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Meng L, Shang H, Liu Q, Li Z, Wang X, Li Q, Li F, Zhao Z, Liu C. Lnc-PSMA8-1 activated by GEFT promotes rhabdomyosarcoma progression via upregulation of mTOR expression by sponging miR-144-3p. BMC Cancer 2024; 24:79. [PMID: 38225540 PMCID: PMC10789031 DOI: 10.1186/s12885-023-11798-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Accepted: 12/26/2023] [Indexed: 01/17/2024] Open
Abstract
BACKGROUND GEFT is a key regulator of tumorigenesis in rhabdomyosarcoma (RMS), and overexpression of GEFT is significantly correlated with distant metastasis, lymph node metastasis, and a poor prognosis, yet the underlying molecular mechanism is still poorly understood. This study aimed to investigate and validate the molecular mechanism of GEFT-activated lncRNAs in regulating mTOR expression to promote the progression of RMS. METHODS GEFT-regulated lncRNAs were identified through microarray analysis. The effects of GEFT-regulated lncRNAs on the proliferation, apoptosis, invasion, and migration of RMS cells were confirmed through cell functional experiments. The target miRNAs of GEFT-activated lncRNAs in the regulation of mTOR expression were predicted by bioinformatics analysis combined with quantitative real-time polymerase chain reaction (qRT-PCR) analysis. The expression of lnc-PSMA8-1, miR-144-3p, and mTOR was measured by qRT-PCR in RMS tissue samples and cell lines. The regulatory mechanisms of the lnc-PSMA8-1-miR-144-3p-mTOR signaling axis were verified by RNA-binding protein immunoprecipitation (RIP), a luciferase reporter assay, qRT-PCR analysis, Western blot analysis, and cell functional experiments. RESULTS The microarray-based analysis identified 31 differentially expressed lncRNAs (fold change > 2.0, P < 0.05). Silencing the 4 upregulated lncRNAs (lnc-CEACAM19-1, lnc-VWCE-2, lnc-GPX7-1, and lnc-PSMA8-1) and overexpressing the downregulated lnc-FAM59A-1 inhibited the proliferation, invasion, and migration and induced the apoptosis of RMS cells. Among the factors analyzed, the expression of lnc-PSMA8-1, miR-144-3p, and mTOR in RMS tissue samples and cells was consistent with the correlations among their expression indicated by the lncRNA-miRNA-mRNA regulatory network based on the ceRNA hypothesis. lnc-PSMA8-1 promoted RMS progression by competitively binding to miR-144-3p to regulate mTOR expression. CONCLUSION Our research demonstrated that lnc-PSMA8-1 was activated by GEFT and that the former positively regulated mTOR expression by sponging miR-144-3p to promote the progression of RMS. Therefore, targeting this network may constitute a potential therapeutic approach for the management of RMS.
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Affiliation(s)
- Lian Meng
- Department of Pathology and Key Laboratory for Xinjiang Endemic and Ethnic Diseases, Shihezi University School of Medicine/The First Affiliated Hospital, Shihezi University, Shihezi, China
| | - Hao Shang
- Department of Pathology and Key Laboratory for Xinjiang Endemic and Ethnic Diseases, Shihezi University School of Medicine/The First Affiliated Hospital, Shihezi University, Shihezi, China
- Judicial Appraisal Institute, Tongde Hospital of Zhejiang Province (Zhejiang Mental Health Center), Hangzhou, China
| | - Qianqian Liu
- Department of Pathology and Key Laboratory for Xinjiang Endemic and Ethnic Diseases, Shihezi University School of Medicine/The First Affiliated Hospital, Shihezi University, Shihezi, China
| | - Zhenzhen Li
- Department of Pathology and Key Laboratory for Xinjiang Endemic and Ethnic Diseases, Shihezi University School of Medicine/The First Affiliated Hospital, Shihezi University, Shihezi, China
| | - Xiaomeng Wang
- Department of Pathology and Key Laboratory for Xinjiang Endemic and Ethnic Diseases, Shihezi University School of Medicine/The First Affiliated Hospital, Shihezi University, Shihezi, China
| | - Qianru Li
- Department of Pathology and Key Laboratory for Xinjiang Endemic and Ethnic Diseases, Shihezi University School of Medicine/The First Affiliated Hospital, Shihezi University, Shihezi, China
| | - Feng Li
- Department of Pathology and Key Laboratory for Xinjiang Endemic and Ethnic Diseases, Shihezi University School of Medicine/The First Affiliated Hospital, Shihezi University, Shihezi, China
- Department of Pathology and Medical Research Center, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China
| | - Zhenguo Zhao
- Department of Orthopedics, National Clinical Research Center for Cancer/Cancer Hospital, National Cancer Center, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China.
| | - Chunxia Liu
- Department of Pathology and Key Laboratory for Xinjiang Endemic and Ethnic Diseases, Shihezi University School of Medicine/The First Affiliated Hospital, Shihezi University, Shihezi, China.
- Department of Pathology, The Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China.
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Salamon RS, Backer JM. Phosphatidylinositol-3,4,5-trisphosphate: tool of choice for class I PI 3-kinases. Bioessays 2014; 35:602-11. [PMID: 23765576 DOI: 10.1002/bies.201200176] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Class I PI 3-kinases signal by producing the signaling lipid phosphatidylinositol(3,4,5) trisphosphate, which in turn acts by recruiting downstream effectors that contain specific lipid-binding domains. The class I PI 3-kinases comprise four distinct catalytic subunits linked to one of seven different regulatory subunits. All the class I PI 3-kinases produce the same signaling lipid, PIP3, and the different isoforms have overlapping expression patterns and are coupled to overlapping sets of upstream activators. Nonetheless, studies in cultured cells and in animals have demonstrated that the different isoforms are coupled to distinct ranges of downstream responses. This review focuses on the mechanisms by which the production of a common product, PIP3, can produce isoform-specific signaling by PI 3-kinases.
