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D’Andria Ursoleo J, Licheri M, Barucco G, Breggion S, De Simone F, Monaco F. Management of Microvascular Bleeding after On-Pump Cardiac Surgery in a Patient with Perioperative Diagnosis of Impairment of Platelet Responses to Adenosine Diphosphate: A Case Report and a Literature Review. J Clin Med 2023; 12:6372. [PMID: 37835016 PMCID: PMC10573189 DOI: 10.3390/jcm12196372] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 09/18/2023] [Accepted: 10/03/2023] [Indexed: 10/15/2023] Open
Abstract
BACKGROUND Impairment of platelet responses to adenosine diphosphate (ADP) is typified by mild to severe bleeding diathesis, easy bruising, excessive mucosal and post-operative bleeding. Patients lack full platelet activation and aggregation in response to ADP. Following research of the literature in Scopus, PubMed/MEDLINE, ScienceDirect, and the Cochrane Library, we report only 18 patients described to date with impaired platelet response to ADP, none of whom in the high bleeding-risk surgical setting or exploring potential therapeutic options. Data regarding population, putative genetic mutations, modes of inheritance, functional defects, and related clinical manifestations were retrieved from case series and case reports. CASE PRESENTATION A 40-year-old woman was scheduled for on-pump cardiac surgery. Her past medical history included episodes of spontaneous mucocutaneous hemorrhages of the mild entity since childhood. Multiple electrode aggregometry (MEA, Multiplate® Roche Diagnostics, Rotkreuz, Switzerland) was used to evaluate platelet response to thrombin-activated peptide-6 (TRAP), arachidonic acid (ASPI), and ADP. An inadequate platelet aggregation induced using a high concentration of ADP with normal TRAP and ASPI tests was detected preoperatively. Therefore, intravenous desmopressin (DVVAP) 0.3 μg/kg body weight was administered to manage microvascular bleeding developed after weaning from cardiopulmonary bypass (CPB). CONCLUSIONS Proper management of impaired platelet response to ADP requires a systematic assessment. The Multiplate analyzer is a valuable tool to promptly detect the disorder when a high clinical suspect is present and obtain insights during high bleeding-risk surgical procedures. DVVAP can be beneficial as first-line therapy in bleeding patients to improve platelet function.
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Affiliation(s)
- Jacopo D’Andria Ursoleo
- Department of Anesthesia and Intensive Care, IRCCS San Raffaele Scientific Institute, Via Olgettina 60, 20132 Milan, Italy; (J.D.U.); (M.L.); (G.B.); (F.D.S.)
| | - Margherita Licheri
- Department of Anesthesia and Intensive Care, IRCCS San Raffaele Scientific Institute, Via Olgettina 60, 20132 Milan, Italy; (J.D.U.); (M.L.); (G.B.); (F.D.S.)
| | - Gaia Barucco
- Department of Anesthesia and Intensive Care, IRCCS San Raffaele Scientific Institute, Via Olgettina 60, 20132 Milan, Italy; (J.D.U.); (M.L.); (G.B.); (F.D.S.)
| | - Sara Breggion
- San Raffaele Telethon Institute for Gene Therapy (SR-Tiget), IRCCS San Raffaele Scientific Institute, Via Olgettina 60, 20132 Milan, Italy;
| | - Francesco De Simone
- Department of Anesthesia and Intensive Care, IRCCS San Raffaele Scientific Institute, Via Olgettina 60, 20132 Milan, Italy; (J.D.U.); (M.L.); (G.B.); (F.D.S.)
| | - Fabrizio Monaco
- Department of Anesthesia and Intensive Care, IRCCS San Raffaele Scientific Institute, Via Olgettina 60, 20132 Milan, Italy; (J.D.U.); (M.L.); (G.B.); (F.D.S.)
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Abstract
In addition to the key role in hemostasis and thrombosis, platelets have also been wildly acknowledged as immune regulatory cells and involving in the pathogenesis of inflammation-related diseases. Since purine receptor P2Y12 plays a crucial role in platelet activation, P2Y12 antagonists such as clopidogrel, prasugrel, and ticagrelor have been widely used in cardiovascular diseases worldwide in recent decades due to their potent antiplatelet and antithrombotic effects. Meanwhile, the role of P2Y12 in inflammatory diseases has also been extensively studied. Relatively, there are few studies on the regulation of P2Y12. This review first summarizes the various roles of P2Y12 in the process of platelet activation, as well as downstream effects and signaling pathways; then introduces the effects of P2Y12 in inflammatory diseases such as sepsis, atherosclerosis, cancer, autoimmune diseases, and asthma; and finally reviews the current researches on P2Y12 regulation.
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Affiliation(s)
- Xiaohua Li
- Department of Infectious Diseases, The First Hospital of Jilin University, Changchun, 130021, Jilin, China
- Department of Pharmacology, School of Pharmacy, Jilin University, Fujin Road, Changchun, 130021, Jilin, China
| | | | - Xia Cao
- Department of Pharmacology, School of Pharmacy, Jilin University, Fujin Road, Changchun, 130021, Jilin, China.
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Mahmood A, Iqbal J. Purinergic receptors modulators: An emerging pharmacological tool for disease management. Med Res Rev 2022; 42:1661-1703. [PMID: 35561109 DOI: 10.1002/med.21888] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 03/16/2022] [Accepted: 05/04/2022] [Indexed: 11/10/2022]
Abstract
Purinergic signaling is mediated through extracellular nucleotides (adenosine 5'-triphosphate, uridine-5'-triphosphate, adenosine diphosphate, uridine-5'-diphosphate, and adenosine) that serve as signaling molecules. In the early 1990s, purines and pyrimidine receptors were cloned and characterized drawing the attention of scientists toward this aspect of cellular signaling. This signaling pathway is comprised of four subtypes of adenosine receptors (P1), eight subtypes of G-coupled protein receptors (P2YRs), and seven subtypes of ligand-gated ionotropic receptors (P2XRs). In current studies, the pathophysiology and therapeutic potentials of these receptors have been focused on. Various ligands, modulating the functions of purinergic receptors, are in current clinical practices for the treatment of various neurodegenerative disorders and cardiovascular diseases. Moreover, several purinergic receptors ligands are in advanced phases of clinical trials as a remedy for depression, epilepsy, autism, osteoporosis, atherosclerosis, myocardial infarction, diabetes, irritable bowel syndrome, and cancers. In the present study, agonists and antagonists of purinergic receptors have been summarized that may serve as pharmacological tools for drug design and development.
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Affiliation(s)
- Abid Mahmood
- Centre for Advanced Drug Research, COMSATS University Islamabad, Abbottabad, Pakistan
| | - Jamshed Iqbal
- Centre for Advanced Drug Research, COMSATS University Islamabad, Abbottabad, Pakistan
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Nurden P, Stritt S, Favier R, Nurden AT. Inherited platelet diseases with normal platelet count: phenotypes, genotypes and diagnostic strategy. Haematologica 2021; 106:337-350. [PMID: 33147934 PMCID: PMC7849565 DOI: 10.3324/haematol.2020.248153] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2020] [Accepted: 08/12/2020] [Indexed: 12/16/2022] Open
Abstract
Inherited platelet disorders resulting from platelet function defects and a normal platelet count cause a moderate or severe bleeding diathesis. Since the description of Glanzmann thrombasthenia resulting from defects of ITGA2B and ITGB3, new inherited platelet disorders have been discovered, facilitated by the use of high throughput sequencing and genomic analyses. Defects of RASGRP2 and FERMT3 responsible for severe bleeding syndromes and integrin activation have illustrated the critical role of signaling molecules. Important are mutations of P2RY12 encoding the major ADP receptor causal for an inherited platelet disorder with inheritance characteristics that depend on the variant identified. Interestingly, variants of GP6 encoding the major subunit of the collagen receptor GPVI/FcRγ associate only with mild bleeding. The numbers of genes involved in dense granule defects including Hermansky-Pudlak and Chediak Higashi syndromes continue to progress and are updated. The ANO6 gene encoding a Ca2+-activated ion channel required for phospholipid scrambling is responsible for the rare Scott syndrome and decreased procoagulant activity. A novel EPHB2 defect in a familial bleeding syndrome demonstrates a role for this tyrosine kinase receptor independent of the classical model of its interaction with ephrins. Such advances highlight the large diversity of variants affecting platelet function but not their production, despite the difficulties in establishing a clear phenotype when few families are affected. They have provided insights into essential pathways of platelet function and have been at the origin of new and improved therapies for ischemic disease. Nevertheless, many patients remain without a diagnosis and requiring new strategies that are now discussed.
