University, Edinburgh, UK
| | - Rory R Duncan
- Institute of Biological Chemistry, Biophysics and Bioengineering, School of Engineering and Physical Sciences, Heriot Watt University, Edinburgh, UK
| | - Nicholas R Leslie
- Institute of Biological Chemistry, Biophysics and Bioengineering, School of Engineering and Physical Sciences, Heriot Watt University, Edinburgh, UK
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Baranov MV, Revelo NH, Verboogen DRJ, Ter Beest M, van den Bogaart G. SWAP70 is a universal GEF-like adaptor for tethering actin to phagosomes. Small GTPases 2018; 10:311-323. [PMID: 28489960 PMCID: PMC6548301 DOI: 10.1080/21541248.2017.1328302] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
We recently identified a key role for SWAP70 as the tethering factor stabilizing F-actin filaments on the surface of phagosomes in human dendritic cells by interacting both with Rho-family GTPases and the lipid phosphatidylinositol (3,4)-bisphosphate. In this study, we aimed to investigate whether this role of SWAP70 was general among immune phagocytes. Our data reveal that SWAP70 is recruited to early phagosomes of macrophages and dendritic cells from both human and mouse. The putative inhibitor of SWAP70 sanguinarine blocked phagocytosis and F-actin polymerization, supporting a key role for SWAP70 in phagocytosis as demonstrated previously with knock-down. Moreover, SWAP70 was recently shown to sequester the F-actin severing protein cofilin and we investigated this relationship in phagocytosis. Our data show an increased activation of cellular cofilin upon siRNA knockdown of SWAP70. Finally, we explored whether SWAP70 would be recruited to the immune synapse between dendritic cells and T cells required for antigen presentation, as the formation of such synapses depends on F-actin. However, we observed that SWAP70 was depleted at immune synapses and specifically was recruited to phagosomes. Our data support an essential and specific role for SWAP70 in tethering and stabilizing F-actin to the phagosomal surface in a wide range of phagocytes.
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Affiliation(s)
- Maksim V Baranov
- a Department of Tumor Immunology , Radboud University Medical Center, Radboud Institute for Molecular Life Sciences , Nijmegen , The Netherlands
| | - Natalia H Revelo
- a Department of Tumor Immunology , Radboud University Medical Center, Radboud Institute for Molecular Life Sciences , Nijmegen , The Netherlands
| | - Daniëlle R J Verboogen
- a Department of Tumor Immunology , Radboud University Medical Center, Radboud Institute for Molecular Life Sciences , Nijmegen , The Netherlands
| | - Martin Ter Beest
- a Department of Tumor Immunology , Radboud University Medical Center, Radboud Institute for Molecular Life Sciences , Nijmegen , The Netherlands
| | - Geert van den Bogaart
- a Department of Tumor Immunology , Radboud University Medical Center, Radboud Institute for Molecular Life Sciences , Nijmegen , The Netherlands
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7
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Baranov MV, Revelo NH, Dingjan I, Maraspini R, Ter Beest M, Honigmann A, van den Bogaart G. SWAP70 Organizes the Actin Cytoskeleton and Is Essential for Phagocytosis. Cell Rep 2017; 17:1518-1531. [PMID: 27806292 PMCID: PMC5149533 DOI: 10.1016/j.celrep.2016.10.021] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Revised: 09/05/2016] [Accepted: 10/06/2016] [Indexed: 10/25/2022] Open
Abstract
Actin plays a critical role during the early stages of pathogenic microbe internalization by immune cells. In this study, we identified a key mechanism of actin filament tethering and stabilization to the surface of phagosomes in human dendritic cells. We found that the actin-binding protein SWAP70 is specifically recruited to nascent phagosomes by binding to the lipid phosphatidylinositol (3,4)-bisphosphate. Multi-color super-resolution stimulated emission depletion (STED) microscopy revealed that the actin cage surrounding early phagosomes is formed by multiple concentric rings containing SWAP70. SWAP70 colocalized with and stimulated activation of RAC1, a known activator of actin polymerization, on phagosomes. Genetic ablation of SWAP70 impaired actin polymerization around phagosomes and resulted in a phagocytic defect. These data show a key role for SWAP70 as a scaffold for tethering the peripheral actin cage to phagosomes.