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Affiliation(s)
- Rachel Schnur Salamon
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, USA
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3
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Jaiswal M, Gremer L, Dvorsky R, Haeusler LC, Cirstea IC, Uhlenbrock K, Ahmadian MR. Mechanistic insights into specificity, activity, and regulatory elements of the regulator of G-protein signaling (RGS)-containing Rho-specific guanine nucleotide exchange factors (GEFs) p115, PDZ-RhoGEF (PRG), and leukemia-associated RhoGEF (LARG). J Biol Chem 2011; 286:18202-12. [PMID: 21454492 DOI: 10.1074/jbc.m111.226431] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The multimodular guanine nucleotide exchange factors (GEFs) of the Dbl family mostly share a tandem Dbl homology (DH) and pleckstrin homology (PH) domain organization. The function of these and other domains in the DH-mediated regulation of the GDP/GTP exchange reaction of the Rho proteins is the subject of intensive investigations. This comparative study presents detailed kinetic data on specificity, activity, and regulation of the catalytic DH domains of four GEFs, namely p115, p190, PDZ-RhoGEF (PRG), and leukemia-associated RhoGEF (LARG). We demonstrate that (i) these GEFs are specific guanine nucleotide exchange factors for the Rho isoforms (RhoA, RhoB, and RhoC) and inactive toward other members of the Rho family, including Rac1, Cdc42, and TC10. (ii) The DH domain of LARG exhibits the highest catalytic activity reported for a Dbl protein till now with a maximal acceleration of the nucleotide exchange by 10(7)-fold, which is at least as efficient as reported for GEFs specific for Ran or the bacterial toxin SopE. (iii) A novel regulatory region at the N terminus of the DH domain is involved in its association with GDP-bound RhoA monitored by a fluorescently labeled RhoA. (iv) The tandem PH domains of p115 and PRG efficiently contribute to the DH-mediated nucleotide exchange reaction. (v) In contrast to the isolated DH or DH-PH domains, a p115 fragment encompassing both the regulator of G-protein signaling and the DH domains revealed a significantly reduced GEF activity, supporting the proposed models of an intramolecular autoinhibitory mechanism for p115-like RhoGEFs.
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Affiliation(s)
- Mamta Jaiswal
- Institut für Biochemie und Molekularbiologie II, Medizinische Fakultät der Heinrich-Heine-Universität, 40225 Düsseldorf, Germany
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4
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Goh LL, Manser E. The RhoA GEF Syx is a target of Rnd3 and regulated via a Raf1-like ubiquitin-related domain. PLoS One 2010; 5:e12409. [PMID: 20811643 PMCID: PMC2928299 DOI: 10.1371/journal.pone.0012409] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2010] [Accepted: 08/04/2010] [Indexed: 12/20/2022] Open
Abstract
Background Rnd3 (RhoE) protein belongs to the unique branch of Rho family GTPases that has low intrinsic GTPase activity and consequently remains constitutively active [1], [2]. The current consensus is that Rnd1 and Rnd3 function as important antagonists of RhoA signaling primarily by activating the ubiquitous p190 RhoGAP [3], but not by inhibiting the ROCK family kinases. Methodology/Principal Findings Rnd3 is abundant in mouse embryonic stem (mES) cells and in an unbiased two-step affinity purification screen we identified a new Rnd3 target, termed synectin-binding RhoA exchange factor (Syx), by mass spectrometry. The Syx interaction with Rnd3 does not occur through the Syx DH domain but utilizes a region similar to the classic Raf1 Ras-binding domain (RBD), and most closely related to those in RGS12 and RGS14. We show that Syx behaves as a genuine effector of Rnd3 (and perhaps Rnd1), with binding characteristics similar to p190-RhoGAP. Morpholino-oligonucleotide knockdown of Syx in zebrafish at the one cell stage resulted in embryos with shortened anterior-posterior body axis: this phenotype was effectively rescued by introducing mouse Syx1b mRNA. A Rnd3-binding defective mutant of Syx1b mutated in the RBD (E164A/R165D) was more potent in rescuing the embryonic defects than wild-type Syx1b, showing that Rnd3 negatively regulates Syx activity in vivo. Conclusions/Significance This study uncovers a well defined Rnd3 effector Syx which is widely expressed and directly impacts RhoA activation. Experiments conducted in vivo indicate that Rnd3 negatively regulates Syx, and that as a RhoA-GEF it plays a key role in early embryonic cell shape changes. Thus a connection to signaling via the planar cell polarity pathway is suggested.
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Affiliation(s)
- Liuh Ling Goh
- Rho GTPases in Stem Cells (RGS) Group, Institute of Medical Biology (IMB), Singapore, Singapore
| | - Ed Manser
- Rho GTPases in Stem Cells (RGS) Group, Institute of Medical Biology (IMB), Singapore, Singapore
- Small G-Protein Signaling and Kinases (sGSK) Group, Institute of Molecular and Cell Biology (IMCB), Neuroscience Research Partnership, Singapore, Singapore
- * E-mail:
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5
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Porchia F, Papucci M, Gargini C, Asta A, De Marco G, Agretti P, Tonacchera M, Mazzoni MR. Endothelin-1 up-regulates p115RhoGEF in embryonic rat cardiomyocytes during the hypertrophic response. J Recept Signal Transduct Res 2008; 28:265-83. [PMID: 18569527 DOI: 10.1080/10799890802084515] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
In cardiomyocytes, certain extracellular stimuli that activate heterotrimeric G protein-coupled receptors (GPCRs) can induce hypertrophy by regulating gene expression and increasing protein synthesis. We investigated if rat embryonic cardiomyocytes (H9c2) underwent variations in the expression levels and subcellular distribution of key components of GPCR-activated signaling pathways during endothelin-1 (ET-1)-induced hypertrophic response. A significant increase of p115RhoGEF protein level was evident in ET-1-treated cells. Real-time quantitative PCR showed RhoGEF mRNA levels were significantly increased. Inhibition of the Rho-associated kinase (ROCK) caused a significant decrease of p115RhoGEF protein in the nuclear fraction, whereas an inhibitor of PKC induced a redistribution of the protein between membrane/organelle and nuclear fractions. The ROCK inhibitor also decreased H9c2 cell hypertrophic response. These results indicate that ROCK and its downstream target molecules, which are involved in inducing the hypertrophic response, are also implicated in signaling the up-regulation of the p115RhoGEF protein.
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Affiliation(s)
- Francesca Porchia
- Dipartimento di Psichiatria, Neurobiologia, Farmacologia e Biotecnologie, University of Pisa, Pisa, Italy
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6
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Abstract
Asef is a member of the Dbl-family of guanine nucleotide exchange factors (GEFs) with a proposed specificity for the small GTPase Rac1. Here we investigated the specificity and regulation of Asef by measuring its GEF activity in vitro and observed hardly any activity towards Rac1, Rac2 and Rac3, or RhoA and TC10. In contrast, various purified Asef protein fragments catalyzed the nucleotide exchange reaction of Cdc42. The Cdc42GEF activity of the Dbl homology (DH) domain of Asef was significantly higher in the presence of the pleckstrin homology (PH) domain. Our data strongly suggest that Asef is a canonical Cdc42GEF, which employs its PH domain to efficiently stabilize its autoinhibited state, but also to facilitate nucleotide exchange activity of the DH domain after its activation by upstream signals.
