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.

Actomyosin motor in the merozoite of the malaria parasite, Plasmodium falciparum: implications for red cell invasion

1998 ◽  
Vol 111 (13) ◽  
pp. 1831-1839 ◽  
Author(s):  
J.C. Pinder ◽  
R.E. Fowler ◽  
A.R. Dluzewski ◽  
L.H. Bannister ◽  
F.M. Lavin ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Plasma Membrane ◽  
Toxoplasma Gondii ◽  
Malaria Parasite ◽  
Cellular Protein ◽  
Red Cell ◽  
Parasite Protein ◽  
Ionic Detergent ◽  
Parasite Plasmodium ◽  
Parasite Plasmodium Falciparum

The genome of the malaria parasite, Plasmodium falciparum, contains a myosin gene sequence, which bears a close homology to one of the myosin genes found in another apicomplexan parasite, Toxoplasma gondii. A polyclonal antibody was generated against an expressed polypeptide of molecular mass 27,000, based on part of the deduced sequence of this myosin. The antibody reacted with the cognate antigen and with a component of the total parasite protein on immunoblots, but not with vertebrate striated or smooth muscle myosins. It did, however, recognise two components in the cellular protein of Toxoplasma gondii. The antibody was used to investigate stage-specificity of expression of the myosin (here designated Pf-myo1) in P. falciparum. The results showed that the protein is synthesised in mature schizonts and is present in merozoites, but vanishes after the parasite enters the red cell. Pf-myo1 was found to be largely, though not entirely, associated with the particulate parasite cell fraction and is thus presumably mainly membrane bound. It was not solubilised by media that would be expected to dissociate actomyosin or myosin filaments, or by non-ionic detergent. Immunofluorescence revealed that in the merozoite and mature schizont Pf-myo1 is predominantly located around the periphery of the cell. Immuno-gold electron microscopy also showed the presence of the myosin around almost the entire parasite periphery, and especially in the region surrounding the apical prominence. Labelling was concentrated under the plasma membrane but was not seen in the apical prominence itself. This suggests that Pf-myo1 is associated with the plasma membrane or with the outer membrane of the subplasmalemmal cisterna, which forms a lining to the plasma membrane, with a gap at the apical prominence. The results lead to a conjectural model of the invasion mechanism.

scholarly journals Interplay of Plasmodium falciparum and thrombin in brain endothelial barrier disruption

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Marion Avril ◽  
Max Benjamin ◽  
Mary-Margaret Dols ◽  
Joseph D. Smith
Keyword(s):  
Plasmodium Falciparum ◽  
Endothelial Permeability ◽  
Endothelial Activation ◽  
Mature Stage ◽  
Microvascular Endothelial Cell ◽  
Schizont Stage ◽  
Trophozoite Stage ◽  
Barrier Disruption ◽  
Inflammatory Stimuli ◽  
Factor Α

Abstract Recent concepts suggest that both Plasmodium falciparum factors and coagulation contribute to endothelial activation and dysfunction in pediatric cerebral malaria (CM) pathology. However, there is still limited understanding of how these complex inflammatory stimuli are integrated by brain endothelial cells. In this study, we examined how mature-stage P. falciparum infected erythrocytes (IE) interact with tumor necrosis factor α (TNFα) and thrombin in the activation and permeability of primary human brain microvascular endothelial cell (HBMEC) monolayers. Whereas trophozoite-stage P. falciparum-IE have limited effect on the viability of HBMEC or the secretion of pro-inflammatory cytokines or chemokines, except at super physiological parasite-host cell ratios, schizont-stage P. falciparum-IE induced low levels of cell death. Additionally, schizont-stage parasites were more barrier disruptive than trophozoite-stage P. falciparum-IE and prolonged thrombin-induced barrier disruption in both resting and TNFα-activated HBMEC monolayers. These results provide evidence that parasite products and thrombin may interact to increase brain endothelial permeability.

