1
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Hassan MA, Fukui T, Shimizu H, Kishimoto K. G2A as a key modulator of carbonyl stress and apoptosis resistance in glucose-loaded cancer cells. Biochem Biophys Res Commun 2024; 736:150516. [PMID: 39121674 DOI: 10.1016/j.bbrc.2024.150516] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2024] [Revised: 08/02/2024] [Accepted: 08/06/2024] [Indexed: 08/12/2024]
Abstract
Cancer cells exhibit high glycolytic activity, metabolizing glucose as their primary energy substrate. Toxic metabolites produced during glycolysis, such as methylglyoxal, induce carbonyl stress (CS), promoting inflammation and oxidative stress. The elevated glucose metabolism in cancer cells creates this toxic environment. However, little research has focused on the molecules mediating these reactions and stresses, and their role in selecting and enriching apoptosis-resistant cells. This study investigated the impact of constitutively suppressing oxidized lipid receptor G2A (GPR132) expression on the relationship between CS and oxidative stress in glucose-loaded cancer cells. G2A has recently attracted attention as a tumor promoter. However, our study shows that G2A suppression under glucose loading significantly reduces CS and associated oxidative stress, thereby enhancing cancer cell survival. This suggests a new mechanism contrary to conventional thinking, involving the acute induction of glyoxalase 1 (Glo1). G2A may thus play a role in selecting and enriching apoptosis-resistant cell populations under high glucose conditions by regulating Glo1 expression. These findings improve our understanding of the adaptive capacity of cancer cells to glucose toxicity.
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Affiliation(s)
- Md Abul Hassan
- Faculty of Bioscience and Bioindustry, Tokushima University Graduate School of Advanced Technology and Science, Tokushima, Japan
| | - Takahito Fukui
- Faculty of Bioresource Science, Tokushima University Graduate School of Sciences and Technology for Innovation, Tokushima, Japan
| | - Hidetaka Shimizu
- Faculty of Bioresource Science, Tokushima University Graduate School of Sciences and Technology for Innovation, Tokushima, Japan
| | - Koji Kishimoto
- Division of Bioscience and Bioindustry, Tokushima University Graduate School of Technology, Industrial and Social Sciences, Tokushima, Japan.
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2
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Ji R, Chang L, An C, Zhang J. Proton-sensing ion channels, GPCRs and calcium signaling regulated by them: implications for cancer. Front Cell Dev Biol 2024; 12:1326231. [PMID: 38505262 PMCID: PMC10949864 DOI: 10.3389/fcell.2024.1326231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2023] [Accepted: 02/14/2024] [Indexed: 03/21/2024] Open
Abstract
Extracellular acidification of tumors is common. Through proton-sensing ion channels or proton-sensing G protein-coupled receptors (GPCRs), tumor cells sense extracellular acidification to stimulate a variety of intracellular signaling pathways including the calcium signaling, which consequently exerts global impacts on tumor cells. Proton-sensing ion channels, and proton-sensing GPCRs have natural advantages as drug targets of anticancer therapy. However, they and the calcium signaling regulated by them attracted limited attention as potential targets of anticancer drugs. In the present review, we discuss the progress in studies on proton-sensing ion channels, and proton-sensing GPCRs, especially emphasizing the effects of calcium signaling activated by them on the characteristics of tumors, including proliferation, migration, invasion, metastasis, drug resistance, angiogenesis. In addition, we review the drugs targeting proton-sensing channels or GPCRs that are currently in clinical trials, as well as the relevant potential drugs for cancer treatments, and discuss their future prospects. The present review aims to elucidate the important role of proton-sensing ion channels, GPCRs and calcium signaling regulated by them in cancer initiation and development. This review will promote the development of drugs targeting proton-sensing channels or GPCRs for cancer treatments, effectively taking their unique advantage as anti-cancer drug targets.
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Affiliation(s)
- Renhui Ji
- Foundational and Translational Medical Research Center, Department of Allergy and General Surgery, Hohhot First Hospital, Hohhot, China
- Department of Pathophysiology, Basic Medicine College of Inner Mongolia Medical University, Hohhot, China
| | - Li Chang
- Foundational and Translational Medical Research Center, Department of Allergy and General Surgery, Hohhot First Hospital, Hohhot, China
- Department of Pathophysiology, Basic Medicine College of Inner Mongolia Medical University, Hohhot, China
| | - Caiyan An
- Foundational and Translational Medical Research Center, Department of Allergy and General Surgery, Hohhot First Hospital, Hohhot, China
| | - Junjing Zhang
- Foundational and Translational Medical Research Center, Department of Allergy and General Surgery, Hohhot First Hospital, Hohhot, China
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3
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Steffan BN, Calise D, Park SC, Niu M, Yang J, Hammock BD, Jones M, Steele C, Keller NP. Loss of the mammalian G-protein coupled receptor, G2A, modulates severity of invasive pulmonary aspergillosis. Front Immunol 2023; 14:1173544. [PMID: 37435068 PMCID: PMC10331294 DOI: 10.3389/fimmu.2023.1173544] [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: 02/24/2023] [Accepted: 06/01/2023] [Indexed: 07/13/2023] Open
Abstract
Background Aspergillus fumigatus is a well-known opportunistic pathogen that causes a range of diseases including the often-fatal disease, invasive pulmonary aspergillosis (IPA), in immunocompromised populations. The severity of IPA is dependent on both host- and pathogen-derived signaling molecules that mediate host immunity and fungal growth. Oxylipins are bioactive oxygenated fatty acids known to influence host immune response and Aspergillus developmental programs. Aspergillus synthesizes 8-HODE and 5,8-diHODE that have structural similarities to 9-HODE and 13-HODE, which are known ligands of the host G-protein-coupled receptor G2A (GPR132). Materials and methods Oxylipins were extracted from infected lung tissue to assess fungal oxylipin production and the Pathhunter β-arrestin assay was used to assess agonist and antagonist activity by fungal oxylipins on G2A. An immunocompetent model of A. fumigatus infection was used to assess changes in survival and immune responses for G2A-/- mice. Results Here we report that Aspergillus oxylipins are produced in lung tissue of infected mice and in vitro ligand assays suggest 8-HODE is a G2A agonist and 5,8-diHODE is a partial antagonist. To address the hypothesis that G2A could be involved in the progression of IPA, we assessed the response of G2A-/- mice to A. fumigatus infection. G2A-/- mice showed a survival advantage over wild-type mice; this was accompanied by increased recruitment of G2A-/- neutrophils and increased levels of inflammatory markers in A. fumigatus-infected lungs. Conclusions We conclude that G2A suppresses host inflammatory responses to Aspergillus fumigatus although it remains unclear if fungal oxylipins are involved in G2A activities.
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Affiliation(s)
- Breanne N. Steffan
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, United States
| | - Dante Calise
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, United States
| | - Sung Chul Park
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, United States
| | - Mengyao Niu
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, United States
| | - Jun Yang
- Department of Entomology, University of California-Davis, Davis, CA, United States
| | - Bruce D. Hammock
- Department of Entomology, University of California-Davis, Davis, CA, United States
| | - MaryJane Jones
- Department of Microbiology and Immunology, School of Medicine, Tulane University, New Orleans, LA, United States
| | - Chad Steele
- Department of Microbiology and Immunology, School of Medicine, Tulane University, New Orleans, LA, United States
| | - Nancy P. Keller
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, United States
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, WI, United States
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4
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Korbecki J, Rębacz-Maron E, Kupnicka P, Chlubek D, Baranowska-Bosiacka I. Synthesis and Significance of Arachidonic Acid, a Substrate for Cyclooxygenases, Lipoxygenases, and Cytochrome P450 Pathways in the Tumorigenesis of Glioblastoma Multiforme, Including a Pan-Cancer Comparative Analysis. Cancers (Basel) 2023; 15:cancers15030946. [PMID: 36765904 PMCID: PMC9913267 DOI: 10.3390/cancers15030946] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2022] [Revised: 01/25/2023] [Accepted: 01/31/2023] [Indexed: 02/05/2023] Open
Abstract
Glioblastoma multiforme (GBM) is one of the most aggressive gliomas. New and more effective therapeutic approaches are being sought based on studies of the various mechanisms of GBM tumorigenesis, including the synthesis and metabolism of arachidonic acid (ARA), an omega-6 polyunsaturated fatty acid (PUFA). PubMed, GEPIA, and the transcriptomics analysis carried out by Seifert et al. were used in writing this paper. In this paper, we discuss in detail the biosynthesis of this acid in GBM tumors, with a special focus on certain enzymes: fatty acid desaturase (FADS)1, FADS2, and elongation of long-chain fatty acids family member 5 (ELOVL5). We also discuss ARA metabolism, particularly its release from cell membrane phospholipids by phospholipase A2 (cPLA2, iPLA2, and sPLA2) and its processing by cyclooxygenases (COX-1 and COX-2), lipoxygenases (5-LOX, 12-LOX, 15-LOX-1, and 15-LOX-2), and cytochrome P450. Next, we discuss the significance of lipid mediators synthesized from ARA in GBM cancer processes, including prostaglandins (PGE2, PGD2, and 15-deoxy-Δ12,14-PGJ2 (15d-PGJ2)), thromboxane A2 (TxA2), oxo-eicosatetraenoic acids, leukotrienes (LTB4, LTC4, LTD4, and LTE4), lipoxins, and many others. These lipid mediators can increase the proliferation of GBM cancer cells, cause angiogenesis, inhibit the anti-tumor response of the immune system, and be responsible for resistance to treatment.
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Affiliation(s)
- Jan Korbecki
- Department of Biochemistry and Medical Chemistry, Pomeranian Medical University in Szczecin, Powstańców Wlkp. 72, 70-111 Szczecin, Poland
| | - Ewa Rębacz-Maron
- Department of Ecology and Anthropology, Institute of Biology, University of Szczecin, Wąska 13, 71-415 Szczecin, Poland
| | - Patrycja Kupnicka
- Department of Biochemistry and Medical Chemistry, Pomeranian Medical University in Szczecin, Powstańców Wlkp. 72, 70-111 Szczecin, Poland
| | - Dariusz Chlubek
- Department of Biochemistry and Medical Chemistry, Pomeranian Medical University in Szczecin, Powstańców Wlkp. 72, 70-111 Szczecin, Poland
| | - Irena Baranowska-Bosiacka
- Department of Biochemistry and Medical Chemistry, Pomeranian Medical University in Szczecin, Powstańców Wlkp. 72, 70-111 Szczecin, Poland
- Correspondence: ; Tel.: +48-914-661-515
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5
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Understanding the Contribution of Lactate Metabolism in Cancer Progress: A Perspective from Isomers. Cancers (Basel) 2022; 15:cancers15010087. [PMID: 36612084 PMCID: PMC9817756 DOI: 10.3390/cancers15010087] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Revised: 12/13/2022] [Accepted: 12/21/2022] [Indexed: 12/28/2022] Open
Abstract
Lactate mediates multiple cell-intrinsic effects in cancer metabolism in terms of development, maintenance, and metastasis and is often correlated with poor prognosis. Its functions are undertaken as an energy source for neighboring carcinoma cells and serve as a lactormone for oncogenic signaling pathways. Indeed, two isomers of lactate are produced in the Warburg effect: L-lactate and D-lactate. L-lactate is the main end-production of glycolytic fermentation which catalyzes glucose, and tiny D-lactate is fabricated through the glyoxalase system. Their production inevitably affects cancer development and therapy. Here, we systematically review the mechanisms of lactate isomers production, and highlight emerging evidence of the carcinogenic biological effects of lactate and its isomers in cancer. Accordingly, therapy that targets lactate and its metabolism is a promising approach for anticancer treatment.
