RESUMEN
BACKGROUND AND OBJECTIVE: Hereditary angioedema with C1-inhibitor deficiency (C1-INH-HAE) and acquired angioedema related to angiotensin-converting enzyme (ACE) inhibitors (ACEI-AAE) are types of bradykinin-mediated angioedema without wheals characterized by recurrent swelling episodes. Recent evidence suggests that a state of "vascular preconditioning" predisposes individuals to attacks, although no data are available on possible structural alterations of the vessels. Objective: This study aims to compare the features of nailfold capillaries to highlight possible structural anomalies between patients affected by C1-INH-HAE and controls and between patients with ACEI-AAE and hypertensive controls. METHODS: We used nailfold videocapillaroscopy (NVC) to assess the following: apical, internal, and external diameter; loop length; intercapillary distance; and capillary density, distribution, and morphology. Plasma levels of vascular endothelial growth factor (VEGF) A, VEGF-C, angiopoietin (Ang) 1, and Ang2 were also measured. RESULTS: Compared with healthy controls (n=28), C1-INH-HAE patients (n = 34) were characterized by significant structural alterations of the capillaries, such as greater intercapillary distance (216 vs 190 µm), increased apical, internal, and external diameter (28 vs 22 µm; 22 vs 20 µm; and 81 vs 65 µm, respectively), decreased density (4 vs 5 capillaries/mm2), more irregular capillary distribution, and more tortuous morphology. Apical diameter was enlarged in patients with ≥12 attacks per year. In ACEI-AAE patients, NVC showed no alterations with respect to hypertensive controls. NVC performed in 2 C1-INH-HAE patients during attacks showed no changes compared with the remission phase. CONCLUSIONS: We detected major structural capillary alterations in C1-INH-HAE patients, thus confirming the involvement of microcirculation in the pathogenesis of angioedema.
Asunto(s)
Angioedema , Angioedemas Hereditarios , Bradiquinina , Proteína Inhibidora del Complemento C1 , Humanos , Angioscopía Microscópica , Factor A de Crecimiento Endotelial VascularRESUMEN
Background: Hereditary angioedema with C1-inhibitor deficiency (C1-INH-HAE) and acquired angioedema related to angiotensin-converting enzyme (ACE) inhibitors (ACEI-AAE) are types of bradykinin-mediated angioedema without wheals characterized by recurrent swelling episodes. Recent evidence suggests that a state of vascular preconditioning predisposes individuals to attacks, although no data are available on possible structural alterations of the vessels. Objective: This study aims to compare the features of nailfold capillaries to highlight possible structural anomalies between patients affected by C1-INH-HAE and controls and between patients with ACEI-AAE and hypertensive controls.Methods: We used nailfold videocapillaroscopy (NVC) to assess the following: apical, internal, and external diameter; loop length; intercapillary distance; and capillary density, distribution, and morphology. Plasma levels of vascular endothelial growth factor (VEGF) A, VEGF-C, angiopoietin (Ang) 1, and Ang2 were also measured. Results: Compared with healthy controls (n=28), C1-INH-HAE patients (n = 34) were characterized by significant structural alterations of the capillaries, such as greater intercapillary distance (216 vs 190 μm), increased apical, internal, and external diameter (28 vs 22 μm; 22 vs 20 μm; and 81 vs 65 μm, respectively), decreased density (4 vs 5 capillaries/mm2), more irregular capillary distribution, and more tortuous morphology. Apical diameter was enlarged in patients with ≥12 attacks per year. In ACEI-AAE patients, NVC showed no alterations with respect to hypertensive controls. NVC performed in 2 C1-INH-HAE patients during attacks showed no changes compared with the remission phase. Conclusions: We detected major structural capillary alterations in C1-INH-HAE patients, thus confirming the involvement of microcirculation in the pathogenesis of angioedema (AU)
