1
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Nowak N, Sas-Nowosielska H, Szymański J. Nuclear Rac1 controls nuclear architecture and cell migration of glioma cells. Biochim Biophys Acta Gen Subj 2024; 1868:130632. [PMID: 38677529 DOI: 10.1016/j.bbagen.2024.130632] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Revised: 04/05/2024] [Accepted: 04/22/2024] [Indexed: 04/29/2024]
Abstract
Rac1 (Ras-related C3 botulinum toxin substrate 1) protein has been found in the cell nucleus many years ago, however, its nuclear functions are still poorly characterized but some data suggest its nuclear accumulation in cancers. We investigated nuclear Rac1 in glioma cancer cells nuclei and compared its levels and activity to normal astrocytes, and also characterized the studied cells on various nuclear properties and cell migration patterns. Nuclear Rac1 indeed was found accumulated in glioma cells, but only a small percentage of the protein was in active, GTP-bound state in comparison to healthy control. Altering the nuclear activity of Rac1 influenced chromatin architecture and cell motility in GTP-dependent and independent manner. This suggests that the landscape of Rac1 nuclear interactions might be as complicated and wide as its well-known, non-nuclear signaling.
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Affiliation(s)
- Natalia Nowak
- Laboratory of Imaging Tissue Structure and Function, Nencki Insitute of Experimental Biology of Polish Academy of Sciences, 3 Pasteur Str., 02-093, Warsaw, Poland.
| | - Hanna Sas-Nowosielska
- Laboratory of Imaging Tissue Structure and Function, Nencki Insitute of Experimental Biology of Polish Academy of Sciences, 3 Pasteur Str., 02-093, Warsaw, Poland; Institute of Epigenetics, Department of Cell Biology, University of Pennsylvania, Philadelphia, PA, USA
| | - Jędrzej Szymański
- Laboratory of Imaging Tissue Structure and Function, Nencki Insitute of Experimental Biology of Polish Academy of Sciences, 3 Pasteur Str., 02-093, Warsaw, Poland
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2
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Bailly C, Degand C, Laine W, Sauzeau V, Kluza J. Implication of Rac1 GTPase in molecular and cellular mitochondrial functions. Life Sci 2024; 342:122510. [PMID: 38387701 DOI: 10.1016/j.lfs.2024.122510] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Revised: 02/07/2024] [Accepted: 02/16/2024] [Indexed: 02/24/2024]
Abstract
Rac1 is a member of the Rho GTPase family which plays major roles in cell mobility, polarity and migration, as a fundamental regulator of actin cytoskeleton. Signal transduction by Rac1 occurs through interaction with multiple effector proteins, and its activity is regulated by guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs). The small protein is mainly anchored to the inner side of the plasma membrane but it can be found in endocellular compartments, notably endosomes and cell nuclei. The protein localizes also into mitochondria where it contributes to the regulation of mitochondrial dynamics, including both mitobiogenesis and mitophagy, in addition to signaling processes via different protein partners, such as the proapoptotic protein Bcl-2 and chaperone sigma-1 receptor (σ-1R). The mitochondrial form of Rac1 (mtRac1) has been understudied thus far, but it is as essential as the nuclear or plasma membrane forms, via its implication in regulation of oxidative stress and DNA damages. Rac1 is subject to diverse post-translational modifications, notably to a geranylgeranylation which contributes importantly to its mitochondrial import and its anchorage to mitochondrial membranes. In addition, Rac1 contributes to the mitochondrial translocation of other proteins, such as p53. The mitochondrial localization and functions of Rac1 are discussed here, notably in the context of human diseases such as cancers. Inhibitors of Rac1 have been identified (NSC-23766, EHT-1864) and some are being developed for the treatment of cancer (MBQ-167) or central nervous system diseases (JK-50561). Their effects on mtRac1 warrant further investigations. An overview of mtRac1 is provided here.
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Affiliation(s)
- Christian Bailly
- University of Lille, CNRS, Inserm, CHU Lille, UMR9020 - UMR1277 - Canther - Cancer Heterogeneity, Plasticity and Resistance to Therapies, 59000 Lille, France; University of Lille, Faculty of Pharmacy, Institut de Chimie Pharmaceutique Albert Lespagnol (ICPAL), 3 rue du Professeur Laguesse, 59000 Lille, France; OncoWitan, Consulting Scientific Office, Lille (Wasquehal) 59290, France.
| | - Claire Degand
- University of Lille, CNRS, Inserm, CHU Lille, UMR9020 - UMR1277 - Canther - Cancer Heterogeneity, Plasticity and Resistance to Therapies, 59000 Lille, France
| | - William Laine
- University of Lille, CNRS, Inserm, CHU Lille, UMR9020 - UMR1277 - Canther - Cancer Heterogeneity, Plasticity and Resistance to Therapies, 59000 Lille, France
| | - Vincent Sauzeau
- Université de Nantes, CHU Nantes, CNRS, INSERM, Institut du thorax, Nantes, France
| | - Jérôme Kluza
- University of Lille, CNRS, Inserm, CHU Lille, UMR9020 - UMR1277 - Canther - Cancer Heterogeneity, Plasticity and Resistance to Therapies, 59000 Lille, France
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3
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Koehn OJ, Lorimer E, Unger B, Harris R, Das AS, Suazo KF, Auger S, Distefano M, Prokop JW, Williams CL. GTPase splice variants RAC1 and RAC1B display isoform-specific differences in localization, prenylation, and interaction with the chaperone protein SmgGDS. J Biol Chem 2023; 299:104698. [PMID: 37059183 DOI: 10.1016/j.jbc.2023.104698] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2022] [Revised: 04/04/2023] [Accepted: 04/06/2023] [Indexed: 04/16/2023] Open
Abstract
Identifying events that regulate the prenylation and localization of small GTPases will help define new strategies for therapeutic targeting of these proteins in disorders such as cancer, cardiovascular disease, and neurological deficits. Splice variants of the chaperone protein SmgGDS (encoded by RAP1GDS1) are known to regulate prenylation and trafficking of small GTPases. The SmgGDS-607 splice variant regulates prenylation by binding pre-prenylated small GTPases, but the effects of SmgGDS binding to the small GTPase RAC1 versus the splice variant RAC1B are not well defined. Here we report unexpected differences in the prenylation and localization of RAC1 and RAC1B, and their binding to SmgGDS. Compared to RAC1, RAC1B more stably associates with SmgGDS-607, is less prenylated, and accumulates more in the nucleus. We show that the small GTPase DIRAS1 inhibits binding of RAC1 and RAC1B to SmgGDS and reduces their prenylation. These results suggest that prenylation of RAC1 and RAC1B is facilitated by binding to SmgGDS-607, but the greater retention of RAC1B by SmgGDS-607 slows RAC1B prenylation. We show that inhibiting RAC1 prenylation by mutating the CAAX motif promotes RAC1 nuclear accumulation, suggesting that differences in prenylation contribute to the different nuclear localization of RAC1 versus RAC1B. Finally, we demonstrate RAC1 and RAC1B that cannot be prenylated bind GTP in cells, indicating that prenylation is not a prerequisite for activation. We report differential expression of RAC1 and RAC1B transcripts in tissues, consistent with these two splice variants having unique functions that might arise in part from their differences in prenylation and localization.
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Affiliation(s)
- Olivia J Koehn
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI, 53226, USA
| | - Ellen Lorimer
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI, 53226, USA
| | - Bethany Unger
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI, 53226, USA
| | - Ra'Mal Harris
- Department of Pediatrics and Human Development, College of Human Medicine, Michigan State University, Grand Rapids, MI, 49503, USA
| | - Akansha S Das
- Department of Pediatrics and Human Development, College of Human Medicine, Michigan State University, Grand Rapids, MI, 49503, USA
| | - Kiall F Suazo
- Department of Chemistry, University of Minnesota, Minneapolis, MN, 55455, USAA
| | - Shelby Auger
- Department of Chemistry, University of Minnesota, Minneapolis, MN, 55455, USAA
| | - Mark Distefano
- Department of Chemistry, University of Minnesota, Minneapolis, MN, 55455, USAA
| | - Jeremy W Prokop
- Department of Pediatrics and Human Development, College of Human Medicine, Michigan State University, Grand Rapids, MI, 49503, USA; Department of Pharmacology and Toxicology, Michigan State University, East Lansing, MI, 48824, USA
| | - Carol L Williams
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI, 53226, USA.
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4
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Argueta CE, Figy C, Bouali S, Guo A, Yeung KC, Fenteany G. RKIP localizes to the nucleus through a bipartite nuclear localization signal and interaction with importin α to regulate mitotic progression. J Biol Chem 2023; 299:103023. [PMID: 36805338 PMCID: PMC10060766 DOI: 10.1016/j.jbc.2023.103023] [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: 05/12/2022] [Revised: 01/13/2023] [Accepted: 02/02/2023] [Indexed: 02/17/2023] Open
Abstract
Raf kinase inhibitor protein (RKIP) is a multifunctional modulator of intracellular signal transduction. Although most of its functions have been considered cytosolic, we show here that the localization of RKIP is primarily nuclear in both growing and quiescent Madin-Darby canine kidney epithelial cells and in Cal-51 and BT-20 human breast cancer cells. We have identified a putative bipartite nuclear localization signal (NLS) in RKIP that maps to the surface of the protein surrounding a known regulatory region. Like classical NLS sequences, the putative NLS of RKIP is rich in arginine and lysine residues. Deletion of and point mutations in the putative NLS lead to decreased nuclear localization. Point mutation of all the basic residues in the putative NLS of RKIP particularly strongly reduces nuclear localization. We found consistent results in reexpression experiments with wildtype or mutant RKIP in RKIP-silenced cells. A fusion construct of the putative NLS of RKIP alone to a heterologous reporter protein leads to nuclear localization of the fusion protein, demonstrating that this sequence alone is sufficient for import into the nucleus. We found that RKIP interacts with the nuclear transport factor importin α in BT-20 and MDA-MB-231 human breast cancer cells, suggesting importin-mediated active nuclear translocation. Taken together, these findings suggest that a bipartite NLS in RKIP interacts with importin α for active transport of RKIP into the nucleus and that this process may be involved in the regulation of mitotic progression. Evaluating the biological function of nuclear localization of RKIP, we found that the presence of the putative NLS is important for the role of RKIP in mitotic checkpoint regulation in MCF-7 human breast cancer cells.
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Affiliation(s)
- Christian E Argueta
- Department of Chemistry, University of Connecticut, Storrs, Connecticut, USA
| | - Christopher Figy
- Department of Cell and Cancer Biology, University of Toledo College of Medicine, Toledo, Ohio, USA
| | - Sawssen Bouali
- Department of Medical Chemistry, University of Szeged, Szeged, Hungary
| | - Anna Guo
- Department of Cell and Cancer Biology, University of Toledo College of Medicine, Toledo, Ohio, USA
| | - Kam C Yeung
- Department of Cell and Cancer Biology, University of Toledo College of Medicine, Toledo, Ohio, USA
| | - Gabriel Fenteany
- Department of Medical Chemistry, University of Szeged, Szeged, Hungary; ELKH-SZTE Biomimetic Systems Research Group, Eötvös Loránd Research Network, Szeged, Hungary.
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5
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Michalak DJ, Unger B, Lorimer E, Grishaev A, Williams CL, Heinrich F, Lösche M. Structural and biophysical properties of farnesylated KRas interacting with the chaperone SmgGDS-558. Biophys J 2022; 121:3684-3697. [PMID: 35614853 PMCID: PMC9617131 DOI: 10.1016/j.bpj.2022.05.028] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 05/02/2022] [Accepted: 05/19/2022] [Indexed: 11/26/2022] Open
Abstract
KRas is a small GTPase and membrane-bound signaling protein. Newly synthesized KRas is post-translationally modified with a membrane-anchoring prenyl group. KRas chaperones are therapeutic targets in cancer due to their participation in trafficking oncogenic KRas to membranes. SmgGDS splice variants are chaperones for small GTPases with basic residues in their hypervariable domain (HVR), including KRas. SmgGDS-607 escorts pre-prenylated small GTPases, while SmgGDS-558 escorts prenylated small GTPases. We provide a structural description of farnesylated and fully processed KRas (KRas-FMe) in complex with SmgGDS-558 and define biophysical properties of this interaction. Surface plasmon resonance measurements on biomimetic model membranes quantified the thermodynamics of the interaction of SmgGDS with KRas, and small-angle x-ray scattering was used to characterize complexes of SmgGDS-558 and KRas-FMe structurally. Structural models were refined using Monte Carlo and molecular dynamics simulations. Our results indicate that SmgGDS-558 interacts with the HVR and the farnesylated C-terminus of KRas-FMe, but not its G-domain. Therefore, SmgGDS-558 interacts differently with prenylated KRas than prenylated RhoA, whose G-domain was found in close contact with SmgGDS-558 in a recent crystal structure. Using immunoprecipitation assays, we show that SmgGDS-558 binds the GTP-bound, GDP-bound, and nucleotide-free forms of farnesylated and fully processed KRas in cells, consistent with SmgGDS-558 not engaging the G-domain of KRas. We found that the dissociation constant, Kd, for KRas-FMe binding to SmgGDS-558 is comparable with that for the KRas complex with PDEδ, a well-characterized KRas chaperone that also does not interact with the KRas G-domain. These results suggest that KRas interacts in similar ways with the two chaperones SmgGDS-558 and PDEδ. Therapeutic targeting of the SmgGDS-558/KRas complex might prove as useful as targeting the PDEδ/KRas complex in KRas-driven cancers.
