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Li MS, Wang XH, Wang H. Immunomodulation of Proton-activated G Protein-coupled Receptors in Inflammation. Curr Med Sci 2024; 44:475-484. [PMID: 38748372 DOI: 10.1007/s11596-024-2872-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2023] [Accepted: 03/22/2024] [Indexed: 06/29/2024]
Abstract
Proton-activated G protein-coupled receptors (GPCRs), initially discovered by Ludwig in 2003, are widely distributed in various tissues. These receptors have been found to modulate the immune system in several inflammatory diseases, including inflammatory bowel disease, atopic dermatitis, and asthma. Proton-activated GPCRs belong to the G protein-coupled receptor family and can detect alternations in extracellular pH. This detection triggers downstream signaling pathways within the cells, ultimately influencing the function of immune cells. In this review, we specifically focused on investigating the immune response of proton-activated GPCRs under inflammatory conditions.
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Affiliation(s)
- Min-Shan Li
- Department of Otolaryngology-Head and Neck Surgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
- Institute of Allergy and Clinical Immunology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
- Hubei Clinical Research Center for Nasal Inflammatory Diseases, Wuhan, 430030, China
| | - Xiang-Hong Wang
- Department of Otolaryngology-Head and Neck Surgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
- Institute of Allergy and Clinical Immunology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
- Hubei Clinical Research Center for Nasal Inflammatory Diseases, Wuhan, 430030, China
| | - Heng Wang
- Department of Otolaryngology-Head and Neck Surgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China.
- Institute of Allergy and Clinical Immunology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China.
- Hubei Clinical Research Center for Nasal Inflammatory Diseases, Wuhan, 430030, China.
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2
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Gonye EC, Dagli AV, Kumar NN, Clements RT, Xu W, Bayliss DA. Expression of endogenous epitope-tagged GPR4 in the mouse brain. eNeuro 2024; 11:ENEURO.0002-24.2024. [PMID: 38408869 DOI: 10.1523/eneuro.0002-24.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2024] [Revised: 02/13/2024] [Accepted: 02/17/2024] [Indexed: 02/28/2024] Open
Abstract
GPR4 is a proton-sensing G protein-coupled receptor implicated in many peripheral and central physiological processes. GPR4 expression has previously been assessed only via detection of the cognate transcript or indirectly, by use of fluorescent reporters. In this work, CRISPR/Cas9 knock-in technology was used to encode a hemagglutinin (HA) epitope tag within the endogenous locus of Gpr4 and visualize GPR4-HA in the mouse central nervous system using a specific, well characterized HA antibody; GPR4 expression was further verified by complementary Gpr4 mRNA detection. HA immunoreactivity was found in a limited set of brain regions, including in the retrotrapezoid nucleus (RTN), serotonergic raphe nuclei, medial habenula, lateral septum, and several thalamic nuclei. GPR4 expression was not restricted to cells of a specific neurochemical identity as it was observed in excitatory, inhibitory, and aminergic neuronal cell groups. HA immunoreactivity was not detected in brain vascular endothelium, despite clear expression of Gpr4 mRNA in endothelial cells. In the RTN, GPR4 expression was detected at the soma and in proximal dendrites along blood vessels and the ventral surface of the brainstem; HA immunoreactivity was not detected in RTN projections to two known target regions. This localization of GPR4 protein in mouse brain neurons corroborates putative sites of expression where its function has been previously implicated (e.g., CO2-regulated breathing by RTN), and provides a guide for where GPR4 could contribute to other CO2/H+ modulated brain functions. Finally, GPR4-HA animals provide a useful reagent for further study of GPR4 in other physiological processes outside of the brain.Significance Statement GPR4 is a proton-sensing G-protein coupled receptor whose expression is necessary for a number of diverse physiological processes including acid-base sensing in the kidney, immune function, and cancer progression. In the brain, GPR4 has been implicated in the hypercapnic ventilatory response mediated by brainstem neurons. While knockout studies in animals have clearly demonstrated its necessity for normal physiology, descriptions of GPR4 expression have been limited due to a lack of specific antibodies for use in mouse models. In this paper, we implemented a CRISPR/Cas9 knock-in approach to incorporate the coding sequence for a small epitope tag into the locus of GPR4. Using these mice, we were able to describe GPR4 protein expression directly for the first time.
