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β-Arrestin2 Is Critically Involved in the Differential Regulation of Phosphosignaling Pathways by Thyrotropin-Releasing Hormone and Taltirelin. Cells 2022; 11:cells11091473. [PMID: 35563779 PMCID: PMC9103620 DOI: 10.3390/cells11091473] [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: 03/05/2022] [Revised: 04/22/2022] [Accepted: 04/25/2022] [Indexed: 12/17/2022] Open
Abstract
In recent years, thyrotropin-releasing hormone (TRH) and its analogs, including taltirelin (TAL), have demonstrated a range of effects on the central nervous system that represent potential therapeutic agents for the treatment of various neurological disorders, including neurodegenerative diseases. However, the molecular mechanisms of their actions remain poorly understood. In this study, we investigated phosphosignaling dynamics in pituitary GH1 cells affected by TRH and TAL and the putative role of β-arrestin2 in mediating these effects. Our results revealed widespread alterations in many phosphosignaling pathways involving signal transduction via small GTPases, MAP kinases, Ser/Thr- and Tyr-protein kinases, Wnt/β-catenin, and members of the Hippo pathway. The differential TRH- or TAL-induced phosphorylation of numerous proteins suggests that these ligands exhibit some degree of biased agonism at the TRH receptor. The different phosphorylation patterns induced by TRH or TAL in β-arrestin2-deficient cells suggest that the β-arrestin2 scaffold is a key factor determining phosphorylation events after TRH receptor activation. Our results suggest that compounds that modulate kinase and phosphatase activity can be considered as additional adjuvants to enhance the potential therapeutic value of TRH or TAL.
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2
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Abstract
Cell migration, a crucial step in numerous biological processes, is tightly regulated in space and time. Cells employ Rho GTPases, primarily Rho, Rac, and Cdc42, to regulate their motility. Like other small G proteins, Rho GTPases function as biomolecular switches in regulating cell migration by operating between GDP bound 'OFF' and GTP bound 'ON' states. Guanine nucleotide exchange factors (GEFs) catalyse the shuttling of GTPases from OFF to ON state. G protein-coupled receptors (GPCRs) are the largest family of cell surface receptors that are involved in many signalling phenomena including cell survival and cell migration events. In this review, we summarize signalling mechanisms, involving GPCRs, leading to the activation of RhoGEFs. GPCRs exhibit diverse GEF activation modes that include the interaction of heterotrimeric G protein subunits with different domains of GEFs, phosphorylation, protein-protein interaction, protein-lipid interaction, and/or a combination of these processes.
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Affiliation(s)
- Aishwarya Omble
- Division of Biochemical Sciences, CSIR-National Chemical Laboratory, Pune, India,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
| | - Kiran Kulkarni
- Division of Biochemical Sciences, CSIR-National Chemical Laboratory, Pune, India,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India,CONTACT Kiran Kulkarni Academy of Scientific and Innovative Research (Acsir), Ghaziabad 201002, India
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3
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Rac-dependent feedforward autoactivation of NOX2 leads to oxidative burst. J Biol Chem 2021; 297:100982. [PMID: 34293347 PMCID: PMC8353492 DOI: 10.1016/j.jbc.2021.100982] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2021] [Revised: 07/09/2021] [Accepted: 07/17/2021] [Indexed: 12/03/2022] Open
Abstract
NADPH oxidase 2 (NOX2) produces the superoxide anion radical (O2−), which has functions in both cell signaling and immune defense. NOX2 is a multimeric-protein complex consisting of several protein subunits including the GTPase Rac. NOX2 uniquely facilitates an oxidative burst, which is described by initially slow O2− production, which increases over time. The NOX2 oxidative burst is considered critical to immune defense because it enables expedited O2− production in response to infections. However, the mechanism of the initiation and progression of this oxidative burst and its implications for regulation of NOX2 have not been clarified. In this study, we show that the NOX2 oxidative burst is a result of autoactivation of NOX2 coupled with the redox function of Rac. NOX2 autoactivation begins when active Rac triggers NOX2 activation and the subsequent production of O2−, which in turn activates redox-sensitive Rac. This activated Rac further activates NOX2, amplifying the feedforward cycle and resulting in a NOX2-mediated oxidative burst. Using mutagenesis-based kinetic and cell analyses, we show that enzymatic activation of Rac is exclusively responsible for production of the active Rac trigger that initiates NOX2 autoactivation, whereas redox-mediated Rac activation is the main driving force of NOX2 autoactivation and contributes to generation of ∼98% of the active NOX2 in cells. The results of this study provide insight into the regulation of NOX2 function, which could be used to develop therapeutics to control immune responses associated with dysregulated NOX2 oxidative bursts.
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4
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Fray MA, Charpentier JC, Sylvain NR, Seminario MC, Bunnell SC. Vav2 lacks Ca 2+ entry-promoting scaffolding functions unique to Vav1 and inhibits T cell activation via Cdc42. J Cell Sci 2020; 133:jcs238337. [PMID: 31974114 PMCID: PMC7075049 DOI: 10.1242/jcs.238337] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Accepted: 01/06/2020] [Indexed: 12/16/2022] Open
Abstract
Vav family guanine nucleotide exchange factors (GEFs) are essential regulators of immune function. Despite their structural similarity, Vav1 promotes and Vav2 opposes T cell receptor (TCR)-induced Ca2+ entry. By using a Vav1-deficient Jurkat T cell line, we find that Vav1 facilitates Ca2+ entry via non-catalytic scaffolding functions that are encoded by the catalytic core of Vav1 and flanking linker regions. We implicate, in this scaffolding function, a previously undescribed polybasic motif that is strictly conserved in Vav1 and absent from Vav2 in tetrapods. Conversely, the catalytic activity of Vav2 contributes to the suppression of TCR-mediated Ca2+ entry. By performing an in vivo 'GEF trapping' assay in intact cells, we demonstrate that Cdc42 interacts with the catalytic surface of Vav2 but not Vav1, and that Vav1 discriminates Cdc42 from Rac1 via F56 (W56 in Rac1). Finally, the Cdc42-specific inhibitor ZCL278 and the shRNA-mediated suppression of Cdc42 each prevent the inhibition of TCR-induced Ca2+ entry by Vav2. These findings define stark differences in the functions of Vav1 and Vav2, and provide an explanation for the differential usage of these Vav isoforms by immune subpopulations.
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Affiliation(s)
- Michael A Fray
- Program in Immunology, Department of Immunology, Tufts University School of Medicine, Boston, MA 02111, USA
| | - John C Charpentier
- Department of Biology, University of Massachusetts Boston, Boston, MA 02125, USA
| | - Nicholas R Sylvain
- Program in Immunology, Department of Immunology, Tufts University School of Medicine, Boston, MA 02111, USA
| | - Maria-Cristina Seminario
- Program in Immunology, Department of Immunology, Tufts University School of Medicine, Boston, MA 02111, USA
| | - Stephen C Bunnell
- Program in Immunology, Department of Immunology, Tufts University School of Medicine, Boston, MA 02111, USA
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5
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Xu Z, Gakhar L, Bain FE, Spies M, Fuentes EJ. The Tiam1 guanine nucleotide exchange factor is auto-inhibited by its pleckstrin homology coiled-coil extension domain. J Biol Chem 2017; 292:17777-17793. [PMID: 28882897 PMCID: PMC5663878 DOI: 10.1074/jbc.m117.799114] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Revised: 08/25/2017] [Indexed: 12/22/2022] Open
Abstract
T-cell lymphoma invasion and metastasis 1 (Tiam1) is a Dbl-family guanine nucleotide exchange factor (GEF) that specifically activates the Rho-family GTPase Rac1 in response to upstream signals, thereby regulating cellular processes including cell adhesion and migration. Tiam1 contains multiple domains, including an N-terminal pleckstrin homology coiled-coiled extension (PHn-CC-Ex) and catalytic Dbl homology and C-terminal pleckstrin homology (DH-PHc) domain. Previous studies indicate that larger fragments of Tiam1, such as the region encompassing the N-terminal to C-terminal pleckstrin homology domains (PHn-PHc), are auto-inhibited. However, the domains in this region responsible for inhibition remain unknown. Here, we show that the PHn-CC-Ex domain inhibits Tiam1 GEF activity by directly interacting with the catalytic DH-PHc domain, preventing Rac1 binding and activation. Enzyme kinetics experiments suggested that Tiam1 is auto-inhibited through occlusion of the catalytic site rather than by allostery. Small angle X-ray scattering and ensemble modeling yielded models of the PHn-PHc fragment that indicate it is in equilibrium between "open" and "closed" conformational states. Finally, single-molecule experiments support a model in which conformational sampling between the open and closed states of Tiam1 contributes to Rac1 dissociation. Our results highlight the role of the PHn-CC-Ex domain in Tiam1 GEF regulation and suggest a combinatorial model for GEF inhibition and activation of the Rac1 signaling pathway.
