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Ashton AW. Preparing to strike: Acute events in signaling by the serpentine receptor for thromboxane A 2. Pharmacol Ther 2023:108478. [PMID: 37321373 DOI: 10.1016/j.pharmthera.2023.108478] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Revised: 05/31/2023] [Accepted: 06/07/2023] [Indexed: 06/17/2023]
Abstract
Over the last two decades, awareness of the (patho)physiological roles of thromboxane A2 signaling has been greatly extended. From humble beginnings as a short-lived stimulus that activates platelets and causes vasoconstriction to a dichotomous receptor system involving multiple endogenous ligands capable of modifying tissue homeostasis and disease generation in almost every tissue of the body. Thromboxane A2 receptor (TP) signal transduction is associated with the pathogenesis of cancer, atherosclerosis, heart disease, asthma, and host response to parasitic infection amongst others. The two receptors mediating these cellular responses (TPα and TPβ) are derived from a single gene (TBXA2R) through alternative splicing. Recently, knowledge about the mechanism(s) of signal propagation by the two receptors has undergone a revolution in understanding. Not only have the structural relationships associated with G-protein coupling been established but the modulation of that signaling by post-translational modification to the receptor has come sharply into focus. Moreover, the signaling of the receptor unrelated to G-protein coupling has become a burgeoning field of endeavor with over 70 interacting proteins currently identified. These data are reshaping the concept of TP signaling from a mere guanine nucleotide exchange factors for Gα activation to a nexus for the convergence of diverse and poorly characterized signaling pathways. This review summarizes the advances in understanding in TP signaling, and the potential for new growth in a field that after almost 50 years is finally coming of age.
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Affiliation(s)
- Anthony W Ashton
- Division of Cardiovascular Medicine, Lankenau Institute for Medical Research, Rm 128, 100 E Lancaster Ave, Wynnewood, PA 19096, USA; Division of Perinatal Research, Kolling Institute of Medical Research, Faculty of Medicine and Health, University of Sydney, St Leonards, NSW 2065, Australia.
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2
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Biringer RG. A Review of Prostanoid Receptors: Expression, Characterization, Regulation, and Mechanism of Action. J Cell Commun Signal 2020; 15:155-184. [PMID: 32970276 DOI: 10.1007/s12079-020-00585-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2020] [Accepted: 09/15/2020] [Indexed: 12/22/2022] Open
Abstract
Prostaglandin signaling controls a wide range of biological processes from blood pressure homeostasis to inflammation and resolution thereof to the perception of pain to cell survival. Disruption of normal prostanoid signaling is implicated in numerous disease states. Prostaglandin signaling is facilitated by G-protein-coupled, prostanoid-specific receptors and the array of associated G-proteins. This review focuses on the expression, characterization, regulation, and mechanism of action of prostanoid receptors with particular emphasis on human isoforms.
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Affiliation(s)
- Roger G Biringer
- College of Osteopathic Medicine, Lake Erie College of Osteopathic Medicine, 5000 Lakewood Ranch Blvd, Bradenton, FL, 34211, USA.
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Mulvaney EP, Shilling C, Eivers SB, Perry AS, Bjartell A, Kay EW, Watson RW, Kinsella BT. Expression of the TPα and TPβ isoforms of the thromboxane prostanoid receptor (TP) in prostate cancer: clinical significance and diagnostic potential. Oncotarget 2018; 7:73171-73187. [PMID: 27689401 PMCID: PMC5341971 DOI: 10.18632/oncotarget.12256] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Accepted: 09/19/2016] [Indexed: 12/21/2022] Open
Abstract
The prostanoid thromboxane (TX) A2 plays a central role in haemostasis and is increasingly implicated in cancer progression. TXA2 signals through two T Prostanoid receptor (TP) isoforms termed TPα and TPβ, with both encoded by the TBXA2R gene. Despite exhibiting several functional and regulatory differences, the role of the individual TP isoforms in neoplastic diseases is largely unknown. This study evaluated expression of the TPα and TPβ isoforms in tumour microarrays of the benign prostate and different pathological (Gleason) grades of prostate cancer (PCa). Expression of TPβ was significantly increased in PCa relative to benign tissue and strongly correlated with increasing Gleason grade. Furthermore, higher TPβ expression was associated with increased risk of biochemical recurrence (BCR) and significantly shorter disease-free survival time in patients post-surgery. While TPα was more variably expressed than TPβ in PCa, increased/high TPα expression within the tumour also trended toward increased BCR and shorter disease-free survival time. Comparative genomic CpG DNA methylation analysis revealed substantial differences in the extent of methylation of the promoter regions of the TBXA2R that specifically regulate expression of TPα and TPβ, respectively, both in benign prostate and in clinically-derived tissue representative of precursor lesions and progressive stages of PCa. Collectively, TPα and TPβ expression is differentially regulated both in the benign and tumourigenic prostate, and coincides with clinical pathology and altered CpG methylation of the TBXA2R gene. Analysis of TPβ, or a combination of TPα/TPβ, expression levels may have significant clinical potential as a diagnostic biomarker and predictor of PCa disease recurrence.
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Affiliation(s)
- Eamon P Mulvaney
- UCD School of Biomolecular and Biomedical Science, University College Dublin, Belfield, Dublin, Ireland
| | - Christine Shilling
- Department of Pathology, Beaumont Hospital and Royal College of Surgeons, Dublin, Ireland
| | - Sarah B Eivers
- UCD School of Biomolecular and Biomedical Science, University College Dublin, Belfield, Dublin, Ireland
| | - Antoinette S Perry
- UCD School of Biomolecular and Biomedical Science, University College Dublin, Belfield, Dublin, Ireland
| | - Anders Bjartell
- Department of Translational Medicine, Division of Urological Cancers, Skåne University Hospital Malmö, Lund University, Lund, Sweden
| | - Elaine W Kay
- Department of Pathology, Beaumont Hospital and Royal College of Surgeons, Dublin, Ireland
| | - R William Watson
- UCD School of Medicine, UCD Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin, Ireland
| | - B Therese Kinsella
- UCD School of Biomolecular and Biomedical Science, University College Dublin, Belfield, Dublin, Ireland
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Moscardó A, Fuset MP, Ruano M, Santos MT, Vallés J. Residual cyclooxygenase-1 activity and epinephrine reduce the antiplatelet effect of aspirin in patients with acute myocardial infarction. Thromb Haemost 2017; 105:663-9. [DOI: 10.1160/th10-08-0550] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2010] [Accepted: 01/19/2011] [Indexed: 01/22/2023]
Abstract
SummaryAspirin treatment is essential in patients with acute myocardial infarction (AMI) to block platelet thromboxane (TXA)2 synthesis. Epinephrine is known to enhance platelet reactivity induced by other agonists and to be elevated in patients with AMI due to stress. Our objective was to study the influence of epinephrine on platelet TXA2 synthesis in patients treated with aspirin for AMI at early onset (within 48 hours) and the potential biochemical mechanisms involved in the functional response. Washed platelets from 45 patients with AMI and 10 aspirin-free controls were stimulated with arachidonic acid (AA) or AA + epinephrine, and aggregation and TXA2 synthesis were evaluated. Full platelet aggregation was recorded in 8/45 patients (18%) with a partial TXA2 inhibition (86%) vs. the aspirin-free controls. Platelets from the remaining 37 patients did not aggregate to AA and had TXA2 inhibition >95%. However, when platelets were simultaneously stimulated with AA + epinephrine, in 25/37 patients a large intensity of aggregation (73%) was observed and a 5.5-fold increase in TXA2 synthesis, although this remained residual (<5% of aspirin-free controls). This residual-TXA2 was critical in the functional response, as demonstrated by the complete inhibition by TXA2 receptor blockade or additional aspirin in vitro. The phosphatidylinositol-3-kinase activity and the cytosolic calcium levels participated in this platelet response elicited by a receptor cooperation mechanism, while the Rho/p160ROCK pathway or the blockade of the ADP receptors (P2Y1, P2Y12) were without effect. Residual-cyclooxygenase –1 activity and epinephrine enhance TXA2-dependent platelet function, which may reduce the clinical benefit of aspirin in patients with AMI.
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O'Sullivan AG, Mulvaney EP, Kinsella BT. Regulation of protein kinase C-related kinase (PRK) signalling by the TPα and TPβ isoforms of the human thromboxane A 2 receptor: Implications for thromboxane- and androgen- dependent neoplastic and epigenetic responses in prostate cancer. Biochim Biophys Acta Mol Basis Dis 2017; 1863:838-856. [PMID: 28108419 DOI: 10.1016/j.bbadis.2017.01.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Revised: 01/11/2017] [Accepted: 01/16/2017] [Indexed: 12/11/2022]
Abstract
The prostanoid thromboxane (TX) A2 and its T Prostanoid receptor (the TP) are increasingly implicated in prostate cancer (PCa). Mechanistically, we recently discovered that both TPα and TPβ form functional signalling complexes with members of the protein kinase C-related kinase (PRK) family, AGC- kinases essential for the epigenetic regulation of androgen receptor (AR)-dependent transcription and promising therapeutic targets for treatment of castrate-resistant prostate cancer (CRPC). Critically, similar to androgens, activation of the PRKs through the TXA2/TP signalling axis induces phosphorylation of histone H3 at Thr11 (H3Thr11), a marker of androgen-induced chromatin remodelling and transcriptional activation, raising the possibility that TXA2-TP signalling can mimic and/or enhance AR-induced cellular changes even in the absence of circulating androgens such as in CRPC. Hence the aim of the current study was to investigate whether TXA2/TP-induced PRK activation can mimic and/or enhance AR-mediated cellular responses in the model androgen-responsive prostate adenocarcinoma LNCaP cell line. We reveal that TXA2/TP signalling can act as a neoplastic- and epigenetic-regulator, promoting and enhancing both AR-associated chromatin remodelling (H3Thr11 phosphorylation, WDR5 recruitment and acetylation of histone H4 at lysine 16) and AR-mediated transcriptional activation (e.g of the KLK3/prostate-specific antigen and TMPRSS2 genes) through mechanisms involving TPα/TPβ mediated-PRK1 and PRK2, but not PRK3, signalling complexes. Overall, these data demonstrate that TPα/TPβ can act as neoplastic and epigenetic regulators by mimicking and/or enhancing the actions of androgens within the prostate and provides further mechanistic insights into the role of the TXA2/TP signalling axis in PCa, including potentially in CRPC.
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Affiliation(s)
- Aine G O'Sullivan
- UCD School of Biomolecular and Biomedical Sciences, UCD Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland
| | - Eamon P Mulvaney
- UCD School of Biomolecular and Biomedical Sciences, UCD Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland
| | - B Therese Kinsella
- UCD School of Biomolecular and Biomedical Sciences, UCD Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland.
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Protein kinase C-related kinase 1 and 2 play an essential role in thromboxane-mediated neoplastic responses in prostate cancer. Oncotarget 2016; 6:26437-56. [PMID: 26296974 PMCID: PMC4694913 DOI: 10.18632/oncotarget.4664] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2015] [Accepted: 07/06/2015] [Indexed: 01/03/2023] Open
Abstract
The prostanoid thromboxane (TX) A2 is increasingly implicated in neoplastic progression, including prostate cancer (PCa). Mechanistically, we recently identified protein kinase C-related kinase (PRK) 1 as a functional interactant of both the TPα and TPβ isoforms of the human T prostanoid receptor (TP). The interaction with PRK1 was not only essential for TPα/TPβ-induced PCa cell migration but also enabled the TXA2-TP axis to induce phosphorylation of histone H3 at Thr11 (H3Thr11), an epigenetic marker both essential for and previously exclusively associated with androgen-induced chromatin remodelling and transcriptional activation. PRK1 is a member of a subfamily of three structurally related kinases comprising PRK1/PKNα, PRK2/PKNγ and PRK3/PKNβ that are widely yet differentially implicated in various cancers. Hence, focusing on the setting of prostate cancer, this study investigated whether TPα and/or TPβ might also complex with PRK2 and PRK3 to regulate their activity and neoplastic responses. While TPα and TPβ were found in immune complexes with PRK1, PRK2 and PRK3 to regulate their activation and signalling, they do so differentially and in a TP agonist-regulated manner dependent on the T-loop activation status of the PRKs but independent of their kinase activity. Furthermore, TXA2-mediated neoplastic responses in prostate adenocarcinoma PC-3 cells, including histone H3Thr11 phosphorylation, was found to occur through a PRK1- and PRK2-, but not PRK3-, dependent mechanism. Collectively, these data suggest that TXA2 acts as both a neoplastic and epigenetic regulator and provides a mechanistic explanation, at least in part, for the prophylactic benefits of Aspirin in reducing the risk of certain cancers.
