RESUMO
It has been generally assumed that insulin circulates freely in blood. However it can also interact with plasma proteins. Insulin receptors are located in the membrane of target cells and consist of an alpha and beta subunits with a tyrosine kinase cytoplasmic domain. The ectodomain, called soluble insulin receptor (SIR) has been found elevated in patients with diabetes mellitus. We explored if insulin binds to SIRs in circulation under physiological conditions and hypothesize that this SIR may be released by hepatocytes in response to high insulin concentrations. The presence of SIR in rat and human plasmas and the culture medium of hepatocytes was explored using Western blot analysis. A purification protocol was performed to isolated SIR using affinity, gel filtration, and ion exchange chromatographies. A modified reverse hemolytic plaque assay was used to measure SIR release from cultured hepatocytes. Incubation with 1 nmol l(-1) insulin induces the release of the insulin receptor ectodomains from normal rat hepatocytes. This effect can be partially prevented by blocking protease activity. Furthermore, plasma levels of SIR were higher in a model of metabolic syndrome, where rats are hyperinsulinemic. We also found increased SIR levels in hyperinsulinemic humans. SIR may be an important regulator of the amount of free insulin in circulation. In hyperinsulinemia, the amount of this soluble receptor increases and this could lead to higher amounts of insulin bound to this receptor, rather than free insulin, which is the biologically active form of the hormone. This observation could enlighten the mechanisms of insulin resistance.
RESUMO
Endogenous glycosylated Hev b 2 (endo-ß-1,3-glucanase) from Hevea brasiliensis is an important latex allergen that is recognized by IgE antibodies from patients who suffer from latex allergy. The carbohydrate moieties of Hev b 2 constitute a potentially important IgE-binding epitope that could be responsible for its cross-reactivity. Here, the structure of the endogenous isoform II of Hev b 2 that exhibits three post-translational modifications, including an N-terminal pyroglutamate and two glycosylation sites at Asn27 and at Asn314, is reported from two crystal polymorphs. These modifications form a patch on the surface of the molecule that is proposed to be one of the binding sites for IgE. A structure is also proposed for the most important N-glycan present in this protein as determined by digestion with specific enzymes. To analyze the role of the carbohydrate moieties in IgE antibody binding and in human basophil activation, the glycoallergen was enzymatically deglycosylated and evaluated. Time-lapse automated video microscopy of basophils stimulated with glycosylated Hev b 2 revealed basophil activation and degranulation. Immunological studies suggested that carbohydrates on Hev b 2 represent an allergenic IgE epitope. In addition, a dimer was found in each asymmetric unit that may reflect a regulatory mechanism of this plant defence protein.
Assuntos
Antígenos de Plantas/química , Basófilos/efeitos dos fármacos , Celulase/química , Hevea/química , Imunoglobulina E/química , Proteínas de Plantas/química , Sequência de Aminoácidos , Antígenos de Plantas/imunologia , Antígenos de Plantas/isolamento & purificação , Antígenos de Plantas/farmacologia , Teste de Degranulação de Basófilos , Basófilos/citologia , Basófilos/imunologia , Sítios de Ligação , Sequência de Carboidratos , Células Cultivadas , Celulase/imunologia , Celulase/isolamento & purificação , Celulase/farmacologia , Cristalografia por Raios X , Ácido Glutâmico/metabolismo , Glicosilação , Humanos , Imunoglobulina E/imunologia , Hipersensibilidade ao Látex/imunologia , Modelos Moleculares , Dados de Sequência Molecular , Proteínas de Plantas/imunologia , Proteínas de Plantas/isolamento & purificação , Proteínas de Plantas/farmacologia , Ligação Proteica , Processamento de Proteína Pós-Traducional , Estrutura Quaternária de Proteína , Imagem com Lapso de TempoRESUMO
Scorpions, mainly those belonging to the genus Tityus cause many deaths and injuries in Brazil, with tens of thousands of envenomations notified every year. However, injuries involving other scorpion species are scarcely registered. Among the sixteen species of the genus Rhopalurus, Thorell, 1876, described up to date, nine are found in this country, with only a confirmed case of human envenomation provoked by R. agamemnonKoch, 1839. The present case reports, for the first time, a case of scorpion sting in a human victim involving Rhopalurus amazonicus, endemic species of the west region of the Pará state, Amazon, Brazil. The symptoms of envenomation were local pain and paresthesia. This study contributes to develop the knowledge on venomous scorpions, particularly those that may cause envenomations in this region.