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Affiliation(s)
- Zhen Xu
- From the Department of Biochemistry
| | - Lokesh Gakhar
- From the Department of Biochemistry
- Protein Crystallography Facility, and
| | | | - Maria Spies
- From the Department of Biochemistry
- Holden Comprehensive Cancer Center, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242
| | - Ernesto J Fuentes
- From the Department of Biochemistry,
- Holden Comprehensive Cancer Center, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242
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6
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7
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Li JJ, Sun ZJ, Yuan YM, Yin FF, Bian YG, Long LY, Zhang XL, Xie D. EphB3 Stimulates Cell Migration and Metastasis in a Kinase-dependent Manner through Vav2-Rho GTPase Axis in Papillary Thyroid Cancer. J Biol Chem 2016; 292:1112-1121. [PMID: 27986811 DOI: 10.1074/jbc.m116.750349] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Revised: 11/28/2016] [Indexed: 12/18/2022] Open
Abstract
Eph receptors, the largest subfamily of transmembrane tyrosine kinase receptors, have been increasingly implicated in various physiologic and pathologic processes, and the roles of the Eph family members during tumorigenesis have recently attracted growing attentions. In the present study, we explored the function of EphB3, one member of Eph family, in papillary thyroid cancer (PTC). We found that the expression of EphB3 was significantly elevated in PTC. Either overexpression of EphB3 or activation of EphB3 by EfnB1-Fc/EfnB2-Fc stimulated in vitro migration of PTC cells. In contrast, siRNA-mediated knockdown of EphB3 or EphB3-Fc treatment, which only blocked EphB3-mediated forward signaling, inhibited migration and metastasis of PTC cells. A mechanism study revealed that EphB3 knockdown led to suppressed activity of Rac1 and enhanced activity of RhoA. Moreover, we found that Vav2, an important regulator of Rho family GTPases, was activated by EphB3 in a kinase-dependent manner. Altogether, our work suggested that EphB3 acted as a tumor promoter in PTC by increasing the in vitro migration as well as the in vivo metastasis of PTC cells through regulating the activities of Vav2 and Rho GTPases in a kinase-dependent manner.
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Affiliation(s)
- Jing-Jing Li
- From the Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China and
| | - Zhi-Jian Sun
- From the Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China and
| | - Yan-Mei Yuan
- From the Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China and
| | - Fen-Fen Yin
- From the Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China and
| | - Yao-Gang Bian
- the Department of General Surgery, Fengxian Hospital Affiliated to Southern Medical University, 6600 Nanfeng Road, Shanghai 201499, China
| | - Ling-Yun Long
- From the Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China and
| | - Xue-Li Zhang
- the Department of General Surgery, Fengxian Hospital Affiliated to Southern Medical University, 6600 Nanfeng Road, Shanghai 201499, China
| | - Dong Xie
- From the Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China and
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8
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Shin JY, Wey M, Umutesi HG, Sun X, Simecka J, Heo J. Thiopurine Prodrugs Mediate Immunosuppressive Effects by Interfering with Rac1 Protein Function. J Biol Chem 2016; 291:13699-714. [PMID: 27189938 DOI: 10.1074/jbc.m115.694422] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2015] [Indexed: 12/19/2022] Open
Abstract
6-Thiopurine (6-TP) prodrugs include 6-thioguanine and azathioprine. Both are widely used to treat autoimmune disorders and certain cancers. This study showed that a 6-thioguanosine triphosphate (6-TGTP), converted in T-cells from 6-TP, targets Rac1 to form a disulfide adduct between 6-TGTP and the redox-sensitive GXXXXGK(S/T)C motif of Rac1. This study also showed that, despite the conservation of the catalytic activity of RhoGAP (Rho-specific GAP) on the 6-TGTP-Rac1 adduct to produce the biologically inactive 6-thioguanosine diphosphate (6-TGDP)-Rac1 adduct, RhoGEF (Rho-specific GEF) cannot exchange the 6-TGDP adducted on Rac1 with free guanine nucleotide. The biologically inactive 6-TGDP-Rac1 adduct accumulates in cells because of the ongoing combined actions of RhoGEF and RhoGAP. Because other Rho GTPases, such as RhoA and Cdc42, also possess the GXXXXGK(S/T)C motif, the proposed mechanism for the inactivation of Rac1 also applies to RhoA and Cdc42. However, previous studies have shown that CD3/CD28-stimulated T-cells contain more activated Rac1 than other Rho GTPases such as RhoA and Cdc42. Accordingly, Rac1 is the main target of 6-TP in activated T-cells. This explains the T-cell-specific Rac1-targeting therapeutic action of 6-TP that suppresses the immune response. This proposed mechanism for the action of 6-TP on Rac1 performs a critical role in demonstrating the capability to design a Rac1-targeting chemotherapeutic agent(s) for autoimmune disorders. Nevertheless, the results also suggest that the targeting action of other Rho GTPases in other organ cells, such as RhoA in vascular cells, may be linked to cytotoxicities because RhoA plays a key role in vasculature functions.
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Affiliation(s)
- Jin-Young Shin
- From the Department of Chemistry and Biochemistry, University of Texas at Arlington, Arlington, Texas 76019
| | - Michael Wey
- From the Department of Chemistry and Biochemistry, University of Texas at Arlington, Arlington, Texas 76019
| | - Hope G Umutesi
- From the Department of Chemistry and Biochemistry, University of Texas at Arlington, Arlington, Texas 76019
| | - Xiangle Sun
- the Department of Cell Biology and Immunology, University of North Texas Health Science Center, Fort Worth, Texas 76107, and
| | - Jerry Simecka
- the Department of Cell Biology and Immunology, University of North Texas Health Science Center, Fort Worth, Texas 76107, and the Department of Pharmaceutical Sciences, UNT System College of Pharmacy, University of North Texas Health Science Center, Fort Worth, Texas 76107
| | - Jongyun Heo
- From the Department of Chemistry and Biochemistry, University of Texas at Arlington, Arlington, Texas 76019,
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9
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Wey M, Lee J, Kim HS, Jeong SS, Kim J, Heo J. Kinetic Mechanism of Formation of Hyperactive Embryonic Ras in Cells. Biochemistry 2016; 55:543-59. [PMID: 26765051 DOI: 10.1021/acs.biochem.5b00902] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Embryonic Ras (ERas)--a new subset of Ras proteins--are characterized by a unique p-loop residue, unique Switch II residues, and an unusual extended N-terminus. When expressed, both murine and human ERas are highly populated in their GTP-bound forms. The expression of murine ERas is linked to the development of murine embryonic cells, and the expression of human ERas is correlated to certain human cancers. Mutation-based kinetic analyses, in combination with assessments of the kinetic parameter-based calculation of the fraction of the GTP-bound active form of ERas proteins, explain the kinetic mechanism that produces the unprecedented hyperactive ERas. The ERas-specific p-loop residue contributes ERas proteins to intrinsically populate their GTP-bound form in cells. Furthermore, the ERas-specific Switch II residues block the catalytic action of p120GAP on ERas proteins. This blockage sustains the previously mentioned GTP-bound ERas proteins. In essence, the combined work of the ERas-specific p-loop and Switch II residues populates the exceedingly high GTP-bound form of ERas in cells. This study also rules out any kinetic function of the unique ERas-specific N-terminus in the production of the hyperactive GTP-bound ERas in cells. The biological role of this N-terminus remains uninvestigated. Intriguingly, the ERas-specific p-loop residue matches the mutated Ser residue of the Costello Syndrome G12S HRas mutant that also intrinsically populates its GTP-bound form in cells. However, because the effector protein of ERas differs from that of G12S HRas, this kinetic similarity does not confer on ERas biological and/or pathophysiological similarity to G12S HRas.