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Affiliation(s)
| | - Simon Stritt
- Department of Immunology, Genetics and Pathology, Uppsala University, Uppsala
| | - Remi Favier
- French National Reference Center for Inherited Platelet Disorders, Armand Trousseau Hospital, Assistance Publique-Hôpitaux de Paris, Paris
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5
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Molecular pharmacology of P2Y receptor subtypes. Biochem Pharmacol 2020; 187:114361. [PMID: 33309519 DOI: 10.1016/j.bcp.2020.114361] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Revised: 12/06/2020] [Accepted: 12/07/2020] [Indexed: 02/06/2023]
Abstract
Professor Geoffrey Burnstock proposed the concept of purinergic signaling via P1 and P2 receptors. P2Y receptors are G-protein-coupled receptors (GPCRs) for extracellular adenine and uracil nucleotides. Eight mammalian P2Y receptor subtypes have been identified. They are divided into two subgroups (P2Y1, P2Y2, P2Y4, P2Y6, and P2Y11) and (P2Y12, P2Y13, and P2Y14). P2Y receptors are found in almost all cells and mediate responses in physiology and pathophysiology including pain and inflammation. The antagonism of platelet P2Y12 receptors by cangrelor, ticagrelor or active metabolites of the thienopyridine compounds ticlopidine, clopidogrel and prasugrel reduces the ADP-induced platelet aggregation in patients with thrombotic complications of vascular diseases. The nucleotide agonist diquafosol acting at P2Y2 receptors is used for the treatment of the dry eye syndrome. Structural information obtained by crystallography of the human P2Y1 and P2Y12 receptor proteins, site-directed mutagenesis and molecular modeling will facilitate the rational design of novel selective drugs.
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Antagonism of Protease-Activated Receptor 4 Protects Against Traumatic Brain Injury by Suppressing Neuroinflammation via Inhibition of Tab2/NF-κB Signaling. Neurosci Bull 2020; 37:242-254. [PMID: 33111257 DOI: 10.1007/s12264-020-00601-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Accepted: 07/19/2020] [Indexed: 12/23/2022] Open
Abstract
Traumatic brain injury (TBI) triggers the activation of the endogenous coagulation mechanism, and a large amount of thrombin is released to curb uncontrollable bleeding through thrombin receptors, also known as protease-activated receptors (PARs). However, thrombin is one of the most critical factors in secondary brain injury. Thus, the PARs may be effective targets against hemorrhagic brain injury. Since the PAR1 antagonist has an increased bleeding risk in clinical practice, PAR4 blockade has been suggested as a more promising treatment. Here, we explored the expression pattern of PAR4 in the brain of mice after TBI, and explored the effect and possible mechanism of BMS-986120 (BMS), a novel selective and reversible PAR4 antagonist on secondary brain injury. Treatment with BMS protected against TBI in mice. mRNA-seq analysis, Western blot, and qRT-PCR verification in vitro showed that BMS significantly inhibited thrombin-induced inflammation in astrocytes, and suggested that the Tab2/ERK/NF-κB signaling pathway plays a key role in this process. Our findings provide reliable evidence that blocking PAR4 is a safe and effective intervention for TBI, and suggest that BMS has a potential clinical application in the management of TBI.
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7
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Ibrahim-Kosta M, Alessi MC, Hezard N. Laboratory Techniques Used to Diagnose Constitutional Platelet Dysfunction. Hamostaseologie 2020; 40:444-459. [PMID: 32932546 DOI: 10.1055/a-1223-3306] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Platelets play a major role in primary hemostasis, where activated platelets form plugs to stop hemorrhaging in response to vessel injuries. Defects in any step of the platelet activation process can cause a variety of platelet dysfunction conditions associated with bleeding. To make an accurate diagnosis, constitutional platelet dysfunction (CPDF) should be considered once von Willebrand disease and drug intake are ruled out. CPDF may be associated with thrombocytopenia or a genetic syndrome. CPDF diagnosis is complex, as no single test enables the analysis of all aspects of platelet function. Furthermore, the available tests lack standardization, and repeat tests must be performed in specialized laboratories especially for mild and moderate forms of the disease. In this review, we provide an overview of the laboratory tests used to diagnose CPDF, with a focus on light transmission platelet aggregation (LTA), flow cytometry (FC), and granules assessment. Global tests, mainly represented by LTA, are often initially performed to investigate the consequences of platelet activation on platelet aggregation in a single step. Global test results should be confirmed by additional analytical tests. FC represents an accurate, simple, and reliable test to analyze abnormalities in platelet receptors, and granule content and release. This technique may also be used to investigate platelet function by comparing resting- and activated-state platelet populations. Assessment of granule content and release also requires additional specialized analytical tests. High-throughput sequencing has become increasingly useful to diagnose CPDF. Advanced tests or external research laboratory techniques may also be beneficial in some cases.
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Affiliation(s)
- Manal Ibrahim-Kosta
- Aix Marseille University, INSERM, INRAE, Marseille Cedex 05, France.,Laboratory of Hematology, CHU Timone, Marseille Cedex 05, France
| | - Marie-Christine Alessi
- Aix Marseille University, INSERM, INRAE, Marseille Cedex 05, France.,Laboratory of Hematology, CHU Timone, Marseille Cedex 05, France
| | - Nathalie Hezard
- Laboratory of Hematology, CHU Timone, Marseille Cedex 05, France
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8
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Alessi MC, Sié P, Payrastre B. Strengths and Weaknesses of Light Transmission Aggregometry in Diagnosing Hereditary Platelet Function Disorders. J Clin Med 2020; 9:jcm9030763. [PMID: 32178287 PMCID: PMC7141357 DOI: 10.3390/jcm9030763] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Revised: 02/17/2020] [Accepted: 03/03/2020] [Indexed: 12/15/2022] Open
Abstract
Hereditary defects in platelet function are responsible for sometimes severe mucocutaneous hemorrhages. They are a heterogeneous group of abnormalities whose first-line diagnosis typically involves interpreting the results of in vitro light transmission aggregometry (LTA) traces. Interpretation of LTA is challenging. LTA is usually performed in specialized laboratories with expertise in platelet pathophysiology. This review updates knowledge on LTA, describing the various platelet aggregation profiles typical of hereditary platelet disorders to guide the physician in the diagnosis of functional platelet disorders.
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Affiliation(s)
- Marie-Christine Alessi
- Aix Marseille Univ, Inserm, Inrae, C2VN, 13385 Marseille CEDEX, France
- Correspondence: ; Tel.: +33-4-91-32-45-06
| | - Pierre Sié
- CHU de Toulouse, Laboratoire d’Hématologie, 31059 Toulouse CEDEX, France;
| | - Bernard Payrastre
- Inserm U1048, I2MC et Université Paul Sabatier, 31024 Toulouse CEDEX, France;
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9
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Inoue A, Raimondi F, Kadji FMN, Singh G, Kishi T, Uwamizu A, Ono Y, Shinjo Y, Ishida S, Arang N, Kawakami K, Gutkind JS, Aoki J, Russell RB. Illuminating G-Protein-Coupling Selectivity of GPCRs. Cell 2019; 177:1933-1947.e25. [PMID: 31160049 DOI: 10.1016/j.cell.2019.04.044] [Citation(s) in RCA: 325] [Impact Index Per Article: 65.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Revised: 01/28/2019] [Accepted: 04/25/2019] [Indexed: 12/20/2022]
Abstract
Heterotrimetic G proteins consist of four subfamilies (Gs, Gi/o, Gq/11, and G12/13) that mediate signaling via G-protein-coupled receptors (GPCRs), principally by receptors binding Gα C termini. G-protein-coupling profiles govern GPCR-induced cellular responses, yet receptor sequence selectivity determinants remain elusive. Here, we systematically quantified ligand-induced interactions between 148 GPCRs and all 11 unique Gα subunit C termini. For each receptor, we probed chimeric Gα subunit activation via a transforming growth factor-α (TGF-α) shedding response in HEK293 cells lacking endogenous Gq/11 and G12/13 proteins, and complemented G-protein-coupling profiles through a NanoBiT-G-protein dissociation assay. Interrogation of the dataset identified sequence-based coupling specificity features, inside and outside the transmembrane domain, which we used to develop a coupling predictor that outperforms previous methods. We used the predictor to engineer designer GPCRs selectively coupled to G12. This dataset of fine-tuned signaling mechanisms for diverse GPCRs is a valuable resource for research in GPCR signaling.
