scholarly journals Increased permeability to choline in simian erythrocytes after Plasmodium knowlesi infection

1991 ◽  
Vol 273 (3) ◽  
pp. 701-709 ◽  
Author(s):  
M L Ancelin ◽  
M Parant ◽  
M J Thuet ◽  
J R Philippot ◽  
H J Vial
Keyword(s):  
De Novo ◽  
Plasmodium Knowlesi ◽  
Maximum Velocity ◽  
Atp Depletion ◽  
Facilitated Diffusion ◽  
High Increase ◽  
Choline Transport ◽  
Parasite Plasmodium ◽  
Thiol Reagent ◽  
Infected Cells

The permeability of simian erythrocytes to choline was found to be considerably increased after infection by the malaria parasite, Plasmodium knowlesi. Choline entry occurs by a facilitated-diffusion system involving a carrier, which displays temperature-dependence, saturability with choline (Km = 8.5 +/- 0.7 microM) and specificity. This carrier can also be inhibited by a thiol reagent, N-ethylmaleimide, at an inactivation rate which is, in the absence of choline, the same as in normal erythrocytes. Inactivation by N-ethylmaleimide can be accelerated by external choline and prevented by decamethonium, which acts as an inhibitor of choline entry in infected cells (as with dodecyltrimethylammonium). Both ethanolamine and imidazole act as inhibitors or activators of choline entry in infected erythrocytes, depending on the relative concentrations of choline and of the competing compound (i.e. ethanolamine or imidazole). After infection, the maximum velocity reached 2.84 +/- 0.5 nmol/min per 10(10) infected cells, which is more than 10 times the Vmax. of normal erythrocytes. Impairing the biosynthesis of phosphatidylcholine de novo in Plasmodium-infected erythrocytes by various methods (glucose or ATP depletion, high ethanolamine concentrations) did not result in any alteration of choline transport (Km or Vmax.), indicating that the constant triggering and transformation of choline into phosphatidylcholine by the parasite is not directly responsible for the increase in the choline transport rate after infection. This high increase in choline transport activity is more likely related to modifications in choline carriers and/or in their environment after Plasmodium infection.

scholarly journals An intracellular simian malarial parasite (Plasmodium knowlesi) induces stage-dependent alterations in membrane phospholipid organization of its host erythrocyte

1987 ◽  
Vol 246 (1) ◽  
pp. 103-108 ◽  
Author(s):  
P Joshi ◽  
G P Dutta ◽  
C M Gupta
Keyword(s):  
Developmental Stages ◽  
Plasmodium Knowlesi ◽  
Membrane Phospholipid ◽  
Malarial Parasite ◽  
Merocyanine 540 ◽  
Parasite Plasmodium ◽  
Normal Monkey ◽  
Infected Cells ◽  
Membrane Isolation ◽  
Different Sources

The membrane phospholipid organization in monkey erythrocytes harbouring different developmental stages of the simian malarial parasite Plasmodium knowlesi was studied using phospholipase A2 from two different sources and Merocyanine 540 as the external-membrane probes. Experiments were done to confirm that the phospholipases did not penetrate into the infected cells or hydrolyse phospholipids during membrane isolation. The parasite-free erythrocyte membrane was isolated by differential centrifugation or by using the cationic beads Affi-Gel 731. The purity of the membranes was established by optical and electron microscopy, and by assaying the parasite-specific enzyme glutamate dehydrogenase. About 10% of the phosphatidylethanolamine and none of phosphatidylserine were hydrolysed by the phospholipases in intact normal monkey erythrocytes. However, accessibility of these aminophospholipids to the enzymes was significantly enhanced in the infected cells under identical conditions. The degree of this enhancement depended on the developmental stage of the intracellular parasite, but not on the parasitaemia levels in the infected monkeys, and increased with the parasite growth inside the cells. Analogously, Merocyanine 540 was found to label the trophozoite- or schizont-infected erythrocytes, but not the ring-infected or normal cells. These results demonstrate that the intracellular malarial parasite produces stage-dependent alterations in the membrane phospholipid organization of its host erythrocyte.