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6
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Ion Channels, Transporters, and Sensors Interact with the Acidic Tumor Microenvironment to Modify Cancer Progression. Rev Physiol Biochem Pharmacol 2021; 182:39-84. [PMID: 34291319 DOI: 10.1007/112_2021_63] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Solid tumors, including breast carcinomas, are heterogeneous but typically characterized by elevated cellular turnover and metabolism, diffusion limitations based on the complex tumor architecture, and abnormal intra- and extracellular ion compositions particularly as regards acid-base equivalents. Carcinogenesis-related alterations in expression and function of ion channels and transporters, cellular energy levels, and organellar H+ sequestration further modify the acid-base composition within tumors and influence cancer cell functions, including cell proliferation, migration, and survival. Cancer cells defend their cytosolic pH and HCO3- concentrations better than normal cells when challenged with the marked deviations in extracellular H+, HCO3-, and lactate concentrations typical of the tumor microenvironment. Ionic gradients determine the driving forces for ion transporters and channels and influence the membrane potential. Cancer and stromal cells also sense abnormal ion concentrations via intra- and extracellular receptors that modify cancer progression and prognosis. With emphasis on breast cancer, the current review first addresses the altered ion composition and the changes in expression and functional activity of ion channels and transporters in solid cancer tissue. It then discusses how ion channels, transporters, and cellular sensors under influence of the acidic tumor microenvironment shape cancer development and progression and affect the potential of cancer therapies.
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7
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Cosín-Roger J, Ortiz-Masia D, Barrachina MD, Calatayud S. Metabolite Sensing GPCRs: Promising Therapeutic Targets for Cancer Treatment? Cells 2020; 9:cells9112345. [PMID: 33113952 PMCID: PMC7690732 DOI: 10.3390/cells9112345] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 10/21/2020] [Accepted: 10/21/2020] [Indexed: 02/07/2023] Open
Abstract
G-protein-coupled receptors constitute the most diverse and largest receptor family in the human genome, with approximately 800 different members identified. Given the well-known metabolic alterations in cancer development, we will focus specifically in the 19 G-protein-coupled receptors (GPCRs), which can be selectively activated by metabolites. These metabolite sensing GPCRs control crucial processes, such as cell proliferation, differentiation, migration, and survival after their activation. In the present review, we will describe the main functions of these metabolite sensing GPCRs and shed light on the benefits of their potential use as possible pharmacological targets for cancer treatment.
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Affiliation(s)
- Jesús Cosín-Roger
- Hospital Dr. Peset, Fundación para la Investigación Sanitaria y Biomédica de la Comunitat Valenciana, FISABIO, 46017 Valencia, Spain
- Correspondence: ; Tel.: +34-963851234
| | - Dolores Ortiz-Masia
- Departament of Medicine, Faculty of Medicine, University of Valencia, 46010 Valencia, Spain;
| | - Maria Dolores Barrachina
- Departament of Pharmacology and CIBER, Faculty of Medicine, University of Valencia, 46010 Valencia, Spain; (M.D.B.); (S.C.)
| | - Sara Calatayud
- Departament of Pharmacology and CIBER, Faculty of Medicine, University of Valencia, 46010 Valencia, Spain; (M.D.B.); (S.C.)
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8
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Wang T, Zhou G, He M, Xu Y, Rusyniak WG, Xu Y, Ji Y, Simon RP, Xiong ZG, Zha XM. GPR68 Is a Neuroprotective Proton Receptor in Brain Ischemia. Stroke 2020; 51:3690-3700. [PMID: 33059544 PMCID: PMC7678672 DOI: 10.1161/strokeaha.120.031479] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Supplemental Digital Content is available in the text. Brain acidosis is prevalent in stroke and other neurological diseases. Acidosis can have paradoxical injurious and protective effects. The purpose of this study is to determine whether a proton receptor exists in neurons to counteract acidosis-induced injury.
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Affiliation(s)
- Tao Wang
- Department of Physiology and Cell Biology (T.W., G.Z., M.H., Yuanyuan Xu, X.-m.Z.), University of South Alabama College of Medicine, Mobile
| | - Guokun Zhou
- Department of Physiology and Cell Biology (T.W., G.Z., M.H., Yuanyuan Xu, X.-m.Z.), University of South Alabama College of Medicine, Mobile.,Laboratory of Neuropharmacology and Neurotoxicology, Shanghai University, China (G.Z., Y.J.)
| | - Mindi He
- Department of Physiology and Cell Biology (T.W., G.Z., M.H., Yuanyuan Xu, X.-m.Z.), University of South Alabama College of Medicine, Mobile
| | - Yuanyuan Xu
- Department of Physiology and Cell Biology (T.W., G.Z., M.H., Yuanyuan Xu, X.-m.Z.), University of South Alabama College of Medicine, Mobile
| | - W G Rusyniak
- Department of Neurosurgery (W.G.R.), University of South Alabama College of Medicine, Mobile
| | - Yan Xu
- Department of Obstetrics and Gynecology, Indiana University School of Medicine, Indianapolis (Yan Xu)
| | - Yonghua Ji
- Laboratory of Neuropharmacology and Neurotoxicology, Shanghai University, China (G.Z., Y.J.)
| | - Roger P Simon
- Department of Neurobiology, Morehouse School of Medicine, Atlanta, GA (R.P.S., Z.-G.X.)
| | - Zhi-Gang Xiong
- Department of Neurobiology, Morehouse School of Medicine, Atlanta, GA (R.P.S., Z.-G.X.)
| | - Xiang-Ming Zha
- Department of Physiology and Cell Biology (T.W., G.Z., M.H., Yuanyuan Xu, X.-m.Z.), University of South Alabama College of Medicine, Mobile
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9
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Klatt W, Wallner S, Brochhausen C, Stolwijk JA, Schreml S. Expression profiles of proton-sensing G-protein coupled receptors in common skin tumors. Sci Rep 2020; 10:15327. [PMID: 32948783 PMCID: PMC7501253 DOI: 10.1038/s41598-020-71700-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Accepted: 08/19/2020] [Indexed: 12/18/2022] Open
Abstract
The proton-sensing GPCRs (pH-GPCRs) GPR4 (GPR19), TDAG8 (GPR65, T-cell death associated gene 8), OGR1 (GPR68, ovarian cancer GPCR1), and G2A (GPR132, G2 accumulation protein) are involved in sensing and transducing changes in extracellular pH (pHe). Extracellular acidification is a central hallmark of solid cancer. pH-GPCR function has been associated with cancer cell proliferation, adhesion, migration and metastasis, as well as with modulation of the immune system. Little is known about the expression levels and role of pH-GPCRs in skin cancer. To better understand the functions of pH-GPCRs in skin cancer in vivo, we examined the expression-profiles of GPR4, TDAG8, OGR1 and G2A in four common skin tumors, i.e. squamous cell carcinoma (SCC), malignant melanoma (MM), compound nevus cell nevi (NCN), basal cell carcinoma (BCC). We performed immunohistochemistry and immunofluorescence staining on paraffin-embedded tissue samples acquired from patients suffering from SCC, MM, NCN or BCC. We show the expression of pH-GPCRs in four common skin cancers. Different expression patterns in the investigated skin cancer types indicate that the different pH-GPCRs may have distinct functions in tumor progression and serve as novel therapeutic targets.
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Affiliation(s)
- Wybke Klatt
- Department of Dermatology, University Medical Center Regensburg, Franz-Josef-Strauß-Allee 11, 93053, Regensburg, Germany
| | - Susanne Wallner
- Department of Dermatology, University Medical Center Regensburg, Franz-Josef-Strauß-Allee 11, 93053, Regensburg, Germany
| | - Christoph Brochhausen
- Institute of Pathology, University of Regensburg, Franz-Josef-Strauß-Allee 11, 93053, Regensburg, Germany
| | - Judith A Stolwijk
- Department of Dermatology, University Medical Center Regensburg, Franz-Josef-Strauß-Allee 11, 93053, Regensburg, Germany
- Institute of Analytical Chemistry, Chemo- and Biosensors, Faculty of Chemistry and Pharmacy, University of Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany
| | - Stephan Schreml
- Department of Dermatology, University Medical Center Regensburg, Franz-Josef-Strauß-Allee 11, 93053, Regensburg, Germany.
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10
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Stolwijk JA, Sauer L, Ackermann K, Nassios A, Aung T, Haerteis S, Bäumner AJ, Wegener J, Schreml S. pH sensing in skin tumors: Methods to study the involvement of GPCRs, acid-sensing ion channels and transient receptor potential vanilloid channels. Exp Dermatol 2020; 29:1055-1061. [PMID: 32658355 DOI: 10.1111/exd.14150] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Revised: 07/01/2020] [Accepted: 07/06/2020] [Indexed: 12/19/2022]
Abstract
Solid tumors exhibit an inversed pH gradient with increased intracellular pH (pHi ) and decreased extracellular pH (pHe ). This inside-out pH gradient is generated via sodium/hydrogen antiporter 1, vacuolar-type H + ATPases, monocarboxylate transporters, (bi)carbonate (co)transporters and carboanhydrases. Our knowledge on how pHe -signals are sensed and what the respective receptors induce inside cells is scarce. Some pH-sensitive receptors (GPR4, GPR65/TDAG8, GPR68/OGR1, GPR132/G2A, possibly GPR31 and GPR151) and ion channels (acid-sensing ion channels ASICs, transient receptor potential vanilloid receptors TRPVs) transduce signals inside cells. As little is known on the expression and function of these pH sensors, we used immunostainings to study tissue samples from common and rare skin cancers. Our current and future work is directed towards investigating the impact of all the pH-sensing receptors in different skin tumors using cell culture techniques with selective knockdown/knockout (siRNA/CRISPR-Cas9). To study cell migration and proliferation, novel impedance-based wound healing assays have been developed and are used. The field of pH sensing in tumors and wounds holds great promise for the development of pH-targeting therapies, either against pH regulators or sensors to inhibit cell proliferation and migration.
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Affiliation(s)
- Judith A Stolwijk
- Department of Dermatology, University Medical Center Regensburg, Regensburg, Germany.,Institute of Analytical Chemistry, Chemo- and Biosensors, Faculty of Chemistry and Pharmacy, University of Regensburg, Regensburg, Germany
| | - Lisa Sauer
- Institute of Analytical Chemistry, Chemo- and Biosensors, Faculty of Chemistry and Pharmacy, University of Regensburg, Regensburg, Germany
| | - Kirsten Ackermann
- Department of Dermatology, University Medical Center Regensburg, Regensburg, Germany
| | - Anaïs Nassios
- Department of Dermatology, University Medical Center Regensburg, Regensburg, Germany
| | - Thiha Aung
- Centre of Plastic, Aesthetic, Hand and Reconstructive Surgery, University Medical Center Regensburg, Regensburg, Germany
| | - Silke Haerteis
- Institute of Molecular and Cellular Anatomy, University of Regensburg, Regensburg, Germany
| | - Antje J Bäumner
- Institute of Analytical Chemistry, Chemo- and Biosensors, Faculty of Chemistry and Pharmacy, University of Regensburg, Regensburg, Germany
| | - Joachim Wegener
- Institute of Analytical Chemistry, Chemo- and Biosensors, Faculty of Chemistry and Pharmacy, University of Regensburg, Regensburg, Germany
| | - Stephan Schreml
- Department of Dermatology, University Medical Center Regensburg, Regensburg, Germany
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11
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Ward C, Meehan J, Gray ME, Murray AF, Argyle DJ, Kunkler IH, Langdon SP. The impact of tumour pH on cancer progression: strategies for clinical intervention. EXPLORATION OF TARGETED ANTI-TUMOR THERAPY 2020; 1:71-100. [PMID: 36046070 PMCID: PMC9400736 DOI: 10.37349/etat.2020.00005] [Citation(s) in RCA: 54] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2019] [Accepted: 02/05/2020] [Indexed: 02/06/2023] Open
Abstract
Dysregulation of cellular pH is frequent in solid tumours and provides potential opportunities for therapeutic intervention. The acidic microenvironment within a tumour can promote migration, invasion and metastasis of cancer cells through a variety of mechanisms. Pathways associated with the control of intracellular pH that are under consideration for intervention include carbonic anhydrase IX, the monocarboxylate transporters (MCT, MCT1 and MCT4), the vacuolar-type H+-ATPase proton pump, and the sodium-hydrogen exchanger 1. This review will describe progress in the development of inhibitors to these targets.
