scholarly journals Defining the Morphology and Mechanism of the Hemoglobin Transport Pathway in Plasmodium falciparum-Infected Erythrocytes

2015 ◽  
Vol 14 (4) ◽  
pp. 415-426 ◽  
Author(s):  
Katharine J. Milani ◽  
Timothy G. Schneider ◽  
Theodore F. Taraschi
Keyword(s):  
Plasmodium Falciparum ◽  
Three Dimensional ◽  
Parasite Development ◽  
Transport Pathway ◽  
Trophozoite Stage ◽  
Pharmacological Agents ◽  
Content Type ◽  
Protein Receptor ◽  
Morphological Organization ◽  
Hemoglobin Degradation

ABSTRACT Hemoglobin degradation during the asexual cycle of Plasmodium falciparum is an obligate process for parasite development and survival. It is established that hemoglobin is transported from the host erythrocyte to the parasite digestive vacuole (DV), but this biological process is not well characterized. Three-dimensional reconstructions made from serial thin-section electron micrographs of untreated, trophozoite-stage P. falciparum -infected erythrocytes (IRBC) or IRBC treated with different pharmacological agents provide new insight into the organization and regulation of the hemoglobin transport pathway. Hemoglobin internalization commences with the formation of cytostomes from localized, electron-dense collars at the interface of the parasite plasma and parasitophorous vacuolar membranes. The cytostomal collar does not function as a site of vesicle fission but rather serves to stabilize the maturing cytostome. We provide the first evidence that hemoglobin transport to the DV uses an actin-myosin motor system. Short-lived, hemoglobin-filled vesicles form from the distal end of the cytostomes through actin and dynamin-mediated processes. Results obtained with IRBC treated with N -ethylmaleimide (NEM) suggest that fusion of hemoglobin-containing vesicles with the DV may involve a soluble NEM-sensitive factor attachment protein receptor-dependent mechanism. In this report, we identify new key components of the hemoglobin transport pathway and provide a detailed characterization of its morphological organization and regulation.

scholarly journals Altered Plasmodium falciparum Sensitivity to the Antiretroviral Protease Inhibitor Lopinavir Associated with Polymorphisms in pfmdr1

2016 ◽  
Vol 61 (1) ◽  
Author(s):  
Ebere Sonoiki ◽  
Christian Nsanzabana ◽  
Jennifer Legac ◽  
Kirthana M. V. Sindhe ◽  
Joseph DeRisi ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Protease Inhibitor ◽  
Genome Sequencing ◽  
Copy Number ◽  
Hiv Protease ◽  
Parasite Development ◽  
Whole Genome ◽  
Aspartic Proteases ◽  
Content Type

ABSTRACT The HIV protease inhibitor lopinavir inhibits Plasmodium falciparum aspartic proteases (plasmepsins) and parasite development, and children receiving lopinavir-ritonavir experienced fewer episodes of malaria than those receiving other antiretroviral regimens. Resistance to lopinavir was selected in vitro over ∼9 months, with ∼4-fold decreased sensitivity. Whole-genome sequencing of resistant parasites showed a mutation and increased copy number in pfmdr1 and a mutation in a protein of unknown function, but no polymorphisms in plasmepsin genes.

scholarly journals Plasmodium falciparum Founder Populations in Western Cambodia Have Reduced Artemisinin SensitivityIn Vitro

2014 ◽  
Vol 58 (8) ◽  
pp. 4935-4937 ◽  
Author(s):  
Chanaki Amaratunga ◽  
Benoit Witkowski ◽  
Dalin Dek ◽  
Vorleak Try ◽  
Nimol Khim ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Parasite Clearance ◽  
Parasite Development ◽  
Ring Stage ◽  
Content Type ◽  
Short Course ◽  
Founder Populations ◽  
Admixed Population ◽  
Survival Assay

ABSTRACTReducedPlasmodium falciparumsensitivity to short-course artemisinin (ART) monotherapy manifests as a long parasite clearance half-life. We recently defined three parasite founder populations with long half-lives in Pursat, western Cambodia, where reduced ART sensitivity is prevalent. Using the ring-stage survival assay, we show that these founder populations have reduced ART sensitivityin vitroat the early ring stage of parasite development and that a genetically admixed population contains subsets of parasites with normal or reduced ART sensitivity.

