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D’Souza CA, Zhao FL, Li X, Xu Y, Dunn SE, Zhang L. OGR1/GPR68 Modulates the Severity of Experimental Autoimmune Encephalomyelitis and Regulates Nitric Oxide Production by Macrophages. PLoS One 2016; 11:e0148439. [PMID: 26828924 PMCID: PMC4735495 DOI: 10.1371/journal.pone.0148439] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Accepted: 01/18/2016] [Indexed: 11/18/2022] Open
Abstract
Ovarian cancer G protein-coupled receptor 1 (OGR1) is a proton-sensing molecule that can detect decreases in extracellular pH that occur during inflammation. Although OGR1 has been shown to have pro-inflammatory functions in various diseases, its role in autoimmunity has not been examined. We therefore sought to determine whether OGR1 has a role in the development of T cell autoimmunity by contrasting the development of experimental autoimmune encephalomyelitis between wild type and OGR1-knockout mice. OGR1-knockout mice showed a drastically attenuated clinical course of disease that was associated with a profound reduction in the expansion of myelin oligodendrocyte glycoprotein 35-55-reactive T helper 1 (Th1) and Th17 cells in the periphery and a reduced accumulation of Th1 and Th17 effectors in the central nervous system. We determined that these impaired T cell responses in OGR1-knockout mice associated with a reduced frequency and number of dendritic cells in draining lymph nodes during EAE and a higher production of nitric oxide by macrophages. Our studies suggest that OGR1 plays a key role in regulating T cell responses during autoimmunity.
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Affiliation(s)
- Cheryl A. D’Souza
- Toronto General Research Institute, University Health Network, Toronto, Ontario, Canada
| | - Fei Linda Zhao
- Department of Immunology, University of Toronto, Toronto, Ontario, Canada
| | - Xujian Li
- Toronto General Research Institute, University Health Network, Toronto, Ontario, Canada
| | - Yan Xu
- Department of Obstetrics and Gynecology, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
| | - Shannon E. Dunn
- Toronto General Research Institute, University Health Network, Toronto, Ontario, Canada
- Department of Immunology, University of Toronto, Toronto, Ontario, Canada
- Women’s College Research Institute, Toronto, Ontario, Canada
- * E-mail: (LZ); (SED)
| | - Li Zhang
- Toronto General Research Institute, University Health Network, Toronto, Ontario, Canada
- Department of Immunology, University of Toronto, Toronto, Ontario, Canada
- Department of Laboratory Medicine and Pathobiology and Immunology, University of Toronto, Toronto, Ontario, Canada
- * E-mail: (LZ); (SED)
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Krieger NS, Yao Z, Kyker-Snowman K, Kim MH, Boyce BF, Bushinsky DA. Increased bone density in mice lacking the proton receptor OGR1. Kidney Int 2016; 89:565-73. [PMID: 26880453 DOI: 10.1016/j.kint.2015.12.020] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Revised: 08/18/2015] [Accepted: 09/09/2015] [Indexed: 12/24/2022]
Abstract
Chronic metabolic acidosis stimulates cell-mediated calcium efflux from bone through osteoblastic prostaglandin E2-induced stimulation of receptor activator of NF-kB ligand leading to increased osteoclastic bone resorption. Osteoblasts express the proton-sensing G-protein-coupled receptor OGR1, which activates inositol phosphate-mediated intracellular calcium. Proton-induced osteoblastic intracellular calcium signaling requires ovarian cancer G-protein-coupled receptor 1 (OGR1), suggesting that OGR1 is the sensor activated during acidosis to cause bone resorption. Growing mice produce large amounts of metabolic acids, which must be buffered, primarily by bone, before excretion by the kidney. Here we tested whether lack of OGR1 inhibits proton-induced bone resorption by measuring bone mineral density by micro-computed tomography and histomorphometry in 8-week-old male OGR1(-/-) and C57/Bl6 wild type mice. OGR1(-/-) mice have normal skeletal development with no atypical gross phenotype. Trabecular and cortical bone volume was increased in tibiae and vertebrae from OGR1(-/-). There were increased osteoblast numbers on the cortical and trabecular surfaces of tibiae from OGR1(-/-) mice, increased endocortical and trabecular bone formation rates, and osteoblastic gene expression. Osteoclast numbers and surface were increased in tibiae of OGR1(-/-) mice. Thus, in rapidly growing mice, lack of OGR1 leads to increased bone mass with increased bone turnover and a greater increase in bone formation than resorption. This supports the important role of the proton receptor OGR1 in the response of bone to protons.
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Affiliation(s)
- Nancy S Krieger
- Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, New York, USA.
| | - Zhenqiang Yao
- Department of Pathology, University of Rochester School of Medicine and Dentistry, Rochester, New York, USA
| | - Kelly Kyker-Snowman
- Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, New York, USA
| | - Min Ho Kim
- Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, New York, USA
| | - Brendan F Boyce
- Department of Pathology, University of Rochester School of Medicine and Dentistry, Rochester, New York, USA
| | - David A Bushinsky
- Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, New York, USA
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de Vallière C, Vidal S, Clay I, Jurisic G, Tcymbarevich I, Lang S, Ludwig MG, Okoniewski M, Eloranta JJ, Kullak-Ublick GA, Wagner CA, Rogler G, Seuwen K. The pH-sensing receptor OGR1 improves barrier function of epithelial cells and inhibits migration in an acidic environment. Am J Physiol Gastrointest Liver Physiol 2015. [PMID: 26206859 DOI: 10.1152/ajpgi.00408.2014] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The pH-sensing receptor ovarian cancer G protein-coupled receptor 1 (OGR1; GPR68) is expressed in the gut. Inflammatory bowel disease is typically associated with a decrease in local pH, which may lead to altered epithelial barrier function and subsequent gastrointestinal repair involving epithelial cell adhesion and migration. As the mechanisms underlying the response to pH changes are not well understood, we have investigated OGR1-mediated, pH-dependent signaling pathways in intestinal epithelial cells. Caco-2 cells stably overexpressing OGR1 were created and validated as tools to study OGR1 signaling. Barrier function, migration, and proliferation were measured using electric cell-substrate impedance-sensing technology. Localization of the tight junction proteins zonula occludens protein 1 and occludin and the rearrangement of cytoskeletal actin were examined by confocal microscopy. Paracellular permeability and protein and gene expression analysis using DNA microarrays were performed on filter-grown Caco-2 monolayers. We report that an acidic pH shift from pH 7.8 to 6.6 improved barrier function and stimulated reorganization of filamentous actin with prominent basal stress fiber formation. Cell migration and proliferation during in vitro wound healing were inhibited. Gene expression analysis revealed significant upregulation of genes related to cytoskeleton remodeling, cell adhesion, and growth factor signaling. We conclude that acidic extracellular pH can have a signaling function and impact the physiology of intestinal epithelial cells. The deconstruction of OGR1-dependent signaling may aid our understanding of mucosal inflammation mechanisms.
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Affiliation(s)
- Cheryl de Vallière
- Division of Gastroenterology and Hepatology, University Hospital Zurich, Zurich, Switzerland; Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Solange Vidal
- Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Ieuan Clay
- Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Giorgia Jurisic
- Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Irina Tcymbarevich
- Division of Gastroenterology and Hepatology, University Hospital Zurich, Zurich, Switzerland
| | - Silvia Lang
- Division of Gastroenterology and Hepatology, University Hospital Zurich, Zurich, Switzerland
| | | | - Michal Okoniewski
- Functional Genomics Center, University of Zurich, Zurich, Switzerland
| | - Jyrki J Eloranta
- Department of Clinical Pharmacology and Toxicology, University Hospital Zurich, Zurich, Switzerland
| | - Gerd A Kullak-Ublick
- Department of Clinical Pharmacology and Toxicology, University Hospital Zurich, Zurich, Switzerland
| | - Carsten A Wagner
- Institute of Physiology, University of Zurich, Zurich, Switzerland; and Zurich Center for Integrative Human Physiology, Zurich, Switzerland
| | - Gerhard Rogler
- Division of Gastroenterology and Hepatology, University Hospital Zurich, Zurich, Switzerland; Zurich Center for Integrative Human Physiology, Zurich, Switzerland
| | - Klaus Seuwen
- Novartis Institutes for Biomedical Research, Basel, Switzerland;
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Ahn SH, Lee SY, Baek JE, Lee SY, Park SY, Lee YS, Kim H, Kim BJ, Lee SH, Koh JM. Psychosine inhibits osteoclastogenesis and bone resorption via G protein-coupled receptor 65. J Endocrinol Invest 2015; 38:891-9. [PMID: 25841894 DOI: 10.1007/s40618-015-0276-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/30/2014] [Accepted: 03/17/2015] [Indexed: 01/20/2023]
Abstract
BACKGROUND It was recently reported that G protein-coupled receptor 65 (GPR65) suppresses ovariectomy-induced bone loss. AIM The present study investigated the role of the lysosphingolipid psychosine, a GPR65 ligand, on osteoclastic differentiation and bone resorption. METHODS Osteoclasts were differentiated from mouse bone marrow macrophages. Tartrate-resistant acid phosphatase-positive multinucleated cells were considered to be osteoclasts, and the resorption area was measured by incubating the cells on dentine discs. The expression levels of osteoclast differentiation markers were assessed by qRT-PCR. GPR65 siRNA and its scrambled siRNA were transfected with lipofectamine. Intracellular cyclic adenosine monophosphate (cAMP) levels were assessed using a direct enzyme immunoassay. RESULTS Psychosine inhibited osteoclastogenesis and in vitro bone resorption without any significant effect on the viability of pre-osteoclasts, decreased the expression of osteoclast differentiation markers significantly, and increased intracellular cAMP levels. The knockdown of GPR65 by its siRNA restored osteoclastogenesis and decreased cAMP levels in the presence of psychosine. CONCLUSION Psychosine inhibits osteoclastogenesis by increasing intracellular cAMP levels via GPR65.
