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Wu D, Casey PJ. GPCR-Gα13 Involvement in Mitochondrial Function, Oxidative Stress, and Prostate Cancer. Int J Mol Sci 2024; 25:7162. [PMID: 39000269 PMCID: PMC11241654 DOI: 10.3390/ijms25137162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2024] [Revised: 06/20/2024] [Accepted: 06/26/2024] [Indexed: 07/16/2024] Open
Abstract
Gα13 and Gα12, encoded by the GNA13 and GNA12 genes, respectively, are members of the G12 family of Gα proteins that, along with their associated Gβγ subunits, mediate signaling from specific G protein-coupled receptors (GPCRs). Advanced prostate cancers have increased expression of GPCRs such as CXC Motif Chemokine Receptor 4 (CXCR4), lysophosphatidic acid receptor (LPAR), and protease activated receptor 1 (PAR-1). These GPCRs signal through either the G12 family, or through Gα13 exclusively, often in addition to other G proteins. The effect of Gα13 can be distinct from that of Gα12, and the role of Gα13 in prostate cancer initiation and progression is largely unexplored. The oncogenic effect of Gα13 on cell migration and invasion in prostate cancer has been characterized, but little is known about other biological processes such as mitochondrial function and oxidative stress. Current knowledge on the link between Gα13 and oxidative stress is based on animal studies in which GPCR-Gα13 signaling decreased superoxide levels, and the overexpression of constitutively active Gα13 promoted antioxidant gene activation. In human samples, mitochondrial superoxide dismutase 2 (SOD2) correlates with prostate cancer risk and prognostic Gleason grade. However, overexpression of SOD2 in prostate cancer cells yielded conflicting results on cell growth and survival under basal versus oxidative stress conditions. Hence, it is necessary to explore the effect of Gα13 on prostate cancer tumorigenesis, as well as the effect of Gα13 on SOD2 in prostate cancer cell growth under oxidative stress conditions.
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Affiliation(s)
- Di Wu
- Programme in Cancer and Stem Cell Biology, Duke-NUS Medical School, 8 College Road, Singapore 169857, Singapore;
| | - Patrick J. Casey
- Programme in Cancer and Stem Cell Biology, Duke-NUS Medical School, 8 College Road, Singapore 169857, Singapore;
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, 308 Research Drive, Durham, NC 27710, USA
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Lee J, Avramets D, Jeon B, Choo H. Modulation of Serotonin Receptors in Neurodevelopmental Disorders: Focus on 5-HT7 Receptor. Molecules 2021; 26:molecules26113348. [PMID: 34199418 PMCID: PMC8199608 DOI: 10.3390/molecules26113348] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Revised: 05/31/2021] [Accepted: 05/31/2021] [Indexed: 12/17/2022] Open
Abstract
Since neurodevelopmental disorders (NDDs) influence more than 3% of children worldwide, there has been intense investigation to understand the etiology of disorders and develop treatments. Although there are drugs such as aripiprazole, risperidone, and lurasidone, these medications are not cures for the disorders and can only help people feel better or alleviate their symptoms. Thus, it is required to discover therapeutic targets in order to find the ultimate treatments of neurodevelopmental disorders. It is suggested that abnormal neuronal morphology in the neurodevelopment process is a main cause of NDDs, in which the serotonergic system is emerging as playing a crucial role. From this point of view, we noticed the correlation between serotonin receptor subtype 7 (5-HT7R) and NDDs including autism spectrum disorder (ASD), fragile X syndrome (FXS), and Rett syndrome (RTT). 5-HT7R modulators improved altered behaviors in animal models and also affected neuronal morphology via the 5-HT7R/G12 signaling pathway. Through the investigation of recent studies, it is suggested that 5-HT7R could be a potential therapeutic target for the treatment of NDDs.
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Affiliation(s)
- Jieon Lee
- Brain Science Institute, Korea Institute of Science and Technology, Seongbuk-gu, Seoul 02792, Korea; (J.L.); (D.A.)
- Division of Bio-Medical Science & Technology, KIST School, Korea University of Science and Technology, Seoul 02792, Korea
| | - Diana Avramets
- Brain Science Institute, Korea Institute of Science and Technology, Seongbuk-gu, Seoul 02792, Korea; (J.L.); (D.A.)
- Division of Bio-Medical Science & Technology, KIST School, Korea University of Science and Technology, Seoul 02792, Korea
| | - Byungsun Jeon
- Brain Science Institute, Korea Institute of Science and Technology, Seongbuk-gu, Seoul 02792, Korea; (J.L.); (D.A.)
- Correspondence: (B.J.); (H.C.); Tel.: +82-2-958-5191 (B.J.); +82-2-958-5157 (H.C.)
| | - Hyunah Choo
- Brain Science Institute, Korea Institute of Science and Technology, Seongbuk-gu, Seoul 02792, Korea; (J.L.); (D.A.)
- Division of Bio-Medical Science & Technology, KIST School, Korea University of Science and Technology, Seoul 02792, Korea
- Correspondence: (B.J.); (H.C.); Tel.: +82-2-958-5191 (B.J.); +82-2-958-5157 (H.C.)
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3
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Yang LK, Hou ZS, Tao YX. Biased signaling in naturally occurring mutations of G protein-coupled receptors associated with diverse human diseases. Biochim Biophys Acta Mol Basis Dis 2021; 1867:165973. [PMID: 32949766 PMCID: PMC7722056 DOI: 10.1016/j.bbadis.2020.165973] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 09/07/2020] [Accepted: 09/14/2020] [Indexed: 12/15/2022]
Abstract
G protein-coupled receptors (GPCRs) play critical roles in transmitting a variety of extracellular signals into the cells and regulate diverse physiological functions. Naturally occurring mutations that result in dysfunctions of GPCRs have been known as the causes of numerous diseases. Significant progresses have been made in elucidating the pathophysiology of diseases caused by mutations. The multiple intracellular signaling pathways, such as G protein-dependent and β-arrestin-dependent signaling, in conjunction with recent advances on biased agonism, have broadened the view on the molecular mechanism of disease pathogenesis. This review aims to briefly discuss biased agonism of GPCRs (biased ligands and biased receptors), summarize the naturally occurring GPCR mutations that cause biased signaling, and propose the potential pathophysiological relevance of biased mutant GPCRs associated with various endocrine diseases.
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Affiliation(s)
- Li-Kun Yang
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, United States
| | - Zhi-Shuai Hou
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, United States
| | - Ya-Xiong Tao
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, United States.
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4
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A synthetic method to assay adhesion-family G-protein coupled receptors. Determination of the G-protein coupling profile of ADGRG6(GPR126). Biochem Biophys Res Commun 2020; 534:317-322. [PMID: 33248691 DOI: 10.1016/j.bbrc.2020.11.086] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Accepted: 11/18/2020] [Indexed: 12/19/2022]
Abstract
G-protein coupled receptors (GPCRs) are the largest family of membrane-spanning receptors in metazoans and mediate diverse biological processes such as chemotaxis, vision, and neurotransmission. Adhesion GPCRs represent an understudied class of GPCRs. Adhesion GPCRs (ADGRs) are activated by an intrinsic proteolytic mechanism executed by the G-protein autoproteolysis inducing domain that defines this class of GPCRs. It is hypothesized that agonist ligands modulate the proteolyzed receptor to regulate the activity of a tethered agonist peptide that is an intramolecular activator of ADGRs. The mechanism of activation of ADGRs in physiological settings is unclear and the toolbox for interrogating ADGR physiology in cellular models is limited. Therefore, we generated a novel enterokinase-activated tethered ligand system for ADGRG6(GPR126). Enterokinase addition to cells expressing a synthetic ADGRG6 protein induced potent and efficacious signal transduction through heterotrimeric G-protein coupled second messenger pathways including cyclic nucleotide production, intracellular calcium mobilization, and GPCR-pathway linked reporter gene induction. These studies support the hypothesis that ADGRG6(GPR126) is coupled to multiple heterotrimeric G-proteins: including Gαs, Gαq, and Gα12. This novel assay method is robust, specific, and compatible with numerous cell pharmacology approaches. We present a new tool for determination of the biological function of ADGRs and the identification of ligands that engage these receptors.
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Bernau K, Torr EE, Evans MD, Aoki JK, Ngam CR, Sandbo N. Tensin 1 Is Essential for Myofibroblast Differentiation and Extracellular Matrix Formation. Am J Respir Cell Mol Biol 2017; 56:465-476. [PMID: 28005397 DOI: 10.1165/rcmb.2016-0104oc] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Myofibroblasts, the primary effector cells that mediate matrix remodeling during pulmonary fibrosis, rapidly assemble an extracellular fibronectin matrix. Tensin (TNS) 1 is a key component of specialized cellular adhesions (fibrillar adhesions) that bind to extracellular fibronectin fibrils. We hypothesized that TNS1 may play a role in modulating myofibroblast-mediated matrix formation. We found that TNS1 expression is increased in fibroblastic foci from lungs with idiopathic pulmonary fibrosis. Transforming growth factor (TGF)-β profoundly up-regulates TNS1 expression with kinetics that parallel the expression of the myofibroblast marker, smooth muscle α-actin. TGF-β-induced TNS1 expression is dependent on signaling through the TGF-β receptor 1 and is Rho coiled-coiled kinase/actin/megakaryoblastic leukemia-1/serum response factor dependent. Small interfering RNA-mediated knockdown of TNS1 disrupted TGF-β-induced myofibroblast differentiation, without affecting TGF-β/Smad signaling. In contrast, loss of TNS1 resulted in disruption of focal adhesion kinase phosphorylation, focal adhesion formation, and actin stress fiber development. Finally, TNS1 was essential for the formation of fibrillar adhesions and the assembly of nascent fibronectin and collagen matrix in myofibroblasts. In summary, our data show that TNS1 is a novel megakaryoblastic leukemia-1-dependent gene that is induced during pulmonary fibrosis. TNS1 plays an essential role in TGF-β-induced myofibroblast differentiation and myofibroblast-mediated formation of extracellular fibronectin and collagen matrix. Targeted disruption of TNS1 and associated signaling may provide an avenue to inhibit tissue fibrosis.
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Affiliation(s)
| | | | - Michael D Evans
- 2 Biostatistics and Medical Informatics, University of Wisconsin-Madison, School of Medicine and Public Health, Madison, Wisconsin
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Bodmann EL, Krett AL, Bünemann M. Potentiation of receptor responses induced by prolonged binding of Gα 13 and leukemia-associated RhoGEF. FASEB J 2017; 31:3663-3676. [PMID: 28465324 DOI: 10.1096/fj.201700026r] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Accepted: 04/17/2017] [Indexed: 12/29/2022]
Abstract
Diverse cellular functions are controlled by RhoA-GTPases, which are activated by trimeric G proteins via RhoGEFs, among others. In this study, we focused on the signaling from GPCRs to RhoA via Gα13 and leukemia-associated RhoGEF (LARG). The activation of Gα13 was elucidated in living cells with high temporal and spatial resolution by means of FRET. The inactivation after agonist withdrawal occurred in the same range (t1/2 = 25.3 ± 2.2 s; mean ± sem; n = 22) as described for other Gα proteins. The interaction of Gα13 and LARG and the thereby-induced LARG translocation to the plasma membrane were at least 1 order of magnitude more stable after agonist withdrawal, exceeding Gα13 deactivation in the absence of LARG several fold. Consequently, we observed an almost 100-fold higher agonist sensitivity of the Gα13 LARG interaction compared to the Gα13 activation in the absence of LARG.-Bodmann, E.-L., Krett, A.-L., Bünemann, M. Potentiation of receptor responses induced by prolonged binding of Gα13 and leukemia-associated RhoGEF.