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Touchberry CD, Silswal N, Tchikrizov V, Elmore CJ, Srinivas S, Akthar AS, Swan HK, Wetmore LA, Wacker MJ. Cardiac thromboxane A2 receptor activation does not directly induce cardiomyocyte hypertrophy but does cause cell death that is prevented with gentamicin and 2-APB. BMC Pharmacol Toxicol 2014; 15:73. [PMID: 25519194 PMCID: PMC4293009 DOI: 10.1186/2050-6511-15-73] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2014] [Accepted: 12/12/2014] [Indexed: 12/31/2022] Open
Abstract
Background We have previously shown that the thromboxane (TXA2) receptor agonist, U46619, can directly induce ventricular arrhythmias that were associated with increases in intracellular calcium in cardiomyocytes. Since TXA2 is an inflammatory mediator and induces direct calcium changes in cardiomyocytes, we hypothesized that TXA2 released during ischemia or inflammation could also cause cardiac remodeling. Methods U46619 (0.1-10 μM) was applied to isolated adult mouse ventricular primary cardiomyocytes, mouse ventricular cardiac muscle strips, and cultured HL-1 cardiomyocytes and markers of hypertrophy and cell death were measured. Results We found that TXA2 receptors were expressed in ventricular cardiomyocytes and were functional via calcium imaging. U46619 treatment for 24 h did not increase expression of pathological hypertrophy genes (atrial natriuretic peptide, β-myosin heavy chain, skeletal muscle α-actin) and it did not increase protein synthesis. There was also no increase in cardiomyocyte size after 48 h treatment with U46619 as measured by flow cytometry. However, U46619 (0.1-10 μM) caused a concentration-dependent increase in cardiomyocyte death (trypan blue, MTT assays, visual cell counts and TUNEL stain) after 24 h. Treatment of cells with the TXA2 receptor antagonist SQ29548 and inhibitors of the IP3 pathway, gentamicin and 2-APB, eliminated the increase in cell death induced by U46619. Conclusions Our data suggests that TXA2 does not induce cardiac hypertrophy, but does induce cell death that is mediated in part by IP3 signaling pathways. These findings may provide important therapeutic targets for inflammatory-induced cardiac apoptosis that can lead to heart failure.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Michael J Wacker
- Muscle Biology Group, School of Medicine, University of Missouri-Kansas City, 2464 Charlotte Street, Kansas City, MO 64108, USA.
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Santhosh KT, Sikarwar AS, Hinton M, Chelikani P, Dakshinamurti S. Thromboxane receptor hyper-responsiveness in hypoxic pulmonary hypertension requires serine 324. Br J Pharmacol 2014; 171:676-87. [PMID: 24490858 DOI: 10.1111/bph.12487] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2013] [Revised: 09/21/2013] [Accepted: 10/03/2013] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND AND PURPOSE Dysregulation of the thromboxane A₂ (TP) receptor, resulting in agonist hypersensitivity and hyper-responsiveness, contributes to exaggerated vasoconstriction in the hypoxic pulmonary artery in neonatal persistent pulmonary hypertension. We previously reported that hypoxia inhibits TP receptor phosphorylation, causing desensitization. Hence, we examined the role of PKA-accessible serine residues in determining TP receptor affinity, using site-directed mutational analysis. EXPERIMENTAL APPROACH Vasoconstriction to a thromboxane mimetic and phosphorylation of TP receptor serine was examined in pulmonary arteries from neonatal swine with persistent pulmonary hypertension and controls. Effects of hypoxia were determined in porcine and human TP receptors. Human TPα serines at positions 324, 329 and 331 (C-terminal tail) were mutated to alanine and transiently expressed in HEK293T cells. Saturation binding and displacement kinetics of a TP antagonist and agonist were determined in porcine TP, wild-type human TPα and all TP mutants. Agonist-elicited calcium mobilization was determined for each TP mutant, in the presence of a PKA activator or inhibitor, and in hypoxic and normoxic conditions. KEY RESULTS The Ser324A mutant was insensitive to PKA activation and hypoxia, had a high affinity for agonist and increased agonist-induced calcium mobilization. Ser329A was no different from wild-type TP receptors. Ser331A was insensitive to hypoxia and PKA with a decreased agonist-mediated response. CONCLUSIONS AND IMPLICATIONS In hypoxic pulmonary hypertension, loss of site-specific phosphorylation of the TP receptor causes agonist hyper-responsiveness. Ser324 is the primary residue phosphorylated by PKA, which regulates TP receptor-agonist interactions. Ser331 mutation confers loss of TP receptor-agonist interaction, regardless of PKA activity.
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Affiliation(s)
- K T Santhosh
- Biology of Breathing Group, Manitoba Institute of Child Health, Winnipeg, MB, Canada
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Keating GL, Reid HM, Eivers SB, Mulvaney EP, Kinsella BT. Transcriptional regulation of the human thromboxane A2 receptor gene by Wilms' tumor (WT)1 and hypermethylated in cancer (HIC) 1 in prostate and breast cancers. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2014; 1839:476-92. [PMID: 24747176 DOI: 10.1016/j.bbagrm.2014.04.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2013] [Revised: 04/09/2014] [Accepted: 04/10/2014] [Indexed: 01/17/2023]
Abstract
The prostanoid thromboxane (TX) A(2) plays a central role in hemostasis and is increasingly implicated in neoplastic disease, including prostate and breast cancers. In humans, TXA(2) signals through the TPα and TPβ isoforms of the T prostanoid receptor, two structurally related receptors transcriptionally regulated by distinct promoters, Prm1 and Prm3, respectively, within the TP gene. Focusing on TPα, the current study investigated its expression and transcriptional regulation through Prm1 in prostate and breast cancers. Expression of TPα correlated with increasing prostate and breast tissue tumor grade while the TXA(2) mimetic U46619 promoted both proliferation and migration of the respective prostate (PC3) and breast (MCF-7 and MDA-MD-231) derived-carcinoma cell lines. Through 5' deletional and genetic reporter analyses, several functional upstream repressor regions (URRs) were identified within Prm1 in PC3, MCF-7 and MDA-MB-231 cells while site-directed mutagenesis identified the tumor suppressors Wilms' tumor (WT)1 and hypermethylated in cancer (HIC) 1 as the trans-acting factors regulating those repressor regions. Chromatin immunoprecipitation (ChIP) studies confirmed that WT1 binds in vivo to multiple GC-enriched WT1 cis-elements within the URRs of Prm1 in PC3, MCF-7 and MDA-MB-231 cells. Furthermore, ChIP analyses established that HIC1 binds in vivo to the HIC1((b))cis-element within Prm1 in PC3 and MCF-7 cells but not in the MDA-MB-231 carcinoma line. Collectively, these data establish that WT1 and HIC1, both tumor suppressors implicated in prostate and breast cancers, transcriptionally repress TPα expression and thereby provide a strong genetic basis for understanding the role of TXA2 in the progression of certain human cancers.
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Affiliation(s)
- Garret L Keating
- UCD School of Biomolecular and Biomedical Sciences, UCD Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield Dublin 4, Ireland
| | - Helen M Reid
- UCD School of Biomolecular and Biomedical Sciences, UCD Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield Dublin 4, Ireland
| | - Sarah B Eivers
- UCD School of Biomolecular and Biomedical Sciences, UCD Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield Dublin 4, Ireland
| | - Eamon P Mulvaney
- UCD School of Biomolecular and Biomedical Sciences, UCD Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield Dublin 4, Ireland
| | - B Therese Kinsella
- UCD School of Biomolecular and Biomedical Sciences, UCD Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield Dublin 4, Ireland.
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Synthesis and pharmacological evaluation of 2-aryloxy/arylamino-5-cyanobenzenesulfonylureas as novel thromboxane A₂ receptor antagonists. Eur J Med Chem 2013; 65:32-40. [PMID: 23688698 DOI: 10.1016/j.ejmech.2013.04.033] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2012] [Revised: 04/10/2013] [Accepted: 04/13/2013] [Indexed: 11/20/2022]
Abstract
New series of original 2-aryloxy/arylamino-5-cyanobenzenesulfonylureas were synthesized and evaluated as thromboxane A2 receptor (TP receptor) antagonists. A functional pharmacological test was used, which consisted of measuring the inhibition of intracellular calcium mobilization in a model of mammalian cell line that specifically over-expressed the individual TPα or TPβ isoforms. 2-Arylamino-5-cyanobenzenesulfonylureas exhibited virtually identical affinity and/or functional activity than 2-aryloxy-5-cyanobenzenesulfonylureas for both TPα and TPβ, but some 2-aryloxy-substituted compounds showed increased selectivity for TPβ relative to TPα. Several compounds were found to be as potent as the 2-arylamino-5-nitrobenzenesulfonylurea reference compound BM-573, supporting the view that the bioisosteric replacement of the nitro group by a cyano group was tolerated. TP receptor antagonist activity of the most promising molecules was confirmed in a platelet aggregation assay using the TP receptor agonist U-46619 as a proaggregant. Three compounds (7e, 7h and 8h) were identified as leads for further non-clinical pharmacological and toxicological studies.
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He J, Zhou Y, Xing J, Wang Q, Zhu H, Zhu Y, Zou MH. Liver kinase B1 is required for thromboxane receptor-dependent nuclear factor-κB activation and inflammatory responses. Arterioscler Thromb Vasc Biol 2013; 33:1297-305. [PMID: 23539217 DOI: 10.1161/atvbaha.113.301296] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
OBJECTIVE Thromboxane A2 receptor (TPr) has been reported to trigger vascular inflammation. Nuclear factor κ B (NF-κB) is a known transcription factor. The aims of the present study were to determine the contributions of NF-κB activation to TPr-triggered vascular inflammation and elucidate the mechanism(s) underlying TPr activation of NF-κB. APPROACH AND RESULTS The effects of TPr activators, [1S-[1 alpha,2 alpha(Z),3beta(1E,3S*), 4 alpha]]-7-[3-[3-hydroxy-4-(4-iodophenoxy)-1-butenyl]-7-oxabicyclo[2.2.1]hept-2-yl]-5-heptenoic acid (I-BOP) and U46619, on NF-κB activation, phosphorylation of rhoA/rho-associated kinases and liver kinase B1, cell adhesion and migration, proliferation, and endothelium-dependent vasorelaxation were assayed in cultured human umbilical vein endothelial cells, human monocytes, or isolated mouse aortas. Exposure of human umbilical vein endothelial cells to TPr agonists I-BOP and U46619 induced dose-dependent and time-dependent phosphorylation of inhibitor of κB α in parallel with aberrant expression of inflammatory markers cyclooxygenase-2, inducible nitric oxide synthase, intercellular adhesion molecule-1, and vascular cell adhesion molecule-1. Inhibition of NF-κB by pharmacological or genetic means abolished TPr-triggered expression of inflammatory markers. Consistently, exposure of human umbilical vein endothelial cells to either I-BOP or U46619 significantly increased phosphorylation of inhibitor of κB α, I kappaB kinase, rhoA, rho-associated kinases, and liver kinase B1. Pretreatment of human umbilical vein endothelial cells with the TPr antagonist SQ29548 or rho-associated kinases inhibitor Y27632 or silencing of the LKB1 blocked TPr-enhanced phosphorylation of inhibitor of κB α and its upstream kinase, I kappaB kinase. Finally, exposure of isolated mouse aortas to either U46619 or I-BOP enhanced NF-κB activation and vascular inflammation in parallel with reduced endothelium-dependent relaxation in intact vessels. CONCLUSIONS TPr stimulation instigates aberrant inflammation and endothelial dysfunction via rho-associated kinases/liver kinase B1/I kappaB kinase-dependent NF-κB activation in vascular endothelial cells.
