9 research outputs found
Structural characterization of a bacterial antibody-degrading system
No full textLes mycoplasmes sont à l'origine de plusieurs maladies chroniques chez les espèces animales et provoquent des infections telles que la pneumonie et des infections sexuellement transmissibles chez l'être humain. Ils ont développé des stratégies pour échapper à la réponse immunitaire de l'hôte, notamment via le système de dégradation des anticorps Mycoplasma Immunoglobulin Binding (MIB) - Mycoplasma Immunoglobulin Protease (MIP). Le domaine Fab de nombreux types d'immunoglobulines est reconnu par MIB. Cette interaction permet la dissociation anticorps-antigène et l'action ciblée de la sérine protéase MIP, qui clive le lien entre les domaines CH et VH de l'anticorps.Pour comprendre le mécanisme moléculaire de ce système, les structures du système de dégradation des anticorps MIB-MIP en complexe avec des anticorps à différents états du mécanisme ont été obtenues en utilisant la microscopie cryo-électronique à particules isolées.La structure a permis de comprendre l'architecture du complexe dans un mécanisme « d’étreinte de la mort » inédit. La structure montre que MIB interagit principalement avec la chaîne légère du Fab, ce qui entraîne un changement radical de la structure du site de liaison de l'antigène du Fab. Les régions déterminant la complémentarité des domaines VL et VH sont séparées, ce qui entraîne la dissociation du complexe antigène-anticorps. Cette rupture du paratope permet le recrutement de MIP qui interagit avec la chaîne lourde du Fab et contient une triade catalytique de sérine protéase qui est idéalement placée pour cliver cette chaîne. De plus, des expériences de résonance de plasmons de surface ont mis en évidence le comportement inattendu de MIB qui est la première protéine identifiée qui dissocie activement divers complexes immuns.La résolution de ces structures cryoEM révèle la base moléculaire du mécanisme de liaison, de dissociation et de dégradation de l'anticorps et permet de mieux comprendre le système MIB-MIP. MIB et MIP apparaissent comme de nouvelles cibles thérapeutiques pour lutter contre le mécanisme d'évasion immunitaire des mycoplasmes.Mycoplasmas cause various chronic diseases in livestock species and induce infections such as pneumonia and sexually transmitted infections in humans. They have evolved strategies to evade the host immune response, including the Mycoplasma Immunoglobulin Binding (MIB) - Mycoplasma Immunoglobulin Protease (MIP) antibody degrading system. The Fab domain of many types of immunoglobulins is recognized by MIB. This interaction mediates antibody-antigen dissociation and the targeted activity of the serine protease MIP, which cleaves the linker between the CH and VH domains of the antibody.To understand the molecular basis of this system, the structures of the MIB-MIP antibody degrading system in complex with antibodies at different state of the mechanism were obtained using single particle cryo-electron microscopy.The structure allowed us to understand the intricate architecture of the complex in a previously unseen “hug of death” mechanism. The structure shows that MIB interacts mainly with the Fab’s light chain leading to a drastic change in the structure of the Fab’s antigen binding site. The complementarity determining regions of the VL and VH domains are separated resulting in the dissociation of the antigen- antibody complex. This paratope disruption allows MIP recruitment that interacts with the Fab’s heavy chain and contains a serine protease catalytic triad that is ideally placed to cleave this chain. In addition, surface plasmon resonance experiments highlighted MIB’s unexpected behavior which is the first identified protein that actively dissociate various immune complexes.Solving this cryoEM structures reveals the molecular basis of the antibody binding, dissociation and degradation mechanism and further our understanding of the MIB-MIP system. MIB and MIP are emerging as new therapeutic targets to fight against the immune evasion mechanism of mycoplasma
Caractérisation structurale d’un système bactérien de dégradation des anticorps
No full textMycoplasmas cause various chronic diseases in livestock species and induce infections such as pneumonia and sexually transmitted infections in humans. They have evolved strategies to evade the host immune response, including the Mycoplasma Immunoglobulin Binding (MIB) - Mycoplasma Immunoglobulin Protease (MIP) antibody degrading system. The Fab domain of many types of immunoglobulins is recognized by MIB. This interaction mediates antibody-antigen dissociation and the targeted activity of the serine protease MIP, which cleaves the linker between the CH and VH domains of the antibody.To understand the molecular basis of this system, the structures of the MIB-MIP antibody degrading system in complex with antibodies at different state of the mechanism were obtained using single particle cryo-electron microscopy.The structure allowed us to understand the intricate architecture of the complex in a previously unseen “hug of death” mechanism. The structure shows that MIB interacts mainly with the Fab’s light chain leading to a drastic change in the