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Affiliation(s)
- Eva-Lisa Bodmann
- Department of Pharmacology and Clinical Pharmacy, Philipps University of Marburg, Marburg, Germany
| | - Anna-Lena Krett
- Department of Pharmacology and Clinical Pharmacy, Philipps University of Marburg, Marburg, Germany
| | - Moritz Bünemann
- Department of Pharmacology and Clinical Pharmacy, Philipps University of Marburg, Marburg, Germany
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Sandbo N, Smolyaninova LV, Orlov SN, Dulin NO. Control of Myofibroblast Differentiation and Function by Cytoskeletal Signaling. BIOCHEMISTRY (MOSCOW) 2017; 81:1698-1708. [PMID: 28260491 DOI: 10.1134/s0006297916130071] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The cytoskeleton consists of three distinct types of protein polymer structures - microfilaments, intermediate filaments, and microtubules; each serves distinct roles in controlling cell shape, division, contraction, migration, and other processes. In addition to mechanical functions, the cytoskeleton accepts signals from outside the cell and triggers additional signals to extracellular matrix, thus playing a key role in signal transduction from extracellular stimuli through dynamic recruitment of diverse intermediates of the intracellular signaling machinery. This review summarizes current knowledge about the role of cytoskeleton in the signaling mechanism of fibroblast-to-myofibroblast differentiation - a process characterized by accumulation of contractile proteins and secretion of extracellular matrix proteins, and being critical for normal wound healing in response to tissue injury as well as for aberrant tissue remodeling in fibrotic disorders. Specifically, we discuss control of serum response factor and Hippo signaling pathways by actin and microtubule dynamics as well as regulation of collagen synthesis by intermediate filaments.
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Affiliation(s)
- N Sandbo
- University of Wisconsin, Department of Medicine, Madison, WI, USA
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8
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The analysis of heterotaxy patients reveals new loss-of-function variants of GRK5. Sci Rep 2016; 6:33231. [PMID: 27618959 PMCID: PMC5020398 DOI: 10.1038/srep33231] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Accepted: 08/19/2016] [Indexed: 11/08/2022] Open
Abstract
G protein-coupled receptor kinase 5 (GRK5) is a regulator of cardiac performance and a potential therapeutic target in heart failure in the adult. Additionally, we have previously classified GRK5 as a determinant of left-right asymmetry and proper heart development using zebrafish. We thus aimed to identify GRK5 variants of functional significance by analysing 187 individuals with laterality defects (heterotaxy) that were associated with a congenital heart defect (CHD). Using Sanger sequencing we identified two moderately frequent variants in GRK5 with minor allele frequencies <10%, and seven very rare polymorphisms with minor allele frequencies <1%, two of which are novel variants. Given their evolutionarily conserved position in zebrafish, in-depth functional characterisation of four variants (p.Q41L, p.G298S, p.R304C and p.T425M) was performed. We tested the effects of these variants on normal subcellular localisation and the ability to desensitise receptor signalling as well as their ability to correct the left-right asymmetry defect upon Grk5l knockdown in zebrafish. While p.Q41L, p.R304C and p.T425M responded normally in the first two aspects, neither p.Q41L nor p.R304C were capable of rescuing the lateralisation phenotype. The fourth variant, p.G298S was identified as a complete loss-of-function variant in all assays and provides insight into the functions of GRK5.
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9
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Anastasiadou S, Knöll B. The multiple sclerosis drug fingolimod (FTY720) stimulates neuronal gene expression, axonal growth and regeneration. Exp Neurol 2016; 279:243-260. [PMID: 26980486 DOI: 10.1016/j.expneurol.2016.03.012] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2015] [Revised: 03/03/2016] [Accepted: 03/11/2016] [Indexed: 11/30/2022]
Abstract
Fingolimod (FTY720) is a new generation oral treatment for multiple sclerosis (MS). So far, FTY720 was mainly considered to target trafficking of immune cells but not brain cells such as neurons. Herein, we analyzed FTY720's potential to directly alter neuronal function. In CNS neurons, we identified a FTY720 governed gene expression response. FTY720 upregulated immediate early genes (IEGs) encoding for neuronal activity associated transcription factors such as c-Fos, FosB, Egr1 and Egr2 and induced actin cytoskeleton associated genes (actin isoforms, tropomyosin, calponin). Stimulation of primary neurons with FTY720 enhanced neurite growth and altered growth cone morphology. In accordance, FTY720 enhanced axon regeneration in mice upon facial nerve axotomy. We identified components of a FTY720 engaged signaling cascade including S1P receptors, G12/13G-proteins, RhoA-GTPases and the transcription factors SRF/MRTF. In summary, we uncovered a broader cellular and therapeutic operation mode of FTY720, suggesting beneficial FTY720 effects also on CNS neurons during MS therapy and for treatment of other neurodegenerative diseases requiring neuroprotective and neurorestorative processes.
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Affiliation(s)
- Sofia Anastasiadou
- Institute of Physiological Chemistry, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Bernd Knöll
- Institute of Physiological Chemistry, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany.
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10
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Vatter P, Schuhholz J, Koenig C, Pfreimer M, Moepps B. Ligand-dependent serum response factor activation by the human CC chemokine receptors CCR2a and CCR2b is mediated by G proteins of the Gqfamily. J Leukoc Biol 2016; 99:979-91. [DOI: 10.1189/jlb.2ma0815-386r] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2015] [Accepted: 01/13/2016] [Indexed: 12/31/2022] Open
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11
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Rourke JL, Dranse HJ, Sinal CJ. CMKLR1 and GPR1 mediate chemerin signaling through the RhoA/ROCK pathway. Mol Cell Endocrinol 2015; 417:36-51. [PMID: 26363224 DOI: 10.1016/j.mce.2015.09.002] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Revised: 07/31/2015] [Accepted: 09/01/2015] [Indexed: 12/14/2022]
Abstract
Chemerin is an adipose-derived hormone that regulates immunity and energy homesotasis. To date, all known chemerin functions have been attributed to activation of the G protein-coupled receptor chemokine-like receptor-1 (CMKLR1). Chemerin is also the only known ligand for a second receptor, G protein-coupled receptor-1 (GPR1), whose signaling and function remains unknown. This study investigated the in vitro signal transduction mechanisms of CMKLR1 and GPR1 using a panel of luciferase-reporters and pathway-specific inhibitors. Herein we report the novel finding that chemerin signals through a RhoA and rho-associated protein kinase (ROCK)-dependent pathway for activation of the transcriptional regulator serum-response factor (SRF). Despite similarities in RhoA/ROCK, Gαi/o, and MAPK signaling, we also demonstrate species-specific and receptor-dependent variations in GPR1 and CMKLR1 signaling and expression of the SRF target genes EGR1, FOS and VCL. Moreover, we demonstrate that signaling through p38, Gαi/o, RhoA, and ROCK is required for chemerin-mediated chemotaxis of L1.2 lymphocytes and AGS gastric adenocarcinoma cells. These results provide, to our knowledge, the first empirical evidence that GPR1 is a functional chemerin receptor and identify RhoA/SRF as a novel chemerin-signaling axis via both CMKLR1 and GPR1.
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Affiliation(s)
- Jillian L Rourke
- Department of Pharmacology, Dalhousie University, Halifax, NS, Canada
| | - Helen J Dranse
- Department of Pharmacology, Dalhousie University, Halifax, NS, Canada
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Sobel K, Monnier L, Menyhart K, Bolinger M, Studer R, Nayler O, Gatfield J. FTY720 Phosphate Activates Sphingosine-1-Phosphate Receptor 2 and Selectively Couples to Gα12/13/Rho/ROCK to Induce Myofibroblast Contraction. Mol Pharmacol 2015; 87:916-27. [PMID: 25762025 DOI: 10.1124/mol.114.097261] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Accepted: 03/11/2015] [Indexed: 12/26/2022] Open
Abstract
FTY720 phosphate (FTY720-P; 2-amino-2-[2-(4-octylphenyl)ethyl]-1,3-propanediol, monodihydrogen phosphate ester) is a nonselective sphingosine-1-phosphate (S1P) receptor agonist thought to be devoid of activity at the S1P2 receptor subtype. However, we have recently shown that FTY720-P displays significant S1P2 receptor agonist activity in recombinant cells and fibroblasts expressing endogenous S1P2 receptors. To elucidate the S1P2-dependent signaling pathways that were activated by FTY720-P, we employed second messenger assays and impedance-based assays in combination with pharmacological and small interfering RNA-based pathway inhibition in recombinant Chinese hamster ovary (CHO)-S1P2 cells as well as human lung myofibroblasts generated in vitro. In CHO-S1P2 cells, FTY720-P did not modulate cAMP or calcium levels. However, reporter-gene assays, impedance-based assays with a selective Rho-associated kinase (ROCK) inhibitor, Gα12/13 knockdown and activated Rho-pull-down assays demonstrated that FTY720-P potently activated Gα12/13/Rho/ROCK signaling. S1P similarly activated Gα12/13/Rho/ROCK signaling via S1P2 receptors, whereas the two selective S1P1 receptor agonists (Z,Z)-5-(3-chloro-4-[(2R)-2,3-dihydroxy-propoxy]-benzylidene)-2-propylimino-3-o-tolyl-thiazolidin-4-one (ponesimond) and 5-[4-phenyl-5-(trifluoromethyl)thiophen-2-yl]-3-[3-(trifluoromethyl)phenyl]1,2,4-oxadiazole (SEW2871) were inactive. In lung myofibroblasts, which mainly expressed the S1P2 receptor subtype, we showed that FTY720-P selectively activated the Gα12/13/Rho/ROCK pathway via the S1P2 receptor. Moreover, the activation of the Gα12/13/Rho/ROCK pathway in myofibroblasts by FTY720-P caused potent myofibroblast contraction similar to that induced by the natural ligand S1P. Thus, complementing second messenger assays with unbiased label-free assays or phenotypic assays in native expression systems can uncover activation of additional pathways, such as Gα12/13/Rho/ROCK signaling.
