scholarly journals Exploring inhibition of Pdx1, a component of the PLP synthase complex of the human malaria parasite Plasmodium falciparum

2012 ◽  
Vol 449 (1) ◽  
pp. 175-187 ◽  
Author(s):  
Shaun B. Reeksting ◽  
Ingrid B. Müller ◽  
Pieter B. Burger ◽  
Emmanuel S. Burgos ◽  
Laurent Salmon ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Reaction Mechanism ◽  
Aldehyde Group ◽  
Dependent Manner ◽  
Transgenic Cell ◽  
Ic50 Value ◽  
Parasite Plasmodium ◽  
Parasite Plasmodium Falciparum ◽  
Imine Bond

Malaria tropica is a devastating infectious disease caused by Plasmodium falciparum. This parasite synthesizes vitamin B6de novo via the PLP (pyridoxal 5′-phosphate) synthase enzymatic complex consisting of PfPdx1 and PfPdx2 proteins. Biosynthesis of PLP is largely performed by PfPdx1, ammonia provided by PfPdx2 subunits is condensed together with R5P (D-ribose 5-phosphate) and G3P (DL-glyceraldehyde 3-phosphate). PfPdx1 accommodates both the R5P and G3P substrates and intricately co-ordinates the reaction mechanism, which is composed of a series of imine bond formations, leading to the production of PLP. We demonstrate that E4P (D-erythrose 4-phosphate) inhibits PfPdx1 in a dose-dependent manner. We propose that the acyclic phospho-sugar E4P, with a C1 aldehyde group similar to acyclic R5P, could interfere with R5P imine bond formations in the PfPdx1 reaction mechanism. Molecular docking and subsequent screening identified the E4P hydrazide analogue 4PEHz (4-phospho-D-erythronhydrazide), which selectively inhibited PfPdx1 with an IC50 of 43 μM. PfPdx1 contained in the heteromeric PLP synthase complex was shown to be more sensitive to 4PEHz and was inhibited with an IC50 of 16 μM. Moreover, the compound had an IC50 value of 10 μM against cultured P. falciparum intraerythrocytic parasites. To analyse further the selectivity of 4PEHz, transgenic cell lines overexpressing PfPdx1 and PfPdx2 showed that additional copies of the protein complex conferred protection against 4PEHz, indicating that the PLP synthase is directly affected by 4PEHz in vivo. These PfPdx1 inhibitors represent novel lead scaffolds which are capable of targeting PLP biosynthesis, and we propose this as a viable strategy for the development of new therapeutics against malaria.

scholarly journals PfPDE1, a novel cGMP-specific phosphodiesterase from the human malaria parasite Plasmodium falciparum

2005 ◽  
Vol 392 (1) ◽  
pp. 221-229 ◽  
Author(s):  
Keizo Yuasa ◽  
Fumika Mi-Ichi ◽  
Tamaki Kobayashi ◽  
Masaya Yamanouchi ◽  
Jun Kotera ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Cyclic Nucleotide ◽  
Malaria Parasite ◽  
Catalytic Domain ◽  
Hydrolytic Activity ◽  
Human Malaria Parasite ◽  
Pde Inhibitors ◽  
Ic50 Value ◽  
Parasite Plasmodium ◽  
Parasite Plasmodium Falciparum

This is the first report of molecular characterization of a novel cyclic nucleotide PDE (phosphodiesterase), isolated from the human malaria parasite Plasmodium falciparum and designated PfPDE1. PfPDE1 cDNA encodes an 884-amino-acid protein, including six putative transmembrane domains in the N-terminus followed by a catalytic domain. The PfPDE1 gene is a single-copy gene consisting of two exons and a 170 bp intron. PfPDE1 transcripts were abundant in the ring form of the asexual blood stages of the parasite. The C-terminal catalytic domain of PfPDE1, produced in Escherichia coli, specifically hydrolysed cGMP with a Km value of 0.65 μM. Among the PDE inhibitors tested, a PDE5 inhibitor, zaprinast, was the most effective, having an IC50 value of 3.8 μM. The non-specific PDE inhibitors IBMX (3-isobutyl-1-methylxanthine), theophylline and the antimalarial chloroquine had IC50 values of over 100 μM. Membrane fractions prepared from P. falciparum at mixed asexual blood stages showed potent cGMP hydrolytic activity compared with cytosolic fractions. This hydrolytic activity was sensitive to zaprinast with an IC50 value of 4.1 μM, but insensitive to IBMX and theophylline. Furthermore, an in vitro antimalarial activity assay demonstrated that zaprinast inhibited the growth of the asexual blood parasites, with an ED50 value of 35 μM. The impact of cyclic nucleotide signalling on the cellular development of this parasite has previously been discussed. Thus this enzyme is suggested to be a novel potential target for the treatment of the disease malaria.

