23 results on '"Lamsoul, Isabelle"'
Search Results
2. ASB2α regulates migration of immature dendritic cells
- Author
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Lamsoul, Isabelle, Métais, Arnaud, Gouot, Emmanuelle, Heuzé, Mélina L., Lennon-Duménil, Ana-Maria, Moog-Lutz, Christel, and Lutz, Pierre G.
- Published
- 2013
- Full Text
- View/download PDF
3. Macrophage Mesenchymal Migration Requires Podosome Stabilization by Filamin A
- Author
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Guiet, Romain, Vérollet, Christel, Lamsoul, Isabelle, Cougoule, Céline, Poincloux, Renaud, Labrousse, Arnaud, Calderwood, David A., Glogauer, Michael, Lutz, Pierre G., and Maridonneau-Parini, Isabelle
- Published
- 2012
- Full Text
- View/download PDF
4. Molecular Tuning of Filamin A Activities in the Context of Adhesion and Migration
- Author
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Lamsoul, Isabelle, Dupré, Loïc, Lutz, Pierre G., Centre de Physiopathologie Toulouse Purpan (CPTP), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS), and Lutz, Pierre
- Subjects
[SDV] Life Sciences [q-bio] ,Cell and Developmental Biology ,animal structures ,actin cytoskeleton ,cell migration ,integrin ,Mini Review ,[SDV]Life Sciences [q-bio] ,cell adhesion ,Cell Biology ,macromolecular substances ,filamin ,Developmental Biology - Abstract
International audience; The dynamic organization of actin cytoskeleton meshworks relies on multiple actinbinding proteins endowed with distinct actin-remodeling activities. Filamin A is a large multi-domain scaffolding protein that cross-links actin filaments with orthogonal orientation in response to various stimuli. As such it plays key roles in the modulation of cell shape, cell motility, and differentiation throughout development and adult life. The essentiality and complexity of Filamin A is highlighted by mutations that lead to a variety of severe human disorders affecting multiple organs. One of the most conserved activity of Filamin A is to bridge the actin cytoskeleton to integrins, thereby maintaining the later in an inactive state. We here review the numerous mechanisms cells have developed to adjust Filamin A content and activity and focus on the function of Filamin A as a gatekeeper to integrin activation and associated adhesion and motility.
- Published
- 2020
5. ASB2 targets filamins A and B to proteasomal degradation
- Author
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Heuzé, Mélina L., Lamsoul, Isabelle, Baldassarre, Massimiliano, Lad, Yatish, Lévêque, Sophie, Razinia, Ziba, Moog-Lutz, Christel, Calderwood, David A., and Lutz, Pierre G.
- Published
- 2008
- Full Text
- View/download PDF
6. Ubiquitin-mediated proteasomal degradation in normal and malignant hematopoiesis
- Author
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Heuzé, Mélina L., Lamsoul, Isabelle, Moog-Lutz, Christel, and Lutz, Pierre G.