structure of the Fab’s antigen binding site. The complementarity determining regions of the VL and VH domains are separated resulting in the dissociation of the antigen- antibody complex. This paratope disruption allows MIP recruitment that interacts with the Fab’s heavy chain and contains a serine protease catalytic triad that is ideally placed to cleave this chain. In addition, surface plasmon resonance experiments highlighted MIB’s unexpected behavior which is the first identified protein that actively dissociate various immune complexes.Solving this cryoEM structures reveals the molecular basis of the antibody binding, dissociation and degradation mechanism and further our understanding of the MIB-MIP system. MIB and MIP are emerging as new therapeutic targets to fight against the immune evasion mechanism of mycoplasma.Les mycoplasmes sont à l'origine de plusieurs maladies chroniques chez les espèces animales et provoquent des infections telles que la pneumonie et des infections sexuellement transmissibles chez l'être humain. Ils ont développé des stratégies pour échapper à la réponse immunitaire de l'hôte, notamment via le système de dégradation des anticorps Mycoplasma Immunoglobulin Binding (MIB) - Mycoplasma Immunoglobulin Protease (MIP). Le domaine Fab de nombreux types d'immunoglobulines est reconnu par MIB. Cette interaction permet la dissociation anticorps-antigène et l'action ciblée de la sérine protéase MIP, qui clive le lien entre les domaines CH et VH de l'anticorps.Pour comprendre le mécanisme moléculaire de ce système, les structures du système de dégradation des anticorps MIB-MIP en complexe avec des anticorps à différents états du mécanisme ont été obtenues en utilisant la microscopie cryo-électronique à particules isolées.La structure a permis de comprendre l'architecture du complexe dans un mécanisme « d’étreinte de la mort » inédit. La structure montre que MIB interagit principalement avec la chaîne légère du Fab, ce qui entraîne un changement radical de la structure du site de liaison de l'antigène du Fab. Les régions déterminant la complémentarité des domaines VL et VH sont séparées, ce qui entraîne la dissociation du complexe antigène-anticorps. Cette rupture du paratope permet le recrutement de MIP qui interagit avec la chaîne lourde du Fab et contient une triade catalytique de sérine protéase qui est idéalement placée pour cliver cette chaîne. De plus, des expériences de résonance de plasmons de surface ont mis en évidence le comportement inattendu de MIB qui est la première protéine identifiée qui dissocie activement divers complexes immuns.La résolution de ces structures cryoEM révèle la base moléculaire du mécanisme de liaison, de dissociation et de dégradation de l'anticorps et permet de mieux comprendre le système MIB-MIP. MIB et MIP apparaissent comme de nouvelles cibles thérapeutiques pour lutter contre le mécanisme d'évasion immunitaire des mycoplasmes
CryoEM Workflow Acceleration with Feret Signatures
No full textCommon challenges in cryogenic electron microscopy, such as orientation bias, conformational diversity, and 3D misclassification, complicate single particle analysis and lead to significant resource expenditure. We previously introduced an in silico method using the maximum Feret diameter distribution, the Feret signature, to characterize sample heterogeneity of disc-shaped samples. Here, we expanded the Feret signature methodology to identify preferred orientations of samples containing arbitrary shapes with only about 1000 particles required. This method enables real-time adjustments of data acquisition parameters for optimizing data collection strategies or aiding in decisions to discontinue ineffective imaging sessions. Beyond detecting preferred orientations, the Feret signature approach can serve as an early-warning system for inconsistencies in classification during initial image processing steps, a capability that allows for strategic adjustments in data processing. These features establish the Feret signature as a valuable auxiliary tool in the context of single particle analysis, significantly accelerating the structure determination process
Study of the interaction between indole-based compounds and biologically relevant G-quadruplexes
No full textThe mycoplasma surface proteins MIB and MIP promote the dissociation of the antibody-antigen interaction
No full textInternational audienceMycoplasma immunoglobulin binding (MIB) and mycoplasma immunoglobulin protease (MIP) are surface proteins found in the majority of mycoplasma species, acting sequentially to capture antibodies and cleave off their V H domains. Cryo-electron microscopy structures show how MIB and MIP bind to a Fab fragment in a "hug of death" mechanism. As a result, the orientation of the V L and V H domains is twisted out of alignment, disrupting the antigen binding site. We also show that MIB-MIP has the ability to promote the dissociation of the antibody-antigen complex. This system is functional in cells and protects mycoplasmas from antibody-mediated agglutination. These results highlight the key role of the MIB-MIP system in immunity evasion by mycoplasmas through an unprecedented mechanism, and open exciting perspectives to use these proteins as potential tools in the antibody field
