Protein kinases (PKs) of parasitic protozoa are being evaluated as drug targets. A large number of protein kinases within the protein kinome of Entamoeba histolytica strongly suggest that protein phosphorylation is a key component of pathogenesis regulation by this parasite. PI3 K and Src are kinases previously described in this parasite, but their role is poorly understood. Here, the effect of Src-1-inhibitor and PI3 K inhibitor (Wortmannin) on the virulence factors of E. histolytica was evaluated. Results show that both inhibitors affect the actin cytoskeleton and the amoebic movement. Also, the proteolytic activity is diminished by Wortmannin, but not by Src-inhibitor-1; however, the phagocytic capacity is diminished by Wortmannin and Src-1-inhibitor. Finally, we found that the virulence in vivo of E. histolytica is affected by Wortmannin but not by Src-1-inhibitor. This study opens the way for the design of anti-amoebic drugs based on kinase inhibition.

Viruses replicate inside host cells, where they use host biochemical and structural components to facilitate the production of new virus particles. As a consequence of co-evolution with their hosts, viruses have acquired host genes and genetic mutations that confer dominance over normal cell function. Research on virus–cell interactions has focused on the identification of mechanisms of virus dominance in order to develop therapeutic strategies for preventing productive infection. Although such research remains an essential part of molecular virology, viruses are also important genetic tools that can be used to analyse cell function. Because virus genomes contain genetic information, some of which was derived from host cells, it is possible that the analyses of virus–host interactions might lead to the identification of functionally dominant virus genes and novel eukaryotic counterparts. In this article, we have described how transforming and non-transforming viruses can control cell motility (cell migration or membrane projection), and explained how the analysis of virus cytopathic effects (CPEs) led to the identification of a novel family of cellular genes that regulate diverse aspects of cell motility.

Growth and development of adult schistosomes requires permanent communication processes of the parasites with their specific host environment and, additionally, between the two genders. Accumulating evidence suggests that, at the molecular level, the mandatory interactions are mediated by signal transduction processes. During recent years, a considerable interest has emerged in the identification of signalling molecules from this parasite and to elucidate their roles during development. In this organism, a number of different molecules have been identified which belong to diverse classes of evolutionary conserved signal transduction cascades. However, up to now no representative of the conserved family of cellular tyrosine kinases has been identified. In this study we present a suitable approach to identify this class of molecules and demonstrate the successful cloning and molecular characterization of one of the isolated genes, the tyrosine kinase 5 (TK5). An unexpected finding was that in the Liberian strain of Schistosoma mansoni the TK5 gene exhibits an allelic polymorphism.