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Affiliation(s)
- Elizabeth C Gonye
- University of Virginia, Department of Pharmacology, Charlottesville, VA, USA
| | - Alexandra V Dagli
- University of Virginia, Department of Pharmacology, Charlottesville, VA, USA
| | - Natasha N Kumar
- University of New South Wales Sydney, School of Biomedical Sciences, New South Wales, Australia
| | - Rachel T Clements
- University of Virginia, Department of Pharmacology, Charlottesville, VA, USA
| | - Wenhao Xu
- University of Virginia, Genetically Engineered Mouse Model Core, Charlottesville, VA, USA
| | - Douglas A Bayliss
- University of Virginia, Department of Pharmacology, Charlottesville, VA, USA
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3
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Xu L, Niu X, Li X, Zheng Y, Feng H, Fu Q, Zhou Y. Effects of nitrogen addition and root fungal inoculation on the seedling growth and rhizosphere soil microbial community of Pinus tabulaeformis. Front Microbiol 2022; 13:1013023. [PMID: 36338078 PMCID: PMC9626767 DOI: 10.3389/fmicb.2022.1013023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2022] [Accepted: 10/04/2022] [Indexed: 11/13/2022] Open
Abstract
Nitrogen (N) availability is significant in different ecosystems, but the response of forest plant-microbial symbionts to global N deposition remains largely unexplored. In this study, the effects of different N concentration levels on four types of fungi, Suillus granulatus (Sg), Pisolithus tinctorius (Pt), Pleotrichocladium opacum (Po), and Pseudopyrenochaeta sp. (Ps), isolated from the roots of Pinus tabulaeformis were investigated in vitro. Then, the effects of the fungi on the growth performance, nutrient uptake, and rhizosphere soil microbial community structure of P. tabulaeformis under different N addition conditions (0, 40, and 80 kg hm−2 year−1) were examined. The biomass and phytohormone contents of the Sg, Pt and Po strains increased with increasing N concentration, while those of the Ps strain first increased and then decreased. All four fungal strains could effectively colonize the plant roots and form a strain-dependent symbiosis with P. tabulaeformis. Although the effects depended on the fungal species, the growth and root development of inoculated seedlings were higher than those of uninoculated seedlings under N deficiency and normal N supply conditions. However, these positive effects disappeared and even became negative under high N supply conditions. The inoculation of the four fungal strains also showed significant positive effects on the shoot and root nutrient contents of P. tabulaeformis. Fungal inoculation significantly increased different microbial groups and the total soil microorganisms but decreased the microbial diversity under N deficiency stress. In summary, exogenous symbiotic fungal inoculations could increase the growth performance of P. tabulaeformis under N deficiency and normal N supply conditions, but the effects were negative under excessive N addition.
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Affiliation(s)
- Lingjie Xu
- Country College of Landscape Architecture and Tourism, Hebei Agricultural University, Baoding, China
| | - Xiaoyun Niu
- Country College of Landscape Architecture and Tourism, Hebei Agricultural University, Baoding, China
| | - Xia Li
- School of Life Sciences, Hebei University, Baoding, China
| | - Yanyan Zheng
- Country College of Landscape Architecture and Tourism, Hebei Agricultural University, Baoding, China
| | - Hualei Feng
- Country College of Landscape Architecture and Tourism, Hebei Agricultural University, Baoding, China
| | - Qiang Fu
- Country College of Landscape Architecture and Tourism, Hebei Agricultural University, Baoding, China
| | - Yong Zhou
- Country College of Landscape Architecture and Tourism, Hebei Agricultural University, Baoding, China
- *Correspondence: Yong Zhou,
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4
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Imenez Silva PH, Câmara NO, Wagner CA. Role of proton-activated G protein-coupled receptors in pathophysiology. Am J Physiol Cell Physiol 2022; 323:C400-C414. [PMID: 35759438 DOI: 10.1152/ajpcell.00114.2022] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Local acidification is a common feature of many disease processes such as inflammation, infarction, or solid tumor growth. Acidic pH is not merely a sequelae of disease but contributes to recruitment and regulation of immune cells, modifies metabolism of parenchymal, immune and tumor cells, modulates fibrosis, vascular permeability, oxygen availability and consumption, invasiveness of tumor cells, and impacts on cell survival. Thus, multiple pH-sensing mechanisms must exist in cells involved in these processes. These pH-sensors play important roles in normal physiology and pathophysiology, and hence might be attractive targets for pharmacological interventions. Among the pH-sensing mechanisms, OGR1 (GPR68), GPR4 (GPR4), and TDAG8 (GPR65) have emerged as important molecules. These G protein-coupled receptors are widely expressed, are upregulated in inflammation and tumors, sense changes in extracellular pH in the range between pH 8 and 6, and are involved in modulating key processes in inflammation, tumor biology, and fibrosis. This review discusses key features of these receptors and highlights important disease states and pathways affected by their activity.
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Affiliation(s)
- Pedro H Imenez Silva
- Institute of Physiology, University of Zurich, Zurich, Switzerland.,National Center of Competence in Research NCCR Kidney.CH, Switzerland
| | - Niels Olsen Câmara
- Department of Immunology, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil
| | - Carsten A Wagner
- Institute of Physiology, University of Zurich, Zurich, Switzerland.,National Center of Competence in Research NCCR Kidney.CH, Switzerland
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5
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Li R, Guan Z, Bi S, Wang F, He L, Niu X, You Y, Liu Y, Ding Y, Siwko S, Wang N, Zhang Z, Jin Y, Luo J. The proton-activated G protein-coupled receptor GPR4 regulates the development of osteoarthritis via modulating CXCL12/CXCR7 signaling. Cell Death Dis 2022; 13:152. [PMID: 35165253 PMCID: PMC8844071 DOI: 10.1038/s41419-021-04455-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Revised: 11/17/2021] [Accepted: 11/29/2021] [Indexed: 12/11/2022]
Abstract
Inflammatory diseases decrease the extracellular environmental pH. However, whether proton-activated G protein-coupled receptors (GPCRs) can regulate the development of osteoarthritis (OA) is largely unknown. In this study, we report that proton-activated GPR4 is essential for OA development. We found a marked increase in expression of the proton-activated GPR4 in human and mouse OA cartilage. Lentivirus-mediated overexpression of GPR4 in mouse joints accelerated the development of OA, including promotion of articular cartilage damage, synovial hyperplasia, and osteophyte formation, while Gpr4 knockout effectively attenuated the development of posttraumatic and aging-associated OA in mice. We also found that inhibition of GPR4 with the antagonist NE52-QQ57 ameliorated OA progression in mice, promoted extracellular matrix (ECM) production, and protected cartilage from degradation in human articular cartilage explants. Moreover, GPR4 overexpression upregulated matrix-degrading enzymes’ expression and inflammation factors under pro-inflammatory and slightly acidic conditions. Mechanistically, GPR4 suppressed chondrocyte differentiation and upregulated cartilage homeostasis through NF-κB/MAPK signaling activation by regulating CXCR7/CXCL12 expression. Together, our results take the lead to illustrate that proton-activated GPCR acts as a key regulator for OA pathogenesis in vivo, and support that GPR4 could be a promising therapeutic target for OA treatment.