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Affiliation(s)
- Carol Ward
- Cancer Research UK Edinburgh Centre and Edinburgh Pathology, Institute of Genetics and Molecular Medicine, University of Edinburgh, Crewe Road South, EH4 2XU Edinburgh, UK
| | - James Meehan
- Cancer Research UK Edinburgh Centre and Edinburgh Pathology, Institute of Genetics and Molecular Medicine, University of Edinburgh, Crewe Road South, EH4 2XU Edinburgh, UK
| | - Mark E Gray
- Royal (Dick) School of Veterinary Studies and Roslin Institute, University of Edinburgh, Easter Bush, EH25 9RG Midlothian, UK
| | - Alan F Murray
- School of Engineering, Institute for Integrated Micro and Nano Systems, EH9 3JL Edinburgh, UK
| | - David J Argyle
- Royal (Dick) School of Veterinary Studies and Roslin Institute, University of Edinburgh, Easter Bush, EH25 9RG Midlothian, UK
| | - Ian H Kunkler
- Cancer Research UK Edinburgh Centre and Edinburgh Pathology, Institute of Genetics and Molecular Medicine, University of Edinburgh, Crewe Road South, EH4 2XU Edinburgh, UK
| | - Simon P Langdon
- Cancer Research UK Edinburgh Centre and Edinburgh Pathology, Institute of Genetics and Molecular Medicine, University of Edinburgh, Crewe Road South, EH4 2XU Edinburgh, UK
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12
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Bond J, Domaschenz R, Roman-Trufero M, Sabbattini P, Ferreiros-Vidal I, Gerrard G, Asnafi V, Macintyre E, Merkenschlager M, Dillon N. Direct interaction of Ikaros and Foxp1 modulates expression of the G protein-coupled receptor G2A in B-lymphocytes and acute lymphoblastic leukemia. Oncotarget 2018; 7:65923-65936. [PMID: 27588474 PMCID: PMC5323203 DOI: 10.18632/oncotarget.11688] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2016] [Accepted: 08/13/2016] [Indexed: 12/13/2022] Open
Abstract
Ikaros and Foxp1 are transcription factors that play key roles in normal lymphopoiesis and lymphoid malignancies. We describe a novel physical and functional interaction between the proteins, which requires the central zinc finger domain of Ikaros. The Ikaros-Foxp1 interaction is abolished by deletion of this region, which corresponds to the IK6 isoform that is commonly associated with high-risk acute lymphoblastic leukemia (ALL). We also identify the Gpr132 gene, which encodes the orphan G protein-coupled receptor G2A, as a novel target for Foxp1. Increased expression of Foxp1 enhanced Gpr132 transcription and caused cell cycle changes, including G2 arrest. Co-expression of wild-type Ikaros, but not IK6, displaced Foxp1 binding from the Gpr132 gene, reversed the increase in Gpr132 expression and inhibited G2 arrest. Analysis of primary ALL samples revealed a significant increase in GPR132 expression in IKZF1-deleted BCR-ABL negative patients, suggesting that levels of wild-type Ikaros may influence the regulation of G2A in B-ALL. Our results reveal a novel effect of Ikaros haploinsufficiency on Foxp1 functioning, and identify G2A as a potential modulator of the cell cycle in Ikaros-deleted B-ALL.
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Affiliation(s)
- Jonathan Bond
- Gene Regulation and Chromatin Group, MRC Clinical Sciences Centre, Imperial College Faculty of Medicine, Hammersmith Campus, London W12 0NN, United Kingdom.,Université Paris Descartes Sorbonne Cité, Institut Necker-Enfants Malades (INEM), Institut National de Recherche Médicale (INSERM), and Laboratory of Onco-Hematology, Assistance Publique-Hôpitaux de Paris (AP-HP), Hôpital Necker Enfants-Malades, Paris, France
| | - Renae Domaschenz
- Gene Regulation and Chromatin Group, MRC Clinical Sciences Centre, Imperial College Faculty of Medicine, Hammersmith Campus, London W12 0NN, United Kingdom.,Present address: Chromatin and Transcriptional Regulation Group, John Curtin School of Medical Research, The Australian National University, Canberra, Australian Capital Territory, Australia
| | - Mónica Roman-Trufero
- Gene Regulation and Chromatin Group, MRC Clinical Sciences Centre, Imperial College Faculty of Medicine, Hammersmith Campus, London W12 0NN, United Kingdom
| | - Pierangela Sabbattini
- Gene Regulation and Chromatin Group, MRC Clinical Sciences Centre, Imperial College Faculty of Medicine, Hammersmith Campus, London W12 0NN, United Kingdom
| | - Isabel Ferreiros-Vidal
- Lymphocyte Development Group, MRC Clinical Sciences Centre, Imperial College Faculty of Medicine, Hammersmith Campus, London W12 0NN, United Kingdom
| | - Gareth Gerrard
- Imperial Molecular Pathology, Imperial College Academic Health Sciences Centre, Hammersmith Campus, London W12 0NN, United Kingdom
| | - Vahid Asnafi
- Université Paris Descartes Sorbonne Cité, Institut Necker-Enfants Malades (INEM), Institut National de Recherche Médicale (INSERM), and Laboratory of Onco-Hematology, Assistance Publique-Hôpitaux de Paris (AP-HP), Hôpital Necker Enfants-Malades, Paris, France
| | - Elizabeth Macintyre
- Université Paris Descartes Sorbonne Cité, Institut Necker-Enfants Malades (INEM), Institut National de Recherche Médicale (INSERM), and Laboratory of Onco-Hematology, Assistance Publique-Hôpitaux de Paris (AP-HP), Hôpital Necker Enfants-Malades, Paris, France
| | - Matthias Merkenschlager
- Lymphocyte Development Group, MRC Clinical Sciences Centre, Imperial College Faculty of Medicine, Hammersmith Campus, London W12 0NN, United Kingdom
| | - Niall Dillon
- Gene Regulation and Chromatin Group, MRC Clinical Sciences Centre, Imperial College Faculty of Medicine, Hammersmith Campus, London W12 0NN, United Kingdom
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13
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Opportunities for therapeutic antibodies directed at G-protein-coupled receptors. Nat Rev Drug Discov 2017; 16:787-810. [PMID: 28706220 DOI: 10.1038/nrd.2017.91] [Citation(s) in RCA: 106] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
G-protein-coupled receptors (GPCRs) are activated by a diverse range of ligands, from large proteins and proteases to small peptides, metabolites, neurotransmitters and ions. They are expressed on all cells in the body and have key roles in physiology and homeostasis. As such, GPCRs are one of the most important target classes for therapeutic drug discovery. The development of drugs targeting GPCRs has therapeutic value across a wide range of diseases, including cancer, immune and inflammatory disorders as well as neurological and metabolic diseases. The progress made by targeting GPCRs with antibody-based therapeutics, as well as technical hurdles to overcome, are presented and discussed in this Review. Antibody therapeutics targeting C-C chemokine receptor type 4 (CCR4), CCR5 and calcitonin gene-related peptide (CGRP) are used as illustrative clinical case studies.
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G Protein-Coupled Receptors in Cancer. Int J Mol Sci 2016; 17:ijms17081320. [PMID: 27529230 PMCID: PMC5000717 DOI: 10.3390/ijms17081320] [Citation(s) in RCA: 141] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Revised: 07/21/2016] [Accepted: 08/08/2016] [Indexed: 12/12/2022] Open
Abstract
Despite the fact that G protein-coupled receptors (GPCRs) are the largest signal-conveying receptor family and mediate many physiological processes, their role in tumor biology is underappreciated. Numerous lines of evidence now associate GPCRs and their downstream signaling targets in cancer growth and development. Indeed, GPCRs control many features of tumorigenesis, including immune cell-mediated functions, proliferation, invasion and survival at the secondary site. Technological advances have further substantiated GPCR modifications in human tumors. Among these are point mutations, gene overexpression, GPCR silencing by promoter methylation and the number of gene copies. At this point, it is imperative to elucidate specific signaling pathways of “cancer driver” GPCRs. Emerging data on GPCR biology point to functional selectivity and “biased agonism”; hence, there is a diminishing enthusiasm for the concept of “one drug per GPCR target” and increasing interest in the identification of several drug options. Therefore, determining the appropriate context-dependent conformation of a functional GPCR as well as the contribution of GPCR alterations to cancer development remain significant challenges for the discovery of dominant cancer genes and the development of targeted therapeutics.
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15
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Ichijo Y, Mochimaru Y, Azuma M, Satou K, Negishi J, Nakakura T, Oshima N, Mogi C, Sato K, Matsuda K, Okajima F, Tomura H. Two zebrafish G2A homologs activate multiple intracellular signaling pathways in acidic environment. Biochem Biophys Res Commun 2015; 469:81-86. [PMID: 26614909 DOI: 10.1016/j.bbrc.2015.11.075] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2015] [Accepted: 11/17/2015] [Indexed: 01/01/2023]
Abstract
Human G2A is activated by various stimuli such as lysophosphatidylcholine (LPC), 9-hydroxyoctadecadienoic acid (9-HODE), and protons. The receptor is coupled to multiple intracellular signaling pathways, including the Gs-protein/cAMP/CRE, G12/13-protein/Rho/SRE, and Gq-protein/phospholipase C/NFAT pathways. In the present study, we examined whether zebrafish G2A homologs (zG2A-a and zG2A-b) could respond to these stimuli and activate multiple intracellular signaling pathways. We also examined whether histidine residue and basic amino acid residue in the N-terminus of the homologs also play roles similar to those played by human G2A residues if the homologs sense protons. We found that the zG2A-a showed the high CRE, SRE, and NFAT activities, however, zG2A-b showed only the high SRE activity under a pH of 8.0. Extracellular acidification from pH 7.4 to 6.3 ameliorated these activities in zG2A-a-expressing cells. On the other hand, acidification ameliorated the SRE activity but not the CRE and NFAT activities in zG2A-b-expressing cells. LPC or 9-HODE did not modify any activity of either homolog. The substitution of histidine residue at the 174(th) position from the N-terminus of zG2A-a to asparagine residue attenuated proton-induced CRE and NFAT activities but not SRE activity. The substitution of arginine residue at the 32nd position from the N-terminus of zG2A-a to the alanine residue also attenuated its high and the proton-induced CRE and NFAT activities. On the contrary, the substitution did not attenuate SRE activity. The substitution of the arginine residue at the 10th position from the N-terminus of zG2A-b to the alanine residue also did not attenuate its high or the proton-induced SRE activity. These results indicate that zebrafish G2A homologs were activated by protons but not by LPC and 9-HODE, and the activation mechanisms of the homologs were similar to those of human G2A.
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Affiliation(s)
- Yuta Ichijo
- Laboratory of Cell Signaling Regulation, Department of Life Sciences, School of Agriculture, Meiji University, Kawasaki 214-8571, Japan
| | - Yuta Mochimaru
- Laboratory of Cell Signaling Regulation, Department of Life Sciences, School of Agriculture, Meiji University, Kawasaki 214-8571, Japan
| | - Morio Azuma
- Laboratory of Regulatory Biology, Graduate School of Science and Engineering, University of Toyama, 3190-Gofuku, Toyama 930-8555, Japan
| | - Kazuhiro Satou
- Laboratory of Cell Signaling Regulation, Department of Life Sciences, School of Agriculture, Meiji University, Kawasaki 214-8571, Japan
| | - Jun Negishi
- Laboratory of Cell Signaling Regulation, Department of Life Sciences, School of Agriculture, Meiji University, Kawasaki 214-8571, Japan
| | - Takashi Nakakura
- Department of Anatomy, Graduate School of Medicine, Teikyo University, 2-11-1 Itabashi-Ku, Tokyo 173-8605, Japan
| | - Natsuki Oshima
- Laboratory of Cell Signaling Regulation, Department of Life Sciences, School of Agriculture, Meiji University, Kawasaki 214-8571, Japan
| | - Chihiro Mogi
- Laboratory of Signal Transduction, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi 371-8512, Japan
| | - Koichi Sato
- Laboratory of Signal Transduction, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi 371-8512, Japan
| | - Kouhei Matsuda
- Laboratory of Regulatory Biology, Graduate School of Science and Engineering, University of Toyama, 3190-Gofuku, Toyama 930-8555, Japan
| | - Fumikazu Okajima
- Laboratory of Signal Transduction, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi 371-8512, Japan
| | - Hideaki Tomura
- Laboratory of Cell Signaling Regulation, Department of Life Sciences, School of Agriculture, Meiji University, Kawasaki 214-8571, Japan.