scholarly journals Fucosylated Chondroitin Sulfate Inhibits Plasmodium falciparum Cytoadhesion and Merozoite Invasion

2014 ◽  
Vol 58 (4) ◽  
pp. 1862-1871 ◽  
Author(s):  
Marcele F. Bastos ◽  
Letusa Albrecht ◽  
Eliene O. Kozlowski ◽  
Stefanie C. P. Lopes ◽  
Yara C. Blanco ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Plasmodium Falciparum ◽  
Chondroitin Sulfate ◽  
Parasite Development ◽  
Flow Conditions ◽  
Inhibitory Effects ◽  
Merozoite Invasion ◽  
Content Type ◽  
Life Threatening ◽  
Lung Endothelial Cells

ABSTRACTSequestration ofPlasmodium falciparum-infected erythrocytes (Pf-iEs) in the microvasculature of vital organs plays a key role in the pathogenesis of life-threatening malaria complications, such as cerebral malaria and malaria in pregnancy. This phenomenon is marked by the cytoadhesion of Pf-iEs to host receptors on the surfaces of endothelial cells, on noninfected erythrocytes, and in the placental trophoblast; therefore, these sites are potential targets for antiadhesion therapies. In this context, glycosaminoglycans (GAGs), including heparin, have shown the ability to inhibit Pf-iE cytoadherence and growth. Nevertheless, the use of heparin was discontinued due to serious side effects, such as bleeding. Other GAG-based therapies were hampered due to the potential risk of contamination with prions and viruses, as some GAGs are isolated from mammals. In this context, we investigated the effects and mechanism of action of fucosylated chondroitin sulfate (FucCS), a unique and highly sulfated GAG isolated from the sea cucumber, with respect toP. falciparumcytoadhesion and development. FucCS was effective in inhibiting the cytoadherence of Pf-iEs to human lung endothelial cells and placenta cryosections under static and flow conditions. Removal of the sulfated fucose branches of the FucCS structure virtually abolished the inhibitory effects of FucCS. Importantly, FucCS rapidly disrupted rosettes at high levels, and it was also able to block parasite development by interfering with merozoite invasion. Collectively, these findings highlight the potential of FucCS as a candidate for adjunct therapy against severe malaria.

scholarly journals RNA Secondary Structurome Revealed Distinct Thermoregulation in Plasmodium falciparum

2022 ◽  
Vol 9 ◽  
Author(s):  
Yanwei Qi ◽  
Yuhong Zhang ◽  
Quankai Mu ◽  
Guixing Zheng ◽  
Mengxin Zhang ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Secondary Structure ◽  
Rna Structure ◽  
Rna Secondary Structure ◽  
Structural Changes ◽  
Environmental Changes ◽  
Parasite Development ◽  
Temperature Dependent ◽  
Trophozoite Stage ◽  
Temperature Changes

The development of Plasmodium parasites, a causative agent of malaria, requests two hosts and the completion of 11 different parasite stages during development. Therefore, an efficient and fast response of parasites to various complex environmental changes, such as ambient temperature, pH, ions, and nutrients, is essential for parasite development and survival. Among many of these environmental changes, temperature is a decisive factor for parasite development and pathogenesis, including the thermoregulation of rRNA expression, gametogenesis, and parasite sequestration in cerebral malaria. However, the exact mechanism of how Plasmodium parasites rapidly respond and adapt to temperature change remains elusive. As a fundamental and pervasive regulator of gene expression, RNA structure can be a specific mechanism for fine tuning various biological processes. For example, dynamic and temperature-dependent changes in RNA secondary structures can control the expression of different gene programs, as shown by RNA thermometers. In this study, we applied the in vitro and in vivo transcriptomic-wide secondary structurome approach icSHAPE to measure parasite RNA structure changes with temperature alteration at single-nucleotide resolution for ring and trophozoite stage parasites. Among 3,000 probed structures at different temperatures, our data showed structural changes in the global transcriptome, such as S-type rRNA, HRPII gene, and the erythrocyte membrane protein family. When the temperature drops from 37°C to 26°C, most of the genes in the trophozoite stage cause significantly more changes to the RNA structure than the genes in the ring stage. A multi-omics analysis of transcriptome data from RNA-seq and RNA structure data from icSHAPE reveals that the specific RNA secondary structure plays a significant role in the regulation of transcript expression for parasites in response to temperature changes. In addition, we identified several RNA thermometers (RNATs) that responded quickly to temperature changes. The possible thermo-responsive RNAs in Plasmodium falciparum were further mapped. To this end, we identified dynamic and temperature-dependent RNA structural changes in the P. falciparum transcriptome and performed a comprehensive characterization of RNA secondary structures over the course of temperature stress in blood stage development. These findings not only contribute to a better understanding of the function of the RNA secondary structure but may also provide novel targets for efficient vaccines or drugs.

