RESUMEN

The specific kinetics and thermodynamics of protein-protein interactions underlie the molecular mechanisms of cellular functions; hence the characterization of these interaction parameters is central to the quantitative understanding of physiological and pathological processes. Many methods have been developed to study protein-protein interactions, which differ in various features including the interaction detection principle, the sensitivity, whether the method operates in vivo, in vitro, or in silico, the temperature control, the use of labels, immobilization, the amount of sample required, the number of measurements that can be accomplished simultaneously, or the cost. Bio-Layer Interferometry (BLI) is a label-free biophysical method to measure the kinetics of protein-protein interactions. Label-free interaction assays are a broad family of methods that do not require protein modifications (other than immobilization) or labels such as fusions with fluorescent proteins or transactivating domains or chemical modifications like biotinylation or reaction with radionuclides. Besides BLI, other label-free techniques that are widely used for determining protein-protein interactions include surface plasmon resonance (SPR), thermophoresis, and isothermal titration calorimetry (ITC), among others.

Asunto(s)

Proteínas , Resonancia por Plasmón de Superficie , Unión Proteica , Termodinámica , Proteínas/química , Interferometría/métodos , Cinética

RESUMEN

Leptospirosis is a neglected worldwide zoonosis involving farm animals and domestic pets caused by the Gram-negative spirochete Leptospira interrogans. This bacterium deploys a variety of immune evasive mechanisms, some of them targeted at the complement system of the host's innate immunity. In this work, we have solved the X-ray crystallographic structure of L. interrogans glyceraldehyde-3-phosphate dehydrogenase (GAPDH) to 2.37-Å resolution, a glycolytic enzyme that has been shown to exhibit moonlighting functions that potentiate infectivity and immune evasion in various pathogenic organisms. Besides, we have characterized the enzyme's kinetic parameters toward the cognate substrates and have proven that the two natural products anacardic acid and curcumin are able to inhibit L. interrogans GAPDH at micromolar concentration through a noncompetitive inhibition modality. Furthermore, we have established that L. interrogans GAPDH can interact with the anaphylatoxin C5a of human innate immunity in vitro using bio-layer interferometry and a short-range cross-linking reagent that tethers free thiol groups in protein complexes. To shed light into the interaction between L. interrogans GAPDH and C5a, we have also carried out cross-link guided protein-protein docking. These results suggest that L. interrogans could be placed in the growing list of bacterial pathogens that exploit glycolytic enzymes as extracellular immune evasive factors. Analysis of the docking results indicates a low affinity interaction that is consistent with previous evidence, including known binding modes of other α-helical proteins with GAPDH. These findings allow us to propose L. interrogans GAPDH as a potential immune evasive factor targeting the complement system.

Asunto(s)

Leptospira interrogans , Leptospirosis , Animales , Humanos , Inmunidad Innata , Proteínas del Sistema Complemento , Gliceraldehído-3-Fosfato Deshidrogenasas , Anafilatoxinas

RESUMEN

Hidradenitis suppurativa (HS) is a chronic auto-inflammatory skin disease with a complex and multifactorial pathogenesis involving both the innate and adaptive immune system. Despite limited evidence for local complement activation, conflicting results have been published on the role of systemic complement activation in HS. It was hypothesized that complement was consumed in highly inflamed HS skin, trapping complement from the circulation. Therefore, the aim of this study was to evaluate this local complement deposition in HS skin lesions using routine and commonly used complement antibodies.Direct immunofluorescence for C1q, C3c, C4d, C5b-9, and properdin was performed on frozen tissue sections of 19 HS patients and 6 controls. C5a receptor 1 (C5aR1) was visualized using immunohistochemistry. Overall, we found no significant local complement deposition in HS patients versus controls regarding C1q, C3c, C4d, C5b-9, or properdin on either vessels or immune cells. C5aR1 expression was exclusively found on immune cells, predominantly neutrophilic granulocytes, but not significantly different relatively to the total infiltrate in HS lesions compared with controls. In conclusion, despite not being able to confirm local complement depositions of C1q, C3c, C4d, or properdin using highly sensitive and widely accepted techniques, the increased presence of C5aR1 positive immune cells in HS suggests the importance of complement in the pathogenesis of HS and supports emerging therapies targeting this pathway.