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16
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Orgaz JL, Herraiz C, Sanz-Moreno V. Rho GTPases modulate malignant transformation of tumor cells. Small GTPases 2014; 5:e29019. [PMID: 25036871 DOI: 10.4161/sgtp.29019] [Citation(s) in RCA: 117] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Rho GTPases are involved in the acquisition of all the hallmarks of cancer, which comprise 6 biological capabilities acquired during the development of human tumors. The hallmarks include proliferative signaling, evading growth suppressors, resisting cell death, enabling replicative immortality, inducing angiogenesis, and activating invasion and metastasis programs, as defined by Hanahan and Weinberg. (1) Controlling these hallmarks are genome instability and inflammation. Emerging hallmarks are reprogramming of energy metabolism and evading immune destruction. To give a different view to the readers, we will not be focusing on invasion, metastasis, or cytoskeletal remodeling, but we will review here how Rho GTPases contribute to other hallmarks of cancer with a special emphasis on malignant transformation.
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Affiliation(s)
- Jose L Orgaz
- Randall Division of Cell and Molecular Biophysics; New Hunt's House; Guy's Campus; King's College London; London, UK
| | - Cecilia Herraiz
- Randall Division of Cell and Molecular Biophysics; New Hunt's House; Guy's Campus; King's College London; London, UK
| | - Victoria Sanz-Moreno
- Randall Division of Cell and Molecular Biophysics; New Hunt's House; Guy's Campus; King's College London; London, UK
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17
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Justus CR, Dong L, Yang LV. Acidic tumor microenvironment and pH-sensing G protein-coupled receptors. Front Physiol 2013; 4:354. [PMID: 24367336 PMCID: PMC3851830 DOI: 10.3389/fphys.2013.00354] [Citation(s) in RCA: 231] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Accepted: 11/19/2013] [Indexed: 01/02/2023] Open
Abstract
The tumor microenvironment is acidic due to glycolytic cancer cell metabolism, hypoxia, and deficient blood perfusion. It is proposed that acidosis in the tumor microenvironment is an important stress factor and selection force for cancer cell somatic evolution. Acidic pH has pleiotropic effects on the proliferation, migration, invasion, metastasis, and therapeutic response of cancer cells and the function of immune cells, vascular cells, and other stromal cells. However, the molecular mechanisms by which cancer cells and stromal cells sense and respond to acidic pH in the tumor microenvironment are poorly understood. In this article the role of a family of pH-sensing G protein-coupled receptors (GPCRs) in tumor biology is reviewed. Recent studies show that the pH-sensing GPCRs, including GPR4, GPR65 (TDAG8), GPR68 (OGR1), and GPR132 (G2A), regulate cancer cell metastasis and proliferation, immune cell function, inflammation, and blood vessel formation. Activation of the proton-sensing GPCRs by acidosis transduces multiple downstream G protein signaling pathways. Since GPCRs are major drug targets, small molecule modulators of the pH-sensing GPCRs are being actively developed and evaluated. Research on the pH-sensing GPCRs will continue to provide important insights into the molecular interaction between tumor and its acidic microenvironment and may identify new targets for cancer therapy and chemoprevention.
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Affiliation(s)
- Calvin R Justus
- Department of Oncology, Brody School of Medicine, East Carolina University Greenville, NC, USA
| | - Lixue Dong
- Department of Oncology, Brody School of Medicine, East Carolina University Greenville, NC, USA
| | - Li V Yang
- Department of Oncology, Brody School of Medicine, East Carolina University Greenville, NC, USA ; Department of Internal Medicine, Brody School of Medicine, East Carolina University Greenville, NC, USA ; Department of Anatomy and Cell Biology, Brody School of Medicine, East Carolina University Greenville, NC, USA
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18
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Rolin J, Al-Jaderi Z, Maghazachi AA. Oxidized lipids and lysophosphatidylcholine induce the chemotaxis and intracellular calcium influx in natural killer cells. Immunobiology 2012. [PMID: 23200035 DOI: 10.1016/j.imbio.2012.10.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
We previously reported that human NK cells express G2A and they respond to LPC. Here, we report that oxidized lipids such as 9-R-HODE, 9-S-HODE and 13-R-HODE, as well as LPC induced the in vitro chemotaxis of human NK cells, although with variable efficacies. The chemotactic effects of these lipids were inhibited by prior treatment of NK cells with pertussis toxin (PTX). 9-S-HODE, 9-R-HODE and LPC optimally induced the influx of intracellular Ca(2+) in NK cells. Addition of 9-S-HODE prior to the addition of LPC inhibited more than 50% of the effect of LPC, whereas addition of LPC prior to the addition of 9-S-HODE completely inhibited the effect of the latter lipid. Also, there was a complete reciprocal desensitization among 9-R-HODE and LPC on the influx of intracellular Ca(2+). Further analysis showed that the four lipids did not affect NK cell lysis of tumor target cells. 9-R-HODE but not any other lipid increased the percentages of NK cells producing IFN-γ and is the only lipid that enhanced the release of this cytokine by these cells. In conclusion, we provide novel evidence showing that oxidized lipids and LPC exert important functions for cells of innate immune system.
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Affiliation(s)
- Johannes Rolin
- Department of Physiology, Institute of Basic Medical Science, Faculty of Medicine, University of Oslo, Norway
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19
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Singh A, Boyer JL, Der CJ, Zohn IE. Transformation by a nucleotide-activated P2Y receptor is mediated by activation of Galphai, Galphaq and Rho-dependent signaling pathways. J Mol Signal 2010; 5:11. [PMID: 20653955 PMCID: PMC2917412 DOI: 10.1186/1750-2187-5-11] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2010] [Accepted: 07/23/2010] [Indexed: 11/14/2022] Open
Abstract
Background Nucleotide-actived P2Y receptors play critical roles in the growth of tumor cells by regulating cellular proliferation, differentiation and survival. Results Here we demonstrate that an avian P2Y purinoceptor (tP2YR) with unique pharmacological and signal transduction properties induces morphologic and growth transformation of rodent fibroblasts. tP2YR induced a transformed phenotype similar to the mas oncogene, a G protein-coupled receptor which causes transformation by activation of Rac-dependent pathways. tP2YR-transformed cells exhibited increased steady-state activation of Rac1 and RhoA. Like activated Rho GTPases, tP2YR cooperated with activated Raf and caused synergistic transformation of NIH3T3 cells. Our data indicate that the ability of tP2YR to cause transformation is due to its unique ability among purinergic receptors to simultaneously activate Gαq and Gαi. Co-expression of constitutively activated mutants of these two Gα subunits caused the same transformed phenotype as tP2YR and Mas. Furthermore, transformation by both tP2YR and Mas was blocked by pharmacological inhibition of GαI by pertussis toxin (PTX) indicating an essential role for Gαi in transformation by these G-protein coupled receptors. Conclusions Our data suggest that coordinated activation of Gαq and Gαi may link the tP2YR and possibility the Mas oncogene with signaling pathways resulting in activation of Rho family proteins to promote cellular transformation.
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Affiliation(s)
- Anurag Singh
- Linebergher Comprehensive Cancer Center, University of North Carolina at Chapel Hill, NC 27599, USA.
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20
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Murakami N, Hashidate T, Harayama T, Yokomizo T, Shimizu T, Nakamura M. Transcriptional regulation of human G2A in monocytes/ macrophages: involvement of c/EBPs, Runx and Pu.1. Genes Cells 2009; 14:1441-55. [DOI: 10.1111/j.1365-2443.2009.01360.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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21
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Bercher M, Hanson B, van Staden C, Wu K, Ng GY, Lee PH. Agonists of the orphan human G2A receptor identified from inducible G2A expression and beta-lactamase reporter screen. Assay Drug Dev Technol 2009; 7:133-42. [PMID: 19505230 DOI: 10.1089/adt.2008.179] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The G protein-coupled receptor (GPCR) G2A (for G2 accumulation) was identified as a stress-inducible antiproliferative cell cycle regulator. Targeted G2A gene deletion in mice resulted in systemic lupus erythematosus-like and atherosclerotic lesion phenotypes. These findings suggested that G2A may be a therapeutic target for cancers and autoimmune and cardiovascular diseases. The G2A receptor is cytotoxic upon ectopic expression, and its cognate ligand has not been identified, making it difficult to generate a cell line for screening using a conventional approach. The function of human G2A remains obscure. Here we show that by using an inducible T-REx (Invitrogen, Carlsbad, CA) expression system an inducible G2A functional cell-based beta-lactamase reporter assay could be developed using the constitutive activity of the receptor. Furthermore, G2A expression levels can be controlled under this inducible system to avoid the expression artifacts of conventional approaches using constitutive expression vectors. This stable cell line expressing the human G2A receptor was screened against a chemical library containing 740,000 compounds, and small molecules showing selective agonistic activity on G2A were identified. We believe the strategy employed here for G2A should be applicable to other "intractable" GPCRs where target gene expression results in cytotoxic and/or high constitutive activities.
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Affiliation(s)
- Mark Bercher
- Invitrogen Discovery Sciences, Madison, Wisconsin, USA
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22
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Kabarowski JH. G2A and LPC: regulatory functions in immunity. Prostaglandins Other Lipid Mediat 2009; 89:73-81. [PMID: 19383550 DOI: 10.1016/j.prostaglandins.2009.04.007] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2009] [Revised: 04/10/2009] [Accepted: 04/13/2009] [Indexed: 02/07/2023]
Abstract
The G2A receptor was originally identified by virtue of its transcriptional induction in murine B lymphoid cells in response to oncogenic transformation and treatment with various DNA-damaging agents. While preliminary characterization of cellular responses to G2A overexpression in fibroblastic cell lines suggested that this receptor may negatively regulate cell growth under conditions of proliferative and genotoxic stress, subsequent studies driven by the discovery of lysophosphatidylcholine (LPC) as a regulator of G2A signaling in immunoregulatory cells point to an important role for this receptor in innate and adaptive immunity.
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Affiliation(s)
- Janusz H Kabarowski
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294-2170, USA.
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23
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Tobo M, Tomura H, Mogi C, Wang JQ, Liu JP, Komachi M, Damirin A, Kimura T, Murata N, Kurose H, Sato K, Okajima F. Previously postulated "ligand-independent" signaling of GPR4 is mediated through proton-sensing mechanisms. Cell Signal 2007; 19:1745-53. [PMID: 17462861 DOI: 10.1016/j.cellsig.2007.03.009] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2007] [Accepted: 03/21/2007] [Indexed: 12/25/2022]
Abstract
GPR4 was initially identified as a receptor for sphingosylphosphorylcholine and lysophosphatidylcholine; however, lipid actions have not always been confirmed. Instead, ligand-independent actions have sometimes been observed in GPR4- and other OGR1 family receptor-expressing cells. Here, we examined the possible involvement of extracellular protons, which have recently been proposed as another ligand for GPR4. At pH 7.4, the epidermal growth factor-induced extracellular signal-regulated kinase activity was lower in GPR4-transfected RH7777 cells, in association with increased cAMP accumulation, than in vector-transfected cells. The serum response element (SRE)-driven transcriptional activity was also clearly higher in GPR4-expressing HEK293 cells than in vector-transfected cells at pH 7.4. These apparent ligand-independent actions were very small at alkalinic 7.8. The SRE activity was further increased by extracellular acidification in a manner dependent on the G13 protein/Rho signaling pathway in HEK293 cells expressing GPR4 or other OGR1 receptor family members. GPR4-expressing cells also showed a calcineurin-dependent nuclear factor of activated T cell (NFAT) promoter activation at pH 7.4, and this activity was further increased by pH below 7.2 in association with inositol phosphate production. In contrast to the cAMP and SRE responses, however, alkalinization to pH 7.8 hardly affected the high basal activity. Finally, the expression of GPR4 hardly modulated the sphingosylphosphorylcholine- or lysophosphatidylcholine-induced action. These results suggest that an extracellular proton play a role as a ligand in some of previously postulated ligand-independent actions through GPR4 receptors. Moreover, GPR4 may be a multi-functional receptor coupling to Gs, G13, and Gq/11 proteins in response to extracellular acidification.
