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Hopp MT, Holze J, Lauber F, Holtkamp L, Rathod DC, Miteva MA, Prestes EB, Geyer M, Manoury B, Merle NS, Roumenina LT, Bozza MT, Weindl G, Imhof D. Insights into the molecular basis and mechanism of heme-triggered TLR4 signalling: The role of heme-binding motifs in TLR4 and MD2. Immunology 2024; 171:181-197. [PMID: 37885279 DOI: 10.1111/imm.13708] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Accepted: 10/06/2023] [Indexed: 10/28/2023] Open
Abstract
Haemolytic disorders, such as sickle cell disease, are accompanied by the release of high amounts of labile heme into the intravascular compartment resulting in the induction of proinflammatory and prothrombotic complications in affected patients. In addition to the relevance of heme-regulated proteins from the complement and blood coagulation systems, activation of the TLR4 signalling pathway by heme was ascribed a crucial role in the progression of these pathological processes. Heme binding to the TLR4-MD2 complex has been proposed recently, however, essential mechanistic information of the processes at the molecular level, such as heme-binding kinetics, the heme-binding capacity and the respective heme-binding sites (HBMs) is still missing. We report the interaction of TLR4, MD2 and the TLR4-MD2 complex with heme and the consequences thereof by employing biochemical, spectroscopic, bioinformatic and physiologically relevant approaches. Heme binding occurs transiently through interaction with up to four HBMs in TLR4, two HBMs in MD2 and at least four HBMs in their complex. Functional studies highlight that mutations of individual HBMs in TLR4 preserve full receptor activation by heme, suggesting that heme interacts with TLR4 through different binding sites independently of MD2. Furthermore, we confirm and extend the major role of TLR4 for heme-mediated cytokine responses in human immune cells.
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Affiliation(s)
- Marie-T Hopp
- Pharmaceutical Biochemistry and Bioanalytics, Pharmaceutical Institute, University of Bonn, Bonn, Germany
- Department of Chemistry, Institute of Integrated Natural Sciences, University of Koblenz, Koblenz, Germany
| | - Janine Holze
- Pharmacology and Toxicology, Pharmaceutical Institute, University of Bonn, Bonn, Germany
| | - Felicitas Lauber
- Pharmacology and Toxicology, Pharmaceutical Institute, University of Bonn, Bonn, Germany
| | - Laura Holtkamp
- Pharmacology and Toxicology, Pharmaceutical Institute, University of Bonn, Bonn, Germany
| | - Dhruv C Rathod
- Pharmaceutical Biochemistry and Bioanalytics, Pharmaceutical Institute, University of Bonn, Bonn, Germany
| | - Maria A Miteva
- CNRS UMR 8038 CiTCoM, Université de Paris, Faculté de Pharmacie de Paris, Paris, France
- INSERM U 1268 Medicinal Chemistry and Translational Research, Paris, France
| | - Elisa B Prestes
- Laboratório de Inflamação e Imunidade, Departamento de Imunologia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Matthias Geyer
- Institute of Structural Biology, University of Bonn, Bonn, Germany
| | - Bénédicte Manoury
- Institut Necker Enfants Malades, INSERM U1151-CNRS UMR8253, Université Paris Cité, Faculté de médecine Necker, Paris, France
| | - Nicolas S Merle
- Centre de Recherche des Cordeliers, UMR_S 1138, INSERM, Paris, France
- Centre de Recherche des Cordeliers, Sorbonne Universités, Paris, France
- Centre de Recherche des Cordeliers, Université Paris Descartes, Paris, France
| | - Lubka T Roumenina
- Centre de Recherche des Cordeliers, UMR_S 1138, INSERM, Paris, France
- Centre de Recherche des Cordeliers, Sorbonne Universités, Paris, France
- Centre de Recherche des Cordeliers, Université Paris Descartes, Paris, France
| | - Marcelo T Bozza
- Laboratório de Inflamação e Imunidade, Departamento de Imunologia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Günther Weindl
- Pharmacology and Toxicology, Pharmaceutical Institute, University of Bonn, Bonn, Germany
| | - Diana Imhof
- Pharmaceutical Biochemistry and Bioanalytics, Pharmaceutical Institute, University of Bonn, Bonn, Germany
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Structural Characterization of Heme Environmental Mutants of CgHmuT that Shuttles Heme Molecules to Heme Transporters. Int J Mol Sci 2016; 17:ijms17060829. [PMID: 27240352 PMCID: PMC4926363 DOI: 10.3390/ijms17060829] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Revised: 05/19/2016] [Accepted: 05/24/2016] [Indexed: 01/19/2023] Open
Abstract
Corynebacteria contain a heme uptake system encoded in hmuTUV genes, in which HmuT protein acts as a heme binding protein to transport heme to the cognate transporter HmuUV. The crystal structure of HmuT from Corynebacterium glutamicum (CgHmuT) reveals that heme is accommodated in the central cleft with His141 and Tyr240 as the axial ligands and that Tyr240 forms a hydrogen bond with Arg242. In this work, the crystal structures of H141A, Y240A, and R242A mutants were determined to understand the role of these residues for the heme binding of CgHmuT. Overall and heme environmental structures of these mutants were similar to those of the wild type, suggesting that there is little conformational change in the heme-binding cleft during heme transport reaction with binding and the dissociation of heme. A loss of one axial ligand or the hydrogen bonding interaction with Tyr240 resulted in an increase in the redox potential of the heme for CgHmuT to be reduced by dithionite, though the wild type was not reduced under physiological conditions. These results suggest that the heme environmental structure stabilizes the ferric heme binding in CgHmuT, which will be responsible for efficient heme uptake under aerobic conditions where Corynebacteria grow.
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