Asunto(s)

Hidradenitis Supurativa , Activación de Complemento , Complemento C1q , Complejo de Ataque a Membrana del Sistema Complemento , Humanos , Inflamación , Properdina , Receptor de Anafilatoxina C5a

RESUMEN

Coronavirus disease-2019 (COVID-19) was declared as a pandemic by WHO in March 2020. SARS-CoV-2 causes a wide range of illness from asymptomatic to life-threatening. There is an essential need to identify biomarkers to predict disease severity and mortality during the earlier stages of the disease, aiding treatment and allocation of resources to improve survival. The aim of this study was to identify at the time of SARS-COV-2 infection patients at high risk of developing severe disease associated with low survival using blood parameters, including inflammation and coagulation mediators, vital signs, and pre-existing comorbidities. This cohort included 89 multi-ethnic COVID-19 patients recruited between July 14th and October 20th 2020 in Doha, Qatar. According to clinical severity, patients were grouped into severe (n=33), mild (n=33) and asymptomatic (n=23). Common routine tests such as complete blood count (CBC), glucose, electrolytes, liver and kidney function parameters and markers of inflammation, thrombosis and endothelial dysfunction including complement component split product C5a, Interleukin-6, ferritin and C-reactive protein were measured at the time COVID-19 infection was confirmed. Correlation tests suggest that C5a is a predictive marker of disease severity and mortality, in addition to 40 biological and physiological parameters that were found statistically significant between survivors and non-survivors. Survival analysis showed that high C5a levels, hypoalbuminemia, lymphopenia, elevated procalcitonin, neutrophilic leukocytosis, acute anemia along with increased acute kidney and hepatocellular injury markers were associated with a higher risk of death in COVID-19 patients. Altogether, we created a prognostic classification model, the CAL model (C5a, Albumin, and Lymphocyte count) to predict severity with significant accuracy. Stratification of patients using the CAL model could help in the identification of patients likely to develop severe symptoms in advance so that treatments can be targeted accordingly.

Asunto(s)

Biomarcadores/sangre , COVID-19/sangre , COVID-19/mortalidad , Complemento C5a/análisis , Gravedad del Paciente , Adulto , Anciano , COVID-19/complicaciones , Estudios de Cohortes , Femenino , Humanos , Hipoalbuminemia/mortalidad , Hipoalbuminemia/virología , Recuento de Linfocitos , Linfopenia/mortalidad , Linfopenia/virología , Masculino , Persona de Mediana Edad , Pronóstico , Estudios Prospectivos , Qatar , SARS-CoV-2

RESUMEN

Innate immune complement activation generates the C3 and C5 protein cleavage products C3a and C5a, defined classically as anaphylatoxins. C3a activates C3aR, while C5a activates two receptors (C5aR1 and C5aR2) to exert their immunomodulatory activities. The non-peptide compound, SB290157, was originally reported in 2001 as the first C3aR antagonist. In 2005, the first report on the non-selective nature of SB290157 was published, where the compound exerted clear agonistic, not antagonistic, activity in variety of cells. Other studies also documented the non-selective activities of this drug in vivo. These findings severely hamper data interpretation regarding C3aR when using this compound. Unfortunately, given the dearth of C3aR inhibitors, SB290157 still remains widely used to explore C3aR biology (>70 publications to date). Given these issues, in the present study we aimed to further explore SB290157's pharmacological selectivity by screening the drug against three human anaphylatoxin receptors, C3aR, C5aR1 and C5aR2, using cell models. We identified that SB290157 exerts partial agonist activity at C5aR2 by mediating ß-arrestin recruitment at higher compound doses. This translated to a functional outcome in both human and mouse primary macrophages, where SB290157 significantly dampened C5a-induced ERK signaling. We also confirmed that SB290157 acts as a potent agonist at human C3aR in transfected cells, but as an antagonist in primary human macrophages. Our results therefore provide even more caution against using SB290157 as a research tool to explore C3aR function. Given the reported immunomodulatory and anti-inflammatory activities of C5aR2 agonism, any function observed with SB290157 could be due to these off-target activities.

RESUMEN

LPS-induced lung injury in the mouse is one of the most robust experimental models used for studies of acute lung injury (ALI) and acute respiratory distress syndrome in humans. Prior clinical and experimental studies support an important role for complement activation, particularly production of C5a, in the pathophysiology of human ALI/acute respiratory distress syndrome. In the mouse model, however, the precise role of C5a and its receptors is unclear. C5L2, an enigmatic second receptor for C5a, has been characterized, and results have generated substantial debate regarding its in vivo function. Our previous work with human neutrophils revealed a unique role for C5L2 in negatively modulating C5a-C5a receptor (C5aR)-mediated cellular activation, in which antibody-mediated blockade of C5L2 resulted in augmented C5a-C5aR responses. Here, we demonstrate that C5L2-/- mice (BALB/c background) administered intranasal LPS exhibit significantly more airway edema and hemorrhage than do wild-type animals. Bronchoalveolar lavage fluid and lung homogenates have significantly more neutrophils and myeloperoxidase activity, as well as proinflammatory cytokines and chemokines. When a blocking antibody against the C5aR was administered before LPS administration, the increased neutrophilic infiltration and cytokine levels were reversed. Thus, our data show not only that C5a contributes significantly to LPS-induced ALI in the mouse, but also that C5L2 plays an important antiinflammatory role in this model through actions resulting at least in part from negative modulation of C5a receptor activation.