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Affiliation(s)
- S H Ahn
- Division of Endocrinology and Metabolism, Asan Medical Center, University of Ulsan College of Medicine, 388-1 Poongnap-2Dong, Songpa-Gu, Seoul, 138-736, South Korea
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Tobo A, Tobo M, Nakakura T, Ebara M, Tomura H, Mogi C, Im DS, Murata N, Kuwabara A, Ito S, Fukuda H, Arisawa M, Shuto S, Nakaya M, Kurose H, Sato K, Okajima F. Characterization of Imidazopyridine Compounds as Negative Allosteric Modulators of Proton-Sensing GPR4 in Extracellular Acidification-Induced Responses. PLoS One 2015; 10:e0129334. [PMID: 26070068 PMCID: PMC4466532 DOI: 10.1371/journal.pone.0129334] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Accepted: 05/07/2015] [Indexed: 02/02/2023] Open
Abstract
G protein-coupled receptor 4 (GPR4), previously proposed as the receptor for sphingosylphosphorylcholine, has recently been identified as the proton-sensing G protein-coupled receptor (GPCR) coupling to multiple intracellular signaling pathways, including the Gs protein/cAMP and G13 protein/Rho. In the present study, we characterized some imidazopyridine compounds as GPR4 modulators that modify GPR4 receptor function. In the cells that express proton-sensing GPCRs, including GPR4, OGR1, TDAG8, and G2A, extracellular acidification stimulates serum responsive element (SRE)-driven transcriptional activity, which has been shown to reflect Rho activity, with different proton sensitivities. Imidazopyridine compounds inhibited the moderately acidic pH-induced SRE activity only in GPR4-expressing cells. Acidic pH-stimulated cAMP accumulation, mRNA expression of inflammatory genes, and GPR4 internalization within GPR4-expressing cells were all inhibited by the GPR4 modulator. We further compared the inhibition property of the imidazopyridine compound with psychosine, which has been shown to selectively inhibit actions induced by proton-sensing GPCRs, including GPR4. In the GPR4 mutant, in which certain histidine residues were mutated to phenylalanine, proton sensitivity was significantly shifted to the right, and psychosine failed to further inhibit acidic pH-induced SRE activation. On the other hand, the imidazopyridine compound almost completely inhibited acidic pH-induced action in mutant GPR4. We conclude that some imidazopyridine compounds show specificity to GPR4 as negative allosteric modulators with a different action mode from psychosine, an antagonist susceptible to histidine residues, and are useful for characterizing GPR4-mediated acidic pH-induced biological actions.
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Affiliation(s)
- Ayaka Tobo
- Laboratory of Signal Transduction, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan
| | - Masayuki Tobo
- Laboratory of Signal Transduction, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan
| | - Takashi Nakakura
- Laboratory of Signal Transduction, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan
| | - Masashi Ebara
- Laboratory of Signal Transduction, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan
| | - Hideaki Tomura
- Laboratory of Signal Transduction, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan
| | - Chihiro Mogi
- Laboratory of Signal Transduction, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan
| | - Dong-Soon Im
- Laboratory of Pharmacology, College of Pharmacy, Pusan National University, Busan, Republic of Korea
| | - Naoya Murata
- Laboratory of Signal Transduction, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan
| | - Atsushi Kuwabara
- Laboratory of Signal Transduction, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan
| | - Saki Ito
- Faculty of Pharmaceutical Science, Hokkaido University, Sapporo, Japan
| | - Hayato Fukuda
- Faculty of Pharmaceutical Science, Hokkaido University, Sapporo, Japan
| | - Mitsuhiro Arisawa
- Faculty of Pharmaceutical Science, Hokkaido University, Sapporo, Japan
| | - Satoshi Shuto
- Faculty of Pharmaceutical Science, Hokkaido University, Sapporo, Japan
- Center for Research and Education on Drug Discovery, Hokkaido University, Sapporo, Japan
| | - Michio Nakaya
- Department of Pharmacology and Toxicology, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan
| | - Hitoshi Kurose
- Department of Pharmacology and Toxicology, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan
| | - Koichi Sato
- Laboratory of Signal Transduction, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan
- * E-mail: (FO); (KS)
| | - Fumikazu Okajima
- Laboratory of Signal Transduction, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan
- * E-mail: (FO); (KS)
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Molinari G. Is hydrogen ion (H(+)) the real second messenger in calcium signalling? Cell Signal 2015; 27:1392-7. [PMID: 25843778 DOI: 10.1016/j.cellsig.2015.03.023] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Revised: 03/10/2015] [Accepted: 03/23/2015] [Indexed: 11/28/2022]
Abstract
Most second messengers have the acknowledged ability to mobilize the segregated Ca(2+) from intracellular stores, although the mechanisms of mobilization are unclear. To study this problem, the fact that inositol 1,4,5-trisphosphate, and six other known endogenous Ca(2+) mobilizers are acids, or acid-generating compounds, is highlighted. In physiological conditions, a newly generated acid releases H(+). The transient rise of H(+) in the cytosol may induce the lowering of pH, mobilization of bound Ca(2+), protein conformational rearrangement, store depletion, and Ca(2+) influx. Accordingly, a new description of the basic mechanism for signal transduction in non-excitable cells and the related consequences is put forward.
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Affiliation(s)
- Giuliano Molinari
- Biochemical Specialist at Molinari Giuliano, Via Agrigento 56, 37138 Verona Italy.
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Affiliation(s)
- Lonny R. Levin
- Department of Pharmacology, Weill Cornell Medical College, New York, NY 10065; ,
| | - Jochen Buck
- Department of Pharmacology, Weill Cornell Medical College, New York, NY 10065; ,
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Mochimaru Y, Azuma M, Oshima N, Ichijo Y, Satou K, Matsuda K, Asaoka Y, Nishina H, Nakakura T, Mogi C, Sato K, Okajima F, Tomura H. Extracellular acidification activates ovarian cancer G-protein-coupled receptor 1 and GPR4 homologs of zebra fish. Biochem Biophys Res Commun 2015; 457:493-9. [DOI: 10.1016/j.bbrc.2014.12.105] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2014] [Accepted: 12/24/2014] [Indexed: 02/02/2023]
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Ionotropic and metabotropic proton-sensing receptors involved in airway inflammation in allergic asthma. Mediators Inflamm 2014; 2014:712962. [PMID: 25197168 PMCID: PMC4147257 DOI: 10.1155/2014/712962] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2014] [Revised: 07/10/2014] [Accepted: 07/24/2014] [Indexed: 12/19/2022] Open
Abstract
An acidic microenvironment has been shown to evoke a variety of airway responses, including cough, bronchoconstriction, airway hyperresponsiveness (AHR), infiltration of inflammatory cells in the lung, and stimulation of mucus hyperproduction. Except for the participation of transient receptor potential vanilloid-1 (TRPV1) and acid-sensing ion channels (ASICs) in severe acidic pH (of less than 6.0)-induced cough and bronchoconstriction through sensory neurons, the molecular mechanisms underlying extracellular acidic pH-induced actions in the airways have not been fully understood. Recent studies have revealed that ovarian cancer G protein-coupled receptor 1 (OGR1)-family G protein-coupled receptors, which sense pH of more than 6.0, are expressed in structural cells, such as airway smooth muscle cells and epithelial cells, and in inflammatory and immune cells, such as eosinophils and dendritic cells. They function in a variety of airway responses related to the pathophysiology of inflammatory diseases, including allergic asthma. In the present review, we discuss the roles of ionotropic TRPV1 and ASICs and metabotropic OGR1-family G protein-coupled receptors in the airway inflammation and AHR in asthma and respiratory diseases.
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Acidic pH increases cGMP accumulation through the OGR1/phospholipase C/Ca(2+)/neuronal NOS pathway in N1E-115 neuronal cells. Cell Signal 2014; 26:2326-32. [PMID: 25025574 DOI: 10.1016/j.cellsig.2014.07.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Accepted: 07/09/2014] [Indexed: 12/29/2022]
Abstract
Neuronal NO synthase (nNOS)-mediated cGMP accumulation has been shown to affect a variety of neuronal cell activities, regardless of whether they are detrimental or beneficial, depending on the amount of their levels, under the physiological and pathological situations. In the present study, we examined the role of proton-sensing G protein-coupled receptors (GPCRs), which have been identified as new pH sensors, in the acidic pH-induced nNOS/cGMP activity in N1E-115 neuronal cells. In this cell line, ovarian cancer G protein-coupled receptor 1 (OGR1) and G protein-coupled receptor 4 (GPR4) mRNAs are expressed. An extracellular acidic pH increased cGMP accumulation, which was inhibited by nNOS-specific inhibitors. Acidic pH also activated phospholipase C/Ca(2+) pathways and Akt-induced phosphorylation of nNOS at S1412, both of which have been shown to be critical regulatory mechanisms for nNOS activation. The acidic pH-induced activation of the phospholipase C/Ca(2+) pathway, but not Akt/nNOS phosphorylation, was inhibited by small interfering RNA specific to OGR1 and YM-254890, an inhibitor of Gq/11 proteins, in association with the inhibition of cGMP accumulation. Moreover cGMP accumulation was inhibited by 2-aminoethoxydiphenyl borate, an inhibitor of inositol 1,4,5-trisphosphate channel; however, it was not by wortmannin, a phosphatidylinositol 3-kinase inhibitor, which inhibited Akt/nNOS phosphorylation. In conclusion, acidic pH stimulates cGMP accumulation preferentially through the OGR1/Gq/11 proteins/phospholipase C/Ca(2+)/nNOS in N1E-115 neuronal cells. Akt-mediated phosphorylation of nNOS, however, does not appreciably contribute to the acidification-induced accumulation of cGMP.