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Affiliation(s)
- Maksim V Baranov
- Department of Tumor Immunology, Radboud University Medical Center, Radboud Institute for Molecular Life Sciences, Geert Grooteplein 28, 6525GA Nijmegen, the Netherlands
| | - Natalia H Revelo
- Department of Tumor Immunology, Radboud University Medical Center, Radboud Institute for Molecular Life Sciences, Geert Grooteplein 28, 6525GA Nijmegen, the Netherlands
| | - Ilse Dingjan
- Department of Tumor Immunology, Radboud University Medical Center, Radboud Institute for Molecular Life Sciences, Geert Grooteplein 28, 6525GA Nijmegen, the Netherlands
| | - Riccardo Maraspini
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany
| | - Martin Ter Beest
- Department of Tumor Immunology, Radboud University Medical Center, Radboud Institute for Molecular Life Sciences, Geert Grooteplein 28, 6525GA Nijmegen, the Netherlands
| | - Alf Honigmann
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany
| | - Geert van den Bogaart
- Department of Tumor Immunology, Radboud University Medical Center, Radboud Institute for Molecular Life Sciences, Geert Grooteplein 28, 6525GA Nijmegen, the Netherlands.
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Tokuda N, Kawai K, Lee YH, Ikegami T, Yamaguchi S, Yagisawa H, Fukui Y, Tuzi S. Membrane-induced alteration of the secondary structure in the SWAP-70 pleckstrin homology domain. J Biochem 2012; 151:391-401. [DOI: 10.1093/jb/mvr146] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
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The Guanine Nucleotide Exchange Factor SWAP-70 Modulates the Migration and Invasiveness of Human Malignant Glioma Cells. Transl Oncol 2011; 2:300-9. [PMID: 19956392 DOI: 10.1593/tlo.09172] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2009] [Revised: 06/30/2009] [Accepted: 08/07/2009] [Indexed: 11/18/2022] Open
Abstract
The malignant glioma is the most common primary human brain tumor. Its tendency to invade away from the primary tumor mass is considered a leading cause of tumor recurrence and treatment failure. Accordingly, the molecular pathogenesis of glioma invasion is currently under investigation. Previously, we examined a gene expression array database comparing human gliomas to nonneoplastic controls and identified several Rac guanine nucleotide exchange factors with differential expression. Here, we report that the guanine nucleotide exchange factor SWAP-70 has increased expression in malignant gliomas and strongly correlates with lowered patient survival. SWAP-70 is a multifunctional signaling protein involved in membrane ruffling that works cooperatively with activated Rac. Using a glioma tissue microarray, we validated that SWAP-70 demonstrates higher expression in malignant gliomas compared with low-grade gliomas or nonneoplastic brain tissue. Through immunofluorescence, SWAP-70 localizes to membrane ruffles in response to the growth factor, epidermal growth factor. To assess the role of SWAP-70 in glioma migration and invasion, we inhibited its expression withsmall interfering RNAs and observed decreased glioma cell migration and invasion. SWAP-70 overexpression led to increased levels of active Rac even in low-serum conditions. In addition, when SWAP-70 was overexpressed in glioma cells, we observed enhanced membrane ruffle formation followed by increased cellmigration and invasiveness. Taken together, our findings suggest that the guanine nucleotide exchange factor SWAP-70 plays an important role in the migration and invasion of human gliomas into the surrounding tissue.
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Fukui Y, Ihara S. A mutant of SWAP-70, a phosphatidylinositoltrisphosphate binding protein, transforms mouse embryo fibroblasts, which is inhibited by sanguinarine. PLoS One 2010; 5:e14180. [PMID: 21152038 PMCID: PMC2996291 DOI: 10.1371/journal.pone.0014180] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2010] [Accepted: 11/05/2010] [Indexed: 11/18/2022] Open
Abstract
SWAP-70, a phosphatidylinositol trisphosphate (PtdIns(3,4,5)P3) binding protein, has been suggested to be involved in transformation of mouse embryo fibroblasts (MEFs) as well as membrane ruffling after growth factor stimulation of the cells. A mutant, SWAP-70-374, was found to be able to bind to F-actin in vitro, whereas wild-type SWAP-70 failed to do so. This mutant was present at the plasma membrane without any stimulation while the wild-type protein was present only in the cytosol unless cells were stimulated with EGF. Expression of this mutant in MEFs resulted in morphologic transformation, fast growth, and loss of contact inhibition, suggesting that SWAP-70 with this mutation can transform the cells. ERK1/2 was activated in SWAP-70-374-transformed cells. Use of MEK inhibitors revealed that the ERK1/2 pathway does not affect the cell growth of MEFs but is responsible for loss of contact inhibition. To investigate the function of SWAP-70 further, drugs that can inhibit SWAP-70-dependent cell responses were screened. Among various drugs, sanguinarine was found to inhibit transformation of MEFs by SWAP-70-374. This drug was able to inhibit SWAP-70-mediated membrane ruffling as well, suggesting that its effect was closely related to the SWAP-70 signaling pathway. These results suggest that SWAP-70-374 can activate some signaling pathways, including the ERK1/2 pathway, to transform MEFs.
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Affiliation(s)
- Yasuhisa Fukui
- Laboratory of Signal Transduction, Hoshi University, Tokyo, Japan.
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