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Giladi M, Montgomery AP, Kassiou M, Danon JJ. Structure-based drug design for TSPO: Challenges and opportunities. Biochimie 2024:S0300-9084(24)00120-2. [PMID: 38782353 DOI: 10.1016/j.biochi.2024.05.018] [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: 02/19/2024] [Revised: 04/27/2024] [Accepted: 05/21/2024] [Indexed: 05/25/2024]
Abstract
The translocator protein 18 kDa (TSPO) is an evolutionarily conserved mitochondrial transmembrane protein implicated in various neuropathologies and inflammatory conditions, making it a longstanding diagnostic and therapeutic target of interest. Despite the development of various classes of TSPO ligand chemotypes, and the elucidation of bacterial and non-human mammalian experimental structures, many unknowns exist surrounding its differential structural and functional features in health and disease. There are several limitations associated with currently used computational methodologies for modelling the native structure and ligand-binding behaviour of this enigmatic protein. In this perspective, we provide a critical analysis of the developments in the uses of these methods, outlining their uses, inherent limitations, and continuing challenges. We offer suggestions of unexplored opportunities that exist in the use of computational methodologies which offer promise for enhancing our understanding of the TSPO.
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Affiliation(s)
- Mia Giladi
- School of Chemistry, The University of Sydney, 2050, Sydney, NSW, Australia
| | | | - Michael Kassiou
- School of Chemistry, The University of Sydney, 2050, Sydney, NSW, Australia.
| | - Jonathan J Danon
- School of Chemistry, The University of Sydney, 2050, Sydney, NSW, Australia.
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2
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Saade C, Pozza A, Bonneté F, Finet S, Lutz-Bueno V, Tully MD, Varela PF, Lacapère JJ, Combet S. Enhanced structure/function of mTSPO translocator in lipid:surfactant mixed micelles. Biochimie 2024:S0300-9084(24)00083-X. [PMID: 38663457 DOI: 10.1016/j.biochi.2024.04.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2024] [Revised: 04/06/2024] [Accepted: 04/19/2024] [Indexed: 05/06/2024]
Abstract
TSPO is a ubiquitous transmembrane protein used as a pharmacological marker in neuroimaging. The only known atomic structure of mammalian TSPOs comes from the solution NMR of mouse TSPO (mTSPO) bound to the PK11195 ligand and in a DPC surfactant environment. No structure is available in a biomimetic environment and without PK11195 which strongly stiffens the protein. We measured the effect of different amphiphilic environments on ligand-free mTSPO to study its structure/function and find optimal solubilization conditions. By replacing the SDS surfactant, where the recombinant protein is purified, with mixed lipid:surfactant (DMPC:DPC) micelles at different ratios (0:1, 1:2, and 2:1, w:w), the α-helix content and interactions and the intrinsic tryptophan (Trp) fluorescence of mTSPO are gradually increased. Small-angle X-ray scattering (SAXS) shows a more extended mTSPO/belt complex with the addition of lipids: Dmax ∼95 Å in DPC alone versus ∼142 Å in DMPC:DPC (1:2). SEC-MALLS shows that the molecular composition of the mTSPO belt is ∼98 molecules for DPC alone and ∼58 DMPC and ∼175 DPC for DMPC:DPC (1:2). Additionally, DMPC:DPC micelles stabilize mTSPO compared to DPC alone, where the protein has a greater propensity to aggregate. These structural changes are consistent with the increased affinity of mTSPO for the PK11195 ligand in presence of lipids (Kd ∼70 μM in DPC alone versus ∼0.91 μM in DMPC:DPC, 1:2), as measured by microscale thermophoresis (MST). In conclusion, mixed lipid:surfactant micelles open new possibilities for the stabilization of membrane proteins and for their study in solution in a more biomimetic amphiphilic environment.