Asunto(s)

Lesión Pulmonar Aguda/metabolismo , Lesión Pulmonar Aguda/patología , Receptores de Quimiocina/metabolismo , Lesión Pulmonar Aguda/genética , Lesión Pulmonar Aguda/fisiopatología , Administración Intranasal , Animales , Líquido del Lavado Bronquioalveolar , Quimiocinas/genética , Quimiocinas/metabolismo , Edema/complicaciones , Edema/patología , Edema/fisiopatología , Regulación de la Expresión Génica , Hemorragia/complicaciones , Hemorragia/patología , Hemorragia/fisiopatología , Mediadores de Inflamación/metabolismo , Lipopolisacáridos/administración & dosificación , Pulmón/patología , Ratones Endogámicos BALB C , Neutrófilos/metabolismo , Peroxidasa/metabolismo , Receptor de Anafilatoxina C5a , Receptores de Quimiocina/antagonistas & inhibidores , Receptores de Quimiocina/deficiencia , Mecánica Respiratoria , Receptores Toll-Like/genética , Receptores Toll-Like/metabolismo

RESUMEN

Although complement is a known contributor to biomaterial-induced complications, pathological implications and therapeutic options remain to be explored. Here we investigated the involvement of complement in the inflammatory response to polypropylene meshes commonly used for hernia repair. In vitro assays revealed deposition of complement activation fragments on the mesh after incubation in plasma. Moreover, significant mesh-induced complement and granulocyte activation was observed in plasma and leukocyte preparations, respectively. Pretreatment of plasma with the complement inhibitor compstatin reduced opsonization >2-fold, and compstatin and a C5a receptor antagonist (C5aRa) impaired granulocyte activation by 50 and 67%, respectively. We established a clinically relevant mouse model of implantation and could confirm deposition of C3 activation fragments on mesh implants in vivo using immunofluorescence. In meshes extracted after subcutaneous or peritoneal implantation, the amount of immune cell infiltrate in mice deficient in key complement components (C3, C5aR), or treated with C5aRa, was approximately half of that observed in wild-type littermates or mice treated with inactive C5aRa, respectively. Our data suggest that implantation of a widely used surgical mesh triggers the formation of an inflammatory cell microenvironment at the implant site through complement activation, and indicates a path for the therapeutic modulation of implant-related complications.

Asunto(s)

Materiales Biocompatibles/farmacología , Activación de Complemento/efectos de los fármacos , Inflamación/prevención & control , Polipropilenos/farmacología , Animales , Antígeno CD11b/metabolismo , Complemento C3/genética , Complemento C3/metabolismo , Citometría de Flujo , Granulocitos/efectos de los fármacos , Granulocitos/metabolismo , Humanos , Implantes Experimentales/efectos adversos , Inflamación/etiología , Inflamación/metabolismo , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Microscopía Fluorescente , Proteínas Opsoninas/metabolismo , Péptidos Cíclicos/farmacología , Receptor de Anafilatoxina C5a/genética , Receptor de Anafilatoxina C5a/metabolismo , Receptores de Quimiocina/metabolismo

RESUMEN

Objective:To study the blocking effects of anti-sense peptide of C5a on the adhesion between pulmonary vascular endothelial cell(PVEC) and neutrophil resulting from C5a anaphylatoxin.Methods:It was determined by Flowcytometry that the change of adhesion molecule expression on PVEC and the activity of MPO in PMN was determined after adhesion.Results:In response to C5a after interactions with several concentrations of anti-sense peptide R4, the expression of P-Selectin on PVEC decreased significantly and reached the minimum at the concentration of 5 000 ng/ml, and the activity of MPO in PMN reduced by 40% at the concentration of 5 000 ng/ml of anti-sense peptide R4.Conclusion:The results suggested that anti-sense peptide of C5a has significant blocking effects on C5a anaphylatoxin.

RESUMEN

Objective:To discover some high hydrophilic profiles of the human C5a anaphylatoxin based on relationship between the structure and function of the protein and the protein molecular design principles.Methods:The peptides were synthesized by 431A automatic peptide synthesizer,purified by PHLC and confirmed by caplilliary electrophoresis.Results:The N terminus No.9 30 profile of the C5aR(P22) could interacte with anti C5aR McAb(S5/1,from Serotic Co.),as determined by ELISA.Furthermore,it could be inhibited OD490 values remarkably by 10.0 ?g/L rhC5a(P