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Affiliation(s)
- Rong Li
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai, 200241, PR China
| | - Zijing Guan
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai, 200241, PR China
| | - Shuyan Bi
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai, 200241, PR China
| | - Fanhua Wang
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai, 200241, PR China.,Yangzhi Rehabilitation Hospital (Shanghai Sunshine Rehabilitation Center), Tongji University School of Medicine, Shanghai, 201619, PR China
| | - Liang He
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai, 200241, PR China.,Yangzhi Rehabilitation Hospital (Shanghai Sunshine Rehabilitation Center), Tongji University School of Medicine, Shanghai, 201619, PR China
| | - Xin Niu
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai, 200241, PR China
| | - Yu You
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai, 200241, PR China
| | - Yuwei Liu
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai, 200241, PR China
| | - Yi Ding
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai, 200241, PR China
| | - Stefan Siwko
- Department of Translational Medical Sciences, Institute of Biosciences and Technology, Texas A&M University Health Science Center, Houston, TX, 77030, USA
| | - Ning Wang
- Department of Oncology and Metabolism, The University of Sheffield, Sheffield, UK
| | - Ziming Zhang
- Department of Pediatric Orthopedics, Xinhua Hospital, School of Medicine, Shanghai Jiaotong University, Shanghai, 200092, PR China.
| | - Yunyun Jin
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai, 200241, PR China.
| | - Jian Luo
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai, 200241, PR China. .,Yangzhi Rehabilitation Hospital (Shanghai Sunshine Rehabilitation Center), Tongji University School of Medicine, Shanghai, 201619, PR China.
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6
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Yang LV, Oppelt KA, Thomassen MJ, Marie MA, Nik Akhtar S, McCallen JD. Can GPR4 Be a Potential Therapeutic Target for COVID-19? Front Med (Lausanne) 2021; 7:626796. [PMID: 33553219 PMCID: PMC7859652 DOI: 10.3389/fmed.2020.626796] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Accepted: 12/30/2020] [Indexed: 01/08/2023] Open
Abstract
Coronavirus disease 19 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), first emerged in late 2019 and has since rapidly become a global pandemic. SARS-CoV-2 infection causes damages to the lung and other organs. The clinical manifestations of COVID-19 range widely from asymptomatic infection, mild respiratory illness to severe pneumonia with respiratory failure and death. Autopsy studies demonstrate that diffuse alveolar damage, inflammatory cell infiltration, edema, proteinaceous exudates, and vascular thromboembolism in the lung as well as extrapulmonary injuries in other organs represent key pathological findings. Herein, we hypothesize that GPR4 plays an integral role in COVID-19 pathophysiology and is a potential therapeutic target for the treatment of COVID-19. GPR4 is a pro-inflammatory G protein-coupled receptor (GPCR) highly expressed in vascular endothelial cells and serves as a "gatekeeper" to regulate endothelium-blood cell interaction and leukocyte infiltration. GPR4 also regulates vascular permeability and tissue edema under inflammatory conditions. Therefore, we hypothesize that GPR4 antagonism can potentially be exploited to mitigate the hyper-inflammatory response, vessel hyper-permeability, pulmonary edema, exudate formation, vascular thromboembolism and tissue injury associated with COVID-19.
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Affiliation(s)
- Li V. Yang
- Department of Internal Medicine, Brody School of Medicine, East Carolina University, Greenville, NC, United States
- Department of Anatomy and Cell Biology, Brody School of Medicine, East Carolina University, Greenville, NC, United States
| | - Karen A. Oppelt
- Department of Comparative Medicine, Brody School of Medicine, East Carolina University, Greenville, NC, United States
| | - Mary Jane Thomassen
- Department of Internal Medicine, Brody School of Medicine, East Carolina University, Greenville, NC, United States
| | - Mona A. Marie
- Department of Internal Medicine, Brody School of Medicine, East Carolina University, Greenville, NC, United States
| | - Shayan Nik Akhtar
- Department of Anatomy and Cell Biology, Brody School of Medicine, East Carolina University, Greenville, NC, United States
| | - Justin D. McCallen
- Department of Internal Medicine, Brody School of Medicine, East Carolina University, Greenville, NC, United States
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7
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Comprehensive Assessment of GPR68 Expression in Normal and Neoplastic Human Tissues Using a Novel Rabbit Monoclonal Antibody. Int J Mol Sci 2019; 20:ijms20215261. [PMID: 31652823 PMCID: PMC6862545 DOI: 10.3390/ijms20215261] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2019] [Revised: 10/17/2019] [Accepted: 10/22/2019] [Indexed: 02/07/2023] Open
Abstract
GPR68 (OGR1) belongs to the proton-sensing G protein-coupled receptors that are involved in cellular adaptations to pH changes during tumour development. Although expression of GPR68 has been described in many tumour cell lines, little is known about its presence in human tumour entities. We characterised the novel rabbit monoclonal anti-human GPR68 antibody 16H23L16 using various cell lines and tissue specimens. The antibody was then applied to a large series of formalin-fixed, paraffin-embedded normal and neoplastic human tissue samples. Antibody specificity was demonstrated in a Western blot analysis of GPR68-expressing cells using specific siRNAs. Immunocytochemical experiments revealed pH-dependent changes in subcellular localisation of the receptor and internalisation after stimulation with lorazepam. In normal tissue, GPR68 was present in glucagon-producing islet cells, neuroendocrine cells of the intestinal tract, gastric glands, granulocytes, macrophages, muscle layers of arteries and arterioles, and capillaries. GPR68 was also expressed in neuroendocrine tumours, where it may be a positive prognostic factor, in pheochromocytomas, cervical adenocarcinomas, and endometrial cancer, as well as in paragangliomas, medullary thyroid carcinomas, gastrointestinal stromal tumours, and pancreatic adenocarcinomas. Often, tumour capillaries were also strongly GPR68-positive. The novel antibody 16H23L16 will be a valuable tool for basic research and for identifying GPR68-expressing tumours during histopathological examinations.