scholarly journals Antisense long noncoding RNAs regulate var gene activation in the malaria parasite Plasmodium falciparum

2015 ◽  
Vol 112 (9) ◽  
pp. E982-E991 ◽  
Author(s):  
Inbar Amit-Avraham ◽  
Guy Pozner ◽  
Shiri Eshar ◽  
Yair Fastman ◽  
Netanel Kolevzon ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Antigenic Variation ◽  
Single Gene ◽  
Gene Activation ◽  
Noncoding Rnas ◽  
Long Noncoding Rnas ◽  
Dependent Manner ◽  
Parasite Plasmodium ◽  
Parasite Plasmodium Falciparum ◽  
Antisense Lncrnas

The virulence of Plasmodium falciparum, the causative agent of the deadliest form of human malaria, is attributed to its ability to evade human immunity through antigenic variation. These parasites alternate between expression of variable antigens, encoded by members of a multicopy gene family named var. Immune evasion through antigenic variation depends on tight regulation of var gene expression, ensuring that only a single var gene is expressed at a time while the rest of the family is maintained transcriptionally silent. Understanding how a single gene is chosen for activation is critical for understanding mutually exclusive expression but remains a mystery. Here, we show that antisense long noncoding RNAs (lncRNAs) initiating from var introns are associated with the single active var gene at the time in the cell cycle when the single var upstream promoter is active. We demonstrate that these antisense transcripts are incorporated into chromatin, and that expression of these antisense lncRNAs in trans triggers activation of a silent var gene in a sequence- and dose-dependent manner. On the other hand, interference with these lncRNAs using complement peptide nucleic acid molecules down-regulated the active var gene, erased the epigenetic memory, and induced expression switching. Altogether, our data provide evidence that these antisense lncRNAs play a key role in regulating var gene activation and mutually exclusive expression.

scholarly journals The in vivo RNA structurome of the malaria parasite Plasmodium falciparum, a protozoan with an A/T-rich transcriptome

2021 ◽  
Author(s):  
F Dumetz ◽  
AJ Enright ◽  
J Zhao ◽  
CK Kwok ◽  
CJ Merrick
Keyword(s):  
Plasmodium Falciparum ◽  
Protozoan Parasite ◽  
Structural Features ◽  
Translation Efficiency ◽  
Rna Molecules ◽  
Transcript Stability ◽  
Parasite Plasmodium ◽  
Parasite Plasmodium Falciparum ◽  
Transcriptomic Level

AbstractPlasmodium falciparum, a protozoan parasite and causative agent of human malaria, has one of the most A/T-biased genomes sequenced to date. This may give the genome and the transcriptome unusual structural features. Recent progress in sequencing techniques has made it possible to study the secondary structures of RNA molecules at the transcriptomic level. Accordingly, in this study we produced the first in vivo RNA structurome of a protozoan parasite, and the first of a highly A/U-biased transcriptome. We showed that it is possible to probe the secondary structure of P. falciparum RNA molecules in vivo using two different chemical probes, and obtained structures for more than half of all transcripts in the transcriptome. These showed greater stability (lower free energy) than the same structures modelled in silico, and structural features appeared to influence translation efficiency and RNA decay. Finally, we compared the P. falciparum RNA structurome with the predicted RNA structurome of an A/T-balanced species, P. knowlesi, finding a bias towards lower overall transcript stability and more hairpins and multi-stem loops in P. falciparum. This first protozoan RNA structurome will provide a basis for similar studies in other protozoans and also in other unusual genomes.

scholarly journals Artemisinin susceptibility in the malaria parasite Plasmodium falciparum: propellers, adaptor proteins and the need for cellular healing

2020 ◽  
Author(s):  
Colin J Sutherland ◽  
Ryan C Henrici ◽  
Katerina Artavanis-Tsakonas
Keyword(s):  
Plasmodium Falciparum ◽  
Artemisinin Resistance ◽  
Adaptor Proteins ◽  
Mutant Form ◽  
New Synthesis ◽  
Parasite Plasmodium ◽  
Parasite Plasmodium Falciparum ◽  
Complex Picture