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Affiliation(s)
- Christelle Saade
- Laboratoire Léon-Brillouin (LLB), UMR12 CEA-CNRS, Université Paris-Saclay, F-91191, Gif-sur-Yvette CEDEX, France
| | - Alexandre Pozza
- Université Paris Cité, CNRS UMR7099, Biochimie des Protéines Membranaires, F-75005, Paris, France
| | - Françoise Bonneté
- Université Paris Cité, CNRS UMR7099, Biochimie des Protéines Membranaires, F-75005, Paris, France
| | - Stéphanie Finet
- Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie (IMPMC), UMR 7590 CNRS-Sorbonne Université Université, MNHN, IRD, F-75005, Paris, France
| | - Viviane Lutz-Bueno
- Laboratoire Léon-Brillouin (LLB), UMR12 CEA-CNRS, Université Paris-Saclay, F-91191, Gif-sur-Yvette CEDEX, France; Paul Scherrer Institut (PSI), Forschungsstrasse 111, 5232, Villigen PSI, Switzerland
| | - Mark D Tully
- The European Synchrotron (ESRF), 71 Avenue des Martyrs, F-38043, Grenoble, France
| | - Paloma F Varela
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Saclay, F-91191, Gif-sur-Yvette CEDEX, France
| | - Jean-Jacques Lacapère
- Sorbonne Université, Ecole Normale Supérieure, PSL University, CNRS UMR 7203, Laboratoire des BioMolécules (LBM), 4 Place Jussieu, F-75005, Paris, France
| | - Sophie Combet
- Laboratoire Léon-Brillouin (LLB), UMR12 CEA-CNRS, Université Paris-Saclay, F-91191, Gif-sur-Yvette CEDEX, France.
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Rao RM, El Dhaybi I, Cadet F, Etchebest C, Diharce J. The mutual and dynamic role of TSPO and ligands in their binding process: An example with PK-11195. Biochimie 2024:S0300-9084(24)00067-1. [PMID: 38494108 DOI: 10.1016/j.biochi.2024.03.009] [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: 10/30/2023] [Revised: 02/12/2024] [Accepted: 03/15/2024] [Indexed: 03/19/2024]
Abstract
Translocator protein (TSPO) is an 18 kDa transmembrane protein, localized primarily on the outer mitochondrial membrane. It has been found to be involved in various physiological processes and pathophysiological conditions. Though studies on its structure have been performed only recently, there is little information on the nature of dynamics and doubts about some structures referenced in the literature, especially the NMR structure of mouse TSPO. In the present work, we thoroughly study the dynamics of mouse TSPO protein by means of atomistic molecular dynamics simulations, in presence as well as in absence of the diagnostic ligand PKA. We considered two starting structures: the NMR structure and a homology model (HM) generated on the basis of X-ray structures from bacterial TSPO. We examine the conformational landscape in both the modes for both starting points, in presence and absence of the ligand, in order to measure its impact for both structures. The analysis highlights high flexibility of the protein globally, but NMR simulations show a surprisingly flexibility even in the presence of the ligand. Interestingly, this is not the case for HM calculations, to the point that the ligand seems not so stable as in the NMR system and an unbinding event process is partially sampled. All those results tend to show that the NMR structure of mTSPO seems not deficient but is just in another portion of the global conformation space of TSPO.