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Affiliation(s)
- Michael Wey
- Department of Chemistry and Biochemistry, The University of Texas at Arlington , Arlington, Texas 76019, United States
| | - Jungwoon Lee
- Department of Life Science, Sogang University , Seoul 121-742, Korea
| | - Hyo Sun Kim
- Department of Life Science, Sogang University , Seoul 121-742, Korea
| | - Soon Seog Jeong
- Humanzyme , 2201 West Campbell Park Drive, Chicago, Illinois 60612, United States
| | - Jungho Kim
- Department of Life Science, Sogang University , Seoul 121-742, Korea
| | - Jongyun Heo
- Department of Chemistry and Biochemistry, The University of Texas at Arlington , Arlington, Texas 76019, United States
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10
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Zhang C, Liu J, Zhao Y, Yue X, Zhu Y, Wang X, Wu H, Blanco F, Li S, Bhanot G, Haffty BG, Hu W, Feng Z. Glutaminase 2 is a novel negative regulator of small GTPase Rac1 and mediates p53 function in suppressing metastasis. eLife 2016; 5:e10727. [PMID: 26751560 PMCID: PMC4749555 DOI: 10.7554/elife.10727] [Citation(s) in RCA: 77] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Accepted: 12/06/2015] [Indexed: 01/13/2023] Open
Abstract
Glutaminase (GLS) isoenzymes GLS1 and GLS2 are key enzymes for glutamine metabolism. Interestingly, GLS1 and GLS2 display contrasting functions in tumorigenesis with elusive mechanism; GLS1 promotes tumorigenesis, whereas GLS2 exhibits a tumor-suppressive function. In this study, we found that GLS2 but not GLS1 binds to small GTPase Rac1 and inhibits its interaction with Rac1 activators guanine-nucleotide exchange factors, which in turn inhibits Rac1 to suppress cancer metastasis. This function of GLS2 is independent of GLS2 glutaminase activity. Furthermore, decreased GLS2 expression is associated with enhanced metastasis in human cancer. As a p53 target, GLS2 mediates p53's function in metastasis suppression through inhibiting Rac1. In summary, our results reveal that GLS2 is a novel negative regulator of Rac1, and uncover a novel function and mechanism whereby GLS2 suppresses metastasis. Our results also elucidate a novel mechanism that contributes to the contrasting functions of GLS1 and GLS2 in tumorigenesis.
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Affiliation(s)
- Cen Zhang
- Department of Radiation Oncology, Rutgers Cancer Institute of New Jersey, Rutgers, The State University of New Jersey, New Brunswick, United States
| | - Juan Liu
- Department of Radiation Oncology, Rutgers Cancer Institute of New Jersey, Rutgers, The State University of New Jersey, New Brunswick, United States
| | - Yuhan Zhao
- Department of Radiation Oncology, Rutgers Cancer Institute of New Jersey, Rutgers, The State University of New Jersey, New Brunswick, United States
| | - Xuetian Yue
- Department of Radiation Oncology, Rutgers Cancer Institute of New Jersey, Rutgers, The State University of New Jersey, New Brunswick, United States
| | - Yu Zhu
- Department of Radiation Oncology, Rutgers Cancer Institute of New Jersey, Rutgers, The State University of New Jersey, New Brunswick, United States.,Department of Neurosurgery, First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Xiaolong Wang
- Department of Radiation Oncology, Rutgers Cancer Institute of New Jersey, Rutgers, The State University of New Jersey, New Brunswick, United States
| | - Hao Wu
- Department of Radiation Oncology, Rutgers Cancer Institute of New Jersey, Rutgers, The State University of New Jersey, New Brunswick, United States
| | - Felix Blanco
- Department of Radiation Oncology, Rutgers Cancer Institute of New Jersey, Rutgers, The State University of New Jersey, New Brunswick, United States
| | - Shaohua Li
- Department of Surgery, Robert Wood Johnson Medical School, Rutgers, The State University of New Jersey, New Brunswick, United States
| | - Gyan Bhanot
- Department of Molecular Biology, Biochemistry & Physics, Rutgers, The State University of New Jersey, Piscataway, United States
| | - Bruce G Haffty
- Department of Radiation Oncology, Rutgers Cancer Institute of New Jersey, Rutgers, The State University of New Jersey, New Brunswick, United States
| | - Wenwei Hu
- Department of Radiation Oncology, Rutgers Cancer Institute of New Jersey, Rutgers, The State University of New Jersey, New Brunswick, United States
| | - Zhaohui Feng
- Department of Radiation Oncology, Rutgers Cancer Institute of New Jersey, Rutgers, The State University of New Jersey, New Brunswick, United States
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11
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Regulation of sarcoma cell migration, invasion and invadopodia formation by AFAP1L1 through a phosphotyrosine-dependent pathway. Oncogene 2015. [DOI: 10.1038/onc.2015.272] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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12
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Rac1 modification by an electrophilic 15-deoxy Δ(12,14)-prostaglandin J2 analog. Redox Biol 2015; 4:346-54. [PMID: 25677088 PMCID: PMC4326178 DOI: 10.1016/j.redox.2015.01.016] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2014] [Revised: 01/29/2015] [Accepted: 01/30/2015] [Indexed: 11/24/2022] Open
Abstract
Vascular endothelial cells (ECs) are important for maintaining vascular homeostasis. Dysfunction of ECs contributes to cardiovascular diseases, including atherosclerosis, and can impair the healing process during vascular injury. An important mediator of EC response to stress is the GTPase Rac1. Rac1 responds to extracellular signals and is involved in cytoskeletal rearrangement, reactive oxygen species generation and cell cycle progression. Rac1 interacts with effector proteins to elicit EC spreading and formation of cell-to-cell junctions. Rac1 activity has recently been shown to be modulated by glutathiolation or S-nitrosation via an active site cysteine residue. However, it is not known whether other redox signaling compounds can modulate Rac1 activity. An important redox signaling mediator is the electrophilic lipid, 15-deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2). This compound is a downstream product of cyclooxygenase and forms covalent adducts with specific cysteine residues, and induces cellular signaling in a pleiotropic manner. In this study, we demonstrate that a biotin-tagged analog of 15d-PGJ2 (bt-15d-PGJ2) forms an adduct with Rac1 in vitro at the C157 residue, and an additional adduct was detected on the tryptic peptide associated with C178. Rac1 modification in addition to modulation of Rac1 activity by bt-15d-PGJ2 was observed in cultured ECs. In addition, decreased EC migration and cell spreading were observed in response to the electrophile. These results demonstrate for the first time that Rac1 is a target for 15d-PGJ2 in ECs, and suggest that Rac1 modification by electrophiles such as 15d-PGJ2 may alter redox signaling and EC function. • Recombinant Rac1 is modified by bt-15d-PGJ2 at C157 in vitro. • Rac1 is modified by bt-15d-PGJ2 in bovine aortic endothelial cells. • Rac1 activity is transiently stimulated by bt-15d-PGJ2. • 15d-PGJ2 inhibits endothelial cell migration and spreading.
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13
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Abstract
Spatio-temporal control of RhoA GTPase is critical for regulation of cell migration, attachment to extracellular matrix, and cell-cell adhesions. Activation of RhoA is mediated by guanine nucleotide exchange factors (GEFs), a diverse family of enzymes that are controlled by multiple signaling pathways regulating actin cytoskeleton and cell migration. GEFs can be regulated by different mechanisms. Growing evidence demonstrates that phosphorylation serves as one of the predominant signals controlling activity, interactions, and localization of RhoGEFs. It acts as a positive and a negative regulator, and allows for regulation of RhoGEFs by multiple signaling cascades. Although there are common trends in phosphorylation-mediated regulation of some RhoGEF homologs, the majority of GEFs utilize distinct mechanisms that are dictated by their unique structure and interaction networks. This diversity enables multiple signaling pathways to use different RhoGEFs for regulation of a single central-RhoA. Here, we review current examples of phosphorylation-mediated regulation of GEFs for RhoA and its role in cell migration, discuss mechanisms, and provide insights into potential future directions.
