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Capra V, Mauri M, Guzzi F, Busnelli M, Accomazzo MR, Gaussem P, Nisar SP, Mundell SJ, Parenti M, Rovati GE. Impaired thromboxane receptor dimerization reduces signaling efficiency: A potential mechanism for reduced platelet function in vivo. Biochem Pharmacol 2016; 124:43-56. [PMID: 27845050 DOI: 10.1016/j.bcp.2016.11.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Accepted: 11/10/2016] [Indexed: 12/16/2022]
Abstract
Thromboxane A2 is a potent mediator of inflammation and platelet aggregation exerting its effects through the activation of a G protein-coupled receptor (GPCR), termed TP. Although the existence of dimers/oligomers in Class A GPCRs is widely accepted, their functional significance still remains controversial. Recently, we have shown that TPα and TPβ homo-/hetero-dimers interact through an interface of residues in transmembrane domain 1 (TM1) whose disruption impairs dimer formation. Here, biochemical and pharmacological characterization of this dimer deficient mutant (DDM) in living cells indicates a significant impairment in its response to agonists. Interestingly, two single loss-of-function TPα variants, namely W29C and N42S recently identified in two heterozygous patients affected by bleeding disorders, match some of the residues mutated in our DDM. These two naturally occurring variants display a reduced potency to TP agonists and are characterized by impaired dimer formation in transfected HEK-293T cells. These findings provide proofs that lack of homo-dimer formation is a crucial process for reduced TPα function in vivo, and might represent one molecular mechanism through which platelet TPα receptor dysfunction affects the patient(s) carrying these mutations.
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Key Words
- (Z)-7-[(1R,2R,3R,4S)-3-[[2-(phenylcarbamoyl)hydrazinyl]methyl]-7-oxabicyclo[2.2.1]heptan-2-yl]hept-5-enoic acid
- (Z)-7-[(1S,2S,3R,4R)-3-[(E,3S)-3-hydroxyoct-1-enyl]-5-oxabicyclo[2.2.1]heptan-2-yl]hept-5-enoic acid
- (Z)-7-[(1S,2S,3S,4R)-3-[(E,3R)-3-hydroxy-4-(4-iodophenoxy)but-1-enyl]-7-oxabicyclo[2.2.1]heptan-2-yl]hept-5-enoic acid
- (Z)-7-[(1S,3R,4R,5S)-3-[(E,3R)-3-hydroxyoct-1-enyl]-6,6-dimethyl-4-bicyclo[3.1.1]heptanyl]hept-5-enoic acid
- 3-[(3R)-3-[(4-fluorophenyl)sulfonylamino]-1,2,3,4-tetrahydrocarbazol-9-yl]propanoic acid
- Eicosanoids
- G protein coupled receptors
- I-BOP (PubChem CID: 51015454)
- Pinane Thromboxane A2 (PTA2) (PubChem CID: 25834471)
- Platelets
- Ramatroban (PubChem CID: 123879)
- Receptor dimer
- SQ29,548 (PubChem CID: 6437074)
- Signal transduction
- Thromboxane A(2)
- U46619 (PubChem CID: 5311493)
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Affiliation(s)
- Valérie Capra
- Department of Pharmacological and Biomolecular Sciences, University of Milan, Milano, Italy; Department of Health Science, University of Milan, Milano, Italy.
| | - Mario Mauri
- Department of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy.
| | - Francesca Guzzi
- Department of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy.
| | - Marta Busnelli
- CNR, Institute of Neuroscience, University of Milan, Milan, Italy; Department of Medical Biotechnology and Translational Medicine, University of Milan, Milan, Italy.
| | - Maria Rosa Accomazzo
- Department of Pharmacological and Biomolecular Sciences, University of Milan, Milano, Italy.
| | - Pascale Gaussem
- Inserm UMR-S1140, Faculte' de Pharmacie, Université Paris Descartes, Sorbonne Paris Cité, Paris and AP-HP, Hopital Européen Georges Pompidou, Service d'Hématologie Biologique, Paris, France.
| | - Shaista P Nisar
- School of Physiology and Pharmacology, University of Bristol, Bristol BS8 1TD, UK.
| | - Stuart J Mundell
- School of Physiology and Pharmacology, University of Bristol, Bristol BS8 1TD, UK.
| | - Marco Parenti
- Department of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy.
| | - G Enrico Rovati
- Department of Pharmacological and Biomolecular Sciences, University of Milan, Milano, Italy.
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