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8
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Rajkumar P, Pluznick JL. Unsung renal receptors: orphan G-protein-coupled receptors play essential roles in renal development and homeostasis. Acta Physiol (Oxf) 2017; 220:189-200. [PMID: 27699982 DOI: 10.1111/apha.12813] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Revised: 09/23/2016] [Accepted: 09/29/2016] [Indexed: 12/31/2022]
Abstract
Recent studies have shown that orphan GPCRs of the GPR family are utilized as specialized chemosensors in various tissues to detect metabolites, and in turn to activate downstream pathways which regulate systemic homeostasis. These studies often find that such metabolites are generated by well-known metabolic pathways, implying that known metabolites and chemicals may perform novel functions. In this review, we summarize recent findings highlighting the role of deorphanized GPRs in renal development and function. Understanding the role of these receptors is critical in gaining insights into mechanisms that regulate renal function both in health and in disease.
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Affiliation(s)
- P. Rajkumar
- Department of Physiology; Johns Hopkins School of Medicine; Baltimore; MD USA
| | - J. L. Pluznick
- Department of Physiology; Johns Hopkins School of Medicine; Baltimore; MD USA
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9
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Sanderlin EJ, Leffler NR, Lertpiriyapong K, Cai Q, Hong H, Bakthavatchalu V, Fox JG, Oswald JZ, Justus CR, Krewson EA, O'Rourke D, Yang LV. GPR4 deficiency alleviates intestinal inflammation in a mouse model of acute experimental colitis. Biochim Biophys Acta Mol Basis Dis 2016; 1863:569-584. [PMID: 27940273 DOI: 10.1016/j.bbadis.2016.12.005] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Revised: 11/13/2016] [Accepted: 12/06/2016] [Indexed: 02/07/2023]
Abstract
GPR4 is a proton-sensing G protein-coupled receptor that can be activated by extracellular acidosis. It has recently been demonstrated that activation of GPR4 by acidosis increases the expression of numerous inflammatory and stress response genes in vascular endothelial cells (ECs) and also augments EC-leukocyte adhesion. Inhibition of GPR4 by siRNA or small molecule inhibitors reduces endothelial cell inflammation. As acidotic tissue microenvironments exist in many types of inflammatory disorders, including inflammatory bowel disease (IBD), we examined the role of GPR4 in intestinal inflammation using a dextran sulfate sodium (DSS)-induced acute colitis mouse model. We observed that GPR4 mRNA expression was increased in mouse and human IBD tissues when compared to control intestinal tissues. To determine the function of GPR4 in intestinal inflammation, wild-type and GPR4-deficient mice were treated with 3% DSS for 7days to induce acute colitis. Our results showed that the severity of colitis was decreased in GPR4-deficient DSS-treated mice in comparison to wild-type DSS-treated mice. Clinical parameters, macroscopic disease indicators, and histopathological features were less severe in the DSS-treated GPR4-deficient mice than the DSS-treated wild-type mice. Endothelial adhesion molecule expression, leukocyte infiltration, and isolated lymphoid follicle (ILF) formation were reduced in intestinal tissues of DSS-treated GPR4-null mice. Collectively, our results suggest GPR4 provides a pro-inflammatory role in the inflamed gut as the absence of GPR4 ameliorates intestinal inflammation in the acute experimental colitis mouse model.
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Affiliation(s)
- Edward J Sanderlin
- Department of Internal Medicine, Brody School of Medicine, East Carolina University, USA
| | - Nancy R Leffler
- Department of Internal Medicine, Brody School of Medicine, East Carolina University, USA
| | - Kvin Lertpiriyapong
- Department of Comparative Medicine, Brody School of Medicine, East Carolina University, USA
| | - Qi Cai
- Department of Pathology, Brody School of Medicine, East Carolina University, USA
| | - Heng Hong
- Department of Pathology, Brody School of Medicine, East Carolina University, USA
| | | | - James G Fox
- Division of Comparative Medicine, Massachusetts Institute of Technology, USA
| | - Joani Zary Oswald
- Department of Anatomy and Cell Biology, Brody School of Medicine, East Carolina University, USA
| | - Calvin R Justus
- Department of Internal Medicine, Brody School of Medicine, East Carolina University, USA
| | - Elizabeth A Krewson
- Department of Anatomy and Cell Biology, Brody School of Medicine, East Carolina University, USA
| | - Dorcas O'Rourke
- Department of Comparative Medicine, Brody School of Medicine, East Carolina University, USA
| | - Li V Yang
- Department of Internal Medicine, Brody School of Medicine, East Carolina University, USA; Department of Anatomy and Cell Biology, Brody School of Medicine, East Carolina University, USA.