scholarly journals Enhanced choline and Rb+ transport in human erythrocytes infected with the malaria parasite Plasmodium falciparum

1991 ◽  
Vol 278 (2) ◽  
pp. 521-525 ◽  
Author(s):  
K Kirk ◽  
H Y Wong ◽  
B C Elford ◽  
C I Newbold ◽  
J C Ellory
Keyword(s):  
Plasmodium Falciparum ◽  
Malaria Parasite ◽  
Human Erythrocytes ◽  
Transport Pathway ◽  
Choline Transport ◽  
Transport Component ◽  
Parasite Plasmodium ◽  
Parasite Plasmodium Falciparum ◽  
Infected Cells

Human erythrocytes infected in vitro with the malaria parasite Plasmodium falciparum showed a markedly increased rate of choline influx compared with normal cells. Choline transport into uninfected cells (cultured in parallel with infected cells) obeyed Michaelis-Menten kinetics (Km approximately 11 microM). In malaria-parasite-infected cells there was an additional choline-transport component which failed to saturate at extracellular concentrations of up to 500 microM. This component was less sensitive than the endogenous transporter to inhibition by the Cinchona bark alkaloids quinine, quinidine, cinchonine and cinchonidine, but showed a much greater sensitivity than the native system to inhibition by piperine. The sensitivity of the induced choline transport to these reagents was similar to that of the malaria-induced (ouabain- and bumetanide-resistant) Rb(+)-transport pathway; however, the relative magnitudes of the piperine-sensitive choline and Rb+ fluxes in malaria-parasite-infected cells varied between cultures. This suggests either that the enhanced transport of the two cations was via functionally distinct (albeit pharmacologically similar) pathways, or that the transport was mediated by a pathway with variable substrate selectivity.

scholarly journals Localization of ferrochelatase in Plasmodium falciparum

2004 ◽  
Vol 384 (2) ◽  
pp. 429-436 ◽  
Author(s):  
Sundaramurthy VARADHARAJAN ◽  
B. K. Chandrashekar SAGAR ◽  
Pundi N. RANGARAJAN ◽  
Govindarajan PADMANABAN
Keyword(s):  
Plasmodium Falciparum ◽  
De Novo ◽  
Enzymic Activity ◽  
Malarial Parasite ◽  
Parasite Genome ◽  
Marker Proteins ◽  
Parasite Plasmodium ◽  
Theoretical Predictions ◽  
Parasite Plasmodium Falciparum

Our previous studies have demonstrated de novo haem biosynthesis in the malarial parasite (Plasmodium falciparum and P. berghei). It has also been shown that the first enzyme of the pathway is the parasite genome-coded ALA (δ-aminolaevulinate) synthase localized in the parasite mitochondrion, whereas the second enzyme, ALAD (ALA dehydratase), is accounted for by two species: one species imported from the host red blood cell into the parasite cytosol and another parasite genome-coded species in the apicoplast. In the present study, specific antibodies have been raised to PfFC (parasite genome-coded ferrochelatase), the terminal enzyme of the haem-biosynthetic pathway, using recombinant truncated protein. With the use of these antibodies as well as those against the hFC (host red cell ferrochelatase) and other marker proteins, immunofluorescence studies were performed. The results reveal that P. falciparum in culture manifests a broad distribution of hFC and a localized distribution of PfFC in the parasite. However, PfFC is not localized to the parasite mitochondrion. Immunoelectron-microscopy studies reveal that PfFC is indeed localized to the apicoplast, whereas hFC is distributed in the parasite cytoplasm. These results on the localization of PfFC are unexpected and are at variance with theoretical predictions based on leader sequence analysis. Biochemical studies using the parasite cytosolic and organellar fractions reveal that the cytosol containing hFC accounts for 80% of FC enzymic activity, whereas the organellar fraction containing PfFC accounts for the remaining 20%. Interestingly, both the isolated cytosolic and organellar fractions are capable of independent haem synthesis in vitro from [4-14C]ALA, with the cytosol being three times more efficient compared with the organellar fraction. With [2-14C]glycine, most of the haem is synthesized in the organellar fraction. Thus haem is synthesized in two independent compartments: in the cytosol, using the imported host enzymes, and in the organellar fractions, using the parasite genome-coded enzymes.