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Affiliation(s)
- Katja Gotthardt
- Department of Structural Biology, Max Planck Institute of Molecular Physiology, Otto-Hahn-Strasse 11, D-44227 Dortmund, Germany
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7
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Hikita T, Qadota H, Tsuboi D, Taya S, Moerman DG, Kaibuchi K. Identification of a novel Cdc42 GEF that is localized to the PAT-3-mediated adhesive structure. Biochem Biophys Res Commun 2005; 335:139-45. [PMID: 16055082 DOI: 10.1016/j.bbrc.2005.07.068] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2005] [Accepted: 07/13/2005] [Indexed: 10/25/2022]
Abstract
In the model organism Caenorhabditis elegans, UNC-112 is colocalized with PAT-3/beta-integrin and is a critical protein in the formation of PAT-3-mediated adhesive structure in body-wall muscle cells. However, the signaling pathway downstream of PAT-3/UNC-112 is largely unknown. To clarify the signaling pathway from PAT-3/UNC-112 to the actin cytoskeleton, we searched for and identified a novel Dbl homology/pleckstrin homology (DH/PH) domain containing protein, UIG-1 (UNC-112-interacting guanine nucleotide exchange factor-1). UIG-1 was colocalized with UNC-112 at dense bodies in body-wall muscle cells. UIG-1 showed CDC-42-specific GEF activity in vitro and induced filopodia formation in NIH 3T3 cells. Depletion of CDC-42 or PAT-3 in the developmental stage, by RNAi, prevented the formation of continuous actin filament in body-wall muscle cells. Taken together, these results suggest that UIG-1 links a PAT-3/UNC-112 complex to the CDC-42 signaling pathway during muscle formation.
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Affiliation(s)
- Takao Hikita
- Department of Cell Pharmacology, Graduate School of Medicine, Nagoya University, 65 Tsurumai, Showa-ku, Nagoya, Aichi 466-8550, Japan
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8
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Bryan B, Kumar V, Stafford LJ, Cai Y, Wu G, Liu M. GEFT, a Rho family guanine nucleotide exchange factor, regulates neurite outgrowth and dendritic spine formation. J Biol Chem 2004; 279:45824-32. [PMID: 15322108 DOI: 10.1074/jbc.m406216200] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Rho family of small GTPases controls a wide range of cellular processes in eukaryotic cells, such as normal cell growth, proliferation, differentiation, gene regulation, actin cytoskeletal organization, cell fate determination, and neurite outgrowth. The activation of Rho-GTPases requires the exchange of GDP for GTP, a process catalyzed by the Dbl family of guanine nucleotide exchange factors. We demonstrate that a newly identified guanine nucleotide exchange factor, GEFT, is widely expressed in the brain and highly concentrated in the hippocampus, and the Purkinje and granular cells of the cerebellum. Exogenous expression of GEFT promotes dendrite outgrowth in hippocampal neurons, resulting in spines with larger size as compared with control spines. In neuroblastoma cells, GEFT promotes the active GTP-bound state of Rac1, Cdc42, and RhoA and increases neurite outgrowth primarily via Rac1. Furthermore, we demonstrated that PAK1 and PAK5, both downstream effectors of Rac1/Cdc42, are necessary for GEFT-induced neurite outgrowth. AP-1 and NF-kappaB, two transcriptional factors involved in neurite outgrowth and survival, were up-regulated in GEFT-expressing cells. Together, our data suggest that GEFT enhances dendritic spine formation and neurite outgrowth in primary neurons and neuroblastoma cells, respectively, through the activation of Rac/Cdc42-PAK signaling pathways.
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Affiliation(s)
- Brad Bryan
- Alkek Institute of Biosciences and Technology, and Department of Medical Biochemistry and Genetics, Texas A and M University System Health Science Center, Houston, TX 77030, USA
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9
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Abstract
Rho-family proteins control signalling pathways that regulate a wide range of biological processes. In vitro studies implicating Rho proteins in cell adhesion, migration, transcriptional activation, cell-cycle progression and transformation suggested roles for these proteins in the formation and progression of tumours in vivo. Studies using different recombinant mouse models have recently confirmed this idea. Rho signalling pathways crosstalk with different oncogenic signalling cascades, including those downstream of Ras and Wnt, and contribute to various aspects of tumourigenesis, including survival, growth and progression of tumour cells.
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Affiliation(s)
- Angeliki Malliri
- The Netherlands Cancer Institute, Division of Cell Biology, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands.
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10
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Brecht M, Steenvoorden ACM, Collard JG, Luf S, Erz D, Bartram CR, Janssen JWG. Activation ofgef-h1, a guanine nucleotide exchange factor for RhoA, by DNA transfection. Int J Cancer 2004; 113:533-40. [PMID: 15455375 DOI: 10.1002/ijc.20626] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Several oncogenes isolated by the NIH/3T3 transformation assay, i.e., dbl, dbs, lbc, lfc, lsc, net, ost and tim, contain a Dbl homology (DH) and a pleckstrin-homology (PH) domain and act as GEFs (guanine nucleotide exchange factors) for Rho-like GTPases. In a search for genes with oncogenic potential in DNA from the monocytic leukaemia cell line U937, we identified an amino-terminal truncated form of gef-h1, a gene encoding a GEF for RhoA. These data support the idea that a systematic search for mutations and/or deletions of GEFs in human cancer is promising.
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Affiliation(s)
- Marcus Brecht
- University of Heidelberg, Institute of Human Genetics, Im Neunheimer Feld 366, D-69120 Heidelberg, Germany
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11
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Kawakita A, Yamashita T, Taniguchi M, Koyama Y, Kubo T, Tsuji L, Tohyama M. Developmental regulation of FERM domain including guanine nucleotide exchange factor gene expression in the mouse brain. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 2003; 144:181-9. [PMID: 12935915 DOI: 10.1016/s0165-3806(03)00169-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
FERM domain including Rho GEF (FIR) is one of the guanine nucleotide exchange factors for Rac1. FIR, expressed in hippocampal and cortical neurons in vitro, is suggested to be involved in neurite remodeling. We examine developmental regulation of FIR mRNA expression in the mouse brain using in situ hybridization to get insight into its function. FIR mRNA is expressed in the ventricular zone and the intermediate zone as well as the cortical plate and the preplate in the brain from mice during the embryonic stages 12.5 to 14.5. In the brain during the later embryonic stages and the postnatal stages, the expression was restricted to the cortical plate. These results suggest that FIR may play a role not only in neurogenesis, but also in the asymmetrical cell division and migration of neurons.