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Affiliation(s)
- Masayuki Tobo
- Laboratory of Signal Transduction, Institute for Molecular and Cellular Regulation, Gunma University, 3-39-15 Showa-machi, Maebashi 371-8512, Japan
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24
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Yin YJ, Katz V, Salah Z, Maoz M, Cohen I, Uziely B, Turm H, Grisaru-Granovsky S, Suzuki H, Bar-Shavit R. Mammary gland tissue targeted overexpression of human protease-activated receptor 1 reveals a novel link to beta-catenin stabilization. Cancer Res 2006; 66:5224-33. [PMID: 16707447 DOI: 10.1158/0008-5472.can-05-4234] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Protease-activated receptor 1 (PAR1) is emerging with distinct assignments in tumor biology. We show that tissue targeted overexpression of hPar1 in mice mammary glands results in precocious hyperplasia, characterized by a dense network of ductal side branching and accelerated proliferation. These glands exhibit increased levels of wnt-4 and wnt-7b and a striking beta-catenin stabilization. Nuclear localization of beta-catenin is observed in hPar1 transgenic mouse tissue sections but not in the wild-type, age-matched counterparts. PAR1 induces beta-catenin nuclear localization also in established epithelial tumor cell lines of intact beta-catenin system (transformed on the background of mismatch repair system; RKO cells). We propose hereby that PAR1-mediated beta-catenin stabilization is taking place primarily via the increase of Wnt expression. Enforced expression of a specific Wnt antagonist family member, secreted frizzled receptor protein 5 (SFRP5), efficiently inhibited PAR1-induced beta-catenin stabilization. Likewise, application of either SFRP2 or SFRP5 on epithelial tumor cells completely abrogated PAR1-induced beta-catenin nuclear accumulation. This takes place most likely via inhibition of Wnt signaling at the level of cell surface (forming a neutralizing complex of "Receptors-SFRP-Wnt"). Furthermore, depletion of hPar1 by small interfering RNA (siRNA) vectors markedly inhibited PAR1-induced Wnt-4. The striking stabilization of beta-catenin, inhibited by SFRPs on one hand and Wnt-4 silencing by hPar1 siRNA on the other hand, points to a novel role of hPar1 in Wnt-mediated beta-catenin stabilization. This link between PAR1 and beta-catenin may bear substantial implications both in developmental and tumor progression processes.
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Affiliation(s)
- Yong-Jun Yin
- Department of Oncology, Hadassah-Hebrew University Hospital, Jerusalem, Israel
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25
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Tomura H, Mogi C, Sato K, Okajima F. Proton-sensing and lysolipid-sensitive G-protein-coupled receptors: A novel type of multi-functional receptors. Cell Signal 2005; 17:1466-76. [PMID: 16014326 DOI: 10.1016/j.cellsig.2005.06.002] [Citation(s) in RCA: 132] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2005] [Accepted: 06/03/2005] [Indexed: 11/16/2022]
Abstract
OGR1, GPR4, G2A, and TDAG8 share 40% to 50% homology with each other and seem to form a family of GPCRs. They have been described as receptors for lipid molecules such as sphingosylphosphorylcholine, lysophosphatidylcholine, and psychosine. Recent studies, however, have revealed that these receptors also sense extracellular protons or pH through histidine residues of receptors and stimulate a variety of intracellular signaling pathways through several species of hetero-trimeric G-proteins, including G(s), G(i), G(q), and G(12/13). Thus, this family of GPCR seems to recognize both lipid molecules and protons as ligands. Although our knowledge of proton-sensing and lysolipid-sensitive GPCRs is preliminary, the receptor levels and ligand levels especially protons are both sensitively modulated in response to a variety of microenvironmental changes. These results suggest a multiple role of proton-sensing GPCRs in a variety of physiological and pathophysiological states.
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Affiliation(s)
- Hideaki Tomura
- Laboratory of Signal Transduction, Institute for Molecular and Cellular Regulation, Gunma University, 3-39-15 Showa-machi, Maebashi 371-8512, Japan
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26
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Abstract
Recently, two different chemicals have been matched as ligands with the same G-protein-coupled receptor (GPCR). Double-pairing of OGR1 family GPCRs with proton and lysolipid raises several questions. First, whether both are the real ligands for the GPCRs. Second, whether modulation of a GPCR by two chemicals could be possible. Third, one of the chemicals is proton. Proton-sensing not only is a new action mode of GPCR activation, but also it could be generalized in other GPCRs. In this review, I would like to summarize the issue and discuss questions with pharmacological criteria.
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Affiliation(s)
- Dong-Soon Im
- Laboratory of Pharmacology and Research Institute of Drug Development, College of Pharmacy, Pusan National University, Busan 609-735, Republic of Korea.
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27
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Riobo NA, Manning DR. Receptors coupled to heterotrimeric G proteins of the G12 family. Trends Pharmacol Sci 2005; 26:146-54. [PMID: 15749160 DOI: 10.1016/j.tips.2005.01.007] [Citation(s) in RCA: 126] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Much regarding the engagement of the G(12) family of heterotrimeric G proteins (G(12) and G(13)) by agonist-activated receptors remains unclear. For example, the identity of receptors that couple unequivocally to G(12) and G(13) and how signals are allocated among these and other G proteins remain open questions. Part of the problem in understanding signaling through G(12) and G(13) is that the activation of these G proteins is rarely demonstrated directly and is instead presumed usually from far removed downstream events. Furthermore, receptors that couple to G(12) and G(13) invariably couple to additional G proteins, and thus few events can be linked unambiguously to one G protein or another. In this article, we document receptors that reportedly couple to G(12), G(13) or both G(12) and G(13), evaluate the methodology used to understand the coupling of these receptors, and discuss the ability of these receptors to couple also to G(q).
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Affiliation(s)
- Natalia A Riobo
- Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6084, USA
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28
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Parks BW, Gambill GP, Lusis AJ, Kabarowski JHS. Loss of G2A promotes macrophage accumulation in atherosclerotic lesions of low density lipoprotein receptor-deficient mice. J Lipid Res 2005; 46:1405-15. [PMID: 15834123 DOI: 10.1194/jlr.m500085-jlr200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Lysophosphatidylcholine (LPC) is considered a major proatherogenic component of oxidized low density lipoprotein based on its proinflammatory actions in vitro. LPC stimulates macrophage and T-cell chemotaxis via the G protein-coupled receptor G2A and may thus promote inflammatory cell infiltration during atherosclerotic lesion development. However, G2A also mediates proapoptotic effects of LPC and may therefore promote the death of inflammatory cells within developing lesions. To determine how these effects of LPC modify atherogenesis, we examined atherosclerotic lesion development in G2A-sufficient and G2A-deficient low density lipoprotein receptor knockout mice. Although LPC species capable of activating G2A-dependent responses were increased during lesion development, G2A-deficient mice developed lesions similar in size to those in their G2A-sufficient counterparts. Loss of G2A during atherosclerotic lesion development did not reduce macrophage and T-cell infiltration but instead resulted in increased lesional macrophage content associated with reduced numbers of terminal deoxynucleotidyl transferase-mediated dUTP nick end labeled cells and decreased collagen deposition. These data indicate that the ability of LPC to stimulate macrophage and T-cell chemotaxis via G2A is not manifested in vivo and that G2A-mediated proapoptotic rather than chemotactic action is most penetrant during atherogenesis and may modify the stability of atherosclerotic lesions by promoting macrophage death.
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Affiliation(s)
- Brian W Parks
- Department of Microbiology, University of Alabama, Birmingham, AL 35294-2170, USA
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29
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Abstract
Heterotrimeric G-proteins are intracellular partners of G-protein-coupled receptors (GPCRs). GPCRs act on inactive Galpha.GDP/Gbetagamma heterotrimers to promote GDP release and GTP binding, resulting in liberation of Galpha from Gbetagamma. Galpha.GTP and Gbetagamma target effectors including adenylyl cyclases, phospholipases and ion channels. Signaling is terminated by intrinsic GTPase activity of Galpha and heterotrimer reformation - a cycle accelerated by 'regulators of G-protein signaling' (RGS proteins). Recent studies have identified several unconventional G-protein signaling pathways that diverge from this standard model. Whereas phospholipase C (PLC) beta is activated by Galpha(q) and Gbetagamma, novel PLC isoforms are regulated by both heterotrimeric and Ras-superfamily G-proteins. An Arabidopsis protein has been discovered containing both GPCR and RGS domains within the same protein. Most surprisingly, a receptor-independent Galpha nucleotide cycle that regulates cell division has been delineated in both Caenorhabditis elegans and Drosophila melanogaster. Here, we revisit classical heterotrimeric G-protein signaling and explore these new, non-canonical G-protein signaling pathways.
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Affiliation(s)
- C R McCudden
- Department of Pharmacology, Lineberger Comprehensive Cancer Center, and UNC Neuroscience Center, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, 27599-7365, USA.
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30
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Wang L, Radu CG, Yang LV, Bentolila LA, Riedinger M, Witte ON. Lysophosphatidylcholine-induced surface redistribution regulates signaling of the murine G protein-coupled receptor G2A. Mol Biol Cell 2005; 16:2234-47. [PMID: 15728718 PMCID: PMC1087231 DOI: 10.1091/mbc.e04-12-1044] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Intracellular trafficking and spatial dynamics of membrane receptors critically regulate receptor function. Using microscopic and subcellular fractionation analysis, we studied the localization of the murine G protein-coupled receptor G2A (muG2A). Evaluating green fluorescent protein-tagged, exogenously expressed as well as the endogenous muG2A, we observed that this receptor was spontaneously internalized and accumulated in endosomal compartments, whereas its surface expression was enhanced and stabilized by lysophosphatidylcholine (LPC) treatment. Monensin, a general inhibitor of recycling pathways, blocked LPC-regulated surface localization of muG2A as well as muG2A-dependent extracellular signal-regulated kinase (ERK) activation and cell migration induced by LPC treatment. Mutation of the conserved DRY motif (R-->A) enhanced the surface expression of muG2A, resulting in its resistance to monensin inhibition of ERK activation. Our data suggest that intracellular sequestration and surface expression regulated by LPC, rather than direct agonistic activity control the signaling responses of murine G2A toward LPC.