scholarly journals Scanning electron microscope-analysis of the protrusions (knobs) present on the surface of Plasmodium falciparum-infected erythrocytes.

1983 ◽  
Vol 97 (3) ◽  
pp. 795-802 ◽  
Author(s):  
J Gruenberg ◽  
D R Allred ◽  
I W Sherman
Keyword(s):  
Plasmodium Falciparum ◽  
Cell Surface ◽  
Parasite Development ◽  
Red Cell ◽  
Schizont Stage ◽  
Dynamic Changes ◽  
Trophozoite Stage ◽  
Parasite Plasmodium Falciparum ◽  
Surface Patterns ◽  
Scanning Electron

The nature of the surface deformations of erythrocytes infected with the human malaria parasite Plasmodium falciparum was analyzed using scanning electron microscopy at two stages of the 48-h parasite maturation cycle. Infected cells bearing trophozoite-stage parasites (24-36 h) had small protrusions (knobs), with diameters varying from 160 to 110 nm, and a density ranging from 10 to 35 knobs X micron-2. When parasites were fully mature (schizont stage, 40-44 h), knob size decreased (100-70 nm), whereas density increased (45-70 knobs X micron-2). Size and density of the knobs varied inversely, suggesting that knob production (a) occurred throughout intraerythrocytic parasite development from trophozoite to schizont and (b) was related to dynamic changes of the erythrocyte membrane. Variation in the distribution of the knobs over the red cell surface was observed during parasite maturation. At the early trophozoite stage of parasite development, knobs appeared to be formed in particular domains of the cell surface. As the density of knobs increased and they covered the entire cell surface, their lateral distribution was dispersive (more-than-random); this was particularly evident at the schizont stage. Regional surface patterns of knobs (rows, circles) were seen throughout parasite development. The nature of the dynamic changes that occurred at the red cell surface during knob formation, as well as the nonrandom distribution of knobs, suggested that the red cell cytoskeleton may have played a key role in knob formation and patterning.

scholarly journals Limonene Arrests Parasite Development and Inhibits Isoprenylation of Proteins in Plasmodium falciparum

2001 ◽  
Vol 45 (9) ◽  
pp. 2553-2558 ◽  
Author(s):  
Ivan Cruz Moura ◽  
Gerhard Wunderlich ◽  
Maria L. Uhrig ◽  
Alicia S. Couto ◽  
Valnice J. Peres ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Protein Modification ◽  
Eukaryotic Cells ◽  
Parasite Development ◽  
Farnesyl Pyrophosphate ◽  
Ring Stage ◽  
Ras Proteins ◽  
Trophozoite Stage ◽  
Isoprenoid Metabolism ◽  
Layer Chromatography

ABSTRACT Isoprenylation is an essential protein modification in eukaryotic cells. Herein, we report that in Plasmodium falciparum, a number of proteins were labeled upon incubation of intraerythrocytic forms with either [3H]farnesyl pyrophosphate or [3H]geranylgeranyl pyrophosphate. By thin-layer chromatography, we showed that attached isoprenoids are partially modified to dolichol and other, uncharacterized, residues, confirming active isoprenoid metabolism in this parasite. Incubation of blood-stage P. falciparum treated with the isoprenylation inhibitor limonene significantly decreased the parasites' progression from the ring stage to the trophozoite stage and at 1.22 mM, 50% of the parasites died after the first cycle. Using Ras- and Rap-specific monoclonal antibodies, putative Rap and Ras proteins of P. falciparum were immunoprecipitated. Upon treatment with 0.5 mM limonene, isoprenylation of these proteins was significantly decreased, possibly explaining the observed arrest of parasite development.