Structural characterization of the antibody degradation complex MIB-MIP and functional insights on its impact on the immune system
No full textBackground: The ability of mycoplasma to cause chronic infections suggests that they evolved mechanisms to bypass or counter their host’s immune system. We previously characterized the MIB-MIP complex, a widespread system in mycoplasma that selectively captures and cleaves IgG. Methods: In this work, we further studied this system by solving the 3D structure of MIB-MIP bound to their target antibody. Based on these structural data, we analyzed the functionality of the system in vitro and in cellulo.Results: Solving the 3D structure highlights the molecular determinants of the MIB-MIP mechanism. In particular, it suggests that MIB-MIP can target and cleave antibodies that are already bound to an antigen, which was then successfully verified in vitro. We also show that the MIB-MIP system can bind and degrade the three main classes of antibodies (IgG, sIgA and IgM), but that in cellulo this function is focused solely on antibodies targeting the cell surface and ignores non-specific immunoglobulins. We also provide a comparative analysis of the 4 pairs of MIB-MIP encoded in the genome of the model Mycoplasma mycoides subsp. capri GM12. Our results show that they are functionally redundant and fully cross-reactive, suggesting that their sequence diversity is linked to antigenic variation.Conclusion: We showed that mycoplasma have a mechanism dedicated to destroying specific antibodies, the main components of the humoral response. The in vivo function of this system is to be further studied, but our data shed new light on the host-pathogen interaction of these bacteria
Structural characterization of the antibody degradation complex MIB-MIP and functional insights on its impact on the immune system
No full textInternational audienceBackground: The ability of mycoplasma to cause chronic infections suggests that they evolved mechanisms to bypass or counter their host’s immune system. We previously characterized the MIB-MIP complex, a widespread system in mycoplasma that selectively captures and cleaves IgG. Methods: In this work, we further studied this system by solving the 3D structure of MIB-MIP bound to their target antibody. Based on these structural data, we analyzed the functionality of the system in vitro and in cellulo.Results: Solving the 3D structure highlights the molecular determinants of the MIB-MIP mechanism. In particular, it suggests that MIB-MIP can target and cleave antibodies that are already bound to an antigen, which was then successfully verified in vitro. We also show that the MIB-MIP system can bind and degrade the three main classes of antibodies (IgG, sIgA and IgM), but that in cellulo this function is focused solely on antibodies targeting the cell surface and ignores non-specific immunoglobulins. We also provide a comparative analysis of the 4 pairs of MIB-MIP encoded in the genome of the model Mycoplasma mycoides subsp. capri GM12. Our results show that they are functionally redundant and fully cross-reactive, suggesting that their sequence diversity is linked to antigenic variation.Conclusion: We showed that mycoplasma have a mechanism dedicated to destroying specific antibodies, the main components of the humoral response. The in vivo function of this system is to be further studied, but our data shed new light on the host-pathogen interaction of these bacteria
Easy synthesis and ring-opening polymerization of 5-Z-amino-δ-valerolactone: New degradable amino-functionalized (Co)polyesters
No full textInternational audienc
Controlled Anchoring of Iron-Oxide Nanoparticles on Polymeric Nanofibers: Easy Access to Core@Shell Organic-Inorganic Nanocomposites for Magneto-Scaffolds
No full textComposites combining superparamagnetic iron oxide nanoparticles (SPIONs) and polymers are largely present in modern (bio)materials. However, while SPIONs embedded in polymer matrices are classically reported, the mechanical and degradation properties of the polymer scaffold are impacted by the SPIONs. Therefore, the controlled anchoring of SPIONs onto polymer surfaces is still a major challenge. Herein, we propose an efficient strategy for the direct and uniform anchoring of SPIONs on the surface of functionalized-polylactide (PLA) nanofibers via a simple free ligand exchange procedure to design PLA@SPIONs core@shell nanocomposites. The resulting PLA@SPIONs hybrid biomaterials are characterized by electron microscopy (SEM and TEM) and EDXS analysis, to probe the morphology and detect elements present at the organic/inorganic interface, respectively. A monolayer of SPIONs with a complete and homogeneous coverage is observed on the surface of PLA nanofibers. Magnetization experiments show that magnetic properties of the nanoparticles are well-preserved after their grafting on the PLA fibers and that the size of the nanoparticles does not change. The absence of cytotoxicity, combined with a high sensitivity of detection in MRI both in vitro and in vivo make these hybrid nanocomposites attractive for the development of magnetic biomaterials for biomedical applications