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Affiliation(s)
- Katrin Sobel
- Actelion Pharmaceuticals Ltd, Gewerbestrasse 16, Allschwil, Switzerland
| | - Lucile Monnier
- Actelion Pharmaceuticals Ltd, Gewerbestrasse 16, Allschwil, Switzerland
| | - Katalin Menyhart
- Actelion Pharmaceuticals Ltd, Gewerbestrasse 16, Allschwil, Switzerland
| | - Matthias Bolinger
- Actelion Pharmaceuticals Ltd, Gewerbestrasse 16, Allschwil, Switzerland
| | - Rolf Studer
- Actelion Pharmaceuticals Ltd, Gewerbestrasse 16, Allschwil, Switzerland
| | - Oliver Nayler
- Actelion Pharmaceuticals Ltd, Gewerbestrasse 16, Allschwil, Switzerland
| | - John Gatfield
- Actelion Pharmaceuticals Ltd, Gewerbestrasse 16, Allschwil, Switzerland
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Woodard GE, Jardín I, Berna-Erro A, Salido GM, Rosado JA. Regulators of G-protein-signaling proteins: negative modulators of G-protein-coupled receptor signaling. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2015; 317:97-183. [PMID: 26008785 DOI: 10.1016/bs.ircmb.2015.02.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Regulators of G-protein-signaling (RGS) proteins are a category of intracellular proteins that have an inhibitory effect on the intracellular signaling produced by G-protein-coupled receptors (GPCRs). RGS along with RGS-like proteins switch on through direct contact G-alpha subunits providing a variety of intracellular functions through intracellular signaling. RGS proteins have a common RGS domain that binds to G alpha. RGS proteins accelerate GTPase and thus enhance guanosine triphosphate hydrolysis through the alpha subunit of heterotrimeric G proteins. As a result, they inactivate the G protein and quickly turn off GPCR signaling thus terminating the resulting downstream signals. Activity and subcellular localization of RGS proteins can be changed through covalent molecular changes to the enzyme, differential gene splicing, and processing of the protein. Other roles of RGS proteins have shown them to not be solely committed to being inhibitors but behave more as modulators and integrators of signaling. RGS proteins modulate the duration and kinetics of slow calcium oscillations and rapid phototransduction and ion signaling events. In other cases, RGS proteins integrate G proteins with signaling pathways linked to such diverse cellular responses as cell growth and differentiation, cell motility, and intracellular trafficking. Human and animal studies have revealed that RGS proteins play a vital role in physiology and can be ideal targets for diseases such as those related to addiction where receptor signaling seems continuously switched on.
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Affiliation(s)
- Geoffrey E Woodard
- Department of Surgery, Uniformed Services University of the Health Sciences, Bethesda, MD, USA; Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, Bethesda, MD, USA
| | - Isaac Jardín
- Department of Physiology, University of Extremadura, Caceres, Spain
| | - A Berna-Erro
- Department of Physiology, University of Extremadura, Caceres, Spain
| | - Gines M Salido
- Department of Physiology, University of Extremadura, Caceres, Spain
| | - Juan A Rosado
- Department of Physiology, University of Extremadura, Caceres, Spain
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Donlea JM, Ramanan N, Silverman N, Shaw PJ. Genetic rescue of functional senescence in synaptic and behavioral plasticity. Sleep 2014; 37:1427-37. [PMID: 25142573 DOI: 10.5665/sleep.3988] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
STUDY OBJECTIVES Aging has been linked with decreased neural plasticity and memory formation in humans and in laboratory model species such as the fruit fly, Drosophila melanogaster. Here, we examine plastic responses following social experience in Drosophila as a high-throughput method to identify interventions that prevent these impairments. PATIENTS OR PARTICIPANTS Wild-type and transgenic Drosophila melanogaster. DESIGN AND INTERVENTIONS Young (5-day old) or aged (20-day old) adult female Drosophila were housed in socially enriched (n = 35-40) or isolated environments, then assayed for changes in sleep and for structural markers of synaptic terminal growth in the ventral lateral neurons (LNVs) of the circadian clock. MEASUREMENTS AND RESULTS When young flies are housed in a socially enriched environment, they exhibit synaptic elaboration within a component of the circadian circuitry, the LNVs, which is followed by increased sleep. Aged flies, however, no longer exhibit either of these plastic changes. Because of the tight correlation between neural plasticity and ensuing increases in sleep, we use sleep after enrichment as a high-throughput marker for neural plasticity to identify interventions that prolong youthful plasticity in aged flies. To validate this strategy, we find three independent genetic manipulations that delay age-related losses in plasticity: (1) elevation of dopaminergic signaling, (2) over-expression of the transcription factor blistered (bs) in the LNVs, and (3) reduction of the Imd immune signaling pathway. These findings provide proof-of-principle evidence that measuring changes in sleep in flies after social enrichment may provide a highly scalable assay for the study of age-related deficits in synaptic plasticity. CONCLUSIONS These studies demonstrate that Drosophila provides a promising model for the study of age-related loss of neural plasticity and begin to identify genes that might be manipulated to delay the onset of functional senescence.
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Benbernou N, Esnault S, Galibert F. Activation of SRE and AP1 by olfactory receptors via the MAPK and Rho dependent pathways. Cell Signal 2013; 25:1486-97. [PMID: 23524338 DOI: 10.1016/j.cellsig.2013.02.019] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2012] [Revised: 02/08/2013] [Accepted: 02/12/2013] [Indexed: 12/11/2022]
Abstract
Whereas the activation of MAPKs (mitogen activated kinases) and Rho dependant pathways by GPCR (G protein coupled receptors) has been the subject of many studies, its implication in the signalling of olfactory receptors, which constitute the largest GPCR family, has been far less analysed. Using an in vitro heterologous system, we showed that odorant activated ORs activate SRE containing promoters via the ERK pathway. We also demonstrated that RhoA and Rock kinases but not Rac were involved in ORs-induced SRE/SRF activation and that AP1 was activated, via JNK and p38 MAPKinase. Using real time PCR we found that mOR23, RnI7 and CfOR12A07 induced elevated levels of transcription factors ELK-4, srf, c-fos and c-jun mRNAs whereas mOREG induced an elevated transcription levels of c-fos and c-jun mRNA only. We showed also that odorant activated ORs stimulate the downstream MAPKs and Rho pathways in primary cultures of rat olfactory sensory neurons (OSNs). Similar results were also obtained with OE (olfactory epithelium) extracts prepared from rats exposed to odorants in vivo. Finally, we showed the important role of the AKT and MAPK signalling pathways in OSNs survival. Taken together, these data provide direct evidence that the binding of odorants onto their ORs activates the MAPK and Rho signalling pathways that are involved in OSNs survival events. This suggests that these pathways could be implicated in the regulation of OSNs homeostasis.
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16
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Siehler S. G12/13-dependent signaling of G-protein-coupled receptors: disease context and impact on drug discovery. Expert Opin Drug Discov 2013; 2:1591-604. [PMID: 23488903 DOI: 10.1517/17460441.2.12.1591] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
G-protein-coupled receptors (GPCRs) transmit extracellular signals across the plasma membrane via intracellular activation of heterotrimeric G proteins. The signal transduction pathways of Gs, Gi and Gq protein families are widely studied, whereas signaling properties of G12 proteins are only emerging. Many GPCRs were found to couple to G12/13 proteins in addition to coupling to one or more other types of G proteins. G12/13 proteins couple GPCRs to activation of the small monomeric GTPase RhoA. Activation of RhoA modulates various downstream effector systems relevant to diseases such as hypertension, artherosclerosis, asthma and cancer. GPCR screening assays exist for Gs-, Gi- and Gq-linked pathways, whereas a drug-screening assay for the G12-Rho pathway was developed only recently. The review gives an overview of the present understanding of the G12/13-related biology of GPCRs.
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Affiliation(s)
- Sandra Siehler
- Novartis Institutes for BioMedical Research Basel, Center for Proteomic Chemistry, Novartis Pharma AG, WSJ-88.2.05, 4002 Basel, Switzerland +41 61 324 8946 ; +41 61 324 2870 ;
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17
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The zinc-binding region of IL-2 inducible T cell kinase (Itk) is required for interaction with Gα13 and activation of serum response factor. Int J Biochem Cell Biol 2013; 45:1074-82. [PMID: 23454662 DOI: 10.1016/j.biocel.2013.02.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2012] [Revised: 02/04/2013] [Accepted: 02/18/2013] [Indexed: 11/20/2022]
Abstract
Tec family kinases play critical roles in the activation of immune cells. In particular, Itk is important for the activation of T cells via the T cell Receptor (TcR), however, molecules that cooperate with Itk to activate downstream targets remain little explored. Here we show that Itk interacts with the heterotrimeric G-protein α subunit Gα13 during TcR triggering. This interaction requires membrane localization of both partners, and is partially dependent on GDP- and GTP-bound states of Gα13. Furthermore, we find that Itk interacts with Gα13 via the zinc binding regions within its Tec homology domain. The interaction between Itk and Gα13 also results in tyrosine phosphorylation of Gα13, however this is not required for the interaction. Itk enhances Gα13 mediated activation of serum response factor (SRF) transcriptional activity dependent on its ability to interact with Gα13, but its kinase activity is not required to enhance SRF activity. These data reveal a new pathway regulated by Itk in cells, and suggest cross talk between Itk and G-protein signaling downstream of the TcR.
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18
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Lanzafame AA, Christopoulos A, Mitchelson F. Cellular Signaling Mechanisms for Muscarinic Acetylcholine Receptors. ACTA ACUST UNITED AC 2011. [DOI: 10.3109/10606820308263] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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19
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Abstract
Dopamine is an important regulator of systemic blood pressure via multiple mechanisms. It affects fluid and electrolyte balance by its actions on renal hemodynamics and epithelial ion and water transport and by regulation of hormones and humoral agents. The kidney synthesizes dopamine from circulating or filtered L-DOPA independently from innervation. The major determinants of the renal tubular synthesis/release of dopamine are probably sodium intake and intracellular sodium. Dopamine exerts its actions via two families of cell surface receptors, D1-like receptors comprising D1R and D5R, and D2-like receptors comprising D2R, D3R, and D4R, and by interactions with other G protein-coupled receptors. D1-like receptors are linked to vasodilation, while the effect of D2-like receptors on the vasculature is variable and probably dependent upon the state of nerve activity. Dopamine secreted into the tubular lumen acts mainly via D1-like receptors in an autocrine/paracrine manner to regulate ion transport in the proximal and distal nephron. These effects are mediated mainly by tubular mechanisms and augmented by hemodynamic mechanisms. The natriuretic effect of D1-like receptors is caused by inhibition of ion transport in the apical and basolateral membranes. D2-like receptors participate in the inhibition of ion transport during conditions of euvolemia and moderate volume expansion. Dopamine also controls ion transport and blood pressure by regulating the production of reactive oxygen species and the inflammatory response. Essential hypertension is associated with abnormalities in dopamine production, receptor number, and/or posttranslational modification.
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Affiliation(s)
- Ines Armando
- Children’s National Medical Center—Center for Molecular Physiology Research, Washington, District of Columbia
| | - Van Anthony M. Villar
- Children’s National Medical Center—Center for Molecular Physiology Research, Washington, District of Columbia
| | - Pedro A. Jose
- Children’s National Medical Center—Center for Molecular Physiology Research, Washington, District of Columbia
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20
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Ognibene M, Vanni C, Segalerba D, Mancini P, Merello E, Torrisi MR, Bosco MC, Varesio L, Eva A. The tumor suppressor hamartin enhances Dbl protein transforming activity through interaction with ezrin. J Biol Chem 2011; 286:29973-83. [PMID: 21712385 DOI: 10.1074/jbc.m111.270785] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The Rho guanine nucleotide exchange factor (GEF) Dbl binds to the N-terminal region of ezrin, a member of the ERM (ezrin, radixin, moesin) proteins known to function as linkers between the plasma membrane and the actin cytoskeleton. Here we have characterized the interaction between ezrin and Dbl. We show that binding of Dbl with ezrin involves positively charged amino acids within the region of the pleckstrin homology (PH) domain comprised between β1 and β2 sheets. In addition, we show that Dbl forms a complex with the tuberous sclerosis-1 (TSC-1) gene product hamartin and with ezrin. We demonstrate that hamartin and ezrin are both required for activation of Dbl. In fact, the knock-down of ezrin and hamartin, as well as the expression of a mutant hamartin, unable to bind ezrin, inhibit Dbl transforming and exchange activity. These results suggest that Dbl is regulated by hamartin through association with ezrin.