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Affiliation(s)
- Akihiro Kawakita
- Department of Anatomy and Neuroscience, Graduate School of Medicine, Osaka University, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan
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12
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Madura T, Yamashita T, Kubo T, Taniguchi M, Kawakita A, Hosokawa K, Tohyama M. Expression of FERM domain including guanine nucleotide exchange factor mRNA in adult rat brain. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 2003; 114:163-7. [PMID: 12829327 DOI: 10.1016/s0169-328x(03)00166-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
FERM domain including Rho GEF (FIR) belongs to Dbl family of guanine nucleotide exchange factors and specifically activates biochemical pathways specific for Rac1. FIR was shown to regulate neurite remodeling of the embryonic neurons. Here we report a distribution of FIR mRNA in adult rat brain using in situ hybridization. The expression was found all throughout the brain with the most intensive signals in hippocampus, piriform cortex, red nucleus and nuclei of cranial nerves. The signal was predominantly localized in the neuronal cells.
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Affiliation(s)
- Tomas Madura
- Department of Anatomy and Neuroscience, Graduate School of Medicine, Osaka University, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan
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13
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A novel FERM domain including guanine nucleotide exchange factor is involved in Rac signaling and regulates neurite remodeling. J Neurosci 2002. [PMID: 12351724 DOI: 10.1523/jneurosci.22-19-08504.2002] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The Rho family of small GTPases, key regulators of the actin cytoskeleton in eukaryotic cells from yeast to human, is implicated in the control of neuronal morphology. Guanine nucleotide exchange factors (GEFs) are upstream positive regulators of Rho GTPases and integrate extracellular signaling for appropriate activation of Rho GTPases at specific subcellular regions. Here we describe the identification of a novel Dbl family GEF for Rho GTPases in Homo sapiens and Mus musculus. It contains a tandem Dbl homology-pleckstrin homology domain and FERM domain, characteristic of the plasma membrane proteins linker. This gene, termed FERM domain including RhoGEF (FIR), was abundantly expressed in brain, lung, and testis, as well as embryonic hippocampal and cortical neurons. FIR was found to activate the biochemical pathway specific for Rac1 but not for RhoA or Cdc42. Ectopic expression of FIR in the cortical neurons resulted in significantly shortened neurites and excessive growth cones, presumably mediated by Rac1. These results suggest that FIR may regulate neurite remodeling by mediating the signaling pathways from membrane proteins to Rac.
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14
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Rümenapp U, Freichel-Blomquist A, Wittinghofer B, Jakobs KH, Wieland T. A mammalian Rho-specific guanine-nucleotide exchange factor (p164-RhoGEF) without a pleckstrin homology domain. Biochem J 2002; 366:721-8. [PMID: 12071859 PMCID: PMC1222833 DOI: 10.1042/bj20020654] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2002] [Revised: 06/07/2002] [Accepted: 06/19/2002] [Indexed: 11/17/2022]
Abstract
Rho GTPases, which are activated by specific guanine-nucleotide exchange factors (GEFs), play pivotal roles in several cellular functions. We identified a recently cloned human cDNA, namely KIAA0337, encoding a protein containing 1510 amino acids (p164). It contains a RhoGEF-specific Dbl homology (DH) domain but lacks their typical pleckstrin homology domain. The expression of the mRNA encoding p164 was found to be at least 4-fold higher in the heart than in other tissues. Recombinant p164 interacted with and induced GDP/GTP exchange at RhoA but not at Rac1 or Cdc42. p164-DeltaC and p164-DeltaN are p164 mutants that are truncated at the C- and N-termini respectively but contain the DH domain. In contrast with the full-length p164, expression of p164-DeltaC and p164-DeltaN strongly induced actin stress fibre formation and activated serum response factor-mediated and Rho-dependent gene transcription. Interestingly, p164-DeltaN2, a mutant containing the C-terminus but having a defective DH domain, bound to p164-DeltaC and suppressed the p164-DeltaC-induced gene transcription. Overexpression of the full-length p164 inhibited M(3) muscarinic receptor-induced gene transcription, whereas co-expression with Gbeta(1)gamma(2) dimers induced transcriptional activity. It is concluded that p164-RhoGEF is a Rho-specific GEF with novel structural and regulatory properties and predominant expression in the heart. Apparently, its N- and C-termini interact with each other, thereby inhibiting its GEF activity.
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Affiliation(s)
- Ulrich Rümenapp
- Institut für Pharmakologie, Universitätsklinikum Essen, Hufelandstrasse 55, Germany
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15
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Schmidt S, Diriong S, Méry J, Fabbrizio E, Debant A. Identification of the first Rho-GEF inhibitor, TRIPalpha, which targets the RhoA-specific GEF domain of Trio. FEBS Lett 2002; 523:35-42. [PMID: 12123800 DOI: 10.1016/s0014-5793(02)02928-9] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The Rho-guanine nucleotide exchange factors (Rho-GEFs) remodel the actin cytoskeleton via their Rho-GTPase targets and affect numerous physiological processes such as transformation and cell motility. They are therefore attractive targets to design specific inhibitors that may have therapeutic applications. Trio contains two Rho-GEF domains, GEFD1 and GEFD2, which activate the Rac and RhoA pathways, respectively. Here we have used a genetic screen in yeast to select in vivo peptides coupled to thioredoxin, called aptamers, that could inhibit GEFD2 activity. One aptamer, TRIAPalpha (TRio Inhibitory APtamer), specifically blocks GEFD2-exchange activity on RhoA in vitro. The corresponding peptide sequence, TRIPalpha, inhibits TrioGEFD2-mediated activation of RhoA in intact cells and specifically reverts the neurite retraction phenotype induced by TrioGEFD2 in PC12 cells. Thus TRIPalpha is the first Rho-GEF inhibitor isolated so far, and represents an important step in the design of inhibitors for the expanding family of Rho-GEFs.
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Affiliation(s)
- Susanne Schmidt
- CRBM-CNRS, UPR 1086 CNRS, 1919 Route de Mende, 34293 Cedex 5, Montpellier, France
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16
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Abstract
Net1 is a guanine nucleotide exchange factor specific for the small GTPase Rho. Oncogenic activation of Net1 occurs by truncation of the N-terminal part of the protein, which functions as a negative regulatory domain. Here, we have investigated the mechanism of Net1 regulation via its N terminus. We find that Net1 localizes to the nucleus, whereas oncogenic Net1 is found in the cytoplasm. Nuclear import of Net1 is mediated by two nuclear localization signals present in the N terminus of the protein, and forced cytoplasmic localization of Net1 is sufficient to activate Rho. In addition, the pleckstrin homology (PH) domain of Net1 acts as a nuclear export signal. Because an amino acid substitution in the PH domain that inhibits guanine nucleotide exchange factor activity does not inhibit nuclear export, we conclude that this PH domain has at least two functions. Together, our results suggest that Net1 can shuttle in and out of the nucleus, and that activation of Rho by Net1 is controlled by changes in its subcellular localization.