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Microenvironmental Influences on Metastasis Suppressor Expression and Function during a Metastatic Cell's Journey. CANCER MICROENVIRONMENT 2014; 7:117-31. [PMID: 24938990 DOI: 10.1007/s12307-014-0148-4] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Accepted: 06/08/2014] [Indexed: 12/21/2022]
Abstract
Metastasis is the process of primary tumor cells breaking away and colonizing distant secondary sites. In order for a tumor cell growing in one microenvironment to travel to, and flourish in, a secondary environment, it must survive a series of events termed the metastatic cascade. Before departing the primary tumor, cells acquire genetic and epigenetic changes that endow them with properties not usually associated with related normal differentiated cells. Those cells also induce a subset of bone marrow-derived stem cells to mobilize and establish pre-metastatic niches [1]. Many tumor cells undergo epithelial-to-mesenchymal transition (EMT), where they transiently acquire morphologic changes, reduced requirements for cell-cell contact and become more invasive [2]. Invasive tumor cells eventually enter the circulatory (hematogenous) or lymphatic systems or travel across body cavities. In transit, tumor cells must resist anoikis, survive sheer forces and evade detection by the immune system. For blood-borne metastases, surviving cells then arrest or adhere to endothelial linings before either proliferating or extravasating. Eventually, tumor cells complete the process by proliferating to form a macroscopic mass [3].Up to 90 % of all cancer related morbidity and mortality can be attributed to metastasis. Surgery manages to ablate most primary tumors, especially when combined with chemotherapy and radiation. But if cells have disseminated, survival rates drop precipitously. While multiple parameters of the primary tumor are predictive of local or distant relapse, biopsies remain an imperfect science. The introduction of molecular and other biomarkers [4, 5] continue to improve the accuracy of prognosis. However, the invasive procedure introduces new complications for the patient. Likewise, the heterogeneity of any tumor population [3, 6, 7] means that sampling error (i.e., since it is impractical to examine the entire tumor) necessitates further improvements.In the case of breast cancer, for example, women diagnosed with stage I diseases (i.e., no evidence of invasion through a basement membrane) still have a ~30 % likelihood of developing distant metastases [8]. Many physicians and patients opt for additional chemotherapy in order to "mop up" cells that have disseminated and have the potential to grow into macroscopic metastases. This means that ~ 70 % of patients receive unnecessary therapy, which has undesirable side effects. Therefore, improving prognostic capability is highly desirable.Recent advances allow profiling of primary tumor DNA sequences and gene expression patterns to define a so-called metastatic signature [9-11], which can be predictive of patient outcome. However, the genetic changes that a tumor cell must undergo to survive the initial events of the metastatic cascade and colonize a second location belie a plasticity that may not be adequately captured in a sampling of heterogeneous tumors. In order to tailor or personalize patient treatments, a more accurate assessment of the genetic profile in the metastases is needed. Biopsy of each individual metastasis is not practical, safe, nor particularly cost-effective. In recent years, there has been a resurrection of the notion to do a 'liquid biopsy,' which essentially involves sampling of circulating tumor cells (CTC) and/or cell free nucleic acids (cfDNA, including microRNA (miRNA)) present in blood and lymph [12-16].The rationale for liquid biopsy is that tumors shed cells and/or genetic fragments into the circulation, theoretically making the blood representative of not only the primary tumor but also distant metastases. Logically, one would predict that the proportion of CTC and/or cfDNA would be proportionate to the likelihood of developing metastases [14]. While a linear relationship does not exist, the information within CTC or cfDNA is beginning to show great promise for enabling a global snapshot of the disease. However, the CTC and cfDNA are present at extremely low levels. Nonetheless, newer technologies capture enough material to enrich and sequence the patient's DNA or quantification of some biomarkers.Among the biomarkers showing great promise are metastasis suppressors which, by definition, block a tumor cell's ability to complete the metastatic process without prohibiting primary tumor growth [17]. Since the discovery of the first metastasis suppressor, Nm23, more than 30 have been functionally characterized. They function at various stages of the metastatic cascade, but their mechanisms of action, for the most part, remain ill-defined. Deciphering the molecular interactions of functional metastasis suppressors may provide insights for targeted therapies when these regulators cease to function and result in metastatic disease.In this brief review, we summarize what is known about the various metastasis suppressors and their functions at individual steps of the metastatic cascade (Table 1). Some of the subdivisions are rather arbitrary in nature, since many metastasis suppressors affect more than one step in the metastatic cascade. Nonetheless what emerges is a realization that metastasis suppressors are intimately associated with the microenvironments in which cancer cells find themselves [18].
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Thongon N, Ketkeaw P, Nuekchob C. The roles of acid-sensing ion channel 1a and ovarian cancer G protein-coupled receptor 1 on passive Mg2+ transport across intestinal epithelium-like Caco-2 monolayers. J Physiol Sci 2014; 64:129-39. [PMID: 24375028 PMCID: PMC10717441 DOI: 10.1007/s12576-013-0301-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2013] [Accepted: 12/10/2013] [Indexed: 02/06/2023]
Abstract
Intestinal passive Mg(2+) absorption, which is vital for normal Mg(2+) homeostasis, has been shown to be regulated by luminal proton. We aimed to study the regulatory role of intestinal acid sensors in paracellular passive Mg(2+) transport. Omeprazole enhanced the expressions of acid-sensing ion channel 1a (ASIC1a), ovarian cancer G protein-coupled receptor 1 (OGR1), and transient receptor potential vanilloid 4 in Caco-2 cells. It also inhibited passive Mg(2+) transport across Caco-2 monolayers. The expression and activation of OGR1 resulted in the stimulation of passive Mg(2+) transport via phospholipase C- and protein kinase C-dependent pathways. ASIC1a activation, on the other hand, enhanced apical HCO3 (-) secretion that led, at least in part, by a Ca(2+)-dependent pathway to an inhibition of paracellular Mg(2+) absorption. Our results provided supporting evidence for the roles of OGR1 and ASIC1a in the regulation of intestinal passive Mg(2+) absorption.
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Affiliation(s)
- Narongrit Thongon
- Division of Physiology, Department of Biomedical Sciences, Faculty of Allied Health Sciences, Burapha University, 169 Long-Hard Bangsaen Rd., Saensook, Muang, Chonburi, 20131, Thailand,
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Jin Y, Sato K, Tobo A, Mogi C, Tobo M, Murata N, Ishii S, Im DS, Okajima F. Inhibition of interleukin-1β production by extracellular acidification through the TDAG8/cAMP pathway in mouse microglia. J Neurochem 2014; 129:683-95. [PMID: 24447140 DOI: 10.1111/jnc.12661] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2013] [Accepted: 01/16/2014] [Indexed: 12/23/2022]
Abstract
Interleukin-1β (IL-1β) is released from activated microglia and involved in the neurodegeneration of acute and chronic brain disorders, such as stroke and Alzheimer's disease, in which extracellular acidification has been shown to occur. Here, we examined the extracellular acidic pH regulation of IL-1β production, especially focusing on TDAG8, a major proton-sensing G-protein-coupled receptor, in mouse microglia. Extracellular acidification inhibited lipopolysaccharide -induced IL-1β production, which was associated with the inhibition of IL-1β cytoplasmic precursor and mRNA expression. The IL-1β mRNA and protein responses were significantly, though not completely, attenuated in microglia derived from TDAG8-deficient mice compared with those from wild-type mice. The acidic pH also stimulated cellular cAMP accumulation, which was completely inhibited by TDAG8 deficiency. Forskolin and a cAMP derivative, which specifically stimulates protein kinase A (PKA), mimicked the proton actions, and PKA inhibitors reversed the acidic pH-induced IL-1β mRNA expression. The acidic pH-induced inhibitory IL-1β responses were accompanied by the inhibition of extracellular signal-related kinase and c-Jun N-terminal kinase activities. The inhibitory enzyme activities in response to acidic pH were reversed by the PKA inhibitor and TDAG8 deficiency. We conclude that extracellular acidic pH inhibits lipopolysaccharide-induced IL-1β production, at least partly, through the TDAG8/cAMP/PKA pathway, by inhibiting extracellular signal-related kinase and c-Jun N-terminal kinase activities, in mouse microglia.
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Affiliation(s)
- Ye Jin
- Laboratory of Signal Transduction, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan
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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: 238] [Impact Index Per Article: 21.6] [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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Alexander SPH, Benson HE, Faccenda E, Pawson AJ, Sharman JL, Spedding M, Peters JA, Harmar AJ. The Concise Guide to PHARMACOLOGY 2013/14: G protein-coupled receptors. Br J Pharmacol 2013; 170:1459-581. [PMID: 24517644 PMCID: PMC3892287 DOI: 10.1111/bph.12445] [Citation(s) in RCA: 505] [Impact Index Per Article: 45.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The Concise Guide to PHARMACOLOGY 2013/14 provides concise overviews of the key properties of over 2000 human drug targets with their pharmacology, plus links to an open access knowledgebase of drug targets and their ligands (www.guidetopharmacology.org), which provides more detailed views of target and ligand properties. The full contents can be found at http://onlinelibrary.wiley.com/doi/10.1111/bph.12444/full. G protein-coupled receptors are one of the seven major pharmacological targets into which the Guide is divided, with the others being G protein-coupled receptors, ligand-gated ion channels, ion channels, catalytic receptors, nuclear hormone receptors, transporters and enzymes. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. A new landscape format has easy to use tables comparing related targets. It is a condensed version of material contemporary to late 2013, which is presented in greater detail and constantly updated on the website www.guidetopharmacology.org, superseding data presented in previous Guides to Receptors and Channels. It is produced in conjunction with NC-IUPHAR and provides the official IUPHAR classification and nomenclature for human drug targets, where appropriate. It consolidates information previously curated and displayed separately in IUPHAR-DB and the Guide to Receptors and Channels, providing a permanent, citable, point-in-time record that will survive database updates.
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Affiliation(s)
- Stephen PH Alexander
- School of Life Sciences, University of Nottingham Medical SchoolNottingham, NG7 2UH, UK
| | - Helen E Benson
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
| | - Elena Faccenda
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
| | - Adam J Pawson
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
| | - Joanna L Sharman
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
| | | | - John A Peters
- Neuroscience Division, Medical Education Institute, Ninewells Hospital and Medical School, University of DundeeDundee, DD1 9SY, UK
| | - Anthony J Harmar
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
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Hikiji H, Endo D, Horie K, Harayama T, Akahoshi N, Igarashi H, Kihara Y, Yanagida K, Takeda J, Koji T, Shimizu T, Ishii S. TDAG8 activation inhibits osteoclastic bone resorption. FASEB J 2013; 28:871-9. [DOI: 10.1096/fj.13-233106] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Affiliation(s)
- Hisako Hikiji
- Department of Biochemistry and Molecular BiologyFaculty of MedicineThe University of TokyoTokyoJapan
| | - Daisuke Endo
- Department of Histology and Cell BiologyNagasaki University Graduate School of Biomedical SciencesNagasakiJapan
| | - Kyoji Horie
- Department of Social and Environmental MedicineGraduate School of MedicineOsaka UniversityOsakaJapan
| | - Takeshi Harayama
- Department of Biochemistry and Molecular BiologyFaculty of MedicineThe University of TokyoTokyoJapan
| | - Noriyuki Akahoshi
- Department of ImmunologyGraduate School of MedicineAkita UniversityAkitaJapan
| | - Hidemitsu Igarashi
- Department of ImmunologyGraduate School of MedicineAkita UniversityAkitaJapan
| | - Yasuyuki Kihara
- Department of Biochemistry and Molecular BiologyFaculty of MedicineThe University of TokyoTokyoJapan
| | - Keisuke Yanagida
- Department of Biochemistry and Molecular BiologyFaculty of MedicineThe University of TokyoTokyoJapan
| | - Junji Takeda
- Department of Social and Environmental MedicineGraduate School of MedicineOsaka UniversityOsakaJapan
| | - Takehiko Koji
- Department of Histology and Cell BiologyNagasaki University Graduate School of Biomedical SciencesNagasakiJapan
| | - Takao Shimizu
- Department of Biochemistry and Molecular BiologyFaculty of MedicineThe University of TokyoTokyoJapan
| | - Satoshi Ishii
- Department of Biochemistry and Molecular BiologyFaculty of MedicineThe University of TokyoTokyoJapan
- Department of ImmunologyGraduate School of MedicineAkita UniversityAkitaJapan
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Regulation of inflammation by extracellular acidification and proton-sensing GPCRs. Cell Signal 2013; 25:2263-71. [PMID: 23917207 DOI: 10.1016/j.cellsig.2013.07.022] [Citation(s) in RCA: 129] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2013] [Accepted: 07/26/2013] [Indexed: 12/14/2022]
Abstract
Under ischemic and inflammatory circumstances, such as allergic airway asthma, rheumatoid arthritis, atherosclerosis, and tumors, extracellular acidification occurs due to the stimulation of anaerobic glycolysis. An acidic microenvironment has been shown to modulate pro-inflammatory or anti-inflammatory responses, including cyclooxygenase-2 (COX-2) expression, prostaglandin synthesis, and cytokine expression, in a variety of cell types, and thereby to exacerbate or ameliorate inflammation. However, molecular mechanisms underlying extracellular acidic pH-induced actions have not been fully understood. Recent studies have shown that ovarian cancer G protein-coupled receptor 1 (OGR1)-family G protein-coupled receptors (GPCRs) can sense extracellular pH or protons, which in turn stimulates intracellular signaling pathways and subsequent diverse cellular responses. In the present review, I discuss extracellular acidic pH-induced inflammatory responses and related responses in inflammatory cells, such as macrophages and neutrophils, and non-inflammatory cells, such as smooth muscle cells and endothelial cells, focusing especially on proton-sensing GPCRs.