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Affiliation(s)
- Dennis J Michalak
- Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania
| | - Bethany Unger
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Ellen Lorimer
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Alexander Grishaev
- Institute for Bioscience and Biotechnology Research, Rockville, Maryland; Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland
| | - Carol L Williams
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Frank Heinrich
- Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania; Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland.
| | - Mathias Lösche
- Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania; Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland
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6
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Kitzinger R, Fritz G, Henninger C. Nuclear RAC1 is a modulator of the doxorubicin-induced DNA damage response. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2022; 1869:119320. [PMID: 35817175 DOI: 10.1016/j.bbamcr.2022.119320] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Revised: 06/17/2022] [Accepted: 06/22/2022] [Indexed: 06/15/2023]
Abstract
Rho GTPases like RAC1 are localized on the inner side of the outer cell membrane where they act as molecular switches that can trigger signal transduction pathways in response to various extracellular stimuli. Nuclear functions of RAC1 were identified that are related to mitosis, cell cycle arrest and apoptosis. Previously, we showed that RAC1 plays a role in the doxorubicin (Dox)-induced DNA damage response (DDR). In this context it is still unknown whether cytosolic RAC1 modulates the Dox-induced DDR or if a nuclear fraction of RAC1 is involved. Here, we silenced RAC1 in mouse embryonic fibroblasts (MEF) pharmacologically with EHT1864 or by using siRNA against Rac1. Additionally, we transfected MEF with RAC1 mutants (wild-type, dominant-negative, constitutively active) containing a nuclear localization sequence (NLS). Afterwards, we analysed the Dox-induced DDR by evaluation of fluorescent nuclear γH2AX and 53BP1 foci formation, as well as by detection of activated proteins of the DDR by western blot to elucidate the role of nuclear RAC1 in the DDR. Treatment with EHT1864 as well as Rac1 knock-down reduced the Dox-induced DSB-formation to a similar extent. Enhanced nuclear localization of dominant-negative as well as constitutively active RAC1 mimicked these effects. Expression of the RAC1 mutants altered the Dox-induced amount of pP53 and pKAP1 protein. The observed effects were independent of S1981 ATM phosphorylation. We conclude that RAC1 is required for a substantial activation of the Dox-induced DDR and balanced levels of active/inactive RAC1 inside the nucleus are a prerequisite for this response.
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Affiliation(s)
- Rebekka Kitzinger
- Institute of Toxicology, Medical Faculty of the Heinrich Heine University Düsseldorf, Moorenstr. 5, 40225 Düsseldorf, Germany
| | - Gerhard Fritz
- Institute of Toxicology, Medical Faculty of the Heinrich Heine University Düsseldorf, Moorenstr. 5, 40225 Düsseldorf, Germany
| | - Christian Henninger
- Institute of Toxicology, Medical Faculty of the Heinrich Heine University Düsseldorf, Moorenstr. 5, 40225 Düsseldorf, Germany.
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7
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Yadav S, Garrido A, Hernández MC, Oliveros JC, Pérez-García V, Fraga MF, Carrera AC. PI3Kβ-regulated β-catenin mediates EZH2 removal from promoters controlling primed human ESC stemness and primitive streak gene expression. Stem Cell Reports 2022; 17:2239-2255. [PMID: 36179694 PMCID: PMC9561645 DOI: 10.1016/j.stemcr.2022.09.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Revised: 09/01/2022] [Accepted: 09/02/2022] [Indexed: 11/21/2022] Open
Abstract
The mechanism governing the transition of human embryonic stem cells (hESCs) toward differentiated cells is only partially understood. To explore this transition, the activity and expression of the ubiquitous phosphatidylinositol 3-kinase (PI3Kα and PI3Kβ) were modulated in primed hESCs. The study reports a pathway that dismantles the restraint imposed by the EZH2 polycomb repressor on an essential stemness gene, NODAL, and on transcription factors required to trigger primitive streak formation. The primitive streak is the site where gastrulation begins to give rise to the three embryonic cell layers from which all human tissues derive. The pathway involves a PI3Kβ non-catalytic action that controls nuclear/active RAC1 levels, activation of JNK (Jun N-terminal kinase) and nuclear β-catenin accumulation. β-Catenin deposition at promoters triggers release of the EZH2 repressor, permitting stemness maintenance (through control of NODAL) and correct differentiation by allowing primitive streak master gene expression. PI3Kβ epigenetic control of EZH2/β-catenin might be modulated to direct stem cell differentiation. PI3Kβ directs epigenetic control of stemness and primitive streak (PS) essential genes PI3Kβ directs RAC1/JNK/β-catenin activation and induces EZH2 promoter displacement β-Catenin/EZH2 control NODAL, a gene essential for stemness and the master PS genes PI3Kβ/PI3K activities cooperate at stemness; PI3Kβ directs PS gene expression
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Affiliation(s)
- Sudhanshu Yadav
- Department of Immunology and Oncology, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
| | - Antonio Garrido
- Department of Immunology and Oncology, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
| | - M Carmen Hernández
- Department of Immunology and Oncology, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
| | - Juan C Oliveros
- Department of Systems Biology, Bioinformatics, Centro Nacional de Biotecnología/CSIC, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
| | - Vicente Pérez-García
- Centro de Investigación Príncipe Felipe, Eduardo Primo Yúfera, 46013 Valencia, Spain
| | - Mario F Fraga
- Nanomaterials and Nanotechnology Research Center/CSIC, Health Research Institute of Asturias (ISPA), Institute of Oncology of Asturias (IUOPA), Research Center for Rare Diseases (CIBERER), 33011 Oviedo, Asturias, Spain
| | - Ana C Carrera
- Department of Immunology and Oncology, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain.
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8
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Valenta H, Dupré-Crochet S, Abdesselem M, Bizouarn T, Baciou L, Nüsse O, Deniset-Besseau A, Erard M. Consequences of the constitutive NOX2 activity in living cells: Cytosol acidification, apoptosis, and localized lipid peroxidation. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2022; 1869:119276. [PMID: 35489654 DOI: 10.1016/j.bbamcr.2022.119276] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Revised: 03/19/2022] [Accepted: 04/12/2022] [Indexed: 06/14/2023]
Abstract
The phagocyte NADPH oxidase (NOX2) is a key enzyme of the innate immune system generating superoxide anions (O2•-), precursors of reactive oxygen species. The NOX2 protein complex is composed of six subunits: two membrane proteins (gp91phox and p22phox) forming the catalytic core, three cytosolic proteins (p67phox, p47phox and p40phox) and a small GTPase Rac. The sophisticated activation mechanism of the NADPH oxidase relies on the assembly of cytosolic subunits with the membrane-bound components. A chimeric protein, called 'Trimera', composed of the essential domains of the cytosolic proteins p47phox (aa 1-286), p67phox (aa 1-212) and full-length Rac1Q61L, enables a constitutive and robust NOX2 activity in cells without the need of any stimulus. We employed Trimera as a single activating protein of the phagocyte NADPH oxidase in living cells and examined the consequences on the cell physiology of this continuous and long-term NOX activity. We showed that the sustained high level of NOX activity causes acidification of the intracellular pH, triggers apoptosis and leads to local peroxidation of lipids in the membrane. These local damages to the membrane correlate with the strong tendency of the Trimera to clusterize in the plasma membrane observed by FRET-FLIM microscopy.
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Affiliation(s)
- Hana Valenta
- Institut de Chimie Physique, UMR8000, Université Paris-Saclay, CNRS, 91405 Orsay, France
| | - Sophie Dupré-Crochet
- Institut de Chimie Physique, UMR8000, Université Paris-Saclay, CNRS, 91405 Orsay, France
| | - Mouna Abdesselem
- Institut de Chimie Physique, UMR8000, Université Paris-Saclay, CNRS, 91405 Orsay, France
| | - Tania Bizouarn
- Institut de Chimie Physique, UMR8000, Université Paris-Saclay, CNRS, 91405 Orsay, France
| | - Laura Baciou
- Institut de Chimie Physique, UMR8000, Université Paris-Saclay, CNRS, 91405 Orsay, France
| | - Oliver Nüsse
- Institut de Chimie Physique, UMR8000, Université Paris-Saclay, CNRS, 91405 Orsay, France
| | - Ariane Deniset-Besseau
- Institut de Chimie Physique, UMR8000, Université Paris-Saclay, CNRS, 91405 Orsay, France
| | - Marie Erard
- Institut de Chimie Physique, UMR8000, Université Paris-Saclay, CNRS, 91405 Orsay, France.
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9
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Electrostatic Forces Mediate the Specificity of RHO GTPase-GDI Interactions. Int J Mol Sci 2021; 22:ijms222212493. [PMID: 34830380 PMCID: PMC8622166 DOI: 10.3390/ijms222212493] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2021] [Revised: 11/15/2021] [Accepted: 11/16/2021] [Indexed: 01/13/2023] Open
Abstract
Three decades of research have documented the spatiotemporal dynamics of RHO family GTPase membrane extraction regulated by guanine nucleotide dissociation inhibitors (GDIs), but the interplay of the kinetic mechanism and structural specificity of these interactions is as yet unresolved. To address this, we reconstituted the GDI-controlled spatial segregation of geranylgeranylated RHO protein RAC1 in vitro. Various biochemical and biophysical measurements provided unprecedented mechanistic details for GDI function with respect to RHO protein dynamics. We determined that membrane extraction of RHO GTPases by GDI occurs via a 3-step mechanism: (1) GDI non-specifically associates with the switch regions of the RHO GTPases; (2) an electrostatic switch determines the interaction specificity between the C-terminal polybasic region of RHO GTPases and two distinct negatively-charged clusters of GDI1; (3) a non-specific displacement of geranylgeranyl moiety from the membrane sequesters it into a hydrophobic cleft, effectively shielding it from the aqueous milieu. This study substantially extends the model for the mechanism of GDI-regulated RHO GTPase extraction from the membrane, and could have implications for clinical studies and drug development.
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10
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Brandt AC, Koehn OJ, Williams CL. SmgGDS: An Emerging Master Regulator of Prenylation and Trafficking by Small GTPases in the Ras and Rho Families. Front Mol Biosci 2021; 8:685135. [PMID: 34222337 PMCID: PMC8242357 DOI: 10.3389/fmolb.2021.685135] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Accepted: 05/27/2021] [Indexed: 11/17/2022] Open
Abstract
Newly synthesized small GTPases in the Ras and Rho families are prenylated by cytosolic prenyltransferases and then escorted by chaperones to membranes, the nucleus, and other sites where the GTPases participate in a variety of signaling cascades. Understanding how prenylation and trafficking are regulated will help define new therapeutic strategies for cancer and other disorders involving abnormal signaling by these small GTPases. A growing body of evidence indicates that splice variants of SmgGDS (gene name RAP1GDS1) are major regulators of the prenylation, post-prenylation processing, and trafficking of Ras and Rho family members. SmgGDS-607 binds pre-prenylated small GTPases, while SmgGDS-558 binds prenylated small GTPases. This review discusses the history of SmgGDS research and explains our current understanding of how SmgGDS splice variants regulate the prenylation and trafficking of small GTPases. We discuss recent evidence that mutant forms of RabL3 and Rab22a control the release of small GTPases from SmgGDS, and review the inhibitory actions of DiRas1, which competitively blocks the binding of other small GTPases to SmgGDS. We conclude with a discussion of current strategies for therapeutic targeting of SmgGDS in cancer involving splice-switching oligonucleotides and peptide inhibitors.
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Affiliation(s)
- Anthony C Brandt
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Olivia J Koehn
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Carol L Williams
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI, United States
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11
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Hu S, Zhu L, Song Y, Zhao X, Chen Q, Pan Y, Zhang J, Bai Y, Zhang H, Shao C. Radiation-induced abscopal reproductive effect is driven by TNF-α/p38 MAPK/Rac1 axis in Sertoli cells. Am J Cancer Res 2021; 11:5742-5758. [PMID: 33897879 PMCID: PMC8058717 DOI: 10.7150/thno.56853] [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: 12/06/2020] [Accepted: 03/03/2021] [Indexed: 12/24/2022] Open
Abstract
Rationale: Radiotherapy has become a mainstay for tumor management, and more than 50% of patients with thoracic tumor need to be treated with radiotherapy. However, the potential adverse effects of thoracic radiotherapy on the reproductive system remain elusive. Methods: Western blot analysis, immunofluorescence assay and transmission electron microscopy (TEM) analysis were performed to investigate the integrity of blood-testis barrier (BTB) in male mice after hypofractionated irradiation (IR) on the right thorax. RNA sequencing, co-immunoprecipitation (IP), Duolink PLA and inhibitor experiments were carried out to demonstrate the molecular mechanisms of the BTB dynamics changes and the subsequent reproductive effect. Results: It was found that the hypofractionated IR on right thorax evoked ultrastructural destruction in distant testes, and thus caused radiation-induced abscopal reproductive effect (RIARE) in male mice. Mechanistically, thoracic IR induced significant nuclear translocation of Rac Family Small GTPase 1 (Rac1) in abscopal Sertoli cells, which closely correlated with the activation of TNF-α/p38 mitogen activated protein kinase (MAPK) pathway. Of note, YWHAZ, a critical polarity protein, was found to be co-localized with Rac1 in Sertoli cells, and this interaction was indispensable for thoracic IR-induced Rac1 nuclear translocation and subsequent degradation of BTB-associated proteins. Conclusions: Our findings imply for the first time that YWHAZ-mediated Rac1 nuclear translocation plays central roles in RIARE, and TNF-α/p38 MAPK/Rac1 axis can be employed as a therapeutic target against RIARE for young male patients receiving hypofractionated radiotherapy.