- Published
- 2008
- Full Text
- View/download PDF
7. Post-translational modifications of the Tax oncoprotein of human T-cell leukemia virus control cytoplasmic and nuclear steps in Tax-mediated activation of the NF-κB pathway
- Author
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Lodewick Julie, Lamsoul Isabelle, Sampaio Carla, and Bex Françoise
- Subjects
Immunologic diseases. Allergy ,RC581-607 - Published
- 2009
- Full Text
- View/download PDF
8. Substrates of the ASB2α E3 ubiquitin ligase in dendritic cells
- Author
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Spinner, Camille, Uttenweiler-Joseph, Sandrine, Metais, Arnaud, Stella, Alexandre, Burlet-Schiltz, Odile, Moog-Lutz, Christel, Lamsoul, Isabelle, Lutz, Pierre, Institut de pharmacologie et de biologie structurale (IPBS), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Neurosignalisation Moleculaire et Cellulaire, Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de la Santé et de la Recherche Médicale (INSERM), Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées
- Subjects
Mice, Knockout ,Proteomics ,Proteasome Endopeptidase Complex ,Ubiquitin ,Filamins ,Ubiquitin-Protein Ligases ,[SDV]Life Sciences [q-bio] ,Suppressor of Cytokine Signaling Proteins ,Dendritic Cells ,[SDV.BC]Life Sciences [q-bio]/Cellular Biology ,Article ,Mice ,Cell Line, Tumor ,Animals ,Humans ,[SDV.BBM]Life Sciences [q-bio]/Biochemistry, Molecular Biology ,ComputingMilieux_MISCELLANEOUS ,Adaptor Proteins, Signal Transducing ,HeLa Cells - Abstract
International audience; Conventional dendritic cells (cDCs) comprise distinct populations with specialized immune functions that are mediators of innate and adaptive immune responses. Transcriptomic and proteomic approaches have been used so far to identify transcripts and proteins that are differentially expressed in these subsets to understand the respective functions of cDCs subsets. Here, we showed that the Cullin 5-RING E3 ubiquitin ligase (E3) ASB2α, by driving degradation of filamin A (FLNa) and filamin B (FLNb), is responsible for the difference in FLNa and FLNb abundance in the different spleen cDC subsets. Importantly, the ability of these cDC subsets to migrate correlates with the level of FLNa. Furthermore, our results strongly point to CD4 positive and double negative cDCs as distinct populations. Finally, we develop quantitative global proteomic approaches to identify ASB2α substrates in DCs using ASB2 conditional knockout mice. As component of the ubiquitinproteasome system (UPS) are amenable to pharmacological manipulation, these approaches aimed to the identification of E3 substrates in physiological relevant settings could potentially lead to novel targets for therapeutic strategies.
- Published
- 2015
9. Cullin 5-RING E3 ubiquitin ligases, new therapeutic targets?
- Author
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Lamsoul, Isabelle, Uttenweiler-Joseph, Sandrine, Moog-Lutz, Christel, and Lutz, Pierre G.
- Subjects
- *
UBIQUITIN ligases , *TARGETED drug delivery , *POST-translational modification , *FOCAL adhesion kinase , *DNA damage - Abstract
Ubiquitylation is a reversible post-translational modification of proteins that controls a myriad of functions and cellular processes. It occurs through the sequential action of three distinct enzymes. E3 ubiquitin ligases (E3s) play the role of conductors of the ubiquitylation pathway making them attractive therapeutic targets. This review is dedicated to the largest family of multimeric E3s, the Cullin-RING E3 (CRL) family and more specifically to cullin 5 based CRLs that remains poorly characterized. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
10. Phosphorylation of serine 323 of ASB2α is pivotal for the targeting of filamin A to degradation.
- Author
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Zakaria, Rim, Lamsoul, Isabelle, Uttenweiler-Joseph, Sandrine, Erard, Monique, Monsarrat, Bernard, Burlet-Schiltz, Odile, Moog-Lutz, Christel, and Lutz, Pierre G.
- Subjects
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SERINE proteinases , *FILAMINS , *BIODEGRADATION , *PHOSPHORYLATION , *MASS spectrometry , *MICROFILAMENT proteins - Abstract
Abstract: ASB proteins are the specificity subunits of cullin5-RING E3 ubiquitin ligases (CRL5) that play roles in ubiquitin-mediated protein degradation. However, how their activity is regulated remains poorly understood. Here, we unravel a novel mechanism of regulation of a CRL5 through phosphorylation of its specificity subunit ASB2α. Indeed, using mass spectrometry, we showed for the first time that ASB2α is phosphorylated and that phosphorylation of serine-323 (Ser-323) of ASB2α is crucial for the targeting of the actin-binding protein filamin A (FLNa) to degradation. Mutation of ASB2α Ser-323 to Ala had no effect on intrinsic E3 ubiquitin ligase activity of ASB2α but abolished the ability of ASB2α to induce degradation of FLNa. In contrast, the ASB2α Ser-323 to Asp phosphomimetic mutant induced acute degradation of FLNa. Moreover, inhibition of the extracellular signal-regulated kinases 1 and 2 (Erk1/2) activity reduced ASB2α-mediated FLNa degradation. We further showed that the subcellular localization of ASB2α to actin-rich structures is dependent on ASB2α Ser-323 phosphorylation and propose that the interaction with FLNa depends on the electrostatic potential redistribution induced by the Ser-323 phosphate group. Taken together, these data unravel an important mechanism by which ASB2α-mediated FLNa degradation can be regulated. [Copyright &y& Elsevier]