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Affiliation(s)
- Asuka Inoue
- Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Miyagi 980-8578, Japan; Advanced Research & Development Programs for Medical Innovation (PRIME), Japan Agency for Medical Research and Development (AMED), Chiyoda-ku, Tokyo 100-0004, Japan; Advanced Research & Development Programs for Medical Innovation (LEAP), AMED, Chiyoda-ku, Tokyo 100-0004, Japan.
| | - Francesco Raimondi
- CellNetworks, Bioquant, Heidelberg University, Im Neuenheimer Feld 267, 69120 Heidelberg, Germany; Biochemie Zentrum Heidelberg (BZH), Heidelberg University, Im Neuenheimer Feld 328, 69120 Heidelberg, Germany.
| | | | - Gurdeep Singh
- CellNetworks, Bioquant, Heidelberg University, Im Neuenheimer Feld 267, 69120 Heidelberg, Germany; Biochemie Zentrum Heidelberg (BZH), Heidelberg University, Im Neuenheimer Feld 328, 69120 Heidelberg, Germany
| | - Takayuki Kishi
- Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Miyagi 980-8578, Japan
| | - Akiharu Uwamizu
- Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Miyagi 980-8578, Japan
| | - Yuki Ono
- Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Miyagi 980-8578, Japan
| | - Yuji Shinjo
- Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Miyagi 980-8578, Japan
| | - Satoru Ishida
- Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Miyagi 980-8578, Japan
| | - Nadia Arang
- Department of Pharmacology and Moores Cancer Center, University of California, San Diego, La Jolla, CA 92093, USA
| | - Kouki Kawakami
- Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Miyagi 980-8578, Japan
| | - J Silvio Gutkind
- Department of Pharmacology and Moores Cancer Center, University of California, San Diego, La Jolla, CA 92093, USA
| | - Junken Aoki
- Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Miyagi 980-8578, Japan; Advanced Research & Development Programs for Medical Innovation (LEAP), AMED, Chiyoda-ku, Tokyo 100-0004, Japan
| | - Robert B Russell
- CellNetworks, Bioquant, Heidelberg University, Im Neuenheimer Feld 267, 69120 Heidelberg, Germany; Biochemie Zentrum Heidelberg (BZH), Heidelberg University, Im Neuenheimer Feld 328, 69120 Heidelberg, Germany.
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10
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von Kügelgen I. Pharmacology of P2Y receptors. Brain Res Bull 2019; 151:12-24. [PMID: 30922852 DOI: 10.1016/j.brainresbull.2019.03.010] [Citation(s) in RCA: 57] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Revised: 03/04/2019] [Accepted: 03/17/2019] [Indexed: 01/17/2023]
Abstract
P2Y receptors are G-protein-coupled receptors (GPCRs) for extracellular nucleotides. There are eight mammalian P2Y receptor subtypes divided into two subgroups (P2Y1, P2Y2, P2Y4, P2Y6, and P2Y11) and (P2Y12, P2Y13, and P2Y14). The P2Y receptors are expressed in various cell types and play important roles in physiology and pathophysiology including inflammatory responses and neuropathic pain. The antagonism of P2Y12 receptors is used in pharmacotherapy for the prevention and therapy of cardiovascular events. The nucleoside analogue ticagrelor and active metabolites of the thienopyridine compounds ticlopidine, clopidogrel and prasugrel inhibit platelet P2Y12 receptors and reduce thereby platelet aggregation. The P2Y2 receptor agonist diquafosol is used for the treatment of the dry eye syndrome. The P2Y receptor subtypes differ in their amino acid sequences, their pharmacological profiles and their signaling transduction pathways. Recently, selective receptor ligands have been developed for all subtypes. The published crystal structures of the human P2Y1 and P2Y12 receptors as well as receptor models will facilitate the development of novel drugs for pharmacotherapy.
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Affiliation(s)
- Ivar von Kügelgen
- Department of Pharmacology and Toxicology, Pharma Center, University of Bonn, D-53127, Bonn, Germany.
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11
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Garcia C, Maurel-Ribes A, Nauze M, N'Guyen D, Martinez LO, Payrastre B, Sénard JM, Galés C, Pons V. Deciphering biased inverse agonism of cangrelor and ticagrelor at P2Y 12 receptor. Cell Mol Life Sci 2019; 76:561-576. [PMID: 30406277 PMCID: PMC11105710 DOI: 10.1007/s00018-018-2960-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Revised: 10/15/2018] [Accepted: 10/29/2018] [Indexed: 12/12/2022]
Abstract
P2Y12 receptor (P2Y12-R) is one of the major targets for drug inhibiting platelet aggregation in the treatment/prevention of arterial thrombosis. However, the clinical use of P2Y12-R antagonists faces some limitations, such as a delayed onset of action (clopidogrel) or adverse effect profile (ticagrelor, cangrelor), justifying the development of a new generation of P2Y12-R antagonists with a better clinical benefit-risk balance. Although the recent concept of biased agonism offers the possibility to alleviate undesirable adverse effects while preserving therapeutic outcomes, it has never been explored at P2Y12-R. For the first time, using highly sensitive BRET2-based probes, we accurately delineated biased ligand efficacy at P2Y12-R in living HEK293T cells on G protein activation and downstream effectors. We demonstrated that P2Y12-R displayed constitutive Gi/o-dependent signaling that is impaired by the R122C mutation, previously associated with a bleeding disorder. More importantly, we reported the biased inverse agonist efficacy of cangrelor and ticagrelor that could underlie their clinical efficacy. Our study points out that constitutive P2Y12-R signaling is a normal feature of the receptor that might be essential for platelets to respond faster to a vessel injury. From a therapeutic standpoint, our data suggest that the beneficial advantages of antiplatelet drugs might be more related to inverse agonism at P2Y12-R than to antagonism of ADP-mediated signaling. In the future, deciphering P2Y12-R constitutive activity should allow the discovery of more selective biased P2Y12-R blockers demonstrating therapeutic advantages over classical antiplatelet drugs by improving therapeutic outcomes and concomitantly relieving undesirable adverse effects.
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Affiliation(s)
- Cédric Garcia
- Laboratoire d'Hématologie, Centre Hospitalier Universitaire de Toulouse, 31000, Toulouse, France
| | - Agnès Maurel-Ribes
- Laboratoire d'Hématologie, Centre Hospitalier Universitaire de Toulouse, 31000, Toulouse, France
| | - Michel Nauze
- INSERM U1048, Institut des Maladies Métaboliques et Cardiovasculaires, Université de Toulouse, 1 Avenue Jean Poulhès, BP 84225, 31432, Toulouse Cedex 04, France
| | - Du N'Guyen
- INSERM U1048, Institut des Maladies Métaboliques et Cardiovasculaires, Université de Toulouse, 1 Avenue Jean Poulhès, BP 84225, 31432, Toulouse Cedex 04, France
| | - Laurent O Martinez
- INSERM U1048, Institut des Maladies Métaboliques et Cardiovasculaires, Université de Toulouse, 1 Avenue Jean Poulhès, BP 84225, 31432, Toulouse Cedex 04, France
| | - Bernard Payrastre
- Laboratoire d'Hématologie, Centre Hospitalier Universitaire de Toulouse, 31000, Toulouse, France
- INSERM U1048, Institut des Maladies Métaboliques et Cardiovasculaires, Université de Toulouse, 1 Avenue Jean Poulhès, BP 84225, 31432, Toulouse Cedex 04, France
| | - Jean-Michel Sénard
- INSERM U1048, Institut des Maladies Métaboliques et Cardiovasculaires, Université de Toulouse, 1 Avenue Jean Poulhès, BP 84225, 31432, Toulouse Cedex 04, France
- Service de Pharmacologie Clinique, Centre Hospitalier Universitaire de Toulouse, Université de Toulouse, 31000, Toulouse, France
| | - Céline Galés
- INSERM U1048, Institut des Maladies Métaboliques et Cardiovasculaires, Université de Toulouse, 1 Avenue Jean Poulhès, BP 84225, 31432, Toulouse Cedex 04, France
| | - Véronique Pons
- INSERM U1048, Institut des Maladies Métaboliques et Cardiovasculaires, Université de Toulouse, 1 Avenue Jean Poulhès, BP 84225, 31432, Toulouse Cedex 04, France.