Nuclear and mitochondrial DNA of the primate malarial parasite Plasmodium knowlesi

1985 ◽  
Vol 14 (2) ◽  
pp. 199-209 ◽  
Author(s):  
Donald H. Williamson ◽  
Robert J.M. Wilson ◽  
Paul A. Bates ◽  
Shirley McCready ◽  
Francine Perler ◽  
...  
Keyword(s):  
Mitochondrial Dna ◽  
Plasmodium Knowlesi ◽  
Malarial Parasite ◽  
Parasite Plasmodium

scholarly journals Novel vectors of the zoonotic malaria parasite, Plasmodium knowlesi, in two districts of Sarawak, Malaysian Borneo

2018 ◽  
Vol 73 ◽  
pp. 75
Author(s):  
J. Ang Xin De ◽  
K. Abdul Kadir ◽  
D.S. Awang Mohamad ◽  
A. Matusop ◽  
K. Yaman ◽  
...  
Keyword(s):  
Malaria Parasite ◽  
Plasmodium Knowlesi ◽  
Zoonotic Malaria ◽  
Parasite Plasmodium ◽  
Malaysian Borneo

scholarly journals ATP-dependent release of glucocorticoid receptors from the nuclear matrix.

1996 ◽  
Vol 16 (5) ◽  
pp. 1989-2001 ◽  
Author(s):  
Y Tang ◽  
D B DeFranco
Keyword(s):  
Nuclear Receptors ◽  
Nuclear Matrix ◽  
Nuclear Export ◽  
Glucocorticoid Receptors ◽  
De Novo ◽  
Steroid Receptors ◽  
Simian Virus 40 ◽  
Atp Depletion ◽  
Nuclear Proteins ◽  
The Matrix

Glucocorticoid receptors (GRs) have the capacity to shuttle between the nuclear and cytoplasmic compartments, sharing that trait with other steroid receptors and unrelated nuclear proteins of diverse function. Although nuclear import of steroid receptors, like that of nearly all other karyophilic proteins examined to date, requires ATP, there appear to be different energetic requirements for export of proteins, including steroid receptors, from nuclei. In an attempt to reveal which steps, if any, in the nuclear export pathway utilized by steroid receptors require ATP, we have used indirect immunofluorescence to visualize GRs within cells subjected to a reversible ATP depletion. Under conditions which lead to >95% depletion of cellular ATP levels within 90 min, GRs remain localized within nuclei and do not efflux into the cytoplasm. Under analogous conditions of ATP depletion, transfected progesterone receptors are also retained within nuclei. Importantly, GRs which accumulate within nuclei of ATP-depleted cells are distinguished from nuclear receptors in metabolically active cells by their resistance to in situ extraction with a hypotonic, detergent-containing buffer. GRs in ATP-depleted cells are not permanently trapped in this nuclear compartment, as nuclear receptors rapidly regain their capacity to be extracted upon restoration of cellular ATP, even in the absence of de novo protein synthesis. More extensive extraction of cells with high salt and detergent, coupled with DNase I digestion, established that a significant fraction of GRs in ATP-depleted cells are associated with an RNA-containing nuclear matrix. Quantitative Western blot (immunoblot) analysis confirmed the dramatic increase in GR binding to the nuclear matrix of ATP-depleted cells, while confocal microscopy revealed that GRs are bound to the matrix throughout all planes of the nucleus. ATP depletion does not lead to wholesale collapse of nuclear proteins onto the matrix, as the interaction of a subpopulation of simian virus 40 large tumor antigen with the nuclear matrix is not quantitatively altered in ATP-depleted Cos-1 cells. Nuclear GRs which are not bound to the nuclear matrix of metabolically active cells (i.e., a DNA-binding domain deletion mutant and a beta-galactosidase chimera possessing the GR nuclear localization signal sequence) are not recruited to the matrix upon depletion of cellular ATP. Thus, it appears that ATP depletion does not expose the GR to nuclear matrix interactions which are not normally encountered in cells but merely alters the dynamics of such interactions. The dynamic association of steroid receptors with the nuclear matrix may provide a mechanism which is utilized by these regulable transcription factors to facilitate their efficient scanning of the genome.