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12
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Abdrabou A, Wang Z. Regulation of the nuclear speckle localization and function of Rac1. FASEB J 2021; 35:e21235. [PMID: 33417283 DOI: 10.1096/fj.202001694r] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Revised: 11/02/2020] [Accepted: 11/16/2020] [Indexed: 11/11/2022]
Abstract
Despite significant evidence that Rac1 is localized to the nucleus, little is known regarding the function and biological significance of nuclear Rac1. Here, we showed that in response to EGF Rac1 was translocated to nuclear speckles and co-localized with the nuclear speckle marker Serine/arginine-rich splicing factor 2 (SRSF2) in Cos-7 cells. We also showed that the nuclear speckle localization of Rac1 was dependent on its T108 phosphorylation and facilitated by Rac1 polybasic region (PBR) that contains a nuclear localization signal and Rac1 GTPase activity. To gain insight into the function of Rac1 in nuclear speckles, we searched for Rac1 binding proteins in the nucleus. We isolated nuclear fraction of HEK 293 cells and incubated with GST-Rac1 and the phosphomimetic GST-Rac1T108E. We identified 463 proteins that were associated with GST-Rac1T108E, but not with GST-Rac1 by LC-MS/MS. Three notable groups of these proteins are: the heterogeneous nuclear ribonucleoproteins (hnRNPs), small nuclear ribonucleoproteins (snRNPs), and SRSFs, all of which are involved in pre-mRNA splicing and associated with nuclear speckles. We further showed by co-immunoprecipitation that Rac1 interacts with SRSF2, hnRNPA1, and U2A' in response to EGF. The interaction is dependent on T108 phosphorylation and facilitated by Rac1 PBR and GTPase activity. We showed that hnRNPA1 translocated in and out of nucleus in response to EGF in a similar pattern to Rac1. Rac1 only partially colocalized with U2A' that localizes to the actual splicing sites adjacent to nuclear speckle. Finally, we showed that Rac1 regulated EGF-induced pre-mRNA splicing and this is mediated by T108 phosphorylation. We conclude that in response to EGF, T108 phosphorylated Rac1 is targeted to nuclear speckles, interacts with multiple groups of proteins involved in pre-mRNA splicing, and regulates EGF-induced pre-mRNA splicing.
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Affiliation(s)
- Abdalla Abdrabou
- Department of Medical Genetics and Signal, Transduction Research Group, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
| | - Zhixiang Wang
- Department of Medical Genetics and Signal, Transduction Research Group, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
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13
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Splice switching an oncogenic ratio of SmgGDS isoforms as a strategy to diminish malignancy. Proc Natl Acad Sci U S A 2020; 117:3627-3636. [PMID: 32019878 DOI: 10.1073/pnas.1914153117] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The chaperone protein SmgGDS promotes cell-cycle progression and tumorigenesis in human breast and nonsmall cell lung cancer. Splice variants of SmgGDS, named SmgGDS-607 and SmgGDS-558, facilitate the activation of oncogenic members of the Ras and Rho families of small GTPases through membrane trafficking via regulation of the prenylation pathway. SmgGDS-607 interacts with newly synthesized preprenylated small GTPases, while SmgGDS-558 interacts with prenylated small GTPases. We determined that cancer cells have a high ratio of SmgGDS-607:SmgGDS-558 (607:558 ratio), and this elevated ratio is associated with reduced survival of breast cancer patients. These discoveries suggest that targeting SmgGDS splicing to lower the 607:558 ratio may be an effective strategy to inhibit the malignant phenotype generated by small GTPases. Here we report the development of a splice-switching oligonucleotide, named SSO Ex5, that lowers the 607:558 ratio by altering exon 5 inclusion in SmgGDS pre-mRNA (messenger RNA). Our results indicate that SSO Ex5 suppresses the prenylation of multiple small GTPases in the Ras, Rho, and Rab families and inhibits ERK activity, resulting in endoplasmic reticulum (ER) stress, the unfolded protein response, and ultimately apoptotic cell death in breast and lung cancer cell lines. Furthermore, intraperitoneal (i.p.) delivery of SSO Ex5 in MMTV-PyMT mice redirects SmgGDS splicing in the mammary gland and slows tumorigenesis in this aggressive model of breast cancer. Taken together, our results suggest that the high 607:558 ratio is required for optimal small GTPase prenylation, and validate this innovative approach of targeting SmgGDS splicing to diminish malignancy in breast and lung cancer.
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14
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15
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Casado-Medrano V, Barrio-Real L, Gutiérrez-Miranda L, González-Sarmiento R, Velasco EA, Kazanietz MG, Caloca MJ. Identification of a truncated β1-chimaerin variant that inactivates nuclear Rac1. J Biol Chem 2019; 295:1300-1314. [PMID: 31871052 DOI: 10.1074/jbc.ra119.008688] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 12/14/2019] [Indexed: 12/11/2022] Open
Abstract
β1-chimaerin belongs to the chimaerin family of GTPase-activating proteins (GAPs) and is encoded by the CHN2 gene, which also encodes the β2- and β3-chimaerin isoforms. All chimaerin isoforms have a C1 domain that binds diacylglycerol as well as tumor-promoting phorbol esters and a catalytic GAP domain that inactivates the small GTPase Rac. Nuclear Rac has emerged as a key regulator of various cell functions, including cell division, and has a pathological role by promoting tumorigenesis and metastasis. However, how nuclear Rac is regulated has not been fully addressed. Here, using several approaches, including siRNA-mediated gene silencing, confocal microscopy, and subcellular fractionation, we identified a nuclear variant of β1-chimaerin, β1-Δ7p-chimaerin, that participates in the regulation of nuclear Rac1. We show that β1-Δ7p-chimaerin is a truncated variant generated by alternative splicing at a cryptic splice site in exon 7. We found that, unlike other chimaerin isoforms, β1-Δ7p-chimaerin lacks a functional C1 domain and is not regulated by diacylglycerol. We found that β1-Δ7p-chimaerin localizes to the nucleus via a nuclear localization signal in its N terminus. We also identified a key nuclear export signal in β1-chimaerin that is absent in β1-Δ7p-chimaerin, causing nuclear retention of this truncated variant. Functionally analyses revealed that β1-Δ7p-chimaerin inactivates nuclear Rac and negatively regulates the cell cycle. Our results provide important insights into the diversity of chimaerin Rac-GAP regulation and function and highlight a potential mechanism of nuclear Rac inactivation that may play significant roles in pathologies such as cancer.
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Affiliation(s)
- Victoria Casado-Medrano
- Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas (CSIC), Universidad de Valladolid, 47003 Valladolid, Spain
| | - Laura Barrio-Real
- Molecular Medicine Unit and Institute of Molecular and Cellular Biology of Cancer, Biomedical Research Institute of Salamanca, University of Salamanca, 37007 Salamanca, Spain
| | - Laura Gutiérrez-Miranda
- Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas (CSIC), Universidad de Valladolid, 47003 Valladolid, Spain
| | - Rogelio González-Sarmiento
- Molecular Medicine Unit and Institute of Molecular and Cellular Biology of Cancer, Biomedical Research Institute of Salamanca, University of Salamanca, 37007 Salamanca, Spain
| | - Eladio A Velasco
- Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas (CSIC), Universidad de Valladolid, 47003 Valladolid, Spain
| | - Marcelo G Kazanietz
- Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - María J Caloca
- Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas (CSIC), Universidad de Valladolid, 47003 Valladolid, Spain
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16
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García-Torres D, Fierke CA. The chaperone SmgGDS-607 has a dual role, both activating and inhibiting farnesylation of small GTPases. J Biol Chem 2019; 294:11793-11804. [PMID: 31197034 DOI: 10.1074/jbc.ra119.007438] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Revised: 06/12/2019] [Indexed: 11/06/2022] Open
Abstract
Ras family small GTPases undergo prenylation (such as farnesylation) for proper localization to the plasma membrane, where they can initiate oncogenic signaling pathways. Small GTP-binding protein GDP-dissociation stimulator (SmgGDS) proteins are chaperones that bind and traffic small GTPases, although their exact cellular function is unknown. Initially, SmgGDS proteins were classified as guanine nucleotide exchange factors, but recent findings suggest that SmgGDS proteins also regulate prenylation of small GTPases in vivo in a substrate-selective manner. SmgGDS-607 recognizes the polybasic region and the CAAX box of several small GTPases and inhibits prenylation by impeding their entry into the geranylgeranylation pathway. Here, using recombinant and purified enzymes for prenylation and protein-binding assays, we demonstrate that SmgGDS-607 differentially regulates farnesylation of several small GTPases. SmgGDS-607 inhibited farnesylation of some proteins, such as DiRas1, by sequestering the protein and limiting modification catalyzed by protein farnesyltransferase (FTase). We found that the competitive binding affinities of the small GTPase for SmgGDS-607 and FTase dictate the extent of this inhibition. Additionally, we discovered that SmgGDS-607 increases the rate of farnesylation of HRas by enhancing product release from FTase. Our work indicates that SmgGDS-607 binds to a broad range of small GTPases and does not require a PBR for recognition. Together, these results provide mechanistic insight into SmgGDS-607-mediated regulation of farnesylation of small GTPases and suggest that SmgGDS-607 has multiple modes of substrate recognition.
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Affiliation(s)
| | - Carol A Fierke
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109
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17
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Polyphosphoinositides in the nucleus: Roadmap of their effectors and mechanisms of interaction. Adv Biol Regul 2019; 72:7-21. [PMID: 31003946 DOI: 10.1016/j.jbior.2019.04.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Revised: 04/02/2019] [Accepted: 04/03/2019] [Indexed: 01/01/2023]
Abstract
Biomolecular interactions between proteins and polyphosphoinositides (PPIn) are essential in the regulation of the vast majority of cellular processes. Consequently, alteration of these interactions is implicated in the development of many diseases. PPIn are phosphorylated derivatives of phosphatidylinositol and consist of seven species with different phosphate combinations. PPIn signal by recruiting proteins via canonical domains or short polybasic motifs. Although their actions are predominantly documented on cytoplasmic membranes, six of the seven PPIn are present within the nucleus together with the PPIn kinases, phosphatases and phospholipases that regulate their turnover. Importantly, the contribution of nuclear PPIn in the regulation of nuclear processes has led to an increased recognition of their importance compared to their more accepted cytoplasmic roles. This review summarises our knowledge on the identification and functional characterisation of nuclear PPIn-effector proteins as well as their mode of interactions, which tend to favour polybasic motifs.
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18
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Abdrabou A, Wang Z. Post-Translational Modification and Subcellular Distribution of Rac1: An Update. Cells 2018; 7:cells7120263. [PMID: 30544910 PMCID: PMC6316090 DOI: 10.3390/cells7120263] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Revised: 12/06/2018] [Accepted: 12/10/2018] [Indexed: 12/27/2022] Open
Abstract
Rac1 is a small GTPase that belongs to the Rho family. The Rho family of small GTPases is a subfamily of the Ras superfamily. The Rho family of GTPases mediate a plethora of cellular effects, including regulation of cytoarchitecture, cell size, cell adhesion, cell polarity, cell motility, proliferation, apoptosis/survival, and membrane trafficking. The cycling of Rac1 between the GTP (guanosine triphosphate)- and GDP (guanosine diphosphate)-bound states is essential for effective signal flow to elicit downstream biological functions. The cycle between inactive and active forms is controlled by three classes of regulatory proteins: Guanine nucleotide exchange factors (GEFs), GTPase-activating proteins (GAPs), and guanine-nucleotide-dissociation inhibitors (GDIs). Other modifications include RNA splicing and microRNAs; various post-translational modifications have also been shown to regulate the activity and function of Rac1. The reported post-translational modifications include lipidation, ubiquitination, phosphorylation, and adenylylation, which have all been shown to play important roles in the regulation of Rac1 and other Rho GTPases. Moreover, the Rac1 activity and function are regulated by its subcellular distribution and translocation. This review focused on the most recent progress in Rac1 research, especially in the area of post-translational modification and subcellular distribution and translocation.
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Affiliation(s)
- Abdalla Abdrabou
- Department of Medical Genetics, and Signal Transduction Research Group, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB T6G 2H7, Canada.
| | - Zhixiang Wang
- Department of Medical Genetics, and Signal Transduction Research Group, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB T6G 2H7, Canada.
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19
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Masoud R, Serfaty X, Erard M, Machillot P, Karimi G, Hudik E, Wien F, Baciou L, Houée-Levin C, Bizouarn T. Conversion of NOX2 into a constitutive enzyme in vitro and in living cells, after its binding with a chimera of the regulatory subunits. Free Radic Biol Med 2017; 113:470-477. [PMID: 29079525 DOI: 10.1016/j.freeradbiomed.2017.10.376] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Revised: 10/20/2017] [Accepted: 10/23/2017] [Indexed: 11/30/2022]
Abstract
During the phagocytosis of pathogens by phagocyte cells, the NADPH oxidase complex is activated to produce superoxide anion, a precursor of microbial oxidants. The activated NADPH oxidase complex from phagocytes consists in two transmembrane proteins (Nox2 and p22phox) and four cytosolic proteins (p40phox, p47phox, p67phox and Rac1-2). In the resting state of the cells, these proteins are dispersed in the cytosol, the membrane of granules and the plasma membrane. In order to synchronize the assembly of the cytosolic subunits on the membrane components of the oxidase, a fusion of the cytosolic proteins p47phox, p67phox and Rac1 named trimera was constructed. The trimera investigated in this paper is composed of the p47phox segment 1-286, the p67phox segment 1-212 and the mutated Rac1(Q61L). We demonstrate that the complex trimera-cyt b558 is functionally comparable to the one containing the separated subunits. Each of the subunits p47phox, p67phox and Rac1Q61L has kept its own activating property. The trimera is produced in an activated conformation as seen by circular dichroism. However, the presence of amphiphile is still necessary in a cell-free system to trigger superoxide anion production. The COS7gp91-p22 cells expressing the trimera produce continuously superoxide anion at high rate. This constitutive activity in cells can be of particular interest for understanding the NADPH oxidase functioning independently of signaling pathways.