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Affiliation(s)
- Anja Schmidt
- Medical Research Council Laboratory for Molecular Cell Biology and Cancer Research Campaign Oncogene and Signal Transduction Group, University College London, Gower Street, London WC1E 6BT, United Kingdom
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17
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Welch HCE, Coadwell WJ, Ellson CD, Ferguson GJ, Andrews SR, Erdjument-Bromage H, Tempst P, Hawkins PT, Stephens LR. P-Rex1, a PtdIns(3,4,5)P3- and Gbetagamma-regulated guanine-nucleotide exchange factor for Rac. Cell 2002; 108:809-21. [PMID: 11955434 DOI: 10.1016/s0092-8674(02)00663-3] [Citation(s) in RCA: 419] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Rac, a member of the Rho family of monomeric GTPases, is an integrator of intracellular signaling in a wide range of cellular processes. We have purified a PtdIns(3,4,5)P3-sensitive activator of Rac from neutrophil cytosol. It is an abundant, 185 kDa guanine-nucleotide exchange factor (GEF), which we cloned and named P-Rex1. The recombinant enzyme has Rac-GEF activity that is directly, substantially, and synergistically activated by PtdIns(3,4,5)P3 and Gbetagammas both in vitro and in vivo. P-Rex1 antisense oligonucleotides reduced endogenous P-Rex1 expression and C5a-stimulated reactive oxygen species formation in a neutrophil-like cell line. P-Rex1 appears to be a coincidence detector in PtdIns(3,4,5)P3 and Gbetagamma signaling pathways that is particularly adapted to function downstream of heterotrimeric G proteins in neutrophils.
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Estrach S, Schmidt S, Diriong S, Penna A, Blangy A, Fort P, Debant A. The Human Rho-GEF trio and its target GTPase RhoG are involved in the NGF pathway, leading to neurite outgrowth. Curr Biol 2002; 12:307-12. [PMID: 11864571 DOI: 10.1016/s0960-9822(02)00658-9] [Citation(s) in RCA: 133] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Rho-GTPases control a wide range of physiological processes by regulating actin cytoskeleton dynamics. Numerous studies on neuronal cell lines have established that Rac, Cdc42, and RhoG activate neurite extension, while RhoA mediates neurite retraction. Guanine nucleotide exchange factors (GEFs) activate Rho-GTPases by accelerating GDP/GTP exchange. Trio displays two Rho-GEF domains, GEFD1, activating the Rac pathway via RhoG, and GEFD2, acting on RhoA, and contains numerous signaling motifs whose contribution to Trio function has not yet been investigated. Genetic analyses in Drosophila and in Caenorhabditis elegans indicate that Trio is involved in axon guidance and cell motility via a GEFD1-dependent process, suggesting that the activity of its Rho-GEFs is strictly regulated. Here, we show that human Trio induces neurite outgrowth in PC12 cells in a GEFD1-dependent manner. Interestingly, the spectrin repeats and the SH3-1 domain of Trio are essential for GEFD1-mediated neurite outgrowth, revealing an unexpected role for these motifs in Trio function. Moreover, we demonstrate that Trio-induced neurite outgrowth is mediated by the GEFD1-dependent activation of RhoG, previously shown to be part of the NGF (nerve growth factor) pathway. The expression of different Trio mutants interferes with NGF-induced neurite outgrowth, suggesting that Trio may be an upstream regulator of RhoG in this pathway. In addition, we show that Trio protein accumulates under NGF stimulation. Thus, Trio is the first identified Rho-GEF involved in the NGF-differentiation signaling.
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Affiliation(s)
- Soline Estrach
- CRBM-CNRS, UPR 1086 CNRS, 1919 Route de Mende, 34293 5, Montpellier Cédex, France
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19
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Souchet M, Portales-Casamar E, Mazurais D, Schmidt S, Léger I, Javré JL, Robert P, Berrebi-Bertrand I, Bril A, Gout B, Debant A, Calmels TPG. Human p63RhoGEF, a novel RhoA-specific guanine nucleotide exchange factor, is localized in cardiac sarcomere. J Cell Sci 2002; 115:629-40. [PMID: 11861769 DOI: 10.1242/jcs.115.3.629] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
The Rho small GTPases are crucial proteins involved in regulation of signal transduction cascades from extracellular stimuli to cell nucleus and cytoskeleton. It has been reported that these GTPases are directly associated with cardiovascular disorders. In this context, we have searched for novel modulators of Rho GTPases, and here we describe p63RhoGEF a new Db1-like guanine nucleotide exchange factor (GEF). P63RhoGEF encodes a 63 kDa protein containing a Db1 homology domain in tandem with a pleckstrin homology domain and is most closely related to the second Rho GEF domain of Trio. Northern blot and in situ analysis have shown that p63RhoGEF is mainly expressed in heart and brain. In vitro guanine nucleotide exchange assays have shown that p63RhoGEF specifically acts on RhoA. Accordingly, p63RhoGEF expression induces RhoA-dependent stress fiber formation in fibroblasts and in H9C2 cardiac myoblasts. Moreover, we show that p63RhoGEF activation of RhoA in intact cells is dependent on the presence of the PH domain. Using a specific anti-p63RhoGEF antibody, we have detected the p63RhoGEF protein by immunocytochemistry in human heart and brain tissue sections. Confocal microscopy shows that p63RhoGEF is located in the sarcomeric I-band mainly constituted of cardiac sarcomeric actin. Together, these results show that p63RhoGEF is a RhoA-specific GEF that may play a key role in actin cytoskeleton reorganization in different tissues, especially in heart cellular morphology.