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12
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Cattaneo M. Inherited Disorders of Platelet Function. Platelets 2019. [DOI: 10.1016/b978-0-12-813456-6.00048-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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13
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von Kügelgen I. Structure, Pharmacology and Roles in Physiology of the P2Y 12 Receptor. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1051:123-138. [PMID: 28921447 DOI: 10.1007/5584_2017_98] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
P2Y receptors are G-protein-coupled receptors (GPCRs) for extracellular nucleotides. The platelet ADP-receptor which has been denominated P2Y12 receptor is an important target in pharmacotherapy. The receptor couples to Gαi2 mediating an inhibition of cyclic AMP accumulation and additional downstream events including the activation of phosphatidylinositol-3-kinase and Rap1b proteins. The nucleoside analogue ticagrelor and active metabolites of the thienopyridine compounds ticlopidine, clopidogrel and prasugrel block P2Y12 receptors and, thereby, inhibit ADP-induced platelet aggregation. These drugs are used for the prevention and therapy of cardiovascular events such as acute coronary syndromes or stroke. The recently published three-dimensional crystal structures of the human P2Y12 receptor in complex with agonists and antagonists will facilitate the development of novel therapeutic agents with reduced adverse effects. P2Y12 receptors are also expressed on vascular smooth muscle cells and may be involved in the pathophysiology of atherogenesis. P2Y12 receptors on microglial cells operate as sensors for adenine nucleotides released during brain injury. A recent study indicated the involvement of microglial P2Y12 receptors in the activity-dependent neuronal plasticity. Interestingly, there is evidence for changes in P2Y12 receptor expression in CNS pathologies including Alzheimer's diseases and multiple sclerosis. P2Y12 receptors may also be involved in systemic immune modulating responses and the susceptibility to develop bronchial asthma.
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Affiliation(s)
- Ivar von Kügelgen
- Department of Pharmacology and Toxicology, Pharma Center, University of Bonn, D-53127, Bonn, Germany.
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14
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Mundell SJ, Rabbolini D, Gabrielli S, Chen Q, Aungraheeta R, Hutchinson JL, Kilo T, Mackay J, Ward CM, Stevenson W, Morel-Kopp MC. Receptor homodimerization plays a critical role in a novel dominant negative P2RY12 variant identified in a family with severe bleeding. J Thromb Haemost 2018; 16:44-53. [PMID: 29117459 DOI: 10.1111/jth.13900] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Indexed: 01/06/2023]
Abstract
Essentials Three dominant variants for the autosomal recessive bleeding disorder type-8 have been described. To date, there has been no phenotype/genotype correlation explaining their dominant transmission. Proline plays an important role in P2Y12R ligand binding and signaling defects. P2Y12R homodimer formation is critical for the receptor function and signaling. SUMMARY Background Although inherited platelet disorders are still underdiagnosed worldwide, advances in molecular techniques are improving disease diagnosis and patient management. Objective To identify and characterize the mechanism underlying the bleeding phenotype in a Caucasian family with an autosomal dominant P2RY12 variant. Methods Full blood counts, platelet aggregometry, flow cytometry and western blotting were performed before next-generation sequencing (NGS). Detailed molecular analysis of the identified variant of the P2Y12 receptor (P2Y12R) was subsequently performed in mammalian cells overexpressing receptor constructs. Results All three referred individuals had markedly impaired ADP-induced platelet aggregation with primary wave only, despite normal total and surface P2Y12R expression. By NGS, a single P2RY12:c.G794C substitution (p.R265P) was identified in all affected individuals, and this was confirmed by Sanger sequencing. Mammalian cell experiments with the R265P-P2Y12R variant showed normal receptor surface expression versus wild-type (WT) P2Y12R. Agonist-stimulated R265P-P2Y12R function (both signaling and surface receptor loss) was reduced versus WT P2Y12R. Critically, R265P-P2Y12R acted in a dominant negative manner, with agonist-stimulated WT P2Y12R activity being reduced by variant coexpression, suggesting dramatic loss of WT homodimers. Importantly, platelet P2RY12 cDNA cloning and sequencing in two affected individuals also revealed three-fold mutant mRNA overexpression, decreasing even further the likelihood of WT homodimer formation. R265 located within extracellular loop 3 (EL3) is one of four residues that are important for receptor functional integrity, maintaining the binding pocket conformation and allowing rotation following ligand binding. Conclusion This novel dominant negative variant confirms the important role of R265 in EL3 in the functional integrity of P2Y12R, and suggests that pathologic heterodimer formation may underlie this family bleeding phenotype.
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Affiliation(s)
- S J Mundell
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, UK
| | - D Rabbolini
- Department of Haematology and Transfusion Medicine, Royal North Shore Hospital, Sydney, Australia
- Northern Blood Research Centre, Kolling Institute, The University of Sydney, Sydney, Australia
| | - S Gabrielli
- Department of Haematology and Transfusion Medicine, Royal North Shore Hospital, Sydney, Australia
- Northern Blood Research Centre, Kolling Institute, The University of Sydney, Sydney, Australia
| | - Q Chen
- Department of Haematology and Transfusion Medicine, Royal North Shore Hospital, Sydney, Australia
- Northern Blood Research Centre, Kolling Institute, The University of Sydney, Sydney, Australia
| | - R Aungraheeta
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, UK
| | - J L Hutchinson
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, UK
| | - T Kilo
- Haematology Department, Westmead Children's Hospital, Sydney, Australia
| | - J Mackay
- School of Molecular Biosciences, The University of Sydney, Sydney, Australia
| | - C M Ward
- Department of Haematology and Transfusion Medicine, Royal North Shore Hospital, Sydney, Australia
- Northern Blood Research Centre, Kolling Institute, The University of Sydney, Sydney, Australia
| | - W Stevenson
- Department of Haematology and Transfusion Medicine, Royal North Shore Hospital, Sydney, Australia
- Northern Blood Research Centre, Kolling Institute, The University of Sydney, Sydney, Australia
| | - M-C Morel-Kopp
- Department of Haematology and Transfusion Medicine, Royal North Shore Hospital, Sydney, Australia
- Northern Blood Research Centre, Kolling Institute, The University of Sydney, Sydney, Australia
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15
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Raimondi F, Betts MJ, Lu Q, Inoue A, Gutkind JS, Russell RB. Genetic variants affecting equivalent protein family positions reflect human diversity. Sci Rep 2017; 7:12771. [PMID: 28986545 PMCID: PMC5630595 DOI: 10.1038/s41598-017-12971-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Accepted: 09/13/2017] [Indexed: 12/22/2022] Open
Abstract
Members of diverse protein families often perform overlapping or redundant functions meaning that different variations within them could reflect differences between individual organisms. We investigated likely functional positions within aligned protein families that contained a significant enrichment of nonsynonymous variants in genomes of healthy individuals. We identified more than a thousand enriched positions across hundreds of family alignments with roles indicative of mammalian individuality, including sensory perception and the immune system. The most significant position is the Arginine from the Olfactory receptor “DRY” motif, which has more variants in healthy individuals than all other positions in the proteome. Odorant binding data suggests that these variants lead to receptor inactivity, and they are mostly mutually exclusive with other loss-of-function (stop/frameshift) variants. Some DRY Arginine variants correlate with smell preferences in sub-populations and all 2,504 humans studied contain a unique spectrum of active and inactive receptors. The many other variant enriched positions, across hundreds of other families might also provide insights into individual differences.
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Affiliation(s)
- Francesco Raimondi
- CellNetworks, Bioquant, Heidelberg University, Im Neuenheimer Feld 267, 69120, Heidelberg, Germany.,Biochemie Zentrum Heidelberg (BZH), Heidelberg University, Im Neuenheimer Feld 328, 69120, Heidelberg, Germany
| | - Matthew J Betts
- CellNetworks, Bioquant, Heidelberg University, Im Neuenheimer Feld 267, 69120, Heidelberg, Germany.,Biochemie Zentrum Heidelberg (BZH), Heidelberg University, Im Neuenheimer Feld 328, 69120, Heidelberg, Germany
| | - Qianhao Lu
- CellNetworks, Bioquant, Heidelberg University, Im Neuenheimer Feld 267, 69120, Heidelberg, Germany.,Biochemie Zentrum Heidelberg (BZH), Heidelberg University, Im Neuenheimer Feld 328, 69120, Heidelberg, Germany
| | - Asuka Inoue
- Graduate School of Pharmaceutical Science, Tohoku University, Sendai, Miyagi, Japan.,Japan Science and Technology Agency (JST), Precursory Research for Embryonic Science and Technology (PRESTO), Kawaguchi, Saitama, Japan
| | | | - Robert B Russell
- CellNetworks, Bioquant, Heidelberg University, Im Neuenheimer Feld 267, 69120, Heidelberg, Germany. .,Biochemie Zentrum Heidelberg (BZH), Heidelberg University, Im Neuenheimer Feld 328, 69120, Heidelberg, Germany.