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Affiliation(s)
- Marzia Ognibene
- Laboratorio di Biologia Molecolare, Istituto G. Gaslini, Genova, Italy
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21
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Hajicek N, Kukimoto-Niino M, Mishima-Tsumagari C, Chow CR, Shirouzu M, Terada T, Patel M, Yokoyama S, Kozasa T. Identification of critical residues in G(alpha)13 for stimulation of p115RhoGEF activity and the structure of the G(alpha)13-p115RhoGEF regulator of G protein signaling homology (RH) domain complex. J Biol Chem 2011; 286:20625-36. [PMID: 21507947 PMCID: PMC3121507 DOI: 10.1074/jbc.m110.201392] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2010] [Revised: 04/08/2011] [Indexed: 01/28/2023] Open
Abstract
RH-RhoGEFs are a family of guanine nucleotide exchange factors that contain a regulator of G protein signaling homology (RH) domain. The heterotrimeric G protein Gα(13) stimulates the guanine nucleotide exchange factor (GEF) activity of RH-RhoGEFs, leading to activation of RhoA. The mechanism by which Gα(13) stimulates the GEF activity of RH-RhoGEFs, such as p115RhoGEF, has not yet been fully elucidated. Here, specific residues in Gα(13) that mediate activation of p115RhoGEF are identified. Mutation of these residues significantly impairs binding of Gα(13) to p115RhoGEF as well as stimulation of GEF activity. These data suggest that the exchange activity of p115RhoGEF is stimulated allosterically by Gα(13) and not through its interaction with a secondary binding site. A crystal structure of Gα(13) bound to the RH domain of p115RhoGEF is also presented, which differs from a previously crystallized complex with a Gα(13)-Gα(i1) chimera. Taken together, these data provide new insight into the mechanism by which p115RhoGEF is activated by Gα(13).
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Affiliation(s)
- Nicole Hajicek
- Department of Pharmacology, College of Medicine, University of Illinois, Chicago, Illinois 60612, USA
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22
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Wuertz CM, Lorincz A, Vettel C, Thomas MA, Wieland T, Lutz S. p63RhoGEF—a key mediator of angiotensin II‐dependent signaling and processes in vascular smooth muscle cells. FASEB J 2010. [DOI: 10.1096/fj.10.155499] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Christina M. Wuertz
- Institute of Experimental and Clinical Pharmacology and Toxicology Heidelberg Germany
| | - Akos Lorincz
- Institute of Experimental and Clinical Pharmacology and Toxicology Heidelberg Germany
| | - Christiane Vettel
- Institute of Experimental and Clinical Pharmacology and Toxicology Heidelberg Germany
| | - Martin A. Thomas
- Institute of Experimental and Clinical Pharmacology and Toxicology Heidelberg Germany
| | - Thomas Wieland
- Institute of Experimental and Clinical Pharmacology and Toxicology Heidelberg Germany
| | - Susanne Lutz
- Medical Faculty MannheimUniversity of Heidelberg Heidelberg Germany
- Department of PharmacologyMedical Faculty Goettingen, University of Goettingen Goettingen Germany
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Abstract
During the development of the pulmonary vasculature in the fetus, many structural and functional changes occur to prepare the lung for the transition to air breathing. The development of the pulmonary circulation is genetically controlled by an array of mitogenic factors in a temporo-spatial order. With advancing gestation, pulmonary vessels acquire increased vasoreactivity. The fetal pulmonary vasculature is exposed to a low oxygen tension environment that promotes high intrinsic myogenic tone and high vasocontractility. At birth, a dramatic reduction in pulmonary arterial pressure and resistance occurs with an increase in oxygen tension and blood flow. The striking hemodynamic differences in the pulmonary circulation of the fetus and newborn are regulated by various factors and vasoactive agents. Among them, nitric oxide, endothelin-1, and prostaglandin I2 are mainly derived from endothelial cells and exert their effects via cGMP, cAMP, and Rho kinase signaling pathways. Alterations in these signaling pathways may lead to vascular remodeling, high vasocontractility, and persistent pulmonary hypertension of the newborn.
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Affiliation(s)
- Yuansheng Gao
- Department of Physiology and Pathophysiology, Peking University, Health Science Center, Beijing, China; and Department of Pediatrics, University of Illinois, College of Medicine at Chicago, Chicago, Illinois
| | - J. Usha Raj
- Department of Physiology and Pathophysiology, Peking University, Health Science Center, Beijing, China; and Department of Pediatrics, University of Illinois, College of Medicine at Chicago, Chicago, Illinois
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24
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Wuertz CM, Lorincz A, Vettel C, Thomas MA, Wieland T, Lutz S. p63RhoGEF--a key mediator of angiotensin II-dependent signaling and processes in vascular smooth muscle cells. FASEB J 2010; 24:4865-76. [PMID: 20739613 DOI: 10.1096/fj.10-155499] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The purpose of our study was to investigate the role of endogenous p63RhoGEF in G(q/11)-dependent RhoA activation and signaling in rat aortic smooth muscle cells (RASMCs). Therefore, we studied the expression and subcellular localization in freshly isolated RASMCs and performed loss of function experiments to analyze its contribution to RhoGTPase activation and functional responses such as proliferation and contraction. By this, we could show that p63RhoGEF is endogenously expressed in RASMCs and acts there as the dominant mediator of the fast angiotensin II (ANG II)-dependent but not of the sphingosine-1-phosphate (S(1)P)-dependent RhoA activation. p63RhoGEF is not an activator of the concomitant Rac1 activation and functions independently of caveolae. The knockdown of endogenous p63RhoGEF significantly reduced the mitogenic response of ANG II, abolished ANG II-induced stress fiber formation and cell elongation in 2-D culture, and impaired the ANG II-driven contraction in a collagen-based 3-D model. In conclusion, our data provide for the first time evidence that p63RhoGEF is an important mediator of ANG II-dependent RhoA activation in RASMCs and therewith a leading actor in the subsequently triggered cellular processes, such as proliferation and contraction.
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Affiliation(s)
- Christina M Wuertz
- Institute of Experimental and Clinical Pharmacology and Toxicology, Medical Faculty Mannheim, University of Heidelberg, Heidelberg, Germany
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25
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The role of beta(1)Pix/caveolin-1 interaction in endothelin signaling through Galpha subunits. Biochem Biophys Res Commun 2009; 391:1330-5. [PMID: 20026011 DOI: 10.1016/j.bbrc.2009.12.041] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2009] [Accepted: 12/10/2009] [Indexed: 01/19/2023]
Abstract
Endothelin-1 (ET-1) is a potent mitogen that transmits signals through its cognate G protein-coupled receptors to stimulate extracellular signal-regulated kinase Erk1/2. Endothelin-1 receptors (ET-Rs) are known to interact with caveolin-1 and co-localize in caveolae which integrate different receptor and signaling proteins. We have recently shown that beta(1)Pix binds specifically to ET-Rs. Here, we show that beta(1)Pix binding to caveolin-1 is dependent on heterotrimeric G proteins activation state. beta(1)Pix interaction with different G proteins is increased in the presence of the G protein activator AMF. Moreover, extraction of cholesterol with methyl-beta-cyclodextrin disrupts the binding of beta(1)Pix to Galpha(q), Galpha(12) and phospho-Erk1/2 but not the binding of beta(1)Pix to G(beta1). The disruption of beta(1)Pix dimerization strongly reduced the binding of caveolin-1, Galpha(q) and Galpha(12). Constitutively active mutants of Galpha(q) and Galpha(12) increased Cdc42 activation when co-expressed with beta(1)Pix but not in the presence of beta(1)Pix dimerization deficient mutant beta(1)PixDelta (602-611). ET-1 stimulation increased the binding of phosphorylated Erk1/2 to beta(1)Pix but not to beta(1)PixDelta (602-611). RGS3 decreased ET-1-induced Cdc42 activation. These results strongly suggest that the activation of ET-Rs leads to the compartmentalization and the binding of Galpha(q) to beta(1)Pix in caveolae, where dimeric beta(1)Pix acts as platform to facilitate the binding and the activation of Erk1/2.
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26
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Tesmer JJG. Structure and function of regulator of G protein signaling homology domains. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2009; 86:75-113. [PMID: 20374714 DOI: 10.1016/s1877-1173(09)86004-3] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
All regulator of G protein signaling (RGS) proteins contain a conserved domain of approximately 130 amino acids that binds to activated heterotrimeric G protein α subunits (Gα) and accelerates their rate of GTP hydrolysis. Homologous domains are found in at least six other protein families, including a family of Rho guanine nucleotide exchange factors (RhoGEFs) and the G protein-coupled receptor kinases (GRKs). Although some of the RhoGEF and GRK RGS-like domains can also bind to activated Gα subunits, they do so in distinct ways and with much lower levels of GTPase activation. In other protein families, the domains have as of yet no obvious relationship to heterotrimeric G protein signaling. These RGS homology (RH) domains are now recognized as mediators of extraordinarily diverse protein-protein interactions. Through these interactions, they play roles that range from enzyme to molecular scaffold to signal transducing module. In this review, the atomic structures of RH domains from RGS proteins, Axins, RhoGEFs, and GRKs are compared in light of what is currently known about their functional roles.
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Affiliation(s)
- John J G Tesmer
- Department of Pharmacology, Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109‐2216, USA
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27
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Wang Z, Kumamoto Y, Wang P, Gan X, Lehmann D, Smrcka AV, Cohn L, Iwasaki A, Li L, Wu D. Regulation of immature dendritic cell migration by RhoA guanine nucleotide exchange factor Arhgef5. J Biol Chem 2009; 284:28599-606. [PMID: 19713215 DOI: 10.1074/jbc.m109.047282] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
There are a large number of Rho guanine nucleotide exchange factors, most of which have no known functions. Here, we carried out a short hairpin RNA-based functional screen of Rho-GEFs for their roles in leukocyte chemotaxis and identified Arhgef5 as an important factor in chemotaxis of a macrophage phage-like RAW264.7 cell line. Arhgef5 can strongly activate RhoA and RhoB and weakly RhoC and RhoG, but not Rac1, RhoQ, RhoD, or RhoV, in transfected human embryonic kidney 293 cells. In addition, Gbetagamma interacts with Arhgef5 and can stimulate Arhgef5-mediated activation of RhoA in an in vitro assay. In vivo roles of Arhgef5 were investigated using an Arhgef-5-null mouse line. Arhgef5 deficiency did not affect chemotaxis of mouse macrophages, T and B lymphocytes, and bone marrow-derived mature dendritic cells (DC), but it abrogated MIP1alpha-induced chemotaxis of immature DCs and impaired migration of DCs from the skin to lymph node. In addition, Arhgef5 deficiency attenuated allergic airway inflammation. Therefore, this study provides new insights into signaling mechanisms for DC migration regulation.