- Published
- 2013
- Full Text
- View/download PDF
11. Filamins but Not Janus Kinases Are Substrates of the ASB2α Cullin- Ring E3 Ubiquitin Ligase in Hematopoietic Cells.
- Author
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Lamsoul, Isabelle, Erard, Monique, van der Ven, Peter F. M., Lutz, Pierre G., and Zhengqi Wang
- Subjects
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PROTEINS , *UBIQUITIN ligases , *MICROFILAMENT proteins , *FILAMINS , *HEMATOPOIESIS , *MOLECULAR models - Abstract
The ASB2α protein is the specificity subunit of an E3 ubiquitin ligase complex involved in hematopoietic differentiation and is proposed to exert its effects by regulating the turnover of specific proteins. Three ASB2α substrates have been described so far: the actin-binding protein filamins, the Mixed Lineage Leukemia protein, and the Janus kinases 2 and 3. To determine the degradation of which substrate drives ASB2α biological effects is crucial for the understanding of ASB2α functions in hematopoiesis. Here, we show that neither endogenous nor exogenously expressed ASB2α induces degradation of JAK proteins in hematopoietic cells. Furthermore, we performed molecular modeling to generate the first structural model of an E3 ubiquitin ligase complex of an ASB protein bound to one of its substrates. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
12. Functional and Structural Insights into ASB2α, a Novel Regulator of Integrin-dependent Adhesion of Hematopoietic Cells.
- Author
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Lamsoul, Isabelle, Burande, Clara F., Razinia, Ziba, Houles, Thibault C., Menoret, Delphine, Baldassarre, Massimiliano, Erard, Monique, Moog-Lutz, Christel, Calderwood, David A., and Lutz, Pierre G.
- Subjects
- *
INTEGRINS , *HEMATOPOIETIC stem cells , *CELL adhesion , *FIBRONECTINS , *MOLECULAR models - Abstract
By providing contacts between hematopoietic cells and the bone marrow microenvironment, integrins are implicated in cell adhesion and thereby in control of cell fate of normal and leukemia cells. The ASB2 gene, initially identified as a retinoic acid responsive gene and a target of the promyelocytic leukemia retinoic acid receptor α oncoprotein in acute promyelocytic leukemia cells, encodes two isoforms, a hematopoietic-type (ASB2α) and a muscle-type (ASB2β) that are involved in hematopoietic and myogenic differentiation, respectively. ASB2α is the specificity subunit of an E3 ubiquitin ligase complex that targets filamins to proteasomal degradation. To examine the relationship of the ASB2α structure to E3 ubiquitin ligase function, functional assays and molecular modeling were performed. We show that ASB2α, through filamin A degradation, enhances adhesion of hematopoietic cells to fibronectin, the main ligand of β1 integrins. Furthermore, we demonstrate that a short N-terminal region specific to ASB2α, together with ankyrin repeats 1 to 10, is necessary for association of ASB2α with filamin A. Importantly, the ASB2α N-terminal region comprises a 9-residue segment with predicted structural homology to the filamin-binding motifs of migfilin and β integrins. Together, these data provide new insights into the molecular mechanisms of ASB2α binding to filamin. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