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Affiliation(s)
- Li Wang
- Department of Microbiology, Immunology, and Molecular Genetics, UCLA, Los Angeles, CA 90095, USA
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31
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Radu CG, Nijagal A, McLaughlin J, Wang L, Witte ON. Differential proton sensitivity of related G protein-coupled receptors T cell death-associated gene 8 and G2A expressed in immune cells. Proc Natl Acad Sci U S A 2005; 102:1632-7. [PMID: 15665078 PMCID: PMC545089 DOI: 10.1073/pnas.0409415102] [Citation(s) in RCA: 165] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
G2A, T cell death-associated gene 8 (TDAG8), ovarian cancer G protein-coupled receptor 1 (OGR1), and G protein-coupled receptor 4 (GPR4) form a group of structurally related G protein-coupled receptors (GPCRs) originally proposed to bind proinflammatory lipids. More recent studies have challenged the identification of lipid agonists for these GPCRs and have suggested that they function primarily as proton sensors. We compared the ability of these four receptors to modulate pH-dependent responses by using transiently transfected cell lines. In accordance with previously published reports, OGR1 was found to evoke strong pH-dependent responses as measured by inositol phosphate accumulation. We also confirmed the pH-dependent cAMP production by GPR4 and TDAG8. However, we found the activity of the human G2A receptor and its mouse homolog to be significantly less sensitive to pH fluctuations as measured by inositol phosphate and cAMP accumulation. Sequence homology analysis indicated that, with one exception, the histidine residues that were previously shown to be important for pH sensing by OGR1, GPR4, and TDAG8 were not conserved in the G2A receptor. We further addressed the pH-sensing properties of G2A and TDAG8 in a cellular context where these receptors are coexpressed. In thymocytes and splenocytes explanted from receptor-deficient mice, TDAG8 was found to be critical for pH-dependent cAMP production. In contrast, G2A was found to be dispensable for this process. We conclude that members of this GPCR group exhibit differential sensitivity to extracellular protons, and that expression of TDAG8 by immune cells may regulate responses in acidic microenvironments.
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Affiliation(s)
- Caius G Radu
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, CA 90095, USA
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32
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Abstract
Lysophospholipids (LPs), such as lysophosphatidic acid and sphingosine 1-phosphate, are membrane-derived bioactive lipid mediators. LPs can affect fundamental cellular functions, which include proliferation, differentiation, survival, migration, adhesion, invasion, and morphogenesis. These functions influence many biological processes that include neurogenesis, angiogenesis, wound healing, immunity, and carcinogenesis. In recent years, identification of multiple cognate G protein-coupled receptors has provided a mechanistic framework for understanding how LPs play such diverse roles. Generation of LP receptor-null animals has allowed rigorous examination of receptor-mediated physiological functions in vivo and has identified new functions for LP receptor signaling. Efforts to develop LP receptor subtype-specific agonists/antagonists are in progress and raise expectations for a growing collection of chemical tools and potential therapeutic compounds. The rapidly expanding literature on the LP receptors is herein reviewed.
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Affiliation(s)
- Isao Ishii
- Department of Molecular Genetics, National Institute of Neuroscience, NCNP, Kodaira, Tokyo 187-8502, Japan.
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33
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Murakami N, Yokomizo T, Okuno T, Shimizu T. G2A is a proton-sensing G-protein-coupled receptor antagonized by lysophosphatidylcholine. J Biol Chem 2004; 279:42484-91. [PMID: 15280385 DOI: 10.1074/jbc.m406561200] [Citation(s) in RCA: 187] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
G2A (from G2 accumulation) is a G-protein-coupled receptor (GPCR) that regulates the cell cycle, proliferation, oncogenesis, and immunity. G2A shares significant homology with three GPCRs including ovarian cancer GPCR (OGR1/GPR68), GPR4, and T cell death-associated gene 8 (TDAG8). Lysophosphatidylcholine (LPC) and sphingosylphosphorylcholine (SPC) were reported as ligands for G2A and GPR4 and for OGR1 (SPC only), and a glycosphingolipid psychosine was reported as ligand for TDAG8. As OGR1 and GPR4 were reported as proton-sensing GPCRs (Ludwig, M. G., Vanek, M., Guerini, D., Gasser, J. A., Jones, C. E., Junker, U., Hofstetter, H., Wolf, R. M., and Seuwen, K. (2003) Nature 425, 93-98), we evaluated the proton-sensing function of G2A. Transient expression of G2A caused significant activation of the zif 268 promoter and inositol phosphate (IP) accumulation at pH 7.6, and lowering extracellular pH augmented the activation only in G2A-expressing cells. LPC inhibited the pH-dependent activation of G2A in a dose-dependent manner in these assays. Thus, G2A is another proton-sensing GPCR, and LPC functions as an antagonist, not as an agonist, and regulates the proton-dependent activation of G2A.
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Affiliation(s)
- Naoka Murakami
- Department of Biochemistry, Faculty of Medicine, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan
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34
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Sin WC, Zhang Y, Zhong W, Adhikarakunnathu S, Powers S, Hoey T, An S, Yang J. G protein-coupled receptors GPR4 and TDAG8 are oncogenic and overexpressed in human cancers. Oncogene 2004; 23:6299-303. [PMID: 15221007 DOI: 10.1038/sj.onc.1207838] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The GPR4 subfamily consists of four G protein-coupled receptors that share significant sequence homology. In addition to GPR4, this subfamily includes OGR1, TDAG8 and G2A. G2A has previously been shown to be a potent transforming oncogene for murine 3T3 cells. Here we show that GPR4 also malignantly transforms NIH3T3 cells and that TDAG8 malignantly transforms the normal mammary epithelial cell line NMuMG. Overexpression of GPR4 or TDAG8 in HEK293 cells led to transcriptional activation from SRE- and CRE-driven promoters, independent of exogenously added ligand. TDAG8 and GPR4 are also overexpressed in a range of human cancer tissues. Our results suggest that GPR4 and TDAG8 overexpression in human tumors plays a role in driving or maintaining tumor formation.
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Affiliation(s)
- Wun Chey Sin
- Genomics Division, Tularik Inc., 266 East Pulaski Rd, Greenlawn, NY 11740, USA
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35
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Han KH, Hong KH, Ko J, Rhee KS, Hong MK, Kim JJ, Kim YH, Park SJ. Lysophosphatidylcholine up-regulates CXCR4 chemokine receptor expression in human CD4 T cells. J Leukoc Biol 2004; 76:195-202. [PMID: 15178707 DOI: 10.1189/jlb.1103563] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Oxidized low-density lipoprotein (OxLDL) is an inflammatory modulator in the atherosclerotic plaque. We examined the effect of lysophosphatidylcholine (lysoPC), a main phospholipid component of OxLDL, on inflammatory responses in human CD4 T cells. We found that lysoPC dose- and time-dependently increased expression of CXCR4, the chemokine receptor on CD4 T cells. This increase was inhibited by caffeic acid phenethyl ester or SN50, nuclear factor-kappaB inhibitors, and also by suppression of G2A expression, the specific receptor for lysoPC, using antisense oligonucleotide. lysoPC enhanced CD4 T cell chemotaxis in response to stromal cell-derived factor-1 (SDF-1), the exclusive ligand for CXCR4. lysoPC also enhanced SDF-1-stimulated production of inflammatory cytokines interleukin-2 and interferon-gamma by CD4 T cells activated by anti-CD3 immunoglobulin G. In conclusion, this study demonstrates that lysoPC directly modulates inflammatory responses in human CD4 T cells. The data suggest that the presence of lysoPC and SDF-1 in atherosclerotic lesions may trigger inflammatory responses mediated by CD4 T cells, which may play an important role in progression of atherosclerosis.
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Affiliation(s)
- Ki Hoon Han
- College of Medicine, Asan Medical Center, 388-1 Pungnap-2 dong, Songpa-gu 138-736, Seoul, South Korea
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36
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Kostenis E. A glance at G-protein-coupled receptors for lipid mediators: a growing receptor family with remarkably diverse ligands. Pharmacol Ther 2004; 102:243-57. [PMID: 15246248 DOI: 10.1016/j.pharmthera.2004.04.005] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
A plethora of lipid-like molecules known to act as intracellular second messengers are now recognized to signal cells through plasma membrane 7 transmembrane G-protein-coupled receptors (GPCRs). This has been the result of a decade-long genetic hunt for novel sequences encoding 7 transmembrane receptor proteins and the efforts to pair novel sequences with biologically active substances of (partly) unknown molecular mechanism of action. Identification of novel GPCR ligand pairs represents the first step to shed more light into the mode of action of novel cellular signaling molecules in human health and disease and might represent a fruitful source for the development of new drugs, judged on the successful history of GPCR as drug targets. Since 2000, more than 16 reports became available on lipid mediators--as diverse as lysophospholipids, arachidonic acid metabolites, short-, medium-, and long-chain fatty acids as well as steroid-like molecules--exerting their effects as extracellular mediators via rhodopsin-like family GPCRs. These reports have opened new avenues for research in human lipid receptor physiology and pharmacology. Here, the current knowledge on the recently deorphanized lipid receptors, including their isolation, expression pattern, function, and possible physiological or pathological roles will be reviewed.
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Affiliation(s)
- Evi Kostenis
- 7TM Pharma A/S, 3 Fremtidsvej, 2970 Hoersholm, Denmark.
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37
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Radu CG, Yang LV, Riedinger M, Au M, Witte ON. T cell chemotaxis to lysophosphatidylcholine through the G2A receptor. Proc Natl Acad Sci U S A 2003; 101:245-50. [PMID: 14681556 PMCID: PMC314170 DOI: 10.1073/pnas.2536801100] [Citation(s) in RCA: 156] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
G2A is an immunoregulatory G protein-coupled receptor predominantly expressed in lymphocytes and macrophages. Ectopic overexpression studies have implicated G2A as a receptor for the bioactive lysophospholipid, lysophosphatidylcholine (LPC). However, the functional consequences of LPC-G2A interaction at physiological levels of receptor expression, and in a cellular context relevant to its immunological role, remain largely unknown. Here, we show impaired chemotaxis to LPC of a T lymphoid cell line in which G2A expression was chronically down-regulated by RNA interference technology. Rescuing this phenotype by reconstitution of the physiological level of receptor expression further supports a functional connection between LPC-G2A interaction and cellular motility. Overexpression of G2A in the T lymphoid cell line significantly enhanced chemotaxis to LPC. It also modified migration toward the LPC-related molecule, lysophosphatidic acid, indicating the possibility of crosstalk between G2A and endogenous lysophosphatidic acid receptors. The role of G2A in LPC-mediated cell migration may be relevant to the autoimmune syndrome associated with genetic inactivation of this G protein-coupled receptor in mice. The experimental system described here can be useful for understanding the structural requirements for LPC recognition by G2A and the signaling pathways regulated by this ligand-receptor pair.
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Affiliation(s)
- Caius G Radu
- Department of Microbiology, Howard Hughes Medical Institute, University of California, Los Angeles, CA 90095, USA
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Wing MR, Snyder JT, Sondek J, Harden TK. Direct activation of phospholipase C-epsilon by Rho. J Biol Chem 2003; 278:41253-8. [PMID: 12900402 DOI: 10.1074/jbc.m306904200] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Unique among the phospholipase C isozymes, the recently identified phospholipase C-epsilon (PLC-epsilon) contains an amino-terminal CDC25 domain capable of catalyzing nucleotide exchange on Ras family GTPases as well as a tandem array of Ras-associating (RA) domains near its carboxyl terminus that are effector binding sites for activated H-Ras and Rap. To determine whether other small GTPases activate PLC-epsilon, we measured inositol phosphate accumulation in COS-7 cells expressing a broad range of GTPase-deficient mutants of Ras superfamily proteins. RhoA, RhoB, and RhoC all markedly stimulated inositol phosphate accumulation in PLC-epsilon-expressing cells. This stimulation matched or exceeded phospholipase activation promoted by co-expression of PLC-epsilon with the known regulators Ras, Galpha12/13, or Gbeta1gamma2. In contrast, little effect was observed with the other Rho family members Rac1, Rac2, Rac3, and Cdc42. Truncation of the two carboxyl-terminal RA domains caused loss of responsiveness to H-Ras but not to Rho. Truncation of PLC-epsilon to remove the CDC25 and pleckstrin homology (PH) domains also did not cause loss of responsiveness to Rho, Galpha12/13, or Gbeta1gamma2. Comparative sequence analysis of mammalian phospholipase C isozymes revealed a unique approximately 65 amino acid insert within the catalytic core of PLC-epsilon not present in PLC-beta, gamma, delta, or zeta. A PLC-epsilon construct lacking this region was no longer activated by Rho or Galpha12/13 but retained regulation by Gbetagamma and H-Ras. GTP-dependent interaction of Rho with PLC-epsilon was illustrated in pull-down experiments with GST-Rho, and this interaction was retained in the PLC-epsilon construct lacking the unique insert within the catalytic core. These results are consistent with the conclusion that Rho family GTPases directly interact with PLC-epsilon by a mechanism independent of the CDC25 or RA domains. A unique insert within the catalytic core of PLC-epsilon imparts responsiveness to Rho, which may signal downstream of Galpha12/13 in the regulation of PLC-epsilon, because activation by both Rho and Galpha12/13 is lost in the absence of this sequence.