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Affiliation(s)
- Jinlong He
- Department of Physiology and Pathophysiology, Peking University Health Science Center, Beijing, China
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Involvement of lipid rafts in multiple signal transductions mediated by two isoforms of thromboxane A₂ receptor: dependency on receptor isoforms and downstream signaling types. Eur J Pharmacol 2012; 693:15-24. [PMID: 22963705 DOI: 10.1016/j.ejphar.2012.07.046] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2011] [Revised: 07/13/2012] [Accepted: 07/27/2012] [Indexed: 11/21/2022]
Abstract
Lipid rafts, microdomains in the plasma membrane, are known to be involved in G protein-coupled receptor signal transduction; however, their involvement in thromboxane A(2) receptor (TP) signaling remains to be clarified. We examined whether two isoforms of TP, TPα and TPβ, utilize lipid rafts for multiple G protein signal transduction. Sucrose density gradient centrifugation followed by western blotting of HEK cells expressing TPα or TPβ revealed the localization of both TPα and TPβ in lipid rafts. Furthermore, methyl-β-cyclodextrin, which destroys lipid raft structure by depleting cholesterol, influenced G protein signaling elicited by TPα and TPβ to varying degrees. Phosphatidylinositol hydrolysis and cAMP accumulation induced by TPα or TPβ stimulation was markedly inhibited by methyl-β-cyclodextrin. In contrast, treatment with methyl-β-cyclodextrin partially inhibited RhoA activation induced by TPα stimulation, but failed to affect TPβ stimulation. Furthermore, the inhibitory action of methyl-β-cyclodextrin on cAMP accumulation was specific to TPα and TPβ, because methyl-β-cyclodextrin enhanced forskolin and β-adrenergic stimulation-induced cAMP accumulation. These results indicate that TP isoforms depend on lipid rafts during G(q) and G(s) signaling, while G(13) signaling mediated by TP isoforms does not. Moreover, TPα seems to be more lipid raft-dependent with respect to RhoA activation than TPβ. These results indicate that the two isoforms of the TP mediate multiple signal transductions with varying degrees of lipid raft dependency. Moreover, our results provide a deeper understanding of the function of lipid rafts in G protein signaling and the physiological meaning of TP isoforms.
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Ambrosio M, Fanelli F, Brocchetti S, Raimondi F, Mauri M, Rovati GE, Capra V. Superactive mutants of thromboxane prostanoid receptor: functional and computational analysis of an active form alternative to constitutively active mutants. Cell Mol Life Sci 2010; 67:2979-89. [PMID: 20383734 PMCID: PMC11115618 DOI: 10.1007/s00018-010-0368-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2009] [Revised: 03/22/2010] [Accepted: 03/25/2010] [Indexed: 12/13/2022]
Abstract
In class A GPCRs the E/DRY motif is critical for receptor activation and function. According to experimental and computational data, R3.50 forms a double salt bridge with the adjacent E/D3.49 and E/D6.30 in helix 6, constraining the receptor in an inactive state. The disruption of this network of interactions facilitates conformational transitions that generate a signal or constitutive activity. Here we demonstrate that non-conservative substitution of either E129((3.49)) or E240((6.30)) of thromboxane prostanoid receptor (TP) resulted in mutants characterized by agonist-induced more efficient signaling properties, regardless of the G protein coupling. Results of computational modeling suggested a more effective interaction between G(q) and the agonist-bound forms of the TP mutants, compared to the wild type. Yet, none of the mutants examined revealed any increase in basal activity, precluding their classification as constitutively active mutants. Here, we propose that these alternative active conformations might be identified as superactive mutants or SAM.
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Affiliation(s)
- Manuela Ambrosio
- Laboratory of Molecular Pharmacology, Department of Pharmacological Sciences, Università degli Studi di Milano, Via Balzaretti 9, 20133 Milan, Italy
| | - Francesca Fanelli
- Department of Chemistry and Dulbecco Telethon Institute, Università di Modena e Reggio Emilia, Modena, Italy
| | - Silvia Brocchetti
- Laboratory of Molecular Pharmacology, Department of Pharmacological Sciences, Università degli Studi di Milano, Via Balzaretti 9, 20133 Milan, Italy
| | - Francesco Raimondi
- Department of Chemistry and Dulbecco Telethon Institute, Università di Modena e Reggio Emilia, Modena, Italy
| | - Mario Mauri
- Department of Experimental Medicine, Università di Milano-Bicocca, Monza, Italy
| | - G. Enrico Rovati
- Laboratory of Molecular Pharmacology, Department of Pharmacological Sciences, Università degli Studi di Milano, Via Balzaretti 9, 20133 Milan, Italy
| | - Valérie Capra
- Laboratory of Molecular Pharmacology, Department of Pharmacological Sciences, Università degli Studi di Milano, Via Balzaretti 9, 20133 Milan, Italy
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14
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Chillar A, Wu J, Cervantes V, Ruan KH. Structural and Functional Analysis of the C-Terminus of Gαq in Complex with the Human Thromboxane A2 Receptor Provides Evidence of Constitutive Activity. Biochemistry 2010; 49:6365-74. [DOI: 10.1021/bi100047n] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Annirudha Chillar
- Center for Experimental Therapeutics and Pharmacoinformatics, Department of Pharmacological and Pharmaceutical Sciences, University of Houston, Houston, Texas 77204
| | - Jiaxin Wu
- Center for Experimental Therapeutics and Pharmacoinformatics, Department of Pharmacological and Pharmaceutical Sciences, University of Houston, Houston, Texas 77204
| | - Vanessa Cervantes
- Center for Experimental Therapeutics and Pharmacoinformatics, Department of Pharmacological and Pharmaceutical Sciences, University of Houston, Houston, Texas 77204
| | - Ke-He Ruan
- Center for Experimental Therapeutics and Pharmacoinformatics, Department of Pharmacological and Pharmaceutical Sciences, University of Houston, Houston, Texas 77204
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15
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Wacker MJ, Kosloski LM, Gilbert WJR, Touchberry CD, Moore DS, Kelly JK, Brotto M, Orr JA. Inhibition of thromboxane A2-induced arrhythmias and intracellular calcium changes in cardiac myocytes by blockade of the inositol trisphosphate pathway. J Pharmacol Exp Ther 2009; 331:917-24. [PMID: 19741149 DOI: 10.1124/jpet.109.157677] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
We have recently reported that left atrial injections of the thromboxane A(2) (TXA(2)) mimetic, (5Z)-7-[(1R,4S,5S,6R)-6-[(1E,3S)-3-hydroxy-1-octenyl]-2 -oxabicyclo[2.2.1]hept-5-yl]-5-heptenoic acid (U46619), induced ventricular arrhythmias in the anesthetized rabbit. Data from this study led us to hypothesize that TXA(2) may be inducing direct actions on the myocardium to induce these arrhythmias. The aim of this study was to further elucidate the mechanism responsible for these arrhythmias. We report that TXA(2)R is expressed at both the gene and protein levels in atrial and ventricular samples of adult rabbits. In addition, TXA(2)R mRNA was identified in single, isolated ventricular cardiac myocytes. Furthermore, treatment of isolated cardiac myocytes with U46619 increased intracellular calcium in a dose-dependent manner and these increases were blocked by the specific TXA(2)R antagonist, 7-(3-((2-((phenylamino)carbonyl)hydrazino)methyl)-7-oxabicyclo(2.2.1)hept-2-yl)-5-heptenoic acid (SQ29548). Pretreatment of myocytes with an inhibitor of inositol trisphosphate (IP(3)) formation, gentamicin, or with an inhibitor of IP(3) receptors, 2-aminoethoxydiphenylborate (2-APB), blocked the increase in intracellular calcium. In vivo pretreatment of anesthetized rabbits with either gentamicin or 2-APB subsequently inhibited the formation of ventricular arrhythmias elicited by U46619. These data support the hypothesis that TXA(2) can induce arrhythmias via a direct action on cardiac myocytes. Furthermore, these arrhythmogenic actions were blocked by inhibitors of the IP(3) pathway. In summary, this study provides novel evidence for direct TXA(2)-induced cardiac arrhythmias and provides a rationale for IP(3) as a potential target for the treatment of TXA(2)-mediated arrhythmias.
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Affiliation(s)
- M J Wacker
- Muscle Biology Research Group, School of Medicine, University of Missouri-Kansas City, Kansas City, Missouri 64108, USA.
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16
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Reid HM, Kinsella BT. Intermolecular cross-talk between the prostaglandin E2 receptor (EP)3 of subtype and thromboxane A(2) receptor signalling in human erythroleukaemic cells. Br J Pharmacol 2009; 158:830-47. [PMID: 19702786 DOI: 10.1111/j.1476-5381.2009.00351.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND AND PURPOSE In previous studies investigating cross-talk of signalling between prostaglandin (PG)E(2) receptor (EP) and the TPalpha and TPbeta isoforms of the human thromboxane (TX)A(2) receptor (TP), 17-phenyl trinor PGE(2)-induced desensitization of TP receptor signalling through activation of the AH6809 and SC19220-sensitive EP(1) subtype of the EP receptor family, in a cell-specific manner. Here, we sought to further investigate that cross-talk in human erythroleukaemic (HEL) 92.1.7 cells. EXPERIMENTAL APPROACH Specificity of 17-phenyl trinor PGE(2) signalling and its possible cross-talk with signalling by TPalpha/TPbeta receptors endogenously expressed in HEL cells was examined through assessment of agonist-induced inositol 1,4,5-trisphosphate (IP)(3) generation and intracellular calcium ([Ca(2+)](i)) mobilization. KEY RESULTS While 17-Phenyl trinor PGE(2) led to activation of phospholipase (PL)Cbeta to yield increases in IP(3) generation and [Ca(2+)](i), it did not desensitize but rather augmented that signalling in response to subsequent stimulation with the TXA(2) mimetic U46619. Furthermore, the augmentation was reciprocal. Signalling by 17-phenyl trinor PGE(2) was found to occur through AH6809- and SC19920-insensitive, Pertussis toxin-sensitive, G(i)/G(betagamma)-dependent activation of PLCbeta. Further pharmacological investigation using selective EP receptor subtype agonists and antagonists confirmed that 17-phenyl trinor PGE(2)-mediated signalling and reciprocal cross-talk with the TP receptors occurred through the EP(3), rather than the EP(1), EP(2) or EP(4) receptor subtype in HEL cells. CONCLUSIONS AND IMPLICATIONS The EP(1) and EP(3) subtypes of the EP receptor family mediated intermolecular cross-talk to differentially regulate TP receptor-mediated signalling whereby activation of EP(1) receptors impaired or desensitized, while that of EP(3) receptors augmented signalling through TPalpha/TPbeta receptors, in a cell type-specific manner.
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Affiliation(s)
- Helen M Reid
- Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin, Ireland
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17
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Pfister SL. Characterization of endothelial thromboxane receptors in rabbit aorta. Prostaglandins Other Lipid Mediat 2008; 87:54-61. [PMID: 18812232 DOI: 10.1016/j.prostaglandins.2008.08.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2007] [Revised: 08/12/2008] [Accepted: 08/26/2008] [Indexed: 01/16/2023]
Abstract
An increased synthesis of thromboxane (TX) A(2) is associated with a number of cardiovascular diseases including atherosclerosis, unstable angina and hypertension. We previously identified a subgroup of NZW rabbits in which isolated arteries failed to contract to the TX agonists, U46619 or I-BOP. In vascular smooth muscle membranes, there was a significant decrease in TX receptors, termed TP. These rabbits are referred to as vTP- and those with the TP receptor are called vTP+. Because TP receptors are expressed in some types of endothelial cells, the present study was designed to determine whether functional TP receptors are present in endothelial cells cultured from aortas of vTP+ and vTP- rabbits. Radioligand binding studies were performed with (125)I-BOP. Aortic endothelial cells from vTP+ rabbits exhibited specific and saturable binding. In contrast, in endothelial preparations from vTP- rabbit aortas, no measurable binding to (125)I-BOP was detected. Using an anti-TP receptor antibody, we compared the amount of receptor expressed in endothelial cell lysates obtained from vTP+ and vTP- rabbits. Consistent with the results observed radioligand binding assays, the expression of TP receptor protein was decreased in vTP- compared to vTP+ endothelial cells. An in vitro wound healing assay was used on confluent monolayers of endothelial cells. In the untreated vTP+ cells, the area of the scratch was completely closed by 30 h. In the vTP+ cells treated with U46619 (3 microM), the rate of closure of the scratch area was reduced with approximately 12% of the scratch area remaining at 30 h. Pretreatment with the TP receptor antagonist, SQ 29548 (10 microM) prevented the inhibitory effect of U46619. The rate of closure of the scratch in the vTP- was not altered by U46619. In a separate study, U46619 (3 microM) increased the release of 6-keto PGF(1alpha), the stable metabolite of prostacyclin, in vTP+ but not vTP- endothelial cells. Pretreatment with SQ29548 (10 microM) or the cyclooxygenase inhibitor, indomethacin (10 microM) blocked the increase in vTP+ endothelial cells. In vascular reactivity studies in aortas from vTP+ rabbits, removal of the endothelium enhanced the vasoconstrictor response to U46619 indicating that activation of endothelial TP receptors may modulate vascular tone via the release of the vasodilator, prostacyclin. The results of this study suggest an important role for endothelial TP receptors in modulating vascular function.