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Davenport AP, Alexander SPH, Sharman JL, Pawson AJ, Benson HE, Monaghan AE, Liew WC, Mpamhanga CP, Bonner TI, Neubig RR, Pin JP, Spedding M, Harmar AJ. International Union of Basic and Clinical Pharmacology. LXXXVIII. G protein-coupled receptor list: recommendations for new pairings with cognate ligands. Pharmacol Rev 2013; 65:967-86. [PMID: 23686350 PMCID: PMC3698937 DOI: 10.1124/pr.112.007179] [Citation(s) in RCA: 226] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
In 2005, the International Union of Basic and Clinical Pharmacology Committee on Receptor Nomenclature and Drug Classification (NC-IUPHAR) published a catalog of all of the human gene sequences known or predicted to encode G protein-coupled receptors (GPCRs), excluding sensory receptors. This review updates the list of orphan GPCRs and describes the criteria used by NC-IUPHAR to recommend the pairing of an orphan receptor with its cognate ligand(s). The following recommendations are made for new receptor names based on 11 pairings for class A GPCRs: hydroxycarboxylic acid receptors [HCA₁ (GPR81) with lactate, HCA₂ (GPR109A) with 3-hydroxybutyric acid, HCA₃ (GPR109B) with 3-hydroxyoctanoic acid]; lysophosphatidic acid receptors [LPA₄ (GPR23), LPA₅ (GPR92), LPA₆ (P2Y5)]; free fatty acid receptors [FFA4 (GPR120) with omega-3 fatty acids]; chemerin receptor (CMKLR1; ChemR23) with chemerin; CXCR7 (CMKOR1) with chemokines CXCL12 (SDF-1) and CXCL11 (ITAC); succinate receptor (SUCNR1) with succinate; and oxoglutarate receptor [OXGR1 with 2-oxoglutarate]. Pairings are highlighted for an additional 30 receptors in class A where further input is needed from the scientific community to validate these findings. Fifty-seven human class A receptors (excluding pseudogenes) are still considered orphans; information has been provided where there is a significant phenotype in genetically modified animals. In class B, six pairings have been reported by a single publication, with 28 (excluding pseudogenes) still classified as orphans. Seven orphan receptors remain in class C, with one pairing described by a single paper. The objective is to stimulate research into confirming pairings of orphan receptors where there is currently limited information and to identify cognate ligands for the remaining GPCRs. Further information can be found on the IUPHAR Database website (http://www.iuphar-db.org).
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Affiliation(s)
- Anthony P Davenport
- Clinical Pharmacology Unit, University of Cambridge, Level 6, Centre for Clinical Investigation, Box 110, Addenbrooke's Hospital, Cambridge CB2 0QQ, UK.
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Gallo PM, Gallucci S. The dendritic cell response to classic, emerging, and homeostatic danger signals. Implications for autoimmunity. Front Immunol 2013; 4:138. [PMID: 23772226 PMCID: PMC3677085 DOI: 10.3389/fimmu.2013.00138] [Citation(s) in RCA: 120] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2013] [Accepted: 05/23/2013] [Indexed: 12/18/2022] Open
Abstract
Dendritic cells (DCs) initiate and control immune responses, participate in the maintenance of immunological tolerance and are pivotal players in the pathogenesis of autoimmunity. In patients with autoimmune disease and in experimental animal models of autoimmunity, DCs show abnormalities in both numbers and activation state, expressing immunogenic levels of costimulatory molecules and pro-inflammatory cytokines. Exogenous and endogenous danger signals activate DCs to stimulate the immune response. Classic endogenous danger signals are released, activated, or secreted by host cells and tissues experiencing stress, damage, and non-physiologic cell death; and are therefore referred to as damage-associated molecular patterns (DAMPs). Some DAMPs are released from cells, where they are normally sequestered, during necrosis (e.g., heat shock proteins, uric acid, ATP, HMGB1, mitochondria-derived molecules). Others are actively secreted, like Type I Interferons. Here we discuss important DAMPs in the context of autoimmunity. For some, there is a clear pathogenic link (e.g., nucleic acids and lupus). For others, there is less evidence. Additionally, we explore emerging danger signals. These include inorganic materials and man-made technologies (e.g., nanomaterials) developed as novel therapeutic approaches. Some nanomaterials can activate DCs and may trigger unintended inflammatory responses. Finally, we will review “homeostatic danger signals,” danger signals that do not derive directly from pathogens or dying cells but are associated with perturbations of tissue/cell homeostasis and may signal pathological stress. These signals, like acidosis, hypoxia, and changes in osmolarity, also play a role in inflammation and autoimmunity.
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Affiliation(s)
- Paul M Gallo
- Laboratory of Dendritic Cell Biology, Department of Microbiology and Immunology, Temple Autoimmunity Center, Temple University School of Medicine , Philadelphia, PA , USA
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Lukashova V, Jinadasa T, Ilie A, Verbich D, Cooper E, Orlowski J. The Na(+)/H (+) exchanger NHE5 is sorted to discrete intracellular vesicles in the central and peripheral nervous systems. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2013; 961:397-410. [PMID: 23224898 DOI: 10.1007/978-1-4614-4756-6_34] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The pH milieu of the central and peripheral nervous systems is an important determinant of neuronal excitability, function, and survival. In mammals, neural acid-base homeostasis is coordinately regulated by ion transporters belonging to the Na(+)/H(+) exchanger (NHE) and bicarbonate transporter gene families. However, the relative contributions of individual isoforms within the respective families are not fully understood. This report focuses on the NHE family, specifically the plasma membrane-type NHE5 which is preferentially transcribed in brain, but the distribution of the native protein has not been extensively characterized. To this end, we generated a rabbit polyclonal antibody that specifically recognizes NHE5. In both central (cortex, hippocampus) and peripheral (superior cervical ganglia, SCG) nervous tissue of mice, NHE5 immunostaining was punctate and highly concentrated in the somas and to lesser amounts in the dendrites of neurons. Very little signal was detected in axons. Similarly, in primary cultures of differentiated SCG neurons, NHE5 localized predominantly to vesicles in the somatodendritic compartment, though some immunostaining was also evident in punctate vesicles along the axons. NHE5 was also detected predominantly in intracellular vesicles of cultured SCG glial cells. Dual immunolabeling of SCG neurons showed that NHE5 did not colocalize with markers for early endosomes (EEA1) or synaptic vesicles (synaptophysin), but did partially colocalize with the transferrin receptor, a marker of recycling endosomes. Collectively, these data suggest that NHE5 partitions into a unique vesicular pool in neurons that shares some characteristics of recycling endosomes where it may serve as an important regulated store of functional transporters required to maintain cytoplasmic pH homeostasis.
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71
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Grzelczyk A, Gendaszewska-Darmach E. Novel bioactive glycerol-based lysophospholipids: new data -- new insight into their function. Biochimie 2012; 95:667-79. [PMID: 23089136 DOI: 10.1016/j.biochi.2012.10.009] [Citation(s) in RCA: 115] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2012] [Accepted: 10/11/2012] [Indexed: 11/28/2022]
Abstract
Based on the results of research conducted over last two decades, lysophospholipids (LPLs) were observed to be not only structural components of cellular membranes but also biologically active molecules influencing a broad variety of processes such as carcinogenesis, neurogenesis, immunity, vascular development or regulation of metabolic diseases. With a growing interest in the involvement of extracellular lysophospholipids in both normal physiology and pathology, it has become evident that those small molecules may have therapeutic potential. While lysophosphatidic acid (LPA) and sphingosine-1-phosphate (S1P) have been studied in detail, other LPLs such as lysophosphatidylglycerol (LPG), lysophosphatidylserine (LPS), lysophosphatidylinositol (LPI), lysophosphatidylethanolamine (LPE) or even lysophosphatidylcholine (LPC) have not been elucidated to such a high degree. Although information concerning the latter LPLs is sparse as compared to LPA and S1P, within the last couple of years much progress has been made. Recently published data suggest that these compounds may regulate fundamental cellular activities by modulating multiple molecular targets, e.g. by binding to specific receptors and/or altering the structure and fluidity of lipid rafts. Therefore, the present review is devoted to novel bioactive glycerol-based lysophospholipids and recent findings concerning their functions and possible signaling pathways regulating physiological and pathological processes.
