Secretion of Plasmodium falciparum rhoptry protein into the plasma membrane of host erythrocytes.

The rhoptry is an organelle of the malarial merozoite which has been suggested to play a role in parasite invasion of its host cell, the erythrocyte. A monoclonal antibody selected for reactivity with this organelle identifies a parasite synthesized protein of 110 kD. From biosynthetic labeling experiments it was demonstrated that the protein is synthesized midway through the erythrocytic cycle (the trophozoite stage) but immunofluorescence indicates the protein is not localized in the organelle until the final stage (segmenter stage) of intraerythrocytic development. Immunoelectron microscopy shows that the protein is localized in the matrix of the rhoptry organelle and on membranous whorls secreted from the merozoite. mAb recognition of the protein is dithiothreitol (DTT) labile, indicating that the conformation of the epitope is dependent on a disulfide linkage. During erythrocyte reinvasion by the extracellular merozoite, immunofluorescence shows the rhoptry protein discharging from the merozoite and spreading around the surface of the erythrocyte. The protein is located in the plasma membrane of the newly invaded erythrocyte. These studies suggest that the 110-kD rhoptry protein is inserted into the membrane of the host erythrocyte during merozoite invasion.

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Antimalarials increase vesicle pH in Plasmodium falciparum.

The Journal of Cell Biology ◽

10.1083/jcb.101.6.2302 ◽

1985 ◽

Vol 101 (6) ◽

pp. 2302-2309 ◽

Cited By ~ 166

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.

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Evidence that the Malaria Parasite Plasmodium falciparum Putative Rhoptry Protein 2 Localizes to the Golgi Apparatus throughout the Erythrocytic Cycle

PLoS ONE ◽

10.1371/journal.pone.0138626 ◽

2015 ◽

Vol 10 (9) ◽

pp. e0138626 ◽

Cited By ~ 8

Author(s):

Stéphanie Hallée ◽

Dave Richard

Keyword(s):

Plasmodium Falciparum ◽

Golgi Apparatus ◽

Malaria Parasite ◽

Parasite Plasmodium ◽

Parasite Plasmodium Falciparum ◽

Erythrocytic Cycle ◽

Rhoptry Protein

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

The Journal of Cell Biology ◽

10.1083/jcb.124.4.449 ◽

1994 ◽

Vol 124 (4) ◽

pp. 449-462 ◽

Cited By ~ 117

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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IgG4 Pf NPNA-1 a human anti-Plasmodium falciparum sporozoite monoclonal antibody cloned from a protected individual inhibits parasite invasion of hepatocytes

Human Antibodies ◽

10.3233/hab-2004-13305 ◽

2004 ◽

Vol 13 (3) ◽

pp. 91-96 ◽

Cited By ~ 8

Author(s):

Jonathan A. Chappel ◽

Michael R. Hollingdale ◽

Angray S. Kang

Keyword(s):

Monoclonal Antibody ◽

Plasmodium Falciparum ◽

Parasite Invasion ◽

Falciparum Sporozoite

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Secretion of a malarial histidine-rich protein (Pf HRP II) from Plasmodium falciparum-infected erythrocytes.

The Journal of Cell Biology ◽

10.1083/jcb.103.4.1269 ◽

1986 ◽

Vol 103 (4) ◽

pp. 1269-1277 ◽

Cited By ~ 192

Author(s):

R J Howard ◽

S Uni ◽

M Aikawa ◽

S B Aley ◽

J H Leech ◽

...

Keyword(s):