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Affiliation(s)
- Sandra L Pfister
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
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18
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Gannon AM, Kinsella BT. Regulation of the human thromboxane A2 receptor gene by Sp1, Egr1, NF-E2, GATA-1, and Ets-1 in megakaryocytes. J Lipid Res 2008; 49:2590-604. [PMID: 18698092 DOI: 10.1194/jlr.m800256-jlr200] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The alpha and beta isoforms of the human thromboxane A(2) (TXA(2)) receptor (TP) are encoded by a single gene but are transcriptionally regulated by distinct promoters, termed promoter 1 (Prm1) and Prm3, respectively. Herein, it was sought to identify factors regulating Prm1 within the megakaryocytic human erythroleukemia 92.1.7 cell line. Through gene deletion and reporter assays, the core Prm1 was localized to between nucleotides -6,320 and -5,895, proximal to the transcription initiation site. Furthermore, two upstream repressor and two upstream activator regions were identified. Site-directed mutagenesis of four overlapping Sp1/Egr1 elements and an NF-E2/AP1 element within the proximal region substantially reduced Prm1 activity. Deletion/mutation of GATA and Ets elements disrupted the upstream activator sequence located between -7,962 and -7,717, significantly impairing Prm1 activity. Electrophoretic mobility shift assays and chromatin immunoprecipitations confirmed that Sp1, Egr1, and NF-E2 bind to elements within the core promoter, whereas GATA-1 and Ets-1 factors bind to the upstream activator sequence (between -7,962 and -7,717). Collectively, these data establish that Sp1, Egr1, and NF-E2 regulate core Prm1 activity in the megakaryocytic-platelet progenitor cells, whereas GATA-1 and Ets-1 act as critical upstream activators, hence providing the first genetic basis for the expression of the human TXA(2) receptor (TP) within the vasculature.
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Affiliation(s)
- AnneMarie M Gannon
- University College Dublin School of Biomolecular and Biomedical Sciences, University College Dublin Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland
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19
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Kelley-Hickie LP, O'Keeffe MB, Reid HM, Kinsella BT. Homologous desensitization of signalling by the alpha (alpha) isoform of the human thromboxane A2 receptor: a specific role for nitric oxide signalling. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2007; 1773:970-89. [PMID: 17466390 PMCID: PMC2680961 DOI: 10.1016/j.bbamcr.2007.03.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/23/2007] [Revised: 03/14/2007] [Accepted: 03/15/2007] [Indexed: 01/16/2023]
Abstract
Thromboxane (TX) A2 plays a central role in hemostasis, regulating platelet activation status and vascular tone. We have recently established that the TPβ isoform of the human TXA2 receptor (TP) undergoes rapid, agonist-induced homologous desensitization of signalling largely through a G protein-coupled receptor kinase (GRK) 2/3-dependent mechanism with a lesser role for protein kinase (PK) C. Herein, we investigated the mechanism of desensitization of signalling by the TPα isoform. TPα undergoes profound agonist-induced desensitization of signalling (intracellular calcium mobilization and inositol 1,4,5 trisphosphate generation) in response to the TXA2 mimetic U46619 but, unlike that of TPβ, this is independent of GRKs. Similar to TPβ, TPα undergoes partial agonist-induced desensitization that occurs through a GF 109203X-sensitive, PKC mechanism where Ser145 within intracellular domain (IC)2 represents the key phospho-target. TPα also undergoes more profound sustained PKC- and PKG-dependent desensitization where Thr337 and Ser331, respectively, within its unique C-tail domain were identified as the phospho-targets. Desensitization was impaired by the nitric oxide synthase (NOS), soluble guanylyl cyclase (sGC) and PKG inhibitors l-NAME, LY 83583 and KT5823, respectively, indicating that homologous desensitization of TPα involves nitric oxide generation and signalling. Consistent with this, U46619 led to rapid phosphorylation/activation of endogenous eNOS. Collectively, data herein suggest a mechanism whereby agonist-induced PKC phosphorylation of Ser145 partially and transiently impairs TPα signalling while PKG- and PKC-phosphorylation at both Ser331 and Thr337, respectively, within its C-tail domain profoundly desensitizes TPα, effectively terminating its signalling. Hence, in addition to the agonist-mediated PKC feedback mechanism, U46619-activation of the NOS/sGC/PKG pathway plays a significant role in inducing homologous desensitization of TPα.
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MESH Headings
- 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid/pharmacology
- Calcium Signaling/drug effects
- Calcium Signaling/physiology
- Cell Line
- Cyclic GMP-Dependent Protein Kinases/antagonists & inhibitors
- Cyclic GMP-Dependent Protein Kinases/metabolism
- Enzyme Inhibitors/pharmacology
- G-Protein-Coupled Receptor Kinase 2
- G-Protein-Coupled Receptor Kinase 3
- Hemostasis/drug effects
- Hemostasis/physiology
- Humans
- Indoles/pharmacology
- Inositol 1,4,5-Trisphosphate/metabolism
- Maleimides/pharmacology
- Nitric Oxide/metabolism
- Nitric Oxide Synthase Type III/metabolism
- Platelet Activation/drug effects
- Platelet Activation/physiology
- Protein Isoforms/agonists
- Protein Isoforms/genetics
- Protein Isoforms/metabolism
- Protein Kinase C/antagonists & inhibitors
- Protein Kinase C/metabolism
- Protein Structure, Tertiary/genetics
- Receptors, Thromboxane A2, Prostaglandin H2/agonists
- Receptors, Thromboxane A2, Prostaglandin H2/genetics
- Receptors, Thromboxane A2, Prostaglandin H2/metabolism
- Thromboxane A2/metabolism
- Vasoconstrictor Agents/pharmacology
- beta-Adrenergic Receptor Kinases/metabolism
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20
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Reid HM, Kinsella BT. Palmitoylation of the TPbeta isoform of the human thromboxane A2 receptor. Modulation of G protein: effector coupling and modes of receptor internalization. Cell Signal 2006; 19:1056-70. [PMID: 17229546 PMCID: PMC2680975 DOI: 10.1016/j.cellsig.2006.12.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2006] [Revised: 12/05/2006] [Accepted: 12/05/2006] [Indexed: 11/28/2022]
Abstract
Palmitoylation is a prevalent feature amongst G protein-coupled receptors. In this study we sought to establish whether the TPα and TPβ isoforms of the human prostanoid thromboxane (TX) A2 receptor (TP) are palmitoylated and to assess the functional consequences thereof. Consistent with the presence of three cysteines within its unique carboxyl-terminal domain, metabolic labelling and site-directed mutagenesis confirmed that TPβ is palmitoylated at Cys347 and, to a lesser extent, at Cys373,377 whereas TPα is not palmitoylated. Impairment of palmitoylation did not affect TPβ expression or its ligand affinity. Conversely, agonist-induced [Ca2+]i mobilization by TPβC347S and the non-palmitoylated TPβC347,373,377S, but not by TPβC373S or TPβC373,377S, was significantly reduced relative to the wild type TPβ suggesting that palmitoylation at Cys347 is specifically required for efficient Gq/phospholipase Cβ effector coupling. Furthermore, palmitoylation at Cys373,377 is critical for TPβ internalization with TPβC373S, TPβC373,377S and TPβC347,373,377S failing to undergo either agonist-induced or temperature-dependent tonic internalization. On the other hand, whilst TPβC347S underwent reduced agonist-induced internalization, it underwent tonic internalization to a similar extent as TPβ. The deficiency in agonist-induced internalization by TPβC347S, but not by TPβC373,377 nor TPβC347,373,377S, was overcome by over-expression of either β-arrestin1 or β-arrestin2. Taken together, data herein suggest that whilst palmitoylation of TPβ at Cys373,377 is critical for both agonist- and tonic-induced internalization, palmitoylation at Cys347 has a role in determining which pathway is followed, be it by the β-arrestin-dependent agonist-induced pathway or by the β-arrestin-independent tonic internalization pathway.
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21
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Dassesse T, de Leval X, de Leval L, Pirotte B, Castronovo V, Waltregny D. Activation of the Thromboxane A2 Pathway in Human Prostate Cancer Correlates with Tumor Gleason Score and Pathologic Stage. Eur Urol 2006; 50:1021-31; discussion 1031. [PMID: 16522350 DOI: 10.1016/j.eururo.2006.01.036] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2005] [Accepted: 01/15/2006] [Indexed: 11/29/2022]
Abstract
OBJECTIVE We investigated the potential involvement of the thromboxane A(2) (TXA(2)) pathway in human prostate cancer (PCa). METHODS Expression of cyclooxygenase-2 (COX-2), TXA(2) synthase (TXS), and TXA(2) receptors (TPRs), the main actors of the TXA(2) pathway, was analyzed on serial tissue sections from 46 human PCa specimens. RESULTS The expression levels of COX-2, TXS, and TPRs were significantly higher in malignant than in corresponding nontumoral prostatic epithelial cells. Increased immunoreactivity for these antigens was also observed in high-grade prostate intraepithelial neoplasia (HGPIN) glands. COX-2, TXS, and TPR proteins usually displayed a coordinated overexpression pattern in PCa lesions, as assessed in serial tissue sections. Increased levels of these proteins in the tumors were all significantly associated with higher Gleason scores and pathologic stages. CONCLUSIONS Proteins specifically involved in the TXA(2) pathway are up-regulated in human PCa and their level of expression is associated with tumor extraprostatic extension and loss of differentiation. Our study is the first to examine simultaneously all key proteins involved in this pathway including TXA(2) receptors and results suggest that the TXA(2) pathway may be a potential target for PCa prevention/therapy.