13. Move or Die: the Fate of the Tax Oncoprotein of HTLV-1.
- Author
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Lodewick, Julie, Lamsoul, Isabelle, and Bex, Françoise
- Subjects
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HTLV-I , *RETROVIRUSES , *MYC proteins , *LEUKEMIA , *T cells - Abstract
The HTLV-1 Tax protein both activates viral replication and is involved in HTLV-1-mediated transformation of T lymphocytes. The transforming properties of Tax include altering the expression of select cellular genes via activation of cellular pathways and perturbation of both cell cycle control mechanisms and apoptotic signals. The recent discovery that Tax undergoes a hierarchical sequence of posttranslational modifications that control its intracellular localization provides provocative insights into the mechanisms regulating Tax transcriptional and transforming activities. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
14. Acetylation of the human T-cell leukemia virus type 1 Tax oncoprotein by p300 promotes activation of the NF-κB pathway
- Author
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Lodewick, Julie, Lamsoul, Isabelle, Polania, Angela, Lebrun, Sylvie, Burny, Arsène, Ratner, Lee, and Bex, Françoise
- Subjects
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HTLV-I , *ACETYLATION , *PROTEINS , *EVOKED potentials (Electrophysiology) , *CARCINOGENS , *NF-kappa B , *PHOSPHORYLATION , *LYMPHOCYTES - Abstract
Abstract: The oncogenic potential of the HTLV-1 Tax protein involves activation of the NF-κB pathway, which depends on Tax phosphorylation, ubiquitination and sumoylation. We demonstrate that the nuclei of Tax-expressing cells, including HTLV-1 transformed T-lymphocytes, contain a pool of Tax molecules acetylated on lysine residue at amino acid position 346 by the transcriptional coactivator p300. Phosphorylation of Tax on serine residues 300/301 was a prerequisite for Tax localization in the nucleus and correlated with its subsequent acetylation by p300, whereas sumoylation, resulting in the formation of Tax nuclear bodies in which p300 was recruited, favored Tax acetylation. Overexpression of p300 markedly increased Tax acetylation and the ability of a wild type HTLV-1 provirus, –but not of a mutant provirus carrying an acetylation deficient Tax gene–, to activate gene expression from an integrated NF-κB-controlled promoter. Thus, Tax acetylation favors NF-κB activation and might play an important role in HTLV-1-induced cell transformation. [Copyright &y& Elsevier]
- Published
- 2009
- Full Text
- View/download PDF
15. Exclusive Ubiquitination and Sumoylation on Overlapping Lysine Residues Mediate NF-κB Activation by the Human T-Cell Leukemia Virus Tax Oncoprotein.
- Author
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Lamsoul, Isabelle, Lodewick, Julie, Lebrun, Sylvie, Brasseur, Robert, Burny, Arsène, Gaynor, Richard B., and Bex, Françoise
- Subjects
- *
NF-kappa B , *UBIQUITIN , *LYSINE , *T cells , *ADULT T-cell leukemia , *LEUKEMIA , *CYTOPLASM , *GENE expression - Abstract
The transcription factor NF-κB is critical for the induction of cancer, including adult T-cell leukemia, which is linked to infection by human T-cell leukemia virus type 1 and the expression of its regulatory protein Tax. Although activation of the NF-κB pathway by Tax involves its interaction with the regulatory subunit of the IκB kinase (IKK) complex, NEMO/IKKγ the mechanism by which Tax activates specific cellular genes in the nucleus remains unknown. Here, we demonstrate that the attachment of SUMO-1 to Tax regulates its localization in nuclear bodies and the recruitment of both the RelA subunit of NF-κB and free IKKγ in these nuclear structures. However, this sumoylation step is not sufficient for the activation of the NF-κB pathway by Tax. This activity requires the prior ubiquitination and colocalization of ubiquitinated Tax with IKK complexes in the cytoplasm and the subsequent migration of the RelA subunit of NF-κB to the nucleus. Thus, the ubiquitination and sumoylation of Tax function in concert to result in the migration of RelA to the nucleus and its accumulation with IKKγ in nuclear bodies for activation of gene expression. These modifications may result in targets for the treatment of adult T-cell leukemia. [ABSTRACT FROM AUTHOR]