Antecedentes: Tanto el angioedema hereditario con deficiencia de inhibidor del C1 (C1-INH-HAE) como el angioedema adquiridorelacionado con los inhibidores de la ECA (ACEI-AAE), son dos tipos de angioedema mediados por bradicinina que cursan con episodiosde inflamación recurrente sin acompañarse de habones. Existe evidencia de la existencia de un estado de "preacondicionamiento vascular"que predispone a estos pacientes a los ataques, pero no hay datos disponibles sobre las posibles alteraciones estructurales de los vasos.Objetivo: Este estudio tiene como objetivo el evaluar las características de los capilares de la base ungueal para identificar posiblesanomalías estructurales en los pacientes afectados por C1-INH-HAE en comparación con la población sana, y en los pacientes con ACEIAAE en comparación con controles con hipertensión arterial.Métodos: Mediante videocapilaroscopia de la base ungueal (NVC), se evaluaron: los diámetros apical, interno y externo, la longitud delasa, la distancia intercapilar, la densidad capilar, su distribución y su morfología. También se midieron los niveles plasmáticos del factorde crecimiento endotelial vascular (VEGF)-A, VEGF-C, angiopoyetina (Ang)1 y Ang2.Resultados: En los pacientes con C1-INH-HAE (n = 34) se observaron alteraciones estructurales de los capilares significativas, en comparacióncon los controles sanos (n = 28): mayor distancia intercapilar (216 frente a 190 µm), aumento del diámetro apical, interno y externo(28 frente a 22 µm; 22 frente a 20 µm; y 81 frente a 65 µm, respectivamente), disminución de la densidad (4 frente a 5 capilares/mm2),distribución capilar más irregular y una morfología más tortuosa. El diámetro apical fue mayor en aquellos pacientes con ≥12 ataques/año. En los pacientes con ACEI-AAE, las NVC no mostraron alteraciones al ser comparadas con las de los controles hipertensos. Las NVC realizadas en dos pacientes ...(AU)
Asunto(s)
Humanos , Masculino , Femenino , Niño , Adolescente , Adulto Joven , Adulto , Persona de Mediana Edad , Anciano , Angioedema/diagnóstico , Proteína Inhibidora del Complemento C1 , Factor A de Crecimiento Endotelial Vascular , Angioscopía Microscópica , Estudios de Casos y ControlesRESUMEN
BACKGROUND AND OBJECTIVE: Angiotensin-converting enzyme inhibitor-associated angioedema (ACEI-AAE) affects 0.1%-0.7% of patients treated with ACEIs. While previous research suggests that angioedema attacks result from increased vascular permeability, the pathogenesis is not completely understood. Objective: This study aimed to describe the clinical, genetic, and laboratory parameters of ACEI-AAE patients and to investigate the role of vascular endothelial growth factors A and C (VEGF-A and VEGF-C), angiopoietins 1 and 2 (Ang1/Ang2), and secretory phospholipase A2 (sPLA2) in the pathogenesis of ACEI-AAE. METHODS: The clinical and laboratory data of ACEI-AAE patients were collected from 2 angioedema reference centers. Healthy volunteers and ACEI-treated patients without angioedema were enrolled to compare laboratory parameters. Genetic analyses to detect mutations in the genes SERPING1, ANGPT1, PLG, and F12 were performed in a subset of patients. RESULTS: A total of 51 patients (57% male) were diagnosed with ACEI-AAE. The average time to onset of symptoms from the start of ACEI therapy was 3 years (range, 30 days-20 years). The most commonly affected sites were the lips (74.5%), tongue (51.9%), and face (41.2%). Switching from ACEIs to sartans was not associated with an increased risk of angioedema in patients with a history of ACEIAAE. VEGF-A, VEGF-C, and sPLA2 plasma levels were higher in ACEI-AAE patients than in the controls. Ang1/2 concentrations remained unchanged. No mutations were detected in the genes analyzed. CONCLUSIONS: Our data suggest that sartans are a safe therapeutic alternative in ACEI-AAE patients. Increased concentrations of VEGF-A, VEGF-C, and sPLA2 in ACEI-AAE patients suggest a possible role of these mediators in the pathogenesis of ACEI-AAE.