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Affiliation(s)
- Maulik Patel
- Department of Pharmacology; University of Illinois at Chicago; Chicago, IL USA
| | - Andrei V Karginov
- Department of Pharmacology; University of Illinois at Chicago; Chicago, IL USA
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14
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Geczy T, Peach ML, El Kazzouli S, Sigano DM, Kang JH, Valle CJ, Selezneva J, Woo W, Kedei N, Lewin NE, Garfield SH, Lim L, Mannan P, Marquez VE, Blumberg PM. Molecular basis for failure of "atypical" C1 domain of Vav1 to bind diacylglycerol/phorbol ester. J Biol Chem 2012; 287:13137-58. [PMID: 22351766 DOI: 10.1074/jbc.m111.320010] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
C1 domains, the recognition motif of the second messenger diacylglycerol and of the phorbol esters, are classified as typical (ligand-responsive) or atypical (not ligand-responsive). The C1 domain of Vav1, a guanine nucleotide exchange factor, plays a critical role in regulation of Vav activity through stabilization of the Dbl homology domain, which is responsible for exchange activity of Vav. Although the C1 domain of Vav1 is classified as atypical, it retains a binding pocket geometry homologous to that of the typical C1 domains of PKCs. This study clarifies the basis for its failure to bind ligands. Substituting Vav1-specific residues into the C1b domain of PKCδ, we identified five crucial residues (Glu(9), Glu(10), Thr(11), Thr(24), and Tyr(26)) along the rim of the binding cleft that weaken binding potency in a cumulative fashion. Reciprocally, replacing these incompatible residues in the Vav1 C1 domain with the corresponding residues from PKCδ C1b (δC1b) conferred high potency for phorbol ester binding. Computer modeling predicts that these unique residues in Vav1 increase the hydrophilicity of the rim of the binding pocket, impairing membrane association and thereby preventing formation of the ternary C1-ligand-membrane binding complex. The initial design of diacylglycerol-lactones to exploit these Vav1 unique residues showed enhanced selectivity for C1 domains incorporating these residues, suggesting a strategy for the development of ligands targeting Vav1.
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Affiliation(s)
- Tamas Geczy
- Laboratory of Cancer Biology and Genetics, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892, USA
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15
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Essential role for vav Guanine nucleotide exchange factors in brain-derived neurotrophic factor-induced dendritic spine growth and synapse plasticity. J Neurosci 2011; 31:12426-36. [PMID: 21880903 DOI: 10.1523/jneurosci.0685-11.2011] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Brain-derived neurotrophic factor (BDNF) and its cognate receptor, TrkB, regulate a wide range of cellular processes, including dendritic spine formation and functional synapse plasticity. However, the signaling mechanisms that link BDNF-activated TrkB to F-actin remodeling enzymes and dendritic spine morphological plasticity remain poorly understood. We report here that BDNF/TrkB signaling in neurons activates the Vav family of Rac/RhoA guanine nucleotide exchange factors through a novel TrkB-dependent mechanism. We find that Vav is required for BDNF-stimulated Rac-GTP production in cortical and hippocampal neurons. Vav is partially enriched at excitatory synapses in the postnatal hippocampus but does not appear to be required for normal dendritic spine density. Rather, we observe significant reductions in both BDNF-induced, rapid, dendritic spine head growth and in CA3-CA1 theta burst-stimulated long-term potentiation in Vav-deficient mouse hippocampal slices, suggesting that Vav-dependent regulation of dendritic spine morphological plasticity facilitates normal functional synapse plasticity.
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16
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Heo J, Wey M, Hong I. Insight into the 6-thiopurine-mediated termination of the invasive motility of tumor cells derived from inflammatory breast cancer. Biochemistry 2011; 50:5731-42. [PMID: 21568348 DOI: 10.1021/bi200347y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Our study showed that a combination of 6-thiopurine (6-TP) drugs and a redox agent effectively inhibits the motility of SUM cells derived from human inflammatory breast cancer (IBC) cells and RhoC-overexpressed mammary epithelium cells. This 6-TP-mediated inhibition of cell motility occurs because the treated 6-TPs target and inactivate RhoC. A molecular mechanism for inactivation by the 6-TP-mediated RhoC is proposed by which treated TPs are converted in cells into 6-thioguanosine phosphate (6-TGNP). This 6-TGNP in turn reacts with the Cys(20) side chain of the redox-sensitive GXXXCGK(S/T)C motif of RhoC to produce a 6-TGNP-RhoC disulfide adduct. A redox agent synergistically enhances the formation process of this disulfide. The adduct that is formed impedes RhoC guanine nucleotide exchange, which populates an inactive RhoC. Our results suggest that 6-TGNP can also react with the redox-sensitive GXXXCGK(S/T)C and GXXXXGK(S/T)C motif of RhoA and Rac, respectively, to produce a 6-TGNP-RhoA and 6-TGNP-Rac disulfide adduct. However, given that RhoC has been shown to be overexpressed in ∼90% of IBC lesions, the populated RhoC but not other Rho proteins is likely to be a primary target for 6-TPs and a redox agent to terminate the metastasis of IBC.
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Affiliation(s)
- Jongyun Heo
- Department of Chemistry and Biochemistry, The University of Texas at Arlington, Arlington, Texas 76019, USA.
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17
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Heo J. Redox control of GTPases: from molecular mechanisms to functional significance in health and disease. Antioxid Redox Signal 2011; 14:689-724. [PMID: 20649471 DOI: 10.1089/ars.2009.2984] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Small GTPases, including the proto-oncoprotein Ras and Rho GTPases, are involved in various cellular signaling events. Some of these small GTPases are redox sensitive, including Ras, Rho, Ran, Dexras1, and Rhes GTPases. Thus, the redox-mediated regulation of these GTPases often determines the course of their cellular signaling cascades. This article takes into consideration the application of Marcus theory to potential redox-based molecular mechanisms in the regulation of these redox-sensitive GTPases and the relevance of such mechanisms to a specific redox-sensitive motif. The discussion also takes into account various diseases, including cancers, heart, and neuronal disorders, that are often linked with the dysregulation of the redox signaling cascades associated with these redox-sensitive GTPases.
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Affiliation(s)
- Jongyun Heo
- Department of Chemistry and Biochemistry, The University of Texas at Arlington, Arlington, Texas 76019, USA.
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18
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Guanine nucleotide exchange factors for RhoGTPases: good therapeutic targets for cancer therapy? Cell Signal 2010; 23:969-79. [PMID: 21044680 DOI: 10.1016/j.cellsig.2010.10.022] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2010] [Accepted: 10/23/2010] [Indexed: 12/12/2022]
Abstract
Rho guanosine triphosphatases (GTPases) are a family of small proteins which function as molecular switches in a variety of signaling pathways following stimulation of cell surface receptors. RhoGTPases regulate numerous cellular processes including cytoskeleton organization, gene transcription, cell proliferation, migration, growth and cell survival. Because of their central role in regulating processes that are dysregulated in cancer, it seems reasonable that defects in the RhoGTPase pathway may be involved in the development of cancer. RhoGTPase activity is regulated by a number of protein families: guanine nucleotide exchange factors (GEFs), GTPase activating proteins (GAPs) and guanine nucleotide-dissociation inhibitors (GDIs). This review discusses the participation of RhoGTPases and their regulators, especially GEFs in human cancers. In particular, we focus on the involvement of the RhoGTPase GEF, Vav1, a hematopoietic specific signal transducer which is involved in human neuroblastoma, pancreatic ductal carcinoma and lung cancer. Finally, we summarize recent advances in the design and application of a number of molecules that specifically target individual RhoGTPases or their regulators or effectors, and discuss their potential for cancer therapy.
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19
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Malhotra S, Kovats S, Zhang W, Coggeshall KM. Vav and Rac activation in B cell antigen receptor endocytosis involves Vav recruitment to the adapter protein LAB. J Biol Chem 2009; 284:36202-36212. [PMID: 19858206 PMCID: PMC2794736 DOI: 10.1074/jbc.m109.040089] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2009] [Revised: 09/14/2009] [Indexed: 11/06/2022] Open
Abstract
The signal transduction events supporting B cell antigen receptor (BCR) endocytosis are not well understood. We have identified a pathway supporting BCR internalization that begins with tyrosine phosphorylation of the adapter protein LAB. Phosphorylated LAB recruits a complex of Grb2-dynamin and the guanine nucleotide exchange factor Vav. Vav is required for activation of the small GTPases Rac1 and Rac2. All these proteins contribute to (and dynamin, Vav, and Rac1/2 are required for) BCR endocytosis and presentation of antigen to T cells. This is the first description of a sequential signal transduction pathway from BCR to internalization and antigen presentation.