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16
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Cunningham MR, Aungraheeta R, Mundell SJ. Pathophysiological consequences of receptor mistraffic: Tales from the platelet P2Y 12 receptor. Mol Cell Endocrinol 2017; 449:74-81. [PMID: 28212842 DOI: 10.1016/j.mce.2017.02.016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Revised: 02/10/2017] [Accepted: 02/10/2017] [Indexed: 12/12/2022]
Abstract
Genetic variations in G protein-coupled receptor (GPCR) genes can disrupt receptor function in a wide variety of human genetic diseases, including platelet bleeding disorders. Platelets are critical for haemostasis with inappropriate platelet activation leading to the development of arterial thrombosis, which can result in heart attack and stroke whilst decreased platelet activity is associated with an increased risk of bleeding. GPCRs expressed on the surface of platelets play key roles in regulating platelet activity and therefore function. Receptors include purinergic receptors (P2Y1 and P2Y12), proteinase-activated receptor (PAR1 and PAR4) and thromboxane receptors (TPα), among others. Pharmacological blockade of these receptors forms a powerful therapeutic tool in the treatment and prevention of arterial thrombosis. With the advance of genomic technologies, there has been a substantial increase in the identification of naturally occurring rare and common GPCR variants. These variants include single-nucleotide polymorphisms (SNPs) and insertion or deletions that have the potential to alter GPCR expression or function. A number of defects in platelet GPCRs that disrupt receptor function have now been characterized in patients with mild bleeding disorders. This review will focus on rare, function-disrupting variants of platelet GPCRs with particular emphasis upon mutations in the P2Y12 receptor gene that affect receptor traffic to modulate platelet function. Further this review will outline how the identification and characterization of function-disrupting GPCR mutations provides an essential link in translating our detailed understanding of receptor traffic and function in cell line studies into relevant human biological systems.
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Affiliation(s)
- Margaret R Cunningham
- Strathclyde Institute for Pharmacy and Biomedical Sciences (SIPBS), University of Strathclyde, Glasgow, UK
| | - Riyaad Aungraheeta
- School of Physiology, Pharmacology and Neuroscience, Faculty of Biomedical Sciences, University of Bristol, Bristol, UK
| | - Stuart J Mundell
- School of Physiology, Pharmacology and Neuroscience, Faculty of Biomedical Sciences, University of Bristol, Bristol, UK.
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17
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Affiliation(s)
- Mariangela Scavone
- a Unità di Medicina 3, Ospedale San Paolo, Dipartimento di Scienze della Salute , Università degli Studi di Milano , Milano , Italy
| | - Eti A Femia
- a Unità di Medicina 3, Ospedale San Paolo, Dipartimento di Scienze della Salute , Università degli Studi di Milano , Milano , Italy
| | - Marco Cattaneo
- a Unità di Medicina 3, Ospedale San Paolo, Dipartimento di Scienze della Salute , Università degli Studi di Milano , Milano , Italy
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18
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Rovati GE, Capra V, Shaw VS, Malik RU, Sivaramakrishnan S, Neubig RR. The DRY motif and the four corners of the cubic ternary complex model. Cell Signal 2017; 35:16-23. [PMID: 28347873 DOI: 10.1016/j.cellsig.2017.03.020] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Accepted: 03/24/2017] [Indexed: 12/14/2022]
Abstract
Recent structural data on GPCRs using a variety of spectroscopic approaches suggest that GPCRs adopt a dynamic conformational landscape, with ligands stabilizing subsets of these states to activate one or more downstream signaling effectors. A key outstanding question posed by this emerging dynamic structural model of GPCRs is what states, active, inactive, or intermediate are captured by the numerous crystal structures of GPCRs complexed with a variety of agonists, partial agonists, and antagonists. In the early nineties the discovery of inverse agonists and constitutive activity led to the idea that the active receptor state (R⁎) is an intrinsic property of the receptor itself rather than of the RG complex, eventually leading to the formulation of the cubic ternary complex model (CTC). Here, by a careful analysis of a series of data obtained with a number of mutants of the highly conserved E/DRY motif, we show evidences for the existence of all the receptor states theorized by the CTC, four 'uncoupled (R, R⁎ and HR and HR⁎), and, consequently four 'coupled' (RG, R⁎G, HRG and HR⁎G). The E/DRY motif located at the cytosolic end of transmembrane helix III of Class A GPCRs has been widely studied and analyzed because it forms a network of interactions believed to lock receptors in the inactive conformation (R), and, thus, to play a key role in receptor activation. Our conclusions are supported by recent crystal and NMR spectra, as well as by results obtained with two prototypical GPCRs using a new FRET technology that de-couples G protein binding to the receptor from signal transduction. Thus, despite its complexity and limitations, we propose that the CTC is a useful framework to reconcile pharmacological, biochemical and structural data.
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Affiliation(s)
- G Enrico Rovati
- Department of Pharmacological and Biomolecular Sciences, University of Milan, Milano, Italy.
| | - Valérie Capra
- Department of Pharmacological and Biomolecular Sciences, University of Milan, Milano, Italy; Department of Health Science, University of Milan, Milano, Italy.
| | - Vincent S Shaw
- Department of Pharmacology & Toxicology, Michigan State University, East Lansing, MI, USA.
| | - Rabia U Malik
- Department of Genetics, Cell Biology & Development, College of Biological Sciences, University of Minnesota Twin Cities, Minneapolis, MN, USA.
| | - Sivaraj Sivaramakrishnan
- Department of Genetics, Cell Biology & Development, College of Biological Sciences, University of Minnesota Twin Cities, Minneapolis, MN, USA.
| | - Richard R Neubig
- Department of Pharmacology & Toxicology, Michigan State University, East Lansing, MI, USA.
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19
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Inverse agonism at the P2Y12 receptor and ENT1 transporter blockade contribute to platelet inhibition by ticagrelor. Blood 2016; 128:2717-2728. [PMID: 27694321 DOI: 10.1182/blood-2016-03-707844] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Accepted: 09/22/2016] [Indexed: 12/13/2022] Open
Abstract
Ticagrelor is a potent antagonist of the P2Y12 receptor (P2Y12R) and consequently an inhibitor of platelet activity effective in the treatment of atherothrombosis. Here, we sought to further characterize its molecular mechanism of action. Initial studies showed that ticagrelor promoted a greater inhibition of adenosine 5'-diphosphate (ADP)-induced Ca2+ release in washed platelets vs other P2Y12R antagonists. This additional effect of ticagrelor beyond P2Y12R antagonism was in part as a consequence of ticagrelor inhibiting the equilibrative nucleoside transporter 1 (ENT1) on platelets, leading to accumulation of extracellular adenosine and activation of Gs-coupled adenosine A2A receptors. This contributed to an increase in basal cyclic adenosine monophosphate (cAMP) and vasodilator-stimulated phosphoprotein phosphorylation (VASP-P). In addition, ticagrelor increased platelet cAMP and VASP-P in the absence of ADP in an adenosine receptor-independent manner. We hypothesized that this increase originated from a direct effect on basal agonist-independent P2Y12R signaling, and this was validated in 1321N1 cells stably transfected with human P2Y12R. In these cells, ticagrelor blocked the constitutive agonist-independent activity of the P2Y12R, limiting basal Gi-coupled signaling and thereby increasing cAMP levels. These data suggest that ticagrelor has the pharmacological profile of an inverse agonist. Based on our results showing insurmountable inhibition of ADP-induced Ca2+ release and forskolin-induced cAMP, the mode of antagonism of ticagrelor also appears noncompetitive, at least functionally. In summary, our studies describe 2 novel modes of action of ticagrelor, inhibition of platelet ENT1 and inverse agonism at the P2Y12R that contribute to its effective inhibition of platelet activation.