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Angioedema/inmunología , Inhibidores de la Enzima Convertidora de Angiotensina/efectos adversos , Antígenos de Plaqueta Humana/sangre , Factor A de Crecimiento Endotelial Vascular/sangre , Factor C de Crecimiento Endotelial Vascular/sangre , Adulto , Anciano , Anciano de 80 o más Años , Angiopoyetina 1/sangre , Angiopoyetina 2/sangre , Bloqueadores del Receptor Tipo 1 de Angiotensina II/uso terapéutico , Inhibidores de la Enzima Convertidora de Angiotensina/uso terapéutico , Femenino , Humanos , Masculino , Persona de Mediana Edad , Riesgo , Cambio de Tratamiento , Regulación hacia ArribaAsunto(s)
Angioedemas Hereditarios/diagnóstico , Angioedemas Hereditarios/inmunología , Autoanticuerpos/sangre , Anciano de 80 o más Años , Angioedemas Hereditarios/sangre , Angioedemas Hereditarios/patología , Proteínas Inactivadoras del Complemento 1/genética , Proteínas Inactivadoras del Complemento 1/inmunología , Proteína Inhibidora del Complemento C1 , Femenino , Expresión Génica , HumanosRESUMEN
BACKGROUND: Hereditary angioedema with C1 inhibitor deficiency (C1-INH-HAE) is a rare inherited genetic disease characterized by recurrent swelling episodes of the skin, gastrointestinal tract, and upper airways. Angioedema attacks result from increased vascular permeability due to the release of bradykinin from high molecular weight kininogen. Currently, there are no biomarkers predicting the frequency of angioedema attacks. Vascular permeability is modulated by several factors, including vascular endothelial growth factors (VEGFs) and angiopoietins (Angs). As increased circulating levels of VEGFs and Angs have been observed in diseases associated with higher vascular permeability (e.g., systemic capillary leak syndrome and sepsis), we sought to analyze plasma concentrations of VEGFs and Angs in patients with C1-INH-HAE. METHODS: Sixty-eight healthy controls and 128 patients with C1-INH-HAE were studied. Concentrations of angiogenic (VEGF-A, Ang1, Ang2), anti-angiogenic (VEGF-A165b ) and lymphangiogenic (VEGF-C) factors were evaluated by ELISA. C1-INH functional activity was assessed by EIA. RESULTS: Plasma concentrations of VEGF-A, VEGF-C, Ang1, and Ang2 were higher in patients with C1-INH-HAE in remission than in healthy controls. Concentration of VEGF-A was further increased in patients with lower C1-INH functional activity. Patients with C1-INH-HAE experiencing more than 12 angioedema attacks per year were characterized by higher plasma levels of VEGF-A, VEGF-C, and Ang2 compared with the other patients. CONCLUSIONS: We hypothesize that VEGFs and Angs induce a state of 'vascular preconditioning' that may predispose to angioedema attacks. In addition, the identification of increased plasma levels of VEGFs and Angs in patients with C1-INH-HAE may prompt the investigation of VEGFs and Angs as biomarkers of C1-INH-HAE severity.
Asunto(s)
Angioedema Hereditario Tipos I y II/sangre , Factor A de Crecimiento Endotelial Vascular/sangre , Adolescente , Adulto , Angiopoyetina 1/sangre , Angiopoyetina 2/sangre , Biomarcadores , Estudios de Casos y Controles , Niño , Preescolar , Progresión de la Enfermedad , Femenino , Angioedema Hereditario Tipos I y II/diagnóstico , Angioedema Hereditario Tipos I y II/prevención & control , Humanos , Masculino , Persona de Mediana Edad , Índice de Severidad de la Enfermedad , Factor C de Crecimiento Endotelial Vascular/sangre , Adulto JovenRESUMEN
No disponible
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Humanos , Femenino , Anciano de 80 o más Años , Angioedema/complicaciones , Angioedema/diagnóstico , Angioedema/inmunología , Angioedema Hereditario Tipos I y II/inmunología , Metilprednisolona/uso terapéutico , Clorfeniramina/uso terapéutico , Epinefrina/uso terapéutico , Angioedemas Hereditarios/complicaciones , Angioedemas Hereditarios/inmunología , Proteína Inhibidora del Complemento C1/inmunología , Ensayo de Inmunoadsorción Enzimática/métodosRESUMEN
Cytokines act as pleiotropic polypeptides able to regulate inflammatory/immune responses and to provide important signals in physiological and pathological processes. Several cytokines (Th1, Th2, and Th17) seem to be involved in the pathophysiology of Behçet's disease, a chronic immune-mediated disease characterized by oral and genital lesions and ocular inflammation. Its individual susceptibility seems to be modulated by genetic variants in genes codifying these cytokines. Th1 and Th17 seem to be involved in the disease's active phases, and Th2 seems to affect the development or severity of the disease; however, contrasting data are reported. In this study, some genetic variants of the Th1/Th2 cytokine genes were investigated in Sicilian patients and age- and gender-matched controls. Three very significant associations with Behçet's disease were detected, and combined genotypes associated with increased disease risk were identified. Results obtained point to the key role of Th1/Th2 cytokine genetic variants in disease susceptibility.