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Affiliation(s)
- Rawand Masoud
- Laboratoire de Chimie Physique, UMR8000, Université Paris Sud, CNRS, Université Paris Saclay, 91405 Orsay, France
| | - Xavier Serfaty
- Laboratoire de Chimie Physique, UMR8000, Université Paris Sud, CNRS, Université Paris Saclay, 91405 Orsay, France
| | - Marie Erard
- Laboratoire de Chimie Physique, UMR8000, Université Paris Sud, CNRS, Université Paris Saclay, 91405 Orsay, France
| | - Paul Machillot
- Laboratoire de Chimie Physique, UMR8000, Université Paris Sud, CNRS, Université Paris Saclay, 91405 Orsay, France
| | - Gilda Karimi
- Laboratoire de Chimie Physique, UMR8000, Université Paris Sud, CNRS, Université Paris Saclay, 91405 Orsay, France
| | - Elodie Hudik
- Laboratoire de Chimie Physique, UMR8000, Université Paris Sud, CNRS, Université Paris Saclay, 91405 Orsay, France
| | - Frank Wien
- Synchrotron SOLEIL, campus Paris Saclay, Gif-sur-Yvette, France
| | - Laura Baciou
- Laboratoire de Chimie Physique, UMR8000, Université Paris Sud, CNRS, Université Paris Saclay, 91405 Orsay, France
| | - Chantal Houée-Levin
- Laboratoire de Chimie Physique, UMR8000, Université Paris Sud, CNRS, Université Paris Saclay, 91405 Orsay, France
| | - Tania Bizouarn
- Laboratoire de Chimie Physique, UMR8000, Université Paris Sud, CNRS, Université Paris Saclay, 91405 Orsay, France.
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20
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Karabiyik C, Fernandes R, Figueiredo FR, Socodato R, Brakebusch C, Lambertsen KL, Relvas JB, Santos SD. Neuronal Rho GTPase Rac1 elimination confers neuroprotection in a mouse model of permanent ischemic stroke. Brain Pathol 2017; 28:569-580. [PMID: 28960571 DOI: 10.1111/bpa.12562] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Accepted: 09/21/2017] [Indexed: 01/08/2023] Open
Abstract
The Rho GTPase Rac1 is a multifunctional protein involved in distinct pathways ranging from development to pathology. The aim of the present study was to unravel the contribution of neuronal Rac1 in regulating the response to brain injury induced by permanent focal cerebral ischemia (pMCAO). Our results show that pMCAO significantly increased total Rac1 levels in wild type mice, mainly through rising nuclear Rac1, while a reduction in Rac1 activation was observed. Such changes preceded cell death induced by excitotoxic stress. Pharmacological inhibition of Rac1 in primary neuronal cortical cells prevented the increase in oxidative stress induced after overactivation of glutamate receptors. However, this was not sufficient to prevent the associated neuronal cell death. In contrast, RNAi-mediated knock down of Rac1 in primary cortical neurons prevented cell death elicited by glutamate excitotoxicity and decreased the activity of NADPH oxidase. To test whether in vivo down regulation of neuronal Rac1 was neuroprotective after pMCAO, we used tamoxifen-inducible neuron-specific conditional Rac1-knockout mice. We observed a significant 50% decrease in brain infarct volume of knockout mice and a concomitant increase in HIF-1α expression compared to littermate control mice, demonstrating that ablation of Rac1 in neurons is neuroprotective. Transmission electron microscopy performed in the ischemic brain showed that lysosomes in the infarct of Rac1- knockout mice were preserved at similar levels to those of non-infarcted tissue, while littermate mice displayed a decrease in the number of lysosomes, further corroborating the notion that Rac1 ablation in neurons is neuroprotective. Our results demonstrate that Rac1 plays important roles in the ischemic pathological cascade and that modulation of its levels is of therapeutic interest.
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Affiliation(s)
- Cansu Karabiyik
- i3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal.,Glial Cell Biology, IBMC- Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal.,Department of Neurobiology Research, Institute of Molecular Medicine, University of Southern Denmark, Odense C, Denmark
| | - Rui Fernandes
- i3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal.,HEMS, IBMC-Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
| | - Francisco Rosário Figueiredo
- i3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal.,HEMS, IBMC-Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
| | - Renato Socodato
- i3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal.,Glial Cell Biology, IBMC- Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
| | - Cord Brakebusch
- Biotech Research and Innovation Center, University of Copenhagen, Denmark
| | - Kate Lykke Lambertsen
- Department of Neurobiology Research, Institute of Molecular Medicine, University of Southern Denmark, Odense C, Denmark.,Department of Neurology, Odense University Hospital, Odence C, Denmark.,BRIDGE - Brain Research - Inter-Disciplinary Guided Excellence, Department of Clinical Research, University of Southern Denmark, Odense, Denmark
| | - João Bettencourt Relvas
- i3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal.,Glial Cell Biology, IBMC- Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
| | - Sofia Duque Santos
- i3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal.,Glial Cell Biology, IBMC- Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal.,INEB - Instituto de Engenharia Biomédica, Universidade do Porto, Porto, Portugal
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21
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Interaction between Rho GTPases and 14-3-3 Proteins. Int J Mol Sci 2017; 18:ijms18102148. [PMID: 29036929 PMCID: PMC5666830 DOI: 10.3390/ijms18102148] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Revised: 10/11/2017] [Accepted: 10/13/2017] [Indexed: 01/25/2023] Open
Abstract
The Rho GTPase family accounts for as many as 20 members. Among them, the archetypes RhoA, Rac1, and Cdc42 have been the most well-characterized. Like all members of the small GTPases superfamily, Rho proteins act as molecular switches to control cellular processes by cycling between active, GTP-bound and inactive, GDP-bound states. The 14-3-3 family proteins comprise seven isoforms. They exist as dimers (homo- or hetero-dimer) in cells. They function by binding to Ser/Thr phosphorylated intracellular proteins, which alters the conformation, activity, and subcellular localization of their binding partners. Both 14-3-3 proteins and Rho GTPases regulate cell cytoskeleton remodeling and cell migration, which suggests a possible interaction between the signaling pathways regulated by these two groups of proteins. Indeed, more and more emerging evidence indicates the mutual regulation of these two signaling pathways. There have been many documented reviews of 14-3-3 protein and Rac1 separately, but there is no review regarding the interaction and mutual regulation of these two groups of proteins. Thus, in this article we thoroughly review all the reported interactions between the signaling pathways regulated by 14-3-3 proteins and Rho GTPases (mostly Rac1).
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22
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Gonyo P, Bergom C, Brandt AC, Tsaih SW, Sun Y, Bigley TM, Lorimer EL, Terhune SS, Rui H, Flister MJ, Long RM, Williams CL. SmgGDS is a transient nucleolar protein that protects cells from nucleolar stress and promotes the cell cycle by regulating DREAM complex gene expression. Oncogene 2017; 36:6873-6883. [PMID: 28806394 PMCID: PMC5730474 DOI: 10.1038/onc.2017.280] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Revised: 06/07/2017] [Accepted: 07/03/2017] [Indexed: 12/19/2022]
Abstract
The chaperone protein and guanine nucleotide exchange factor SmgGDS (RAP1GDS1) is a key promoter of cancer cell proliferation and tumorigenesis. SmgGDS undergoes nucleocytoplasmic shuttling, suggesting that it has both cytoplasmic and nuclear functions that promote cancer. Previous studies indicate that SmgGDS binds cytoplasmic small GTPases and promotes their trafficking to the plasma membrane. In contrast, little is known about the functions of SmgGDS in the nucleus, or how these nuclear functions might benefit cancer cells. Here we show unique nuclear localization and regulation of gene transcription pathways by SmgGDS. Strikingly, SmgGDS depletion significantly reduces expression of over 600 gene products that are targets of the DREAM complex, which is a transcription factor complex that regulates expression of proteins controlling the cell cycle. The cell cycle regulators E2F1, MYC, MYBL2 (B-Myb) and FOXM1 are among the DREAM targets that are diminished by SmgGDS depletion. E2F1 is well known to promote G1 cell cycle progression, and the loss of E2F1 in SmgGDS-depleted cells provides an explanation for previous reports that SmgGDS depletion characteristically causes a G1 cell cycle arrest. We show that SmgGDS localizes in nucleoli, and that RNAi-mediated depletion of SmgGDS in cancer cells disrupts nucleolar morphology, signifying nucleolar stress. We show that nucleolar SmgGDS interacts with the RNA polymerase I transcription factor upstream binding factor (UBF). The RNAi-mediated depletion of UBF diminishes nucleolar localization of SmgGDS and promotes proteasome-mediated degradation of SmgGDS, indicating that nucleolar sequestration of SmgGDS by UBF stabilizes SmgGDS protein. The ability of SmgGDS to interact with UBF and localize in the nucleolus is diminished by expressing DiRas1 or DiRas2, which are small GTPases that bind SmgGDS and act as tumor suppressors. Taken together, our results support a novel nuclear role for SmgGDS in protecting malignant cells from nucleolar stress, thus promoting cell cycle progression and tumorigenesis.
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Affiliation(s)
- P Gonyo
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI, USA.,Cancer Center, Medical College of Wisconsin, Milwaukee, WI, USA
| | - C Bergom
- Cancer Center, Medical College of Wisconsin, Milwaukee, WI, USA.,Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - A C Brandt
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI, USA.,Cancer Center, Medical College of Wisconsin, Milwaukee, WI, USA
| | - S-W Tsaih
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Y Sun
- Department of Pathology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - T M Bigley
- Department of Microbiology and Immunology, Medical College of Wisconsin, Milwaukee, WI, USA.,Department of Pediatrics, Washington University in St Louis, St Louis, MO, USA
| | - E L Lorimer
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI, USA.,Cancer Center, Medical College of Wisconsin, Milwaukee, WI, USA
| | - S S Terhune
- Department of Microbiology and Immunology, Medical College of Wisconsin, Milwaukee, WI, USA.,Biotechnology and Bioengineering Center, Medical College of Wisconsin, Milwaukee, WI, USA
| | - H Rui
- Cancer Center, Medical College of Wisconsin, Milwaukee, WI, USA.,Department of Pathology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - M J Flister
- Cancer Center, Medical College of Wisconsin, Milwaukee, WI, USA.,Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, USA.,Human and Molecular Genetics Center, Medical College of Wisconsin, Milwaukee, WI, USA.,Cardiovascular Center, Medical College of Wisconsin, Milwaukee, WI, USA
| | - R M Long
- Department of Microbiology and Immunology, Medical College of Wisconsin, Milwaukee, WI, USA.,Medical College of Wisconsin Central Wisconsin Campus, Wausau, WI, USA
| | - C L Williams
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI, USA.,Cancer Center, Medical College of Wisconsin, Milwaukee, WI, USA.,Cardiovascular Center, Medical College of Wisconsin, Milwaukee, WI, USA
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23
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Shimizu H, Toma-Fukai S, Saijo S, Shimizu N, Kontani K, Katada T, Shimizu T. Structure-based analysis of the guanine nucleotide exchange factor SmgGDS reveals armadillo-repeat motifs and key regions for activity and GTPase binding. J Biol Chem 2017; 292:13441-13448. [PMID: 28630045 PMCID: PMC5555202 DOI: 10.1074/jbc.m117.792556] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2017] [Revised: 06/14/2017] [Indexed: 01/15/2023] Open
Abstract
Small GTPases are molecular switches that have critical biological roles and are controlled by GTPase-activating proteins and guanine nucleotide exchange factors (GEFs). The smg GDP dissociation stimulator (SmgGDS) protein functions as a GEF for the RhoA and RhoC small GTPases. SmgGDS has various regulatory roles, including small GTPase trafficking and localization and as a molecular chaperone, and interacts with many small GTPases possessing polybasic regions. Two SmgGDS splice variants, SmgGDS-558 and SmgGDS-607, differ in GEF activity and binding affinity for RhoA depending on the lipidation state, but the reasons for these differences are unclear. Here we determined the crystal structure of SmgGDS-558, revealing a fold containing tandem copies of armadillo repeats not present in other GEFs. We also observed that SmgGDS harbors distinct positively and negatively charged regions, both of which play critical roles in binding to RhoA and GEF activity. This is the first report demonstrating a relationship between the molecular function and atomic structure of SmgGDS. Our findings indicate that the two SmgGDS isoforms differ in GTPase binding and GEF activity, depending on the lipidation state, thus providing useful information about the cellular functions of SmgGDS in cells.
