Assuntos
Comportamento Animal/fisiologia , Doenças Parasitárias em Animais/imunologia , Doenças Parasitárias em Animais/parasitologia , Fenótipo , Adaptação Fisiológica/imunologia , Animais , Controle Comportamental , Ecossistema , Interações Hospedeiro-Parasita/imunologia , Parasitos/fisiologia , Papel do DoenteRESUMO
Analysis of the Schistosoma mansoni peptidome for immunomodulatory molecules by solvent extraction and reverse-phase HPLC revealed a 27-amino-acid residue peptide from an extract of cercariae. Using matrix-assisted, laser desorption-ionization, time-of-flight mass spectrometry, the peptide yielded a protonated molecular ion [M + H]+ of m/z 2789. The unequivocal sequence was deduced by automated Edman degradation as: DLWNSIKDMAAAAGRAALNAVTGMVNQ. The peptide exhibited an 80.76% identity with dermaseptin 3.1 from the leaf frog Agalychnis annae, and was therefore named Schistosoma mansoni dermaseptin-like peptide (SmDLP). Immunocytochemical staining using a primary antidermaseptin B2 antibody located SmDLP in acetabular glands of cercariae, in and around schistosomula, and in adult worms and their eggs. Dot-blotting confirmed its presence in extracts (cercariae and worms) and excretion/secretion (E/S) products (transforming cercariae and eggs). This was corroborated by use of a MALDI-ToF spectra database of E/S products from cercariae. Functional characterization of the peptide indicated that SmDLP had typical amphipathic antimicrobial peptide properties, i.e., the ability to lyse human erythrocytes causing a decrease in the levels of nitric oxide produced by monocytic cells. This last function strongly suggests that SmDLP plays a vital role in the parasite's immunoevasion strategy. The possibility that schistosomes acquired this gene from amphibians has been discussed by constructing a phylogenetic tree.
Assuntos
Proteínas de Anfíbios/química , Peptídeos Catiônicos Antimicrobianos/química , Proteínas de Helminto/química , Schistosoma mansoni/química , Sequência de Aminoácidos , Proteínas de Anfíbios/isolamento & purificação , Proteínas de Anfíbios/fisiologia , Animais , Peptídeos Catiônicos Antimicrobianos/isolamento & purificação , Peptídeos Catiônicos Antimicrobianos/fisiologia , Biomphalaria , Cromatografia Líquida de Alta Pressão , Sequência Consenso , Sequência Conservada , Proteínas de Helminto/fisiologia , Hemólise , Interações Hidrofóbicas e Hidrofílicas , Immunoblotting , Imuno-Histoquímica , Masculino , Camundongos , Dados de Sequência Molecular , Estrutura Secundária de Proteína , Schistosoma mansoni/imunologia , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz , Relação Estrutura-AtividadeRESUMO
Snails are intermediate hosts to schistosome parasites, some of which are the main cause of human schistosomiasis (bilharzia), and have been used as models for parasite-host interactions for a long time. Here, we have characterized a novel internal defense peptide of the snail Lymnaea stagnalis, of which the relative abundance in brain tissue increases upon infection with the avian schistosome Trichobilharzia ocellata. This protein, named granularin, is secreted by granular cells, which are numerous in the connective tissue surrounding the brain. The protein is unique because it comprises only a single Von Willebrand factor type C domain that is normally found in large transmembrane and secreted extracellular matrix proteins. The granularin gene is twice up-regulated during parasitation. Purified granularin stimulates phagocytosis of foreign particles by blood hemocytes. Together, our data indicate that granularin represents a novel protein that acts as an opsonin in the molluscan internal defense response.