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Affiliation(s)
- Michel Souchet
- SmithKline Beecham Laboratoires Pharmaceutiques, Unité de Biologie Cardiovasculaire, 4 rue du Chesnay Beauregard, BP 96205, 35760 Saint-Grégoire, France
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20
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Bellanger JM, Schmidt S, Estrach S, Portales-Casamar É, Diriong S, Debant A. Trio : Un facteur d’échange des GTPases Rho aux multiples facettes impliqué dans le guidage axonal. Med Sci (Paris) 2001. [DOI: 10.1051/medsci/200117121316] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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21
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Taya S, Inagaki N, Sengiku H, Makino H, Iwamatsu A, Urakawa I, Nagao K, Kataoka S, Kaibuchi K. Direct interaction of insulin-like growth factor-1 receptor with leukemia-associated RhoGEF. J Cell Biol 2001; 155:809-20. [PMID: 11724822 PMCID: PMC2150867 DOI: 10.1083/jcb.200106139] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Insulin-like growth factor (IGF)-1 plays crucial roles in growth control and rearrangements of the cytoskeleton. IGF-1 binds to the IGF-1 receptor and thereby induces the autophosphorylation of this receptor at its tyrosine residues. The phosphorylation of the IGF-1 receptor is thought to initiate a cascade of events. Although various signaling molecules have been identified, they appear to interact with the tyrosine-phosphorylated IGF-1 receptor. Here, we identified leukemia-associated Rho guanine nucleotide exchange factor (GEF) (LARG), which contains the PSD-95/Dlg/ZO-1 (PDZ), regulator of G protein signaling (RGS), Dbl homology, and pleckstrin homology domains, as a nonphosphorylated IGF-1 receptor-interacting molecule. LARG formed a complex with the IGF-1 receptor in vivo, and the PDZ domain of LARG interacted directly with the COOH-terminal domain of IGF-1 receptor in vitro. LARG had an exchange activity for Rho in vitro and induced the formation of stress fibers in NIH 3T3 fibroblasts. When MDCKII epithelial cells were treated with IGF-1, Rho and its effector Rho-associated kinase (Rho-kinase) were activated and actin stress fibers were enhanced. Furthermore, the IGF-1-induced Rho-kinase activation and the enhancement of stress fibers were inhibited by ectopic expression of the PDZ and RGS domains of LARG. Taken together, these results indicate that IGF-1 activates the Rho/Rho-kinase pathway via a LARG/IGF-1 receptor complex and thereby regulates cytoskeletal rearrangements.
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Affiliation(s)
- S Taya
- Department of Cell Pharmacology, Graduate School of Medicine, Nagoya University, Showa-ku, Nagoya 466-8550, Japan
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22
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De Toledo M, Coulon V, Schmidt S, Fort P, Blangy A. The gene for a new brain specific RhoA exchange factor maps to the highly unstable chromosomal region 1p36.2-1p36.3. Oncogene 2001; 20:7307-17. [PMID: 11704860 DOI: 10.1038/sj.onc.1204921] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2001] [Revised: 06/25/2001] [Accepted: 08/14/2001] [Indexed: 11/09/2022]
Abstract
Guanine nucleotide exchange factors from the Dbl family are proto-oncogenic proteins that activate small GTPases of the Rho family. Here we report the characterization of GEF720, a novel Dbl-like protein related to p115Rho-GEF. GEF720 activated RhoA both in our recently developed Yeast Exchange Assay and in biochemical in vitro exchange assays. GEF720 induced RhoA dependent assembly of actin stress fibers in REF52 fibroblastic cells. In NIH3T3 cells this Dbl-like protein elicited formation of transformation foci with a morphology similar to RhoA-V14 induced foci. In the PC12 neuron-like cell line, expression of GEF720, whose mRNA is brain specific, inhibited NGF-induced neurite outgrowth. Finally, GEF720 gene is located on human chromosome 1 on band 1p36, between Tumor Protein 73 and Tumor Necrosis Factor Receptor 12, two genes rearranged in many neuroblastoma cell lines. Together, these results show that this new Dbl related protein, GEF720, is an exchange factor that can directly activate RhoA in vivo and is potentially involved in the control of neuronal cell differentiation. GEF720 is also a new candidate gene involved in the progression of neuroblastoma and developmental abnormalities associated with rearrangements in the 1p36 chromosomal region.
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Affiliation(s)
- M De Toledo
- Centre de Recherches en Biochimie Macromoléculaire, CNRS IFR24-UPR 1086, 1919 route de Mende, 34293 Montpellier Cedex 5, France
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23
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Friebel A, Ilchmann H, Aepfelbacher M, Ehrbar K, Machleidt W, Hardt WD. SopE and SopE2 from Salmonella typhimurium activate different sets of RhoGTPases of the host cell. J Biol Chem 2001; 276:34035-40. [PMID: 11440999 DOI: 10.1074/jbc.m100609200] [Citation(s) in RCA: 179] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The bacterial enteropathogen Salmonella typhimurium employs a specialized type III secretion system to inject toxins into host cells, which trigger signaling cascades leading to cell death in macrophages, secretion of pro-inflammatory cytokines, or rearrangements of the host cell cytoskeleton and thus to bacterial invasion. Two of the injected toxins, SopE and the 69% identical protein SopE2, are highly efficient guanine nucleotide exchange factors for the RhoGTPase Cdc42 of the host cell. However, it has been a puzzle why S. typhimurium might employ two toxins with redundant function. We hypothesized that SopE and SopE2 might have different specificities for certain host cellular RhoGTPases. In vitro guanine nucleotide exchange assays and surface plasmon resonance measurements revealed that SopE is an efficient guanine nucleotide exchange factor for Cdc42 and Rac1, whereas SopE2 was interacting efficiently only with Cdc42, but not with Rac1. Affinity precipitation of Cdc42.GTP and Rac1.GTP from lysates and characteristic cytoskeletal rearrangements of infected tissue culture cells confirmed that SopE is highly efficient at activating Cdc42 and Rac1 in vivo, whereas SopE2 was efficiently activating Cdc42, but not Rac1. We conclude that the translocated effector proteins SopE and SopE2 allow S. typhimurium to specifically activate different sets of RhoGTPase signaling cascades.
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Affiliation(s)
- A Friebel
- Max von Pettenkofer-Institut, Ludwig Maximilians Universität, Pettenkoferstrasse 9a, 80336 München, Germany
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24
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Longenecker KL, Lewis ME, Chikumi H, Gutkind JS, Derewenda ZS. Structure of the RGS-like domain from PDZ-RhoGEF: linking heterotrimeric g protein-coupled signaling to Rho GTPases. Structure 2001; 9:559-69. [PMID: 11470431 DOI: 10.1016/s0969-2126(01)00620-7] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
BACKGROUND The multidomain PDZ-RhoGEF is one of many known guanine nucleotide exchange factors that upregulate Rho GTPases. PDZ-RhoGEF and related family members play a critical role in a molecular signaling pathway from heterotrimeric G protein-coupled receptors to Rho proteins. A approximately 200 residue RGS-like (RGSL) domain in PDZ-RhoGEF and its homologs is responsible for the direct association with Galpha12/13 proteins. To better understand structure-function relationships, we initiated crystallographic studies of the RGSL domain from human PDZ-RhoGEF. RESULTS A recombinant construct of the RGSL domain was expressed in Escherichia coli and purified, but it did not crystallize. Alternative constructs were designed based on a novel strategy of targeting lysine and glutamic acid residues for mutagenesis to alanine. A triple-point mutant functionally identical to the wild-type protein was crystallized, and its structure was determined by the MAD method using Se-methionine (Se-Met) incorporation. A molecular model of the RGSL domain was refined at 2.2 A resolution, revealing an all-helical tertiary fold with the mutations located at intermolecular lattice contacts. CONCLUSIONS The first nine helices adopt a fold similar to that observed for RGS proteins, although the sequence identity with other such known structures is below 20%. The last three helices are an integral extension of the RGS fold, packing tightly against helices 3 and 4 with multiple hydrophobic interactions. Comparison with RGS proteins suggests features that are likely relevant for interaction with G proteins. Finally, we conclude that the strategy used to produce crystals was beneficial and might be applicable to other proteins resistant to crystallization.
