RESUMO
Plasmodium the causative agent of malaria is a member of the phylum Apicomplexa, where all invasive forms have a substrate-dependent motility called gliding, key to malaria transmission. Gliding allows parasite host-cell recognition, binding, cell entry and trespassing the cytoplasm. In this process Plasmodium releases molecules from micronemes and the cell surface that are deposited on trails left behind on the substratum as the parasite progresses. Previously we identified the heat shock protein 70-1 (HSP 70-1) on the surface and micronemes of P. berghei ookinetes, the parasite form that invades the mosquito midgut. To investigate if this protein is shed of from the parasite during invasion, we searched HSP 70-1 in gliding trails deposited on a solid surface by P. berghei ookinetes.
Assuntos
Culicidae , Malária , Animais , Culicidae/metabolismo , Proteínas de Choque Térmico HSP70/genética , Malária/parasitologia , Plasmodium berghei/genética , Plasmodium berghei/metabolismo , Proteínas de Protozoários/genética , Proteínas de Protozoários/metabolismoRESUMO
The description of Plasmodium ookinete surface proteins and their participation in the complex process of mosquito midgut invasion is still incomplete. In this study, using phage display, a consensus peptide sequence (PWWP) was identified in phages that bound to the Plasmodium berghei ookinete surface and, in selected phages, bound to actin and enolase in overlay assays with ookinete protein extracts. Actin was localized on the surface of fresh live ookinetes by immunofluorescence and electron microscopy using specific antibodies. The overall results indicated that enolase and actin can be located on the surface of ookinetes, and suggest that they could participate in Plasmodium invasion of the mosquito midgut.
Assuntos
Actinas/metabolismo , Aedes/metabolismo , Anopheles/metabolismo , Sistema Digestório/metabolismo , Estágios do Ciclo de Vida/genética , Peptídeos/metabolismo , Fosfopiruvato Hidratase/metabolismo , Plasmodium berghei , Aedes/genética , Aedes/parasitologia , Sequência de Aminoácidos , Animais , Anopheles/genética , Anopheles/parasitologia , Extratos Celulares , Células Cultivadas , Sequência Conservada , Sistema Digestório/parasitologia , Imunofluorescência , Malária/metabolismo , Malária/parasitologia , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Microscopia Eletrônica , Dados de Sequência Molecular , Biblioteca de Peptídeos , Peptídeos/química , Peptídeos/genética , Plasmodium berghei/genética , Plasmodium berghei/metabolismo , Proteínas de Protozoários/metabolismo , Doenças dos Roedores/metabolismo , Doenças dos Roedores/parasitologiaRESUMO
The acrosome reaction (AR) is a regulated exocytotic process. In several cell types, an actin network situated under the plasma membrane (PM) acts as a physical barrier to prevent this exocytosis. In seeking a function for a cortical skeleton in guinea pig spermatozoa, the PM and the outer acrosomal membrane (OAM) were investigated for the presence of F-actin and spectrin, proteins generally found in cell cortical skeletons. Both membrane types were visualized in whole-mount preparations by electron microscopy. PM proteins gave positive reaction to the Na(+),K(+)-ATPase antibody and the OAM proteins did not react to the antibody. Furthermore, a Triton X-100-resistant skeleton was obtained from both membrane types. Using gold immunoelectron microscopy, F-actin was visualized in the PM and in the OAM skeletons, while spectrin was only detected in the PM skeleton. The presence of an F-actin cortical skeleton in the sperm PM suggests that F-actin may be involved in the AR. The significantly higher number of AR elicited by cytochalasin D (Cyt-D) treatment(P<0.005) and data showing a significant (P>0.03) decrease in F-actin relative concentration in capacitating spermatozoa, agree with this suggestion. Furthermore, the proposal is strengthened by the fact that stabilization of F-actin by phalloidin (Ph) significantly (P>0.01) diminished AR induced by Ca(2+) in a streptolysin O (SLO)-permeabilized sperm model.