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Affiliation(s)
- Zhenglong Wang
- Program for Vascular Biology and Therapeutics and Department of Pharmacology, Yale University School of Medicine, New Haven, Connecticut 06520,, USA
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28
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Han J, Liu G, Profirovic J, Niu J, Voyno-Yasenetskaya T. Zyxin is involved in thrombin signaling via interaction with PAR-1 receptor. FASEB J 2009; 23:4193-206. [PMID: 19690217 DOI: 10.1096/fj.09-131862] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Protease-activated receptor 1 (PAR-1) mediates thrombin signaling in human endothelial cells. As a G-protein-coupled receptor, PAR-1 transmits thrombin signal through activation of the heterotrimeric G proteins, Gi, Gq, and G12/13. In this study, we demonstrated that zyxin, a LIM-domain-containing protein, is involved in thrombin-mediated actin cytoskeleton remodeling and serum response element (SRE)-dependent gene transcription. We determined that zyxin binds to the C-terminal domain of PAR-1, providing a possible mechanism of involvement of zyxin as a signal transducer in PAR-1 signaling. Data showing that disruption of PAR-1-zyxin interaction inhibited thrombin-induced stress fiber formation and SRE activation supports this hypothesis. Similarly, depletion of zyxin using siRNA inhibited thrombin-induced actin stress fiber formation and SRE-dependent gene transcription. In addition, depletion of zyxin resulted in delay of endothelial barrier restoration after thrombin treatment. Notably, down-regulation of zyxin did not affect thrombin-induced activation of RhoA or Gi, Gq, and G12/13 heterotrimeric G proteins, implicating a novel signaling pathway regulated by PAR-1 that is not mediated by G-proteins. The observation that zyxin targets VASP, a partner of zyxin in regulation of actin assembly and dynamics, to focal adhesions and along stress fibers on thrombin stimulation suggests that zyxin may participate in thrombin-induced cytoskeletal remodeling through recruitment of VASP. In summary, this study establishes a crucial role of zyxin in thrombin signaling in endothelial cells and provides evidence for a novel PAR-1 signaling pathway mediated by zyxin.
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Affiliation(s)
- Jingyan Han
- Department of Pharmacology (MC 868), University of Illinois at Chicago, 909 S. Wolcott Ave., Chicago, IL 60612, USA
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29
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Yeung WWS, Wong YH. The RhoA-specific guanine nucleotide exchange factor p63RhoGEF binds to activated Galpha(16) and inhibits the canonical phospholipase Cbeta pathway. Cell Signal 2009; 21:1317-25. [PMID: 19332116 DOI: 10.1016/j.cellsig.2009.03.017] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2009] [Accepted: 03/09/2009] [Indexed: 11/28/2022]
Abstract
Heterotrimeric G proteins regulate diverse physiological processes by modulating the activities of intracellular effectors. Members of the Galpha(q) family link G protein-coupled receptor activation to phospholipase Cbeta (PLCbeta) activity and intracellular calcium signaling cascades. However, they differ markedly in biochemical properties as well as tissue distribution. Recent findings have shown that some of the cellular activities of Galpha(q) family members are independent of PLCbeta activation. A guanine nucleotide exchange factor, p63RhoGEF, has been shown to interact with Galpha(q) proteins and thus provides linkage to RhoA activation. However, it is not known if p63RhoGEF can associate with other Galpha(q) family members such as Galpha(16). In the present study, we employed co-immunoprecipitation studies in HEK293 cells to demonstrate that p63RhoGEF can form a stable complex with the constitutively active mutant of Galpha(16) (Galpha(16)QL). Interestingly, overexpression of p63RhoGEF inhibited Galpha(16)QL-induced IP(3) production in a concentration-dependent manner. The binding of PLCbeta(2) to Galpha(16)QL could be displaced by p63RhoGEF. Similarly, p63RhoGEF inhibited the binding of tetratricopeptide repeat 1 to Galpha(16)QL, leading to a suppression of Galpha(16)QL-induced Ras activation. In the presence of p63RhoGEF, Galpha(16)QL-induced STAT3 phosphorylation was significantly reduced and Galpha(16)QL-mediated SRE transcriptional activation was attenuated. Taken together, these results suggest that p63RhoGEF binds to activated Galpha(16) and inhibits its signaling pathways.
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Affiliation(s)
- Wendy W S Yeung
- Department of Biochemistry, the Molecular Neuroscience Center, and the Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
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Abstract
G protein-coupled receptors (GPCRs) represent a large family of seven transmembrane receptors, which communicate extracellular signals into the cellular lumen. The human genome contains 720-800 GPCRs, and their diverse signal characteristics are determined by their specific tissue and subcellular expression profiles, as well as their coupling profile to the various G protein families (G(s), G(i), G(q), G(12)). The G protein coupling pattern links GPCR activation to the specific downstream effector pathways. G(12/13) signalling of GPCRs has been studied only recently in more detail, and involves activation of RhoGTPase nucleotide exchange factors (RhoGEFs). Four mammalian RhoGEFs regulated by G(12/13) proteins are known: p115-RhoGEF, PSD-95/Disc-large/ZO-1 homology-RhoGEF, leukemia-associated RhoGEF and lymphoid blast crisis-RhoGEF. These link GPCRs to activation of the small monomeric GTPase RhoA, and other downstream effectors. Misregulated G(12/13) signalling is involved in multiple pathophysiological conditions such as cancer, cardiovascular diseases, arterial and pulmonary hypertension, and bronchial asthma. Specific targeting of G(12/13) signalling-related diseases of GPCRs hence provides novel therapeutic approaches. Assays to quantitatively measure GPCR-mediated activation of G(12/13) are only emerging, and are required to understand the G(12/13)-linked pharmacology. The review gives an overview of G(12/13) signalling of GPCRs with a focus on RhoGEF proteins as the immediate mediators of G(12/13) activation.
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Affiliation(s)
- Sandra Siehler
- Novartis Institutes for BioMedical Research Basel, Center for Proteomic Chemistry, Novartis Pharma AG, Basel, Switzerland.
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Sandbo N, Kregel S, Taurin S, Bhorade S, Dulin NO. Critical role of serum response factor in pulmonary myofibroblast differentiation induced by TGF-beta. Am J Respir Cell Mol Biol 2009; 41:332-8. [PMID: 19151320 DOI: 10.1165/rcmb.2008-0288oc] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Transforming growth factor-beta (TGF-beta) is a cytokine implicated in wound healing and in the pathogenesis of pulmonary fibrosis. TGF-beta stimulates myofibroblast differentiation characterized by expression of contractile smooth muscle (SM)-specific proteins such as SM-alpha-actin. In the present study, we examined the role of serum response factor (SRF) in the mechanism of TGF-beta-induced pulmonary myofibroblast differentiation of human lung fibroblasts (HLF). TGF-beta stimulated SM-alpha-actin expression in HLF, which paralleled with a profound induction of SRF expression and activity. Inhibition of SRF by the pharmacologic SRF inhibitor (CCG-1423), or via adenovirus-mediated transduction of SRF short hairpin RNA (shSRF), blocked the expression of both SRF and SM-alpha-actin in response to TGF-beta without affecting Smad-mediated signaling of TGF-beta. However, forced expression of SRF on its own did not promote SM-alpha-actin expression, whereas expression of the constitutively transactivated SRF fusion protein (SRF-VP16) was sufficient to induce SM-alpha-actin expression, suggesting that both expression and transactivation of SRF are important. Activation of protein kinase A (PKA) by forskolin or iloprost resulted in a significant inhibition of SM-alpha-actin expression induced by TGF-beta, and this was associated with inhibition of both SRF expression and activity, but not of Smad-mediated gene transcription. In summary, this is the first direct demonstration that TGF-beta-induced pulmonary myofibroblast differentiation is mediated by SRF, and that inhibition of myofibroblast differentiation by PKA occurs through down-regulation of SRF expression levels and SRF activity, independent of Smad signaling.
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Affiliation(s)
- Nathan Sandbo
- Section of Pulmonary and Critical Care Medicine, University of Chicago, 5841 S. Maryland Ave., MC 6076, Chicago, IL 60618, USA.
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Abstract
G protein-coupled receptors (GPCRs) transmit extracellular signals into the intracellular space, and play key roles in the physiological regulation of virtually every cell and tissue. Characteristic for the GPCR superfamily of cell surface receptors are their seven transmembrane-spanning alpha-helices, an extracellular N terminus and intracellular C-terminal tail. Besides transmission of extracellular signals, their activity is modulated by cellular signals in an auto- or transregulatory fashion. The molecular complexity of GPCRs and their regulated signaling networks triggered the interest in academic research groups to explore them further, and their drugability and role in pathophysiology triggers pharmaceutical research towards small molecular weight ligands and therapeutic antibodies. About 30% of marketed drugs target GPCRs, which underlines the importance of this target class. This review describes current and emerging cellular assays for the ligand discovery of GPCRs.
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Affiliation(s)
- Sandra Siehler
- Novartis Institutes for BioMedical Research Basel, Center for Proteomic Chemistry, Novartis Pharma AG, 4002 Basel, Switzerland.
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Constitutive serum response factor activation by the viral chemokine receptor homologue pUS28 is differentially regulated by Galpha(q/11) and Galpha(16). Cell Signal 2008; 20:1528-37. [PMID: 18534820 DOI: 10.1016/j.cellsig.2008.04.010] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2008] [Accepted: 04/11/2008] [Indexed: 01/30/2023]
Abstract
Expression of the human cytomegalovirus (HCMV)-encoded chemokine receptor homologue pUS28 in mammalian cells results in ligand-dependent and -independent changes in the activity of multiple cellular signal transduction pathways. The ligand-dependent signalling activity of pUS28 has been shown to be predominantly mediated by heterotrimeric G proteins of the G(i/o) and G(12/13) subfamilies. Ligand-independent constitutive activity of pUS28 causing stimulation of inositol phosphate formation has been correlated with the coupling of pUS28 to G proteins of the G(q) family. It is well known that activation of G(q) proteins by cell surface receptors is coupled to activation of the Rho GTPase RhoA. Activated RhoA regulates numerous cellular functions, including the activity of the transcription factor serum response factor (SRF). The marked activation of G(q) proteins by pUS28 in transfected and HCMV-infected cells prompted us to investigate its effect on SRF activity. The results presented herein demonstrate that expression of pUS28 in COS-7 cells caused a vigorous induction of SRF activity. This effect was observed in the absence of chemokines known to interact with pUS28, and was specifically mediated by endogenous G(q) and/or G(11) as well as RhoA and/or a closely related Rho GTPase. The stimulatory effect of pUS28 and Galpha(q/11) was independent of phospholipase C-beta (PLCbeta) activation and was markedly sensitive to inhibition by wild-type, but not by constitutively active Galpha(16), thus identifying Galpha(16) as a modulator of Galpha(q/11) function likely to act by competing with Galpha(q/11) for and thus uncoupling Galpha(q/11) from activation by pUS28.