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Affiliation(s)
- K L Longenecker
- Department of Molecular Physiology and Biological Physics, University of Virginia, P.O. Box 800736, Charlottesville, VA 22908, USA
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25
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Garrard SM, Longenecker KL, Lewis ME, Sheffield PJ, Derewenda ZS. Expression, purification, and crystallization of the RGS-like domain from the Rho nucleotide exchange factor, PDZ-RhoGEF, using the surface entropy reduction approach. Protein Expr Purif 2001; 21:412-6. [PMID: 11281715 DOI: 10.1006/prep.2001.1392] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Lsc-homology domains are found in several eukaryotic nucleotide exchange factors which act on Rho-family GTPases. They show limited amino acid sequence similarity to RGS proteins, which down-regulate the cellular signaling by the alpha-subunits of trimeric G-proteins and have been shown to interact with Galpha12 and Galpha13. It is believed that the RGS-like (RGSL) domain constitutes the functional link between G-protein-coupled receptors and cytosolic Rho-GTPases. We report here the expression, purification, and crystallization of the RGSL domain from the PDZ-RhoGEF. To obtain X-ray-grade crystals we have used the recently proposed approach of crystallization by mutational surface entropy reduction, in which selected Lys --> Ala, Glu --> Ala, and/or combined point mutations are introduced into the target protein to reduce the cumulative conformational entropy of surface residues. Of the five mutants that were designed and prepared, the second one tried (K463A, E465A, E466A) yielded crystals suitable for further analysis and diffracted X-rays to 2.8 A resolution on a home source. The crystals exhibit hexagonal symmetry, space group P6(1) 22 or P6(5) 22, with unit cell parameters a = b = 63.1 A, c = 202.1 A, and contain one molecule in the asymmetric unit.
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Affiliation(s)
- S M Garrard
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA 22906-0011, USA
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26
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Price LS, Collard JG. Regulation of the cytoskeleton by Rho-family GTPases: implications for tumour cell invasion. Semin Cancer Biol 2001; 11:167-73. [PMID: 11322835 DOI: 10.1006/scbi.2000.0367] [Citation(s) in RCA: 99] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Rho-like GTPases regulate both cell-cell and cell-matrix adhesions and can influence the motile and invasive properties of tumour cells in vitro. Increased Rac signalling can promote either cell-cell adhesion or motility depending on the cell type and composition of the extracellular matrix. Ultimately, the balance of Rac and Rho activities and intracellular localization appears to be critical in determining the cellular phenotype.
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Affiliation(s)
- L S Price
- Division of Cell Biology, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
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27
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van Horck FP, Ahmadian MR, Haeusler LC, Moolenaar WH, Kranenburg O. Characterization of p190RhoGEF, a RhoA-specific guanine nucleotide exchange factor that interacts with microtubules. J Biol Chem 2001; 276:4948-56. [PMID: 11058585 DOI: 10.1074/jbc.m003839200] [Citation(s) in RCA: 144] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Rho family GTPases control numerous cellular processes including cytoskeletal reorganization and transcriptional activation. Rho GTPases are activated by guanine nucleotide exchange factors (GEFs) which stimulate the exchange of bound GDP for GTP. We recently isolated a putative GEF, termed p190RhoGEF that binds to RhoA and, when overexpressed in neuronal cells, induces cell rounding and inhibits neurite outgrowth. Here we show that the isolated tandem Dbl homology/pleckstrin homology domain of p190RhoGEF activates RhoA in vitro, but not Rac1 or Cdc42, as determined by GDP release and protein binding assays. In contrast, full-length p190RhoGEF fails to activate RhoA in vitro. When overexpressed in intact cells, however, p190RhoGEF does activate RhoA with subsequent F-actin reorganization and serum response factor-mediated transcription. Immunofluorescence studies show that endogenous p190RhoGEF localizes to distinct RhoA-containing regions at the plasma membrane, to the cytosol and along microtubules. In vitro and in vivo binding experiments show that p190RhoGEF directly interacts with microtubules via its C-terminal region adjacent to the catalytic Dbl homology/pleckstrin homology domain. Our results indicate that p190RhoGEF is a specific activator of RhoA that requires as yet unknown binding partners to unmask its GDP/GTP exchange activity in vivo, and they suggest that p190RhoGEF may provide a link between microtubule dynamics and RhoA signaling.
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Affiliation(s)
- F P van Horck
- Division of Cellular Biochemistry, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
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28
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Kneussel M, Engelkamp D, Betz H. Distribution of transcripts for the brain-specific GDP/GTP exchange factor collybistin in the developing mouse brain. Eur J Neurosci 2001; 13:487-92. [PMID: 11168555 DOI: 10.1046/j.0953-816x.2000.01411.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The dbl-like GDP/GTP exchange factor, collybistin, binds to the receptor anchoring protein gephyrin and activates the Rho-like GTPase Cdc42. Collybistin was found in two splice variants I and II, both of which share a tandem Dbl homology/pleckstrin homology (DH/PH) domain. In heterologous expression systems, collybistin II induces the formation of submembraneous gephyrin aggregates and therefore has been implicated in inhibitory synapse formation. Expression of collybistin is restricted to neuronal tissues and is predominantly found in brain. Here, we investigated the spatio-temporal distribution of collybistin transcripts in the embryonic mouse brain and compared it to gephyrin and glycine receptor mRNA patterns. Our data show that collybistin expression is upregulated when neurons become postmitotic and start to differentiate.
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Affiliation(s)
- M Kneussel
- Department of Neurochemistry, Max-Planck-Institute for Brain Research, Deutschordenstrasse 46, D-60528 Frankfurt/Main, Germany.