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Affiliation(s)
- Hikaru Shimizu
- From the Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Sachiko Toma-Fukai
- From the Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Shinya Saijo
- the Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan, and
| | - Nobutaka Shimizu
- the Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan, and
| | - Kenji Kontani
- the Meiji Pharmaceutical University, 2-522-1 Noshio, Kiyose-shi, Tokyo 204-8588, Japan
| | - Toshiaki Katada
- From the Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Toshiyuki Shimizu
- From the Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan,
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24
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Integrin-Dependent Regulation of Small GTPases: Role in Cell Migration. J Indian Inst Sci 2017. [DOI: 10.1007/s41745-016-0010-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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25
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Justilien V, Ali SA, Jamieson L, Yin N, Cox AD, Der CJ, Murray NR, Fields AP. Ect2-Dependent rRNA Synthesis Is Required for KRAS-TRP53-Driven Lung Adenocarcinoma. Cancer Cell 2017; 31:256-269. [PMID: 28110998 PMCID: PMC5310966 DOI: 10.1016/j.ccell.2016.12.010] [Citation(s) in RCA: 94] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Revised: 10/07/2016] [Accepted: 12/21/2016] [Indexed: 11/16/2022]
Abstract
The guanine nucleotide exchange factor (GEF) epithelial cell transforming sequence 2 (Ect2) has been implicated in cancer. However, it is not clear how Ect2 causes transformation and whether Ect2 is necessary for tumorigenesis in vivo. Here, we demonstrate that nuclear Ect2 GEF activity is required for Kras-Trp53 lung tumorigenesis in vivo and that Ect2-mediated transformation requires Ect2-dependent rDNA transcription. Ect2 activates rRNA synthesis by binding the nucleolar transcription factor upstream binding factor 1 (UBF1) on rDNA promoters and recruiting Rac1 and its downstream effector nucleophosmin (NPM) to rDNA. Protein kinase Cι (PKCι)-mediated Ect2 phosphorylation stimulates Ect2-dependent rDNA transcription. Thus, Ect2 regulates rRNA synthesis through a PKCι-Ect2-Rac1-NPM signaling axis that is required for lung tumorigenesis.
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Affiliation(s)
- Verline Justilien
- Department of Cancer Biology, Mayo Clinic Comprehensive Cancer Center, Griffin Cancer Research Building, Room 212, 4500 San Pablo Road, Jacksonville, FL 32224, USA
| | - Syed A Ali
- Department of Cancer Biology, Mayo Clinic Comprehensive Cancer Center, Griffin Cancer Research Building, Room 212, 4500 San Pablo Road, Jacksonville, FL 32224, USA
| | - Lee Jamieson
- Department of Cancer Biology, Mayo Clinic Comprehensive Cancer Center, Griffin Cancer Research Building, Room 212, 4500 San Pablo Road, Jacksonville, FL 32224, USA
| | - Ning Yin
- Department of Cancer Biology, Mayo Clinic Comprehensive Cancer Center, Griffin Cancer Research Building, Room 212, 4500 San Pablo Road, Jacksonville, FL 32224, USA
| | - Adrienne D Cox
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Channing J Der
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Nicole R Murray
- Department of Cancer Biology, Mayo Clinic Comprehensive Cancer Center, Griffin Cancer Research Building, Room 212, 4500 San Pablo Road, Jacksonville, FL 32224, USA
| | - Alan P Fields
- Department of Cancer Biology, Mayo Clinic Comprehensive Cancer Center, Griffin Cancer Research Building, Room 212, 4500 San Pablo Road, Jacksonville, FL 32224, USA.
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26
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Kudo S, Satoh K, Nogi M, Suzuki K, Sunamura S, Omura J, Kikuchi N, Kurosawa R, Satoh T, Minami T, Ikeda S, Miyata S, Shimokawa H. SmgGDS as a Crucial Mediator of the Inhibitory Effects of Statins on Cardiac Hypertrophy and Fibrosis: Novel Mechanism of the Pleiotropic Effects of Statins. Hypertension 2016; 67:878-89. [PMID: 26975711 DOI: 10.1161/hypertensionaha.115.07089] [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: 12/31/2015] [Accepted: 02/19/2016] [Indexed: 01/31/2023]
Abstract
The detailed molecular mechanisms of the pleiotropic effects of statins remain to be fully elucidated. Here, we hypothesized that cardioprotective effects of statins are mediated by small GTP-binding protein GDP dissociation stimulator (SmgGDS). SmgGDS(+/-) and wild-type (WT) mice were treated with continuous infusion of angiotensin II (Ang II) for 2 weeks with and without oral treatment with atorvastatin or pravastatin. At 2 weeks, the extents of Ang II-induced cardiac hypertrophy and fibrosis were comparable between the 2 genotypes. However, statins significantly attenuated cardiomyocyte hypertrophy and fibrosis in WT mice, but not in SmgGDS(+/-) mice. In SmgGDS(+/-) cardiac fibroblasts (CFs), Rac1 expression, extracellular signal-regulated kinases 1/2 activity, Rho-kinase activity, and inflammatory cytokines secretion in response to Ang II were significantly increased when compared with WT CFs. Atorvastatin significantly reduced Rac1 expression and oxidative stress in WT CFs, but not in SmgGDS(+/-) CFs. Furthermore, Bio-plex analysis revealed significant upregulations of inflammatory cytokines/chemokines and growth factors in SmgGDS(+/-) CFs when compared with WT CFs. Importantly, conditioned medium from SmgGDS(+/-) CFs increased B-type natriuretic peptide expression in rat cardiomyocytes to a greater extent than that from WT CFs. Furthermore, atorvastatin significantly increased SmgGDS secretion from mouse CFs. Finally, treatment with recombinant SmgGDS significantly reduced Rac1 expression in SmgGDS(+/-) CFs. These results indicate that both intracellular and extracellular SmgGDS play crucial roles in the inhibitory effects of statins on cardiac hypertrophy and fibrosis, partly through inhibition of Rac1, Rho kinase, and extracellular signal-regulated kinase 1/2 pathways, demonstrating the novel mechanism of the pleiotropic effects of statins.
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Affiliation(s)
- Shun Kudo
- From the Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan
| | - Kimio Satoh
- From the Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan
| | - Masamichi Nogi
- From the Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan
| | - Kota Suzuki
- From the Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan
| | - Shinichiro Sunamura
- From the Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan
| | - Junichi Omura
- From the Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan
| | - Nobuhiro Kikuchi
- From the Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan
| | - Ryo Kurosawa
- From the Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan
| | - Taijyu Satoh
- From the Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan
| | - Tatsuro Minami
- From the Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan
| | - Shohei Ikeda
- From the Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan
| | - Satoshi Miyata
- From the Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan
| | - Hiroaki Shimokawa
- From the Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan.
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27
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Bergom C, Hauser AD, Rymaszewski A, Gonyo P, Prokop JW, Jennings BC, Lawton AJ, Frei A, Lorimer EL, Aguilera-Barrantes I, Mackinnon AC, Noon K, Fierke CA, Williams CL. The Tumor-suppressive Small GTPase DiRas1 Binds the Noncanonical Guanine Nucleotide Exchange Factor SmgGDS and Antagonizes SmgGDS Interactions with Oncogenic Small GTPases. J Biol Chem 2016; 291:6534-45. [PMID: 26814130 DOI: 10.1074/jbc.m115.696831] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Indexed: 11/06/2022] Open
Abstract
The small GTPase DiRas1 has tumor-suppressive activities, unlike the oncogenic properties more common to small GTPases such as K-Ras and RhoA. Although DiRas1 has been found to be a tumor suppressor in gliomas and esophageal squamous cell carcinomas, the mechanisms by which it inhibits malignant phenotypes have not been fully determined. In this study, we demonstrate that DiRas1 binds to SmgGDS, a protein that promotes the activation of several oncogenic GTPases. In silico docking studies predict that DiRas1 binds to SmgGDS in a manner similar to other small GTPases. SmgGDS is a guanine nucleotide exchange factor for RhoA, but we report here that SmgGDS does not mediate GDP/GTP exchange on DiRas1. Intriguingly, DiRas1 acts similarly to a dominant-negative small GTPase, binding to SmgGDS and inhibiting SmgGDS binding to other small GTPases, including K-Ras4B, RhoA, and Rap1A. DiRas1 is expressed in normal breast tissue, but its expression is decreased in most breast cancers, similar to its family member DiRas3 (ARHI). DiRas1 inhibits RhoA- and SmgGDS-mediated NF-κB transcriptional activity in HEK293T cells. We also report that DiRas1 suppresses basal NF-κB activation in breast cancer and glioblastoma cell lines. Taken together, our data support a model in which DiRas1 expression inhibits malignant features of cancers in part by nonproductively binding to SmgGDS and inhibiting the binding of other small GTPases to SmgGDS.
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Affiliation(s)
- Carmen Bergom
- From the Cancer Center, the Departments of Radiation Oncology,
| | - Andrew D Hauser
- From the Cancer Center, the Departments of Radiation Oncology, Pharmacology and Toxicology, and the Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, New York 10016, and
| | | | - Patrick Gonyo
- From the Cancer Center, Pharmacology and Toxicology, and
| | | | | | - Alexis J Lawton
- the Department of Chemistry, Biochemistry Undergraduate Program, and
| | - Anne Frei
- From the Cancer Center, the Departments of Radiation Oncology
| | | | | | | | - Kathleen Noon
- the Mass Spectroscopy Facility for Proteomics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Carol A Fierke
- the Department of Chemistry, Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109
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28
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Jamieson C, Lui C, Brocardo MG, Martino-Echarri E, Henderson BR. Rac1 augments Wnt signaling by stimulating β-catenin-lymphoid enhancer factor-1 complex assembly independent of β-catenin nuclear import. J Cell Sci 2015; 128:3933-46. [PMID: 26403202 PMCID: PMC4657330 DOI: 10.1242/jcs.167742] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Accepted: 09/17/2015] [Indexed: 12/29/2022] Open
Abstract
β-Catenin transduces the Wnt signaling pathway and its nuclear accumulation leads to gene transactivation and cancer. Rac1 GTPase is known to stimulate β-catenin-dependent transcription of Wnt target genes and we confirmed this activity. Here we tested the recent hypothesis that Rac1 augments Wnt signaling by enhancing β-catenin nuclear import; however, we found that silencing/inhibition or up-regulation of Rac1 had no influence on nuclear accumulation of β-catenin. To better define the role of Rac1, we employed proximity ligation assays (PLA) and discovered that a significant pool of Rac1-β-catenin protein complexes redistribute from the plasma membrane to the nucleus upon Wnt or Rac1 activation. More importantly, active Rac1 was shown to stimulate the formation of nuclear β-catenin-lymphoid enhancer factor 1 (LEF-1) complexes. This regulation required Rac1-dependent phosphorylation of β-catenin at specific serines, which when mutated (S191A and S605A) reduced β-catenin binding to LEF-1 by up to 50%, as revealed by PLA and immunoprecipitation experiments. We propose that Rac1-mediated phosphorylation of β-catenin stimulates Wnt-dependent gene transactivation by enhancing β-catenin-LEF-1 complex assembly, providing new insight into the mechanism of cross-talk between Rac1 and canonical Wnt/β-catenin signaling.
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Affiliation(s)
- Cara Jamieson
- Center for Cancer Research, The Westmead Millennium Institute for Medical Research, The University of Sydney, Westmead, New South Wales 2145, Australia
| | - Christina Lui
- Center for Cancer Research, The Westmead Millennium Institute for Medical Research, The University of Sydney, Westmead, New South Wales 2145, Australia
| | - Mariana G Brocardo
- Center for Cancer Research, The Westmead Millennium Institute for Medical Research, The University of Sydney, Westmead, New South Wales 2145, Australia
| | - Estefania Martino-Echarri
- Center for Cancer Research, The Westmead Millennium Institute for Medical Research, The University of Sydney, Westmead, New South Wales 2145, Australia
| | - Beric R Henderson
- Center for Cancer Research, The Westmead Millennium Institute for Medical Research, The University of Sydney, Westmead, New South Wales 2145, Australia
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29
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Hong JY, Oh IH, McCrea PD. Phosphorylation and isoform use in p120-catenin during development and tumorigenesis. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1863:102-14. [PMID: 26477567 DOI: 10.1016/j.bbamcr.2015.10.008] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2015] [Revised: 10/12/2015] [Accepted: 10/13/2015] [Indexed: 12/12/2022]
Abstract
P120-catenin is essential to vertebrate development, modulating cadherin and small-GTPase functions, and growing evidence points also to roles in the nucleus. A complexity in addressing p120-catenin's functions is its many isoforms, including optional splicing events, alternative points of translational initiation, and secondary modifications. In this review, we focus upon how choices in the initiation of protein translation, or the earlier splicing of the RNA transcript, relates to primary sequences that harbor established or putative regulatory phosphorylation sites. While certain p120 phosphorylation events arise via known kinases/phosphatases and have defined outcomes, in most cases the functional consequences are still to be established. In this review, we provide examples of p120-isoforms as they relate to phosphorylation events, and thereby to isoform dependent protein-protein associations and downstream functions. We also provide a view of upstream pathways that determine p120's phosphorylation state, and that have an impact upon development and disease. Because other members of the p120 subfamily undergo similar processing and phosphorylation, as well as related catenins of the plakophilin subfamily, what is learned regarding p120 will by extension have wide relevance in vertebrates.
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Affiliation(s)
- Ji Yeon Hong
- Division of Cardiology, Department of Medicine, Severance Biomedical Science Institute, Yonsei University College of Medicine, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-752, Republic of Korea.
| | - Il-Hoan Oh
- The Catholic University of Korea, Catholic High Performance Cell Therapy Center, 505 Banpo-dong, Seocho-Ku, Seoul 137-701, Republic of Korea
| | - Pierre D McCrea
- Department of Genetics, University of Texas MD Anderson Cancer Center, University of Texas Graduate School of Biomedical Science, Houston, TX 77030, USA.