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Bhattacharyya R, Noch EK, Khalili K. A novel role of Rac1 GTPase in JCV T-antigen-mediated beta-catenin stabilization. Oncogene 2007; 26:7628-36. [PMID: 17637758 DOI: 10.1038/sj.onc.1210576] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Wnt signaling follows canonical and non-canonical pathways to regulate a variety of processes during cellular homeostasis and development. The large T-antigen (T-Ag) of the human neurotropic JC virus, has been shown to modulate the Wnt-signaling pathway via interaction with beta-catenin, one of the most important components of the canonical Wnt pathway. Here, we have identified an alternative non-canonical pathway that allows T-Ag to recruit Rac1 for stabilizing beta-catenin by inhibiting its ubiquitin-dependent proteasomal degradation. We demonstrate that inhibition of Rac1 by its dominant negative mutant, RacN17, abrogates T-Ag-mediated stabilization of beta-catenin yet exhibits no impact on the transcriptional activity of beta-catenin. Results from immunocytochemistry revealed that together with T-Ag, a pool of beta-catenin appears at the cell surface, particularly at the membrane ruffles where active Rac1 is positioned. Interestingly, cooperativity between T-Ag and beta-catenin leads to activation of Rac1, which in turn, stimulates its association with beta-catenin. These observations unravel the interplay between beta-catenin and Rac1 that is initiated by T-Ag and results in stabilization of beta-catenin and its presence in cell membrane ruffles.
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Affiliation(s)
- R Bhattacharyya
- Department of Neuroscience, Center for Neurovirology, Temple University School of Medicine, Philadelphia, PA 19122, USA
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35
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Mericskay M, Blanc J, Tritsch E, Moriez R, Aubert P, Neunlist M, Feil R, Li Z. Inducible mouse model of chronic intestinal pseudo-obstruction by smooth muscle-specific inactivation of the SRF gene. Gastroenterology 2007; 133:1960-70. [PMID: 18054567 DOI: 10.1053/j.gastro.2007.09.010] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/20/2007] [Accepted: 08/30/2007] [Indexed: 01/20/2023]
Abstract
BACKGROUND & AIMS Serum response factor (SRF) regulates the expression of muscle genes and immediate early genes. We investigated the consequences of inactivating this transcription factor SRF in adult gastrointestinal smooth muscle cells. METHODS SRF-floxed mice were crossed with SM-CreER(T2)(ki) mice expressing a tamoxifen-inducible recombinase in smooth muscle cells. Tamoxifen was injected into 12-week-old animals to activate the CreER(T2) and excise the SRF gene. RESULTS SRF was down-regulated in the smooth muscle cells of the gastrointestinal tract, urinary bladder, and aorta. The mutant mice developed severe dilation of the intestinal tract associated with food stasis and air-fluid levels in the lumen 13 days after tamoxifen treatment. Mutant mice displayed cachexia and died between days 13 and 22. The dilation was associated with a thinning of the muscularis propria and was also observed in the urinary bladder. Ex vivo colonic contraction induced by electric field stimulation and carbachol was impaired in the mutant mice before the occurrence of the dilation phenotype. The expression of several genes, including those encoding smooth muscle actin, the heavy chain of smooth muscle myosin, and smoothelin, was 60% to 70% lower in mutants than in controls, and mutants also had a lower F/G actin ratio. CONCLUSIONS SRF plays a central role in maintaining visceral smooth muscle contractile function in adults. Mice with a smooth muscle cell-specific SRF mutation develop a severe motility disorder resembling chronic intestinal pseudo-obstruction in humans and may be used as an inducible model of this disorder.
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Affiliation(s)
- Mathias Mericskay
- Pierre & Marie Curie University Paris 6, Paris, France; CNRS, UMR7079 Physiology and Physiopathology, Paris, France.
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36
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Williams SL, Lutz S, Charlie NK, Vettel C, Ailion M, Coco C, Tesmer JJG, Jorgensen EM, Wieland T, Miller KG. Trio's Rho-specific GEF domain is the missing Galpha q effector in C. elegans. Genes Dev 2007; 21:2731-46. [PMID: 17942708 DOI: 10.1101/gad.1592007] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The Galpha(q) pathway is essential for animal life and is a central pathway for driving locomotion, egg laying, and growth in Caenorhabditis elegans, where it exerts its effects through EGL-8 (phospholipase Cbeta [PLCbeta]) and at least one other effector. To find the missing effector, we performed forward genetic screens to suppress the slow growth and hyperactive behaviors of mutants with an overactive Galpha(q) pathway. Four suppressor mutations disrupted the Rho-specific guanine-nucleotide exchange factor (GEF) domain of UNC-73 (Trio). The mutations produce defects in neuronal function, but not neuronal development, that cause sluggish locomotion similar to animals lacking EGL-8 (PLCbeta). Strains containing null mutations in both EGL-8 (PLCbeta) and UNC-73 (Trio RhoGEF) have strong synthetic phenotypes that phenocopy the arrested growth and near-complete paralysis of Galpha(q)-null mutants. Using cell-based and biochemical assays, we show that activated C. elegans Galpha(q) synergizes with Trio RhoGEF to activate RhoA. Activated Galpha(q) and Trio RhoGEF appear to be part of a signaling complex, because they coimmunoprecipitate when expressed together in cells. Our results show that Trio's Rho-specific GEF domain is a major Galpha(q) effector that, together with PLCbeta, mediates the Galpha(q) signaling that drives the locomotion, egg laying, and growth of the animal.
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Affiliation(s)
- Stacey L Williams
- Program in Molecular, Cell, and Developmental Biology, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104, USA
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Cho MK, Kim WD, Ki SH, Hwang JI, Choi S, Lee CH, Kim SG. Role of Galpha12 and Galpha13 as novel switches for the activity of Nrf2, a key antioxidative transcription factor. Mol Cell Biol 2007; 27:6195-208. [PMID: 17591699 PMCID: PMC1952151 DOI: 10.1128/mcb.02065-06] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Galpha12 and Galpha13 function as molecular regulators responding to extracellular stimuli. NF-E2-related factor 2 (Nrf2) is involved in a protective adaptive response to oxidative stress. This study investigated the regulation of Nrf2 by Galpha12 and Galpha13. A deficiency of Galpha12, but not of Galpha13, enhanced Nrf2 activity and target gene transactivation in embryo fibroblasts. In mice, Galpha12 knockout activated Nrf2 and thereby facilitated heme catabolism to bilirubin and its glucuronosyl conjugations. An oligonucleotide microarray demonstrated the transactivation of Nrf2 target genes by Galpha12 gene knockout. Galpha12 deficiency reduced Jun N-terminal protein kinase (JNK)-dependent Nrf2 ubiquitination required for proteasomal degradation, and so did Galpha13 deficiency. The absence of Galpha12, but not of Galpha13, increased protein kinase C delta (PKC delta) activation and the PKC delta-mediated serine phosphorylation of Nrf2. Galpha13 gene knockout or knockdown abrogated the Nrf2 phosphorylation induced by Galpha12 deficiency, suggesting that relief from Galpha12 repression leads to the Galpha13-mediated activation of Nrf2. Constitutive activation of Galpha13 promoted Nrf2 activity and target gene induction via Rho-mediated PKC delta activation, corroborating positive regulation by Galpha13. In summary, Galpha12 and Galpha13 transmit a JNK-dependent signal for Nrf2 ubiquitination, whereas Galpha13 regulates Rho-PKC delta-mediated Nrf2 phosphorylation, which is negatively balanced by Galpha12.
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Affiliation(s)
- Min Kyung Cho
- College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, Sillim-dong, Gwanak-gu, Seoul, South Korea
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Vogt A, Lutz S, Rümenapp U, Han L, Jakobs KH, Schmidt M, Wieland T. Regulator of G-protein signalling 3 redirects prototypical Gi-coupled receptors from Rac1 to RhoA activation. Cell Signal 2007; 19:1229-37. [PMID: 17300916 DOI: 10.1016/j.cellsig.2007.01.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2006] [Revised: 01/08/2007] [Accepted: 01/08/2007] [Indexed: 11/19/2022]
Abstract
The small GTPases, Rac1 and RhoA, are pivotal regulators of several essential, but distinct cellular processes. Numerous G-protein-coupled receptors signal to these GTPases, but with different specificities. Specifically, Gi-coupled receptors (GiPCRs) are generally believed to activate Rac1, but not RhoA, a process involving Gbetagamma-dimers and phosphatidylinositol 3-kinase (PI3K). Here we show that, depending on the expression level of the 519 amino acid isoform of regulator of G-protein signalling 3 (RGS3L), prototypical GiPCRs, like M2 muscarinic, A1 adenosine, and alpha2-adrenergic receptors, activate either Rac1 or RhoA in human embryonic kidney cells and neonatal rat cardiomyocyte-derived H10 cells. The switch from Rac1 to RhoA activation in H10 cells was controlled by fibroblast growth factor-2 (FGF-2), lowering the expression of RGS3L. Activation of both, Rac1 and RhoA, seen at low and high expression levels of RGS3L, respectively, was sensitive to pertussis toxin and the PI3K inhibitor LY294002 and mediated by Gbetagamma-dimers. We conclude that RGS3L functions as a molecular switch, redirecting GiPCRs via Gbetagamma-dimers and PI3K from Rac1 to RhoA activation. Considering the essential roles of Rac1 and RhoA in many signalling pathways, this additional function of RGS3L indicates a specific role of this protein in cellular signalling networks.
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Affiliation(s)
- Andreas Vogt
- Department of Experimental and Clinical Pharmacology and Toxicology, University of Heidelberg, Mannheim, Germany
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39
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Ho G, Wang Y, Jones PG, Young KH. Activation of serum response element by D2 dopamine receptor is governed by Gbetagamma-mediated MAPK and Rho pathways and regulated by RGS proteins. Pharmacology 2006; 79:114-21. [PMID: 17179741 DOI: 10.1159/000098097] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2006] [Accepted: 10/30/2006] [Indexed: 11/19/2022]
Abstract
In this study, we investigated the activation of the serum response element (SRE) by the D2 dopamine receptor (D2R) agonist quinpirole. Stimulation of CHO cells expressing the D2R by quinpirol evoked a dose-dependent SRE activation, which was completely blocked by overnight treatment of pertussis toxin or by co-expression of the beta-adrenergic receptor kinase C-terminus, implicating the involvement of Galpha(i )and Gbetagamma in the signal transduction. Furthermore, using MEK inhibitors and dominant negative mutants of RhoA, Rac1, and Cdc42, we showed that the Gbetagamma-mediated activation of the SRE in CHO cells utilizes both MAPK and Rho pathways. Expression of either regulator of G protein signaling 2 or 4 (RGS2 or RGS4) proteins significantly attenuated the quinpirole-induced SRE activation. These results delineate the signaling pathways which couple D2 receptor to the transcriptional activation of SRE and demonstrate a modulatory role for RGS proteins in these processes.
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Affiliation(s)
- Guyu Ho
- Wyeth Neuroscience Research, Wyeth Research, Princeton, N.J., USA
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40
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Kedmi M, Orr-Urtreger A. Differential brain transcriptome of beta4 nAChR subunit-deficient mice: is it the effect of the null mutation or the background strain? Physiol Genomics 2006; 28:213-22. [PMID: 16985005 DOI: 10.1152/physiolgenomics.00155.2006] [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: 11/22/2022] Open
Abstract
Studies using mice with beta4 nicotinic acetylcholine receptor (nAChR) subunit deficiency (beta4-/- mice) helped reveal the roles of this subunit in bradycardiac response to vagal stimulation, nicotine-induced seizure activity and anxiety. To identify genes that might be related to beta4-containing nAChRs activity, we compared the mRNA expression profiles of brains from beta4-/- and wild-type mice using Affymetrix U74Av2 microarray. Seventy-seven genes significantly differentiated between these two experimental groups. Of them, the two most downregulated were spastic paraplegia 21 (human) homolog (Spg21) and 6-pyruvoyl-tetrahydropterin synthase (Pts) genes. Since the targeted mutagenesis of the beta4 nAChR subunit was done by using two mouse strains, 129SvEv and C57BL/6J, it is possible that the genes closely linked to the mutated beta4 gene represent the 129SvEv allele and not the control C57BL/6J-driven allele. We examined this possibility by using public database and quantitative RT-PCR. The expression levels of Spg21 and Pts genes that, like the beta4 gene, are localized on mouse chromosome 9, as well as the expression levels of other genes located on this chromosome, were dependent on the mouse background strain. The 67 differentially expressed genes that are not located on chromosome 9 were further analyzed for overrepresented functional annotations and transcription regulatory elements compared with the entire microarray. Genes encoding for proteins involved in tyrosine phosphatase activity, calcium ion binding, cell growth and/or maintenance, and chromosome organization were overrepresented. Our data enhance the understanding of the molecular interactions involved in the beta4 nAChR subunit function. They also emphasize the need for careful interpretation of expression microarray studies done on genetically manipulated animals.