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MESH Headings
- Adaptor Proteins, Vesicular Transport/genetics
- Adaptor Proteins, Vesicular Transport/immunology
- Adaptor Proteins, Vesicular Transport/metabolism
- Animals
- Antigen Presentation/physiology
- B-Lymphocytes/immunology
- B-Lymphocytes/metabolism
- Cell Line, Tumor
- Dynamins/genetics
- Dynamins/immunology
- Dynamins/metabolism
- Endocytosis/physiology
- GRB2 Adaptor Protein/genetics
- GRB2 Adaptor Protein/immunology
- GRB2 Adaptor Protein/metabolism
- Mice
- Mice, Inbred BALB C
- Mice, Knockout
- Neuropeptides/genetics
- Neuropeptides/immunology
- Neuropeptides/metabolism
- Phosphorylation/physiology
- Proto-Oncogene Proteins c-vav/genetics
- Proto-Oncogene Proteins c-vav/immunology
- Proto-Oncogene Proteins c-vav/metabolism
- Receptors, Antigen, B-Cell/genetics
- Receptors, Antigen, B-Cell/immunology
- Receptors, Antigen, B-Cell/metabolism
- Signal Transduction/physiology
- T-Lymphocytes/immunology
- T-Lymphocytes/metabolism
- rac GTP-Binding Proteins/genetics
- rac GTP-Binding Proteins/immunology
- rac GTP-Binding Proteins/metabolism
- rac1 GTP-Binding Protein
- RAC2 GTP-Binding Protein
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Affiliation(s)
- Shikha Malhotra
- Immunobiology and Cancer Program, Oklahoma Medical Research Foundation, and Department of Cell Biology, University of Oklahoma, Oklahoma City, Oklahoma 73104
| | - Susan Kovats
- Arthritis and Immunology Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104
| | - Weiguo Zhang
- Department of Immunology, Duke University Medical Center, Durham, North Carolina 27710
| | - K Mark Coggeshall
- Immunobiology and Cancer Program, Oklahoma Medical Research Foundation, and Department of Cell Biology, University of Oklahoma, Oklahoma City, Oklahoma 73104.
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20
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Zhang J, Dong B, Siminovitch KA. Contributions of Wiskott-Aldrich syndrome family cytoskeletal regulatory adapters to immune regulation. Immunol Rev 2009; 232:175-94. [PMID: 19909364 DOI: 10.1111/j.1600-065x.2009.00846.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Cytoskeletal structure and dynamic rearrangement are integrally involved in coupling external stimuli to the orchestrated network of molecular interactions and cellular responses required for T-cell effector function. Members of the Wiskott-Aldrich syndrome protein (WASp) family are now widely recognized as cytoskeletal scaffolding adapters that coordinate the transmission of stimulatory signals to downstream induction of actin remodeling and cytoskeletal-dependent T-cell responses. In this review, we discuss the structural and functional properties of the WASp family members, with an emphasis on the roles of these proteins in the molecular pathways underpinning T-cell activation. The contributions of WASp family proteins and the cytoskeletal reorganization they evoke to expression of specific T-cell effector functions and the implications of such activity to normal immune responses and to the immunologic deficits manifested by Wiskott-Aldrich syndrome patients are also described.
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Affiliation(s)
- Jinyi Zhang
- Department of Medicine, University of Toronto, Mount Sinai Hospital Samuel Lunenfeld Research Institute, Toronto, ON, Canada
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21
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Yeom HJ, Park JS, Oh MJ, Paul S, Kim JK, Kim SJ, Lee YS, Kang KS, Hwang SY. Expression analysis of early response-related genes in rat liver epithelial cells exposed to thioacetamide in vitro. J Vet Med Sci 2009; 71:719-27. [PMID: 19578279 DOI: 10.1292/jvms.71.719] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Thioacetamide (TA) is a potent hepatotoxicant known to affect liver metabolism, inhibit mRNA transport and induce immune suppression. The genetic mechanism underlining this biological toxic compound is well understood using microarray technology. Thus, we used high-throughput rat genome oligonucleotide microarrays containing approximately 22,000 genes to investigate the genetic components of TA-related cytotoxicity in WB-F344 rat liver epithelial (WB-F344) cells. We treated cells with TA (two concentrations over five time periods, ranging from 1 to 24 hr), isolated total RNA at 1, 3, 6, 12 and 24 hr following TA treatment and hybridized the RNA to microarrays. Clustering analysis distinguished two groups of genes, early (1 and 3 hr) and late (6, 12 and 24 hr) phase genes. In total, 2,129 and 2,348 differentially-expressed genes were identified following treatment with low and high concentrations of TA, respectively. A common set of 1,229 genes that were differentially expressed following treatment with both low (1,000 muM) and high (10,000 muM) concentrations of TA had similar expression patterns. Interestingly, 1,410 genes at the low concentration and 1,858 genes at the high concentration were differentially expressed in the early phases, suggesting that these genes associated with the early response to TA may be useful as early markers of hepatotoxicity.
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Affiliation(s)
- Hye-Jung Yeom
- Department of Biochemistry, Hanyang University & GenoCheck Co., Ltd., Sangrok-gu, Ansan, Gyeonggi-do 426-791, South Korea
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22
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Sharma S, Orlowski G, Song W. Btk regulates B cell receptor-mediated antigen processing and presentation by controlling actin cytoskeleton dynamics in B cells. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2009; 182:329-39. [PMID: 19109164 PMCID: PMC2855895 DOI: 10.4049/jimmunol.182.1.329] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The high efficiency of Ag processing and presentation by B cells requires Ag-induced BCR signaling and actin cytoskeleton reorganization, although the underlying mechanism for such requirements remains elusive. In this study, we identify Bruton's tyrosine kinase (Btk) as a linker connecting BCR signaling to actin dynamics and the Ag transport pathway. Using xid mice and a Btk inhibitor, we show that BCR engagement increases actin polymerization and Wiskott-Aldrich syndrome protein activation in a Btk-dependent manner. Concurrently, we observe Btk-dependent increases in the levels of phosphatidylinositide-4,5-bisphosphate and phosphorylated Vav upon BCR engagement. The rate of BCR internalization, its movement to late endosomes, and efficiency of BCR-mediated Ag processing and presentation are significantly reduced in both xid and Btk inhibitor-treated B cells. Thus, Btk regulates actin dynamics and Ag transport by activating Wiskott-Aldrich syndrome protein via Vav and phosphatidylinositides. This represents a novel mechanism by which BCR-mediated signaling regulates BCR-mediated Ag processing and presentation.
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Affiliation(s)
- Shruti Sharma
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742
| | - Gregory Orlowski
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742
| | - Wenxia Song
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742
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23
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Ding Y, Chen B, Wang S, Zhao L, Chen J, Ding Y, Chen L, Luo R. Overexpression of Tiam1 in hepatocellular carcinomas predicts poor prognosis of HCC patients. Int J Cancer 2008; 124:653-8. [PMID: 18972435 DOI: 10.1002/ijc.23954] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Little research has been done to test the usefulness of T-lymphoma invasion and metastasis 1 (Tiam1) as a prognostic marker for hepatocellular carcinoma (HCC). In this study, we investigated Tiam1 expression and its prognostic value for HCC. HCC surgical tissue samples were taken from 152 HCC patients who had been followed up for 5 years. Overexpression of Tiam1 (Tiam1 2+ to 3+) was shown in 63.8% of the cases. The Tiam1 expression level did not correlate with any clinicopathological parameters. However, survival analysis showed that the Tiam1 overexpression group had a significantly shorter overall survival time than the Tiam1 downexpression group (p=0.008). Multivariate analysis showed that Tiam1 expression was a significant and independent prognostic parameter (p=0.042) for HCC patients. Tiam1 expression may be a novel and independent predictor for the prognosis of HCC patients.