Assuntos
Masculino , Humanos , Animais , Mordeduras e Picadas/complicações , Parestesia , Picadas de Escorpião/complicações , Venenos de Escorpião/intoxicação , Ecossistema AmazônicoRESUMO
Scorpions, mainly those belonging to the genus Tityus cause many deaths and injuries in Brazil, with tens of thousands of envenomations notified every year. However, injuries involving other scorpion species are scarcely registered. Among the sixteen species of the genus Rhopalurus, Thorell, 1876, described up to date, nine are found in this country, with only a confirmed case of human envenomation provoked by R. agamemnonKoch, 1839. The present case reports, for the first time, a case of scorpion sting in a human victim involving Rhopalurus amazonicus, endemic species of the west region of the Pará state, Amazon, Brazil. The symptoms of envenomation were local pain and paresthesia. This study contributes to develop the knowledge on venomous scorpions, particularly those that may cause envenomations in this region.(AU)
Assuntos
Animais , Intoxicação/diagnóstico , Escorpiões , Picadas de Escorpião , Ecossistema AmazônicoRESUMO
Scorpions, mainly those belonging to the genus Tityus cause many deaths and injuries in Brazil, with tens of thousands of envenomations notified every year. However, injuries involving other scorpion species are scarcely registered. Among the sixteen species of the genus Rhopalurus, Thorell, 1876, described up to date, nine are found in this country, with only a confirmed case of human envenomation provoked by R. agamemnon Koch, 1839. The present case reports, for the first time, a case of scorpion sting in a human victim involving Rhopalurus amazonicus, endemic species of the west region of the Pará state, Amazon, Brazil. The symptoms of envenomation were local pain and paresthesia. This study contributes to develop the knowledge on venomous scorpions, particularly those that may cause envenomations in this region.
RESUMO
Scorpions, mainly those belonging to the genus Tityus cause many deaths and injuries in Brazil, with tens of thousands of envenomations notified every year. However, injuries involving other scorpion species are scarcely registered. Among the sixteen species of the genus Rhopalurus, Thorell, 1876, described up to date, nine are found in this country, with only a confirmed case of human envenomation provoked by R. agamemnonKoch, 1839. The present case reports, for the first time, a case of scorpion sting in a human victim involving Rhopalurus amazonicus, endemic species of the west region of the Pará state, Amazon, Brazil. The symptoms of envenomation were local pain and paresthesia. This study contributes to develop the knowledge on venomous scorpions, particularly those that may cause envenomations in this region.(AU)
Assuntos
Humanos , Animais , Masculino , Mordeduras e Picadas/complicações , Venenos de Escorpião/intoxicação , Picadas de Escorpião/complicações , Parestesia , Ecossistema AmazônicoRESUMO
Sea anemone toxins are predominantly peptide and proteins that act mainly on sodium and potassium channels, as well as in a variety of target cells causing lysis. Over recent years, the number of sea anemone peptide toxins as well as cytolytic pore-forming proteins and phospholipase A(2) sequences submitted to databases has been rapidly increasing due to the developments in DNA sequencing technology and proteomic approaches. However, the lack of a systematic nomenclature has resulted in multiple names being assigned to the same toxins, toxins from unrelated species being designated by the same name, and ambiguous name designations. Therefore, in this work we propose a systematic nomenclature in which we adopted specific criteria, based on order of discovery and phylogenetic analysis, in order to avoid redundant sea anemone toxin names. Implementation of the nomenclature proposed here not only allowed us to rename the already published 191 anemone toxins without ambiguities, but it can be used to unambiguously name newly discovered toxins whether or not they are related to previously published sea anemone sequences. In the new nomenclature each toxin name contains information about the toxin's biological activity, origin and relationship to known isoforms. Ongoing increases in the speed of DNA sequencing will raise significantly the number of sea anemone toxin sequences in the literature. This will represent a constant challenge in their clear identification and logical classification, which could be solved using the proposed nomenclature.
Assuntos
Venenos de Cnidários/química , Peptídeos/química , Proteínas/química , Anêmonas-do-Mar/metabolismo , Terminologia como Assunto , Animais , Venenos de Cnidários/classificação , Bases de Dados de Ácidos Nucleicos , Peptídeos/classificação , Filogenia , Proteínas/classificação , Anêmonas-do-Mar/genética , Análise de Sequência de DNARESUMO
Systemic amyloid light-chain (LC) amyloidosis is a disease process characterized by the pathological deposition of monoclonal LCs in tissue. All LC subtypes are capable of fibril formation although lambda chains, particularly those belonging to the lambda6 type, are overrepresented. Here, we report the thermodynamic and in vitro fibrillogenic properties of several mutants of the lambda6 protein 6aJL2 in which Pro7 and/or His8 was substituted by Ser or Pro. The H8P and H8S mutants were almost as stable as the wild-type protein and were poorly fibrillogenic. In contrast, the P7S mutation decreased the thermodynamic stability of 6aJL2 and greatly enhanced its capacity to form amyloid-like fibrils in vitro. The crystal structure of the P7S mutant showed that the substitution induced both local and long-distance effects, such as the rearrangement of the V(L) (variable region of the light chain)-V(L) interface. This mutant crystallized in two orthorhombic polymorphs, P2(1)2(1)2(1) and C222(1). In the latter, a monomer that was not arranged in the typical Bence-Jones dimer was observed for the first time. Crystal-packing analysis of the C222(1) lattice showed the establishment of intermolecular beta-beta interactions that involved the N-terminus and beta-strand B and that these could be relevant in the mechanism of LC fibril formation. Our results strongly suggest that Pro7 is a key residue in the conformation of the N-terminal sheet switch motif and, through long-distance interactions, is also critically involved in the contacts that stabilized the V(L) interface in lambda6 LCs.