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Affiliation(s)
- Anna Grzelczyk
- Institute of Technical Biochemistry, Faculty of Biotechnology and Food Sciences, Lodz University of Technology, Stefanowskiego 4/10, 90-924 Lodz, Poland
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72
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Saxena H, Deshpande DA, Tiegs BC, Yan H, Battafarano RJ, Burrows WM, Damera G, Panettieri RA, Dubose TD, An SS, Penn RB. The GPCR OGR1 (GPR68) mediates diverse signalling and contraction of airway smooth muscle in response to small reductions in extracellular pH. Br J Pharmacol 2012; 166:981-90. [PMID: 22145625 DOI: 10.1111/j.1476-5381.2011.01807.x] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
BACKGROUND AND PURPOSE Previous studies have linked a reduction in pH in airway, caused by either environmental factors, microaspiration of gastric acid or inflammation, with airway smooth muscle (ASM) contraction and increased airway resistance. Neural mechanisms have been shown to mediate airway contraction in response to reductions in airway pH to < 6.5; whether reduced extracellular pH (pHo) has direct effects on ASM is unknown. EXPERIMENTAL APPROACH Intracellular signalling events stimulated by reduced pHo in human cultured ASM cells were examined by immunoblotting, phosphoinositide hydrolysis and calcium mobilization assays. ASM cell contractile state was examined using magnetic twisting cytometry. The expression of putative proton-sensing GPCRs in ASM was assessed by real-time PCR. The role of ovarian cancer G protein-coupled receptor 1 (OGR1 or GPR68) in acid-induced ASM signalling and contraction was assessed in cultures subjected to siRNA-mediated OGR1 knockdown. KEY RESULTS ASM cells responded to incremental reductions in pHo (from pH 8.0 to pH 6.8) by activating multiple signalling pathways, involving p42/p44, PKB, PKA and calcium mobilization. Coincidently, ASM cells contracted in response to decreased pHo with similar 'dose'-dependence. Real-time PCR suggested OGR1 was the only proton-sensing GPCR expressed in ASM cells. Both acid-induced signalling (with the exception of PKB activation) and contraction were significantly attenuated by knockdown of OGR1. CONCLUSIONS AND IMPLICATIONS These studies reveal OGR1 to be a physiologically relevant GPCR in ASM cells, capable of pleiotropic signalling and mediating contraction in response to small reductions in extracellular pH. Accordingly, ASM OGR1 may contribute to asthma pathology and represent a therapeutic target in obstructive lung diseases.
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Affiliation(s)
- H Saxena
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Maryland School of Medicine, Baltimore, MD 21201-1075, USA
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Nakakura T, Mogi C, Tobo M, Tomura H, Sato K, Kobayashi M, Ohnishi H, Tanaka S, Wayama M, Sugiyama T, Kitamura T, Harada A, Okajima F. Deficiency of proton-sensing ovarian cancer G protein-coupled receptor 1 attenuates glucose-stimulated insulin secretion. Endocrinology 2012; 153:4171-80. [PMID: 22733973 DOI: 10.1210/en.2012-1164] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Ovarian cancer G protein-coupled receptor 1 (OGR1) has been shown as a receptor for protons. In the present study, we aimed to know whether OGR1 plays a role in insulin secretion and, if so, the manner in which it does. To this end, we created OGR1-deficient mice and examined insulin secretion activity in vivo and in vitro. OGR1 deficiency reduced insulin secretion induced by glucose administered ip, although it was not associated with glucose intolerance in vivo. Increased insulin sensitivity and reduced plasma glucagon level may explain, in part, the unusual normal glucose tolerance. In vitro islet experiments revealed that glucose-stimulated insulin secretion was dependent on extracellular pH and sensitive to OGR1; insulin secretion at pH 7.4 to 7.0, but not 8.0, was significantly suppressed by OGR1 deficiency and inhibition of G(q/11) proteins. Insulin secretion induced by KCl and tolbutamide was also significantly inhibited, whereas that induced by several insulin secretagogues, including vasopressin, a glucagon-like peptide 1 receptor agonist, and forskolin, was not suppressed by OGR1 deficiency. The inhibition of insulin secretion was associated with the reduction of glucose-induced increase in intracellular Ca(2+) concentration. In conclusion, the OGR1/G(q/11) protein pathway is activated by extracellular protons existing under the physiological extracellular pH of 7.4 and further stimulated by acidification, resulting in the enhancement of insulin secretion in response to high glucose concentrations and KCl.
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Affiliation(s)
- Takashi Nakakura
- 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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Custodi C, Nuti R, Oprea TI, Macchiarulo A. Fitting the complexity of GPCRs modulation into simple hypotheses of ligand design. J Mol Graph Model 2012; 38:70-81. [PMID: 23079642 DOI: 10.1016/j.jmgm.2012.07.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Revised: 06/29/2012] [Accepted: 07/02/2012] [Indexed: 01/26/2023]
Abstract
G-protein coupled receptors (GPCR(s)) are a large family of membrane-bound receptors that mediate a wide range of physiologic responses to hormones, neurotransmitters and dietary lipids, which represent an important class of drug targets. Significant chemical space regions have been explored both in the academia and by pharmaceutical companies, in the quest for new GPCR modulators as potential therapeutic agents. This accumulated body of evidence provides new opportunities to evaluate potential features of GPCR agonists and antagonists, and how to distinguish them. In this study, the chemical space covered within the WOMBAT database by GPCRs modulators was investigated with the aim of identifying specific molecular determinants that distinguish GPCR agonists from antagonists. While instrumental to get insights into the design strategies of GPCRs modulators, the results of this study provide novel clues on the molecular mechanisms that underlie the complexity of GPCR modulation.
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Affiliation(s)
- Chiara Custodi
- Dipartimento di Chimica e Tecnologia del Farmaco, Università di Perugia, via del Liceo 1, 06123 Perugia, Italy
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Russell JL, Goetsch SC, Aguilar HR, Coe H, Luo X, Liu N, van Rooij E, Frantz DE, Schneider JW. Regulated expression of pH sensing G Protein-coupled receptor-68 identified through chemical biology defines a new drug target for ischemic heart disease. ACS Chem Biol 2012; 7:1077-83. [PMID: 22462679 DOI: 10.1021/cb300001m] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Chemical biology promises discovery of new and unexpected mechanistic pathways, protein functions and disease targets. Here, we probed the mechanism-of-action and protein targets of 3,5-disubstituted isoxazoles (Isx), cardiomyogenic small molecules that target Notch-activated epicardium-derived cells (NECs) in vivo and promote functional recovery after myocardial infarction (MI). Mechanistic studies in NECs led to an Isx-activated G(q) protein-coupled receptor (G(q)PCR) hypothesis tested in a cell-based functional target screen for GPCRs regulated by Isx. This screen identified one agonist hit, the extracellular proton/pH-sensing GPCR GPR68, confirmed through genetic gain- and loss-of-function. Overlooked until now, GPR68 expression and localization were highly regulated in early post-natal and adult post-infarct mouse heart, where GPR68-expressing cells accumulated subepicardially. Remarkably, GPR68-expressing cardiomyocytes established a proton-sensing cellular "buffer zone" surrounding the MI. Isx pharmacologically regulated gene expression (mRNAs and miRs) in this GPR68-enriched border zone, driving cardiomyogenic and pro-survival transcriptional programs in vivo. In conclusion, we tracked a (micromolar) bioactive small molecule's mechanism-of-action to a candidate target protein, GPR68, and validated this target as a previously unrecognized regulator of myocardial cellular responses to tissue acidosis, setting the stage for future (nanomolar) target-based drug lead discovery.
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Affiliation(s)
| | | | - Hector R. Aguilar
- Department
of Chemistry, University of Texas at San Antonio, San Antonio, Texas,
United States
| | | | | | | | | | - Doug E. Frantz
- Department
of Chemistry, University of Texas at San Antonio, San Antonio, Texas,
United States
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Abstract
Ion channels and G-protein-coupled receptors (GPCRs) play a fundamental role in cancer progression by influencing Ca(2+) influx and signaling pathways in transformed cells. Transformed cells thrive in a hostile environment that is characterized by extracellular acidosis that promotes the pathological phenotype. The pathway(s) by which extracellular protons achieve this remain unclear. Here, a role for proton-sensing ion channels and GPCRs as mediators of the effects of extracellular protons in cancer cells is discussed.
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Affiliation(s)
- Maike Glitsch
- Department of Physiology, Anatomy and Genetics, Oxford University, Oxford, United Kingdom.
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Chen A, Dong L, Leffler NR, Asch AS, Witte ON, Yang LV. Activation of GPR4 by acidosis increases endothelial cell adhesion through the cAMP/Epac pathway. PLoS One 2011; 6:e27586. [PMID: 22110680 PMCID: PMC3217975 DOI: 10.1371/journal.pone.0027586] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2011] [Accepted: 10/20/2011] [Indexed: 01/11/2023] Open
Abstract
Endothelium-leukocyte interaction is critical for inflammatory responses. Whereas the tissue microenvironments are often acidic at inflammatory sites, the mechanisms by which cells respond to acidosis are not well understood. Using molecular, cellular and biochemical approaches, we demonstrate that activation of GPR4, a proton-sensing G protein-coupled receptor, by isocapnic acidosis increases the adhesiveness of human umbilical vein endothelial cells (HUVECs) that express GPR4 endogenously. Acidosis in combination with GPR4 overexpression further augments HUVEC adhesion with U937 monocytes. In contrast, overexpression of a G protein signaling-defective DRY motif mutant (R115A) of GPR4 does not elicit any increase of HUVEC adhesion, indicating the requirement of G protein signaling. Downregulation of GPR4 expression by RNA interference reduces the acidosis-induced HUVEC adhesion. To delineate downstream pathways, we show that inhibition of adenylate cyclase by inhibitors, 2',5'-dideoxyadenosine (DDA) or SQ 22536, attenuates acidosis/GPR4-induced HUVEC adhesion. Consistently, treatment with a cAMP analog or a G(i) signaling inhibitor increases HUVEC adhesiveness, suggesting a role of the G(s)/cAMP signaling in this process. We further show that the cAMP downstream effector Epac is important for acidosis/GPR4-induced cell adhesion. Moreover, activation of GPR4 by acidosis increases the expression of vascular adhesion molecules E-selectin, VCAM-1 and ICAM-1, which are functionally involved in acidosis/GPR4-mediated HUVEC adhesion. Similarly, hypercapnic acidosis can also activate GPR4 to stimulate HUVEC adhesion molecule expression and adhesiveness. These results suggest that acidosis/GPR4 signaling regulates endothelial cell adhesion mainly through the G(s)/cAMP/Epac pathway and may play a role in the inflammatory response of vascular endothelial cells.