scholarly journals Exploring the lower thermal limits for development of the human malaria parasite, Plasmodium falciparum

2019 ◽  
Vol 15 (6) ◽  
pp. 20190275 ◽  
Author(s):  
Jessica L. Waite ◽  
Eunho Suh ◽  
Penelope A. Lynch ◽  
Matthew B. Thomas
Keyword(s):  
Plasmodium Falciparum ◽  
Future Climate Change ◽  
Parasite Development ◽  
Temperature Dependent ◽  
Human Malaria Parasite ◽  
Thermal Limits ◽  
Degree Day ◽  
Extrinsic Incubation Period ◽  
Parasite Plasmodium ◽  
Parasite Plasmodium Falciparum

The rate of malaria transmission is strongly determined by parasite development time in the mosquito, known as the extrinsic incubation period (EIP), since the quicker parasites develop, the greater the chance that the vector will survive long enough for the parasite to complete development and be transmitted. EIP is known to be temperature-dependent but this relationship is surprisingly poorly characterized. There is a single degree-day model for EIP of Plasmodium falciparum that derives from a limited number of poorly controlled studies conducted almost a century ago. Here, we show that the established degree-day model greatly underestimates the rate of development of P. falciparum in both Anopheles stephensi and An. gambiae mosquitoes at temperatures in the range of 17–20°C. We also show that realistic daily temperature fluctuation further speeds parasite development. These novel results challenge one of the longest standing models in malaria biology and have potentially important implications for understanding the impacts of future climate change.

scholarly journals Antimalarials increase vesicle pH in Plasmodium falciparum.

1985 ◽  
Vol 101 (6) ◽  
pp. 2302-2309 ◽  
Author(s):  
D J Krogstad ◽  
P H Schlesinger ◽  
I Y Gluzman
Keyword(s):  
Plasmodium Falciparum ◽  
Mammalian Cells ◽  
Human Fibroblasts ◽  
Food Vacuole ◽  
Malarial Parasite ◽  
Red Cell ◽  
Trophozoite Stage ◽  
Weak Bases ◽  
Erythrocytic Cycle ◽  
Initial Ph

The asexual erythrocytic stage of the malarial parasite ingests and degrades the hemoglobin of its host red cell. To study this process, we labeled the cytoplasm of uninfected red cells with fluorescein-dextran, infected those cells with trophozoite- and schizont-rich cultures of Plasmodium falciparum, and harvested them 110-120 h later in the trophozoite stage. After lysis of the red cell cytoplasm with digitonin, the only fluorescence remaining was in small (0.5-0.9 micron) vesicles similar to the parasite's food vacuole. As measured by spectrofluorimetry, the pH of these vesicles was acid (initial pH 5.2-5.4), and they responded to MgATP with acidification and to weak bases such as NH4Cl with alkalinization. These three properties are similar to those obtained with human fibroblasts and suggest that the endocytic vesicles of plasmodia are similar to those of mammalian cells. Each of the antimalarials tested (chloroquine, quinine, and mefloquine) as well as NH4Cl inhibited parasite growth at concentrations virtually identical to those that increased parasite vesicle pH. These results suggest two conclusions: (a) The increases in vesicle pH that we have observed in our digitonin-treated parasite preparation occur at similar concentrations of weak bases and antimalarials in cultures of parasitized erythrocytes, and (b) P. falciparum parasites are exquisitely dependent on vesicle pH during their asexual erythrocytic cycle, perhaps for processes analogous to endocytosis and proteolysis in mammalian cells, and that antimalarials and NH4Cl may act by interfering with these events.