Monoclonal Antibody ◽

Plasmodium Falciparum ◽

Water Soluble ◽

Intracellular Growth ◽

Trophozoite Stage ◽

Cell Compartments ◽

Host Cell Cytoplasm ◽

Water Soluble Protein ◽

Major Species ◽

Low Levels

Plasmodium falciparum-infected erythrocytes (IRBCs) synthesize several histidine-rich proteins (HRPs) that accumulate high levels of [3H]histidine but very low levels of amino acids such as [3H]isoleucine or [35S]methionine. We prepared a monoclonal antibody which reacts specifically with one of these HRPs (Pf HRP II) and studied the location and synthesis of this protein during the parasite's intracellular growth. With the knob-positive Malayan Camp strain of P. falciparum, the monoclonal antibody identified a multiplet of protein bands with major species at Mr 72,000 and 69,000. Pf HRP II synthesis began with immature parasites (rings) and continued through the trophozoite stage. The Mr 72,000 band of Pf HRP II, but not the faster moving bands of the multiplet, was recovered as a water-soluble protein from the culture supernatant of intact IRBCs. Approximately 50% of the total [3H]histidine radioactivity incorporated into the Mr 72,000 band was extracellular between 2 and 24 h of culture. Immunofluorescence and cryothin-section immunoelectron microscopy localized Pf HRP II to several cell compartments including the parasite cytoplasm, as concentrated "packets" in the host erythrocyte cytoplasm and at the IRBC membrane. Our results provide evidence for an intracellular route of transport for a secreted malarial protein from the parasite through several membranes and the host cell cytoplasm.

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Heterogeneity of Size and Distribution of Intramembrane Particles in the Plasma Membrane of Yeast

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100080407 ◽

1977 ◽

Vol 35 ◽

pp. 596-597

Author(s):

E. Keyhani

Keyword(s):

Plasma Membrane ◽

Candida Utilis ◽

Synthetic Medium ◽

Freeze Fracture ◽

Translational Diffusion ◽

Yeast Cells ◽

Distilled Water ◽

Intramembrane Particles ◽

The Matrix ◽

Water Cell

The matrix of biological membranes consists of a lipid bilayer into which proteins or protein aggregates are intercalated. Freeze-fracture techni- ques permit these proteins, perhaps in association with lipids, to be visualized in the hydrophobic regions of the membrane. Thus, numerous intramembrane particles (IMP) have been found on the fracture faces of membranes from a wide variety of cells (1-3). A recognized property of IMP is their tendency to form aggregates in response to changes in experi- mental conditions (4,5), perhaps as a result of translational diffusion through the viscous plane of the membrane. The purpose of this communica- tion is to describe the distribution and size of IMP in the plasma membrane of yeast (Candida utilis).Yeast cells (ATCC 8205) were grown in synthetic medium (6), and then harvested after 16 hours of culture, and washed twice in distilled water. Cell pellets were suspended in growth medium supplemented with 30% glycerol and incubated for 30 minutes at 0°C, centrifuged, and prepared for freeze-fracture, as described earlier (2,3).

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COVID-19: Update on Pathogenesis and Treatment Strategies

Current Immunology Reviews ◽

10.2174/1573395516999201001154837 ◽

2020 ◽

Vol 16 (1) ◽

pp. 1-5

Author(s):

Rakesh K. Chauhan ◽

Pramod K. Sharma ◽

Shikha Srivastava

Keyword(s):

Monoclonal Antibody ◽

Plasma Membrane ◽

Human Monoclonal Antibody ◽

Cardiac Injury ◽

Treatment Strategies ◽

Severe Pneumonia ◽

Ground Glass Opacity ◽

Golgi Membrane ◽

Virus Particles ◽

Global Pandemic

COVID-19 (Coronavirus disease) is the most contagious virus, which has been characterized as a global pandemic by WHO. The pathological cycle of COVID-19 virus can be specified as RNAaemia, severe pneumonia, along with the Ground-glass opacity (GGO), and acute cardiac injury. The S protein of Coronavirus has been reported to be involved in the entry of the virus into the host cell, which can be accomplished by direct membrane fusion between the virus and plasma membrane. In the endoplasmic reticulum or Golgi membrane, the newly formed enveloped glycoproteins are introduced. The spread of disease occurs due to contact and droplets unleashed by the vesicles holding the virus particles combined with the plasma membrane to the virus released by the host. The present manuscript describes the pathogenesis of COVID-19 and various treatment strategies that include drugs such as chloroquine and hydroxychloroquine, an anti-malarial drug, antibodies: SARS-CoV-specific human monoclonal antibody CR3022 and plasma treatment facilitate the therapeutic effect.

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