The Plasmodium falciparum ApiAP2 transcription factor PfAP2-V controls parasite proliferation and virulence in intra-erythrocytic developmental cycle
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ABSTRACT: Malaria pathogenesis, encompassing parasite invasion, egress, and antigenic variation, relies on the coordinated activity of numerous proteins, yet their molecular regulatory mechanisms remain poorly understood. Here, we define the role of PfAP2-V, a critical AP2 transcription factor in Plasmodium falciparum, during intra-erythrocytic developmental cycle. PfAP2-V displayed two distinct peaks of expression and was critical for parasite proliferation, invasion, and the regulation of virulence-associated genes. Inducible knockdown of PfAP2-V reduced parasitemia by blocking trophozoite development, which was associated with downregulated phosphorylation of virulence-associated proteins. Furthermore, PfAP2-V knockdown reduced PfEMP1 expression, impairing the adhesion of infected red blood cells to endothelial receptors. Genome-wide chromosome conformation capture and chromatin immunoprecipitation sequencing analyses revealed that PfAP2-V knockdown altered chromatin interactions and accessibility, disrupting the regulation of antigenic variant genes. These findings establish PfAP2-V as a key transcriptional regulator at distinct stages of the intra-erythrocytic cycle.
Project description:Transcriptional profiling of transgenic P. falciparum asexual blood stage parasites of the transgenic strain 3D7/DDGFP-PfAP2-HC at five time points during intra-erythrocytic parasite development. The DD (FKBP destabilisation domain) allows for the conditional expression of fusion proteins: DD fusion proteins are rapidly degraded or stably expressed in absence or presence of the stabilising ligand Shield-1, respectively (Banaszynski LA, Chen LC, Maynard-Smith LA, Ooi AG, Wandless TJ. A rapid, reversible, and tunable method to regulate protein function in living cells using synthetic small molecules.Cell. 2006 Sep 8;126(5):995-1004). The goal of this experiment was to identify genes differentially expressed in DDGFP-PfAP2-HC-expressing compared to DDGFP-PfAP2-HC-depleted parasites during the intra-erythtrocytic cell cycle.
Project description:Calcium Dependent Protein Kinases (CDPKs) are key effectors of calcium signaling in malaria parasite. We have elucidated a novel role of PfCDPK1, which is indispensable for the erythrocytic development of Plasmodium falciparum, in invasion of host Red Blood Cells (RBCs). To gain insights into the mechanisms via which PfCDPK1 is involved in parasitic processes, a comparative phosphoproteomic analysis was employed to identify its parasitic targets. Proteins were isolated from CDPK1 knockdown and wild type parasites and processed for trypsin digestion and iTRAQ labeling. Quantitative proteomic analysis using high resolution mass spectrometry led to the identification of hypophosphorylated proteins, which can be the likely substrates for this kinase. In addition, in vitro kinase assays and antibody based validation of the hypophosphorylated sites was carried out. This study will provide a novel insight into the CDPK1 mediated invasion by Plasmodium falciparum.
Project description:In this study we have investigated PfAP2-HC (PF3D7_1456000), a protein that was identified by co-immunoprecipitation with PfHP1 coupled with liquid chromatography-tandem mass spectrometry. PfAP2-HC belongs to the ApiAP2 family, the main transcription factor family in Apicomplexan parasites. We have confirmed that AP2-HC colocalises with HP1 with the use of immunofluorescence assays and chromatin immunoprecipitation-sequencing. We show that PfAP2-HC is not required for heterochromatin maintenance and inheritance with the use of PfAP2-HC Kock out and knockdown. We show with transcriptome-wide microarray time course analysis that PfAP2-HC does not act as a transcription factor in blood stage parasites. We demonstrate that the AP2 domain is dispensable for heterochromatin targeting by introducing a premature stop codon before the AP2 domain. We show that PfAP2-HC binding to heterochromatin dependents on PfHP1. and PfAP2-HC is likely not involved in de novo heterochromatin formation
Project description:Obligate intracellular parasites must efficiently invade host cells in order to mature and be transmitted. For the malaria parasite Plasmodium falciparum, invasion of host red blood cells (RBCs) is essential. Here we describe a parasite-specific transcription factor belonging to the Apicomplexan Apetala 2 (ApiAP2) family that is responsible for regulating the expression of a subset of merozoite genes involved in RBC invasion (PfAP2-I). Our genome-wide analysis by ChIP-seq shows that PfAP2-I interacts with a specific DNA motif in the promoters of these genes. msp5 transcription levels decrease when the PfAP2-I DNA-binding motif is mutated in PfAP2-I-GFP parasites, showing that PfAP2-I must bind the DNA motif in order for msp5 to be transcribed.
Project description:Obligate intracellular parasites must efficiently invade host cells in order to mature and be transmitted. For the malaria parasite Plasmodium falciparum, invasion of host red blood cells (RBCs) is essential. Here we describe a parasite-specific transcription factor belonging to the Apicomplexan Apetala 2 (ApiAP2) family that is responsible for regulating the expression of a subset of merozoite genes involved in RBC invasion (PfAP2-I). Our genome-wide analysis by ChIP-seq shows that PfAP2-I interacts with a specific DNA motif in the promoters of these genes. msp5 transcription levels decrease when the PfAP2-I DNA-binding motif is mutated in PfAP2-I-GFP parasites, showing that PfAP2-I must bind the DNA motif in order for msp5 to be transcribed.