Perturbation of red cell membrane structure during intracellular maturation of Plasmodium falciparum

Science ◽  
1986 ◽  
Vol 232 (4746) ◽  
pp. 102-104 ◽  
Author(s):  
TF Taraschi ◽  
A Parashar ◽  
M Hooks ◽  
H Rubin
Keyword(s):  
Plasmodium Falciparum ◽  
Malarial Parasite ◽  
Erythrocyte Membranes ◽  
Resonance Spectroscopy ◽  
Red Cell ◽  
Red Cell Membrane ◽  
Structural Modifications ◽  
Spin Resonance ◽  
Parasite Plasmodium ◽  
Parasite Plasmodium Falciparum

An experimental approach, which in this study was applied to the malarial system, can be used to analyze the molecular structure and organization of individual phospholipids in a wide variety of biological membranes. Electron spin resonance spectroscopy was used to investigate the structural modifications of the major red cell phospholipids that occur in erythrocyte membranes infected with the human malarial parasite, Plasmodium falciparum. These modifications were correlated with the intracellular developmental stage of the parasite. Phosphatidylcholine, phosphatidylethanolamine, and phosphatidylserine were increasingly disordered (fluidized) as infection progressed. This disordering occurred at different rates and to varying extents.

scholarly journals Protein ubiquitylation is essential for the schizont to merozoite transition in Plasmodium falciparum blood-stage development

2019 ◽  
Author(s):  
Yang Wu ◽  
Vesela Encheva ◽  
Judith L. Green ◽  
Edwin Lasonder ◽  
Adchara Prommaban ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Homology Model ◽  
Food Vacuole ◽  
Blood Stage ◽  
Parasite Development ◽  
Parasite Line ◽  
Schizont Stage ◽  
Post Translational Modification ◽  
Asexual Blood Stage ◽  
Erythrocyte Invasion

AbstractUbiquitylation is a common post translational modification of eukaryotic proteins and in the human malaria parasite, Plasmodium falciparum (Pf) overall ubiquitylation increases in the transition from intracellular schizont to extracellular merozoite stages in the asexual blood stage cycle. Here, we identify specific ubiquitylation sites of protein substrates in three intracellular parasite stages and extracellular merozoites; a total of 1464 sites in 546 proteins were identified (data available via ProteomeXchange with identifier PXD014998). 469 ubiquitylated proteins were identified in merozoites compared with only 160 in the preceding intracellular schizont stage, indicating a large increase in protein ubiquitylation associated with merozoite maturation. Following merozoite invasion of erythrocytes, few ubiquitylated proteins were detected in the first intracellular ring stage but as parasites matured through trophozoite to schizont stages the extent of ubiquitylation increased. We identified commonly used ubiquitylation motifs and groups of ubiquitylated proteins in specific areas of cellular function, for example merozoite pellicle proteins involved in erythrocyte invasion, exported proteins, and histones. To investigate the importance of ubiquitylation we screened ubiquitin pathway inhibitors in a parasite growth assay and identified the ubiquitin activating enzyme (UBA1 or E1) inhibitor MLN7243 (TAK-243) to be particularly effective. This small molecule was shown to be a potent inhibitor of recombinant PfUBA1, and a structural homology model of MLN7243 bound to the parasite enzyme highlights avenues for the development of P. falciparum specific inhibitors. We created a genetically modified parasite with a rapamycin-inducible functional deletion of uba1; addition of either MLN7243 or rapamycin to the recombinant parasite line resulted in the same phenotype, with parasite development blocked at the late schizont stage. These results indicate that the intracellular target of MLN7243 is UBA1, and this activity is essential for the final differentiation of schizonts to merozoites. The ubiquitylation of many merozoite proteins and their disappearance in ring stages are consistent with the idea that ubiquitylation leads to their destruction via the proteasome once their function is complete following invasion, which would allow amino acid recycling in the period prior to the parasite’s elaboration of a new food vacuole.

scholarly journals Altered plasma membrane phospholipid organization in Plasmodium falciparum-infected human erythrocytes

Blood ◽  
1987 ◽  
Vol 69 (2) ◽  
pp. 401-407
Author(s):  
RS Schwartz ◽  
JA Olson ◽  
C Raventos-Suarez ◽  
M Yee ◽  
RH Heath ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Cell Membrane ◽  
Early Stage ◽  
Red Cells ◽  
Membrane Phospholipid ◽  
Cell Membrane Permeability ◽  
Parasite Development ◽  
Red Cell ◽  
Membrane Phospholipids ◽  
Red Cell Membrane