- Published
- 2005
- Full Text
- View/download PDF
16. Stable Ubiquitination of Human T-Cell Leukemia Virus Type 1 Tax Is Required for Proteasome Binding.
- Author
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Chiari, Estelle, Lamsoul, Isabelle, Lodewick, Julie, Chopin, Cécile, Bex, Françoise, and Pique, Claudine
- Subjects
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UBIQUITIN , *LEUKEMIA , *T cells , *VIROLOGY , *MICROBIOLOGY , *MICROORGANISMS - Abstract
Human T-cell leukemia virus type 1 (HTLV-1) is the retrovirus responsible for adult T-cell leukemia and HTLV-1-associated myelopathy. Adult T-cell leukemia development is mainly due to the ability of the viral oncoprotein Tax to promote T-cell proliferation, whereas the appearance of HTLV-1-associated myelopathy involves the antigenic properties of Tax. Understanding the events regulating the intracellular level of Tax is therefore an important issue. How Tax is degraded has not been determined, but it is known that Tax binds to proteasomes, the major sites for degradation of intracellular proteins, generally tagged through polyubiquitin conjugation. In this study, we investigated the relationship between Tax, ubiquitin, and proteasomes. We report that mono- and polyubiquitinated Tax proteins can be recovered from both transfected 293T cells and T lymphocytes. We also show that lysine residues located in the carboxy-terminal domain of Tax are the principal targets of this process. Remarkably, we further demonstrate that mutation of lysine residues in the C-terminal part of Tax, which massively reduces Tax ubiquitination, impairs proteasome binding, and conversely, that a Tax mutant that binds poorly to this particle (M22) is faintly ubiquitinated, suggesting that Tax ubiquitination is required for association with cellular proteasomes. Finally, we document that comparable amounts of ubiquitinated species were found whether proteasome activities were inhibited or not, providing evidence that they are not directly addressed to proteasomes for degradation. These findings indicate that although it is ubiquitinated and binds to proteasomes, Tax is not massively degraded via the ubiquitin-proteasome pathway and therefore reveal that Tax conjugation to ubiquitin mediates a nonproteolytic function. [ABSTRACT FROM AUTHOR]
- Published
- 2004
- Full Text
- View/download PDF
17. Molecular Tuning of Filamin A Activities in the Context of Adhesion and Migration.
- Author
-
Lamsoul I, Dupré L, and Lutz PG
- Abstract
The dynamic organization of actin cytoskeleton meshworks relies on multiple actin-binding proteins endowed with distinct actin-remodeling activities. Filamin A is a large multi-domain scaffolding protein that cross-links actin filaments with orthogonal orientation in response to various stimuli. As such it plays key roles in the modulation of cell shape, cell motility, and differentiation throughout development and adult life. The essentiality and complexity of Filamin A is highlighted by mutations that lead to a variety of severe human disorders affecting multiple organs. One of the most conserved activity of Filamin A is to bridge the actin cytoskeleton to integrins, thereby maintaining the later in an inactive state. We here review the numerous mechanisms cells have developed to adjust Filamin A content and activity and focus on the function of Filamin A as a gatekeeper to integrin activation and associated adhesion and motility., (Copyright © 2020 Lamsoul, Dupré and Lutz.)
