101
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Martin B, Schneider R, Janetzky S, Waibler Z, Pandur P, Kühl M, Behrens J, von der Mark K, Starzinski-Powitz A, Wixler V. The LIM-only protein FHL2 interacts with beta-catenin and promotes differentiation of mouse myoblasts. J Cell Biol 2002; 159:113-22. [PMID: 12370240 PMCID: PMC2173499 DOI: 10.1083/jcb.200202075] [Citation(s) in RCA: 120] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
FHL2 is a LIM-domain protein expressed in myoblasts but down-regulated in malignant rhabdomyosarcoma cells, suggesting an important role of FHL2 in muscle development. To investigate the importance of FHL2 during myoblast differentiation, we performed a yeast two-hybrid screen using a cDNA library derived from myoblasts induced for differentiation. We identified beta-catenin as a novel interaction partner of FHL2 and confirmed the specificity of association by direct in vitro binding tests and coimmunoprecipitation assays from cell lysates. Deletion analysis of both proteins revealed that the NH2-terminal part of beta-catenin is sufficient for binding in yeast, but addition of the first armadillo repeat is necessary for binding FHL2 in mammalian cells, whereas the presence of all four LIM domains of FHL2 is needed for the interaction. Expression of FHL2 counteracts beta-catenin-mediated activation of a TCF/LEF-dependent reporter gene in a dose-dependent and muscle cell-specific manner. After injection into Xenopus embryos, FHL2 inhibited the beta-catenin-induced axis duplication. C2C12 mouse myoblasts stably expressing FHL2 show increased myogenic differentiation reflected by accelerated myotube formation and expression of muscle-specific proteins. These data imply that FHL2 is a muscle-specific repressor of LEF/TCF target genes and promotes myogenic differentiation by interacting with beta-catenin.
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Affiliation(s)
- Bernd Martin
- Institut der Anthropologie und Humangenetik für Biologen, Johann-Wolfgang-Goethe-Universität, 60323 Frankfurt, Germany
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102
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McLoughlin P, Ehler E, Carlile G, Licht JD, Schäfer BW. The LIM-only protein DRAL/FHL2 interacts with and is a corepressor for the promyelocytic leukemia zinc finger protein. J Biol Chem 2002; 277:37045-53. [PMID: 12145280 DOI: 10.1074/jbc.m203336200] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Members of the four-and-a-half-LIM domain (FHL) protein family, which are expressed in a tissue- and stage-specific manner, have been reported previously to function as transcriptional coactivators. One of these is the p53-inducible protein DRAL/FHL2 (where DRAL is down-regulated in rhabdomyosarcoma LIM domain protein). In this work, we identified potential binding partners for DRAL/FHL2 using an inducible yeast two-hybrid system. We present evidence of a functional interaction between the promyelocytic leukemia zinc finger protein (PLZF) and DRAL/FHL2. PLZF is a sequence-specific transcriptional repressor whose function relies on recruitment of corepressors that form part of the histone deacetylase complex involved in chromatin remodeling. DRAL/FHL2 interacts specifically with PLZF in vitro and in vivo and augments transcriptional repression mediated by PLZF. This is the first reported incidence of a bona fide FHL protein-mediated corepression and supports the notion of these proteins having a role as coregulators of tissue-specific gene expression.
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Affiliation(s)
- Patricia McLoughlin
- Division of Clinical Chemistry and Biochemistry, Department of Pediatrics, University of Zürich, CH-8032 Zürich, Switzerland
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103
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Amaar YG, Thompson GR, Linkhart TA, Chen ST, Baylink DJ, Mohan S. Insulin-like growth factor-binding protein 5 (IGFBP-5) interacts with a four and a half LIM protein 2 (FHL2). J Biol Chem 2002; 277:12053-60. [PMID: 11821401 DOI: 10.1074/jbc.m110872200] [Citation(s) in RCA: 105] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Recent studies using insulin-like growth factor I (IGF-I) knockout mice demonstrate that IGF-binding protein (IGFBP)-5, an important bone formation regulator, itself is a growth factor with cellular effects not dependent on IGFs. Because IGFBP-5 contains a nuclear localization sequence that mediates transport of IGFBP-5 into the nucleus, we propose that IGFBP-5 interacts with nuclear proteins to affect transcription of genes involved in bone formation. We therefore undertook studies to identify proteins that bind to IGFBP-5 using IGFBP-5 as bait in a yeast two-hybrid screen of a U2 human osteosarcoma cDNA library. Five related clones that interacted strongly with the bait corresponded to the FHL2 gene, which contains four and a half LIM domains. Co-immunoprecipitation studies with lysates from U2 cells overexpressing FHL2 and IGFBP-5 confirmed that interaction between IGFBP-5 and FHL2 occurs in whole cells. In vitro interaction studies revealed that purified FHL2 interacted with IGFBP-5 but not with IGFBP-3, -4, or -6. Northern blot analysis showed that FHL2 was strongly expressed in human osteoblasts. Nuclear localization of both FHL2 and IGFBP-5 was evident from Western immunoblot analysis and immunofluorescence. The role of FHL2 as an intracellular mediator of the effects of IGFBP-5 and other osteoregulatory agents in osteoblasts will need to be verified in future studies.