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Affiliation(s)
- Aishe Chen
- Department of Internal Medicine, Brody School of Medicine, East Carolina University, Greenville, North Carolina, United States of America
| | - Lixue Dong
- Department of Internal Medicine, Brody School of Medicine, East Carolina University, Greenville, North Carolina, United States of America
| | - Nancy R. Leffler
- Department of Internal Medicine, Brody School of Medicine, East Carolina University, Greenville, North Carolina, United States of America
| | - Adam S. Asch
- Department of Internal Medicine, Brody School of Medicine, East Carolina University, Greenville, North Carolina, United States of America
- UNC Lineberger Comprehensive Cancer Center, Chapel Hill, North Carolina, United States of America
| | - Owen N. Witte
- Howard Hughes Medical Institute, University of California Los Angeles, Los Angeles, California, United States of America
| | - Li V. Yang
- Department of Internal Medicine, Brody School of Medicine, East Carolina University, Greenville, North Carolina, United States of America
- Department of Anatomy and Cell Biology, Brody School of Medicine, East Carolina University, Greenville, North Carolina, United States of America
- UNC Lineberger Comprehensive Cancer Center, Chapel Hill, North Carolina, United States of America
- * E-mail:
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Park SY, Lee YJ, Min Y, Kim HR, Jeong JH, Sohn UD. The mechanism of MAP kinase activation under acidic condition in feline esophageal smooth muscle cells. Arch Pharm Res 2011; 34:1759-68. [PMID: 22076776 DOI: 10.1007/s12272-011-1020-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2011] [Revised: 08/02/2011] [Accepted: 08/04/2011] [Indexed: 12/21/2022]
Abstract
Reflux esophagitis results from repeated exposure of the esophagus to acidic gastric juice or bile-containing duodenal contents. In Barrett's adenocarcinoma, acid increases proliferation via ERK and p38 MAPK activation. This study was focused on determination of the mechanism(s) underlying MAPKs (ERK 1/2, p38 MAPK, and JNK) activation induced by acidic medium at pH 4 in normal feline primary cultured esophageal smooth muscle cells (FESMCs). We detected ERK 1/2 and p38 MAPK phosphorylation after exposure to pH 4 or neutral media in the presence or absence of several inhibitors and quantified the MAPK levels using western blotting analysis and densitometry. Acidic medium markedly increased the phosphorylation of ERK 1/2 and p38 MAPK within 10 min. Acid-induced ERK 1/2 and p38 MAPK activation was inhibited by pertussis toxin (PTX-sensitive G(i/o) protein inhibitor), DEDA (phospholipase (PL) A(2) inhibitor), ρCMB (PLD inhibitor), GF109203X (protein kinase C (PKC) inhibitor) and D609 (phosphatidylcholine-specific PLC inhibitor). But, genistein (tyrosine kinase inhibitor), forskolin (adenylate cyclase activator) and U73122 (phosphatidylinositol-specific PLC inhibitor) had no effect on acid-induced ERK1/2 and p38 MAPK activation. These findings indicate that the activation of ERK 1/2 and p38 MAPK pathways by acidic conditions, at least in part, may be mediated by activation of the G(i/o) protein coupled receptors, PC-PLC, PLD, PLA(2), and PKC in FESMCs.
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Affiliation(s)
- Sun Young Park
- Department of Pharmacology, College of Pharmacy, Chung-Ang University, Seoul 156-756, Korea
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79
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Reduced pathological angiogenesis and tumor growth in mice lacking GPR4, a proton sensing receptor. Angiogenesis 2011; 14:533-44. [PMID: 22045552 DOI: 10.1007/s10456-011-9238-9] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2011] [Accepted: 10/11/2011] [Indexed: 10/16/2022]
Abstract
The G protein-coupled receptor GPR4 is activated by acidic pH and recent evidence indicates that it is expressed in endothelial cells. In agreement with these reports, we observe a high correlation of GPR4 mRNA expression with endothelial marker genes, and we confirm expression and acidic pH dependent function of GPR4 in primary human vascular endothelial cells. GPR4-deficient mice were generated; these are viable and fertile and show no gross abnormalities. However, these animals show a significantly reduced angiogenic response to VEGF (vascular endothelial growth factor), but not to bFGF (basic fibroblast growth factor), in a growth factor implant model. Accordingly, in two different orthotopic models, tumor growth is strongly reduced in mice lacking GPR4. Histological analysis of tumors indicates reduced tumor cell proliferation as well as altered vessel morphology, length and density. Moreover, GPR4 deficiency results in reduced VEGFR2 (VEGF Receptor 2) levels in endothelial cells, accounting, at least in part, for the observed phenotype. Our data suggest that endothelial cells sense local tissue acidosis via GPR4 and that this signal is required to generate a full angiogenic response to VEGF.
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80
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Codina J, Opyd TS, Powell ZB, Furdui CM, Petrovic S, Penn RB, DuBose TD. pH-dependent regulation of the α-subunit of H+-K+-ATPase (HKα2). Am J Physiol Renal Physiol 2011; 301:F536-43. [PMID: 21653633 PMCID: PMC3174558 DOI: 10.1152/ajprenal.00220.2011] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2011] [Accepted: 06/03/2011] [Indexed: 11/22/2022] Open
Abstract
The H(+)-K(+)-ATPase α-subunit (HKα(2)) participates importantly in systemic acid-base homeostasis and defends against metabolic acidosis. We have previously shown that HKα(2) plasma membrane expression is regulated by PKA (Codina J, Liu J, Bleyer AJ, Penn RB, DuBose TD Jr. J Am Soc Nephrol 17: 1833-1840, 2006) and in a separate study demonstrated that genetic ablation of the proton-sensing G(s)-coupled receptor GPR4 results in spontaneous metabolic acidosis (Sun X, Yang LV, Tiegs BC, Arend LJ, McGraw DW, Penn RB, Petrovic S. J Am Soc Nephrol 21: 1745-1755, 2010). In the present study, we investigated the ability of chronic acidosis and GPR4 to regulate HKα(2) expression in HEK-293 cells. Chronic acidosis was modeled in vitro by using multiple methods: reducing media pH by adjusting bicarbonate concentration, adding HCl, or by increasing the ambient concentration of CO(2). PKA activity and HKα(2) protein were monitored by immunoblot analysis, and HKα(2) mRNA, by real-time PCR. Chronic acidosis did not alter the expression of HKα(2) mRNA; however, PKA activity and HKα(2) protein abundance increased when media pH decreased from 7.4 to 6.8. Furthermore, this increase was independent of the method used to create chronic acidosis. Heterologous expression of GPR4 was sufficient to increase both basal and acid-stimulated PKA activity and similarly increase basal and acid-stimulated HKα(2) expression. Collectively, these results suggest that chronic acidosis and GPR4 increase HKα(2) protein by increasing PKA activity without altering HKα(2) mRNA abundance, implicating a regulatory role of pH-activated GPR4 in homeostatic regulation of HKα(2) and acid-base balance.
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Affiliation(s)
- Juan Codina
- Sections on Nephrology and Molecular Medicine, Department of Internal Medicine, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA
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81
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Extracellular acidification induces connective tissue growth factor production through proton-sensing receptor OGR1 in human airway smooth muscle cells. Biochem Biophys Res Commun 2011; 413:499-503. [PMID: 21907704 DOI: 10.1016/j.bbrc.2011.08.087] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2011] [Accepted: 08/17/2011] [Indexed: 11/20/2022]
Abstract
Asthma is characterized by airway inflammation, hyper-responsiveness and remodeling. Extracellular acidification is known to be associated with severe asthma; however, the role of extracellular acidification in airway remodeling remains elusive. In the present study, the effects of acidification on the expression of connective tissue growth factor (CTGF), a critical factor involved in the formation of extracellular matrix proteins and hence airway remodeling, were examined in human airway smooth muscle cells (ASMCs). Acidic pH alone induced a substantial production of CTGF, and enhanced transforming growth factor (TGF)-β-induced CTGF mRNA and protein expression. The extracellular acidic pH-induced effects were inhibited by knockdown of a proton-sensing ovarian cancer G-protein-coupled receptor (OGR1) with its specific small interfering RNA and by addition of the G(q/11) protein-specific inhibitor, YM-254890, or the inositol-1,4,5-trisphosphate (IP(3)) receptor antagonist, 2-APB. In conclusion, extracellular acidification induces CTGF production through the OGR1/G(q/11) protein and inositol-1,4,5-trisphosphate-induced Ca(2+) mobilization in human ASMCs.
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82
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Kukkonen JP. A ménage à trois made in heaven: G-protein-coupled receptors, lipids and TRP channels. Cell Calcium 2011; 50:9-26. [DOI: 10.1016/j.ceca.2011.04.005] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2011] [Revised: 04/21/2011] [Accepted: 04/22/2011] [Indexed: 12/15/2022]
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83
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Montmayeur JP, Fenech C, Kusumakshi S, Laugerette F, Liu Z, Wiencis A, Boehm U. Screening for G-protein-coupled receptors expressed in mouse taste papillae. FLAVOUR FRAG J 2011. [DOI: 10.1002/ffj.2043] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
| | - Claire Fenech
- UMR6265 CNRS, Centre des Sciences du Goût et de l'Alimentation; 15 Rue H. Picardet; F-21000; Dijon; France
| | - Soumya Kusumakshi
- Institute for Neural Signal Transduction, Centre for Molecular Neurobiology; Falkenried 94; D-20253; Hamburg; Germany
| | - Fabienne Laugerette
- General Olfaction and Sensing Programme on a European Level, Centre des Sciences du Goût et de l'Alimentation; 15 Rue H. Picardet; F-21000; Dijon; France
| | - Zhenhui Liu
- UMR6265 CNRS, Centre des Sciences du Goût et de l'Alimentation; 15 Rue H. Picardet; F-21000; Dijon; France
| | - Anna Wiencis
- General Olfaction and Sensing Programme on a European Level, Centre des Sciences du Goût et de l'Alimentation; 15 Rue H. Picardet; F-21000; Dijon; France
| | - Ulrich Boehm
- Institute for Neural Signal Transduction, Centre for Molecular Neurobiology; Falkenried 94; D-20253; Hamburg; Germany
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84
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Connor M, Vaughan CW, Vandenberg RJ. N-acyl amino acids and N-acyl neurotransmitter conjugates: neuromodulators and probes for new drug targets. Br J Pharmacol 2010; 160:1857-71. [PMID: 20649585 DOI: 10.1111/j.1476-5381.2010.00862.x] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
The myriad functions of lipids as signalling molecules is one of the most interesting fields in contemporary pharmacology, with a host of compounds recognized as mediators of communication within and between cells. The N-acyl conjugates of amino acids and neurotransmitters (NAANs) have recently come to prominence because of their potential roles in the nervous system, vasculature and the immune system. NAAN are compounds such as glycine, GABA or dopamine conjugated with long chain fatty acids. More than 70 endogenous NAAN have been reported although their physiological role remains uncertain, with various NAAN interacting with a low affinity at G protein coupled receptors (GPCR) and ion channels. Regardless of their potential physiological function, NAAN are of great interest to pharmacologists because of their potential as flexible tools to probe new sites on GPCRs, transporters and ion channels. NAANs are amphipathic molecules, with a wide variety of potential fatty acid and headgroup moieties, a combination which provides a rich source of potential ligands engaging novel binding sites and mechanisms for modulation of membrane proteins such as GPCRs, ion channels and transporters. The unique actions of subsets of NAAN on voltage-gated calcium channels and glycine transporters indicate that the wide variety of NAAN may provide a readily exploitable resource for defining new pharmacological targets. Investigation of the physiological roles and pharmacological potential of these simple lipid conjugates is in its infancy, and we believe that there is much to be learnt from their careful study.