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Affiliation(s)
- Michele R Wing
- Department of Pharmacology, the Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599, USA
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Iwahara T, Akagi T, Shishido T, Hanafusa H. CrkII induces serum response factor activation and cellular transformation through its function in Rho activation. Oncogene 2003; 22:5946-57. [PMID: 12955073 DOI: 10.1038/sj.onc.1206633] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
CrkII belongs to the adaptor protein family that plays a crucial role in signal transduction. In order to better understand the biological functions of CrkII, we focused on the regulation of gene expression by CrkII. Various transcriptional control elements were examined for their activation by CrkII-expression, and we found that CrkII selectively activates the serum response element (SRE), a transcriptional control element of immediate-early genes. This SRE activation induced by CrkII-overexpression was mediated by the serum response factor (SRF) via Rho. Indeed, we confirmed that the amount of activated Rho was increased in the CrkII-expressing cells. Moreover, we showed that when overexpressed, CrkII induces the cellular transformation of NIH 3T3 cells and that a dominant negative mutant of Rho suppresses this transformation, strongly suggesting that activation of Rho is essential for the transforming activity by CrkII. Furthermore, we also found that CrkII and Galpha12, a member of the heterotrimeric G proteins, synergistically activates Rho as well as the SRF, and that an SH3 mutant of CrkII can inhibit the Galpha12-induced activation of SRF. These results strongly suggest that CrkII is involved in the activation of Rho and SRF by Galpha12. Our study provides strong evidence that Rho activation plays a crucial role in CrkII-mediated signals to induce gene expression and cellular transformation.
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Affiliation(s)
- Toshinori Iwahara
- Laboratory of Molecular Oncology, Osaka Bioscience Institute, 6-2-4 Furuedai, Suita, Osaka 565-0874, Japan
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Scott G, Leopardi S, Parker L, Babiarz L, Seiberg M, Han R. The proteinase-activated receptor-2 mediates phagocytosis in a Rho-dependent manner in human keratinocytes. J Invest Dermatol 2003; 121:529-41. [PMID: 12925212 DOI: 10.1046/j.1523-1747.2003.12427.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Recent work shows that the G-protein-coupled receptor proteinase activated receptor-2 activates signals that stimulate melanosome uptake in keratinocytes in vivo and in vitro. The Rho family of GTP-binding proteins is involved in cytoskeletal remodeling during phagocytosis. We show that proteinase-activated receptor-2 mediated phagocytosis in human keratinocytes is Rho dependent and that proteinase-activated receptor-2 signals to activate Rho. In contrast, Rho activity did not affect either proteinase-activated receptor-2 activity or mRNA and protein levels. We explored the signaling mechanisms of proteinase-activated receptor-2 mediated Rho activation in human keratinocytes and show that activation of proteinase-activated receptor-2, either through specific proteinase-activated receptor-2 activating peptides or through trypsinization, elevates cAMP in keratinocytes. Proteinase-activated receptor-2 mediated Rho activation was pertussis toxin insensitive and independent of the protein kinase A signaling pathway. These data are the first to show that proteinase-activated receptor-2 mediated phagocytosis is Rho dependent and that proteinase-activated receptor-2 signals to Rho and cAMP in keratinocytes. Because phagocytosis of melanosomes is recognized as an important mechanism for melanosome transfer to keratinocytes, these results suggest that Rho is a critical signaling intermediate in melanosome uptake in keratinocytes.
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Affiliation(s)
- Glynis Scott
- Department of Dermatology, University of Rochester School of Medicine, 601 Elmwood Avenue, Rochester, NY 14618, USA.
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41
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Ikeguchi M, Hirooka Y, Kaibara N. Quantitative reverse transcriptase polymerase chain reaction analysis for KiSS-1 and orphan G-protein-coupled receptor (hOT7T175) gene expression in hepatocellular carcinoma. J Cancer Res Clin Oncol 2003; 129:531-5. [PMID: 12898236 DOI: 10.1007/s00432-003-0469-z] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2003] [Accepted: 05/22/2003] [Indexed: 01/01/2023]
Abstract
PURPOSE KiSS-1 has been cloned as a human metastasis suppressor gene and an orphan G-protein-coupled receptor (hOT7T175) identified as the endogenous receptor of the KiSS-1 product. In the present study, we evaluated the clinical importance of KiSS-1 and hOT7T175 gene expression in hepatocellular carcinoma (HCC). METHODS The expression levels of KiSS-1, hOT7T175 and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) messenger RNAs (mRNAs) were analyzed quantitatively by real-time reverse transcriptase polymerase chain reaction (RT-PCR) in 60 surgically resected HCCs. The KiSS-1/GAPDH and hOT7T175/GAPDH ratios of tumors were compared with clinicopathological findings. RESULTS Loss of KiSS-1 mRNA expression was not detected in HCCs. The mean KiSS-1/GAPDH ratio did not change between non-cancerous cirrhotic livers and carcinomas. On the other hand, the average hOT7T175/GAPDH ratios increased from non-cancerous livers (0.08) to carcinomas (0.48). Overexpression of KiSS-1 and hOT7T175 genes was recognized in 6 tumors, which were in an advanced stage and showed poor survival. CONCLUSION Overexpression of KiSS-1 and hOT7T175 genes was frequently observed and correlated with HCC progression; thus, the possibility that overexpressed KiSS-1 and hOT7T175 peptides mediate growth signals into cancer cells in HCCs is suggested.
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MESH Headings
- Adult
- Aged
- Aged, 80 and over
- Biomarkers, Tumor/analysis
- Biomarkers, Tumor/genetics
- Carcinoma, Hepatocellular/chemistry
- Carcinoma, Hepatocellular/pathology
- Disease Progression
- Disease-Free Survival
- Female
- Gene Expression Regulation, Neoplastic
- Genes, Tumor Suppressor
- Heterotrimeric GTP-Binding Proteins/analysis
- Humans
- Kisspeptins
- Liver Neoplasms/chemistry
- Liver Neoplasms/pathology
- Male
- Middle Aged
- Neoplasm Invasiveness
- Neoplasm Staging
- Proteins/analysis
- Proteins/genetics
- RNA, Messenger/analysis
- RNA, Neoplasm/analysis
- Receptors, G-Protein-Coupled
- Receptors, Kisspeptin-1
- Receptors, Neuropeptide/analysis
- Receptors, Neuropeptide/genetics
- Reverse Transcriptase Polymerase Chain Reaction
- Tumor Suppressor Proteins
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Affiliation(s)
- Masahide Ikeguchi
- Division of Operating Room, Faculty of Medicine, Tottori University, 36-1 Nishi-cho, 683-8504, Yonago, Japan.
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42
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Fruehauf S, Topaly J, Schad M, Paschka P, Gschaidmeier H, Zeller WJ, Hochhaus A, Ho AD. Imatinib restores expression of CD62L in BCR-ABL-positive cells. J Leukoc Biol 2003; 73:600-3. [PMID: 12714574 DOI: 10.1189/jlb.1002507] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Chronic myelogenous leukemia (CML) is characterized by aberrant trafficking of malignant hematopoietic progenitor cells in the peripheral blood. Expression of the cell adhesion molecule CD62L was reported to be significantly lower in CML patients than in normal controls. We studied whether the transcription of CD62L in CML cells is dependent on the activity of the BCR-ABL tyrosine kinase. Following addition of the Abelson (ABL) tyrosine kinase inhibitor imatinib (formerly STI571) to two BCR-ABL-positive cell lines (BV173, SD-1), we observed a dose-dependent increase in CD62L RNA levels of up to 45-fold by a quantitative, real-time polymerase chain reaction and an increase in the amount of cell surface-bound CD62L of up to 18-fold by quantitative flow cytometry, respectively. These data are validated by an increased CD62L expression in the bone marrow of patients (n=6) with advanced CML who received imatinib. Restoration of defective cell adhesion mediated via the CD62L pathway may be one mechanism of action of imatinib in BCR-ABL-positive leukemias.
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MESH Headings
- Antineoplastic Agents/pharmacology
- Benzamides
- Biomarkers, Tumor/analysis
- Dose-Response Relationship, Drug
- Enzyme Inhibitors/pharmacology
- Fusion Proteins, bcr-abl/analysis
- Gene Expression Regulation, Leukemic/drug effects
- Humans
- Imatinib Mesylate
- L-Selectin/biosynthesis
- L-Selectin/genetics
- Leukemia, Myelogenous, Chronic, BCR-ABL Positive/metabolism
- Leukemia, Myelogenous, Chronic, BCR-ABL Positive/pathology
- Neoplasm Proteins/biosynthesis
- Neoplasm Proteins/genetics
- Piperazines/pharmacology
- Polymerase Chain Reaction
- Pyrimidines/pharmacology
- RNA, Messenger/biosynthesis
- RNA, Neoplasm/biosynthesis
- Tumor Cells, Cultured/drug effects
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Affiliation(s)
- S Fruehauf
- Department of Internal Medicine V, University of Heidelberg, Germany.
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43
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Lin P, Ye RD. The lysophospholipid receptor G2A activates a specific combination of G proteins and promotes apoptosis. J Biol Chem 2003; 278:14379-86. [PMID: 12586833 DOI: 10.1074/jbc.m209101200] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
G2A, a G protein-coupled receptor for which lysophosphatidylcholine (LPC) is a high affinity ligand, belongs to a newly defined lysophospholipid receptor subfamily. Expression of G2A is transcriptionally up-regulated by stress-inducing and cell-damaging agents, and ectopic expression of G2A leads to growth inhibition. However, the G proteins that functionally couple to G2A have not been elucidated in detail. We report here that G2A ligand independently stimulates the accumulation of both inositol phosphates and cAMP. LPC does not further enhance inositol phosphate accumulation but dose-dependently augments intracellular cAMP concentration. Expression of G alpha(q) and G alpha(13) with G2A potentiates G2A-mediated activation of a NF-kappa B-luciferase reporter. These results demonstrate that G2A differentially couples to multiple G proteins including G alpha(s), G alpha(q), and G alpha(13), depending on whether it is bound to ligand. G2A-transfected HeLa cells display apoptotic signs including membrane blebbing, nuclear condensation, and reduction of mitochondrial membrane potential. Furthermore, G2A-induced apoptosis can be rescued by the caspase inhibitors, z-vad-fmk and CrmA. Although apoptosis occurs without LPC stimulation, LPC further enhances G2A-mediated apoptosis and correlates with its ability to induce cAMP elevation in both HeLa cells and primary lymphocytes. Rescue from G2A-induced apoptosis was achieved by co-expression of a G alpha(12/13)-specific inhibitor, p115RGS (regulator of G protein signaling), in combination with 2',5'-dideoxyadenosine treatment. These results demonstrate the ability of G2A to activate a specific combination of G proteins, and that G2A/LPC-induced apoptosis involves both G alpha(13)- and G alpha(s)-mediated pathways.