The intraerythrocytic development of the malaria parasite is accompanied by distinct morphological and biochemical changes in the host cell membrane, yet little is known about development-related alterations in the transbilayer organization of membrane phospholipids in parasitized cells. This question was examined in human red cells infected with Plasmodium falciparum. Normal red cells were infected with strain FCR3 or with clonal derivatives that either produce (K+) or do not produce (K-) knobby protuberances on the infected red cells. Parasitized cells were harvested at various stages of parasite development, and the bilayer orientation of red cell membrane phospholipids was determined chemically using 2,4,6-trinitrobenzene sulphonic acid (TNBS) or enzymatically using bee venom phospholipase A2 (PLA2) and sphingomyelinase C (SMC). We found that parasite development was accompanied by distinct alterations in the red cell membrane transbilayer distribution of phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylserine (PS). Increases in the exoplasmic membrane leaflet exposure of PE and PS were larger in the late-stage parasitized cells than in the early-stage parasitized cells. Similar results were obtained for PE membrane distribution using either chemical (TNBS) or enzymatic (PLA2 plus SMC) methods, although changes in PS distribution were observed only with TNBS. Uninfected cohort cells derived from mixed populations of infected and uninfected cells exhibited normal patterns of membrane phospholipid organization. The observed alterations in P falciparum-infected red cell membrane phospholipid distribution, which is independent of the presence or absence of knobby protuberances, might be associated with the drastic changes in cell membrane permeability and susceptibility to early hemolysis observed in the late stages of parasite development.

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 Altered plasma membrane phospholipid organization in Plasmodium falciparum-infected human erythrocytes

Blood ◽  
1987 ◽  
Vol 69 (2) ◽  
pp. 401-407 ◽  
Author(s):  
RS Schwartz ◽  
JA Olson ◽  
C Raventos-Suarez ◽  
M Yee ◽  
RH Heath ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Cell Membrane ◽  
Early Stage ◽  
Red Cells ◽  
Membrane Phospholipid ◽  
Cell Membrane Permeability ◽  
Parasite Development ◽  
Red Cell ◽  
Membrane Phospholipids ◽  
Red Cell Membrane

Abstract The intraerythrocytic development of the malaria parasite is accompanied by distinct morphological and biochemical changes in the host cell membrane, yet little is known about development-related alterations in the transbilayer organization of membrane phospholipids in parasitized cells. This question was examined in human red cells infected with Plasmodium falciparum. Normal red cells were infected with strain FCR3 or with clonal derivatives that either produce (K+) or do not produce (K-) knobby protuberances on the infected red cells. Parasitized cells were harvested at various stages of parasite development, and the bilayer orientation of red cell membrane phospholipids was determined chemically using 2,4,6-trinitrobenzene sulphonic acid (TNBS) or enzymatically using bee venom phospholipase A2 (PLA2) and sphingomyelinase C (SMC). We found that parasite development was accompanied by distinct alterations in the red cell membrane transbilayer distribution of phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylserine (PS). Increases in the exoplasmic membrane leaflet exposure of PE and PS were larger in the late-stage parasitized cells than in the early-stage parasitized cells. Similar results were obtained for PE membrane distribution using either chemical (TNBS) or enzymatic (PLA2 plus SMC) methods, although changes in PS distribution were observed only with TNBS. Uninfected cohort cells derived from mixed populations of infected and uninfected cells exhibited normal patterns of membrane phospholipid organization. The observed alterations in P falciparum-infected red cell membrane phospholipid distribution, which is independent of the presence or absence of knobby protuberances, might be associated with the drastic changes in cell membrane permeability and susceptibility to early hemolysis observed in the late stages of parasite development.

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