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Affiliation(s)
- Thibaut Dassesse
- Metastasis Research Laboratory, Center of Experimental Cancer Research, University of Liège, B-4000 Liège, Belgium
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22
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Kelley-Hickie LP, Kinsella BT. Homologous desensitization of signalling by the beta (β) isoform of the human thromboxane A2 receptor. Biochim Biophys Acta Mol Cell Biol Lipids 2006; 1761:1114-31. [PMID: 16956790 DOI: 10.1016/j.bbalip.2006.07.012] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2006] [Revised: 07/26/2006] [Accepted: 07/27/2006] [Indexed: 10/24/2022]
Abstract
Thromboxane (TX) A(2) is a potent stimulator of platelet activation/aggregation and smooth muscle contraction and contributes to a variety of pathologies within the vasculature. In this study, we investigated the mechanism whereby the cellular responses to TXA(2) mediated through the TPbeta isoform of the human TXA(2) receptor (TP) are dynamically regulated by examining the mechanism of agonist-induced desensitization of intracellular signalling and second messenger generation by TPbeta. It was established that TPbeta is subject to profound agonist-induced homologous desensitization of signalling (intracellular calcium mobilization and inositol 1,3,5 trisphosphate generation) in response to stimulation with the TXA(2) mimetic U46619 and this occurs through two key mechanisms: TPbeta undergoes partial agonist-induced desensitization that occurs through a GF 109203X-sensitive, protein kinase (PK)C mechanism whereby Ser(145) within intracellular domain (IC)(2) has been identified as the key phospho-target. In addition, TPbeta also undergoes more profound and sustained agonist-induced desensitization involving G protein-coupled receptor kinase (GRK)2/3-phosphorylation of both Ser(239) and Ser(357) within its IC(3) and carboxyl-terminal C-tail domains, respectively. Inhibition of phosphorylation of either Ser(239) or Ser(357), through site directed mutagenesis, impaired desensitization while mutation of both Ser(239) and Ser(357) almost completely abolished desensitization of signalling, GRK phosphorylation and beta-arrestin association, thereby blocking TPbeta internalization. These data suggest a model whereby agonist-induced PKC phosphorylation of Ser(145) partially impairs. TPbeta signalling while GRK2/3 phosphorylation at both Ser(239) and Ser(357) within its IC(3) and C-tail domains, respectively, sterically inhibits G-protein coupling, profoundly desensitizing signalling, and promotes beta-arrestin association and, in turn, facilitates TPbeta internalization. Thromboxane (TX) A(2) is a potent stimulator of platelet aggregation and smooth muscle contraction and contributes to a variety of vascular pathologies. Herein the mechanism whereby the cellular responses to TXA(2) mediated through the TPbeta isoform of the human TXA(2) receptor (TP) are dynamically regulated was investigated by examining the mechanism of its agonist-induced desensitization of intracellular signalling and second messenger generation. TPbeta is subject to profound agonist-induced homologous desensitization of signalling (intracellular calcium mobilization and inositol 1,3,5 trisphosphate generation) in response to stimulation with the TXA(2) mimetic U46619 and this occurs through two key mechanisms: TPbeta undergoes partial agonist-induced desensitization that occurs through a GF 109203X-sensitive, protein kinase (PK)C mechanism whereby Ser(145) within intracellular domain (IC)(2) was identified as the key phospho-target. In addition, TPbeta also undergoes more profound and sustained agonist-induced desensitization involving G protein-coupled receptor kinase (GRK)2/3-phosphorylation of both Ser(239) and Ser(357) within its IC(3) and carboxyl-terminal C-tail domains, respectively. Inhibition of phosphorylation of either Ser(239) or Ser(357), through site directed mutagenesis, impaired desensitization while mutation of both Ser(239) and Ser(357) almost completely abolished desensitization of signalling, GRK phosphorylation and beta-arrestin association, thereby blocking TPbeta internalization. These data suggest a model whereby agonist-induced PKC phosphorylation of Ser(145) partially impairs TPbeta signalling while GRK2/3 phosphorylation at both Ser(239) and Ser(357) within its IC(3) and C-tail domains, respectively, sterically inhibits G-protein coupling, profoundly desensitizing signalling, and promotes beta-arrestin association and, in turn, facilitates TPbeta internalization.
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MESH Headings
- 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid/pharmacology
- Amino Acid Sequence
- Arrestins/metabolism
- Calcium/metabolism
- Cell Line
- G-Protein-Coupled Receptor Kinase 3
- Humans
- Indoles/pharmacology
- Inositol 1,4,5-Trisphosphate/analogs & derivatives
- Inositol 1,4,5-Trisphosphate/metabolism
- Maleimides/pharmacology
- Molecular Sequence Data
- Mutagenesis, Site-Directed
- Phosphorylation
- Protein Isoforms/agonists
- Protein Isoforms/antagonists & inhibitors
- Protein Isoforms/metabolism
- Protein Kinase C/antagonists & inhibitors
- Protein Kinase C/metabolism
- Protein Serine-Threonine Kinases/metabolism
- Protein Structure, Tertiary
- Receptors, Thromboxane A2, Prostaglandin H2/agonists
- Receptors, Thromboxane A2, Prostaglandin H2/antagonists & inhibitors
- Receptors, Thromboxane A2, Prostaglandin H2/metabolism
- Second Messenger Systems
- Serine/metabolism
- Signal Transduction
- beta-Arrestins
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Affiliation(s)
- Leanne P Kelley-Hickie
- School of Biomolecular and Biomedical Science, Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland
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23
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Miyosawa K, Sasaki M, Ohkubo S, Nakahata N. Different Pathways for Activation of Extracellular Signal-Regulated Kinase through Thromboxane A2 Receptor Isoforms. Biol Pharm Bull 2006; 29:719-24. [PMID: 16595906 DOI: 10.1248/bpb.29.719] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Thromboxane A2 receptor (TP) consists of two alternatively spliced isoforms, TPalpha and TPbeta, which differ in their cytoplasmic tails. In the present study, we examined the difference in signal transduction of TPalpha and TPbeta, using stably expressing cells of TPalpha and TPbeta. The cells expressing TPalpha (TPalpha-SC2) and TPbeta (TPbeta-SC15) were selected based on the similar binding sites of [3H]-SQ29548, a TP antagonist. U46619, a TP agonist, elicited phosphoinositide hydrolysis in TPalpha-SC2 and TPbeta-SC15 cells with a similar concentration-dependency. U46619 also caused the phosphorylation of extracellular signal-regulated kinase (ERK1/2) in both TPalpha-SC2 and TPbeta-SC15 cells. While the peak of the phosphorylation of ERK1/2 was observed 5 min after addition of U46619 in TPalpha-SC2 cells, the long lasting phosphorylation up to 60 min was in TPbeta-SC15 cells. U46619-induced phosphorylation of ERK1/2 at 5 min was inhibited by pertussis toxin in both cells, suggesting that G(i) is involved in the phosphorylation mediated via both TP isoforms. Interfering G(12/13) activity by overexpression of p115-RGS reduced U46619-induced ERK1/2 phosphorylation in TPbeta-SC15 cells, but not in TPalpha-SC2 cells. H89, an inhibitor of protein kinase A (PKA), reduced U46619-induced ERK1/2 phosphorylation in TPalpha-SC2 cells, but not in TPbeta-SC15 cells. These results indicate that G(i) may be involved in TP-mediated ERK1/2 phosphorylation in both isoforms. In addition, H89-sensitive kinase and G(12/13) may be involved in TP-mediated ERK1/2 phosphorylation in TPalpha and TPbeta, respectively.
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MESH Headings
- 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid/pharmacology
- Adenoviridae/genetics
- Animals
- Blotting, Western
- CHO Cells
- Cricetinae
- Enzyme Activation
- Extracellular Signal-Regulated MAP Kinases/genetics
- Extracellular Signal-Regulated MAP Kinases/metabolism
- Genetic Vectors
- Hydrolysis
- Isomerism
- Isoquinolines/pharmacology
- Pertussis Toxin/pharmacology
- Phosphatidylinositols/metabolism
- Plasmids/genetics
- Receptors, Cell Surface/drug effects
- Receptors, Thromboxane A2, Prostaglandin H2/drug effects
- Receptors, Thromboxane A2, Prostaglandin H2/genetics
- Receptors, Thromboxane A2, Prostaglandin H2/physiology
- Reverse Transcriptase Polymerase Chain Reaction
- Sulfonamides/pharmacology
- Vasoconstrictor Agents/pharmacology
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Affiliation(s)
- Katsutoshi Miyosawa
- Department of Cellular Signaling, Graduate School of Pharmaceutical Sciences, Tohoku University, Aramaki, Sendai, Japan
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24
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Quiniou C, Sennlaub F, Beauchamp MH, Checchin D, Lahaie I, Brault S, Gobeil F, Sirinyan M, Kooli A, Hardy P, Pshezhetsky A, Chemtob S. Dominant Role for Calpain in Thromboxane-Induced Neuromicrovascular Endothelial Cytotoxicity. J Pharmacol Exp Ther 2005; 316:618-27. [PMID: 16214879 DOI: 10.1124/jpet.105.093898] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Thromboxane A(2) (TXA(2)) is an important lipid mediator generated during oxidative stress and implicated in ischemic neural injury. This autacoid was recently shown to partake in this injury process by directly inducing endothelial cytotoxicity. We explored the mechanisms for this TXA(2)-evoked neural microvascular endothelial cell death. Stable TXA(2) mimetics 5-heptenoic acid, 7-[6-(3-hydroxy-1-octenyl)-2-oxabicyclo[2.2.1]hept-5-yl]-[1R-[1alpha,4alpha,5beta(Z),6alpha,(1E,3S)]]-9,11-dedioxy-9alpha,11alpha-methanolpoxy (U-46619) [as well as [1S-[1alpha,2alpha(Z),3beta(1E,3S(*)),4alpha]]-7-[3-[3-hydroxy-4-(4-iodophenoxy)-1-butenyl]-7-oxabicyclo[2.1.1]-hept-2-yl]-5-heptenoic acid; I-BOP] induced a retinal microvascular degeneration in rat pups in vivo and in porcine retinal explants ex vivo and death of porcine brain endothelial cells (in culture). TXA(2) dependence of these effects was corroborated by antagonism using the selective TXA(2) receptor blocker (-)-6,8-difluoro-9-p-methyl-sulfonyl-benzyl-1,2,3,4-tetrahydrocarbazol-1-yl-acetic acid (L670596). In all cases, neurovascular endothelial cell death was prevented by pan-calpain and specific m-calpain inhibitors but not by caspase-3 or pan-caspase inhibitors. Correspondingly, TXA(2) (mimetics) augmented generation of known active m-calpain (but not mu-calpain) form and increased the activity of m-calpain (cleavage of fluorogenic substrate N-succinyl-Leu-Leu-Val-Tyr-7-amino-4-methylcoumarin; and of alpha-spectrin into specific fragments) but not of pan-caspase or specific caspase-3 (respectively, using sulforhodamine-Val-Arg-Asp-fluoromethyl ketone and detecting its active 17- and 12-kDa fragments). Interestingly, these effects were phospholipase C (PLC)-dependent [associated with increase in inositol triphosphate and inhibited by PLC blocker 1-[6-[[17beta-methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-1H-pyrrole-2,5-dione (U73122)] and required calcium but were not associated with increased intracellular calcium. U-46619-induced calpain activation resulted in translocation of Bax to the mitochondria, loss of polarization of the latter (using potentiometric probe 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolyl-carbocyanine iodide; JC-1) and in turn release of cytochrome c into the cytosol and depletion of cellular ATP; these effects were all blocked by calpain inhibitors. Overall, this work identifies (specifically) m-calpain as a dominant protease in TXA(2)-induced neurovascular endothelial cell death.
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Affiliation(s)
- Christiane Quiniou
- Department of Pediatrics, Centre de Recherche de l'Hôpital Ste-Justine, Université de Montréal, Québec, Canada
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25
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Kukkonen JP. Regulation of receptor-coupling to (multiple) G proteins. A challenge for basic research and drug discovery. ACTA ACUST UNITED AC 2005; 10:167-83. [PMID: 15989081 DOI: 10.3109/10606820490926151] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
G protein-coupled receptors induce intracellular signals via interaction of with cytosolic/peripheral membrane proteins, mainly G proteins. There has been much debate about the mode of interaction between the receptors, G proteins and effectors, their mobility and the ways of determining the specificity of interaction. Additional complexity has been added to system upon the discovery of i) coupling of single receptors to several G proteins and ii) active direction of this by different ligands (stimulus trafficking). These data suggest that the most primary unit in the signal transduction is the receptor complexed with a specific G protein, making the investigation of the mechanism of receptor-G protein selection and interaction even more important. In this review, I will summarize the general knowledge of receptor interaction with G proteins and effectors and the ways of investigating this.
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Affiliation(s)
- Jyrki P Kukkonen
- Department of Neuroscience, Physiology, Uppsala University, Uppsala, Sweden.
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26
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Valentin F, Tippins JR, Field MC. The role of alternative splicing and C-terminal amino acids in thromboxane receptor stabilization. Biochem Biophys Res Commun 2005; 329:898-904. [PMID: 15752740 DOI: 10.1016/j.bbrc.2005.02.058] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2005] [Indexed: 10/25/2022]
Abstract
The thromboxane receptor has two alternatively spliced isoforms, alpha and beta, which differ only in sequences within the cytoplasmic C-terminal domain. Oxidative stress induced by H(2)O(2) in a COS-7 cell model results in stabilization of the thromboxane receptor beta isoform by translocation from the endoplasmic reticulum to the Golgi complex, which in turn results in protection of the receptor from degradation. We now report that both the alpha and beta thromboxane receptor isoforms respond identically to oxidative stress. Further, mutagenesis studies indicate that replacing the normal C-terminus with a nonsense sequence also does not alter stabilization behaviour ruling out a role for the distinct C-termini in this process. Further mutagenesis implicates a cluster of arginine residues within the C-terminal domain as involved in oxidative stress-induced stabilization. These data identify a region of the thromboxane receptor that is responsible for responding to oxidative challenge and open the possibility of identification of the molecular machinery underpinning this response.