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30
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Navarro-Lérida I, Pellinen T, Sanchez SA, Guadamillas MC, Wang Y, Mirtti T, Calvo E, Del Pozo MA. Rac1 nucleocytoplasmic shuttling drives nuclear shape changes and tumor invasion. Dev Cell 2015; 32:318-34. [PMID: 25640224 DOI: 10.1016/j.devcel.2014.12.019] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2013] [Revised: 08/06/2014] [Accepted: 12/19/2014] [Indexed: 11/26/2022]
Abstract
Nuclear membrane microdomains are proposed to act as platforms for regulation of nuclear function, but little is known about the mechanisms controlling their formation. Organization of the plasma membrane is regulated by actin polymerization, and the existence of an actin pool in the nucleus suggests that a similar mechanism might operate here. We show that nuclear membrane organization and morphology are regulated by the nuclear level of active Rac1 through actin polymerization-dependent mechanisms. Rac1 nuclear export is mediated by two internal nuclear export signals and through its interaction with nucleophosmin-1 (B23), which acts as a Rac1 chaperone inside the nucleus. Rac1 nuclear accumulation alters the balance between cytosolic Rac1 and Rho, increasing RhoA signaling in the cytoplasm and promoting a highly invasive phenotype. Nuclear Rac1 shuttling is a finely tuned mechanism for controlling nuclear shape and organization and cell invasiveness.
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Affiliation(s)
- Inmaculada Navarro-Lérida
- Integrin Signaling Laboratory, Department of Vascular Biology and Inflammation, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029 Madrid, Spain
| | - Teijo Pellinen
- Integrin Signaling Laboratory, Department of Vascular Biology and Inflammation, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029 Madrid, Spain; Institute for Molecular Medicine Finland (FIMM), University of Helsinki, Tukholmankatu 8, P.O. Box 20, 00014 Helsinki, Finland
| | - Susana A Sanchez
- Microscopy and Dynamic Imaging Unit, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029 Madrid, Spain; Facultad de Ciencias Químicas, Universidad de Concepción, 4070371 Concepción, Chile
| | - Marta C Guadamillas
- Integrin Signaling Laboratory, Department of Vascular Biology and Inflammation, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029 Madrid, Spain
| | - Yinhai Wang
- Institute for Molecular Medicine Finland (FIMM), University of Helsinki, Tukholmankatu 8, P.O. Box 20, 00014 Helsinki, Finland
| | - Tuomas Mirtti
- Institute for Molecular Medicine Finland (FIMM), University of Helsinki, Tukholmankatu 8, P.O. Box 20, 00014 Helsinki, Finland; HUSLAB, Department of Pathology, Haartman Institute, Helsinki University Central Hospital, Haartmaninkatu 3 C, P.O. Box 400, 00029 HUS Helsinki, Finland
| | - Enrique Calvo
- Proteomics Unit, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029 Madrid, Spain
| | - Miguel A Del Pozo
- Integrin Signaling Laboratory, Department of Vascular Biology and Inflammation, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029 Madrid, Spain.
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31
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Cheung LWT, Yu S, Zhang D, Li J, Ng PKS, Panupinthu N, Mitra S, Ju Z, Yu Q, Liang H, Hawke DH, Lu Y, Broaddus RR, Mills GB. Naturally occurring neomorphic PIK3R1 mutations activate the MAPK pathway, dictating therapeutic response to MAPK pathway inhibitors. Cancer Cell 2014; 26:479-94. [PMID: 25284480 PMCID: PMC4198486 DOI: 10.1016/j.ccell.2014.08.017] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Revised: 06/05/2014] [Accepted: 08/26/2014] [Indexed: 12/17/2022]
Abstract
PIK3R1 (p85α regulatory subunit of PI3K) is frequently mutated across cancer lineages. Herein, we demonstrate that the most common recurrent PIK3R1 mutation PIK3R1(R348∗) and a nearby mutation PIK3R1(L370fs), in contrast to wild-type and mutations in other regions of PIK3R1, confers an unexpected sensitivity to MEK and JNK inhibitors in vitro and in vivo. Consistent with the response to inhibitors, PIK3R1(R348∗) and PIK3R1(L370fs) unexpectedly increase JNK and ERK phosphorylation. Surprisingly, p85α R348(∗) and L370fs localize to the nucleus where the mutants provide a scaffold for multiple JNK pathway components facilitating nuclear JNK pathway activation. Our findings uncover an unexpected neomorphic role for PIK3R1(R348∗) and neighboring truncation mutations in cellular signaling, providing a rationale for therapeutic targeting of these mutant tumors.
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Affiliation(s)
- Lydia W T Cheung
- Department of Systems Biology, University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA.
| | - Shuangxing Yu
- Department of Systems Biology, University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Dong Zhang
- Department of Systems Biology, University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Jie Li
- Department of Systems Biology, University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Patrick K S Ng
- Department of Systems Biology, University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Nattapon Panupinthu
- Department of Systems Biology, University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA; Department of Physiology, Faculty of Science, Mahidol University, Bangkok 10400, Thailand
| | - Shreya Mitra
- Department of Systems Biology, University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Zhenlin Ju
- Department of Systems Biology, University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA; Department of Bioinformatics and Computational Biology, University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Qinghua Yu
- Department of Systems Biology, University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Han Liang
- Department of Bioinformatics and Computational Biology, University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - David H Hawke
- Department of Systems Biology, University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA; Department of Pathology, University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Yiling Lu
- Department of Systems Biology, University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Russell R Broaddus
- Department of Pathology, University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Gordon B Mills
- Department of Systems Biology, University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
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32
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Kim EG, Shin EY. Nuclear Rac1 regulates the bFGF-induced neurite outgrowth in PC12 cells. BMB Rep 2014; 46:617-22. [PMID: 24195795 PMCID: PMC4133861 DOI: 10.5483/bmbrep.2013.46.12.114] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2013] [Revised: 06/13/2013] [Accepted: 07/02/2013] [Indexed: 01/05/2023] Open
Abstract
Rac1 plays a key role in neurite outgrowth via reorganization of the actin cytoskeleton. The molecular mechanisms underlying Rac1-mediated actin dynamics in the cytosol and plasma membrane have been intensively studied, but the nuclear function of Rac1 in neurite outgrowth has not yet been addressed. Using subcellular fractionation and immunocytochemistry, we sought to explore the role of nuclear Rac1 in neurite outgrowth. bFGF, a strong agonist for neurite outgrowth in PC12 cells, stimulated the nuclear accumulation of an active form of Rac1. Rac1-PBR (Q) mutant, in which six basic residues in the polybasic region at the C-terminus were replaced by glutamine, didn’t accumulate in the nucleus. In comparison with control cells, cells expressing this mutant form of Rac1 displayed a marked defect in extending neurites that was concomitant with reduced expression of MAP2 and MEK-1. These results suggest that Rac1 translocation to the nucleus functionally correlates with bFGF-induced neurite outgrowth. [BMB Reports 2013; 46(12): 617-622]
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Affiliation(s)
| | - Eun-Young Shin
- Department of Biochemistry, College of Medicine and Medical Research Institute, Chungbuk National University, Cheongju 361-763, Korea
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33
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Rac1 as a potential therapeutic target for chemo-radioresistant head and neck squamous cell carcinomas (HNSCC). Br J Cancer 2014; 110:2677-87. [PMID: 24786604 PMCID: PMC4037830 DOI: 10.1038/bjc.2014.221] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Revised: 02/10/2014] [Accepted: 03/27/2014] [Indexed: 01/25/2023] Open
Abstract
BACKGROUND In order to improve therapy for HNSCC patients, novel methods to predict and combat local and/or distant tumour relapses are urgently needed. This study has been dedicated to the hypothesis that Rac1, a Rho GTPase, is implicated in HNSCC insensitivity to chemo-radiotherapy resulting in tumour recurrence development. METHODS Parental and radiation-resistant (IRR) HNSCC cells were used to support this hypothesis. All cells were investigated for their sensitivity to ionising radiation and cisplatin, Rac1 activity, its intracellular expression and subcellular localisation. Additionally, tumour tissues obtained from 60 HNSCC patients showing different therapy response were evaluated for intratumoral Rac1 expression. RESULTS Radiation-resistant IRR cells also revealed resistance to cisplatin accompanied by increased expression, activity and trend towards nuclear translocation of Rac1 protein. Chemical inhibition of Rac1 expression and activity resulted in significant improvement of HNSCC sensitivity to ionising radiation and cisplatin. Preclinical results were confirmed in clinical samples. Although Rac1 was poorly presented in normal mucosa, tumour tissues revealed increased Rac1 expression. The most pronounced Rac1 presence was observed in HNSCC patients with poor early or late responses to chemo-radiotherapy. Tissues taken at recurrence were characterised not only by enhanced Rac1 expression but also increased nuclear Rac1 content. CONCLUSIONS Increased expression, activity and subcellular localisation of Rac1 could be associated with lower early response rate and higher risk of tumour recurrences in HNSCC patients and warrants further validation in larger independent studies. Inhibition of Rac1 activity can be useful in overcoming treatment resistance and could be proposed for HNSCC patients with primary or secondary chemo-radioresistance.
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34
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Schuld NJ, Vervacke JS, Lorimer EL, Simon NC, Hauser AD, Barbieri JT, Distefano MD, Williams CL. The chaperone protein SmgGDS interacts with small GTPases entering the prenylation pathway by recognizing the last amino acid in the CAAX motif. J Biol Chem 2014; 289:6862-6876. [PMID: 24415755 PMCID: PMC3945348 DOI: 10.1074/jbc.m113.527192] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2013] [Revised: 01/09/2014] [Indexed: 12/31/2022] Open
Abstract
Ras family small GTPases localize at the plasma membrane, where they can activate oncogenic signaling pathways. Understanding the mechanisms that promote membrane localization of GTPases will aid development of new therapies to inhibit oncogenic signaling. We previously reported that SmgGDS splice variants promote prenylation and trafficking of GTPases containing a C-terminal polybasic region and demonstrated that SmgGDS-607 interacts with nonprenylated GTPases, whereas SmgGDS-558 interacts with prenylated GTPases in cells. The mechanism that SmgGDS-607 and SmgGDS-558 use to differentiate between prenylated and nonprenylated GTPases has not been characterized. Here, we provide evidence that SmgGDS-607 associates with GTPases through recognition of the last amino acid in the CAAX motif. We show that SmgGDS-607 forms more stable complexes in cells with nonprenylated GTPases that will become geranylgeranylated than with nonprenylated GTPases that will become farnesylated. These binding relationships similarly occur with nonprenylated SAAX mutants. Intriguingly, farnesyltransferase inhibitors increase the binding of WT K-Ras to SmgGDS-607, indicating that the pharmacological shunting of K-Ras into the geranylgeranylation pathway promotes K-Ras association with SmgGDS-607. Using recombinant proteins and prenylated peptides corresponding to the C-terminal sequences of K-Ras and Rap1B, we found that both SmgGDS-607 and SmgGDS-558 directly bind the GTPase C-terminal region, but the specificity of the SmgGDS splice variants for prenylated versus nonprenylated GTPases is diminished in vitro. Finally, we present structural homology models and data from functional prediction software to define both similar and unique features of SmgGDS-607 when compared with SmgGDS-558.
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Affiliation(s)
- Nathan J Schuld
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Jeffrey S Vervacke
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55414
| | - Ellen L Lorimer
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Nathan C Simon
- Department of Microbiology, Immunology, and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Andrew D Hauser
- Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Joseph T Barbieri
- Department of Microbiology, Immunology, and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Mark D Distefano
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55414
| | - Carol L Williams
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226.
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Rajakylä EK, Vartiainen MK. Rho, nuclear actin, and actin-binding proteins in the regulation of transcription and gene expression. Small GTPases 2014; 5:e27539. [PMID: 24603113 DOI: 10.4161/sgtp.27539] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Actin cytoskeleton is one of the main targets of Rho GTPases, which act as molecular switches on many signaling pathways. During the past decade, actin has emerged as an important regulator of gene expression. Nuclear actin plays a key role in transcription, chromatin remodeling, and pre-mRNA processing. In addition, the "status" of the actin cytoskeleton is used as a signaling intermediate by at least the MKL1-SRF and Hippo-pathways, which culminate in the transcriptional regulation of cytoskeletal and growth-promoting genes, respectively. Rho GTPases may therefore regulate gene expression by controlling either cytoplasmic or nuclear actin dynamics. Although the regulation of nuclear actin polymerization is still poorly understood, many actin-binding proteins, which are downstream effectors of Rho, are found in the nuclear compartment. In this review, we discuss the possible mechanisms and key proteins that may mediate the transcriptional regulation by Rho GTPases through actin.
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Affiliation(s)
- Eeva Kaisa Rajakylä
- Program in Cell and Molecular Biology; Institute of Biotechnology; University of Helsinki; Helsinki, Finland
| | - Maria K Vartiainen
- Program in Cell and Molecular Biology; Institute of Biotechnology; University of Helsinki; Helsinki, Finland
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Dierkes R, Warnking K, Liedmann S, Seyer R, Ludwig S, Ehrhardt C. The Rac1 inhibitor NSC23766 exerts anti-influenza virus properties by affecting the viral polymerase complex activity. PLoS One 2014; 9:e88520. [PMID: 24523909 PMCID: PMC3921225 DOI: 10.1371/journal.pone.0088520] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Accepted: 01/07/2014] [Indexed: 12/31/2022] Open
Abstract
The frequent emergence of new influenza viruses in the human population underlines the urgent need for antiviral therapeutics in addition to the preventative vaccination against the seasonal flu. To circumvent the development of resistance, recent antiviral approaches target cellular proteins needed by the virus for efficient replication. We investigated the contribution of the small GTPase Rac1 to the replication of influenza viruses. Inhibition of Rac1 by NSC23766 resulted in impaired replication of a wide variety of influenza viruses, including a human virus strain of the pandemic from 2009 as well as highly pathogenic avian virus strains. Furthermore, we identified a crucial role of Rac1 for the activity of the viral polymerase complex. The antiviral potential of NSC23766 was confirmed in mouse experiments, identifying Rac1 as a new cellular target for therapeutic treatment of influenza virus infections.