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Síndrome de Behçet/genética , Síndrome de Behçet/inmunología , Interleucinas/genética , Adulto , Síndrome de Behçet/patología , Femenino , Frecuencia de los Genes , Variación Genética , Genotipo , Humanos , Interleucinas/inmunología , Masculino , Persona de Mediana Edad , Proyectos Piloto , Polimorfismo de Nucleótido Simple , Sicilia , Adulto JovenRESUMEN
Parkin is a RING-between-RING E3 ligase that functions in the covalent attachment of ubiquitin to specific substrates, and mutations in Parkin are linked to Parkinson's disease, cancer and mycobacterial infection. The RING-between-RING family of E3 ligases are suggested to function with a canonical RING domain and a catalytic cysteine residue usually restricted to HECT E3 ligases, thus termed 'RING/HECT hybrid' enzymes. Here we present the 1.58 Å structure of Parkin-R0RBR, revealing the fold architecture for the four RING domains, and several unpredicted interfaces. Examination of the Parkin active site suggests a catalytic network consisting of C431 and H433. In cells, mutation of C431 eliminates Parkin-catalysed degradation of mitochondria, and capture of an ubiquitin oxyester confirms C431 as Parkin's cellular active site. Our data confirm that Parkin is a RING/HECT hybrid, and provide the first crystal structure of an RING-between-RING E3 ligase at atomic resolution, providing insight into this disease-related protein.
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Ubiquitina-Proteína Ligasas/química , Ubiquitina-Proteína Ligasas/metabolismo , Biocatálisis , Dominio Catalítico , Humanos , Mitocondrias/metabolismo , Modelos Moleculares , Mutación , Enfermedad de Parkinson/enzimología , Enfermedad de Parkinson/genética , Fenilalanina , Estructura Terciaria de ProteínaRESUMEN
Icatibant, a bradykinin B2 receptor antagonist, is an established treatment for acute attacks of hereditary angioedema (HAE) with C1-inhibitor (C1-INH) deficiency. We describe our experience with icatibant in eight patients with angioedema because of acquired C1-INH deficiency (AAE). Forty-eight moderate-to-severe attacks were treated with subcutaneous icatibant 30 mg; two moderate attacks resolved without treatment. The median (range) duration of treated attacks (onset to complete resolution) was 9.33 (1.67-39.00) h; durations of the untreated attacks were 72 and 96 h. Symptom improvement following icatibant treatment occurred in 0.5 (0.25-2.10) h and complete resolution in 6.75 (0.50-30.75) h. A single icatibant injection achieved complete symptom resolution in 47 attacks; one facial attack required a second injection. One peripheral attack responded less quickly than other treated attacks. Five patients reported transient injection site reactions. Icatibant appeared to provide effective symptom relief and was generally well tolerated.