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Affiliation(s)
- François Valentin
- Division of Cell and Molecular Biology, Biochemistry Building, Imperial College, London SW7 2AZ, UK
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27
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Hata AN, Breyer RM. Pharmacology and signaling of prostaglandin receptors: multiple roles in inflammation and immune modulation. Pharmacol Ther 2005; 103:147-66. [PMID: 15369681 DOI: 10.1016/j.pharmthera.2004.06.003] [Citation(s) in RCA: 599] [Impact Index Per Article: 31.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Prostaglandins are lipid-derived autacoids that modulate many physiological systems including the CNS, cardiovascular, gastrointestinal, genitourinary, endocrine, respiratory, and immune systems. In addition, prostaglandins have been implicated in a broad array of diseases including cancer, inflammation, cardiovascular disease, and hypertension. Prostaglandins exert their effects by activating rhodopsin-like seven transmembrane spanning G protein-coupled receptors (GPCRs). The prostanoid receptor subfamily is comprised of eight members (DP, EP1-4, FP, IP, and TP), and recently, a ninth prostaglandin receptor was identified-the chemoattractant receptor homologous molecule expressed on Th2 cells (CRTH2). The precise roles prostaglandin receptors play in physiologic and pathologic settings are determined by multiple factors including cellular context, receptor expression profile, ligand affinity, and differential coupling to signal transduction pathways. This complexity is highlighted by the diverse and often opposing effects of prostaglandins within the immune system. In certain settings, prostaglandins function as pro-inflammatory mediators, but in others, they appear to have anti-inflammatory properties. In this review, we will discuss the pharmacology and signaling of the nine known prostaglandin GPCRs and highlight the specific roles that these receptors play in inflammation and immune modulation.
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MESH Headings
- Humans
- Inflammation/metabolism
- Phylogeny
- Prostaglandins/physiology
- Receptors, Epoprostenol/genetics
- Receptors, Epoprostenol/metabolism
- Receptors, Immunologic/genetics
- Receptors, Immunologic/metabolism
- Receptors, Prostaglandin/genetics
- Receptors, Prostaglandin/metabolism
- Receptors, Prostaglandin E/genetics
- Receptors, Prostaglandin E/metabolism
- Receptors, Thromboxane A2, Prostaglandin H2/genetics
- Receptors, Thromboxane A2, Prostaglandin H2/metabolism
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Affiliation(s)
- Aaron N Hata
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, USA
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28
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Wilson SJ, Roche AM, Kostetskaia E, Smyth EM. Dimerization of the human receptors for prostacyclin and thromboxane facilitates thromboxane receptor-mediated cAMP generation. J Biol Chem 2004; 279:53036-47. [PMID: 15471868 DOI: 10.1074/jbc.m405002200] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Prostacyclin (PGI(2)) and thromboxane (TxA(2)) are biological opposites; PGI(2), a vasodilator and inhibitor of platelet aggregation, limits the deleterious actions of TxA(2), a vasoconstrictor and platelet activator. The molecular mechanisms involved in the counterregulation of PGI(2)/TxA(2) signaling are unclear. We examined the interaction of the receptors for PGI(2) (IP) and TxA(2) (TPalpha). IP-induced cAMP and TP-induced inositol phosphate generation were unaltered when the receptors were co-expressed in HEK 293 cells (IP/TPalpha-HEK). TP-cAMP generation, in response to TP agonists or a TP-dependent isoprostane, iPE(2)III, was evident in IP/TPalpha-HEK and in aortic smooth muscle cells, but not in cells expressing either receptor alone, or in IP-deficient aortic smooth muscle cells. Augmentation of TP-induced cAMP generation, with the IP agonist cicaprost, was ablated in IP-deficient cells and was independent of direct IP signaling. IP/TPalpha heterodimers were formed constitutively when the receptors were co-expressed, with no overt changes in ligand binding to the individual receptor sites. However, despite inefficient binding of iPE(2)III to either the IP or TPalpha, expressed alone or in combination, robust cAMP generation was evident in IP/TPalpha-HEK, suggesting the formation of an alternative receptor site. Thus, IP/TPalpha dimerization was coincident with TP-cAMP generation, promoting a "PGI(2)-like" cellular response to TP activation. This represents a previously unknown mechanism by which IP may limit the cellular effects of TP.
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Affiliation(s)
- Stephen J Wilson
- Center for Experimental Therapeutics, University of Pennsylvania, 421 Curie Blvd., Philadelphia, PA 19104, USA
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29
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Ashton AW, Ware JA. Thromboxane A2 receptor signaling inhibits vascular endothelial growth factor-induced endothelial cell differentiation and migration. Circ Res 2004; 95:372-9. [PMID: 15242977 DOI: 10.1161/01.res.0000138300.41642.15] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Vascular endothelial growth factor (VEGF) is an important patho-physiological mediator of angiogenesis. VEGF-induced endothelial cell (EC) migration and angiogenesis often occur in complicated environments containing multiple agents capable of modifying the response. Thromboxane (TX) A2 is released from multiple cell types and is a prime mediator of pathogenesis of many vascular diseases. Human EC express both TXA2 receptor (TP) isoforms; however, the effects of individual TP isoforms on VEGF-induced EC migration and angogenesis are unknown. We report here that the TXA2 mimetic [1S-(1alpha, 2beta(5Z), 3alpha(1E, 3R), 4alpha]-7-[3-(3-hydroxy-4-(4'-iodophenoxy)-1-butenyl)-7-oxab icyclo-[2.2.1]heptan-2yl]-5'-heptenoic acid (IBOP) (100 nmol/L) is a potent antagonist (IC50 30 nmol/L) of VEGF-induced EC migration and differentiation. TPbeta, but not TPalpha, expression is required for the inhibition of VEGF-induced migration and angiogenesis. IBOP costimulation suppressed nitric oxide (NO) release from VEGF-treated EC through decreased activation of Akt, eNOS, and PDK1. TPbeta costimulation also ablated the increase in focal adhesion formation in response to VEGF. This mechanism was characterized by decreased recruitment of focal adhesion kinase (FAK) and vinculin to the alpha(v)beta3 integrin and reduced FAK and Src activation in response to VEGF. Addition of NO donors together with transfection of a constitutively active Src construct could circumvent the blockade of VEGF-induced migration by TP; however, neither intervention alone was sufficient. Thus, TP stimulation appears to limit angiogenesis, at least in part, by inhibiting the pro-angiogenic cytokine VEGF. These data further support a role for antagonism of TP activation in enhancing the angiogenic response in tissues exposed to elevated TXA2 levels in which revascularization is important.
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MESH Headings
- 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid/pharmacology
- Animals
- Bridged Bicyclo Compounds, Heterocyclic/pharmacology
- Capillaries/cytology
- Cell Movement/drug effects
- Endothelial Cells/cytology
- Endothelial Cells/drug effects
- Endothelial Cells/metabolism
- Endothelium, Vascular/cytology
- Endothelium, Vascular/drug effects
- Fatty Acids, Unsaturated
- Focal Adhesions/drug effects
- Humans
- Hydrazines/pharmacology
- Neovascularization, Physiologic/drug effects
- Nitric Oxide/metabolism
- Nitric Oxide Donors/pharmacology
- Phosphorylation/drug effects
- Protein Isoforms/antagonists & inhibitors
- Protein Isoforms/drug effects
- Protein Isoforms/physiology
- Protein Kinases/genetics
- Protein Kinases/physiology
- Protein Processing, Post-Translational/drug effects
- Rats
- Receptors, Thromboxane A2, Prostaglandin H2/antagonists & inhibitors
- Receptors, Thromboxane A2, Prostaglandin H2/drug effects
- Receptors, Thromboxane A2, Prostaglandin H2/physiology
- Recombinant Proteins/pharmacology
- Signal Transduction/drug effects
- Transfection
- Umbilical Veins
- Vascular Endothelial Growth Factor A/pharmacology
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Affiliation(s)
- Anthony W Ashton
- Department of Medicine (Cardiology), Albert Einstein College of Medicine, Yeshiva University, 1300 Morris Park Ave, Bronx, NY 10461, USA.
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30
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Kelley-Hickie LP, Kinsella BT. EP1- and FP-mediated cross-desensitization of the alpha (alpha) and beta (beta) isoforms of the human thromboxane A2 receptor. Br J Pharmacol 2004; 142:203-21. [PMID: 15100160 PMCID: PMC1574916 DOI: 10.1038/sj.bjp.0705695] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1. Heterologous desensitization or intermolecular cross-talk plays a critical role in regulating intracellular signalling by diverse members of the G-protein-coupled receptor superfamily. We have previously established that the alpha and beta isoforms of the human thromboxane A(2) receptor (TP) undergo differential desensitization of signalling in response to 17 phenyl trinor prostaglandin (PG)E(2), an agonist of the EP(1) subtype of the PGE(2) receptor (EP) family. 2. Herein, we investigated the molecular basis of TPalpha and TPbeta desensitization in human embryonic kidney (HEK) 293 cells and in renal mesangial cells in response to 17 phenyl trinor PGE(2) and in response to the PGF(2alpha) receptor (FP) agonist PGF(2alpha), and sought to identify the target site(s) of those desensitizations. 3. Our results demonstrated that TPalpha and TPbeta receptors are subject to desensitization in response to both EP(1) and FP receptor activation and that these effects are mediated by direct protein kinase (PK)C phosphorylation of the individual TP isoforms within their unique carboxyl-terminal (C)-tail domains. 4. Moreover, deletion/site-directed mutagenesis and metabolic labelling studies identified Thr(337), within TPalpha, and Thr(399), within TPbeta, as the specific target residues for PKC phosphorylation and EP(1)- and FP-mediated desensitization of TPalpha and TPbeta signalling, respectively. 5. Hence, in conclusion, while the TPalpha and TPbeta diverge within their C-tail domains, they have evolved to share a similar mechanism of PKC-induced phosphorylation and desensitization in response to EP(1) and FP receptor activation, though it occurs at sites unique to the individual TP isoforms.
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MESH Headings
- 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid/pharmacology
- Amino Acid Sequence
- Cell Line
- Humans
- Molecular Sequence Data
- Protein Isoforms/genetics
- Protein Isoforms/metabolism
- Receptors, Prostaglandin/genetics
- Receptors, Prostaglandin/metabolism
- Receptors, Prostaglandin E/genetics
- Receptors, Prostaglandin E/metabolism
- Receptors, Prostaglandin E, EP1 Subtype
- Receptors, Thromboxane A2, Prostaglandin H2/genetics
- Receptors, Thromboxane A2, Prostaglandin H2/metabolism
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Affiliation(s)
- Leanne P Kelley-Hickie
- Department of Biochemistry, Conway Institute of Biomolecular and Biomedical Research, Merville House, University College Dublin, Belfield, Dublin 4, Ireland
| | - B Therese Kinsella
- Department of Biochemistry, Conway Institute of Biomolecular and Biomedical Research, Merville House, University College Dublin, Belfield, Dublin 4, Ireland
- Author for correspondence:
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31
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Geng L, Wu J, So SP, Huang G, Ruan KH. Structural and functional characterization of the first intracellular loop of human thromboxane A2 receptor. Arch Biochem Biophys 2004; 423:253-65. [PMID: 15001390 DOI: 10.1016/j.abb.2004.01.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2003] [Indexed: 11/19/2022]
Abstract
The conformation of a constrained peptide mimicking the putative first intracellular domain (iLP1) of thromboxane A(2) receptor (TP) was determined by (1)H 2D NMR spectroscopy. Through completed assignments of TOCSY, DQF-COSY, and NOESY spectra, a NMR structure of the peptide showed a beta-turn in residues 56-59 and a short helical structure in the residues 63-66. It suggests that residues 63-66 may be part of the second transmembrane domain (TM), and that Arg60, in an exposed position on the outer surface of the loop, may be involved in signaling through charge contact with Gq protein. The sequence alignment of Lys residue in the same position of other prostanoid receptors mediates different G protein couplings, suggesting that the chemical properties of Arg and Lys may also affect the receptor signaling activity. These hypotheses were supported by mutagenesis studies, in which the mutant of Arg60Leu completely lost activity in increasing intracellular calcium level through Gq coupling, and the mutant of Arg60Lys retained only about 35% signaling activity. The difference between the side chain functions of Lys and Arg in effecting the signaling was discussed.