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Affiliation(s)
- Yousef G Amaar
- Musculoskeletal Disease Center, Jerry L. Pettis Veterans Affairs Medical Center, Loma Linda, California 92357, USA
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104
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El Mourabit H, Poinat P, Koster J, Sondermann H, Wixler V, Wegener E, Laplantine E, Geerts D, Georges-Labouesse E, Sonnenberg A, Aumailley M. The PDZ domain of TIP-2/GIPC interacts with the C-terminus of the integrin alpha5 and alpha6 subunits. Matrix Biol 2002; 21:207-14. [PMID: 11852236 DOI: 10.1016/s0945-053x(01)00198-6] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Different cDNA libraries were screened by the yeast two-hybrid system using as a bait the cytoplasmic sequence of integrin alpha6A or alpha6B subunits. Surprisingly, the same PDZ domain-containing protein, TIP-2/GIPC, was isolated with either of the variants, although their sequences are different. Direct interaction assays with the cytoplasmic domain of the integrin alpha1--7 subunits revealed that in addition to alpha6A and alpha6B, TIP-2/GIPC reacted also with alpha5, but not other alpha integrin subunits. The specificity of the interaction was confirmed by in vitro protein binding assays with purified peptides corresponding to integrin cytoplasmic domains. Further analysis with either truncation fragments of TIP-2/GIPC or mutated integrin cytoplasmic domains indicated that the interaction occurs between the PDZ domain of TIP-2/GIPC and a consensus PDZ domain-binding sequence, SDA, present at the C-terminus of the integrin alpha5 and alpha6A subunits. The integrin alpha6B subunit terminates with a different sequence, SYS, which may represent a new PDZ domain-binding motif.
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Affiliation(s)
- Haquima El Mourabit
- Institute for Biochemistry II, Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 52, 50931 Cologne, Germany
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105
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Vossmeyer D, Hofmann W, Löster K, Reutter W, Danker K. Phospholipase Cgamma binds alpha1beta1 integrin and modulates alpha1beta1 integrin-specific adhesion. J Biol Chem 2002; 277:4636-43. [PMID: 11724770 DOI: 10.1074/jbc.m105415200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Integrin adhesion receptors have been implicated in bidirectional signal transduction. The dynamic regulation of integrin affinity and avidity as well as post-ligand effects involved in outside-in signaling depends on the interaction of integrins with cytoskeletal and signaling proteins. In this study, we attempted to identify cytoplasmic binding partners of alpha(1)beta(1) integrin. We were able to show that cell adhesion to alpha(1)beta(1)-specific substrates results in the association of phospholipase Cgamma (PLCgamma) with the alpha(1)beta(1) integrin independent of PLCgamma tyrosine phosphorylation. Using peptide-binding assays, the membrane proximal sequences within the alpha(1)beta(1) integrin subunits were identified as binding sites for PLCgamma. In particular, the conserved sequence of beta(1) subunit binds the enzyme very efficiently. Because purified PLCgamma also binds the integrin peptides, binding seems to be direct. Inhibition of PLC by leads to reduced cell adhesion on alpha(1)beta(1)-specific substrates. Cells lacking the conserved domain of the alpha(1) subunit fail to respond to the PLC inhibition, indicating that this domain is necessary for PLC-dependent adhesion modulation of alpha(1)beta(1) integrin.
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Affiliation(s)
- Dörte Vossmeyer
- Institut für Molekularbiologie und Biochemie, Freie Universität Berlin, Arnimallee 22, D-14195 Berlin-Dahlem, Germany
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106
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Müller JM, Metzger E, Greschik H, Bosserhoff AK, Mercep L, Buettner R, Schüle R. The transcriptional coactivator FHL2 transmits Rho signals from the cell membrane into the nucleus. EMBO J 2002; 21:736-48. [PMID: 11847121 PMCID: PMC125855 DOI: 10.1093/emboj/21.4.736] [Citation(s) in RCA: 147] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
GTPases of the Rho family are transducers of extracellular signals and control cellular processes such as organization of the actin cytoskeleton, motility, adhesion and gene regulation. The Rho signalling pathway is activated, for example, by bioactive sphingolipids such as sphingosine-1-phosphate (SPP) or by overexpression of Rho family members in tumorigenesis and metastases. Here, we show that stimulation of the Rho signalling pathway induces translocation of the transcriptional LIM-only coactivator FHL2 to the nucleus and subsequent activation of FHL2- and androgen receptor-dependent genes. Interestingly, prostate tumours overexpress Rho GTPases and display altered cellular localization of FHL2 concomitant with tumour dedifferentiation. SPP-induced FHL2 activation is mediated by Rho GTPases, but not by the GTPases Cdc42, Rac1 or Ras, and depends on Rho-kinase. In addition, Rho signalling influences other transcriptional coactivators, thus pointing to a general regulatory role for Rho GTPases in cofactor function. In summary, our data propose a yet undescribed signalling pathway in which the coactivator FHL2 acts as a novel molecular transmitter of the Rho signalling pathway, thereby integrating extracellular cues into altered gene expression.