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Affiliation(s)
- Rüdiger Dierkes
- Institute of Molecular Virology (IMV), Centre of Molecular Virology (ZMBE), Westfälische Wilhelms-University, Münster, Germany
| | - Kathrin Warnking
- Institute of Molecular Virology (IMV), Centre of Molecular Virology (ZMBE), Westfälische Wilhelms-University, Münster, Germany
| | - Swantje Liedmann
- Institute of Molecular Virology (IMV), Centre of Molecular Virology (ZMBE), Westfälische Wilhelms-University, Münster, Germany
| | - Roman Seyer
- Institute of Molecular Virology (IMV), Centre of Molecular Virology (ZMBE), Westfälische Wilhelms-University, Münster, Germany
| | - Stephan Ludwig
- Institute of Molecular Virology (IMV), Centre of Molecular Virology (ZMBE), Westfälische Wilhelms-University, Münster, Germany
| | - Christina Ehrhardt
- Institute of Molecular Virology (IMV), Centre of Molecular Virology (ZMBE), Westfälische Wilhelms-University, Münster, Germany
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Huff LP, Decristo MJ, Trembath D, Kuan PF, Yim M, Liu J, Cook DR, Miller CR, Der CJ, Cox AD. The Role of Ect2 Nuclear RhoGEF Activity in Ovarian Cancer Cell Transformation. Genes Cancer 2014; 4:460-75. [PMID: 24386507 DOI: 10.1177/1947601913514851] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Accepted: 11/07/2013] [Indexed: 11/15/2022] Open
Abstract
Ect2, a Rho guanine nucleotide exchange factor (RhoGEF), is atypical among RhoGEFs in its predominantly nuclear localization in interphase cells. One current model suggests that Ect2 mislocalization drives cellular transformation by promoting aberrant activation of cytoplasmic Rho family GTPase substrates. However, in ovarian cancers, where Ect2 is both amplified and overexpressed at the mRNA level, we observed that the protein is highly expressed and predominantly nuclear and that nuclear but not cytoplasmic Ect2 increases with advanced disease. Knockdown of Ect2 in ovarian cancer cell lines impaired their anchorage-independent growth without affecting their growth on plastic. Restoration of Ect2 expression rescued the anchorage-independent growth defect, but not if either the DH catalytic domain or the nuclear localization sequences of Ect2 were mutated. These results suggested a novel mechanism whereby Ect2 could drive transformation in ovarian cancer cells by acting as a RhoGEF specifically within the nucleus. Interestingly, Ect2 had an intrinsically distinct GTPase specificity profile in the nucleus versus the cytoplasm. Nuclear Ect2 bound preferentially to Rac1, while cytoplasmic Ect2 bound to RhoA but not Rac. Consistent with nuclear activation of endogenous Rac, Ect2 overexpression was sufficient to recruit Rac effectors to the nucleus, a process that required a functional Ect2 catalytic domain. Furthermore, expression of active nuclearly targeted Rac1 rescued the defect in transformed growth caused by Ect2 knockdown. Our work suggests a novel mechanism of Ect2-driven transformation, identifies subcellular localization as a regulator of GEF specificity, and implicates activation of nuclear Rac1 in cellular transformation.
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Affiliation(s)
- Lauren P Huff
- Department of Pharmacology, University of North Carolina, Chapel Hill, NC, USA
| | - Molly J Decristo
- Department of Biology, University of North Carolina, Chapel Hill, NC, USA
| | - Dimitri Trembath
- Department of Pathology & Laboratory Medicine, University of North Carolina, Chapel Hill, NC, USA
| | - Pei Fen Kuan
- Department of Biostatistics, University of North Carolina, Chapel Hill, NC, USA
| | - Margaret Yim
- Department of Molecular Biophysics & Biochemistry, Yale University, New Haven, CT, USA
| | - Jinsong Liu
- Department of Pathology, MD Anderson Cancer Center, Houston, TX, USA
| | - Danielle R Cook
- School of Pharmacy, University of North Carolina, Chapel Hill, NC, USA
| | - C Ryan Miller
- Department of Pathology & Laboratory Medicine, University of North Carolina, Chapel Hill, NC, USA ; Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC, USA
| | - Channing J Der
- Department of Pharmacology, University of North Carolina, Chapel Hill, NC, USA ; Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC, USA
| | - Adrienne D Cox
- Department of Pharmacology, University of North Carolina, Chapel Hill, NC, USA ; Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC, USA ; Department of Radiation Oncology, University of North Carolina, Chapel Hill, NC, USA
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38
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Bachmann VA, Bister K, Stefan E. Interplay of PKA and Rac: fine-tuning of Rac localization and signaling. Small GTPases 2013; 4:247-51. [PMID: 24322054 PMCID: PMC4011821 DOI: 10.4161/sgtp.27281] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Cellular membrane receptors sense environmental changes and relay the reshaped signal through spatially and temporally organized protein-protein interactions (PPI). Many of such PPI are transient and occur in a certain cell-dependent context. Molecular switches such as kinases and GTPases are engaged in versatile PPI. Recently, we have identified dynamic interaction and reciprocal regulation of cAMP-dependent protein kinase A (PKA) and Rho-GTPase Rac signaling. We demonstrated that GTP-activated Rac acts as a dual kinase-tuning scaffold for p21-activated kinase (PAK) and PKA activities. We showed that receptor-triggered PKA trans-phosphorylation of GTP-Rac-organized PAK contributes to elevations of nuclear Erk1/2 signaling and proliferation. We discuss these recent observations and we provide additional insights how the cAMP-PKA axis might also participate in the regulation of Rac localization.
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Affiliation(s)
- Verena A Bachmann
- Institute of Biochemistry; University of Innsbruck; Innsbruck, Austria
| | - Klaus Bister
- Institute of Biochemistry; University of Innsbruck; Innsbruck, Austria
| | - Eduard Stefan
- Institute of Biochemistry; University of Innsbruck; Innsbruck, Austria
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Hauser AD, Bergom C, Schuld NJ, Chen X, Lorimer EL, Huang J, Mackinnon AC, Williams CL. The SmgGDS splice variant SmgGDS-558 is a key promoter of tumor growth and RhoA signaling in breast cancer. Mol Cancer Res 2013; 12:130-42. [PMID: 24197117 DOI: 10.1158/1541-7786.mcr-13-0362] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
UNLABELLED Breast cancer malignancy is promoted by the small GTPases RhoA and RhoC. SmgGDS is a guanine nucleotide exchange factor that activates RhoA and RhoC in vitro. We previously reported that two splice variants of SmgGDS, SmgGDS-607, and SmgGDS-558, have different characteristics in binding and transport of small GTPases. To define the role of SmgGDS in breast cancer, we tested the expression of SmgGDS in breast tumors, and the role of each splice variant in proliferation, tumor growth, Rho activation, and NF-κB transcriptional activity in breast cancer cells. We show upregulated SmgGDS protein expression in breast cancer samples compared with normal breast tissue. In addition, Kaplan-Meier survival curves indicated that patients with high SmgGDS expression in their tumors had worse clinical outcomes. Knockdown of SmgGDS-558, but not SmgGDS-607, in breast cancer cells decreased proliferation, in vivo tumor growth, and RhoA activity. Furthermore, we found that SmgGDS promoted a Rho-dependent activation of the transcription factor NF-κB, which provides a potential mechanism to define how SmgGDS-mediated activation of RhoA promotes breast cancer. This study demonstrates that elevated SmgGDS expression in breast tumors correlates with poor survival, and that SmgGDS-558 plays a functional role in breast cancer malignancy. Taken together, these findings define SmgGDS-558 as a unique promoter of RhoA and NF-κB activity and a novel therapeutic target in breast cancer. IMPLICATIONS This study defines a new mechanism to regulate the activities of RhoA and NF-κB in breast cancer cells, and identifies SmgGDS-558 as a novel promoter of breast cancer malignancy.
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Affiliation(s)
- Andrew D Hauser
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226.
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40
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Chahdi A, Raufman JP. The Cdc42/Rac nucleotide exchange factor protein β1Pix (Pak-interacting exchange factor) modulates β-catenin transcriptional activity in colon cancer cells: evidence for direct interaction of β1PIX with β-catenin. J Biol Chem 2013; 288:34019-34029. [PMID: 24129564 DOI: 10.1074/jbc.m113.480103] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Wnt/β-catenin signaling is highly regulated and critical for intestinal epithelial development and repair; aberrant β-catenin signaling is strongly associated with colon cancer. The small GTPase Rac1 regulates β-catenin nuclear translocation and signaling. Here we tested the hypothesis that β1Pix, a Cdc42/Rac guanine nucleotide exchange factor (GEF), regulates β-catenin-dependent transcriptional activity and cell function. We report the novel observations that β1Pix binds directly to β-catenin, an action requiring both the β1Pix DH and dimerization domains but not β1Pix GEF activity. In human colon cancer cells, activation of β-catenin signaling with LiCl decreased β1Pix/β-catenin association in the cytosol and increased nuclear binding of β-catenin to β1Pix. Nuclear association of β1Pix and β-catenin was independent of Rac1 expression and activation; down- and up-regulating Rac1 expression levels did not alter nuclear β1Pix/β-catenin association. Ectopic β1Pix expression enhanced LiCl-induced β-catenin transcriptional activity. Conversely, siRNA knockdown of β1Pix attenuated both LiCl-induced β-catenin transcriptional activity and colon cancer cell proliferation. Ectopic expression of β1Pix stimulated β-catenin transcriptional activity, whereas β1PixΔ(602-611), which is unable to bind β-catenin, had no effect. Altogether, these findings suggest that β1Pix functions as a transcriptional regulator of β-catenin signaling through direct interaction with β-catenin, an action that may be functionally relevant to colon cancer biology.
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Affiliation(s)
- Ahmed Chahdi
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland 21201-1595
| | - Jean-Pierre Raufman
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland 21201-1595; Marlene and Stewart Greenebaum Cancer Center, University of Maryland School of Medicine, Baltimore, Maryland 21201-1595; Veterans Affairs Maryland Health Care System, Baltimore, Maryland 21201-1595.
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41
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Phosphorylation of Rac1 T108 by extracellular signal-regulated kinase in response to epidermal growth factor: a novel mechanism to regulate Rac1 function. Mol Cell Biol 2013; 33:4538-51. [PMID: 24043306 DOI: 10.1128/mcb.00822-13] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Accumulating evidence has implicated Rho GTPases, including Rac1, in many aspects of cancer development. Recent findings suggest that phosphorylation might further contribute to the tight regulation of Rho GTPases. Interestingly, sequence analysis of Rac1 shows that Rac1 T108 within the (106)PNTP(109) motif is likely an extracellular signal-regulated kinase (ERK) phosphorylation site and that Rac1 also has an ERK docking site, (183)KKRKRKCLLL(192) (D site), at the C terminus. Indeed, we show here that both transfected and endogenous Rac1 interacts with ERK and that this interaction is mediated by its D site. Green fluorescent protein (GFP)-Rac1 is threonine (T) phosphorylated in response to epidermal growth factor (EGF), and EGF-induced Rac1 threonine phosphorylation is dependent on the activation of ERK. Moreover, mutant Rac1 with the mutation of T108 to alanine (A) is not threonine phosphorylated in response to EGF. In vitro ERK kinase assay further shows that pure active ERK phosphorylates purified Rac1 but not mutant Rac1 T108A. We also show that Rac1 T108 phosphorylation decreases Rac1 activity, partially due to inhibiting its interaction with phospholipase C-γ1 (PLC-γ1). T108 phosphorylation targets Rac1 to the nucleus, which isolates Rac1 from other guanine nucleotide exchange factors (GEFs) and hinders Rac1's role in cell migration. We conclude that Rac1 T108 is phosphorylated by ERK in response to EGF, which plays an important role in regulating Rac1.
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42
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Johnson MA, Sharma M, Mok MTS, Henderson BR. Stimulation of in vivo nuclear transport dynamics of actin and its co-factors IQGAP1 and Rac1 in response to DNA replication stress. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1833:2334-47. [PMID: 23770048 DOI: 10.1016/j.bbamcr.2013.06.002] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2012] [Revised: 05/31/2013] [Accepted: 06/04/2013] [Indexed: 10/26/2022]
Abstract
Actin, a constituent of the cytoskeleton, is now recognized to function in the nucleus in gene transcription, chromatin remodeling and DNA replication/repair. Actin shuttles in and out of the nucleus through the action of transport receptors importin-9 and exportin-6. Here we have addressed the impact of cell cycle progression and DNA replication stress on actin nuclear localization, through study of actin dynamics in living cells. First, we showed that thymidine-induced G1/S phase cell cycle arrest increased the nuclear levels of actin and of two factors that stimulate actin polymerization: IQGAP1 and Rac1 GTPase. When cells were exposed to hydroxyurea to induce DNA replication stress, the nuclear localization of actin and its regulators was further enhanced. We employed live cell photobleaching assays and discovered that in response to DNA replication stress, GFP-actin nuclear import and export rates increased by up to 250%. The rate of import was twice as fast as export, accounting for actin nuclear accumulation. The faster shuttling dynamics correlated with reduced cellular retention of actin, and our data implicate actin polymerization in the stress-dependent uptake of nuclear actin. Furthermore, DNA replication stress induced a nuclear shift in IQGAP1 and Rac1 with enhanced import dynamics. Proximity ligation assays revealed that IQGAP1 associates in the nucleus with actin and Rac1, and formation of these complexes increased after hydroxyurea treatment. We propose that the replication stress checkpoint triggers co-ordinated nuclear entry and trafficking of actin, and of factors that regulate actin polymerization.
