RESUMEN
Circulating IgM present in the body prior to any apparent Ag exposure is referred to as natural IgM. Natural IgM provides protective immunity against a variety of pathogens. Salmonella enterica serovar Typhi (S. Typhi) is the causative agent of typhoid fever in humans. Because mice are not permissive to S. Typhi infection, we employed a murine model of typhoid using S. enterica serovar Typhimurium expressing the Vi polysaccharide (ViPS) of S. Typhi (S. Typhimurium strain RC60) to evaluate the role of natural IgM in pathogenesis. We found that natural mouse IgM binds to S. Typhi and S. Typhimurium. The severity of S. Typhimurium infection in mice is dependent on presence of the natural resistance-associated macrophage protein 1 (Nramp1) allele; therefore, we infected mice deficient in secreted form of IgM (sIgM) on either a Nramp1-resistant (129S) or -susceptible (C57BL/6J) background. We found that the lack of natural IgM results in a significantly increased susceptibility and an exaggerated liver pathology regardless of the route of infection or the Nramp1 allele. Reconstitution of sIgM-/- mice with normal mouse serum or purified polyclonal IgM restored the resistance to that of sIgM+/+ mice. Furthermore, immunization of sIgM-/- mice with heat-killed S. Typhi induced a significantly reduced anti-ViPS IgG and complement-dependent bactericidal activity against S. Typhi in vitro, compared with that of sIgM+/+ mice. These findings indicate that natural IgM is an important factor in reducing the typhoid severity and inducing an optimal anti-ViPS IgG response to vaccination.
Asunto(s)
Inmunoglobulina G , Inmunoglobulina M , Polisacáridos Bacterianos , Fiebre Tifoidea , Animales , Humanos , Ratones , Modelos Animales de Enfermedad , Inmunoglobulina G/inmunología , Ratones Endogámicos C57BL , Fiebre Tifoidea/inmunología , Susceptibilidad a Enfermedades , Formación de Anticuerpos , Ratones de la Cepa 129 , Polisacáridos Bacterianos/inmunologíaRESUMEN
Low molecular weight protein tyrosine phosphatases (LMW-PTP, EC 3.1.3.48) are a family of single-domain enzymes with molecular weight up to 18 kDa, expressed in different tissues and considered attractive pharmacological targets for cancer chemotherapy. Despite this, few LMW-PTP inhibitors have been described to date, and the structural information on LMW-PTP druggable binding sites is scarce. In this study, a small series of phosphonic acids were designed based on a new crystallographic structure of LMW-PTP complexed with benzylsulfonic acid, determined at 2.1Å. In silico docking was used as a tool to interpret the structural and enzyme kinetics data, as well as to design new analogs. From the synthesized series, two compounds were found to act as competitive inhibitors, with inhibition constants of 0.124 and 0.047 mM. We also report the 2.4Å structure of another complex in which LMW-PTP is bound to benzylphosphonic acid, and a structure of apo LMW-PTP determined at 2.3Å resolution. Although no appreciable conformation changes were observed, in the latter structures, amino acid residues from an expression tag were found bound to a hydrophobic region at the protein surface. This regions is neighbored by positively charged residues, adjacent to the active site pocket, suggesting that this region might be not a mere artefact of crystal contacts but an indication of a possible anchoring region for the natural substrate-which is a phosphorylated protein.
Asunto(s)
Ácidos Fosforosos/química , Proteínas Tirosina Fosfatasas/metabolismo , Proteínas Proto-Oncogénicas/metabolismo , Sitios de Unión , Dominio Catalítico , Cristalografía por Rayos X , Humanos , Cinética , Simulación del Acoplamiento Molecular , Ácidos Fosforosos/metabolismo , Proteínas Tirosina Fosfatasas/química , Proteínas Tirosina Fosfatasas/genética , Proteínas Proto-Oncogénicas/química , Proteínas Proto-Oncogénicas/genética , Proteínas Recombinantes/biosíntesis , Proteínas Recombinantes/química , Proteínas Recombinantes/aislamiento & purificación , Especificidad por Sustrato , Ácidos Sulfónicos/química , Ácidos Sulfónicos/metabolismoRESUMEN
OBJECTIVE: To evaluate the frequency and clinical spectrum of the recently identified p.D620N mutation in the VPS35 gene in Parkinson disease (PD) in an international sample. DESIGN: Genetic analysis by DNA sequencing and detailed clinical and neuropsychiatric assessment as well as neuroimaging in mutation carriers. SETTING: Tertiary referral centers in Germany, Serbia, Chile, and the United States. PATIENTS: One thousand seven hundred seventy-four patients with PD. MAIN OUTCOME MEASURE: Frequency of the p.D620N mutation. RESULTS: A single mutation carrier was identified. The mutation carrier was a 60-year-old German man who had tremor-dominant PD since the age of 45 years. Longitudinal follow-up over 13 years revealed a disease progression from Hoehn and Yahr stage 1 to 3. There was evidence of mild cognitive impairment on the Montreal Cognitive Assessment. No abnormalities were observed by multimodal neuroimaging. He had a family history consistent with autosomal dominant inheritance. An affected paternal aunt and 3 reportedly unaffected siblings were also found to be mutation carriers. CONCLUSION: VPS35 mutations are a rare cause of PD in different populations. The clinical phenotype may be indistinguishable from idiopathic PD with the possible exception of an earlier age at onset. Genetic analysis of the extended family revealed incomplete penetrance of the p.D620N mutation.