scholarly journals The Plasmodium falciparum Artemisinin Susceptibility-Associated AP-2 Adaptin μ Subunit is Clathrin Independent and Essential for Schizont Maturation

mBio ◽  
2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Ryan C. Henrici ◽  
Rachel L. Edwards ◽  
Martin Zoltner ◽  
Donelly A. van Schalkwyk ◽  
Melissa N. Hart ◽  
...  
Keyword(s):  
Drug Resistance ◽  
Plasmodium Falciparum ◽  
Cellular Localization ◽  
Gene Knockout ◽  
Mass Spectrometry Analysis ◽  
Parasite Development ◽  
Content Type ◽  
Spectrometry Analysis ◽  
Fluorescence And Electron Microscopy ◽  
Kelch Domain

ABSTRACT The efficacy of current antimalarial drugs is threatened by reduced susceptibility of Plasmodium falciparum to artemisinin, associated with mutations in pfkelch13. Another gene with variants known to modulate the response to artemisinin encodes the μ subunit of the AP-2 adaptin trafficking complex. To elucidate the cellular role of AP-2μ in P. falciparum, we performed a conditional gene knockout, which severely disrupted schizont organization and maturation, leading to mislocalization of key merozoite proteins. AP-2μ is thus essential for blood-stage replication. We generated transgenic P. falciparum parasites expressing hemagglutinin-tagged AP-2μ and examined cellular localization by fluorescence and electron microscopy. Together with mass spectrometry analysis of coimmunoprecipitating proteins, these studies identified AP-2μ-interacting partners, including other AP-2 subunits, the K10 kelch-domain protein, and PfEHD, an effector of endocytosis and lipid mobilization, but no evidence was found of interaction with clathrin, the expected coat protein for AP-2 vesicles. In reverse immunoprecipitation experiments with a clathrin nanobody, other heterotetrameric AP-complexes were shown to interact with clathrin, but AP-2 complex subunits were absent. IMPORTANCE We examine in detail the AP-2 adaptin complex from the malaria parasite Plasmodium falciparum. In most studied organisms, AP-2 is involved in bringing material into the cell from outside, a process called endocytosis. Previous work shows that changes to the μ subunit of AP-2 can contribute to drug resistance. Our experiments show that AP-2 is essential for parasite development in blood but does not have any role in clathrin-mediated endocytosis. This suggests that a specialized function for AP-2 has developed in malaria parasites, and this may be important for understanding its impact on drug resistance.

scholarly journals In search of a selective inhibitor of the induced transport of small solutes in Plasmodium falciparum-infected erythrocytes: effects of arylaminobenzoates

1995 ◽  
Vol 311 (3) ◽  
pp. 761-768 ◽  
Author(s):  
K Kirk ◽  
H A Horner
Keyword(s):  
Plasmodium Falciparum ◽  
Mammalian Cells ◽  
High Capacity ◽  
Transport Systems ◽  
Single Type ◽  
Transport Pathway ◽  
Choline Transport ◽  
Pharmacological Agents ◽  
Diverse Range

Following invasion of the human erythrocyte by the malaria parasite, Plasmodium falciparum, there appear in the parasitized cell new, high-capacity permeation pathways that transport a diverse range of low-molecular-mass solutes. In this study a series of 16 arylaminobenzoates, analogues of the Cl- channel blocker 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB), were tested for their effects on the transport of choline, a univalent cation, into malaria-infected cells. A number of the arylaminobenzoates were found to be potent inhibitors of malaria-induced choline transport and to be similarly effective at blocking the induced transport of the uncharged pyrimidine nucleoside thymidine and the univalent anion lactate. The data are consistent with the hypothesis that much of the induced transport of cations, anions and non-electrolytes into parasitized cells is via broad-specificity, anion-selective pathways of a single type. A comparison of the effects of the arylaminobenzoates on malaria-induced transport with their effects on a number of representative anion transport systems in normal mammalian cells suggests that it is possible to identify pharmacological agents that block the malaria-induced pathway while not significantly affecting important transport mechanisms in host tissues. The most potent of the induced-transport inhibitors identified were shown to inhibit [3H]hypoxanthine incorporation in in vitro parasite growth assays. These data support the view that the induced-transport pathway may be a viable pharmacological target.