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29
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Bellanger JM, Astier C, Sardet C, Ohta Y, Stossel TP, Debant A. The Rac1- and RhoG-specific GEF domain of Trio targets filamin to remodel cytoskeletal actin. Nat Cell Biol 2000; 2:888-92. [PMID: 11146652 DOI: 10.1038/35046533] [Citation(s) in RCA: 172] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Rho GTPases control actin reorganization and many other cellular functions. Guanine nucleotide-exchange factors (GEFs) activate Rho GTPases by promoting their exchange of GDP for GTP. Trio is a unique Rho GEF, because it has separate GEF domains, GEFD1 and GEFD2, that control the GTPases RhoG/Rac1 and RhoA, respectively. Dbl-homology (DH) domains that are common to GEFs catalyse nucleotide exchange, and pleckstrin-homology (PH) domains localize Rho GEFs near their downstream targets. Here we show that Trio GEFD1 interacts through its PH domain with the actin-filament-crosslinking protein filamin, and localizes with endogenous filamin in HeLa cells. Trio GEFD1 induces actin-based ruffling in filamin-expressing, but not filamin-deficient, cells and in cells transfected with a filamin construct that lacks the Trio-binding domain. In addition, Trio GEFD1 exchange activity is not affected by filamin binding. Our results indicate that filamin, as a molecular target of Trio, may be a scaffold for the spatial organization of Rho-GTPase-mediated signalling pathways.
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Affiliation(s)
- J M Bellanger
- CRBM-CNRS, UPR 1086, 1919 Route de Mende, 34293 Montpellier Cédex 5, France
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30
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Affiliation(s)
- Gareth E. Jones
- The Randall Centre for Molecular Mechanisms of Cell Function, King’s College London, United Kingdom
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31
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Liu BP, Burridge K. Vav2 activates Rac1, Cdc42, and RhoA downstream from growth factor receptors but not beta1 integrins. Mol Cell Biol 2000; 20:7160-9. [PMID: 10982832 PMCID: PMC86269 DOI: 10.1128/mcb.20.19.7160-7169.2000] [Citation(s) in RCA: 174] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Rho family of GTPases plays a major role in the organization of the actin cytoskeleton. These G proteins are activated by guanine nucleotide exchange factors that stimulate the exchange of bound GDP for GTP. In their GTP-bound state, these G proteins interact with downstream effectors. Vav2 is an exchange factor for Rho family GTPases. It is a ubiquitously expressed homologue of Vav1, and like Vav1, it has previously been shown to be activated by tyrosine phosphorylation. Because Vav1 becomes tyrosine phosphorylated and activated following integrin engagement in hematopoietic cells, we investigated the tyrosine phosphorylation of Vav2 in response to integrin-mediated adhesion in fibroblasts and epithelial cells. However, no tyrosine phosphorylation of Vav2 was detected in response to integrin engagement. In contrast, treating cells with either epidermal growth factor or platelet-derived growth factor stimulated tyrosine phosphorylation of Vav2. We have examined the effects of overexpressing either wild-type or amino-terminally truncated (constitutively active) forms of Vav2 as fusion proteins with green fluorescent protein. Overexpression of either wild-type or constitutively active Vav2 resulted in prominent membrane ruffles and enhanced stress fibers. These cells revealed elevated rates of cell migration that were inhibited by expression of dominant negative forms of Rac1 and Cdc42. Using a binding assay to measure the activity of Rac1, Cdc42, and RhoA, we found that overexpression of Vav2 resulted in increased activity of each of these G proteins. Expression of a carboxy-terminal fragment of Vav2 decreased the elevation of Rac1 activity induced by epidermal growth factor, consistent with Vav2 mediating activation of Rac1 downstream from growth factor receptors.
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Affiliation(s)
- B P Liu
- Department of Cell Biology and Anatomy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7090, USA.
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32
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Affiliation(s)
- A Ridley
- Ludwig Institute for Cancer Research, Royal Free and University College Medical School Branch, London W1P 8BT, United Kingdom.
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33
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Garrett WS, Chen LM, Kroschewski R, Ebersold M, Turley S, Trombetta S, Galán JE, Mellman I. Developmental control of endocytosis in dendritic cells by Cdc42. Cell 2000; 102:325-34. [PMID: 10975523 DOI: 10.1016/s0092-8674(00)00038-6] [Citation(s) in RCA: 351] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Dendritic cells (DCs) developmentally regulate antigen uptake by controlling their endocytic capacity. Immature DCs actively internalize antigen. However, mature DCs are poorly endocytic, functioning instead to present antigens to T cells. We have found that endocytic downregulation reflects a decrease in endocytic activity controlled by Rho family GTPases, especially Cdc42. Blocking Cdc42 function by Toxin B treatment or injection of dominant-negative inhibitors of Cdc42 abrogates endocytosis in immature DCs. In mature DCs, injection of constitutively active Cdc42 or microbial delivery of a Cdc42 nucleotide exchange factor reactivates endocytosis. DCs regulate endogenous levels of Cdc42-GTP with activated Cdc42 detectable only in immature cells. We conclude that DCs developmentally regulate endocytosis at least in part by controlling levels of activated Cdc42.
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Affiliation(s)
- W S Garrett
- Department of Cell Biology, Ludwig Institute for Cancer Research, Yale University School of Medicine, New Haven, Connecticut 06520, USA
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34
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Prokopenko SN, Saint R, Bellen HJ. Untying the Gordian knot of cytokinesis. Role of small G proteins and their regulators. J Cell Biol 2000; 148:843-8. [PMID: 10704435 PMCID: PMC2174545 DOI: 10.1083/jcb.148.5.843] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Affiliation(s)
- S N Prokopenko
- Program in Developmental Biology, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA.
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35
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Reid T, Bathoorn A, Ahmadian MR, Collard JG. Identification and characterization of hPEM-2, a guanine nucleotide exchange factor specific for Cdc42. J Biol Chem 1999; 274:33587-93. [PMID: 10559246 DOI: 10.1074/jbc.274.47.33587] [Citation(s) in RCA: 98] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Guanine nucleotide exchange factors of the Dbl family regulate the actin cytoskeleton through activation of Rho-like GTPases. At present the Dbl family consists of more than thirty members; many have not been phenotypically or biochemically characterized. Guanine nucleotide exchange factors universally feature a Dbl homology domain followed by a pleckstrin homology domain. Employing data base screening we identified a recently cloned cDNA, KIAA0424, showing substantial sequence homology with Rac activators such as Tiam1, Sos, Vav, and PIX within the catalytic domain. This cDNA appears to be the human homologue of the Ascidian protein Posterior End Mark-2 (PEM-2). We refer to this exchanger as hPEM-2. hPEM-2 encodes a protein of 70 kDa and features an N-terminal src homology 3 domain, followed by tandem Dbl homology and pleckstrin homology domains. The gene is highly expressed in brain and is localized on the human X-chromosome. Employing biochemical activity assays for Rho-like GTPases we found that hPEM-2 specifically activates Cdc42 and not Rac or RhoA. Ectopic expression of hPEM-2 in NIH3T3 fibroblasts revealed a Cdc42 phenotype featuring filopodia formation, followed by cortical actin polymerization and cell rounding. hPEM-2 represents an exchange factor, which may have a role in the regulation of a number of cellular processes through Cdc42.
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Affiliation(s)
- T Reid
- Division of Cell Biology, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
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