Asunto(s)
Antagonistas Adrenérgicos beta/uso terapéutico , Angioedema/tratamiento farmacológico , Angioedema/inmunología , Bradiquinina/análogos & derivados , Proteína Inhibidora del Complemento C1/inmunología , Anciano , Anciano de 80 o más Años , Autoanticuerpos/inmunología , Enfermedades Autoinmunes/tratamiento farmacológico , Enfermedades Autoinmunes/inmunología , Bradiquinina/uso terapéutico , Antagonistas del Receptor de Bradiquinina B2 , Femenino , Humanos , Masculino , Persona de Mediana Edad , Resultado del TratamientoRESUMEN
OBJECTIVE: To evaluate the usefullness of examination of methylation status of selected tumor-supressor genes in early diagnosis of ovarian cancer. DESIGN: Prospective clinical study. SETTING: Department of Gynecology and Obstetrics, Department of Molecular Biology, Jessenius Medical Faculty, Commenius University, Martin, Slovak Republic. METHODS: In this study we analyzed hypermethylation of 5 genes RASSF1A, GSTP, E-cadherin, p16 and APC in ovarian tumor samples from 34 patients - 13 patients with epithelial ovarian cancer, 2 patients with border-line ovarian tumors, 12 patients with benign lesions of ovaries and 7 patients with healthy ovarian tissue. The methylation status of promoter region of tumor-supressor genes was determined by Methylation Specific Polymerase Chain Reaction (MSP) using a nested two-step approach with bisulfite modified DNA template and specific primers. RESULTS: Gene methylation analysis revealed hypermethylation of gene RASSF1A (46%) and GSTP (8%) only in malignant ovarian tissue samples. Ecad, p16 and APC genes were methylated both in maignant and benign tissue samples. Methylation positivity in observed genes was present independently to all clinical stages of ovarian cancer and to tumor grades. However, there was observed a trend of increased number and selective involvement of methylated genes with increasing disease stages. Furthermore, there was no association between positive methylation status and histological subtypes of ovarian carcinomas. CONCLUSION: RASSF1A and GSTP promoter methylation positivity is associated with ovarian cancer. The revealed gene-selective methylation positivity and the increased number of methylated genes with advancing disease stages could be considered as a useful molecular marker for early detection of ovarian cancer. However, there is need to find diagnostic approach of specifically and frequently methylated genes to determining a methylation phenotype for early detection of ovarian malignancies.
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Metilación de ADN , Genes Supresores de Tumor , Neoplasias Ováricas/genética , Adulto , Anciano , Carcinoma Epitelial de Ovario , Femenino , Humanos , Persona de Mediana Edad , Neoplasias Glandulares y Epiteliales/genética , Reacción en Cadena de la Polimerasa , Regiones Promotoras GenéticasRESUMEN
The 626/94 Decree amendment (see Decree 25/2002) regard a series of mandatory measures towards the exposure estimation both for future prevention activities as well as for the efficacy evaluation of measures that have already been carried out. This publication provides an updating on a study of the ten-year follow-up regarding occupational exposure to Cr (VI) in workers exposed to low levels of cromium.
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Cromo/toxicidad , Exposición Profesional/efectos adversos , Estudios de Seguimiento , Humanos , Persona de Mediana Edad , Vigilancia de la Población , Factores de TiempoRESUMEN
The problems of the use/abuse of alcohol need a special attention by the Public Authorities, based on the scientific evidences related to the subject. We would like to define in the present paper the procedures for alcohol testing (and drug testing) in the sailors, following the international aviation authorities (ICAO, JAR-OPS-1, FAA) recommendations. A Working Group was established to study both the scientific and the legal aspects of the problems related to alcohol testing in Italy. Experts from the Università "La Sapienza" and from Alitalia studied the alcohol testing issues abroad to set out criteria, guidelines and procedures for random testing in Italy.