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20
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Hamilton JR, Trejo J. Challenges and Opportunities in Protease-Activated Receptor Drug Development. Annu Rev Pharmacol Toxicol 2016; 57:349-373. [PMID: 27618736 DOI: 10.1146/annurev-pharmtox-011613-140016] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Protease-activated receptors (PARs) are a unique class of G protein-coupled receptors (GPCRs) that transduce cellular responses to extracellular proteases. PARs have important functions in the vasculature, inflammation, and cancer and are important drug targets. A unique feature of PARs is their irreversible proteolytic mechanism of activation that results in the generation of a tethered ligand that cannot diffuse away. Despite the fact that GPCRs have proved to be the most successful class of druggable targets, the development of agents that target PARs specifically has been challenging. As a consequence, researchers have taken a remarkable diversity of approaches to develop pharmacological entities that modulate PAR function. Here, we present an overview of the diversity of therapeutic agents that have been developed against PARs. We further discuss PAR biased signaling and the influence of receptor compartmentalization, posttranslational modifications, and dimerization, which are important considerations for drug development.
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Affiliation(s)
- Justin R Hamilton
- Australian Centre for Blood Diseases, Monash University, Melbourne, Victoria 3004, Australia
| | - JoAnn Trejo
- Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, California 92093;
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21
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Lecchi A, Femia EA, Paoletta S, Dupuis A, Ohlmann P, Gachet C, Jacobson KA, Machura K, Podda GM, Zieger B, Cattaneo M. Inherited dysfunctional platelet P2Y 12 receptor mutations associated with bleeding disorders. Hamostaseologie 2016; 36:279-283. [PMID: 27487748 DOI: 10.5482/hamo-16-03-0010] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Accepted: 07/20/2016] [Indexed: 11/05/2022] Open
Abstract
The platelet adenosine 5'-diphosphate (ADP) receptor P2Y12 (P2Y12R) plays a critical role in platelet aggregation. The present report illustrates an update of dysfunctional platelet P2Y12R mutations diagnosed with congenital lifelong bleeding problems. Described patients with heterozygous or homozygous substitution in the P2Y12R gene and qualitative abnormalities of the platelet P2Y12R are summarized. Recently, a further dysfunctional variant of P2Y12R has been identified in two brothers who presented with a lifelong severe bleeding disorder. During in vitro aggregation studies, the patient´s platelets show a markedly reduced and rapid reversible ADP-promoted aggregation. A homozygous c.561T>A substitution that changes the codon for His187 to Gln (p.His187Gln) in the P2Y12R gene has been identified. This mutation causes no change in receptor expression but decreases the affinity of the ligand for the receptor, even at high concentrations. Structure modelling studies indicated that the p.His187Gln mutation, located in the fifth transmembrane spanning domain (TM5), impairs conformational changes of the receptor. Structural integrity of the TM5 region is necessary for agonist and antagonist binding and for correct receptor function.
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Affiliation(s)
| | | | | | | | | | | | | | - Katharina Machura
- Katharina Machura, University Medical Center, Freiburg - Department of Pediatrics and Adolescent Medicine, Breisacher-Str. 66, 79106 Freiburg, Germany, Tel. +49/(0)761/27 06 37 10, E-mail:
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22
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Abstract
PURPOSE OF REVIEW The inherited platelet disorders have witnessed a surge in our understanding of molecular mechanisms of disease in the past few years due in large to part to the introduction of next-generation sequencing for discovery of novel genes. The purpose of this review is to update the reader on the novel discoveries with regard to the inherited platelet disorders, with a particular focus on describing the novel disorders described most recently. RECENT FINDINGS The description of novel mechanisms of disease including mutations in PRKACG, in a family with severe macrothrombocytopenia, RUNX1 and FLI1 mutations in patients with inherited mild platelet function disorders and CalDAG-GEFI resulting in a severe platelet bleeding phenotype show that there is still much to be learned from studying families and molecular sequencing of patients with well phenotyped platelet disorders. SUMMARY The implications for clinical practice of the continually growing list of genes described in small numbers of families makes whole exome/genome tempting as an option for evaluation of patients, but use outside of the research setting still needs to be done with extreme caution as interpretation of variants is likely to require additional studies.
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23
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von Kügelgen I, Hoffmann K. Pharmacology and structure of P2Y receptors. Neuropharmacology 2015; 104:50-61. [PMID: 26519900 DOI: 10.1016/j.neuropharm.2015.10.030] [Citation(s) in RCA: 163] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Revised: 10/22/2015] [Accepted: 10/23/2015] [Indexed: 01/30/2023]
Abstract
P2Y receptors are G-protein-coupled receptors (GPCRs) for extracellular nucleotides. There are eight mammalian P2Y receptor subtypes (P2Y1, P2Y2, P2Y4, P2Y6, P2Y11, P2Y12, P2Y13, and P2Y14). P2Y receptors are widely expressed and play important roles in physiology and pathophysiology. One important example is the ADP-induced platelet aggregation mediated by P2Y1 and P2Y12 receptors. Active metabolites of the thienopyridine compounds ticlopidine, clopidogrel and prasugrel as well as the nucleoside analogue ticagrelor block P2Y12 receptors and thereby platelet aggregation. These drugs are used for the prevention and therapy of cardiovascular events. Moreover, P2Y receptors play important roles in the nervous system. Adenine nucleotides modulate neuronal activity and neuronal fibre outgrowth by activation of P2Y1 receptors and control migration of microglia by P2Y12 receptors. UDP stimulates microglial phagocytosis through activation of P2Y6 receptors. There is evidence for a role for P2Y2 receptors in Alzheimer's disease pathology. The P2Y receptor subtypes are highly diverse in both their amino acid sequences and their pharmacological profiles. Selective receptor ligands have been developed for the pharmacological characterization of the receptor subtypes. The recently published three-dimensional crystal structures of the human P2Y1 and P2Y12 receptors will facilitate the development of therapeutic agents that selectively target P2Y receptors. This article is part of the Special Issue entitled 'Purines in Neurodegeneration and Neuroregeneration'.
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Affiliation(s)
- Ivar von Kügelgen
- Department of Pharmacology and Toxicology, Pharma Center, University of Bonn, D-53127 Bonn, Germany.
| | - Kristina Hoffmann
- Department of Pharmacology and Toxicology, Pharma Center, University of Bonn, D-53127 Bonn, Germany
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Abstract
The platelet P2Y12 receptor (P2Y12R) for adenosine 5'diphosphate (ADP) plays a central role in platelet function, hemostasis, and thrombosis. Patients with inherited P2Y12R defects display mild-to-moderate bleeding diatheses. Defects of P2Y12R should be suspected when ADP, even at high concentrations (≥ 10 μm), is unable to induce full, irreversible platelet aggregation. P2Y12R also plays a role in inflammation: its role in the pathogenesis of allergic asthma has been well characterized. In addition, inhibition or genetic deficiency of P2Y12R has antitumor effects. Drugs inhibiting P2Y12R are potent antithrombotic drugs. Clopidogrel is the P2Y12R antagonist that is most widely used in the clinical setting. Its most important drawback is its inability to inhibit adequately P2Y12R-dependent platelet function in about one-third of patients. New drugs, such as prasugrel and ticagrelor, which effectively inhibit P2Y12R in the vast majority of patients, have proved to be more efficacious than clopdidogrel in preventing major adverse cardiovascular events.
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Affiliation(s)
- M Cattaneo
- Dipartimento di Scienze della Salute, Università degli Studi di Milano, Unità di Medicina 3, Ospedale San Paolo, Milan, Italy
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Abstract
The gene variants responsible for the primary genotype of many platelet disorders have now been identified. Next-generation sequencing technology (NGST), mainly exome sequencing, has highlighted genes responsible for defects in platelet secretion (NBEAL2, gray platelet syndrome), procoagulant activity (STIM1, Stormorken syndrome), and activation pathways (RASGRP2, CalDAG-GEFI deficiency and integrin dysfunction; PRKACG, cyclic adenosine monophosphate-dependent protein kinase deficiency). Often disorders of platelet function are associated with a modified platelet production with changes in platelet number and size and can accompany malfunction of other organs or tissues. Most families have private mutations, and gene variants may prevent protein synthesis, abrogate function, or result in aberrant activated proteins. Nevertheless, bleeding severity is difficult to predict by genotype alone suggesting other factors. A major new challenge of NGST is to identify these factors and help improve patient care. This review concentrates on recent developments and is illustrated from personal observations.
