Malaria remains one of the greatest public health challenges worldwide, particularly in sub-Saharan Africa. The clinical outcome of individuals infected with Plasmodium falciparum parasites depends ...on many factors including host systemic inflammatory responses, parasite sequestration in tissues and vascular dysfunction. Production of pro-inflammatory cytokines and chemokines promotes endothelial activation as well as recruitment and infiltration of inflammatory cells, which in turn triggers further endothelial cell activation and parasite sequestration. Inflammatory responses are triggered in part by bioactive parasite products such as hemozoin and infected red blood cell-derived extracellular vesicles (iRBC-derived EVs). Here we demonstrate that such EVs contain functional miRNA-Argonaute 2 complexes that are derived from the host RBC. Moreover, we show that EVs are efficiently internalized by endothelial cells, where the miRNA-Argonaute 2 complexes modulate target gene expression and barrier properties. Altogether, these findings provide a mechanistic link between EVs and vascular dysfunction during malaria infection.
Malaria blood stage parasites export a large number of proteins into their host erythrocyte to change it from a container of predominantly hemoglobin optimized for the transport of oxygen into a ...niche for parasite propagation. To understand this process, it is crucial to know which parasite proteins are exported into the host cell. This has been aided by the PEXEL/HT sequence, a five-residue motif found in many exported proteins, leading to the prediction of the exportome. However, several PEXEL/HT negative exported proteins (PNEPs) indicate that this exportome is incomplete and it remains unknown if and how many further PNEPs exist. Here we report the identification of new PNEPs in the most virulent malaria parasite Plasmodium falciparum. This includes proteins with a domain structure deviating from previously known PNEPs and indicates that PNEPs are not a rare exception. Unexpectedly, this included members of the MSP-7 related protein (MSRP) family, suggesting unanticipated functions of MSRPs. Analyzing regions mediating export of selected new PNEPs, we show that the first 20 amino acids of PNEPs without a classical N-terminal signal peptide are sufficient to promote export of a reporter, confirming the concept that this is a shared property of all PNEPs of this type. Moreover, we took advantage of newly found soluble PNEPs to show that this type of exported protein requires unfolding to move from the parasitophorous vacuole (PV) into the host cell. This indicates that soluble PNEPs, like PEXEL/HT proteins, are exported by translocation across the PV membrane (PVM), highlighting protein translocation in the parasite periphery as a general means in protein export of malaria parasites.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Blood stages of Plasmodium falciparum cause the pathology of malaria; however, the progression of the parasite through this complex part of the life cycle has never been visualized. In this study, we ...use four-dimensional imaging to show for the first time the development of individual parasites in erythrocytes and the concomitant host cell modifications. Our data visualize an unexpectedly dynamic parasite, provide a reference for this life cycle stage and challenge the model that protein export in P. falciparum is linked to the biogenesis of host cell modifications termed Maurer's clefts. Our results provide a novel view of the blood-stage development, Maurer's cleft development and protein export in malaria parasites, and open the door to study dynamic processes, drug effects and the phenotype of mutants.
Transmission represents a population bottleneck in the Plasmodium life cycle and a key intervention target of ongoing efforts to eradicate malaria. Sexual differentiation is essential for this ...process, as only sexual parasites, called gametocytes, are infective to the mosquito vector. Gametocyte production rates vary depending on environmental conditions, but external stimuli remain obscure. Here, we show that the host-derived lipid lysophosphatidylcholine (LysoPC) controls P. falciparum cell fate by repressing parasite sexual differentiation. We demonstrate that exogenous LysoPC drives biosynthesis of the essential membrane component phosphatidylcholine. LysoPC restriction induces a compensatory response, linking parasite metabolism to the activation of sexual-stage-specific transcription and gametocyte formation. Our results reveal that malaria parasites can sense and process host-derived physiological signals to regulate differentiation. These data close a critical knowledge gap in parasite biology and introduce a major component of the sexual differentiation pathway in Plasmodium that may provide new approaches for blocking malaria transmission.
Display omitted
•P. falciparum sexual differentiation is repressed by LysoPC found in human serum•LysoPC is a major building block of parasite phospholipid metabolism•LysoPC acts upstream of the earliest known events of sexual differentiation•Parasite metabolism alters host LysoPC levels during infection
The host-derived lipid lysophosphatidylcholine controls Plasmodium falciparum cell fate by repressing parasite sexual differentiation, a key step in malaria transmission.
Plasmodium falciparum
accounts for the majority of over 600,000 malaria-associated deaths annually. Parasites resistant to nearly all antimalarials have emerged and the need for drugs with ...alternative modes of action is thus undoubted. The FK506-binding protein
Pf
FKBP35 has gained attention as a promising drug target due to its high affinity to the macrolide compound FK506 (tacrolimus). Whilst there is considerable interest in targeting
Pf
FKBP35 with small molecules, a genetic validation of this factor as a drug target is missing and its function in parasite biology remains elusive. Here, we show that limiting
Pf
FKBP35 levels are lethal to
P. falciparum
and result in a delayed death-like phenotype that is characterized by defective ribosome homeostasis and stalled protein synthesis. Our data furthermore suggest that FK506, unlike the action of this drug in model organisms, exerts its antiproliferative activity in a
Pf
FKBP35-independent manner and, using cellular thermal shift assays, we identify putative FK506-targets beyond
Pf
FKBP35. In addition to revealing first insights into the function of
Pf
FKBP35, our results show that FKBP-binding drugs can adopt non-canonical modes of action – with major implications for the development of FK506-derived molecules active against
Plasmodium
parasites and other eukaryotic pathogens.