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Affiliation(s)
- Yi Ding
- Department of Radiation Oncology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong Province, People's Republic of China
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24
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Li P, Martins IRS, Amarasinghe GK, Rosen MK. Internal dynamics control activation and activity of the autoinhibited Vav DH domain. Nat Struct Mol Biol 2008; 15:613-8. [PMID: 18488041 PMCID: PMC2512264 DOI: 10.1038/nsmb.1428] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2008] [Accepted: 04/04/2008] [Indexed: 11/09/2022]
Abstract
Protein motions are important to activity, but quantitative relationships between internal dynamics and function are not well understood. The Dbl homology (DH) domain of the proto-oncoprotein and guanine nucleotide exchange factor Vav1 is autoinhibited through interactions between its catalytic surface and a helix from an N-terminal acidic region. Phosphorylation of the helix relieves autoinhibition. Here we show by NMR spectroscopy that the autoinhibited DH domain exists in equilibrium between a ground state, where the active site is blocked by the inhibitory helix, and an excited state, where the helix is dissociated. Across a series of mutants that differentially sample these states, catalytic activity of the autoinhibited protein and its rate of phosphorylation are linearly dependent on the population of the excited state. Thus, internal dynamics are required for and control both basal activity and the rate of full activation of the autoinhibited DH domain.
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Affiliation(s)
| | | | | | - Michael K. Rosen
- Howard Hughes Medical Institute and Department of Biochemistry, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390-8816, USA
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25
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Rapley J, Tybulewicz VLJ, Rittinger K. Crucial structural role for the PH and C1 domains of the Vav1 exchange factor. EMBO Rep 2008; 9:655-61. [PMID: 18511940 PMCID: PMC2427238 DOI: 10.1038/embor.2008.80] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2008] [Revised: 04/10/2008] [Accepted: 04/10/2008] [Indexed: 12/26/2022] Open
Abstract
The Vav family of proteins are guanine nucleotide exchange factors (GEFs) for the Rho family of GTPases, which regulate various cellular functions, including T-cell activation. They contain a catalytic Dbl homology (DH) domain that is invariably followed by a pleckstrin homology (PH) domain, which is often required for catalytic activity. Vav proteins are the first GEFs for which an additional C1 domain is required for full biological activity. Here, we present the structure of a Vav1 fragment comprising the DH-PH-C1 domains bound to Rac1. This structure shows that the PH and C1 domains form a single structural unit that packs against the carboxy-terminal helix of the DH domain to stabilize its conformation and to promote nucleotide exchange. In contrast to previous reports, this structure shows that there are no direct contacts between the GTPase and C1 domain but instead suggests new mechanisms for the regulation of Vav1 activity.
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Affiliation(s)
- Jonathan Rapley
- Division of Molecular Structure, and National Institute for Medical Research, The Ridgeway, London NW7 1AA, UK
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26
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Chrencik JE, Brooun A, Zhang H, Mathews II, Hura GL, Foster SA, Perry JJP, Streiff M, Ramage P, Widmer H, Bokoch GM, Tainer JA, Weckbecker G, Kuhn P. Structural basis of guanine nucleotide exchange mediated by the T-cell essential Vav1. J Mol Biol 2008; 380:828-43. [PMID: 18589439 DOI: 10.1016/j.jmb.2008.05.024] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2008] [Revised: 05/08/2008] [Accepted: 05/11/2008] [Indexed: 12/27/2022]
Abstract
The guanine nucleotide exchange factor (GEF) Vav1 plays an important role in T-cell activation and tumorigenesis. In the GEF superfamily, Vav1 has the ability to interact with multiple families of Rho GTPases. The structure of the Vav1 DH-PH-CRD/Rac1 complex to 2.6 A resolution reveals a unique intramolecular network of contacts between the Vav1 cysteine-rich domain (CRD) and the C-terminal helix of the Vav1 Dbl homology (DH) domain. These unique interactions stabilize the Vav1 DH domain for its intimate association with the Switch II region of Rac1 that is critical for the displacement of the guanine nucleotide. Small angle x-ray scattering (SAXS) studies support this domain arrangement for the complex in solution. Further, mutational analyses confirms that the atypical CRD is critical for maintaining both optimal guanine nucleotide exchange activity and broader specificity of Vav family GEFs. Taken together, the data outline the detailed nature of Vav1's ability to contact a range of Rho GTPases using a novel protein-protein interaction network.
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Affiliation(s)
- Jill E Chrencik
- Department of Cellular Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
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27
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Signaling cascades as cellular devices for spatial computations. J Math Biol 2008; 58:35-55. [PMID: 18283462 DOI: 10.1007/s00285-008-0162-6] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2007] [Revised: 01/17/2008] [Indexed: 10/22/2022]
Abstract
Signaling networks usually include protein-modification cycles. Cascades of such cycles are the backbones of multiple signaling pathways. Protein gradients emerge from the spatial separation of opposing enzymes, such as kinases and phosphatases, or guanine nucleotide exchange factors (GEFs) and GTPase activating proteins (GAPs) for GTPase cycles. We show that different diffusivities of an active protein form and an inactive form leads to spatial gradients of protein abundance in the cytoplasm. For a cascade of cycles, using a discrete approximation of the space, we derive an analytical expression for the spatial gradients and show that it converges to an exact solution with decreasing the size of the quantization. Our results facilitate quantitative analysis of the dependence of spatial gradients on the network topology and reaction kinetics. We demonstrate how different cascade designs filter and process the input information to generate precise, complex spatial guidance for multiple GTPase effector processes. Thus, protein-modification cascades may serve as devices to compute complex spatial distributions of target proteins within intracellular space.
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28
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Bewry NN, Bolick SCE, Wright KL, Harton JA. GTP-dependent recruitment of CIITA to the class II major histocompatibility complex promoter. J Biol Chem 2007; 282:26178-84. [PMID: 17623662 DOI: 10.1074/jbc.m611747200] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We previously established that the class II transactivator CIITA binds GTP and disruption of the GTP binding ability of CIITA results in increased cytoplasmic CIITA, loss of nuclear CIITA, and thus diminished class II major histocompatibility complex transcription. Because of its role in facilitating nuclear localization, whether GTP binding is also required for CIITA-mediated transactivation of major histocompatibility class II genes remains unclear. We now show that recruitment of CIITA to the human leukocyte antigen (HLA)-DR promoter and activation of HLA-DR transcription is also GTP-dependent. After restoration of nuclear expression, CIITA mutants defective in GTP binding lack full transcriptional activation capacity. Although the availability of the activation domain of CIITA is unaltered, GTP mutants no longer cooperate with CREB-binding protein, p300, and pCAF and are defective in recruitment to the HLA-DR promoter.
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Affiliation(s)
- Nadine N Bewry
- Department of Molecular Medicine, H. Lee Moffitt Cancer Center, University of South Florida, Tampa, Florida 33612, USA
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29
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Schmitter T, Pils S, Sakk V, Frank R, Fischer KD, Hauck CR. The granulocyte receptor carcinoembryonic antigen-related cell adhesion molecule 3 (CEACAM3) directly associates with Vav to promote phagocytosis of human pathogens. THE JOURNAL OF IMMUNOLOGY 2007; 178:3797-805. [PMID: 17339478 DOI: 10.4049/jimmunol.178.6.3797] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The human granulocyte-specific receptor carcinoembryonic antigen-related cell adhesion molecule (CEACAM)3 is critically involved in the opsonin-independent recognition of several bacterial pathogens. CEACAM3-mediated phagocytosis depends on the integrity of an ITAM-like sequence within the cytoplasmic domain of CEACAM3 and is characterized by rapid stimulation of the GTPase Rac. By performing a functional screen with CEACAM3-expressing cells, we found that overexpression of a dominant-negative form of the guanine nucleotide exchange factor Vav, but not the dominant-negative versions SWAP70, Dock2, or ELMO1 interfered with CEACAM3-initiated phagocytosis. Moreover, small interfering RNA-mediated silencing of Vav reduced uptake and abrogated the stimulation of Rac in response to bacterial CEACAM3 engagement. In Vav1/Vav2-deficient cells, CEACAM3-mediated internalization was only observed after re-expression of Vav. Vav colocalized with CEACAM3 upon bacterial infection, coimmunoprecipitated in a complex with CEACAM3, and the Vav Src homology 2 domain directly associated with phosphorylated Tyr(230) of CEACAM3. In primary human granulocytes, TAT-mediated transduction of dominant-negative Vav, but not SWAP70, severely impaired the uptake of CEACAM3-binding bacteria. These data support the view that, different from canonical ITAM signaling, the CEACAM3 ITAM-like sequence short-wires bacterial recognition and Rac stimulation via a direct association with Vav to promote rapid phagocytosis and elimination of CEACAM-binding human pathogens.