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Medicina Aeroespacial , Consumo de Bebidas Alcohólicas , Etanol/sangre , Detección de Abuso de Sustancias/métodos , Humanos , ItaliaRESUMEN
The small heat-shock proteins (sHSPs) form a diverse family of proteins that are produced in all organisms. They function as chaperone-like proteins in that they bind unfolded polypeptides and prevent uncontrolled protein aggregation. Here, we present parallel cryo-electron microscopy studies of five different sHSP assemblies: Methanococcus jannaschii HSP16.5, human alphaB-crystallin, human HSP27, bovine native alpha-crystallin, and the complex of alphaB-crystallin and unfolded alpha-lactalbumin. Gel-filtration chromatography indicated that HSP16.5 is the most monodisperse, while HSP27 and the alpha-crystallin assemblies are more polydisperse. Particle images revealed a similar trend showing mostly regular and symmetric assemblies for HSP16.5 particles and the most irregular assemblies with a wide range of diameters for HSP27. A symmetry test on the particle images indicated stronger octahedral symmetry for HSP16.5 than for HSP27 or the alpha-crystallin assemblies. A single particle reconstruction of HSP16.5, based on 5772 particle images with imposed octahedral symmetry, resulted in a structure that closely matched the crystal structure. In addition, the cryo-EM reconstruction revealed internal density presumably corresponding to the flexible 32 N-terminal residues that were not observed in the crystal structure. The N termini were found to partially fill the central cavity making it unlikely that HSP16.5 sequesters denatured proteins in the cavity. A reconstruction calculated without imposed symmetry confirmed the presence of at least loose octahedral symmetry for HSP16.5 in contrast to the other sHSPs examined, which displayed no clear overall symmetry. Asymmetric reconstructions for the alpha-crystallin assemblies, with an additional mass selection step during image processing, resulted in lower resolution structures. We interpret the alpha-crystallin reconstructions to be average representations of variable assemblies and suggest that the resolutions achieved indicate the degree of variability. Quaternary structural information derived from cryo-electron microscopy is related to recent EPR studies of the alpha-crystallin domain fold and dimer interface of alphaA-crystallin.
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Proteínas de Choque Térmico/química , Proteínas de Choque Térmico/ultraestructura , Animales , Proteínas Arqueales , Bovinos , Cromatografía en Gel , Microscopía por Crioelectrón , Cristalinas/química , Cristalinas/metabolismo , Cristalinas/ultraestructura , Cristalografía por Rayos X , Proteínas de Choque Térmico/metabolismo , Humanos , Lactalbúmina/química , Lactalbúmina/metabolismo , Lactalbúmina/ultraestructura , Methanococcus/química , Modelos Moleculares , Peso Molecular , Docilidad , Estructura Cuaternaria de ProteínaRESUMEN
alphaA-Crystallin, a member of the small heat shock protein (sHsp) family, is a large multimeric protein composed of 30-40 identical subunits. Its quaternary structure is highly dynamic, with subunits capable of freely and rapidly exchanging between oligomers. We report here the development of a fluorescence resonance energy transfer method for measuring structural compatibility between alphaA-crystallin and other proteins. We found that Hsp27 and alphaB-crystallin readily exchanged with fluorescence-labeled alphaA-crystallin, but not with other proteins structurally unrelated to sHsps. Truncation of 19 residues from the N terminus or 10 residues from the C terminus of alphaA-crystallin did not significantly change its subunit organization or exchange rate constant. In contrast, removal of the first 56 or more residues converts alphaA-crystallin into a predominantly small multimeric form consisting of three or four subunits, with a concomitant loss of exchange activity. These findings suggest residues 20-56 are essential for the formation of large oligomers and the exchange of subunits. Similar results were obtained with truncated Hsp27 lacking the first 87 residues. We further showed that the exchange rate is independent of alphaA-crystallin concentration, suggesting subunit dissociation may be the rate-limiting step in the exchange reaction. Our findings reveal a quarternary structure of alphaA-crystallin, consisting of small multimers of alphaA-crystallin subunits in a dynamic equilibrium with the oligomeric complex.
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Cristalinas/química , Proteínas de Choque Térmico/química , Proteínas de Neoplasias/química , Cristalinas/metabolismo , Colorantes Fluorescentes , Proteínas de Choque Térmico HSP27 , Cinética , Sustancias Macromoleculares , Chaperonas Moleculares , Mutagénesis Sitio-Dirigida , Proteínas de Neoplasias/metabolismo , Estructura Cuaternaria de Proteína , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismo , Eliminación de Secuencia , Espectrometría de FluorescenciaRESUMEN
The authors describe a case of a newborn baby with inborn laryngomucocaele, living 14 days after birth. The newborn baby was looked after with artifical lentilation. Because of the inability of self breathing the baby underwent tracheostomia. The autopsy revealed the presence of laryngomucocaele.