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10
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Böhme I, Bosserhoff AK. Acidic tumor microenvironment in human melanoma. Pigment Cell Melanoma Res 2016; 29:508-23. [PMID: 27233233 DOI: 10.1111/pcmr.12495] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Accepted: 05/25/2016] [Indexed: 12/18/2022]
Abstract
One characteristic of solid tumors such as malignant melanoma is the acidification of the tumor microenvironment. The deregulation of cancer cell metabolism is considered a main cause of extracellular acidosis. Here, cancer cells utilize aerobic glycolysis instead of oxidative phosphorylation even under normoxic conditions, as originally described by Otto Warburg. These metabolic alterations cause enhanced acid production, especially of lactate and carbon dioxide (CO2 ). The extensive production of acidic metabolites and the enhanced acid export to the extracellular space cause a consistent acidification of the tumor microenvironment, thus promoting the formation of an acid-resistant tumor cell population with increased invasive and metastatic potential. As melanoma is one of the deadliest and most metastatic forms of cancer, understanding the effects of this extracellular acidosis on human melanoma cells with distinct metastatic properties is important. The aim of this review was to summarize recent studies of the acidification of the tumor microenvironment, focusing on the specific effects of the acidic milieu on melanoma cells and to give a short overview of therapeutic approaches.
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Affiliation(s)
- Ines Böhme
- Institute of Biochemistry, Emil-Fischer-Centrum, Friedrich Alexander University Erlangen-Nürnberg, Erlangen-Nürnberg, Germany
| | - Anja Katrin Bosserhoff
- Institute of Biochemistry, Emil-Fischer-Centrum, Friedrich Alexander University Erlangen-Nürnberg, Erlangen-Nürnberg, Germany. .,Comprehensive Cancer Center Erlangen-EMN, University of Erlangen, Erlangen, Germany.
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11
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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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12
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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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13
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Busch T, Armacki M, Eiseler T, Joodi G, Temme C, Jansen J, von Wichert G, Omary MB, Spatz J, Seufferlein T. Keratin 8 phosphorylation regulates keratin reorganization and migration of epithelial tumor cells. J Cell Sci 2012; 125:2148-59. [PMID: 22344252 DOI: 10.1242/jcs.080127] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Cell migration and invasion are largely dependent on the complex organization of the various cytoskeletal components. Whereas the role of actin filaments and microtubules in cell motility is well established, the role of intermediate filaments in this process is incompletely understood. Organization and structure of the keratin cytoskeleton, which consists of heteropolymers of at least one type 1 and one type 2 intermediate filament, are in part regulated by post-translational modifications. In particular, phosphorylation events influence the properties of the keratin network. Sphingosylphosphorylcholine (SPC) is a bioactive lipid with the exceptional ability to change the organization of the keratin cytoskeleton, leading to reorganization of keratin filaments, increased elasticity, and subsequently increased migration of epithelial tumor cells. Here we investigate the signaling pathways that mediate SPC-induced keratin reorganization and the role of keratin phosphorylation in this process. We establish that the MEK-ERK signaling cascade regulates both SPC-induced keratin phosphorylation and reorganization in human pancreatic and gastric cancer cells and identify Ser431 in keratin 8 as the crucial residue whose phosphorylation is required and sufficient to induce keratin reorganization and consequently enhanced migration of human epithelial tumor cells.
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Affiliation(s)
- Tobias Busch
- Department of Internal Medicine I, University of Ulm, Ulm, Germany
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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: 102] [Impact Index Per Article: 7.8] [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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15
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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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16
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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: 89] [Impact Index Per Article: 6.4] [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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17
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Hasegawa Y, Murph M, Yu S, Tigyi G, Mills GB. Lysophosphatidic acid (LPA)-induced vasodilator-stimulated phosphoprotein mediates lamellipodia formation to initiate motility in PC-3 prostate cancer cells. Mol Oncol 2009; 2:54-69. [PMID: 19081821 DOI: 10.1016/j.molonc.2008.03.009] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Prostate cancer remains the most frequently diagnosed malignancy and the second leading cause of cancer mortality among men in the United States. Hormone refractory, metastatic disease has no molecular therapeutics to date and survival is poor. Lysophosphatidic acid (LPA) is a bioactive lipid exhibiting motility, invasive, growth, proliferative and survival effects in multiple cancer cell lineages. Cells express different combinations of LPA-specific G protein-coupled receptors, LPA(1), LPA(2) LPA(3), and LPA(4) as well as other LPA receptors, which bind LPA and thereby regulate lipid signaling. The role of specific LPA receptors in functional outcomes of lysolipid signaling remains to be fully elucidated in prostate cancer. We hypothesized that LPA can initiate cell migration through specific LPA receptors by activating actin-associating proteins involved in motility, including the vasodilator-stimulated phosphoprotein (VASP). In the present study, we demonstrate that LPA-induced lamellipodia formation in cells is dependent on LPA receptor-mediated phosphorylation of VASP, demonstrating a previously unknown regulation by LPA. LPA induces phosphorylation of VASP at Ser(157), through protein kinase A (PKA) since the stimulation was abrogated by PKA inhibition. In addition, we found the effects of LPA-induced lamellipodia formation and migration were reduced by knockdown of either VASP or LPA receptor expression, suggesting that LPA receptor-induced VASP phosphorylation is a critical mediator of migration initiation. Thus the LPA(2) and LPA(3) receptors, in addition to the previously implicated LPA(1) receptor, play a role in cellular motility potentially contributing to invasion and metastases. Emerging drugs targeting the LPA pathway may be beneficial for the treatment of metastatic progression in prostate cancer.
