Search

Abstract: Plasmodium falciparum Tudor Staphylococcal Nuclease (PfTSN) has a multidomain organization and preferentially cleaves single stranded RNAs. PfTSN is quite distinct from its vertebrate homologues both in terms of its primary sequence and functional activity. Here, we analyzed the effect of PfTSN specific siRNA on parasite growth and development. Treatment of parasite culture with PfTSN siRNA at the late ring stage resulted in substantial inhibition in parasite growth. The PfTSN siRNA treated parasite cultures showed significant reduction in specific mRNA and PfTSN expression. Morphological examination of PfTSN siRNA treated parasites showed block in the development of parasite at the trophozoite stage. Treatment of parasites with a specific inhibitor of micrococcal nucleases, 3′,5′-deoxythymidine biphosphate (pdTp) resulted in similar block in parasite development, thereby suggesting that PfTSN plays an important role at the trophozoite stage of the parasite. Collectively, our findings point towards an essential role for the PfTSN in the parasite’s infection cycle. [Copyright &y& Elsevier]

Abstract: The process of merozoite release in Plasmodium falciparum involves rupture of the parasitophorous vacuole membrane and erythrocyte plasma membrane. Through the use of protease inhibitors that halt the merozoite release, a number of parasite proteases, especially serine, aspartic, and cysteine proteases, have been implicated in the schizont rupture. To understand the precise role of cysteine proteases in the merozoite release, in the present study, we treated P. falciparum cultures with siRNAs corresponding to falcipain-1, falcipain-2, and falcipain-3, the three papain-family proteases of the parasite. Treatment of malaria parasites with either of the falcipain siRNAs considerably reduced parasite growth. Morphological examination of the siRNA treated parasite cultures revealed that most of the parasites in falcipain-2 siRNA treated cultures were arrested at schizont stage. Analysis of a transgenic P. falciparum line expressing chimeric-GFP upon treatment with falcipain-2 siRNA revealed block in the rupture of erythrocyte membrane at the time of merozoite egression. These results suggest that falcipain-2 is an important parasitic protease that participates in hemoglobin degradation and in the merozoite release. [Copyright &y& Elsevier]