Abstract
Plasmodium vivax has 2 invasion ligand/host receptor pathways (P. vivax Duffy-binding protein/Duffy antigen receptor for chemokines DARC and P. vivax reticulocyte binding protein ...2b/transferrin receptor TfR1) that are promising targets for therapeutic intervention. We optimized invasion assays with isogenic cultured reticulocytes. Using a receptor blockade approach with multiple P. vivax isolates, we found that all strains utilized both DARC and TfR1, but with significant variation in receptor usage. This suggests that P. vivax, like Plasmodium falciparum, uses alternative invasion pathways, with implications for pathogenesis and vaccine development.
The malaria parasite Plasmodium vivax invades reticulocytes using multiple ligand-receptor interactions known as invasion pathways. We found that different P. vivax strains, like Plasmodium falciparum, can use alternative pathways for invasion, with implications for pathogenesis and vaccine development.
Plasmodium falciparum is a human-adapted apicomplexan parasite that causes the most dangerous form of malaria. P. falciparum cysteine-rich protective antigen (PfCyRPA) is an invasion complex protein ...essential for erythrocyte invasion. The precise role of PfCyRPA in this process has not been resolved. Here, we show that PfCyRPA is a lectin targeting glycans terminating with α2-6-linked N-acetylneuraminic acid (Neu5Ac). PfCyRPA has a >50-fold binding preference for human, α2-6-linked Neu5Ac over non-human, α2-6-linked N-glycolylneuraminic acid. PfCyRPA lectin sites were predicted by molecular modeling and validated by mutagenesis studies. Transgenic parasite lines expressing endogenous PfCyRPA with single amino acid exchange mutants indicated that the lectin activity of PfCyRPA has an important role in parasite invasion. Blocking PfCyRPA lectin activity with small molecules or with lectin-site-specific monoclonal antibodies can inhibit blood-stage parasite multiplication. Therefore, targeting PfCyRPA lectin activity with drugs, immunotherapy, or a vaccine-primed immune response is a promising strategy to prevent and treat malaria.
Display omitted
•Plasmodium falciparum CyRPA binds to carbohydrates with terminal 2-6-linked Neu5Ac•Lectin activity of Plasmodium falciparum CyRPA contributes to erythrocyte invasion•Targeting lectin activity with drugs and antibodies is a promising anti-malarial strategy
Day et al. show that the essential Plasmodium falciparum invasion protein PfCyRPA is a lectin targeting 2-6-linked Neu5Ac. Molecular modeling, mutagenesis, and transgenic parasite studies show that PfCyRPA lectin activity is required for erythrocyte invasion. Drug and antibody inhibitors validate this activity as a therapeutic target to prevent and treat malaria.
A recent report by Jennison et al. reveals an important role for plasmepsin V (PMV), an aspartyl protease, in the development of malaria transmission stages. The authors showed that PMV activity is ...critical for protein export in these stages and that specific PMV inhibitors block parasite transmission to mosquitoes.
Malaria pathogenesis is caused by the replication of Plasmodium parasites within the red blood cells (RBCs) of the vertebrate host. This selective pressure has favored the evolution of protective ...polymorphisms in erythrocyte proteins, a subset of which serve as cognate receptors for parasite invasion ligands. Recently, the generation of RBCs from immortalized hematopoietic stem cells (HSCs) has offered a more tractable system for genetic manipulation and long-term in vitro culture, enabling elucidation of the functional determinants of host susceptibility in vitro. Here we report the generation of an immortalized erythroid progenitor cell line (EJ cells) from as few as 100 000 peripheral blood mononuclear cells. It offers a robust method for the creation of customized model systems from small volumes of peripheral blood. The EJ cell differentiation mirrored erythropoiesis of primary HSCs, yielding orthochromatic erythroblasts and enucleated RBCs after eight days (ejRBCs). The ejRBCs supported invasion by both P. vivax and P. falciparum. To demonstrate the genetic tractability of this system, we used CRISPR/Cas9 to disrupt the Duffy Antigen/Receptor for Chemokines (DARC) gene, which encodes the canonical receptor of P. vivax in humans. Invasion of P. vivax into this DARC-knockout cell line was strongly inhibited providing direct genetic evidence that P. vivax requires DARC for RBC invasion. Further, genetic complementation of DARC restored P. vivax invasion. Taken together, the peripheral blood immortalization method presented here offers the capacity to generate biologically representative model systems for studies of blood-stage malaria invasion from the peripheral blood of donors harboring unique genetic backgrounds, or rare polymorphisms.
Summary
Plasmodium knowlesi is a simian malaria parasite primarily infecting macaque species in Southeast Asia. Although its capacity to infect humans has been recognized since the early part of the ...last century, it has recently become evident that human infections are widespread and potentially life threatening. Historically, P. knowlesi has proven to be a powerful tool in early studies of malaria parasites, providing key breakthroughs in understanding many aspects of Plasmodium biology. However, the necessity to grow the parasite either in macaques or in vitro using macaque blood restricted research to laboratories with access to these resources. The recent adaptation of P. knowlesi to grow and proliferate in vitro in human red blood cells (RBCs) is therefore a substantial step towards revitalizing and expanding research on P. knowlesi. Furthermore, the development of a highly efficient transfection system to genetically modify the parasite makes P. knowlesi an ideal model to study parasite biology. In this review, we elaborate on the importance of P. knowlesi in earlier phases of malaria research and highlight the future potential of the newly available human adapted P. knowlesi parasite lines.
PDF