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Affiliation(s)
- Yutaka Hasegawa
- Department of Systems Biology, The University of Texas M. D. Anderson Cancer Center, 7435 Fannin Street, Houston, TX 77054, USA
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18
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Li H, Wang D, Singh LS, Berk M, Tan H, Zhao Z, Steinmetz R, Kirmani K, Wei G, Xu Y. Abnormalities in osteoclastogenesis and decreased tumorigenesis in mice deficient for ovarian cancer G protein-coupled receptor 1. PLoS One 2009; 4:e5705. [PMID: 19479052 PMCID: PMC2684630 DOI: 10.1371/journal.pone.0005705] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2009] [Accepted: 05/05/2009] [Indexed: 12/13/2022] Open
Abstract
Ovarian cancer G protein-coupled receptor 1 (OGR1) has been shown to be a proton sensing receptor in vitro. We have shown that OGR1 functions as a tumor metastasis suppressor gene when it is over-expressed in human prostate cancer cells in vivo. To examine the physiological functions of OGR1, we generated conditional OGR1 deficient mice by homologous recombination. OGR1 deficient mice were viable and upon gross-inspection appeared normal. Consistent with in vitro studies showing that OGR1 is involved in osteoclastogenesis, reduced osteoclasts were detected in OGR1 deficient mice. A pH-dependent osteoclasts survival effect was also observed. However, overall abnormality in the bones of these animals was not observed. In addition, melanoma cell tumorigenesis was significantly inhibited in OGR1 deficient mice. OGR1 deficient mice in the mixed background produced significantly less peritoneal macrophages when stimulated with thioglycolate. These macrophages also showed altered extracellular signal-regulated kinases (ERK) activation and nitric oxide (NO) production in response to lipopolysaccharide. OGR1-dependent pH responses assessed by cAMP production and cell survival in macrophages or brown fat cells were not observed, presumably due to the presence of other proton sensing receptors in these cells. Our results indicate that OGR1's role in osteoclastogenesis is not strong enough to affect overall bone development and its role in tumorigenesis warrants further investigation. The mice generated can be potentially used for several disease models, including cancers or osteoclast-related diseases.
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Affiliation(s)
- Hui Li
- Department of Obstetrics and Gynecology, Indiana University Cancer Center, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
- Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Dongmei Wang
- Department of Obstetrics and Gynecology, Indiana University Cancer Center, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
| | - Lisam Shanjukumar Singh
- Department of Obstetrics and Gynecology, Indiana University Cancer Center, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
- Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
- Department of Biotechnology, Manipur University, Canchipur, Manipur, India
| | - Michael Berk
- Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Haiyan Tan
- Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Zhenwen Zhao
- Department of Obstetrics and Gynecology, Indiana University Cancer Center, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
- Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Rosemary Steinmetz
- Department of Obstetrics and Gynecology, Indiana University Cancer Center, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
| | - Kashif Kirmani
- Department of Obstetrics and Gynecology, Indiana University Cancer Center, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
| | - Gang Wei
- Department of Obstetrics and Gynecology, Indiana University Cancer Center, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
| | - Yan Xu
- Department of Obstetrics and Gynecology, Indiana University Cancer Center, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
- * E-mail:
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19
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Seuwen K, Ludwig MG, Wolf RM. Receptors for protons or lipid messengers or both? J Recept Signal Transduct Res 2007; 26:599-610. [PMID: 17118800 DOI: 10.1080/10799890600932220] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The subfamily of G protein-coupled receptors comprising GPR4, OGR1, TDAG8, and G2A was originally characterized as a group of proteins mediating biological responses to the lipid messengers sphingosylphosphorylcholine (SPC), lysophosphatidylcholine (LPC), and psychosine. We challenged this view by reporting that OGR1 and GPR4 sense acidic pH and that this process is not affected by concentrations of SPC or LPC previously reported as agonistic. The original publications describing GPR4, OGR1, and G2A as receptors for LPC or SPC have now been retracted, and the first studies exploring receptors of this family as pH sensors in physiology have appeared. Here we review the status of this field and we confirm that GPR4, OGR1, and TDAG8 should be considered as proton-sensing receptors. Negative regulation of these receptors by high micromolar concentrations of lipids appears not specific in our experiments.
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Affiliation(s)
- Klaus Seuwen
- Novartis Institutes for Biomedical Research, Basel, Switzerland.