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Affiliation(s)
- Merav Kedmi
- Genetic Institute, Tel Aviv Sourasky Medical Center, and Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
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41
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Shin KJ, Wall EA, Zavzavadjian JR, Santat LA, Liu J, Hwang JI, Rebres R, Roach T, Seaman W, Simon MI, Fraser IDC. A single lentiviral vector platform for microRNA-based conditional RNA interference and coordinated transgene expression. Proc Natl Acad Sci U S A 2006; 103:13759-64. [PMID: 16945906 PMCID: PMC1557799 DOI: 10.1073/pnas.0606179103] [Citation(s) in RCA: 254] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
RNAi is proving to be a powerful experimental tool for the functional annotation of mammalian genomes. The full potential of this technology will be realized through development of approaches permitting regulated manipulation of endogenous gene expression with coordinated reexpression of exogenous transgenes. We describe the development of a lentiviral vector platform, pSLIK (single lentivector for inducible knockdown), which permits tetracycline-regulated expression of microRNA-like short hairpin RNAs from a single viral infection of any naïve cell system. In mouse embryonic fibroblasts, the pSLIK platform was used to conditionally deplete the expression of the heterotrimeric G proteins Galpha12 and Galpha13 both singly and in combination, demonstrating the Galpha13 dependence of serum response element-mediated transcription. In RAW264.7 macrophages, regulated knockdown of Gbeta2 correlated with a reduced Ca(2+) response to C5a. Insertion of a GFP transgene upstream of the Gbeta2 microRNA-like short hairpin RNA allowed concomitant reexpression of a heterologous mRNA during tetracycline-dependent target gene knockdown, significantly enhancing the experimental applicability of the pSLIK system.
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Affiliation(s)
- Kum-Joo Shin
- *Division of Biology, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125; and
| | - Estelle A. Wall
- Alliance for Cell Signaling Molecular Biology Laboratory and
- *Division of Biology, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125; and
| | - Joelle R. Zavzavadjian
- Alliance for Cell Signaling Molecular Biology Laboratory and
- *Division of Biology, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125; and
| | - Leah A. Santat
- *Division of Biology, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125; and
| | - Jamie Liu
- *Division of Biology, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125; and
| | - Jong-Ik Hwang
- *Division of Biology, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125; and
| | - Robert Rebres
- Alliance for Cell Signaling Macrophage Biology Laboratory, Department of Veterans Affairs Medical Center, University of California, 4150 Clement Street, San Francisco, CA 94121
| | - Tamara Roach
- Alliance for Cell Signaling Macrophage Biology Laboratory, Department of Veterans Affairs Medical Center, University of California, 4150 Clement Street, San Francisco, CA 94121
| | - William Seaman
- Alliance for Cell Signaling Macrophage Biology Laboratory, Department of Veterans Affairs Medical Center, University of California, 4150 Clement Street, San Francisco, CA 94121
| | - Melvin I. Simon
- Alliance for Cell Signaling Molecular Biology Laboratory and
- *Division of Biology, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125; and
| | - Iain D. C. Fraser
- Alliance for Cell Signaling Molecular Biology Laboratory and
- *Division of Biology, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125; and
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42
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Graness A, Poli V, Goppelt-Struebe M. STAT3-independent inhibition of lysophosphatidic acid-mediated upregulation of connective tissue growth factor (CTGF) by cucurbitacin I. Biochem Pharmacol 2006; 72:32-41. [PMID: 16707113 DOI: 10.1016/j.bcp.2006.04.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2006] [Revised: 03/28/2006] [Accepted: 04/07/2006] [Indexed: 11/21/2022]
Abstract
Cucurbitacins are recognised as anti-tumour agents because of their interference with STAT3 signalling, but may also affect the integrity of the actin cytoskeleton. In the present study the effect of cucurbitacin I was investigated in fibroblasts. In these cells, cucurbitacin I interfered with lysophosphatidic acid (LPA) signalling. It inhibited tyrosine phosphorylation of focal adhesion proteins and induction of connective tissue growth factor (CTGF), a potent profibrotic protein. Inhibition of Src family kinases with PP2, but not the inactive analogue PP3, also interfered with LPA-mediated tyrosine phosphorylation and induction of CTGF. Jak2-STAT3 signalling seemed to be the connecting link, because CTGF induction was sensitive to AG490, an inhibitor of Jak2, and cucurbitacin I, an inhibitor of Jak2 and STAT3. However, LPA did not activate tyrosine phosphorylation of STAT3. Furthermore, cucurbitacin I was as effective in STAT3 knock out cells as in control cells. Therefore, the inhibitory effect of cucurbitacin I was not related to inhibition of STAT3. Immunocytochemical analysis of cucurbitacin I-treated cells revealed disassembly of F-actin fibres, reorganisation into F-actin patches and resolution of focal adhesions. The phenotypic changes resembled changes observed after treatment of the cells with cytochalasin D, which has been shown to interfere with CTGF induction. Concentrations of cucurbitacin I, which have been shown to target Jak2-STAT3 signalling, thus, profoundly affect the actin cytoskeleton and may therefore modulate cell morphology, migration, adherence and gene expression also in non-tumour cells.
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Affiliation(s)
- Angela Graness
- Department of Nephrology and Hypertension, University of Erlangen-Nuremberg, Loschgestrasse 8, D-91054 Erlangen, Germany
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43
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Rosenkilde MM, Benned-Jensen T, Andersen H, Holst PJ, Kledal TN, Lüttichau HR, Larsen JK, Christensen JP, Schwartz TW. Molecular Pharmacological Phenotyping of EBI2. J Biol Chem 2006; 281:13199-13208. [PMID: 16540462 DOI: 10.1074/jbc.m602245200] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Epstein-Barr virus (EBV)-induced receptor 2 (EBI2) is an orphan seven-transmembrane (7TM) receptor originally identified as the most up-regulated gene (>200-fold) in EBV-infected cells. Here we show that EBI2 signals with constitutive activity through Galpha(i) as determined by a receptor-mediated inhibition of forskolin-induced cAMP production and an induction of the serum response element-driven transcriptional activity in a pertussis toxin-sensitive manner. Galpha(s) and Galpha(q) were not activated constitutively as determined by the lack of cAMP production, the lack of inositol phosphate turnover, and the lack of activities of the transcription factors: cAMP response element-binding protein and nuclear factor-kappaB. Immunohistochemistry and confocal microscopy of FLAG- and green fluorescent protein-tagged EBI2 revealed cell-surface expression. A putative N-terminal truncated version of EBI2, delta4-EBI2, showed similar expression and signaling through Galpha(i) as full-length EBI2. By using a 32P-labeled EBI2 probe we found a very high expression in lymphoid tissue (spleen and lymph node) and peripheral blood mononuclear cells and a high expression in lung tissue. Real-time PCR of EBV-infected cells showed high expression of EBI2 during latent and lytic infection, in contrast to the EBV-encoded 7TM receptor BILF1, which was induced during lytic infection. EBI2 clustered with the orphan GPR18 by alignment analysis as well as by close proximity in the chromosomal region 13q32.3. Based on the constitutive signaling and cellular expression pattern of EBI2, it is suggested that it may function in conjunction with BILF1 in the reprogramming of the cell during EBV infection.
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Affiliation(s)
- Mette M Rosenkilde
- Laboratory for Molecular Pharmacology, Department of Pharmacology, University of Copenhagen, 2200 Copenhagen N, Copenhagen, Denmark.
| | - Tau Benned-Jensen
- Laboratory for Molecular Pharmacology, Department of Pharmacology, University of Copenhagen, 2200 Copenhagen N, Copenhagen, Denmark
| | - Helene Andersen
- Clinical Research Unit, Copenhagen University Hospital, 2650 Hvidovre, Denmark
| | - Peter J Holst
- Institute for Medical Microbiology and Immunology, The Panum Institute, Building 18.6, Blegdamsvej 3, 2200 Copenhagen N, Copenhagen, Denmark
| | - Thomas N Kledal
- Clinical Research Unit, Copenhagen University Hospital, 2650 Hvidovre, Denmark
| | - Hans R Lüttichau
- Laboratory for Molecular Pharmacology, Department of Pharmacology, University of Copenhagen, 2200 Copenhagen N, Copenhagen, Denmark; Department for Infectious Diseases, Copenhagen University Hospital, 2200 Copenhagen, Denmark
| | - Jørgen K Larsen
- Finsen Laboratory, The Finsen Center, Copenhagen University Hospital, 2200 Copenhagen, Denmark
| | - Jan P Christensen
- Institute for Medical Microbiology and Immunology, The Panum Institute, Building 18.6, Blegdamsvej 3, 2200 Copenhagen N, Copenhagen, Denmark
| | - Thue W Schwartz
- Laboratory for Molecular Pharmacology, Department of Pharmacology, University of Copenhagen, 2200 Copenhagen N, Copenhagen, Denmark
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44
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De Vries L, Palmier C, Finana F, Le Grand B, Perez M, Cussac D. Pharmacological characterization of protease activated receptor-1 by a serum responsive element-dependent reporter gene assay: Major role of calmodulin. Biochem Pharmacol 2006; 71:1449-58. [PMID: 16524561 DOI: 10.1016/j.bcp.2006.02.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2005] [Revised: 02/01/2006] [Accepted: 02/01/2006] [Indexed: 11/26/2022]
Abstract
We studied the protease activated receptor-1 coupling to a serum response element (SRE)-dependent luciferase activity readout in transfected COS-7 cells. Thrombin, with a pEC50 of 10.5, was 3000-fold more potent than the peptide agonists SFLLR and its derived compound C721-40 in stimulating luciferase activity, although the three agonists exhibited similar efficacy at the maximal concentration tested. Interestingly, SFLLR- and C721-40-induced luciferase activity was biphasic, suggesting that at least two populations of G proteins couple to the receptor. Further pharmacological characterization of this system was performed using selective protease activated receptor-1 antagonists. SCH203099 and ER-112787 blocked SFLLR-induced luciferase activity with similar potencies (pK(B) of 7), slightly higher than that exhibited by an arylisoxazole derivative compound from Merck (pK(B) of 6.1). These values correlated with their affinities established by competition binding experiments using [3H]-C721-40 as radioligand for protease activated receptor-1. Transduction mechanisms of protease activated receptor-1 coupling to SRE-dependent luciferase activity were examined using specific inhibitors. The Ca2+ chelator BAPTA-AM, as well as the calmodulin inhibitors W-7 and ophiobolin A, robustly inhibited SFLLR-induced SRE activation. Overexpression of RGS2 and a dominant negative rhoA protein abolished the SFLLR signal in an additive manner, suggesting a major role of Gq and G12/13 proteins. Furthermore, inhibition of phospholipase C, MAP-kinases, phosphatidyl inositol-3 kinase, rho-kinase and Ca2+/calmodulin-dependent protein kinases, all downstream effectors of Gq and G12/13, partially blocked the SFLLR-induced luciferase signal. Taken together, this SRE-luciferase assay reveals a complex network of transduction pathways of protease activated receptor-1 in accordance with the pleiotrophic action of thrombin.