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MESH Headings
- 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid/pharmacology
- Amino Acid Sequence
- Amino Acid Substitution
- Animals
- Arginine/genetics
- Arginine/metabolism
- COS Cells
- Calcium/metabolism
- Calcium Signaling/drug effects
- Calcium Signaling/physiology
- Circular Dichroism
- Humans
- Models, Molecular
- Nuclear Magnetic Resonance, Biomolecular
- Protein Binding
- Protein Structure, Secondary
- Protein Structure, Tertiary
- Receptors, Thromboxane A2, Prostaglandin H2/antagonists & inhibitors
- Receptors, Thromboxane A2, Prostaglandin H2/chemistry
- Receptors, Thromboxane A2, Prostaglandin H2/genetics
- Receptors, Thromboxane A2, Prostaglandin H2/metabolism
- Recombinant Proteins/chemistry
- Recombinant Proteins/genetics
- Recombinant Proteins/metabolism
- Sequence Alignment
- Sequence Homology, Amino Acid
- Transfection
- Vasoconstrictor Agents/pharmacology
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Affiliation(s)
- Linda Geng
- Vascular Biology Research Center and Division of Hematology, Department of Internal Medicine, The University of Texas Health Science Center, Houston, Texas 77030, USA
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32
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Reid HM, Kinsella BT. The α, but Not the β, Isoform of the Human Thromboxane A2 Receptor Is a Target for Nitric Oxide-mediated Desensitization. J Biol Chem 2003; 278:51190-202. [PMID: 14530262 DOI: 10.1074/jbc.m309314200] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In humans, thromboxane A2 signals through two thromboxane A2 receptor (TP) isoforms termed TP alpha and TP beta. Signaling by TP alpha, but not TP beta, is subject to prostacyclin-induced desensitization mediated by direct protein kinase (PK) A phosphorylation where Ser329 represents the phosphotarget (Walsh, M. T., Foley, J. F., and Kinsella, B. T. (2000) J. Biol. Chem. 275, 20412-20423). In the current study, the effect of the vasodilator nitric oxide (NO) on intracellular signaling by the TP isoforms was investigated. The NO donor 3-morpholinosydnonimine, HCl (SIN-1) and 8-bromo-guanosine 3',5'-cyclic monophosphate (8-Br-cGMP) functionally desensitized U46619-mediated calcium mobilization and inositol 1,4,5-trisphosphate generation by TP alpha whereas signaling by TP beta was unaffected by either agent. NO-mediated desensitization of TP alpha signaling occurred through a PKG-dependent, PKA- and PKC-independent mechanism. TP alpha, but not TP beta, was efficiently phosphorylated by PKG in vitro and underwent NO/PKG-mediated phosphorylation in whole cells. Deletion/site-directed mutagenesis and metabolic labeling studies identified Ser331 as the target residue of NO-induced PKG phosphorylation of TP alpha. Although TP alpha S331A was insensitive to NO/PKG-desensitization, similar to wild type TP alpha its signaling was fully desensitized by the prostacyclin receptor agonist cicaprost occurring through a PKA-dependent mechanism. Conversely, signaling by TP alpha S329A was insensitive to cicaprost stimulation whereas it was fully desensitized by NO/PKG signaling. In conclusion, TP alpha undergoes both NO- and prostacyclin-mediated desensitization that occur through entirely independent mechanisms involving direct PKG phosphorylation of Ser331, in response to NO, and PKA phosphorylation of Ser329, in response to prostacyclin, within the unique carboxyl-terminal tail domain of TP alpha. On the other hand, signaling by TP beta is unaffected by either NO or prostacyclin.
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Affiliation(s)
- Helen M Reid
- Department of Biochemistry, Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland
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33
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Ashton AW, Ware GM, Kaul DK, Ware JA. Inhibition of tumor necrosis factor alpha-mediated NFkappaB activation and leukocyte adhesion, with enhanced endothelial apoptosis, by G protein-linked receptor (TP) ligands. J Biol Chem 2003; 278:11858-66. [PMID: 12517920 DOI: 10.1074/jbc.m210766200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Tumor necrosis factor (TNF) alpha is a critical mediator of inflammation; however, TNFalpha is rarely released alone and the "cross-talk" between different classes of inflammatory mediators is largely unexplored. Thromboxane A(2) (TXA(2)) is released during I/R injury and exerts its effects via a G protein-linked receptor (TP). In this study, we found that TXA(2) mimetics stimulate leukocyte adhesion molecule (LAM) expression on endothelium via TPbeta. The potential interaction between TXA(2) and TNFalpha in altering endothelial survival and LAM expression was examined. IBOP, a TXA(2) mimetic, attenuated TNFalpha-induced LAM expression in vitro, in a concentration-dependent manner, by preventing TNFalpha-enhanced gene expression, and also reduced TNFalpha-induced leukocyte adhesion to endothelium both in vitro and in vivo. IBOP abrogated TNFalpha-induced NFkappaB activation in endothelial cells, as determined by reduced IkappaB phosphorylation and NFkappaB nuclear translocation, by inhibiting the assembly of signaling intermediates with the intracellular domain of TNF receptors 1 and 2 in response to TNFalpha. This inhibition resulted from the Galpha(q)-mediated enhancement of STAT1 activation and was reversed by anti-STAT1 antisense oligonucleotides. TNFalpha-mediated TNFR1-FADD association and caspase 8 activation were not inhibited by IBOP co-stimulation, however, resulting in a 2.6-fold increase in endothelial cell apoptosis. By stimulating the vessel wall and inducing endothelial cell apoptosis, TXA(2), in combination with TNFalpha, may hamper the angiogenic response during inflammation or ischemia, thus reducing revascularization and tissue viability.
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Affiliation(s)
- Anthony W Ashton
- Department of Medicine, Albert Einstein College of Medicine, Yeshiva University, Bronx, New York 10461, USA
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34
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Coyle AT, Miggin SM, Kinsella BT. Characterization of the 5' untranslated region of alpha and beta isoforms of the human thromboxane A2 receptor (TP). Differential promoter utilization by the TP isoforms. EUROPEAN JOURNAL OF BIOCHEMISTRY 2002; 269:4058-73. [PMID: 12180983 DOI: 10.1046/j.1432-1033.2002.03098.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In humans, thromboxane (TX) A2 signals through two TXA2 receptor (TP) isoforms, TPalpha and TPbeta, that diverge within their carboxyl terminal cytoplasmic (C) tail regions and arise by differential splicing. The human TP gene contains three exons E1-E3; while E1 exclusively encodes 5' untranslated region (UTR) sequence, E2 and E3 represent the main coding exons. An additional noncoding exon, E1b was identified within intron 1. Additionally, the TP gene contains two promoters P1 and P2 located 5' of E1 and E1b, respectively. Herein, we investigated the molecular basis of the differential expression of the TP isoforms by characterizing the 5' UTR of the TP transcripts. While E1 and E1b were found associated with TP transcript(s), their expression was mutually exclusive. 5' rapid amplification of cDNA ends (5' RACE) established that the major transcription initiation (TI) sites were clustered between -115 and -92 within E1 and at -99 within E1b. While E1 and E1b sequences were identified on TPalpha transcript(s), neither existed on TPbeta transcript(s). More specifically, TPalpha and TPbeta transcripts diverged within E2 and the major TI sites for TPbeta transcripts mapped to -12/-15 therein. Through genetic reporter assays, a previously unrecognized promoter, termed P3, was identified on the TP gene located immediately 5' of -12. The proximity of P3 to the TI site of TPbeta suggests a role for P3 in the control of TPbeta expression and implies that TPalpha and TPbeta, in addition to being products of differential splicing, are under the transcriptional control of distinct promoters.
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Affiliation(s)
- Adrian T Coyle
- Department of Biochemistry, University College Dublin, Ireland
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35
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Miggin SM, Kinsella BT. Investigation of the mechanisms of G protein: effector coupling by the human and mouse prostacyclin receptors. Identification of critical species-dependent differences. J Biol Chem 2002; 277:27053-64. [PMID: 12016224 DOI: 10.1074/jbc.m203353200] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We recently identified a novel mechanism explaining how the mouse (m) prostacyclin receptor (IP) couples to Galpha(s), Galpha(i), and Galpha(q) (Lawler, O. A., Miggin, S. M., and Kinsella, B. T. (2001) J. Biol. Chem. 276, 33596-33607) whereby mIP coupling to Galpha(i) and Galpha(q) is dependent on its initial coupling to Galpha(s) and subsequent phosphorylation by cAMP-dependent protein kinase A (PKA) on Ser(357). In the current study, the generality of that mechanism was investigated by examining the G protein coupling specificity of the human (h) IP. The hIP efficiently coupled to Galpha(s)/adenylyl cyclase and to Galpha(q)/phospholipase C activation but failed to couple to Galpha(i). Coupling of the hIP to Galpha(q), or indeed to Galpha(s) or Galpha(i), was unaffected by the PKA or protein kinase C (PKC) inhibitors H-89 and GF 109203X, respectively. Thus, mIP and hIP exhibit essential differences in their coupling to Galpha(i) and in their dependence on PKA in regulating their coupling to Galpha(q). Analysis of their primary sequences revealed that the critical PKA phosphorylation site within the mIP, at Ser(357), is replaced by a PKC site within the hIP, at Ser(328). Conversion of the PKC site of the hIP to a PKA site generated hIP(QL325,326RP) that efficiently coupled to Galpha(s) and to Galpha(i) and Galpha(q); coupling of hIP(QL325,326RP) to Galpha(i) but not to Galpha(s) or Galpha(q) was inhibited by H-89. Abolition of the PKC site of the hIP generated hIP(S328A) that efficiently coupled to Galpha(s) and Galpha(q) but failed to couple to Galpha(i). Finally, conversion of the PKA site at Ser(357) within the mIP to a PKC site generated mIP(RP354,355QL) that efficiently coupled to Galpha(s) but not to Galpha(i) or Galpha(q). Collectively, our data highlight critical differences in signaling by the mIP and hIP that are regulated by their differential phosphorylation by PKA and PKC together with contextual sequence differences surrounding those sites.
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Affiliation(s)
- Sinead M Miggin
- Department of Biochemistry, Conway Institute of Biomolecular and Biomedical Research, Merville House, University College Dublin, Belfield, Dublin 4, Ireland
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36
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Foley JF, Kelley LP, Kinsella BT. Prostaglandin D(2) receptor-mediated desensitization of the alpha isoform of the human thromboxane A(2) receptor. Biochem Pharmacol 2001; 62:229-39. [PMID: 11389883 DOI: 10.1016/s0006-2952(01)00661-x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Thromboxane (TX) A(2) and prostaglandin (PG) D(2) mediate opposing actions in platelets and in vascular and non-vascular smooth muscle. Here, we investigated the effects of stimulation of the PGD(2) receptor (DP) on signaling by the TXA(2) receptor (TP) expressed in human platelets and in human embryonic kidney (HEK) 293 cells over-expressing the individual TP alpha and TP beta isoforms. In platelets, the selective DP agonist BW245C abolished TP-mediated mobilization of intracellular calcium ([Ca(2+)](i)) and inhibited platelet aggregation in response to the TXA(2) mimetic U46619. DP-mediated desensitization of TP signaling in platelets was prevented by pretreatment with the cAMP-dependent PKA inhibitor, H-89, but was unaffected by the PKC inhibitor GF 109203X. In HEK 293 cells, signaling by TP alpha, but not TP beta, was subject to DP-mediated desensitization in a PKA-dependent, PKC-independent manner. U46619-induced signaling by TP(Delta 328), a truncated variant of TP containing only those residues common to TP alpha and TP beta, was insensitive to prior DP stimulation, indicating that the carboxyl terminal tail of TPalpha contains the target site(s) for DP-mediated desensitization. Mutation of Ser(329) to Ala(329) within a consensus PKA site in TP alpha rendered the mutant TP alpha(S329A) insensitive to BW245C-mediated desensitization. Whole cell phosphorylation assays established that TP alpha, but not TP beta or TP alpha(S329A), was subject to DP-mediated phosphorylation and that TP alpha phosphorylation was blocked by the PKA inhibitor H-89. These data establish that TP alpha, but not TP beta, is subject to DP-mediated cross desensitization, which occurs through direct PKA-mediated phosphorylation of TP alpha at Ser(329).