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20
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Yang LV, Radu CG, Roy M, Lee S, McLaughlin J, Teitell MA, Iruela-Arispe ML, Witte ON. Vascular abnormalities in mice deficient for the G protein-coupled receptor GPR4 that functions as a pH sensor. Mol Cell Biol 2006; 27:1334-47. [PMID: 17145776 PMCID: PMC1800706 DOI: 10.1128/mcb.01909-06] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
GPR4 is a G protein-coupled receptor expressed in the vasculature, lung, kidney, and other tissues. In vitro ectopic overexpression studies implicated GPR4 in sensing extracellular pH changes leading to cyclic AMP (cAMP) production. To investigate its biological roles in vivo, we generated GPR4-deficient mice by homologous recombination. Whereas GPR4-null adult mice appeared phenotypically normal, neonates showed a higher frequency of perinatal mortality. The average litter size from GPR4(-/-) intercrosses was approximately 30% smaller than that from GPR4(+/+) intercrosses on N3 and N5 C57BL/6 genetic backgrounds. A fraction of knockout embryos and neonates had spontaneous hemorrhages, dilated and tortuous subcutaneous blood vessels, and defective vascular smooth muscle cell coverage. Mesangial cells in kidney glomeruli were also significantly reduced in GPR4-null neonates. Some neonates exhibited respiratory distress with airway lining cell metaplasia. To examine whether GPR4 is functionally involved in vascular pH sensing, an ex vivo aortic ring assay was used under defined pH conditions. Compared to wild-type aortas, microvessel outgrowth from GPR4-null aortas was less inhibited by acidic extracellular pH. Treatment with an analog of cAMP, a downstream effector of GPR4, abolished microvessel outgrowth bypassing the GPR4-knockout phenotype. These results suggest that GPR4 deficiency leads to partially penetrant vascular abnormalities during development and that this receptor functions in blood vessel pH sensing.
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MESH Headings
- Animals
- Animals, Newborn
- Aorta/abnormalities
- Blood Vessels/abnormalities
- Blood Vessels/embryology
- Cells, Cultured
- Crosses, Genetic
- Embryo, Mammalian/abnormalities
- Embryo, Mammalian/blood supply
- Embryo, Mammalian/pathology
- Female
- Gene Targeting
- Genotype
- Hemorrhage/congenital
- Humans
- Hydrogen-Ion Concentration
- Litter Size
- Lung/abnormalities
- Lung/embryology
- Lung/pathology
- Male
- Mesangial Cells/pathology
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Penetrance
- Receptors, G-Protein-Coupled/deficiency
- Receptors, G-Protein-Coupled/metabolism
- Respiratory Tract Diseases/congenital
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Affiliation(s)
- Li V Yang
- Howard Hughes Medical Institute, University of California-Los Angeles, 675 Charles E. Young Drive South, Los Angeles, CA 90095-1662, USA
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21
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Sin WC, Zhang Y, Zhong W, Adhikarakunnathu S, Powers S, Hoey T, An S, Yang J. G protein-coupled receptors GPR4 and TDAG8 are oncogenic and overexpressed in human cancers. Oncogene 2004; 23:6299-303. [PMID: 15221007 DOI: 10.1038/sj.onc.1207838] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The GPR4 subfamily consists of four G protein-coupled receptors that share significant sequence homology. In addition to GPR4, this subfamily includes OGR1, TDAG8 and G2A. G2A has previously been shown to be a potent transforming oncogene for murine 3T3 cells. Here we show that GPR4 also malignantly transforms NIH3T3 cells and that TDAG8 malignantly transforms the normal mammary epithelial cell line NMuMG. Overexpression of GPR4 or TDAG8 in HEK293 cells led to transcriptional activation from SRE- and CRE-driven promoters, independent of exogenously added ligand. TDAG8 and GPR4 are also overexpressed in a range of human cancer tissues. Our results suggest that GPR4 and TDAG8 overexpression in human tumors plays a role in driving or maintaining tumor formation.
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Affiliation(s)
- Wun Chey Sin
- Genomics Division, Tularik Inc., 266 East Pulaski Rd, Greenlawn, NY 11740, USA
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22
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Ludwig MG, Vanek M, Guerini D, Gasser JA, Jones CE, Junker U, Hofstetter H, Wolf RM, Seuwen K. Proton-sensing G-protein-coupled receptors. Nature 2003; 425:93-8. [PMID: 12955148 DOI: 10.1038/nature01905] [Citation(s) in RCA: 528] [Impact Index Per Article: 25.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2003] [Accepted: 07/08/2003] [Indexed: 02/07/2023]
Abstract
Blood pH is maintained in a narrow range around pH 7.4 mainly through regulation of respiration and renal acid extrusion. The molecular mechanisms involved in pH homeostasis are not completely understood. Here we show that ovarian cancer G-protein-coupled receptor 1 (OGR1), previously described as a receptor for sphingosylphosphorylcholine, acts as a proton-sensing receptor stimulating inositol phosphate formation. The receptor is inactive at pH 7.8, and fully activated at pH 6.8-site-directed mutagenesis shows that histidines at the extracellular surface are involved in pH sensing. We find that GPR4, a close relative of OGR1, also responds to pH changes, but elicits cyclic AMP formation. It is known that the skeleton participates in pH homeostasis as a buffering organ, and that osteoblasts respond to pH changes in the physiological range, but the pH-sensing mechanism operating in these cells was hitherto not known. We detect expression of OGR1 in osteosarcoma cells and primary human osteoblast precursors, and show that these cells exhibit strong pH-dependent inositol phosphate formation. Immunohistochemistry on rat tissue sections confirms the presence of OGR1 in osteoblasts and osteocytes. We propose that OGR1 and GPR4 are proton-sensing receptors involved in pH homeostasis.
