Project description:For malaria transmission, the parasite must undergo sexual differentiation into mature gametocytes. However, the molecular basis for this critical transition in the parasites life cycle is unknown. Six previously uncharacterized genes, Pfg14.744, Pfg14.745, Pfg14.748, Pfg14.763, Pfg14.752 and Pfg6.6 that are members of a 36 gene Plasmodium falciparum-specific subtelomeric superfamily were found to be expressed in parasites that are committed to sexual development as suggested by co-expression of Pfs16 and Pfg27. Northern blots demonstrated that Pfg14.744 and Pfg14.748 were first expressed before the parasites differentiated into morphologically distinct gametocytes, transcription continued to increase until stage II gametocytes were formed and then rapidly decreased. Immunofluorescence assays indicated that both proteins were only produced in the subpopulation of ring stage parasites that are committed to gametocytogenesis and both localized to the parasitophorous vacuole (PV)b of the early ring stage parasites. As the parasites continued to develop Pfg14.748 remained within the parasitophorous vacuole, while Pfg14.744 was detected in the erythrocyte. The 5' flanking region of either gene alone was sufficient to drive early gametocyte specific expression of green fluorescent protein (GFP). In parasites transfected with a plasmid containing the Pfg14.748 5' flanking region immediately upstream of GFP, fluorescence was observed in a small number of schizonts the cycle before stage I gametocytes were observed. This expression pattern is consistent with commitment to sexual differentiation prior to merozoite release and erythrocyte invasion. Further investigation into the role of these genes in the transition from asexual to sexual differentiation could provide new strategies to block malaria transmission. Microarray analysis was used to compare two clones derived from Plasmodium falciparum strain 3D7 parasites that differ in their ability to undergo gametocytogenesis. Clone G+ produces gametocytes and clone G- produces very few if any gametocytes. RNA was harvested from the cultures when the asexual parasitemia was 0.9-1.48% (day 4) (n=4) after setting up the gametocyte cultures and 5.2-5.58% (day 6) (n=4) prior to the appearance of morphologically distinct gametocytes and used to generate cDNA that was labeled with Cy3 or Cy5 and hybridized to the Plasmodium falciparum 70 mer oligonucleotide microarray developed by DeRisi and co-workers.
Project description:The inner membrane complex (IMC), a double-membrane organelle underneath the plasma membrane in apicomplexan parasites, plays a significant role in motility and invasion and confers shape to the cell. We characterized the function of PbIMC1g, a component of the IMC1 family member in Plasmodium berghei. PbIMC1g is recruited to the IMC in late schizonts, activated gametocytes, and ookinetes. Pairwise yeast two-hybrid assays demonstrate that PbIMC1g interacts with IMC1c, a component of the PHIL1 complex, and the core sub-repeat motif ‘EKI(V)V(I)EVP’ in PbIMC1g is essential for this interaction. Localization of PbIMC1g to the IMC was dependent on its IMCp domain, while its C-terminus and palmitoylation sites were required for the full efficiency of proper IMC targeting. PbIMC1g is required for asexual stage development, and its conditional knockdown resulted in a defect in schizogony. Additionally, PbIMC1g was also important for male gametogenesis and ookinete development. As an IMC component that assists in anchoring the glideosome to the subpellicular network, PbIMC1g was also involved in ookinete motility and mosquito midgut invasion. IMC1g from the human parasite P. Plasmodium vivax could functionally replace PbIMC1g in P. berghei, confirming the evolutionary conservation of IMC1g proteins in Plasmodium spp. Together, this work reveals an essential role of IMC1g in the parasite life cycle and suggests that IMC1 family members likely contribute to parasite gliding and invasion.
Project description:Malaria parasites require multiple phosphorylation and dephosphorylation steps to drive signaling pathways for proper differentiation and transformation. Several protein phosphatases, including Protein Phosphatase 1 (PP1c), one of the main dephosphorylation enzymes, have been shown to be indispensable for Plasmodium life cycle. PP1c functions are elaborated processes via dynamic interactions with a vast number of binding partners that contribute to its diversity of action. In this study, we have used Plasmodium berghei transgenic parasite strains stably expressing PP1c or its Inhibitor 2 (I2) tagged with mCherry, combined with mCherry affinity pulldown of proteins from asexual and sexual stages and mass spectrometry analyses. Mapped proteins were used to identify interactomes and to cluster functionally related proteins. Our findings confirm previous physical interactions of PP1c and reveal shared and specific biological processes enrichment linked to cellular component assembly in both schizonts and gametocytes, to biosynthetic process/translation in schizonts and to protein transport exclusively in gametocytes. Further, our analysis of PP1c and I2 interactomes reveals that nuclear export mediator factor and peptidyl-prolyl cis-trans isomerase, suggested to be essential in P. falciparum, could be potential targets of the complex PP1c/I2 in both asexual and sexual stages. Our study emphasizes the adaptability of Plasmodium PP1c and provides a fundamental study of the protein interaction landscapes involved in a myriad of events in Plasmodium, suggesting why it is crucial to the parasite and a source for alternative therapeutic strategies.