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MESH Headings
- 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid/pharmacology
- Blood Platelets/drug effects
- Blood Platelets/metabolism
- Cells, Cultured
- Humans
- Hydantoins/pharmacology
- Inositol 1,4,5-Trisphosphate/metabolism
- Phosphorylation
- Protein Isoforms/physiology
- Receptor Cross-Talk/physiology
- Receptors, Immunologic
- Receptors, Prostaglandin/antagonists & inhibitors
- Receptors, Prostaglandin/metabolism
- Receptors, Prostaglandin/physiology
- Receptors, Thromboxane/physiology
- Signal Transduction
- Vasoconstrictor Agents/pharmacology
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Affiliation(s)
- J F Foley
- Department of Biochemistry, Conway Institute of Biomolecular and Biomedical Research, Merville House, University College Dublin, Belfield, Dublin 4, Ireland
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Miggin SM, Kinsella BT. Thromboxane A(2) receptor mediated activation of the mitogen activated protein kinase cascades in human uterine smooth muscle cells. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1539:147-62. [PMID: 11389977 DOI: 10.1016/s0167-4889(01)00103-3] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Both thromboxane (TX) A(2) and 8-epi prostaglandin (PG) F(2alpha) have been reported to stimulate mitogenesis of vascular smooth muscle (SM) in a number of species. However, TXA(2) and 8-epiPGF(2alpha) mediated mitogenic signalling has not been studied in detail in human vascular SM. Thus, using the human uterine ULTR cell line as a model, we investigated TXA(2) receptor (TP) mediated mitogenic signalling in cultured human vascular SMCs. Both the TP agonist U46619 and 8-epiPGF(2alpha) elicited time and concentration dependent activation of the extracellular signal regulated kinase (ERK)s and c-Jun N-terminal kinase (JNK)s in ULTR cells. Whereas the TP antagonist SQ29548 abolished U46619 mediated signalling, it only partially inhibited 8-epiPGF(2alpha) mediated ERK and JNK activation in ULTR cells. Both U46619 and 8-epiPGF(2alpha) induced ERK activations were inhibited by the protein kinase (PK) C, PKA and phosphoinositide 3-kinase inhibitors GF109203X, H-89 and wortmannin, respectively, but were unaffected by pertussis toxin. In addition, U46619 mediated ERK activation in ULTR cells involves transactivation of the epidermal growth factor (EGF) receptor. In humans, TXA(2) signals through two distinct TP isoforms. In investigating the involvement of the TP isoforms in mitogenic signalling, both TPalpha and TPbeta independently directed U46619 and 8-epiPGF(2alpha) mediated ERK and JNK activation in human embryonic kidney (HEK) 293 cells over-expressing the individual TP isoforms. However, in contrast to that which occurred in ULTR cells, SQ29548 abolished 8-epiPGF(2alpha) mediated ERK and JNK activation through both TPalpha and TPbeta in HEK 293 cells providing further evidence that 8-epiPGF(2alpha) may signal through alternative receptors, in addition to the TPs, in human uterine ULTR cells.
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Affiliation(s)
- S M Miggin
- Department of Biochemistry, Conway Institute of Biomolecular and Biomedical Research, Merville House, University College Dublin, Belfield, 4, Dublin, Ireland
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Lawler OA, Miggin SM, Kinsella BT. The effects of the statins lovastatin and cerivastatin on signalling by the prostanoid IP-receptor. Br J Pharmacol 2001; 132:1639-49. [PMID: 11309234 PMCID: PMC1572747 DOI: 10.1038/sj.bjp.0704033] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
The prostanoid-IP receptor may be unique among G protein coupled receptors in that it is isoprenylated. In this study, we investigated the effects of the statins lovastatin and cerivastatin on signalling by the mouse (m) IP and the human (h) IP receptors, over-expressed in human embryonic kidney (HEK) 293 cells and by the hIP receptor, endogenously expressed in human erythroleukaemia cells. Both statins significantly reduced IP receptor-mediated cyclic AMP generation and intracellular calcium ([Ca(2+)](i)) mobilization in a time and concentration dependent manner but had no effect on signalling by the non-isoprenylated beta(2) adrenergic receptor or by the human prostanoid-TP receptor isoforms. Cerivastatin (IC(50), 50 - 90 nM) was significantly more potent than lovastatin (IC(50), 0.80 - 4.2 microM) in inhibiting IP receptor signalling. Whereas IC(50) values indicated that the hIP receptor was significantly more sensitive than the mIP receptor to the statins, the extent of inhibition of cyclic AMP generation by the mIP receptor was significantly greater than that of the hIP receptor to either statin, even at the highest concentrations used. Pretreatment with either statin significantly reduced IP receptor mediated desensitization of signalling by the h.TPalpha, but not by the h.TPbeta, receptor isoform. These data generated in whole cells point to the possibility that statin therapy may interfere with IP receptor signalling in vivo; such interference may be extenuated under conditions where circulating statin levels are elevated and may account, in part, for some of the pleiotropic affects of the statins not attributed solely to their lipid lowering properties.
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Affiliation(s)
- Orlaith A Lawler
- Department of Biochemistry, Conway Institute of Biomolecular and Biomedical Research, Merville House, University College Dublin, Belfield, Dublin 4, Ireland
| | - Sinead M Miggin
- Department of Biochemistry, Conway Institute of Biomolecular and Biomedical Research, Merville House, University College Dublin, Belfield, Dublin 4, Ireland
| | - B Therese Kinsella
- Department of Biochemistry, Conway Institute of Biomolecular and Biomedical Research, Merville House, University College Dublin, Belfield, Dublin 4, Ireland
- Author for correspondence:
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Angeles DM, Williams J, Purdy RE, Zhang L, Pearce WJ. Effects of maturation and acute hypoxia on receptor-IP(3) coupling in ovine common carotid arteries. Am J Physiol Regul Integr Comp Physiol 2001; 280:R410-7. [PMID: 11208569 DOI: 10.1152/ajpregu.2001.280.2.r410] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Whereas previous studies have established that many mechanisms mediating pharmacomechanical coupling are subject to regulation, evidence of physiological regulation of the coupling efficiency between receptor activation and second-messenger production is scarce. The present studies address the hypothesis that acute hypoxia and maturation can influence the mass of second-messenger production for each activated agonist-bound receptor ("receptor gain"). For this assessment, receptor density and agonist affinity values were used to calculate 5-hydroxytryptamine (5-HT) concentrations that would produce standardized numbers of bound receptors (8.5 fmol/mg protein) in each experimental group and thus minimize effects of age or hypoxia on receptor density or agonist affinity. After 3 min of exposure to these 5-HT concentrations, normoxic magnitudes of contraction were similar (as %potassium maxima) in fetal (50 +/- 14%) and adult (40 +/- 9%) arteries, but hypoxia (PO(2) approximately 9--12 Torr for 30 min) depressed contractile tensions with a significantly different time course and magnitude in fetal (30 +/- 10%) and adult (17 +/- 11%) arteries (P < 0.05). Basal inositol 1,4,5-trisphosphate (IP(3)) values (in pmol/mg protein) were significantly greater in fetal (94 +/- 16) than in adult (44 +/- 6) arteries, and integrated areas above baseline for the IP(3) time courses (in nmol-s/mg protein) were significantly greater in fetal than in adult arteries both in normoxic (14.3 +/- 1.8 vs. 9.1 +/- 1.6) and hypoxic (15.0 +/- 2.1 vs. 8.6 +/- 1.2) conditions (P < 0.05). Hypoxia altered the IP(3) time courses both in the fetus and the adult but had no significant effect on IP(3 )mobilization or receptor gain. These data demonstrate that for the 5-HT(2a) receptor predominant in this preparation, receptor gain can be experimentally determined, is not influenced by acute hypoxia, but is greater in fetal than in adult ovine carotid arteries.
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MESH Headings
- Animals
- Calcium Channels/drug effects
- Calcium Channels/physiology
- Carotid Artery, Common/drug effects
- Carotid Artery, Common/embryology
- Carotid Artery, Common/physiology
- Female
- Fetal Hypoxia/physiopathology
- Fetus/physiology
- Gestational Age
- Hypoxia/physiopathology
- Inositol 1,4,5-Trisphosphate/physiology
- Inositol 1,4,5-Trisphosphate Receptors
- Male
- Muscle Contraction/drug effects
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/embryology
- NG-Nitroarginine Methyl Ester/pharmacology
- Pregnancy
- Receptor Cross-Talk/drug effects
- Receptor Cross-Talk/physiology
- Receptors, Cytoplasmic and Nuclear/drug effects
- Receptors, Cytoplasmic and Nuclear/physiology
- Second Messenger Systems/physiology
- Serotonin/pharmacology
- Serotonin/physiology
- Sheep
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Affiliation(s)
- D M Angeles
- Center for Perinatal Biology, Department of Physiology, Loma Linda University School of Medicine, Loma Linda, California 92350, USA
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Walsh MT, Kinsella BT. Regulation of the human prostanoid TPalpha and TPbeta receptor isoforms mediated through activation of the EP(1) and IP receptors. Br J Pharmacol 2000; 131:601-9. [PMID: 11015313 PMCID: PMC1572368 DOI: 10.1038/sj.bjp.0703624] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The intermolecular cross-regulation mediated by the prostanoid IP-receptor (IP)/EP(1) receptor (EP(1)) agonists PGI(2) and 17 phenyl trinor PGE(2) on TP receptor (TP) signalling within platelets was compared to that which occurs to the individual TPalpha and TPbeta receptors over-expressed in human embryonic kidney (HEK) 293 cells. Ligand mediated TP receptor activation was monitored by analysing mobilization of intracellular calcium ([Ca(2+)](i)) following stimulation with the selective thromboxane (TX) A(2) mimetic U46619. Consistent with previous studies, in platelets, PGI(2) acting through endogenous IP receptors completely inhibited U46619-mediated TP receptor signalling in a protein kinase (PK) A-dependent, PKC-independent manner. In HEK 293 cells, PGI(2), acting through endogenous AH6809 sensitive EP(1) rather than IP receptors, and the selective EP(1) receptor agonist 17 phenyl trinor PGE(2) antagonized U46619-mediated signalling by both TPalpha and TPbeta receptors in a PKC-dependent, PKA-independent manner. The maximum response induced by either ligand was significantly (P<0.005) greater for the TPalpha receptor than the TPbeta receptor, pointing to possible physiologic differences between the TP isoforms, although the potency of each ligand was similar for both TP receptors. TP(Delta328), a truncated variant of TP receptor lacking the C-tail sequences unique to TPalpha or TPbeta receptors, was not sensitive to EP(1) receptor-mediated regulation by PGI(2) or 17 phenyl trinor PGE(2) In conclusion, these data confirm that TPalpha and TPbeta receptors are subject to cross regulation by EP(1) receptor signalling in HEK 293 cells mediated by PKC at sites unique to the individual TP receptors and that TPalpha receptor responses are significantly more reduced by EP(1) receptor regulation than those of the TPbeta receptor.
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MESH Headings
- 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid/pharmacology
- Biological Transport/drug effects
- Blood Platelets/drug effects
- Blood Platelets/metabolism
- Calcium/metabolism
- Cells, Cultured
- Dinoprostone/pharmacology
- Drug Interactions
- Enzyme Inhibitors/pharmacology
- Epoprostenol/pharmacology
- Humans
- Indoles/pharmacology
- Isoquinolines/pharmacology
- Maleimides/pharmacology
- Prostaglandin Antagonists/pharmacology
- Prostaglandins/metabolism
- Protein Isoforms/metabolism
- Receptors, Epoprostenol
- Receptors, Prostaglandin/metabolism
- Receptors, Prostaglandin E/metabolism
- Receptors, Prostaglandin E, EP1 Subtype
- Receptors, Thromboxane/antagonists & inhibitors
- Receptors, Thromboxane/metabolism
- Signal Transduction
- Sulfonamides
- Vasoconstrictor Agents/pharmacology
- Xanthenes/pharmacology
- Xanthones
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Affiliation(s)
- Marie-Therese Walsh
- Department of Biochemistry, Conway Institute of Biomolecular and Biomedical Research, Merville House, University College Dublin, Belfield, Dublin 4, Ireland
| | - B Therese Kinsella
- Department of Biochemistry, Conway Institute of Biomolecular and Biomedical Research, Merville House, University College Dublin, Belfield, Dublin 4, Ireland
- Author for correspondence:
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