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23
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Mills GB, Eder A, Fang X, Hasegawa Y, Mao M, Lu Y, Tanyi J, Tabassam FH, Wiener J, Lapushin R, Yu S, Parrott JA, Compton T, Tribley W, Fishman D, Stack MS, Gaudette D, Jaffe R, Furui T, Aoki J, Erickson JR. Critical role of lysophospholipids in the pathophysiology, diagnosis, and management of ovarian cancer. Cancer Treat Res 2002; 107:259-83. [PMID: 11775454 DOI: 10.1007/978-1-4757-3587-1_12] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Lysophosphatidic acid (LPA), the simplest of all phospholipids, exhibits pleiomorphic functions in multiple cell lineages. The effects of LPA appear to be mediated by binding of LPA to specific members of the endothelial differentiation gene (Edg) family of G protein-coupled receptors (GPCR). Edg 2, Edg4, and Edg7 are high affinity receptors for LPA, and Edg1 may be a low affinity receptor for LPA. PSP24 has been shown to be responsive to LPA in Xenopus oocytes, however, its role in mammalian cells is unclear. The specific biochemical events initiated by the different Edg receptors, as well as the biological outcomes of activation of the individual receptors, are only beginning to be determined. LPA levels are consistently elevated in the plasma and ascites of ovarian cancer patients, but not in most other epithelial tumors, with the exception of cervix and endometrium, suggesting that LPA may be of particular importance in the pathophysiology of ovarian cancer. In support of this concept, ovarian cancer cells constitutively and inducibly produce high levels of LPA and demonstrate markedly different responses to LPA than normal ovarian surface epithelium. Edg4 and Edg7 levels are consistently increased in malignant ovarian epithelial cells contributing to the aberrant response of ovarian cancer cells to LPA. Edg2 may represent a negative regulatory LPA receptor inducing apoptosis in ovarian cancer cells. Thus, increased levels of LPA, altered receptor expression and altered responses to LPA may contribute to the initiation, progression or outcome of ovarian cancer. Over 40% of known drugs target GPCR, making LPA receptors attractive targets for molecular therapeutics. Indeed, using the structure-function relationship of LPA in model systems, we have identified selective Edg2 anatgonists, as well as Edg4 and Edg7 agonists. These lead compounds are being assessed in preclinical model systems. Understanding the mechanisms regulating LPA production, metabolism and function could lead to improved methods for early detection and to new targets for therapy in ovarian cancer.
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Affiliation(s)
- Gordon B Mills
- Department of Molecular Therapeutics, MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030, USA
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24
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Zhu K, Baudhuin LM, Hong G, Williams FS, Cristina KL, Kabarowski JH, Witte ON, Xu Y. Sphingosylphosphorylcholine and lysophosphatidylcholine are ligands for the G protein-coupled receptor GPR4. J Biol Chem 2001; 276:41325-35. [PMID: 11535583 DOI: 10.1074/jbc.m008057200] [Citation(s) in RCA: 185] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Sphingosylphosphorylcholine (SPC) and lysophosphatidylcholine (LPC) are bioactive lipid molecules involved in numerous biological processes. We have recently identified ovarian cancer G protein-coupled receptor 1 (OGR1) as a specific and high affinity receptor for SPC, and G2A as a receptor with high affinity for LPC, but low affinity for SPC. Among G protein-coupled receptors, GPR4 shares highest sequence homology with OGR1 (51%). In this work, we have identified GPR4 as not only another high affinity receptor for SPC, but also a receptor for LPC, albeit of lower affinity. Both SPC and LPC induce increases in intracellular calcium concentration in GPR4-, but not vector-transfected MCF10A cells. These effects are insensitive to treatment with BN52021, WEB-2170, and WEB-2086 (specific platelet activating factor (PAF) receptor antagonists), suggesting that they are not mediated through an endogenous PAF receptor. SPC and LPC bind to GPR4 in GPR4-transfected CHO cells with K(d)/SPC = 36 nm, and K(d)/LPC = 159 nm, respectively. Competitive binding is elicited only by SPC and LPC. Both SPC and LPC activate GPR4-dependent activation of serum response element reporter and receptor internalization. Swiss 3T3 cells expressing GPR4 respond to both SPC and LPC, but not sphingosine 1-phosphate (S1P), PAF, psychosine (Psy), glucosyl-beta1'1-sphingosine (Glu-Sph), galactosyl-beta1'1-ceramide (Gal-Cer), or lactosyl-beta1'1-ceramide (Lac-Cer) to activate extracellular signal-regulated kinase mitogen-activated protein kinase in a concentration- and time-dependent manner. SPC and LPC stimulate DNA synthesis in GPR4-expressing Swiss 3T3 cells. Both extracellular signal-regulated kinase activation and DNA synthesis stimulated by SPC and LPC are pertussis toxin-sensitive, suggesting the involvement of a G(i)-heterotrimeric G protein. In addition, GPR4 expression confers chemotactic responses to both SPC and LPC in Swiss 3T3 cells. Taken together, our data indicate that GPR4 is a receptor with high affinity to SPC and low affinity to LPC, and that multiple cellular functions can be transduced via this receptor.
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Affiliation(s)
- K Zhu
- Department of Cancer Biology, Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA
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