Project description:Malarial parasite pathogenicity results from its ability to invade and remodel red blood cells (RBCs), expressing antigenic variant proteins for immune evasion and survival, and then to egress from the host cell. These sequential processes require concerted actions of a large number of proteins during the intraerythrocytic developmental cycle (IDC), but the molecular basis of the required regulation is only partially understood. Here, we have characterized an essential Apicomplexan AP2 (ApiAP2) transcription factor (we refer to it as PfAP2-P; Master Regulator of Pathogenesis) that shows two peaks of expression during the IDC at 16- and 40-hour post invasion (h.p.i.). When expression of PfAP2-P at 40 h.p.i. was disrupted using an inducible gene knockout approach, ∆PfAP2-P parasites unable to form mature merozoites and egress from the host RBCs owing to strong down-regulation of several known egress- and invasion-associated genes, in addition to several novel hypothetical genes of thought to be involved in these key life cycle processes during the IDC. Disruption of PfAP2-P expression at 16 h.p.i. results in transcriptional activation of virtually majority of silenced var genes observed at both bulk and single cell level. This is also reflected by significantly higher level of recognition of the exported proteins on the ∆PfAP2-P parasite-infected RBCs by pooled sera from malaria-exposed individuals from endemic region. In addition, over expression of many early gametocyte marker genes was also observed in ∆PfAP2-P parasites at both 40 h.p.i., and at 16 h.p.i. PfAP2-P directly regulates these genes by binding to their promoter region or indirectly through 14 other down-stream AP2 transcription factors. Taken together, we conclude that PfAP2-P is an upstream transcriptional regulator that participates in mutually exclusive expression pattern shown by the var family of genes and a critical determinant of parasite’s growth during the IDC.
Project description:Malarial parasite pathogenicity results from its ability to invade and remodel red blood cells (RBCs), expressing antigenic variant proteins for immune evasion and survival, and then to egress from the host cell. These sequential processes require concerted actions of a large number of proteins during the intraerythrocytic developmental cycle (IDC), but the molecular basis of the required regulation is only partially understood. Here, we have characterized an essential Apicomplexan AP2 (ApiAP2) transcription factor (we refer to it as PfAP2-P; Pathogenesis) that shows two peaks of expression during the IDC at 16- and 40-hour post invasion (h.p.i.). When expression of PfAP2-P at 40 h.p.i. was disrupted using an inducible gene knockout approach, ∆PfAP2-P parasites unable to form mature merozoites and egress from the host RBCs owing to strong down-regulation of several known egress- and invasion-associated genes, in addition to several novel hypothetical genes of thought to be involved in these key life cycle processes during the IDC. Disruption of PfAP2-P expression at 16 h.p.i. results in transcriptional activation of virtually majority of silenced var genes observed at both bulk and single cell level. This is also reflected by significantly higher level of recognition of the exported proteins on the ∆PfAP2-P parasite-infected RBCs by pooled sera from malaria-exposed individuals from endemic region. In addition, over-expression of many early gametocyte marker genes was also observed in ∆PfAP2-P parasites at both 40 h.p.i., and at 16 h.p.i. PfAP2-P directly regulates these genes by binding to their promoter region or indirectly through 14 other down-stream AP2 transcription factors. Taken together, we conclude that PfAP2-P is an upstream transcriptional regulator that participates in mutually exclusive expression pattern shown by the var family of genes and a critical determinant of parasite’s growth during the IDC.
Project description:Malarial parasite pathogenicity results from its ability to invade and remodel red blood cells (RBCs), expressing antigenic variant proteins for immune evasion and survival, and then to egress from the host cell. These sequential processes require concerted actions of a large number of proteins during the intraerythrocytic developmental cycle (IDC), but the molecular basis of the required regulation is only partially understood. Here, we have characterized an essential Apicomplexan AP2 (ApiAP2) transcription factor (we refer to it as PfAP2-P; Pathogenesis) that shows two peaks of expression during the IDC at 16- and 40-hour post invasion (h.p.i.). When expression of PfAP2-P at 40 h.p.i. was disrupted using an inducible gene knockout approach, ∆PfAP2-P parasites unable to form mature merozoites and egress from the host RBCs owing to strong down-regulation of several known egress- and invasion-associated genes, in addition to several novel hypothetical genes of thought to be involved in these key life cycle processes during the IDC. Disruption of PfAP2-P expression at 16 h.p.i. results in transcriptional activation of virtually majority of silenced var genes observed at both bulk and single cell level. This is also reflected by significantly higher level of recognition of the exported proteins on the ∆PfAP2-P parasite-infected RBCs by pooled sera from malaria-exposed individuals from endemic region. In addition, over-expression of many early gametocyte marker genes was also observed in ∆PfAP2-P parasites at both 40 h.p.i., and at 16 h.p.i. PfAP2-P directly regulates these genes by binding to their promoter region or indirectly through 14 other down-stream AP2 transcription factors. Taken together, we conclude that PfAP2-P is an upstream transcriptional regulator that participates in mutually exclusive expression pattern shown by the var family of genes and a critical determinant of parasite’s growth during the IDC.