- Published
- 2020
- Full Text
- View/download PDF
18. The E3 Ubiquitin Ligase Asb2α in T Helper 2 Cells Negatively Regulates Antitumor Immunity in Colorectal Cancer.
- Author
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Spinner CA, Lamsoul I, Métais A, Febrissy C, Moog-Lutz C, and Lutz PG
- Subjects
- Animals, Binding Sites, Cell Differentiation genetics, Cell Differentiation immunology, Colorectal Neoplasms genetics, Colorectal Neoplasms pathology, Computational Biology methods, Databases, Genetic, Gene Expression Profiling, Hematopoietic Stem Cells cytology, Hematopoietic Stem Cells metabolism, Humans, Immunophenotyping, Mice, Protein Binding, Recurrence, T-Lymphocyte Subsets immunology, T-Lymphocyte Subsets metabolism, Transcription Factors metabolism, Ubiquitin-Protein Ligases genetics, Colorectal Neoplasms immunology, Colorectal Neoplasms metabolism, Immunomodulation, Th2 Cells immunology, Th2 Cells metabolism, Ubiquitin-Protein Ligases metabolism
- Abstract
The escape of cancer cells from host immunosurveillance involves a shift in immune responses, including an imbalance in Th1 and Th2 cells. A Th1-dominated immune response predicts positive outcomes in colorectal cancer. The E3 ubiquitin ligase, Asb2α, is expressed in Th2 cells, but its roles in T-cell maturation and cancer are unclear. We provide evidence that the Th2 master regulator, Gata3, induces Asb2 Loss of Asb2 did not affect Th differentiation ex vivo , but reduced IL4 production from Th2 cells. We found that high ASB2 expression was associated with poor outcome in colorectal cancer. Loss of Asb2 from hematopoietic cells promoted a Th1 response and attenuated colitis-associated tumorigenesis in mice. Diminished Th2 function correlated with increased IFNγ production and an enhanced type 1 antitumor immune response in Asb2 -deficient mice. Our work suggests that Asb2α promotes a Th2 phenotype in vivo , which in turn is associated with tumor progression in a mouse model of colitis., (©2019 American Association for Cancer Research.)
- Published
- 2019
- Full Text
- View/download PDF
19. Substrates of the ASB2α E3 ubiquitin ligase in dendritic cells.
- Author
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Spinner CA, Uttenweiler-Joseph S, Metais A, Stella A, Burlet-Schiltz O, Moog-Lutz C, Lamsoul I, and Lutz PG
- Subjects
- Animals, Cell Line, Tumor, Filamins metabolism, HeLa Cells, Humans, Mice, Mice, Knockout, Proteasome Endopeptidase Complex metabolism, Proteomics methods, Suppressor of Cytokine Signaling Proteins, Ubiquitin metabolism, Adaptor Proteins, Signal Transducing metabolism, Dendritic Cells metabolism, Ubiquitin-Protein Ligases metabolism
- Abstract
Conventional dendritic cells (cDCs) comprise distinct populations with specialized immune functions that are mediators of innate and adaptive immune responses. Transcriptomic and proteomic approaches have been used so far to identify transcripts and proteins that are differentially expressed in these subsets to understand the respective functions of cDCs subsets. Here, we showed that the Cullin 5-RING E3 ubiquitin ligase (E3) ASB2α, by driving degradation of filamin A (FLNa) and filamin B (FLNb), is responsible for the difference in FLNa and FLNb abundance in the different spleen cDC subsets. Importantly, the ability of these cDC subsets to migrate correlates with the level of FLNa. Furthermore, our results strongly point to CD4 positive and double negative cDCs as distinct populations. Finally, we develop quantitative global proteomic approaches to identify ASB2α substrates in DCs using ASB2 conditional knockout mice. As component of the ubiquitin-proteasome system (UPS) are amenable to pharmacological manipulation, these approaches aimed to the identification of E3 substrates in physiological relevant settings could potentially lead to novel targets for therapeutic strategies.
- Published
- 2015
- Full Text
- View/download PDF
20. The E3 ubiquitin ligase specificity subunit ASB2α targets filamins for proteasomal degradation by interacting with the filamin actin-binding domain.