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Enfermedades de la Laringe/congénito , Mucocele/congénito , Adulto , Resultado Fatal , Femenino , Humanos , Recién Nacido , Enfermedades de la Laringe/patología , Masculino , Mucocele/patología , EmbarazoRESUMEN
alphaB-crystallin, a member of the small heat shock protein family, possesses chaperone-like function. Recently, it has been shown that a missense mutation in alphaB-crystallin, R120G, is genetically linked to a desmin-related myopathy as well as to cataracts [Vicart, P., Caron, A., Guicheney, P., Li, A., Prevost, M.-C., Faure, A., Chateau, D., Chapon, F., Tome, F., Dupret, J.-M., et al. (1998) Nat. Genet. 20, 92-95]. By using alpha-lactalbumin, alcohol dehydrogenase, and insulin as target proteins, in vitro assays indicated that R120G alphaB-crystallin had reduced or completely lost chaperone-like function. The addition of R120G alphaB-crystallin to unfolding alpha-lactalbumin enhanced the kinetics and extent of its aggregation. R120G alphaB-crystallin became entangled with unfolding alpha-lactalbumin and was a major portion of the resulting insoluble pellet. Similarly, incubation of R120G alphaB-crystallin with alcohol dehydrogenase and insulin also resulted in the presence of R120G alphaB-crystallin in the insoluble pellets. Far and near UV CD indicate that R120G alphaB-crystallin has decreased beta-sheet secondary structure and an altered aromatic residue environment compared with wild-type alphaB-crystallin. The apparent molecular mass of R120G alphaB-crystallin, as determined by gel filtration chromatography, is 1.4 MDa, which is more than twice the molecular mass of wild-type alphaB-crystallin (650 kDa). Images obtained from cryoelectron microscopy indicate that R120G alphaB-crystallin possesses an irregular quaternary structure with an absence of a clear central cavity. The results of this study show, through biochemical analysis, that an altered structure and defective chaperone-like function of alphaB-crystallin are associated with a point mutation that leads to a desmin-related myopathy and cataracts.
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Cristalinas/química , Cristalinas/genética , Desmina/genética , Enfermedades Musculares/genética , Mutación Missense , Alcohol Deshidrogenasa/metabolismo , Sustitución de Aminoácidos , Dicroismo Circular , Microscopía por Crioelectrón , Cristalinas/metabolismo , Cristalinas/ultraestructura , Humanos , Sustancias Macromoleculares , Chaperonas Moleculares/química , Chaperonas Moleculares/metabolismo , Chaperonas Moleculares/ultraestructura , Conformación Proteica , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismo , Proteínas Recombinantes/ultraestructuraRESUMEN
alpha-Crystallin is a major lens protein, comprising up to 40% of total lens proteins, where its structural function is to assist in maintaining the proper refractive index in the lens. In addition to its structural role, it has been shown to function in a chaperone-like manner. The chaperone-like function of alpha-crystallin will help prevent the formation of large light-scattering aggregates and possibly cataract. In the lens, alpha-crystallin is a polydisperse molecule consisting of a 3:1 ratio of alpha A to alpha B subunits. In this study, we expressed recombinant alpha A- and alpha B-crystallin in E. coli and compared the polydispersity, structure and aggregation state between each other and native bovine lens alpha-crystallin. Using gel permeation chromatography to assay for polydispersity, we found native alpha-crystallin to be significantly more polydisperse than either recombinant alpha A- or alpha B-crystallin, with alpha B-crystallin having the most homogeneous structure of the three. Reconstructed images of alpha B-crystallin obtained with cryo-electron microscopy support the concept that alpha B-crystallin is an extremely dynamic molecule and demonstrated that it has a hollow interior. Interestingly, we present evidence that native alpha-crystallin is significantly more thermally stable than either alpha A- or alpha B-crystallin alone. In fact, our experiments suggest that a 3:1 ratio of alpha A to alpha B subunit composition in an alpha-crystallin molecule is optimal in terms of thermal stability. This fascinating result explains the stoichiometric ratios of alpha A- and alpha B-crystallin subunits in the mammalian lens.