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Affiliation(s)
- Phoebe Lin
- Department of Pharmacology, College of Medicine, University of Illinois, Chicago 60612, USA
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Rikitake Y, Hirata KI, Yamashita T, Iwai K, Kobayashi S, Itoh H, Ozaki M, Ejiri J, Shiomi M, Inoue N, Kawashima S, Yokoyama M. Expression of G2A, a receptor for lysophosphatidylcholine, by macrophages in murine, rabbit, and human atherosclerotic plaques. Arterioscler Thromb Vasc Biol 2002; 22:2049-53. [PMID: 12482833 DOI: 10.1161/01.atv.0000040598.18570.54] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Lysophosphatidylcholine (LPC), a major phospholipid component of oxidized low density lipoprotein, has been demonstrated to induce multiple functional alterations of vasculature that are potentially involved in atherosclerosis. Recently, an orphan G-protein-coupled receptor, G2A, has been identified as a high-affinity receptor for LPC. Although it has been demonstrated that G2A is expressed predominantly in lymphoid tissues and lymphocytes, there are no reports to determine whether G2A is expressed in atherosclerotic lesions and cardiovascular cells. METHODS AND RESULTS Immunohistochemistry with an anti-G2A antibody revealed that G2A was expressed predominantly by macrophages within atherosclerotic lesions at the aortic root of apolipoprotein E-deficient mice and the thoracic aortas of Watanabe heritable hyperlipidemic rabbits. In atherosclerotic plaques of human coronary arterial specimens, G2A was expressed by macrophages within the lipid-rich plaques, whereas no immunoreactivity of G2A was observed in fibrous plaques where macrophages did not exist. Reverse transcription-polymerase chain reaction analysis demonstrated that G2A mRNA was highly expressed in human and murine monocytes/macrophages. The expression of G2A protein was detected in human and murine monocytes/macrophages by immunoblotting. CONCLUSIONS These findings demonstrate that monocytes/macrophages abundantly express G2A and suggest that G2A may play a role in the formation and progression of atherosclerotic lesions.
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MESH Headings
- Animals
- Aorta, Thoracic/chemistry
- Aorta, Thoracic/metabolism
- Apolipoproteins E/deficiency
- Cardiovascular System/metabolism
- Cardiovascular System/pathology
- Cell Cycle Proteins/biosynthesis
- Cell Cycle Proteins/immunology
- Cell Cycle Proteins/metabolism
- Cells, Cultured
- Coronary Artery Disease/metabolism
- Coronary Artery Disease/pathology
- Coronary Vessels/chemistry
- Coronary Vessels/metabolism
- Coronary Vessels/pathology
- Endothelium, Vascular/chemistry
- Endothelium, Vascular/cytology
- Endothelium, Vascular/pathology
- Humans
- Jurkat Cells/chemistry
- Jurkat Cells/metabolism
- Lysophosphatidylcholines/metabolism
- Macrophages/chemistry
- Macrophages/metabolism
- Macrophages/pathology
- Macrophages, Peritoneal/chemistry
- Macrophages, Peritoneal/metabolism
- Macrophages, Peritoneal/pathology
- Mice
- Mice, Knockout
- Monocytes/chemistry
- Monocytes/metabolism
- Muscle, Smooth, Vascular/chemistry
- Muscle, Smooth, Vascular/metabolism
- Muscle, Smooth, Vascular/pathology
- Rabbits
- Receptors, Cell Surface/biosynthesis
- Receptors, Cell Surface/immunology
- Receptors, Cell Surface/metabolism
- Receptors, G-Protein-Coupled
- Tumor Cells, Cultured
- Umbilical Veins/chemistry
- Umbilical Veins/metabolism
- Umbilical Veins/pathology
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Affiliation(s)
- Yoshiyuki Rikitake
- Division of Cardiovascular and Respiratory Medicine, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
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45
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Abstract
During the development and progression of human cancer, cells undergo numerous changes in morphology, proliferation, and transcriptional profile. Over the past couple of decades there have been intense efforts to understand the molecular mechanisms involved, and members of the Ras superfamily of small GTPases have emerged as important players. Mutated versions of the Ras genes were first identified in human cancers some 20 years ago, but more recently, the Rho branch of the family has been receiving increased attention. In addition to the experimental evidence implicating Rho GTPase signaling in promoting malignant transformation, genetic analysis of human cancers has now revealed a few examples of direct alterations in the genes encoding regulators of Rho GTPases. In this review, we discuss the evidence implicating Rho GTPases in transformation and metastasis, as well as the progress made toward identifying their biochemical mechanism of action.
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Affiliation(s)
- Aron B Jaffe
- CRC Oncogene and Signal Transduction Group, University College London, UK
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46
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Abstract
Despite the recognized effects of lysophosphatidylcholine upon cells of the immune system and its association with inflammatory processes, its mechanism of action has remained poorly characterized. Our recent identification of the first lysophosphatidylcholine receptor as an immunoregulatory G protein-coupled receptor named G2A whose genetic ablation results in the development of inflammatory autoimmune disease has, therefore, provided a new perspective on the role of this lysophospholipid as a modulator of immune responses. This commentary discusses the biological properties of lysophosphatidylcholine as an immunoregulatory ligand for cells of the innate and adaptive arms of the immune system. Although we focus primarily on ligand interactions with G2A, we also discuss the issue of possible functional redundancy with other receptors with recently established ligand specificities towards phosphorylcholine-containing lysolipids including lysophosphatidylcholine.
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Affiliation(s)
- Janusz H S Kabarowski
- Department of Microbiology, Immunology & Molecular Genetics, University of California-Los Angeles, 5-748 MRL, 675 Charles E. Young Drive South, Box 951662, Los Angeles, CA 90095-1662, USA.
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47
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Booden MA, Siderovski DP, Der CJ. Leukemia-associated Rho guanine nucleotide exchange factor promotes G alpha q-coupled activation of RhoA. Mol Cell Biol 2002; 22:4053-61. [PMID: 12024019 PMCID: PMC133844 DOI: 10.1128/mcb.22.12.4053-4061.2002] [Citation(s) in RCA: 147] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Leukemia-associated Rho guanine-nucleotide exchange factor (LARG) belongs to the subfamily of Dbl homology RhoGEF proteins (including p115 RhoGEF and PDZ-RhoGEF) that possess amino-terminal regulator of G protein signaling (RGS) boxes also found within GTPase-accelerating proteins (GAPs) for heterotrimeric G protein alpha subunits. p115 RhoGEF stimulates the intrinsic GTP hydrolysis activity of G alpha 12/13 subunits and acts as an effector for G13-coupled receptors by linking receptor activation to RhoA activation. The presence of RGS box and Dbl homology domains within LARG suggests this protein may also function as a GAP toward specific G alpha subunits and couple G alpha activation to RhoA-mediating signaling pathways. Unlike the RGS box of p115 RhoGEF, the RGS box of LARG interacts not only with G alpha 12 and G alpha 13 but also with G alpha q. In cellular coimmunoprecipitation studies, the LARG RGS box formed stable complexes with the transition state mimetic forms of G alpha q, G alpha 12, and G alpha 13. Expression of the LARG RGS box diminished the transforming activity of oncogenic G protein-coupled receptors (Mas, G2A, and m1-muscarinic cholinergic) coupled to G alpha q and G alpha 13. Activated G alpha q, as well as G alpha 12 and G alpha 13, cooperated with LARG and caused synergistic activation of RhoA, suggesting that all three G alpha subunits stimulate LARG-mediated activation of RhoA. Our findings suggest that the RhoA exchange factor LARG, unlike the related p115 RhoGEF and PDZ-RhoGEF proteins, can serve as an effector for Gq-coupled receptors, mediating their functional linkage to RhoA-dependent signaling pathways.
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Affiliation(s)
- Michelle A Booden
- Department of Pharmacology, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, 27599, USA.
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48
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Wing MR, Houston D, Kelley GG, Der CJ, Siderovski DP, Harden TK. Activation of phospholipase C-epsilon by heterotrimeric G protein betagamma-subunits. J Biol Chem 2001; 276:48257-61. [PMID: 11641393 DOI: 10.1074/jbc.c100574200] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
PLC-epsilon was identified recently as a phosphoinositide-hydrolyzing phospholipase C (PLC) containing catalytic domains (X, Y, and C2) common to all PLC isozymes as well as unique CDC25- and Ras-associating domains. Novel regulation of this PLC isozyme by the Ras oncoprotein and alpha-subunits (Galpha(12)) of heterotrimeric G proteins was illustrated. Sequence analyses of PLC-epsilon revealed previously unrecognized PH and EF-hand domains in the amino terminus. The known interaction of Gbetagamma subunits with the PH domains of other proteins led us to examine the capacity of Gbetagamma to activate PLC-epsilon. Co-expression of Gbeta(1)gamma(2) with PLC-epsilon in COS-7 cells resulted in marked stimulation of phospholipase C activity. Gbeta(2) and Gbeta(4) in combination with Ggamma(1), Ggamma(2), Ggamma(3), or Ggamma(13) also activated PLC-epsilon to levels similar to those observed with Gbeta(1)-containing dimers of these Ggamma-subunits. Gbeta(3) in combination with the same Ggamma-subunits was less active, and Gbeta(5)-containing dimers were essentially inactive. Gbetagamma-promoted activation of PLC-epsilon was blocked by cotransfection with either of two Gbetagamma-interacting proteins, Galpha(i1) or the carboxyl terminus of G protein receptor kinase 2. Pharmacological inhibition of PI3-kinase-gamma had no effect on Gbeta(1)gamma(2)-promoted activation of PLC-epsilon. Similarly, activation of Ras in the action of Gbetagamma is unlikely, because a mutation in the second RA domain of PLC-epsilon that blocks Ras activation of PLC failed to alter the stimulatory activity of Gbeta(1)gamma(2). Taken together, these results reveal the presence of additional functional domains in PLC-epsilon and add a new level of complexity in the regulation of this novel enzyme by heterotrimeric G proteins.
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Affiliation(s)
- M R Wing
- Department of Pharmacology, Program in Neurobiology, Lineberger Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599, USA
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49
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Shepard LW, Yang M, Xie P, Browning DD, Voyno-Yasenetskaya T, Kozasa T, Ye RD. Constitutive activation of NF-kappa B and secretion of interleukin-8 induced by the G protein-coupled receptor of Kaposi's sarcoma-associated herpesvirus involve G alpha(13) and RhoA. J Biol Chem 2001; 276:45979-87. [PMID: 11590141 DOI: 10.1074/jbc.m104783200] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The Kaposi's sarcoma herpesvirus (KSHV) open reading frame 74 encodes a G protein-coupled receptor (GPCR) for chemokines. Exogenous expression of this constitutively active GPCR leads to cell transformation and vascular overgrowth characteristic of Kaposi's sarcoma. We show here that expression of KSHV-GPCR in transfected cells results in constitutive transactivation of nuclear factor kappa B (NF-kappa B) and secretion of interleukin-8, and this response involves activation of G alpha(13) and RhoA. The induced expression of a NF-kappa B luciferase reporter was partially reduced by pertussis toxin and the G beta gamma scavenger transducin, and enhanced by co-expression of G alpha(13) and to a lesser extent, G alpha(q). These results indicate coupling of KSHV-GPCR to multiple G proteins for NF-kappa B activation. Expression of KSHV-GPCR led to stress fiber formation in NIH 3T3 cells. To examine the involvement of the G alpha(13)-RhoA pathway in KSHV-GPCR-mediated NF-kappa B activation, HeLa cells were transfected with KSHV-GPCR alone and in combination with the regulator of G protein signaling (RGS) from p115RhoGEF or a dominant negative RhoA(T19N). Both constructs, as well as the C3 exoenzyme from Clostritium botulinum, partially reduced NF-kappa B activation by KSHV-GPCR, and by a constitutively active G alpha(13)(Q226L). KSHV-GPCR-induced NF-kappa B activation is accompanied by increased secretion of IL-8, a function mimicked by the activated G alpha(13) but not by an activated G alpha(q)(Q209L). These results suggest coupling of KSHV-GPCR to the G alpha(13)-RhoA pathway in addition to other G proteins.
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Affiliation(s)
- L W Shepard
- Department of Pharmacology, College of Medicine, University of Illinois, Chicago, Illinois 60612, USA
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50
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Ye RD. Regulation of nuclear factor κB activation by G‐protein‐coupled receptors. J Leukoc Biol 2001. [DOI: 10.1189/jlb.70.6.839] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Affiliation(s)
- Richard D. Ye
- Department of Pharmacology, University of Illinois College of Medicine, Chicago, Illinois
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