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Affiliation(s)
| | | | - Holger Greschik
- Universitäts-Frauenklinik und Zentrum für Klinische Forschung, Klinikum der Universität Freiburg, Breisacherstrasse 66, D-79106 Freiburg,
Institut für Pathologie, Klinikum der RWTH Aachen, Pauwelstrasse 30, D-52074 Aachen and Institut für Pathologie, Universitätsklinikum Bonn, Sigmund-Freud-Strasse 25, D-53127 Bonn, Germany Present address: IGBMC, 1 rue Laurent Fries, BP 163, F-67404 Illkirch Cedex, France Corresponding author e-mail:
| | - Anja-Katrin Bosserhoff
- Universitäts-Frauenklinik und Zentrum für Klinische Forschung, Klinikum der Universität Freiburg, Breisacherstrasse 66, D-79106 Freiburg,
Institut für Pathologie, Klinikum der RWTH Aachen, Pauwelstrasse 30, D-52074 Aachen and Institut für Pathologie, Universitätsklinikum Bonn, Sigmund-Freud-Strasse 25, D-53127 Bonn, Germany Present address: IGBMC, 1 rue Laurent Fries, BP 163, F-67404 Illkirch Cedex, France Corresponding author e-mail:
| | | | - Reinhard Buettner
- Universitäts-Frauenklinik und Zentrum für Klinische Forschung, Klinikum der Universität Freiburg, Breisacherstrasse 66, D-79106 Freiburg,
Institut für Pathologie, Klinikum der RWTH Aachen, Pauwelstrasse 30, D-52074 Aachen and Institut für Pathologie, Universitätsklinikum Bonn, Sigmund-Freud-Strasse 25, D-53127 Bonn, Germany Present address: IGBMC, 1 rue Laurent Fries, BP 163, F-67404 Illkirch Cedex, France Corresponding author e-mail:
| | - Roland Schüle
- Universitäts-Frauenklinik und Zentrum für Klinische Forschung, Klinikum der Universität Freiburg, Breisacherstrasse 66, D-79106 Freiburg,
Institut für Pathologie, Klinikum der RWTH Aachen, Pauwelstrasse 30, D-52074 Aachen and Institut für Pathologie, Universitätsklinikum Bonn, Sigmund-Freud-Strasse 25, D-53127 Bonn, Germany Present address: IGBMC, 1 rue Laurent Fries, BP 163, F-67404 Illkirch Cedex, France Corresponding author e-mail:
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107
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Ng EKO, Chan KK, Wong CH, Tsui SKW, Ngai SM, Lee SMY, Kotaka M, Lee CY, Waye MMY, Fung KP. Interaction of the heart-specific LIM domain protein, FHL2, with DNA-binding nuclear protein, hNP220. J Cell Biochem 2002. [DOI: 10.1002/jcb.10041] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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108
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van der Flier A, Kuikman I, Kramer D, Geerts D, Kreft M, Takafuta T, Shapiro SS, Sonnenberg A. Different splice variants of filamin-B affect myogenesis, subcellular distribution, and determine binding to integrin [beta] subunits. J Cell Biol 2002; 156:361-76. [PMID: 11807098 PMCID: PMC2199218 DOI: 10.1083/jcb.200103037] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Integrins connect the extracellular matrix with the cell interior, and transduce signals through interactions of their cytoplasmic tails with cytoskeletal and signaling proteins. Using the yeast two-hybrid system, we isolated a novel splice variant (filamin-Bvar-1) of the filamentous actin cross-linking protein, filamin-B, that interacts with the cytoplasmic domain of the integrin beta1A and beta1D subunits. RT-PCR analysis showed weak, but wide, expression of filamin-Bvar-1 and a similar splice variant of filamin-A (filamin-Avar-1) in human tissues. Furthermore, alternative splice variants of filamin-B and filamin-C, from which the flexible hinge-1 region is deleted (DeltaH1), were induced during in vitro differentiation of C2C12 mouse myoblasts. We show that both filamin-Avar-1 and filamin-Bvar-1 bind more strongly than their wild-type isoforms to different integrin beta subunits. The mere presence of the high-affinity binding site for beta1A is not sufficient for targeting the filamin-Bvar-1 construct to focal contacts. Interestingly, the simultaneous deletion of the H1 region is required for the localization of filamin-B at the tips of actin stress fibers. When expressed in C2C12 cells, filamin-Bvar-1(DeltaH1) accelerates their differentiation into myotubes. Furthermore, filamin-B variants lacking the H1 region induce the formation of thinner myotubes than those in cells containing variants with this region. These findings suggest that specific combinations of filamin mRNA splicing events modulate the organization of the actin cytoskeleton and the binding affinity for integrins.