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Affiliation(s)
- Michael A Johnson
- Westmead Institute for Cancer Research, The University of Sydney, Westmead, Australia
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43
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Ntantie E, Gonyo P, Lorimer EL, Hauser AD, Schuld N, McAllister D, Kalyanaraman B, Dwinell MB, Auchampach JA, Williams CL. An adenosine-mediated signaling pathway suppresses prenylation of the GTPase Rap1B and promotes cell scattering. Sci Signal 2013; 6:ra39. [PMID: 23716716 DOI: 10.1126/scisignal.2003374] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
During metastasis, cancer cells acquire the ability to dissociate from each other and migrate, which is recapitulated in vitro as cell scattering. The small guanosine triphosphatase (GTPase) Rap1 opposes cell scattering by promoting cell-cell adhesion, a function that requires its prenylation, or posttranslational modification with a carboxyl-terminal isoprenoid moiety, to enable its localization at cell membranes. Thus, signaling cascades that regulate the prenylation of Rap1 offer a mechanism to control the membrane localization of Rap1. We identified a signaling cascade initiated by adenosine A2B receptors that suppressed the prenylation of Rap1B through phosphorylation of Rap1B, which decreased its interaction with the chaperone protein SmgGDS (small GTPase guanosine diphosphate dissociation stimulator). These events promoted the cytosolic and nuclear accumulation of nonprenylated Rap1B and diminished cell-cell adhesion, resulting in cell scattering. We found that nonprenylated Rap1 was more abundant in mammary tumors than in normal mammary tissue in rats and that activation of adenosine receptors delayed Rap1B prenylation in breast, lung, and pancreatic cancer cell lines. Our findings support a model in which high concentrations of extracellular adenosine, such as those that arise in the tumor microenvironment, can chronically activate A2B receptors to suppress Rap1B prenylation and signaling at the cell membrane, resulting in reduced cell-cell contact and promoting cell scattering. Inhibiting A2B receptors may be an effective method to prevent metastasis.
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Affiliation(s)
- Elizabeth Ntantie
- 1Department of Pharmacology and Toxicology, Cancer Center, and Cardiovascular Center, Medical College of Wisconsin, Milwaukee, WI 53226, USA
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44
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Looking beyond the Wnt pathway for the deep nature of β-catenin. EMBO Rep 2013; 14:422-33. [PMID: 23598517 DOI: 10.1038/embor.2013.45] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Accepted: 03/22/2013] [Indexed: 02/06/2023] Open
Abstract
After two decades of stardom, one would think that β-catenin has revealed all of its most intimate details. Yet the essence of its duality has remained mysterious--how can a single protein both be the core link between cadherins and the cytoskeleton, and the nuclear messenger for Wnt signalling? On the basis of the available evidence and on molecular and evolutionary considerations, I propose that β-catenin was a born nuclear transport receptor, which by interacting with adhesion molecules acquired the property to coordinate nuclear functions with cell-cell adhesion. While Wnt signalling diverted this activity, the original pathway might still function in modern eukaryotes.
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45
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Abstract
The study of iron chelators as anti-tumor agents is still in its infancy. Iron is important for cellular proliferation and this is demonstrated by observations that iron-depletion results in cell cycle arrest and also apoptosis. In addition, many iron chelators are known to inhibit ribonucleotide reductase, the iron-containing enzyme that is the rate-limiting step for DNA synthesis. Desferrioxamine is a well known chelator used for the treatment of iron-overload disease, but it has also been shown to possess anti-cancer activity. Another class of chelators, namely the thiosemicarbazones, have been shown to possess anti-cancer activity since the 1950's, although their mechanism(s) of action have only recently been more comprehensively elucidated. In fact, the redox activity of thiosemicarbazone iron complexes is thought to be important in mediating their potent cytotoxicity. Moreover, unlike typical iron chelators which simply act to deplete tumors of iron, several thiosemicarbazones (i.e., Bp44mT and Dp44mT) do not induce this effect, their anti-cancer efficacy being due to other mechanisms e.g., redox activity. Other reports have also shown that some thiosemicarbazones inhibit topoisomerase IIα, demonstrating that this class of agents have multiple molecular targets and act by various mechanisms. The most well characterized thiosemicarbazone iron chelator in terms of its assessment in humans is 3-aminopyridine-2-carboxaldehyde thiosemicarbazone (3-AP). Observations from these clinical trials highlight the less than optimal activity of this ligand and several side effects related to its use, including myelo-suppression, hypoxia and methemoglobinemia. The mechanisms responsible for these latter effects must be elucidated and the design of the ligand altered to minimize these problems and increase efficacy. This review discusses the development of chelators as unique agents for cancer treatment.
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Affiliation(s)
- S Esufali
- Department of Pathology and Laboratory Medicine, Samuel Lunenfeld Research Institute, Mount Sinai Hospital, University of Toronto, Toronto, Canada
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46
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Liu M, Bi F, Zhou X, Zheng Y. Rho GTPase regulation by miRNAs and covalent modifications. Trends Cell Biol 2012; 22:365-73. [PMID: 22572609 DOI: 10.1016/j.tcb.2012.04.004] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Revised: 04/05/2012] [Accepted: 04/10/2012] [Indexed: 12/15/2022]
Abstract
To date, most studies of Rho GTPase regulation have focused on the classic GTPase cycle - GTP binding and hydrolysis - controlled by guanine nucleotide exchange factors (GEFs), GTPase-activating proteins (GAPs) and GDP-dissociation inhibitors (GDIs). Recent investigations have unveiled important additional regulatory mechanisms: microRNA (miRNA) regulating post-transcriptional processing of Rho GTPase-encoding mRNAs; palmitoylation and nuclear targeting affecting intracellular distribution; post-translational phosphorylation, transglutamination and AMPylation impacting Rho GTPase signaling; and ubiquitination controlling Rho GTPase protein stability and turnover. These modes of regulation add to the complexity of the Rho GTPase signaling network and allow precise spatiotemporal control of individual Rho GTPases. This review discusses these 'unconventional' modes of regulation and their contribution to cellular function, focusing on post-transcriptional and post-translational events beyond the classic GTPase cycle regulatory model.
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Affiliation(s)
- Ming Liu
- Division of Experimental Hematology and Cancer Biology, Children's Hospital Research Foundation, University of Cincinnati, Cincinnati, OH 45229, USA
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47
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Yousef AF, Fonseca GJ, Cohen MJ, Mymryk JS. The C-terminal region of E1A: a molecular tool for cellular cartography. Biochem Cell Biol 2012; 90:153-63. [DOI: 10.1139/o11-080] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The adenovirus E1A proteins function via protein–protein interactions. By making many connections with the cellular protein network, individual modules of this virally encoded hub reprogram numerous aspects of cell function and behavior. Although many of these interactions have been thoroughly studied, those mediated by the C-terminal region of E1A are less well understood. This review focuses on how this region of E1A affects cell cycle progression, apoptosis, senescence, transformation, and conversion of cells to an epithelial state through interactions with CTBP1/2, DYRK1A/B, FOXK1/2, and importin-α. Furthermore, novel potential pathways that the C-terminus of E1A influences through these connections with the cellular interaction network are discussed.
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Affiliation(s)
- Ahmed F. Yousef
- Departments of Microbiology and Immunology and Oncology, The University of Western Ontario, London Regional Cancer Program, London, ON N6A 4L6, Canada
| | - Gregory J. Fonseca
- Departments of Microbiology and Immunology and Oncology, The University of Western Ontario, London Regional Cancer Program, London, ON N6A 4L6, Canada
| | - Michael J. Cohen
- Departments of Microbiology and Immunology and Oncology, The University of Western Ontario, London Regional Cancer Program, London, ON N6A 4L6, Canada
| | - Joe S. Mymryk
- Departments of Microbiology and Immunology and Oncology, The University of Western Ontario, London Regional Cancer Program, London, ON N6A 4L6, Canada
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48
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Mendoza-Catalán MA, Cristóbal-Mondragón GR, Adame-Gómez J, del Valle-Flores HN, Coppe JF, Sierra-López L, Romero-Hernández MA, del Carmen Alarcón-Romero L, Illades-Aguiar B, Castañeda-Saucedo E. Nuclear expression of Rac1 in cervical premalignant lesions and cervical cancer cells. BMC Cancer 2012; 12:116. [PMID: 22443139 PMCID: PMC3340301 DOI: 10.1186/1471-2407-12-116] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2011] [Accepted: 03/23/2012] [Indexed: 01/28/2023] Open
Abstract
Background Abnormal expression of Rho-GTPases has been reported in several human cancers. However, the expression of these proteins in cervical cancer has been poorly investigated. In this study we analyzed the expression of the GTPases Rac1, RhoA, Cdc42, and the Rho-GEFs, Tiam1 and beta-Pix, in cervical pre-malignant lesions and cervical cancer cell lines. Methods Protein expression was analyzed by immunochemistry on 102 cervical paraffin-embedded biopsies: 20 without Squamous Intraepithelial Lesions (SIL), 51 Low- grade SIL, and 31 High-grade SIL; and in cervical cancer cell lines C33A and SiHa, and non-tumorigenic HaCat cells. Nuclear localization of Rac1 in HaCat, C33A and SiHa cells was assessed by cellular fractionation and Western blotting, in the presence or not of a chemical Rac1 inhibitor (NSC23766). Results Immunoreacivity for Rac1, RhoA, Tiam1 and beta-Pix was stronger in L-SIL and H-SIL, compared to samples without SIL, and it was significantly associated with the histological diagnosis. Nuclear expression of Rac1 was observed in 52.9% L-SIL and 48.4% H-SIL, but not in samples without SIL. Rac1 was found in the nucleus of C33A and SiHa cells but not in HaCat cells. Chemical inhibition of Rac1 resulted in reduced cell proliferation in HaCat, C33A and SiHa cells. Conclusion Rac1 is expressed in the nucleus of epithelial cells in SILs and cervical cancer cell lines, and chemical inhibition of Rac1 reduces cellular proliferation. Further studies are needed to better understand the role of Rho-GTPases in cervical cancer progression.
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Affiliation(s)
- Miguel A Mendoza-Catalán
- Laboratorio de Biología Celular del Cáncer, UACQB, Universidad Autónoma de Guerrero, Guerrero, Mexico.
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Abstract
Many bacterial pathogens produce protein toxins to outmanoeuvre the immune system of the host. Some of these proteins target regulatory GTPases such as those belonging to the RHO family, which control the actin cytoskeleton of the host cell. In this Review, I discuss a diversity of mechanisms that are used by bacterial effectors and toxins to modulate the activity of host GTPases, with a focus on covalent modifications such as ADP-ribosylation, glucosylation, adenylylation, proteolysis, deamidation and transglutamination.
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Affiliation(s)
- Klaus Aktories
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Albert-Ludwigs-Universität Freiburg, Albertstr. 25, 79104 Freiburg, Germany.
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Hamel B, Monaghan-Benson E, Rojas RJ, Temple BRS, Marston DJ, Burridge K, Sondek J. SmgGDS is a guanine nucleotide exchange factor that specifically activates RhoA and RhoC. J Biol Chem 2011; 286:12141-8. [PMID: 21242305 PMCID: PMC3069418 DOI: 10.1074/jbc.m110.191122] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2010] [Revised: 01/06/2011] [Indexed: 11/06/2022] Open
Abstract
SmgGDS is an atypical guanine nucleotide exchange factor (GEF) that promotes both cell proliferation and migration and is up-regulated in several types of cancer. SmgGDS has been previously shown to activate a wide variety of small GTPases, including the Ras family members Rap1a, Rap1b, and K-Ras, as well as the Rho family members Cdc42, Rac1, Rac2, RhoA, and RhoB. In contrast, here we show that SmgGDS exclusively activates RhoA and RhoC among a large panel of purified GTPases. Consistent with the well known properties of GEFs, this activation is catalytic, and SmgGDS preferentially binds to nucleotide-depleted RhoA relative to either GDP- or GTPγS-bound forms. However, mutational analyses indicate that SmgGDS utilizes a distinct exchange mechanism compared with canonical GEFs and in contrast to known GEFs requires RhoA to retain a polybasic region for activation. A homology model of SmgGDS highlights an electronegative surface patch and a highly conserved binding groove. Mutation of either area ablates the ability of SmgGDS to activate RhoA. Finally, the in vitro specificity of SmgGDS for RhoA and RhoC is retained in cells. Together, these results indicate that SmgGDS is a bona fide GEF that specifically activates RhoA and RhoC through a unique mechanism not used by other Rho family exchange factors.
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Affiliation(s)
- Brant Hamel
- From the Departments of Biochemistry and Biophysics
| | | | | | - Brenda R. S. Temple
- From the Departments of Biochemistry and Biophysics
- the R. L. Juliano Structural Bioinformatics Core, and
| | | | - Keith Burridge
- Cell and Developmental Biology, and
- the Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599
| | - John Sondek
- From the Departments of Biochemistry and Biophysics
- Pharmacology
- the Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599
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