ABSTRACT Studies of the susceptibility of Plasmodium falciparum to the artemisinin family of antimalarial drugs provide a complex picture of partial resistance (tolerance) associated with increased parasite survival in vitro and in vivo. We present an overview of the genetic loci that, in mutant form, can independently elicit parasite tolerance. These encode Kelch propeller domain protein PfK13, ubiquitin hydrolase UBP-1, actin filament-organising protein Coronin, also carrying a propeller domain, and the trafficking adaptor subunit AP-2μ. Detailed studies of these proteins and the functional basis of artemisinin tolerance in blood-stage parasites are enabling a new synthesis of our understanding to date. To guide further experimental work, we present two major conclusions. First, we propose a dual-component model of artemisinin tolerance in P. falciparum comprising suppression of artemisinin activation in early ring stage by reducing endocytic haemoglobin capture from host cytosol, coupled with enhancement of cellular healing mechanisms in surviving cells. Second, these two independent requirements limit the likelihood of development of complete artemisinin resistance by P. falciparum, favouring deployment of existing drugs in new schedules designed to exploit these biological limits, thus extending the useful life of current combination therapies.

scholarly journals Can malaria protein fight cancer?

2018 ◽  
Vol 8 (2) ◽  
pp. 181-193
Author(s):  
Fathia Abd Elwahid Mannaa
Keyword(s):  
Plasmodium Falciparum ◽  
Chondroitin Sulfate ◽  
Diphtheria Toxin ◽  
Malaria Parasite ◽  
The Body ◽  
Tumor Cell Growth ◽  
Successful Recovery ◽  
Parasite Plasmodium ◽  
Parasite Plasmodium Falciparum

Cancer risk depends on a combination of our genes, environment and other aspects of our lives, many of which we can control. Surgery, radiation and chemotherapy are often effective at treating people with a solid tumor, but once the cancer has spread and formed tiny tumors at distant sites, chances for a successful recovery are dismal.Recently, it was discovered that the malaria parasite, Plasmodium falciparum produce and present a malarial protein called VAR2CSA, which bind a type of sugar molecule exclusively found in the placenta. It was found that the exact same sugar molecule structure is also found in most cancer cells. Both molecules are a type of chondroitin sulfate. The VAR2CSA only adhere in the placenta and do not bind to chondroitin sulfate expressed elsewhere in the body. In tumors, placental-like chondroitin sulfate chains are linked to a limited repertoire of cancer-associated proteoglycans including CD44 and CSPG4. The recombinant VAR2CSA (rVAR2) protein localizes to tumors in vivo and rVAR2 fused to diphtheria toxin or conjugated to hemiasterlin compounds strongly inhibits in vivo tumor cell growth and metastasis.

scholarly journals Differential Stimulation of the Na+/H+ Exchanger Determines Chloroquine Uptake in Plasmodium falciparum

1998 ◽  
Vol 140 (2) ◽  
pp. 335-345 ◽  
Author(s):  
Stefan Wünsch ◽  
Cecilia P. Sanchez ◽  
Michael Gekle ◽  
Lars Große-Wortmann ◽  
Jochen Wiesner ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Malarial Parasite ◽  
Physiological Data ◽  
Ph Measurements ◽  
Parasite Plasmodium ◽  
Parasite Plasmodium Falciparum ◽  
Transitory Phase ◽  
Identification And Characterization

Here we describe the identification and characterization of a physiological marker that is associated with the chloroquine-resistant (CQR) phenotype in the human malarial parasite Plasmodium falciparum. Single cell in vivo pH measurements revealed that CQR parasites consistently have an elevated cytoplasmic pH compared to that of chloroquine-sensitive (CQS) parasites because of a constitutively activated Na+/H+ exchanger (NHE). Together, biochemical and physiological data suggest that chloroquine activates the plasmodial NHE of CQS parasites, resulting in a transitory phase of rapid sodium/hydrogen ion exchange during which chloroquine is taken up by this protein. The constitutively stimulated NHE of CQR parasites are capable of little or no further activation by chloroquine. We propose that the inability of chloroquine to stimulate its own uptake through the constitutively activated NHE of resistant parasites constitutes a minimal and necessary event in the generation of the chloroquine-resistant phenotype.

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