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Affiliation(s)
- Arjan van der Flier
- Netherlands Cancer Institute, Division of Cell Biology, 1066 CX Amsterdams, Netherlands
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109
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Kiemer AK, Takeuchi K, Quinlan MP. Identification of genes involved in epithelial-mesenchymal transition and tumor progression. Oncogene 2001; 20:6679-88. [PMID: 11709702 DOI: 10.1038/sj.onc.1204872] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2001] [Revised: 07/31/2001] [Accepted: 08/01/2001] [Indexed: 11/09/2022]
Abstract
The adenovirus E1A12S gene product (WT12S) immortalizes epithelial cells and they retain their differentiated characteristics, but certain mutants cannot do the latter. Characterization of mutant immortalized epithelial cells indicated that they had undergone epithelial mesenchymal transition (EMT). Coexpression of V12ras with WT12S leads to benign tumors, but to malignant tumors with 12S mutants. Since EMT is critical for tumor progression, identification of the molecular mechanisms involved should elucidate novel therapeutic targets. To this end, representational difference analysis (RDA) was used to identify cDNAs upregulated in the mutant cell line. Thirty-five differentially expressed mRNAs were identified and classified into several functional categories, including nine novel cDNAs. Among the 26 known cDNAs, extracellular matrix and related proteins made up the largest group of differentially expressed genes, followed by growth factors and receptors and transcription factors. There was also an ion transporter, a cytoskeletal protein, glycosylation and amidinotransferase enzymes and proteins with unknown functions. Some of the known genes have previously been associated with EMT and/or tumor progression and thus served to validate the system to obtain the desired target genes, while other cDNAs are newly linked with dedifferentiation/malignancy. Array analyses indicated that the cDNAs were specifically upregulated in invasive or metastatic tumors, especially of breast, uterus and lung, suggesting their involvement in the progression of these tumors.
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Affiliation(s)
- A K Kiemer
- Department of Pharmacy, Center of Drug Research, University of Munich, Butenandtstr. 5-13, 81377 Munich, Germany
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110
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DiPersio CM, Trevithick JE, Hynes RO. Functional comparison of the alpha3A and alpha3B cytoplasmic domain variants of the chicken alpha3 integrin subunit. Exp Cell Res 2001; 268:45-60. [PMID: 11461117 DOI: 10.1006/excr.2001.5273] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Integrin alpha3beta1 can be alternatively spliced to generate alpha3A and alpha3B cytoplasmic domain variants that are conserved among vertebrates. To identify distinct functions of these variants, we transfected cells with intact alpha3 integrins or chimeric receptors. alpha3Abeta1 and alpha3Bbeta1 each localized to focal contacts in keratinocytes on an extracellular matrix rich in laminin-5, to which both are known to bind with high affinity. However, alpha3B accumulated intracellularly in keratinocytes on collagen, suggesting that laminin binding may stabilize alpha3Bbeta1 surface expression. Neither alpha3 cytoplasmic domain affected recruitment of chimeric alpha5 integrins to fibronectin-induced focal contacts, and either substituted for the alpha5 cytoplasmic domain in alpha5beta1-mediated cell migration. However, the alpha5/alpha3B chimera localized to cell-cell borders in MDCK or CHO cells to a lesser extent than did the alpha5/alpha3A chimera. To determine whether the alpha3 cytoplasmic domains conferred distinct localization to a nonintegrin protein, we transfected cells with interleukin-2 receptor (IL-2R) chimeras containing the alpha3 cytoplasmic domains. The IL-2R/alpha3A chimera was expressed efficiently on the cell surface, while the IL-2R/alpha3B chimera accumulated intracellularly. Our findings suggest that the alpha3B cytoplasmic domain harbors a retention signal that is regulated in an intact integrin and can alter cell surface expression and distribution of alpha3beta1.
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Affiliation(s)
- C M DiPersio
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
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