- Author
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Razinia Z, Baldassarre M, Bouaouina M, Lamsoul I, Lutz PG, and Calderwood DA
- Subjects
- Animals, CHO Cells, Cell Line, Tumor, Cells, Cultured, Contractile Proteins genetics, Cricetinae, Cricetulus, Filamins, Fluorescent Antibody Technique, HeLa Cells, Humans, Immunoblotting, Mice, Microfilament Proteins genetics, Protein Binding, Ubiquitin-Protein Ligases genetics, Contractile Proteins metabolism, Microfilament Proteins metabolism, Proteasome Endopeptidase Complex metabolism, Ubiquitin-Protein Ligases metabolism
- Abstract
Filamins are an important family of actin-binding and crosslinking proteins that mediate remodeling of the actin cytoskeleton and maintain extracellular matrix connections by anchoring transmembrane proteins to actin filaments and linking them to intracellular signaling cascades. We recently found that filamins are targeted for proteasomal degradation by the E3 ubiquitin ligase specificity subunit ASBα and that acute degradation of filamins through this ubiquitin-proteasome pathway correlates with cell differentiation. Specifically, in myeloid leukemia cells retinoic-acid-induced expression of ASB2α triggers filamin degradation and recapitulates early events crucial for cell differentiation. ASB2α is thought to link substrates to the ubiquitin transferase machinery; however, the mechanism by which ASB2α interacts with filamin to induce degradation remained unknown. Here, we use cell-based and biochemical assays to show that the subcellular localization of ASB2α to actin-rich structures is dependent on filamin and that the actin-binding domain (ABD) of filamin mediates the interaction with ASB2α. Furthermore, we show that the ABD is necessary and sufficient for ASB2α-mediated filamin degradation. We propose that ASB2α exerts its effect by binding the ABD and mediating its polyubiquitylation, so targeting filamins for degradation. These studies provide the molecular basis for ASB2α-mediated filamin degradation and unravel an important mechanism by which filamin levels can be acutely regulated.
- Published
- 2011
- Full Text
- View/download PDF
21. Filamins regulate cell spreading and initiation of cell migration.
- Author
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Baldassarre M, Razinia Z, Burande CF, Lamsoul I, Lutz PG, and Calderwood DA
- Subjects
- Actins chemistry, Animals, Cell Line, Tumor, Cell Movement, Contractile Proteins metabolism, Filamins, Humans, Immunoglobulins chemistry, Jurkat Cells, Microfilament Proteins metabolism, Models, Biological, Mutation, Phenotype, Proteasome Endopeptidase Complex metabolism, Contractile Proteins physiology, Microfilament Proteins physiology
- Abstract
Mammalian filamins (FLNs) are a family of three large actin-binding proteins. FLNa, the founding member of the family, was implicated in migration by cell biological analyses and the identification of FLNA mutations in the neuronal migration disorder periventricular heterotopia. However, recent knockout studies have questioned the relevance of FLNa to cell migration. Here we have used shRNA-mediated knockdown of FLNa, FLNb or FLNa and FLNb, or, alternatively, acute proteasomal degradation of all three FLNs, to generate FLN-deficient cells and assess their ability to migrate. We report that loss of FLNa or FLNb has little effect on migration but that knockdown of FLNa and FLNb, or proteolysis of all three FLNs, impairs migration. The observed defect is primarily a deficiency in initiation of motility rather than a problem with maintenance of locomotion speed. FLN-deficient cells are also impaired in spreading. Re-expression of full length FLNa, but not re-expression of a mutated FLNa lacking immunoglobulin domains 19 to 21, reverts both the spreading and the inhibition of initiation of migration.Our results establish a role for FLNs in cell migration and spreading and suggest that compensation by other FLNs may mask phenotypes in single knockout or knockdown cells. We propose that interactions between FLNs and transmembrane or signalling proteins, mediated at least in part by immunoglobulin domains 19 to 21 are important for both cell spreading and initiation of migration.
- Published
- 2009
- Full Text
- View/download PDF
22. A label-free quantitative proteomics strategy to identify E3 ubiquitin ligase substrates targeted to proteasome degradation.