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Affiliation(s)
- Tim Schmitter
- Zentrum für Infektionsforschung, Universität Würzburg, Würzburg, Germany
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30
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Weckbecker G, Bruns C, Fischer KD, Heusser C, Li J, Metzler B, Morris RE, Nuesslein-Hildesheim B, Raulf F, Wieczorek G, Zenke G. Strongly reduced alloreactivity and long-term survival times of cardiac allografts in Vav1- and Vav1/Vav2-knockout mice. Transpl Int 2007; 20:353-64. [PMID: 17326776 DOI: 10.1111/j.1432-2277.2006.00438.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Vav proteins mediate T- and B-cell activation by functioning as GTP/GDP exchange factors for small GTPases. We have studied the role of Vav1 and Vav2 in allogeneic T-cell activation, antibody responses and allograft rejection. Alloantigen-induced proliferation of T cells from Vav1- and Vav1/Vav2-knockout (ko) mice was decreased by >90% in a mixed lymphocyte reaction. In whole-blood cultures, Vav deficiency led to markedly impaired T- and B-cell activation. Expansion of Vav1- or Vav1/Vav2-ko T cells (C57BL/6) was reduced after transfer into severe combined immune deficiency/beige recipient mice (BALB/c). After priming with 2,4-dinitrophenyl (DNP)-keyhole limpet hemocyanin, T-cell-dependent anti-DNP IgM and IgG antibody levels were normal in Vav1-ko mice but undetectable in Vav1/Vav2-ko mice. The median survival time of BALB/c cardiac allografts transplanted into C57BL/6 Vav1-ko mice (n = 13) or Vav1/Vav2-ko mice (n = 5) was >100 and >77 days, compared with 8-9 days in the corresponding wild-type mice. Vav1/Vav2-ko mice with <100 days graft survival developed bacterial skin infections and were prematurely killed with beating cardiac allograft. Long-term surviving transplants of single and double ko mice showed mild cellular interstitial rejection and mild to severe vascular remodeling. In conclusion, our studies show for the first time that the absence of Vav1 and Vav1/Vav2 in ko mice strongly reduces alloreactivity and results in long-term allograft survival, whereas antibody responses were only affected in Vav1/Vav2 ko mice.
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Affiliation(s)
- Gisbert Weckbecker
- Autoimmunity and Transplantation, Novartis Institutes for BioMedical Research, Novartis Pharma AG, Basel, Switzerland.
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31
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Sahu SN, Nunez S, Bai G, Gupta A. Interaction of Pyk2 and PTP-PEST with leupaxin in prostate cancer cells. Am J Physiol Cell Physiol 2007; 292:C2288-96. [PMID: 17329398 DOI: 10.1152/ajpcell.00503.2006] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have identified the presence of leupaxin (LPXN), which belongs to the paxillin extended family of focal adhesion-associated adaptor proteins, in prostate cancer cells. Previous studies have demonstrated that LPXN is a component of the podosomal signaling complex found in osteoclasts, where LPXN was found to associate with the protein tyrosine kinases Pyk2 and c-Src and the cytosolic protein tyrosine phosphatase-proline-, glutamate-, serine-, and threonine-rich sequence (PTP-PEST). In the current study, LPXN was detectable as a 50-kDa protein in PC-3 cells, a bone-derived metastatic prostate cancer cell line. In PC-3 cells, LPXN was also found to associate with Pyk2, c-Src, and PTP-PEST. A siRNA-mediated inhibition of LPXN resulted in decreased in vitro PC-3 cell migration. A recombinant adenoviral-mediated overexpression of LPXN resulted in an increased association of Pyk2 with LPXN, whereas a similar adenoviral-mediated overexpression of PTP-PEST resulted in decreased association of Pyk2 and c-Src with LPXN. The overexpression of LPXN in PC-3 cells resulted in increased migration, as assessed by in vitro Transwell migration assays. On the contrary, the overexpression of PTP-PEST in PC-3 cells resulted in decreased migration. The overexpression of LPXN resulted in increased activity of Rho GTPase, which was decreased in PTP-PEST-overexpressing cells. The increase in Rho GTPase activity following overexpression of LPXN was inhibited in the presence of Y27632, a selective inhibitor of Rho GTPase. In conclusion, our data demonstrate that LPXN forms a signaling complex with Pyk2, c-Src, and PTP-PEST to regulate migration of prostate cancer cells.
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Affiliation(s)
- Surasri Nandan Sahu
- Dept. of Biomedical Sciences, Dental School, University of Maryland, Baltimore, MD 21201, USA
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Brooun A, Foster SA, Chrencik JE, Chien EYT, Kolatkar AR, Streiff M, Ramage P, Widmer H, Weckbecker G, Kuhn P. Remedial strategies in structural proteomics: expression, purification, and crystallization of the Vav1/Rac1 complex. Protein Expr Purif 2006; 53:51-62. [PMID: 17275330 PMCID: PMC1892187 DOI: 10.1016/j.pep.2006.10.027] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2006] [Revised: 10/24/2006] [Accepted: 10/25/2006] [Indexed: 11/19/2022]
Abstract
The signal transduction pathway involving the Vav1 guanine nucleotide exchange factor (GEF) and the Rac1 GTPase plays several key roles in the immune response mediated by the T cell receptor. Vav1 is also a unique member of the GEF family in that it contains a cysteine-rich domain (CRD) that is critical for Rac1 binding and maximal guanine nucleotide exchange activity, and thus may provide a unique protein-protein interface compared to other GEF/GTPase pairs. Here, we have applied a number of remedial structural proteomics strategies, such as construct and expression optimization, surface mutagenesis, limited proteolysis, and protein formulation to successfully express, purify, and crystallize the Vav1-DH-PH-CRD/Rac1 complex in an active conformation. We have also systematically characterized various Vav1 domains in a GEF assay and Rac1 in vitro binding experiments. In the context of Vav1-DH-PH-CRD, the zinc finger motif of the CRD is required for the expression of stable Vav1, as well as for activity in both a GEF assay and in vitro formation of a Vav1/Rac1 complex suitable for biophysical and structural characterization. Our data also indicate that the isolated CRD maintains a low level of specific binding to Rac1, appears to be folded based on 1D NMR analysis and coordinates two zinc ions based on ICP-MS analysis. The protein reagents generated here are essential tools for the determination of a three dimensional Vav1/Rac1 complex crystal structure and possibly for the identification of inhibitors of the Vav1/Rac1 protein-protein interaction with potential to inhibit lymphocyte activation.
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Affiliation(s)
- Alexei Brooun
- Department of Cellular Biology, The Scripps Research Institute, 10550 N. Torrey Pines Rd., MB-201, La Jolla, CA 92037, USA.
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Hamann MJ, Lubking CM, Luchini DN, Billadeau DD. Asef2 functions as a Cdc42 exchange factor and is stimulated by the release of an autoinhibitory module from a concealed C-terminal activation element. Mol Cell Biol 2006; 27:1380-93. [PMID: 17145773 PMCID: PMC1800726 DOI: 10.1128/mcb.01608-06] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Asef (herein called Asef1) was identified as a Rac1-specific exchange factor stimulated by adenomatous polyposis coli (APC), contributing to colorectal cancer cell metastasis. We investigated Asef2, an Asef1 homologue having a similar N-terminal APC binding region (ABR) and Src-homology 3 (SH3) domain. Contrary to previous reports, we found that Asef1 and Asef2 exchange activity is Cdc42 specific. Moreover, the ABR of Asef2 did not function independently but acted in tandem with the SH3 domain to bind APC. The ABRSH3 also bound the C-terminal tail of Asef2, allowing it to function as an autoinhibitory module within the protein. Deletion of the C-terminal tail did not constitutively activate Asef2 as predicted; rather, a conserved C-terminal segment was required for augmented Cdc42 GDP/GTP exchange. Thus, Asef2 activation involves APC releasing the ABRSH3 from the C-terminal tail, resulting in Cdc42 exchange. These results highlight a novel exchange factor regulatory mechanism and establish Asef1 and Asef2 as Cdc42 exchange factors, providing a more appropriate context for understanding the contribution of APC in establishing cell polarity and migration.