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Affiliation(s)
- A T Nurden
- Institut de Rhythmologie et de Modélisation Cardiaque, Plateforme Technologique d'Innovation Biomédicale, Hôpital Xavier Arnozan, Pessac, France
| | - P Nurden
- Institut de Rhythmologie et de Modélisation Cardiaque, Plateforme Technologique d'Innovation Biomédicale, Hôpital Xavier Arnozan, Pessac, France
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Zhang JH, Wang J, Tang XF, Yao Y, Zhang Y, Ma YL, Xu B, Gao RL, Song L, Gao Z, Chen J, Wu Y, Yang YJ, Meng XM, Yuan JQ. Effect of platelet receptor gene polymorphisms on outcomes in ST-elevation myocardial infarction patients after percutaneous coronary intervention. Platelets 2015; 27:75-9. [PMID: 25901734 DOI: 10.3109/09537104.2015.1034096] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Polymorphisms in platelet receptor genes may influence platelet function. This study aimed to assess the impact of five polymorphisms of genes encoding platelet receptors on the risk of ischemic and bleeding events in ST-elevation myocardial infarction (STEMI) patients after percutaneous coronary intervention (PCI). 503 consecutive Chinese patients with STEMI after an uneventful PCI and exposed to standard dual antiplatelet therapy for 12 months were enrolled. Polymorphisms of platelet receptors, GPIa (ITGA2, 807C > T, rs1126643), GPVI (GP6, 13254T > C, rs1613662), PAR-1 (F2R, IVS-14A > T, rs168753) and P2Y12 (P2RY12, 34C > T, rs6785930 and H1/H2 haplotype, 52G > T, rs6809699) were detected by the ligase detection reaction. The follow-up period was 12 months. Overall, 34 (6.8%) ischemic events occurred and 46 (9.1%) major bleedings occurred. Multivariate Cox regression analysis showed the carriage of F2R rs168753 minor allele was an independent predictor of the composite ischemic events (HR 0.387, 95% CI 0.193-0.778, p = 0.008) after adjusted for established risk factors. Multivariate logistic regression model identified that carriage of P2RY12 rs6809699 minor allele (OR 2.71, 95% CI 1.298-5.659, p = 0.008) was an independent predictor of major bleedings. The associations were then validated in a second cohort of 483 STEMI patients. In STEMI patients after PCI, F2R rs168753 minor allele could significantly contribute to the risk of ischemic events, and P2RY12 rs6809699 minor allele could predict bleedings. The genetic testing of platelet receptors can be valuable in predicting adverse events in STEMI patients after PCI.
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Affiliation(s)
- Jia-Hui Zhang
- a Department of Cardiology, State Key Laboratory of Cardiovascular Disease , Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College , Beijing , People's Republic of China
| | - Jing Wang
- a Department of Cardiology, State Key Laboratory of Cardiovascular Disease , Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College , Beijing , People's Republic of China
| | - Xiao-Fang Tang
- a Department of Cardiology, State Key Laboratory of Cardiovascular Disease , Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College , Beijing , People's Republic of China
| | - Yi Yao
- a Department of Cardiology, State Key Laboratory of Cardiovascular Disease , Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College , Beijing , People's Republic of China
| | - Yin Zhang
- a Department of Cardiology, State Key Laboratory of Cardiovascular Disease , Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College , Beijing , People's Republic of China
| | - Yuan-Liang Ma
- a Department of Cardiology, State Key Laboratory of Cardiovascular Disease , Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College , Beijing , People's Republic of China
| | - Bo Xu
- a Department of Cardiology, State Key Laboratory of Cardiovascular Disease , Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College , Beijing , People's Republic of China
| | - Run-Lin Gao
- a Department of Cardiology, State Key Laboratory of Cardiovascular Disease , Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College , Beijing , People's Republic of China
| | - Lei Song
- a Department of Cardiology, State Key Laboratory of Cardiovascular Disease , Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College , Beijing , People's Republic of China
| | - Zhan Gao
- a Department of Cardiology, State Key Laboratory of Cardiovascular Disease , Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College , Beijing , People's Republic of China
| | - Jue Chen
- a Department of Cardiology, State Key Laboratory of Cardiovascular Disease , Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College , Beijing , People's Republic of China
| | - Yuan Wu
- a Department of Cardiology, State Key Laboratory of Cardiovascular Disease , Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College , Beijing , People's Republic of China
| | - Yue-Jin Yang
- a Department of Cardiology, State Key Laboratory of Cardiovascular Disease , Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College , Beijing , People's Republic of China
| | - Xian-Min Meng
- a Department of Cardiology, State Key Laboratory of Cardiovascular Disease , Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College , Beijing , People's Republic of China
| | - Jin-Qing Yuan
- a Department of Cardiology, State Key Laboratory of Cardiovascular Disease , Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College , Beijing , People's Republic of China
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Leo VC, Morgan NV, Bem D, Jones ML, Lowe GC, Lordkipanidzé M, Drake S, Simpson MA, Gissen P, Mumford A, Watson SP, Daly ME. Use of next-generation sequencing and candidate gene analysis to identify underlying defects in patients with inherited platelet function disorders. J Thromb Haemost 2015; 13:643-50. [PMID: 25556537 PMCID: PMC4383639 DOI: 10.1111/jth.12836] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2014] [Accepted: 12/14/2014] [Indexed: 12/22/2022]
Abstract
BACKGROUND Inherited platelet function disorders (PFDs) are heterogeneous, and identification of the underlying genetic defects is difficult when based solely on phenotypic and clinical features of the patient. OBJECTIVE To analyze 329 genes regulating platelet function, number, and size in order to identify candidate gene defects in patients with PFDs. PATIENTS/METHODS Targeted analysis of candidate PFD genes was undertaken after next-generation sequencing of exomic DNA from 18 unrelated index cases with PFDs who were recruited into the UK Genotyping and Phenotyping of Platelets (GAPP) study and diagnosed with platelet abnormalities affecting either Gi signaling (n = 12) or secretion (n = 6). The potential pathogenicity of candidate gene defects was assessed using computational predictive algorithms. RESULTS Analysis of the 329 candidate PFD genes identified 63 candidate defects, affecting 40 genes, among index cases with Gi signaling abnormalities, while 53 defects, within 49 genes, were identified among patients with secretion abnormalities. Homozygous gene defects were more commonly associated with secretion abnormalities. Functional annotation analysis identified distinct gene clusters in the two patient subgroups. Thirteen genes with significant annotation enrichment for 'intracellular signaling' harbored 16 of the candidate gene defects identified in nine index cases with Gi signaling abnormalities. Four gene clusters, representing 14 genes, with significantly associated gene ontology annotations were identified among the cases with secretion abnormalities, the most significant association being with 'establishment of protein localization.' CONCLUSION Our findings demonstrate the genetic complexity of PFDs and highlight plausible candidate genes for targeted analysis in patients with platelet secretion and Gi signaling abnormalities.
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Affiliation(s)
- V C Leo
- Department of Cardiovascular Science, University of Sheffield Medical School, University of Sheffield, Sheffield, UK
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Burczyk M, Burkhalter MD, Blätte T, Matysik S, Caron MG, Barak LS, Philipp M. Phenotypic regulation of the sphingosine 1-phosphate receptor miles apart by G protein-coupled receptor kinase 2. Biochemistry 2015; 54:765-75. [PMID: 25555130 PMCID: PMC4310627 DOI: 10.1021/bi501061h] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
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The evolutionarily conserved DRY
motif at the end of the third
helix of rhodopsin-like, class-A G protein-coupled receptors (GPCRs)
is a major regulator of receptor stability, signaling activity, and
β-arrestin-mediated internalization. Substitution of the DRY
arginine with histidine in the human vasopressin receptor results
in a loss-of-function phenotype associated with diabetes insipidus.