scholarly journals Trehalose recycling promotes energy-efficient mycomembrane reorganization in nutrient-limited mycobacteria

2019 ◽  
Author(s):  
Amol Arunrao Pohane ◽  
Caleb R. Carr ◽  
Jaishree Garhyan ◽  
Benjamin M. Swarts ◽  
M. Sloan Siegrist
Keyword(s):  
Energy Efficient ◽  
De Novo ◽  
Cell Envelope ◽  
Bacterial Pathogens ◽  
Atp Depletion ◽  
Redox Stress ◽  
Mycobacterial Cell ◽  
Resource Limited ◽  
Trehalose Synthesis ◽  
Long Chain

AbstractThe mycomembrane layer of the mycobacterial cell envelope is a barrier to environmental, immune and antibiotic insults. We find that there is mycomembrane remodeling along the periphery of nutrient-starved, non-replicating mycobacterial cells. Remodeling is supported by recycling of trehalose, a non-mammalian disaccharide that shuttles long-chain mycolate lipids to the mycomembrane. In the absence of trehalose recycling, mycomembrane synthesis continues but mycobacteria experience ATP depletion, enhanced respiration and redox stress. Redox stress from depletion of the trehalose pool is suppressed in a mutant that lacks the OtsAB de novo trehalose synthesis pathway. Our data suggest that trehalose recycling alleviates the energetic burden of mycomembrane remodeling. Loss of trehalose salvage is known to attenuate M. tuberculosis during infection and render the bacterium more susceptible to a variety of drugs. Recycling pathways are emerging targets for sensitizing resource-limited bacterial pathogens to host and antibiotic stress.

scholarly journals Overexpression of quality control proteins reduces prion conversion in prion-infected cells

2018 ◽  
Vol 293 (41) ◽  
pp. 16069-16082 ◽  
Author(s):  
Simrika Thapa ◽  
Basant Abdulrahman ◽  
Dalia H. Abdelaziz ◽  
Li Lu ◽  
Manel Ben Aissa ◽  
...  
Keyword(s):  
Quality Control ◽  
De Novo ◽  
Prion Diseases ◽  
Neuroblastoma Cells ◽  
Cellular Prion Protein ◽  
Control Mechanisms ◽  
Cellular Mechanisms ◽  
Prion Propagation ◽  
Infected Cells

Prion diseases are fatal infectious neurodegenerative disorders in humans and other animals and are caused by misfolding of the cellular prion protein (PrPC) into the pathological isoform PrPSc. These diseases have the potential to transmit within or between species, including zoonotic transmission to humans. Elucidating the molecular and cellular mechanisms underlying prion propagation and transmission is therefore critical for developing molecular strategies for disease intervention. We have shown previously that impaired quality control mechanisms directly influence prion propagation. In this study, we manipulated cellular quality control pathways in vitro by stably and transiently overexpressing selected quality control folding (ERp57) and cargo (VIP36) proteins and investigated the effects of this overexpression on prion propagation. We found that ERp57 or VIP36 overexpression in persistently prion-infected neuroblastoma cells significantly reduces the amount of PrPSc in immunoblots and prion-seeding activity in the real-time quaking-induced conversion (RT-QuIC) assay. Using different cell lines infected with various prion strains confirmed that this effect is not cell type– or prion strain–specific. Moreover, de novo prion infection revealed that the overexpression significantly reduced newly formed PrPSc in acutely infected cells. ERp57-overexpressing cells significantly overcame endoplasmic reticulum stress, as revealed by expression of lower levels of the stress markers BiP and CHOP, accompanied by a decrease in PrP aggregates. Furthermore, application of ERp57-expressing lentiviruses prolonged the survival of prion-infected mice. Taken together, improved cellular quality control via ERp57 or VIP36 overexpression impairs prion propagation and could be utilized as a potential therapeutic strategy.

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