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Affiliation(s)
- Rajas M Rao
- Data Analytics, Bioinformatics and Structural Biology Division, Yenepoya Research Centre, Yenepoya (Deemed to be University), Mangalore, India; Université Paris Cité and Université de la Réunion and Université des Antilles, INSERM, BIGR, DSIMB UMR_S1134, F-74014, Paris, France
| | - Ibaa El Dhaybi
- Université Paris Cité and Université de la Réunion and Université des Antilles, INSERM, BIGR, DSIMB UMR_S1134, F-74014, Paris, France
| | - Frédéric Cadet
- Université Paris Cité and Université de la Réunion and Université des Antilles, INSERM, BIGR, DSIMB UMR_S1134, F-74014, Paris, France; Laboratory of Excellence GR-Ex, Paris, France; Université Paris Cité and Université de la Réunion and Université des Antilles, INSERM, BIGR, DSIMB, F-97715, Saint Denis Messag, France; PEACCEL, Artificial Intelligence Department, Paris, 75013 France
| | - Catherine Etchebest
- Université Paris Cité and Université de la Réunion and Université des Antilles, INSERM, BIGR, DSIMB UMR_S1134, F-74014, Paris, France; Laboratory of Excellence GR-Ex, Paris, France
| | - Julien Diharce
- Université Paris Cité and Université de la Réunion and Université des Antilles, INSERM, BIGR, DSIMB UMR_S1134, F-74014, Paris, France; Laboratory of Excellence GR-Ex, Paris, France.
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Duport C, Armengaud J, Schmitt C, Morin D, Lacapère JJ. Elucidating the pivotal role of TSPO in porphyrin-related cellular processes, in Bacillus cereus. Biochimie 2024:S0300-9084(24)00046-4. [PMID: 38423451 DOI: 10.1016/j.biochi.2024.02.008] [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: 01/11/2024] [Revised: 02/19/2024] [Accepted: 02/21/2024] [Indexed: 03/02/2024]
Abstract
A structural homolog of the mammalian TSPO has been identified in the human pathogen Bacillus cereus. BcTSPO, in its recombinant form, has previously been shown to bind and degrade porphyrins. In this study, we generated a ΔtspO mutant strain in B. cereus ATCC 14579 and assessed the impact of the absence of BcTSPO on cellular proteomics and physiological characteristics. The proteomic analysis revealed correlations between the lack of BcTSPO and the observed growth defects, increased oxygen consumption, ATP deficiency, heightened tryptophan catabolism, reduced motility, and impaired biofilm formation in the ΔtspO mutant strain. Our results also suggested that BcTSPO plays a crucial role in regulating intracellular levels of metabolites from the coproporphyrin-dependent branch of the heme biosynthetic pathway. This regulation potentially underlies alterations in the metabolic landscape, emphasizing the pivotal role of BcTSPO in B. cereus aerobic metabolism. Notably, our study unveils, for the first time, the involvement of TSPO in tryptophan metabolism. These findings underscore the multifaceted role of TSPO, not only in metabolic pathways but also potentially in the microorganism's virulence mechanisms.
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Affiliation(s)
| | - Jean Armengaud
- Université Paris Saclay, CEA, INRAE, Département Médicaments et Technologies pour la Santé (DMTS), SPI, 30200, Bagnols-sur-Cèze, France
| | - Caroline Schmitt
- Assistance Publique Hôpitaux de Paris (AP-HP), Centre Français des Porphyries, Hôpital Louis Mourier, 92700, Colombes, France; INSERM U1149, Center for Research on Inflammation (CRI), Université de Paris, 75018, Paris, France
| | - Didier Morin
- INSERM, U955, équipe 3, Faculté de Médecine, Université Paris Est, 94010, Creteil, France
| | - Jean-Jacques Lacapère
- Sorbonne Université, Ecole Normale Supérieure, PSL University, CNRS UMR 7203, Laboratoire des BioMolécules (LBM), 4 place Jussieu, F-75005, Paris, France
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Issop L, Duma L, Finet S, Lequin O, Lacapère JJ. Among the recombinant TSPOs, the BcTSPO. Biochimie 2024:S0300-9084(24)00029-4. [PMID: 38280504 DOI: 10.1016/j.biochi.2024.01.011] [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: 10/19/2023] [Revised: 01/17/2024] [Accepted: 01/18/2024] [Indexed: 01/29/2024]
Abstract
Overexpression of recombinant Bacillus cereus TSPO (BcTSPO) in E. coli bacteria leads to its recovery with a bound hemin both in bacterial membrane (MB) and inclusion bodies (IB). Unlike mouse TSPO, BcTSPO purified in SDS detergent from IB is well structured and can bind various ligands such as high-affinity PK 11195, protoporphyrin IX (PPIX) and δ-aminolevulinic acid (ALA). For each of the three ligands, 1H-15N HSQC titration NMR experiments suggest that different amino acids of BcTSPO binding cavity are involved in the interaction. PPIX, an intermediate of heme biosynthesis, binds to the cavity of BcTSPO and its fluorescence can be significantly reduced in the presence of light and oxygen. The light irradiation leads to two products that have been isolated and characterized as photoporphyrins. They result from the addition of singlet oxygen to the two vinyl groups hence leading to the formation of hydroxyaldehydes. The involvement of water molecules, recently observed along with the binding of heme in Rhodobacter sphaeroides (RsTSPO) is highly probable. Altogether, these results raise the question of the role of TSPO in heme biosynthesis regulation as a possible scavenger of reactive intermediates.