Project description:For malaria transmission, the parasite must undergo sexual differentiation into mature gametocytes. However, the molecular basis for this critical transition in the parasites life cycle is unknown. Six previously uncharacterized genes, Pfg14.744, Pfg14.745, Pfg14.748, Pfg14.763, Pfg14.752 and Pfg6.6 that are members of a 36 gene Plasmodium falciparum-specific subtelomeric superfamily were found to be expressed in parasites that are committed to sexual development as suggested by co-expression of Pfs16 and Pfg27. Northern blots demonstrated that Pfg14.744 and Pfg14.748 were first expressed before the parasites differentiated into morphologically distinct gametocytes, transcription continued to increase until stage II gametocytes were formed and then rapidly decreased. Immunofluorescence assays indicated that both proteins were only produced in the subpopulation of ring stage parasites that are committed to gametocytogenesis and both localized to the parasitophorous vacuole (PV)b of the early ring stage parasites. As the parasites continued to develop Pfg14.748 remained within the parasitophorous vacuole, while Pfg14.744 was detected in the erythrocyte. The 5' flanking region of either gene alone was sufficient to drive early gametocyte specific expression of green fluorescent protein (GFP). In parasites transfected with a plasmid containing the Pfg14.748 5' flanking region immediately upstream of GFP, fluorescence was observed in a small number of schizonts the cycle before stage I gametocytes were observed. This expression pattern is consistent with commitment to sexual differentiation prior to merozoite release and erythrocyte invasion. Further investigation into the role of these genes in the transition from asexual to sexual differentiation could provide new strategies to block malaria transmission.
Project description:Differentiation from asexual blood stages to sexual gametocytes is required for transmission of malaria parasites from the human to the mosquito host. Preventing gametocyte commitment and development would block parasite transmission, but the underlying molecular mechanisms behind these processes remain poorly understood. Here, we report that the ApiAP2 transcription factor, PfAP2-G2 (PF3D7_1408200) plays a critical role in the maturation of Plasmodium falciparum gametocytes. PfAP2-G2 binds to the promoters of a wide array of genes that are expressed at many stages of the parasite life cycle. Interestingly, we also find binding of PfAP2-G2 within the gene body of almost 3000 genes, which strongly correlates with the location of H3K36me3 and several other histone modifications as well as Heterochromatin Protein 1 (HP1), suggesting that occupancy of PfAP2-G2 in gene bodies may serve as an alternative regulatory mechanism. Disruption of pfap2-g2 does not impact asexual development, parasite multiplication rate, or commitment to sexual development but the majority of sexual parasites are unable to mature beyond stage III gametocytes. The absence of pfap2-g2 leads to overexpression of 28% of the genes bound by PfAP2-G2 and none of the PfAP2-g2 bound are downregulated, suggesting that it is a repressor. We also find that PfAP2-G2 interacts with chromatin remodeling proteins, a microrchidia (MORC) protein, and another ApiAP2 protein (PF3D7_1139300). Overall our data demonstrate that PfAP2-G2 is an important transcription factor that establishes an essential gametocyte maturation program in association with other chromatin-related proteins.
Project description:Plasmodium falciparum asexual parasites and late gametocytes were treated for 24 or 48 h with MMV390048 or MMV642943 in order to understand the functional consequences of inhibiting lipid kinases
Project description:Serine/arginine-rich protein kinases (SRPK) are cell cycle-regulated serine/threonine protein kinases and are important regulators of splicing factors. In this study, we functionally characterize SRPK1 of the human malaria parasite Plasmodium falciparum (Pf). PfSRPK1 was expressed in asexual blood stages and sexual stage gametocytes. Pfsrpk1¯ parasites formed asexual schizonts that generated far fewer merozoites when compared to wildtype parasites, causing reduced replication rates. Pfsrpk1¯parasites also showed a severe defect in the differentiation of male gametes, causing a complete block in parasite transmission to mosquitoes. RNA-seq analysis of wildtype PfNF54 and Pfsrpk1¯ stage V gametocytes suggested a role for PfSRPK1 in regulating transcript splicing and transcript abundance of genes coding for (i) microtubule/cilium morphogenesis related proteins, (ii) proteins involved in cyclic nucleotide metabolic processes, (iii) proteins involved in signaling such as PfMAP2, (iv) lipid metabolism enzymes, (v) proteins of the osmophilic bodies and (vi) crystalloid components. Our study reveals an essential role for PfSRPK1 in parasite cell morphogenesis and suggests this kinase as a target to prevent malaria transmission from man to mosquito.
Project description:Epigenome profiling has led to the paradigm that promoters of active genes are decorated with H3K4me3 and H3K9ac marks. Data revealed an extensively euchromatic epigenome with heterochromatin restricted to variant surface antigen gene families (VSA) and a number of genes hitherto unlinked to VSA. The vast majority of the genome shows an unexpected pattern of enrichment of H3K4me3 and H3K9ac at intergenic regions and depletion at genes. Chip-chip (and cDNA) from Plasmodium falciparum strain NF54 asexual blood stages with H3, H3K4me3, H3K9me3 and H3K9ac
Project description:The description of the transcriptome and proteome datasets of Plasmodium falciparum, the deadliest strain of human malaria, has been a tremendous resource for the understanding of the molecular physiology of this parasite. However, the underlying translational control that links global measurements of steady-state mRNA with protein levels is not well understood. Our work bridges this disconnect by measuring translation on a whole genome scale using ribosome profiling, providing the first measurements of new protein synthesis through the asexual blood phase developmental cycle.