The analogous R150H substitution of the DRY motif in zebrafish sphingosine-1
phosphate receptor 2 (S1p2) produces a mutation, miles apart m93 (milm93), that not only disrupts signaling but
also impairs heart field migration. We hypothesized that constitutive
S1p2 desensitization is the underlying cause of this strong zebrafish
developmental defect. We observed in cell assays that the wild-type
S1p2 receptor is at the cell surface whereas in distinct contrast
the S1p2 R150H receptor is found in intracellular vesicles, blocking
G protein but not arrestin signaling activity. Surface S1p2 R150H
expression could be restored by inhibition of G protein-coupled receptor
kinase 2 (GRK2). Moreover, we observed that β-arrestin 2 and
GRK2 colocalize with S1p2 in developing zebrafish embryos and depletion
of GRK2 in the S1p2 R150H miles apart zebrafish partially rescued
cardia bifida. The ability of reduced GRK2 activity to reverse a developmental
phenotype associated with constitutive desensitization supports efforts
to genetically or pharmacologically target this kinase in diseases
involving biased GPCR signaling.
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Affiliation(s)
- Martina Burczyk
- Institute for Biochemistry and Molecular Biology, Ulm University , 89081 Ulm, Germany
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Jones ML, Norman JE, Morgan NV, Mundell SJ, Lordkipanidzé M, Lowe GC, Daly ME, Simpson MA, Drake S, Watson SP, Mumford AD. Diversity and impact of rare variants in genes encoding the platelet G protein-coupled receptors. Thromb Haemost 2015; 113:826-37. [PMID: 25567036 PMCID: PMC4510585 DOI: 10.1160/th14-08-0679] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Accepted: 11/13/2014] [Indexed: 12/20/2022]
Abstract
Platelet responses to activating agonists are influenced by common population variants within or near G protein-coupled receptor (GPCR) genes that affect receptor activity. However, the impact of rare GPCR gene variants is unknown. We describe the rare single nucleotide variants (SNVs) in the coding and splice regions of 18 GPCR genes in 7,595 exomes from the 1,000-genomes and Exome Sequencing Project databases and in 31 cases with inherited platelet function disorders (IPFDs). In the population databases, the GPCR gene target regions contained 740 SNVs (318 synonymous, 410 missense, 7 stop gain and 6 splice region) of which 70 % had global minor allele frequency (MAF) < 0.05 %. Functional annotation using six computational algorithms, experimental evidence and structural data identified 156/740 (21 %) SNVs as potentially damaging to GPCR function, most commonly in regions encoding the transmembrane and C-terminal intracellular receptor domains. In 31 index cases with IPFDs (Gi-pathway defect n=15; secretion defect n=11; thromboxane pathway defect n=3 and complex defect n=2) there were 256 SNVs in the target regions of 15 stimulatory platelet GPCRs (34 unique; 12 with MAF< 1 % and 22 with MAF≥ 1 %). These included rare variants predicting R122H, P258T and V207A substitutions in the P2Y12 receptor that were annotated as potentially damaging, but only partially explained the platelet function defects in each case. Our data highlight that potentially damaging variants in platelet GPCR genes have low individual frequencies, but are collectively abundant in the population. Potentially damaging variants are also present in pedigrees with IPFDs and may contribute to complex laboratory phenotypes.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | - Andrew D Mumford
- Dr. A. D. Mumford, University of Bristol, Level 7 Bristol Royal Infirmary, Bristol, BS2 8HW, United Kingdom, Tel.: +44 117 3423152, Fax: +44 117 3424036, E-mail
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Identification of a new dysfunctional platelet P2Y12 receptor variant associated with bleeding diathesis. Blood 2014; 125:1006-13. [PMID: 25428217 DOI: 10.1182/blood-2013-07-517896] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Defects of the platelet P2Y12 receptor (P2Y12R) for adenosine diphosphate (ADP) are associated with increased bleeding risk. The study of molecular abnormalities associated with inherited qualitative defects of the P2Y12R protein is useful to unravel structure-function relationships of the receptor. We describe the case of 2 brothers, sons of first cousins, with lifelong history of abnormal bleeding, associated with dysfunctional P2Y12R and a previously undescribed missense mutation in the encoding gene. ADP (4-20 µM)-induced aggregation of patients' platelets was markedly reduced and rapidly reversible. Other agonists induced borderline-normal aggregation. Inhibition of vasodilator-stimulated phosphoprotein phosphorylation and prostaglandin E1-induced increase in cyclic adenosine monophosphate (cAMP) by ADP was impaired, whereas inhibition of cAMP increase by epinephrine was normal. [(3)H]PSB-0413, a selective P2Y12R antagonist, bound to a normal number of binding sites; however, its affinity, and that of the agonists ADP and 2-methylthio-adenosine-5'-diphosphate, was reduced. Patients' DNA showed a homozygous c.847T>A substitution that changed the codon for His-187 to Gln (p.His187Gln). Crystallographic data and molecular modeling studies indicated that His187 in transmembrane 5 is important for agonist and nucleotide antagonist binding and located in a region undergoing conformational changes. These studies delineate a region of P2Y12R required for normal function after ADP binding.
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Nisar SP, Jones ML, Cunningham MR, Mumford AD, Mundell SJ. Rare platelet GPCR variants: what can we learn? Br J Pharmacol 2014; 172:3242-53. [PMID: 25231155 DOI: 10.1111/bph.12941] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2014] [Revised: 09/05/2014] [Accepted: 09/09/2014] [Indexed: 12/31/2022] Open
Abstract
Platelet-expressed GPCRs are critical regulators of platelet function. Pharmacological blockade of these receptors forms a powerful therapeutic tool in the treatment and prevention of arterial thrombosis associated with coronary atherosclerosis and ischaemic stroke. However, anti-thrombotic drug therapy is associated with high inter-patient variability in therapeutic response and adverse bleeding side effects. In order to optimize the use of existing anti-platelet drugs and to develop new therapies, more detailed knowledge is required relating to the molecular mechanisms that regulate GPCR and therefore platelet function. One approach has been to identify rare, function-disrupting mutations within key platelet proteins in patients with bleeding disorders. In this review, we describe how an integrated functional genomics strategy has contributed important structure-function information about platelet GPCRs with specific emphasis upon purinergic and thromboxane A2 receptors. We also discuss the potential implications these findings have for pharmacotherapy and for understanding the molecular basis of mild bleeding disorders.
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Affiliation(s)
- S P Nisar
- School of Physiology and Pharmacology, University of Bristol, Bristol, UK
| | - M L Jones
- School of Cellular and Molecular Medicine, University of Bristol, Bristol, UK
| | - M R Cunningham
- School of Physiology and Pharmacology, University of Bristol, Bristol, UK
| | - A D Mumford
- School of Cellular and Molecular Medicine, University of Bristol, Bristol, UK
| | - S J Mundell
- School of Physiology and Pharmacology, University of Bristol, Bristol, UK
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Rovati GE, Capra V. The DRY motif at work: the P2Y12 receptor case. J Thromb Haemost 2014; 12:713-5. [PMID: 24589132 DOI: 10.1111/jth.12543] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2014] [Accepted: 02/14/2014] [Indexed: 10/25/2022]
Affiliation(s)
- G E Rovati
- Department of Pharmacological and Biomolecular Sciences, Laboratory of Molecular Pharmacology, Milan, Italy
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Characterization of multiple platelet activation pathways in patients with bleeding as a high-throughput screening option: use of 96-well Optimul assay. Blood 2014; 123:e11-22. [PMID: 24408324 DOI: 10.1182/blood-2013-08-520387] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Up to 1% of the population have mild bleeding disorders, but these remain poorly characterized, particularly with regard to the roles of platelets. We have compared the usefulness of Optimul, a 96-well plate-based assay of 7 distinct pathways of platelet activation to characterize inherited platelet defects in comparison with light transmission aggregometry (LTA). Using Optimul and LTA, concentration-response curves were generated for arachidonic acid, ADP, collagen, epinephrine, Thrombin receptor activating-peptide, U46619, and ristocetin in samples from (1) healthy volunteers (n = 50), (2) healthy volunteers treated with antiplatelet agents in vitro (n = 10), and (3) patients with bleeding of unknown origin (n = 65). The assays gave concordant results in 82% of cases (κ = 0.62, P < .0001). Normal platelet function results were particularly predictive (sensitivity, 94%; negative predictive value, 91%), whereas a positive result was not always substantiated by LTA (specificity, 67%; positive predictive value, 77%). The Optimul assay was significantly more sensitive at characterizing defects in the thromboxane pathway, which presented with normal responses with LTA. The Optimul assay is sensitive to mild platelet defects, could be used as a rapid screening assay in patients presenting with bleeding symptoms, and detects changes in platelet function more readily than LTA. This trial was registered at www.isrctn.org as #ISRCTN 77951167.
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