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Affiliation(s)
- Mark Connor
- Brain and Mind Research Institute, University of Sydney, Camperdown, NSW, Australia.
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85
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Krieger NS, Bushinsky DA. Pharmacological inhibition of intracellular calcium release blocks acid-induced bone resorption. Am J Physiol Renal Physiol 2010; 300:F91-7. [PMID: 21048027 DOI: 10.1152/ajprenal.00276.2010] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In vivo chronic metabolic acidosis induces net Ca2+ efflux from bone, and incubation of neonatal mouse calvariae in medium simulating physiological metabolic acidosis induces bone resorption. It appears that activation of the proton (H+) receptor OGR1 in the osteoblast leads to an increase in intracellular Ca2+, which is associated with an increase in cyclooxygenase 2 (COX2) and PGE2-induced receptor activator of NF-κB ligand (RANKL) and H+-induced osteoclastic bone resorption. To support this hypothesis, we tested whether intracellular Ca2+ signaling was integral to H+-induced bone resorption by determining whether 8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate (TMB-8) and 2-aminoethoxydiphenyl borate (2-APB), inhibitors of inositol trisphosphate-mediated Ca2+ signaling, would block H+-induced bone resorption in cultured neonatal calvariae and, if so, would do so by inhibiting H+-induced stimulation of COX2 and RANKL in osteoblastic cells. We found that H+-induced bone resorption is significantly inhibited by TMB-8 and 2-APB. Both compounds also inhibit H+-induced stimulation of COX2 protein in calvariae and COX2 mRNA and protein levels in primary osteoblasts. H+-induced stimulation of RANKL in calvarial cultures, as well as primary cells, is also completely inhibited by TMB-8 and 2-APB. These results support the hypothesis that H+ stimulation of net Ca2+ efflux from bone, mediated by COX2- and subsequent PGE2-induced RANKL production, is initiated in the osteoblast via activation of Ca2+ signaling.
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Affiliation(s)
- Nancy S Krieger
- University of Rochester School of Medicine and Dentistry, Division of Nephrology, Department of Medicine, 601 Elmwood Ave., Box 675, Rochester, NY 14642, USA.
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86
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Sun X, Yang LV, Tiegs BC, Arend LJ, McGraw DW, Penn RB, Petrovic S. Deletion of the pH sensor GPR4 decreases renal acid excretion. J Am Soc Nephrol 2010; 21:1745-55. [PMID: 20798260 DOI: 10.1681/asn.2009050477] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Proton receptors are G protein-coupled receptors that accept protons as ligands and function as pH sensors. One of the proton receptors, GPR4, is relatively abundant in the kidney, but its potential role in acid-base homeostasis is unknown. In this study, we examined the distribution of GPR4 in the kidney, its function in kidney epithelial cells, and the effects of its deletion on acid-base homeostasis. We observed GPR4 expression in the kidney cortex, in the outer and inner medulla, in isolated kidney collecting ducts, and in cultured outer and inner medullary collecting duct cells (mOMCD1 and mIMCD3). Cultured mOMCD1 cells exhibited pH-dependent accumulation of intracellular cAMP, characteristic of GPR4 activation; GPR4 knockdown attenuated this accumulation. In vivo, deletion of GPR4 decreased net acid secretion by the kidney and resulted in a nongap metabolic acidosis, indicating that GPR4 is required to maintain acid-base homeostasis. Collectively, these findings suggest that GPR4 is a pH sensor with an important role in regulating acid secretion in the kidney collecting duct.
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Affiliation(s)
- Xuming Sun
- Department of Medicine, University of Cincinnati, Cincinnati, OH 45267-0585, USA
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87
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Tomura H, Mogi C, Sato K, Okajima F. [Proton-sensing G-protein-coupled receptors and their physiological roles]. Nihon Yakurigaku Zasshi 2010; 135:240-4. [PMID: 20543514 DOI: 10.1254/fpj.135.240] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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88
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Samadi N, Bekele R, Capatos D, Venkatraman G, Sariahmetoglu M, Brindley DN. Regulation of lysophosphatidate signaling by autotaxin and lipid phosphate phosphatases with respect to tumor progression, angiogenesis, metastasis and chemo-resistance. Biochimie 2010; 93:61-70. [PMID: 20709140 DOI: 10.1016/j.biochi.2010.08.002] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2010] [Revised: 08/03/2010] [Accepted: 08/04/2010] [Indexed: 12/21/2022]
Abstract
Evidence from clinical, animal and cell culture studies demonstrates that increased autotaxin (ATX) expression is responsible for enhancing tumor progression, cell migration, metastases, angiogenesis and chemo-resistance. These effects depend mainly on the rapid formation of lysophosphatidate (LPA) by ATX. Circulating LPA has a half-life of about 3 min in mice and it is degraded by the ecto-activities of lipid phosphate phosphatases (LPPs). These enzymes also hydrolyze extracellular sphingosine 1-phosphate (S1P), a potent signal for cell division, survival and angiogenesis. Many aggressive tumor cells express high ATX levels and low LPP activities. This favors the formation of locally high LPA and S1P concentrations. Furthermore, LPPs attenuate signaling downstream of the activation of G-protein coupled receptors and receptor tyrosine kinases. Therefore, we propose that the low expression of LPPs in many tumor cells makes them hypersensitive to growth promoting and survival signals that are provided by LPA, S1P, platelet-derived growth factor (PDGF) and epidermal growth factor (EGF). One of the key signaling pathways in this respect appears to be activation of phospholipase D (PLD) and phosphatidate (PA) production. This is required for the transactivations of the EGFR and PDGFR and also for LPA-induced cell migration. PA also increases the activities of ERK, mTOR, myc and sphingosine kinase-1 (SK-1), which provide individual signals for cells division, survival, chemo-resistance and angiogenesis. This review focuses on the balance of signaling by bioactive lipids including LPA, phosphatidylinositol 3,4,5-trisphosphate, PA and S1P versus the action of ceramides. We will discuss how these lipid mediators interact to produce an aggressive neoplastic phenotype.
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Affiliation(s)
- Nasser Samadi
- Signal Transduction Research Group, Department of Biochemistry, School of Molecular and Systems Medicine, University of Alberta, Edmonton, T6G 2S2 Alberta, Canada
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89
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Tresguerres M, Buck J, Levin LR. Physiological carbon dioxide, bicarbonate, and pH sensing. Pflugers Arch 2010; 460:953-64. [PMID: 20683624 DOI: 10.1007/s00424-010-0865-6] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2010] [Revised: 07/16/2010] [Accepted: 07/18/2010] [Indexed: 12/20/2022]
Abstract
In biological systems, carbon dioxide exists in equilibrium with bicarbonate and protons. The individual components of this equilibrium (i.e., CO₂, HCO₃⁻, and H(+)), which must be sensed to be able to maintain cellular and organismal pH, also function as signals to modulate multiple physiological functions. Yet, the molecular sensors for CO₂/HCO₃⁻/pH remained unknown until recently. Here, we review recent progress in delineating molecular and cellular mechanisms for sensing CO₂, HCO₃⁻, and pH.
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Affiliation(s)
- Martin Tresguerres
- Department of Pharmacology, Weill Cornell Medical College, Cornell University, New York, USA
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90
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Ichimonji I, Tomura H, Mogi C, Sato K, Aoki H, Hisada T, Dobashi K, Ishizuka T, Mori M, Okajima F. Extracellular acidification stimulates IL-6 production and Ca(2+) mobilization through proton-sensing OGR1 receptors in human airway smooth muscle cells. Am J Physiol Lung Cell Mol Physiol 2010; 299:L567-77. [PMID: 20656891 DOI: 10.1152/ajplung.00415.2009] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The asthmatic airway has been shown to be an acidic environment that may be involved in the pathophysiological features of asthma. However, the mechanism by which an acidic pH modulates the cellular activities involved in the asthmatic airway remains elusive. Here, we characterized acidic pH-induced actions in human airway smooth muscle cells (ASMCs). Extracellular acidification stimulates the mRNA expression and protein production of IL-6, a proinflammatory cytokine, in association with the phosphorylation of extracellular signal-regulated kinase (ERK) and p38MAPK, reflecting the activation of the enzymes. Acidification-induced cytokine production was inhibited by inhibitors of ERK and p38MAPK. Acidification also increased intracellular Ca(2+) concentration, which was accompanied by cell rounding, most likely reflecting contraction. In ASMCs, OGR1 is expressed at by far the highest levels among proton-sensing G protein-coupled receptors. The knockdown of OGR1 and G(q/11) protein with their specific small interfering RNAs and an inhibition of G(q/11) protein with YM-254890 attenuated the acidification-induced actions. We conclude that extracellular acidification stimulates IL-6 production and Ca(2+) mobilization through proton-sensing OGR1 receptors/G(q/11) proteins in human ASMCs.
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Affiliation(s)
- Isao Ichimonji
- Institute for Molecular and Cellular Regulation, Gunma Univ., Maebashi, Japan
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91
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Liu JP, Nakakura T, Tomura H, Tobo M, Mogi C, Wang JQ, He XD, Takano M, Damirin A, Komachi M, Sato K, Okajima F. Each one of certain histidine residues in G-protein-coupled receptor GPR4 is critical for extracellular proton-induced stimulation of multiple G-protein-signaling pathways. Pharmacol Res 2010; 61:499-505. [PMID: 20211729 DOI: 10.1016/j.phrs.2010.02.013] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/22/2009] [Revised: 02/11/2010] [Accepted: 02/13/2010] [Indexed: 01/11/2023]
Abstract
GPR4, previously proposed as the receptor for sphingosylphosphorylcholine, has recently been identified as the proton-sensing G-protein-coupled receptor coupling to multiple intracellular signaling pathways, including the G(s)-protein/cAMP, G(12/13)-protein/Rho, and G(q)-protein/phospholipase C pathways. In the present study, we examined whether extracellularly located histidine residues of GPR4 sense extracellular protons and, if so, whether a certain histidine residue is critical for coupling to the single or multiple signaling pathway(s). We found that the mutation of histidine residue at 79, 165, or 269 from the N-terminal of GPR4 to phenylalanine shifted the half-maximal effective concentration (EC(50)) of proton-induced signaling activities to the right, including cAMP accumulation, SRE promoter activity reflecting Rho activity, and NFAT promoter activity reflecting phospholipase C signaling activity, without an appreciable change in the maximal activities. These results suggest that the protonation of each one of histidine residues at 79, 165, and 269 in GPR4 may be critical for conformational change of the receptor for coupling to multiple intracellular signaling pathways through G-proteins.