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Affiliation(s)
- Michael J Hamann
- Division of Oncology Research, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA
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Xu JW, Morita I, Ikeda K, Miki T, Yamori Y. C-reactive protein suppresses insulin signaling in endothelial cells: role of spleen tyrosine kinase. Mol Endocrinol 2006; 21:564-73. [PMID: 17095576 DOI: 10.1210/me.2006-0354] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Although few epidemiological studies have demonstrated that C-reactive protein (CRP) is related to insulin resistance, no study to date has examined the molecular mechanism. Here, we show that recombinant CRP attenuates insulin signaling through the regulation of spleen tyrosine kinase (Syk) on small G-protein RhoA, jun N-terminal kinase (JNK) MAPK, insulin receptor substrate-1 (IRS-1), and endothelial nitric oxide synthase in vascular endothelial cells. Recombinant CRP suppressed insulin-induced NO production, inhibited the phosphorylation of Akt and endothelial nitric oxide synthase, and stimulated the phosphorylation of IRS-1 at the Ser307 site in a dose-dependent manner. These events were blocked by treatment with an inhibitor of RhoA-dependent kinase Y27632, or an inhibitor of JNK SP600125, or the transfection of dominant negative RhoA cDNA. Next, anti-CD64 Fcgamma phagocytic receptor I (FcgammaRI), but not anti-CD16 (FcgammaRIIIa) or anti-CD32 (FcgammaRII) antibody, partially blocked the recombinant CRP-induced phosphorylation of JNK and IRS-1 and restored, to a certain extent, the insulin-stimulated phosphorylation of Akt. Furthermore, we identified that recombinant CRP modulates the phosphorylation of Syk tyrosine kinase in endothelial cells. Piceatannol, an inhibitor of Syk tyrosine kinase, or infection of Syk small interference RNA blocked the recombinant CRP-induced RhoA activity and the phosphorylation of JNK and IRS-1. In addition, piceatannol also restrained CRP-induced endothelin-1 production. We conclude that recombinant CRP induces endothelial insulin resistance and dysfunction, and propose a new mechanism by which recombinant CRP induces the phosphorylation of JNK and IRS-1 at the Ser307 site through a Syk tyrosine kinase and RhoA-activation signaling pathway.
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Affiliation(s)
- Jin-Wen Xu
- Frontier Health Science, School of Human Environmental Science, Mukogawa Women's University, Nishinomiya, Hyogo 663-8179, Japan.
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Augusto O, Muntz Vaz S. EPR spin-trapping of protein radicals to investigate biological oxidative mechanisms. Amino Acids 2006; 32:535-42. [PMID: 17048125 DOI: 10.1007/s00726-006-0429-4] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2006] [Accepted: 06/18/2006] [Indexed: 11/30/2022]
Abstract
Presently, free radicals and oxidants are considered to mediate from signaling circuits involved in physiology and pathology to cell and tissue injury. The elucidation of these many inter-related processes requires a better understanding of cellular oxidative mechanisms many of which are mediated by protein radicals. Here, we will discuss the potentialities of EPR spin-trapping of protein radicals to unravel oxidative mechanisms. An overview of the methodology and its application to identify protein residues that are the target of specific oxidants, characterize emerging oxidants, and discriminate radical from non radical mechanisms will be presented. The examples are based on work developed in our laboratories but will be discussed in a broad scenario to emphasize that simple experiments can provide relevant insights into the biological reactivity of known and emerging biological oxidants and into signaling mechanisms.
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Affiliation(s)
- O Augusto
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil.
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Shin EY, Lee CS, Cho TG, Kim YG, Song S, Juhnn YS, Park SC, Manser E, Kim EG. betaPak-interacting exchange factor-mediated Rac1 activation requires smgGDS guanine nucleotide exchange factor in basic fibroblast growth factor-induced neurite outgrowth. J Biol Chem 2006; 281:35954-64. [PMID: 16954223 DOI: 10.1074/jbc.m602399200] [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] [Indexed: 12/27/2022] Open
Abstract
Neuritogenesis requires active actin cytoskeleton rearrangement in which Rho GTPases play a pivotal role. In a previous study (Shin, E. Y., Woo, K. N., Lee, C. S., Koo, S. H., Kim, Y. G., Kim, W. J., Bae, C. D., Chang, S. I., and Kim, E. G. (2004) J. Biol. Chem. 279, 1994-2004), we demonstrated that betaPak-interacting exchange factor (betaPIX) guanine nucleotide exchange factor (GEF) mediates basic fibroblast growth factor (bFGF)-stimulated Rac1 activation through phosphorylation of Ser-525 and Thr-526 at the GIT-binding domain (GBD). However, the mechanism by which this phosphorylation event regulates the Rac1-GEF activity remained elusive. We show here that betaPIX binds to Rac1 via the GBD and also activates the GTPase via an associated GEF, smgGDS, in a phosphorylation-dependent manner. Notably, the Rac1-GEF activity of betaPIX persisted for an extended period of time following bFGF stimulation, unlike other Rho GEFs containing the Dbl homology domain. We demonstrate that C-PIX, containing proline-rich, GBD, and leucine zipper domains can interact with Rac1 via the GBD in vitro and in vivo and also mediated bFGF-stimulated Rac1 activation, as determined by a modified GEF assay and fluorescence resonance energy transfer analysis. However, nonphosphorylatable C-PIX (S525A/T526A) failed to generate Rac1-GTP. Finally, betaPIX is shown to form a trimeric complex with smgGDS and Rac1; down-regulation of smgGDS expression by short interfering RNA causing significant inhibition of betaPIX-mediated Rac1 activation and neurite outgrowth. These results provide evidence for a new and unexpected mechanism whereby betaPIX can regulate Rac1 activity.
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Affiliation(s)
- Eun-Young Shin
- Department of Biochemistry, College of Medicine, Chungbuk National University, Cheongju 361-763, Korea
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Wang Y, Wang S, Sheibani N. Enhanced proangiogenic signaling in thrombospondin-1-deficient retinal endothelial cells. Microvasc Res 2006; 71:143-51. [PMID: 16624339 DOI: 10.1016/j.mvr.2006.02.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2006] [Accepted: 02/16/2006] [Indexed: 12/19/2022]
Abstract
Thrombospondin-1 (TSP1) is an endogenous inhibitor of angiogenesis, which limits blood vessel density in normal tissues and curtails tumor growth. Previous studies of the molecular and cellular effects of TSP1 in angiogenesis have been contradictory. Here, we show that retinal endothelial cells (REC) prepared from TSP1-deficient (TSP1-/-) mice are more proliferative and migratory compared to the wild type REC. We observed up-regulation of the cell cycle regulators, including cyclin A, D1, and Cdk2, as well as the enhanced sequential activities of Src, PI3-kinase, Akt/PKB, Rac1/Cdc42 GTPases, and p38 MAP kinase in TSP1-/- REC. The increased levels of fibronectin and active Akt/PKB were also observed in retinal vasculature of TSP1-/- mice in vivo. Inhibition of Src/PI3-kinase/P38 MAP kinase activities in TSP1-/- REC resulted in decreased migration. Furthermore, TSP1-/- REC showed decreased intracellular levels of active Fyn and JNK2 without affecting caspase-3 activity. Thus, our results demonstrate that in the absence of TSP1, the proangiogenic signaling is enhanced, possibly through up-regulation of fibronectin expression. The enhanced signaling further promotes EC proliferation, migration, and survival. These novel observations support the TSP1's role as an endogenous inhibitor of angiogenesis whose endothelium expression promotes a quiescent, differentiated phenotype.
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Affiliation(s)
- Yongji Wang
- Department of Ophthalmology and Visual Sciences, University of Wisconsin, Madison, 53792, USA
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Heo J, Campbell SL. Mechanism of redox-mediated guanine nucleotide exchange on redox-active Rho GTPases. J Biol Chem 2005; 280:31003-10. [PMID: 15994296 DOI: 10.1074/jbc.m504768200] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Rho GTPases regulate multiple cellular processes including actin cytoskeletal rearrangements, transcriptional regulation, and oxidant production. The studies described herein demonstrate that small molecule redox agents, in addition to protein regulatory factors, can regulate the activity of redox-active Rho GTPases. A novel (GXXXXGK(S/T)C) motif, conserved in a number of Rho GTPases, appears critical for redox-mediated guanine nucleotide dissociation in vitro. A detailed molecular mechanism for redox regulation of GXXXXGK(S/T)C motif-containing Rho GTPases is proposed.
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Affiliation(s)
- Jongyun Heo
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North Carolina 27599-7260, USA
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