Plasmodium falciparum cysteine protease falcipain-2 cleaves erythrocyte membrane skeletal proteins at late stages of parasite development

Blood ◽  
2002 ◽  
Vol 100 (3) ◽  
pp. 1048-1054 ◽  
Author(s):  
Manjit Hanspal ◽  
Meenakshi Dua ◽  
Yuichi Takakuwa ◽  
Athar H. Chishti ◽  
Akiko Mizuno
Keyword(s):  
Plasmodium Falciparum ◽  
Erythrocyte Membrane ◽  
Cysteine Protease ◽  
Peptide Sequence ◽  
Actin Binding ◽  
Parasite Development ◽  
Trophozoite Stage ◽  
Protein 4.1 ◽  
Late Stages ◽  
Late Trophozoite

Abstract Plasmodium falciparum–derived cysteine protease falcipain-2 cleaves host erythrocyte hemoglobin at acidic pH and specific components of the membrane skeleton at neutral pH. Analysis of stage-specific expression of these 2 proteolytic activities of falcipain-2 shows that hemoglobin-hydrolyzing activity is maximum in early trophozoites and declines rapidly at late stages, whereas the membrane skeletal protein hydrolyzing activity is markedly increased at the late trophozoite and schizont stages. Among the erythrocyte membrane skeletal proteins, ankyrin and protein 4.1 are cleaved by native and recombinant falcipain-2 near their C-termini. To identify the precise peptide sequence at the hydrolysis site of protein 4.1, we used a recombinant construct of protein 4.1 as substrate followed by MALDI-MS analysis of the cleaved product. We show that falcipain-2–mediated cleavage of protein 4.1 occurs immediately after lysine 437, which lies within a region of the spectrin–actin-binding domain critical for erythrocyte membrane stability. A 16-mer peptide containing the cleavage site completely inhibited the enzyme activity and blocked falcipain-2–induced fragmentation of erythrocyte ghosts. Based on these results, we propose that falcipain-2 cleaves hemoglobin in the acidic food vacuole at the early trophozoite stage, whereas it cleaves specific components of the red cell skeleton at the late trophozoite and schizont stages. It is the proteolysis of skeletal proteins that causes membrane instability, which, in turn, facilitates parasite release in vivo.

scholarly journals Plasmodium falciparum exports the Golgi marker sphingomyelin synthase into a tubovesicular network in the cytoplasm of mature erythrocytes

1994 ◽  
Vol 124 (4) ◽  
pp. 449-462 ◽  
Author(s):  
HG Elmendorf ◽  
K Haldar
Keyword(s):  
Plasmodium Falciparum ◽  
Plasma Membrane ◽  
Mammalian Cells ◽  
Three Dimensional ◽  
Eukaryotic Cell ◽  
Biosynthetic Activity ◽  
Trophozoite Stage ◽  
Mature Erythrocyte ◽  
Sphingomyelin Synthase ◽  
Membrane Development

This work describes two unusual features of membrane development in a eukaryotic cell. (a) The induction of an extensive network of tubovesicular membranes by the malaria parasite Plasmodium falciparum in the cytoplasm of the mature erythrocyte, and its visualization with two ceramide analogues C5-DMB-ceramide and C6-NBD-ceramide. "Sectioning" of the infected erythrocytes using laser confocal microscopy has allowed the reconstruction of detailed three-dimensional images of this novel membrane network. (b) The stage-specific export of sphingomyelin synthase, a biosynthetic activity concentrated in the Golgi of mammalian cells, to this tubovesicular network. Evidence is presented that in the extracellular merozoite stage the parasite retains sphingomyelin synthase within its plasma membrane. However, intracellular ring- and trophozoite-stage parasites export a substantial fraction (approximately 26%) of sphingomyelin synthase activity to membranes beyond their plasma membrane. Importantly we do not observe synthesis of new enzyme during these intracellular stages. Taken together these results strongly suggest that the export of this classic Golgi enzyme is developmentally regulated in Plasmodium. We discuss the significance of this export and the tubovesicular network with respect to membrane development and function in the erythrocyte cytosol.

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