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Affiliation(s)
- Jin-Peng Liu
- 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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92
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Păunescu TG, Ljubojevic M, Russo LM, Winter C, McLaughlin MM, Wagner CA, Breton S, Brown D. cAMP stimulates apical V-ATPase accumulation, microvillar elongation, and proton extrusion in kidney collecting duct A-intercalated cells. Am J Physiol Renal Physiol 2010; 298:F643-54. [PMID: 20053793 DOI: 10.1152/ajprenal.00584.2009] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Kidney proton-secreting A-intercalated cells (A-IC) respond to systemic acidosis by accumulating the vacuolar ATPase (V-ATPase) in their apical membrane and by increasing the length and number of apical microvilli. We show here that the cell-permeant cAMP analog CPT-cAMP, infused in vivo, results in an almost twofold increase in apical V-ATPase accumulation in AE1-positive A-IC within 15 min and that these cells develop an extensive array of apical microvilli compared with controls. In contrast, no significant change in V-ATPase distribution could be detected by immunocytochemistry in B-intercalated cells at the acute time point examined. To show a direct effect of cAMP on A-IC, we prepared cell suspensions from the medulla of transgenic mice expressing EGFP in IC (driven by the B1-subunit promoter of the V-ATPase) and exposed them to cAMP analogs in vitro. Three-dimensional reconstructions of confocal images revealed that cAMP induced a time-dependent growth of apical microvilli, starting within minutes after addition. This effect was blocked by the PKA inhibitor myristoylated PKI. These morphological changes were paralleled by increased cAMP-mediated proton extrusion (pHi recovery) by A-IC in outer medullary collecting ducts measured using the ratiometric probe BCECF. These results, and our prior data showing that the bicarbonate-stimulated soluble adenylyl cyclase (sAC) is highly expressed in kidney intercalated cells, support the idea that cAMP generated either by sAC, or by activation of other signaling pathways, is part of the signal transduction mechanism involved in acid-base sensing and V-ATPase membrane trafficking in kidney intercalated cells.
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Affiliation(s)
- Teodor G Păunescu
- MGH Center for Systems Biology, Program in Membrane Biology, and Division of Nephrology, Massachusetts General Hospital, and Harvard Medical School, Boston, Massachusetts 02114, USA
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93
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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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94
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Schilling T, Eder C. Non-selective cation channel activity is required for lysophosphatidylcholine-induced monocyte migration. J Cell Physiol 2009; 221:325-34. [DOI: 10.1002/jcp.21857] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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95
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Gaetano CG, Samadi N, Tomsig JL, Macdonald TL, Lynch KR, Brindley DN. Inhibition of autotaxin production or activity blocks lysophosphatidylcholine-induced migration of human breast cancer and melanoma cells. Mol Carcinog 2009; 48:801-9. [PMID: 19204929 DOI: 10.1002/mc.20524] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Increased expression of autotaxin in tumors including glioblastoma, breast, renal, ovarian, lung, and thyroid cancers is associated with increased tumor aggressiveness. Autotaxin promotes metastasis as well as cell growth, survival, and migration of cancer cells. These actions could depend on the noncatalytic effects of autotaxin on cell adhesion, or the catalytic activity of autotaxin, which converts lysophosphatidylcholine into lysophosphatidate in the extracellular fluid surrounding the tumor. Both lysophosphatidylcholine (LPC) and lysophosphatidate have been reported to stimulate migration through their respective G-protein coupled receptors. The present study determines the roles of autotaxin, LPC, and lysophosphatidate in controlling the migration of two cancer cell lines: MDA-MB-231 breast cancer cells, which produce little autotaxin and MDA-MB-435 melanoma cells that secrete significant levels of autotaxin. LPC alone was unable to stimulate the migration of either cell type unless autotaxin was present. Knocking down autotaxin secretion, or inhibiting its catalytic activity, blocked cell migration by preventing lysophosphatidate production and the subsequent activation of LPA(1/3) receptors. We conclude that inhibiting autotaxin production or activity could provide a beneficial adjuvant to chemotherapy for preventing tumor growth and metastasis in patients with high autotaxin expression in their tumors.
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Affiliation(s)
- Cristoforo G Gaetano
- Department of Biochemistry, Signal Transduction Research Group, University of Alberta, Edmonton, Alberta, Canada T6G 2S2
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96
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Im DS. New intercellular lipid mediators and their GPCRs: An update. Prostaglandins Other Lipid Mediat 2009; 89:53-6. [DOI: 10.1016/j.prostaglandins.2009.01.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2008] [Revised: 01/24/2009] [Accepted: 01/25/2009] [Indexed: 01/08/2023]
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97
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Gloriam DE, Foord SM, Blaney FE, Garland SL. Definition of the G protein-coupled receptor transmembrane bundle binding pocket and calculation of receptor similarities for drug design. J Med Chem 2009; 52:4429-42. [PMID: 19537715 DOI: 10.1021/jm900319e] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Recent advances in structural biology for G-protein-coupled receptors (GPCRs) have provided new opportunities to improve the definition of the transmembrane binding pocket. Here a reference set of 44 residue positions accessible for ligand binding was defined through detailed analysis of all currently available crystal structures. This was used to characterize pharmacological relationships of Family A/Rhodopsin family GPCRs, minimizing evolutionary influence from parts of the receptor that do not generally affect ligand binding. The resultant dendogram tended to group receptors according to endogenous ligand types, although it revealed subdivision of certain classes, notably peptide and lipid receptors. The transmembrane binding site reference set, particularly when coupled with a means of identifying the subset of ligand binding residues, provides a general paradigm for understanding the pharmacology/selectivity profile of ligands at Family A GPCRs. This has wide applicability to GPCR drug design problems across many disease areas.
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Affiliation(s)
- David E Gloriam
- Department of Medicinal Chemistry, Pharmaceutical Faculty, Copenhagen University, Universitetsparken 2, 2100 Copenhagen, Denmark.
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98
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McGuire J, Herman JP, Ghosal S, Eaton K, Sallee FR, Sah R. Acid-sensing by the T cell death-associated gene 8 (TDAG8) receptor cloned from rat brain. Biochem Biophys Res Commun 2009; 386:420-5. [PMID: 19501050 DOI: 10.1016/j.bbrc.2009.05.133] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2009] [Accepted: 05/31/2009] [Indexed: 10/20/2022]
Abstract
The T cell death-associated gene 8 (TDAG8) is a pH-sensing GPCR with a reported immune-specific expression profile. Here, we demonstrate pH-induced activation of TDAG8 receptor cloned from rodent brain (rTDAG8). Cloned rTDAG8 transcript showed 88-95% homology with human and mouse transcripts of lymphoid origin. RT-PCR revealed high expression of TDAG8 in forebrain limbic regions. Extracellular acidification induced significantly elevated intracellular cyclic AMP, and phosphorylated CREB in TDAG8 expressing cells. Acidification-induced LDH release was significantly attenuated in cells expressing TDAG8, suggesting neuroprotective potential against acidosis-related cell injury. Our results open up new areas of investigation into the relevance of TDAG8 in pH homeostasis and pathological states associated with acid-base dys-regulation in the brain such as ischemia and panic disorder.
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Affiliation(s)
- Jennifer McGuire
- Department of Psychiatry, University of Cincinnati, Genome Research Institute, 2170 East Galbraith Road, Cincinnati, OH 45237, USA
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99
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Murata N, Mogi C, Tobo M, Nakakura T, Sato K, Tomura H, Okajima F. Inhibition of superoxide anion production by extracellular acidification in neutrophils. Cell Immunol 2009; 259:21-6. [PMID: 19539899 DOI: 10.1016/j.cellimm.2009.05.008] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2009] [Revised: 05/15/2009] [Accepted: 05/18/2009] [Indexed: 01/23/2023]
Abstract
Extracellular acidification inhibited formyl-Met-Leu-Phe- or C5a-induced superoxide anion (O(2)(-)) production in differentiated HL-60 neutrophil-like cells and human neutrophils. A cAMP-increasing agonist, prostaglandin E(1), also inhibited the formyl peptide-induced O(2)(-) production. The inhibitory action on the O(2)(-) production by extracellular acidic pH was associated with cAMP accumulation and partly attenuated by H89, a protein kinase A inhibitor. A significant amount of mRNAs for T-cell death-associated gene 8 (TDAG8) and other proton-sensing ovarian cancer G-protein-coupled receptor 1 (OGR1)-family receptors is expressed in these cells. These results suggest that cAMP/protein kinase A, possibly through proton-sensing G-protein-coupled receptors, may be involved in extracellular acidic pH-induced inhibition of O(2)(-) production.
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Affiliation(s)
- Naoya Murata
- Laboratory of Signal Transduction, Institute for Molecular and Cellular Regulation Gunma University, Showa-machi, Maebashi, Japan
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100
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Stock C, Schwab A. Protons make tumor cells move like clockwork. Pflugers Arch 2009; 458:981-92. [PMID: 19437033 DOI: 10.1007/s00424-009-0677-8] [Citation(s) in RCA: 181] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2009] [Accepted: 04/28/2009] [Indexed: 01/10/2023]
Abstract
Cancer accounts for 13% of the yearly total mortality worldwide. Most cancer deaths are the sequel of metastatic diseases rather than of primary tumor growth. Thus, the major challenge in tumor therapy is the tumor cells' ability to metastasize. The extent to which a tumor metastasizes correlates with the tumor cells' migratory activity. Tumor cell migration requires a coordinated formation and release of cell adhesion contacts, a controlled cytoskeletal dynamics, the digestion and reorganization of the extracellular matrix, and local ion and water transport across the plasma membrane. All of these operations depend on intracellular pH (pH(i)) and extracellular pH (pH(e)). Numerous H(+), HCO (3) (-) , and monocarboxylate transporters as well as different carbonic anhydrase isozymes have considerable impact on pH(i) and pH(e) which spotlights them as possible, potential targets for anticancer therapeutics. Especially in solid tumors whose vascularization is often not sufficient, tumor cells cope with hypoxia and the resulting glycolysis by overexpressing the Na(+)/H(+) exchanger NHE1, monocarboxylate transporters MCT1 and/or MCT4, and the carbonic anhydrase CA IX. NHE1, MCT, and CA IX activity lead to an acidification of the extracellular space in order to maintain the cytosolic pH homeostasis stable. The present article gives a review on how this characteristic, acidic tumor micro- and nanoenvironment controls tumor cell migration.
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Affiliation(s)
- Christian Stock
- Institut für Physiologie II, University of Münster, Robert-Koch-Str. 27b, 48149, Münster, Germany.
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