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Affiliation(s)
- Luc De Vries
- Department of Cellular and Molecular Biology, Centre de Recherche Pierre Fabre, 17 Avenue Jean Moulin, 81106 Castres, France.
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Milasta S, Evans N, Ormiston L, Wilson S, Lefkowitz R, Milligan G. The sustainability of interactions between the orexin-1 receptor and beta-arrestin-2 is defined by a single C-terminal cluster of hydroxy amino acids and modulates the kinetics of ERK MAPK regulation. Biochem J 2006; 387:573-84. [PMID: 15683363 PMCID: PMC1134986 DOI: 10.1042/bj20041745] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The orexin-1 receptor interacts with beta-arrestin-2 in an agonist-dependent manner. In HEK-293T cells, these two proteins became co-internalized into acidic endosomes. Truncations from the C-terminal tail did not prevent agonist-induced internalization of the orexin-1 receptor or alter the pathway of internalization, although such mutants failed to interact with beta-arrestin-2 in a sustained manner or produce its co-internalization. Mutation of a cluster of three threonine and one serine residue at the extreme C-terminus of the receptor greatly reduced interaction and abolished co-internalization of beta-arrestin-2-GFP (green fluorescent protein). Despite the weak interactions of this C-terminally mutated form of the receptor with beta-arrestin-2, studies in wild-type and beta-arrestin-deficient mouse embryo fibroblasts confirmed that agonist-induced internalization of this mutant required expression of a beta-arrestin. Although without effect on agonist-mediated elevation of intracellular Ca2+ levels, the C-terminally mutated form of the orexin-1 receptor was unable to sustain phosphorylation of the MAPKs (mitogen-activated protein kinases) ERK1 and ERK2 (extracellular-signal-regulated kinases 1 and 2) to the same extent as the wild-type receptor. These studies indicate that a single cluster of hydroxy amino acids within the C-terminal seven amino acids of the orexin-1 receptor determine the sustainability of interaction with beta-arrestin-2, and indicate an important role of beta-arrestin scaffolding in defining the kinetics of orexin-1 receptor-mediated ERK MAPK activation.
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Affiliation(s)
- Sandra Milasta
- *Molecular Pharmacology Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, U.K
| | - Nicholas A. Evans
- †GlaxoSmithKline, New Frontiers Science Park, Third Avenue, Harlow, Essex CM19 5AW, U.K
| | - Laura Ormiston
- *Molecular Pharmacology Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, U.K
| | - Shelagh Wilson
- †GlaxoSmithKline, New Frontiers Science Park, Third Avenue, Harlow, Essex CM19 5AW, U.K
| | - Robert J. Lefkowitz
- ‡Department of Medicine, HHMI/Duke University Medical Center, Durham, NC 27710, U.S.A
| | - Graeme Milligan
- *Molecular Pharmacology Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, U.K
- To whom correspondence should be addressed (email )
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Kvachnina E, Liu G, Dityatev A, Renner U, Dumuis A, Richter DW, Dityateva G, Schachner M, Voyno-Yasenetskaya TA, Ponimaskin EG. 5-HT7 receptor is coupled to G alpha subunits of heterotrimeric G12-protein to regulate gene transcription and neuronal morphology. J Neurosci 2006; 25:7821-30. [PMID: 16120784 PMCID: PMC6725246 DOI: 10.1523/jneurosci.1790-05.2005] [Citation(s) in RCA: 151] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The neurotransmitter serotonin (5-HT) plays an important role in the regulation of multiple events in the CNS. We demonstrated recently a coupling between the 5-HT4 receptor and the heterotrimeric G13-protein resulting in RhoA-dependent neurite retraction and cell rounding (Ponimaskin et al., 2002). In the present study, we identified G12 as an additional G-protein that can be activated by another member of serotonin receptors, the 5-HT7 receptor. Expression of 5-HT7 receptor induced constitutive and agonist-dependent activation of a serum response element-mediated gene transcription through G12-mediated activation of small GTPases. In NIH3T3 cells, activation of the 5-HT7 receptor induced filopodia formation via a Cdc42-mediated pathway correlating with RhoA-dependent cell rounding. In mouse hippocampal neurons, activation of the endogenous 5-HT7 receptors significantly increased neurite length, whereas stimulation of 5-HT4 receptors led to a decrease in the length and number of neurites. These data demonstrate distinct roles for 5-HT7R/G12 and 5-HT4R/G13 signaling pathways in neurite outgrowth and retraction, suggesting that serotonin plays a prominent role in regulating the neuronal cytoarchitecture in addition to its classical role as neurotransmitter.
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MESH Headings
- Animals
- Cells, Cultured
- GTP-Binding Protein alpha Subunits, G12-G13/genetics
- GTP-Binding Protein alpha Subunits, G12-G13/metabolism
- Mice
- NIH 3T3 Cells
- Neurites/physiology
- Neurons/cytology
- Neurons/metabolism
- Receptors, G-Protein-Coupled/agonists
- Receptors, G-Protein-Coupled/antagonists & inhibitors
- Receptors, G-Protein-Coupled/genetics
- Receptors, G-Protein-Coupled/metabolism
- Receptors, Serotonin/genetics
- Receptors, Serotonin/metabolism
- Serotonin/physiology
- Serotonin Antagonists/pharmacology
- Signal Transduction/physiology
- Transcription, Genetic/physiology
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Affiliation(s)
- Elena Kvachnina
- Abteilung Neurologie und Sinnesphysiologie, Physiologisches Institut, Universität Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
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Rimler A, Jockers R, Lupowitz Z, Sampson SR, Zisapel N. Differential effects of melatonin and its downstream effector PKCalpha on subcellular localization of RGS proteins. J Pineal Res 2006; 40:144-52. [PMID: 16441551 DOI: 10.1111/j.1600-079x.2005.00290.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Regulators of G protein signaling (RGS) are proteins that bind specifically to activated Galpha subunits of heterotrimeric G proteins to terminate signaling by both Galpha and Gbetagamma subunits. Signal-induced RGS redistribution may affect their activity in G protein-mediated signaling. We have previously shown that melatonin and the cell permeable cGMP analog 8-bromo cGMP, which lead to protein kinase C (PKC) activation, enhanced cytoplasmic distribution of RGS10 and RGS2 in prostate carcinoma PC3-AR cells. In the present study, we transfected PC3-AR cells with myc-tagged Galphai/Galphaq specific RGS proteins RGS2, RGS4 and RGS10 and examined the effects of melatonin, 8-bromo cGMP and PKC inhibitors on their nuclear-cytoplasmic partitioning. RGS10 and RGS2 were predominantly localized in the nucleus and perinuclear regions whereas RGS4 was mostly cytoplasmic in the PC3-AR cells. Melatonin and the cell permeable cGMP analog 8-bromo cGMP, previously found to activate PKCalpha in the PC3-AR cells, enhanced cytoplasmic localization of RGS10 and RGS2 but induced nuclear accumulation of RGS4. The isozyme specific PKC inhibitor GO6976 (PKCalpha and PKCbeta1) but not hispidin (PKCbeta) negated the effects of melatonin on RGS10, RGS2 and RGS4 localization. These findings indicate that PKCalpha, a downstream effector of the melatonin receptor, differentially affects nuclear/cytoplasmic localization of both Galphai and Galphaq specific RGS proteins. These observations provide further insight into melatonin's ability to fine-tune multiple membrane G-proteins signaling in cells.
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Affiliation(s)
- Avi Rimler
- Department of Neurobiochemistry, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
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Abstract
Chemotaxis is a fascinating biological process, through which a cell migrates along a shallow chemoattractant gradient that is less than 5% difference between the anterior and posterior of the cell. Chemotaxis is composed of two independent, but interrelated processes--motility and directionality--both of which are regulated by extracellular stimuli and chemoattractants; small GTPases have been shown to be involved. In this chapter, the methods that are used to prepare mouse neutrophils and study their chemotactic behaviors and morphological and biochemical changes in response to chemoattractant stimulation are described.
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Affiliation(s)
- Xuemei Dong
- Department of Genetics & Developmental Biology, University of Connecticut Health Center, Farmington, USA
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49
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Orth JHC, Lang S, Taniguchi M, Aktories K. Pasteurella multocida Toxin-induced Activation of RhoA Is Mediated via Two Families of Gα Proteins, Gαq and Gα12/13. J Biol Chem 2005; 280:36701-7. [PMID: 16141214 DOI: 10.1074/jbc.m507203200] [Citation(s) in RCA: 63] [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
Pasteurella multocida toxin (PMT) is a potent mitogen, which is known to activate phospholipase Cbeta by stimulating the alpha-subunit of the heterotrimeric G protein G(q). PMT also activates RhoA and RhoA-dependent pathways. Using YM-254890, a specific inhibitor of G(q/11), we studied whether activation of RhoA involves G proteins other than G(q/11). YM-254890 inhibited PMT or muscarinic M3-receptor-mediated stimulation of phospholipase Cbeta at similar concentrations in HEK293m3 cells. In these cells, PMT-induced RhoA activation and enhancement of RhoA-dependent luciferase activity were partially inhibited by YM-254890. In Galpha(q/11)-deficient fibroblasts, PMT induced activation of RhoA, increase in RhoA-dependent luciferase activity, and increase in ERK phosphorylation. None of these effects were influenced by YM-254890. However, RhoA activation by PMT was inhibited by RGS2, RGS16, lscRGS, and dominant negative G(13)(GA), indicating involvement of Galpha(12/13) in the PMT effect on RhoA. In Galpha(12/13) gene-deficient cells, PMT-induced stimulation of RhoA, luciferase activity, and ERK phosphorylation were blocked by YM-254890, indicating the involvement of G(q). Infection with a virus harboring the gene of Galpha(13) reconstituted the increase in RhoA-dependent luciferase activity by PMT even in the presence of YM-254890. The data show that YM-254890 is able to block PMT activation of Galpha(q) and indicate that, in addition to Galpha(q), the Galpha(12/13) G proteins are targets of PMT.
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Affiliation(s)
- Joachim H C Orth
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Albert-Ludwigs Universität Freiburg, D-79104 Freiburg, Germany
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50
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Abstract
Rho proteins are master regulators of a large array of cellular functions, including control of cell morphology, cell migration and polarity, transcriptional activation, and cell cycle progression. They are the eukaryotic targets of various bacterial protein toxins and effectors, which activate or inactivate the GTPases. Here Rho-inactivating toxins and effectors are reviewed, including the families of large clostridial cytotoxins and C3-like transferases, which inactivate Rho GTPases by glucosylation and ADP-ribosylation, respectively.
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Affiliation(s)
- K Aktories
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Albertstrasse 25, 79104 Freiburg, Germany.
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