- Author
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Burande CF, Heuzé ML, Lamsoul I, Monsarrat B, Uttenweiler-Joseph S, and Lutz PG
- Subjects
- Amino Acid Sequence, Cell Line, Tumor, Contractile Proteins genetics, Contractile Proteins metabolism, Filamins, Humans, Leukemia, Myeloid metabolism, Microfilament Proteins genetics, Microfilament Proteins metabolism, Molecular Sequence Data, Suppressor of Cytokine Signaling Proteins genetics, Suppressor of Cytokine Signaling Proteins metabolism, Talin genetics, Talin metabolism, Ubiquitin metabolism, Ubiquitin-Protein Ligases genetics, Proteasome Endopeptidase Complex metabolism, Proteomics methods, Ubiquitin-Protein Ligases metabolism
- Abstract
The ubiquitin-proteasome system is a central mechanism for controlled proteolysis that regulates numerous cellular processes in eukaryotes. As such, defects in this system can contribute to disease pathogenesis. In this pathway, E3 ubiquitin ligases provide platforms for binding specific substrates, thereby coordinating their ubiquitylation and subsequent degradation by the proteasome. Despite the identification of many E3 ubiquitin ligases, the identities of their specific substrates are still largely unresolved. The ankyrin repeat-containing protein with a suppressor of cytokine signaling box 2 (ASB2) gene that we initially identified as a retinoic acid-response gene in acute promyelocytic leukemia cells encodes the specificity subunit of an E3 ubiquitin ligase complex that is involved in hematopoietic cell differentiation. We have recently identified filamin A and filamin B as the first ASB2 targets and shown that ASB2 triggers ubiquitylation and proteasome-mediated degradation of these proteins. Here a global quantitative proteomics strategy is provided to identify substrates of E3 ubiquitin ligases targeted to proteasomal degradation. Indeed we used label-free methods for quantifying proteins identified by shotgun proteomics in extracts of cells expressing wild-type ASB2 or an E3 ubiquitin ligase-defective mutant of ASB2 under the control of an inducible promoter. Measurements of spectral count and mass spectrometric signal intensity demonstrated a drastic decrease of filamin A and filamin B in myeloid leukemia cells expressing wild-type ASB2 compared with cells expressing an E3 ubiquitin ligase-defective mutant of ASB2. Altogether we provide an original strategy that enables identification of E3 ubiquitin ligase substrates that have to be degraded.
- Published
- 2009
- Full Text
- View/download PDF
23. Gene activation and gene silencing: a subtle equilibrium.
- Author
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Quivy V, Calomme C, Dekoninck A, Demonte D, Bex F, Lamsoul I, Vanhulle C, Burny A, and Van Lint C
- Subjects
- Acetylation, Animals, Cell Nucleus genetics, Cell Nucleus ultrastructure, Chromatin Assembly and Disassembly, Heterochromatin metabolism, Histones metabolism, Humans, Promoter Regions, Genetic, Retroviridae genetics, Transcriptional Activation, Gene Expression Regulation, Gene Silencing, Heterochromatin genetics
- Abstract
The genetic make-up of a cell resides entirely in its DNA. Now that the nucleotide sequence of several genomes has been determined, the major challenging problem is to understand how cell differentiation, proliferation or death are controlled. Major steps include analysis of the determinants of the cell cycle, the unravelling of RNAs and proteins involved in the control of gene expression and the dissection of the protein-destruction machinery. The successive steps to be considered are transcription of RNA on the DNA template, mRNA stabilization or degradation, and mRNA translation and protein localization in the right cell compartment. Gene expression or gene silencing is the result of many DNA-RNA-protein interactions and chromatin is among the key regulators of gene expression. Open chromatin (euchromatin) allows expression of the DNA message. This chromatin structure is generally characterized by the presence on the gene promoters of transcription complexes associated with histone acetyltransferases (HATs). On the contrary, closed chromatin (heterochromatin) is poorly acetylated and more condensed. It contains histone deacetylases (HDACs), potentially associated with DNA methyltransferases (DNMTs). DNMT activity leads to methylation and silencing of the DNA. Thus, a major problem in the field of gene regulation resides in understanding chromatin structure at each promoter, a formidable task for the years to come.
- Published
- 2004
- Full Text
- View/download PDF
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