RESUMO
Congenital Toxoplasma gondii infection can result in intracranial calcification, hydrocephalus and retinochoroiditis. Acquired infection is commonly associated with ocular disease. Pathology is characterized by strong proinflammatory responses. Ligation of ATP by purinergic receptor P2X(7), encoded by P2RX7, stimulates proinflammatory cytokines and can lead directly to killing of intracellular pathogens. To determine whether P2X(7) has a role in susceptibility to congenital toxoplasmosis, we examined polymorphisms at P2RX7 in 149 child/parent trios from North America. We found association (FBAT Z-scores +/-2.429; P=0.015) between the derived C(+)G(-) allele (f=0.68; OR=2.06; 95% CI: 1.14-3.75) at single-nucleotide polymorphism (SNP) rs1718119 (1068T>C; Thr-348-Ala), and a second synonymous variant rs1621388 in linkage disequilibrium with it, and clinical signs of disease per se. Analysis of clinical subgroups showed no association with hydrocephalus, with effect sizes for associations with retinal disease and brain calcifications enhanced (OR=3.0-4.25; 0.004Assuntos
Coriorretinite/genética
, Predisposição Genética para Doença/genética
, Receptores Purinérgicos P2/genética
, Toxoplasmose Congênita/genética
, Adulto
, Brasil
, Pré-Escolar
, Coriorretinite/etiologia
, Feminino
, Estudo de Associação Genômica Ampla
, Haplótipos/genética
, Humanos
, Padrões de Herança/genética
, Desequilíbrio de Ligação
, Modelos Logísticos
, Masculino
, América do Norte
, Polimorfismo de Nucleotídeo Único/genética
, Receptores Purinérgicos P2X7
, Toxoplasmose Congênita/complicações
RESUMO
The shikimate pathway is essential for survival of the apicomplexan parasites Plasmodium falciparum, Toxoplasma gondii and Cryptosporidium parvum. As it is absent in mammals it is a promising therapeutic target. Herein, we describe the genes encoding the shikimate pathway enzymes in T. gondii. The molecular arrangement and phylogeny of the proteins suggests homology with the eukaryotic fungal enzymes, including a pentafunctional AROM. Current rooting of the eukaryotic evolutionary tree infers that the fungi and apicomplexan lineages diverged deeply, suggesting that the arom is an ancient supergene present in early eukaryotes and subsequently lost or replaced in a number of lineages.
Assuntos
Células Eucarióticas/enzimologia , Evolução Molecular , Genes de Protozoários , Transdução de Sinais/genética , Toxoplasma/genética , Oxirredutases do Álcool/genética , Animais , Sequência de Bases , Dados de Sequência Molecular , Fosfotransferases (Aceptor do Grupo Álcool)/genética , FilogeniaRESUMO
Fab I, enoyl acyl carrier protein reductase (ENR), is an enzyme used in fatty acid synthesis. It is a single chain polypeptide in plants, bacteria, and mycobacteria, but is part of a complex polypeptide in animals and fungi. Certain other enzymes in fatty acid synthesis in apicomplexan parasites appear to have multiple forms, homologous to either a plastid, plant-like single chain enzyme or more like the animal complex polypeptide chain. We identified a plant-like Fab I in Plasmodium falciparum and modelled the structure on the Brassica napus and Escherichia coli structures, alone and complexed to triclosan (5-chloro-2-[2,4 dichlorophenoxy] phenol]), which confirmed all the requisite features of an ENR and its interactions with triclosan. Like the remarkable effect of triclosan on a wide variety of bacteria, this compound markedly inhibits growth and survival of the apicomplexan parasites P. falciparum and Toxoplasma gondii at low (i.e. IC50 congruent with150-2000 and 62 ng/ml, respectively) concentrations. Discovery and characterisation of an apicomplexan Fab I and discovery of triclosan as lead compound provide means to rationally design novel inhibitory compounds.