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Affiliation(s)
- Leeyah Issop
- Inserm U955-IMRB, UPEC, Ecole Nationale Vétérinaire d'Alfort, F-94010, Créteil, France
| | - Luminita Duma
- University of Reims Champagne-Ardenne, CNRS, ICMR UMR 7312, 51687, Reims, France
| | - Stephanie Finet
- IMPMC, UMR 7590 CNRS, Sorbonne Université, MNHN, IRD, 75005, Paris, France
| | - Olivier Lequin
- Sorbonne Université, Ecole normale supérieure, PSL University, CNRS (UMR 7203), Laboratoire des Biomolécules, LBM, 75005, Paris, France
| | - Jean-Jacques Lacapère
- Sorbonne Université, Ecole normale supérieure, PSL University, CNRS (UMR 7203), Laboratoire des Biomolécules, LBM, 75005, Paris, France.
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Yeh PS, Li CC, Lu YS, Chiang YW. Structural Insights into the Binding and Degradation Mechanisms of Protoporphyrin IX by the Translocator Protein TSPO. JACS AU 2023; 3:2918-2929. [PMID: 37885593 PMCID: PMC10598825 DOI: 10.1021/jacsau.3c00514] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/30/2023] [Revised: 09/25/2023] [Accepted: 09/26/2023] [Indexed: 10/28/2023]
Abstract
The 18 kDa translocator protein (TSPO) has gained considerable attention as a clinical biomarker for neuroinflammation and a potential therapeutic target. However, the mechanisms by which TSPO associates with ligands, particularly the endogenous porphyrin ligand protoporphyrin IX (PpIX), remain poorly understood. In this study, we employed mutagenesis- and spectroscopy-based functional assays to investigate TSPO-mediated photo-oxidative degradation of PpIX and identify key residues involved in the reaction. We provide structural evidence using electron spin resonance, which sheds light on the highly conserved intracellular loop (LP1) connecting transmembrane 1 (TM1) and TM2. Our findings show that LP1 does not act as a lid to regulate ligand binding; instead, it interacts strongly with the TM3-TM4 linker (LP3) to stabilize the local structure of LP3. This LP1-LP3 interaction is crucial for maintaining the binding pocket structure, which is essential for proper ligand binding. Our results also demonstrate that PpIX accesses the pocket through the lipid bilayer without requiring conformational changes in TSPO. This study provides an improved understanding of TSPO-mediated PpIX degradation, highlighting potential therapeutic strategies to regulate the reaction.
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Affiliation(s)
- Pei-Shan Yeh
- Department of Chemistry, National Tsing Hua University, Hsinchu 300-044, Taiwan
| | - Chieh-Chin Li
- Department of Chemistry, National Tsing Hua University, Hsinchu 300-044, Taiwan
| | - Yi-Shan Lu
- Department of Chemistry, National Tsing Hua University, Hsinchu 300-044, Taiwan
| | - Yun-Wei Chiang
- Department of Chemistry, National Tsing Hua University, Hsinchu 300-044, Taiwan
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