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The Journal of Biological Chemistry Jun 2022The receptor for activated C-kinase 1 (RACK1), a highly conserved eukaryotic protein, is known to have many varying biological roles and functions. Previous work has...
The receptor for activated C-kinase 1 (RACK1), a highly conserved eukaryotic protein, is known to have many varying biological roles and functions. Previous work has established RACK1 as a ribosomal protein, with defined regions important for ribosome binding in eukaryotic cells. In Plasmodium falciparum, RACK1 has been shown to be required for parasite growth, however, conflicting evidence has been presented about RACK1 ribosome binding and its role in mRNA translation. Given the importance of RACK1 as a regulatory component of mRNA translation and ribosome quality control, the case could be made in parasites that RACK1 either binds or does not bind the ribosome. Here, we used bioinformatics and transcription analyses to further characterize the P. falciparum RACK1 protein. Based on homology modeling and structural analyses, we generated a model of P. falciparum RACK1. We then explored mutant and chimeric human and P. falciparum RACK1 protein binding properties to the human and P. falciparum ribosome. We found that WT, chimeric, and mutant RACK1 exhibit distinct ribosome interactions suggesting different binding characteristics for P. falciparum and human RACK1 proteins. The ribosomal binding of RACK1 variants in human and parasite cells shown here demonstrates that although RACK1 proteins have highly conserved sequences and structures across species, ribosomal binding is affected by species-specific alterations to this protein. In conclusion, we show that in the case of P. falciparum, contrary to the structural data, RACK1 is found to bind ribosomes and actively translating polysomes in parasite cells.
Topics: Humans; Plasmodium falciparum; Protein Biosynthesis; Receptors for Activated C Kinase; Ribosomal Proteins; Ribosomes
PubMed: 35452681
DOI: 10.1016/j.jbc.2022.101954 -
Molecular Microbiology Jul 2015The pathogenicity of Plasmodium falciparum is partly due to parasite-induced host cell modifications. These modifications are facilitated by exported P. falciparum...
The pathogenicity of Plasmodium falciparum is partly due to parasite-induced host cell modifications. These modifications are facilitated by exported P. falciparum proteins, collectively referred to as the exportome. Export of several hundred proteins is mediated by the PEXEL/HT, a protease cleavage site. The PEXEL/HT is usually comprised of five amino acids, of which R at position 1, L at position 3 and E, D or Q at position 5 are conserved and important for export. Non-canonical PEXEL/HTs with K or H at position 1 and/or I at position 3 are presently considered non-functional. Here, we show that non-canonical PEXEL/HT proteins are overrepresented in P. falciparum and other Plasmodium species. Furthermore, we show that non-canonical PEXEL/HTs can be cleaved and can promote export in both a REX3 and a GBP reporter, but not in a KAHRP reporter, indicating that non-canonical PEXEL/HTs are functional in concert with a supportive sequence environment. We then selected P. falciparum proteins with a non-canonical PEXEL/HT and show that some of these proteins are exported and that their export depends on non-canonical PEXEL/HTs. We conclude that PEXEL/HT plasticity is higher than appreciated and that non-canonical PEXEL/HT proteins cannot categorically be excluded from Plasmodium exportome predictions.
Topics: Amino Acid Motifs; Host-Parasite Interactions; Peptide Hydrolases; Plasmodium falciparum; Protein Processing, Post-Translational; Protein Transport; Protozoan Proteins
PubMed: 25850860
DOI: 10.1111/mmi.13024 -
Current Opinion in Microbiology Aug 2014The eukaryotic unicellular pathogen Plasmodium falciparum tightly regulates gene expression, both during development and in adaptation to dynamic host environments. This... (Review)
Review
The eukaryotic unicellular pathogen Plasmodium falciparum tightly regulates gene expression, both during development and in adaptation to dynamic host environments. This regulation is evident in the mutually exclusive expression of members of clonally variant virulence multigene families. While epigenetic regulators have been selectively identified at active or repressed virulence genes, their specific recruitment remains a mystery. In recent years, noncoding RNAs (ncRNAs) have emerged as lynchpins of eukaryotic gene regulation; by binding to epigenetic regulators, they provide target specificity to otherwise non-specific enzyme complexes. Not surprisingly, there is great interest in understanding the role of ncRNA in P. falciparum, in particular, their contribution to the mutually exclusive expression of virulence genes. The current repertoire of P. falciparum ncRNAs includes, but is not limited to, subtelomeric ncRNAs, virulence gene-associated ncRNAs and natural antisense RNA transcripts. Continued improvement in high-throughput sequencing methods is sure to expand this repertoire. Here, we summarize recent advances in P. falciparum ncRNA biology, with an emphasis on ncRNA-mediated epigenetic modes of gene regulation.
Topics: Adaptation, Physiological; Epigenesis, Genetic; Gene Expression Regulation; Plasmodium falciparum; RNA, Untranslated; Virulence Factors
PubMed: 25022240
DOI: 10.1016/j.mib.2014.06.013 -
Biochimica Et Biophysica Acta Jul 2016Plasmodium has a complex biology including the ability to interact with host signals modulating their function through cellular machinery. Tumor necrosis factor (TNF)...
BACKGROUND
Plasmodium has a complex biology including the ability to interact with host signals modulating their function through cellular machinery. Tumor necrosis factor (TNF) elicits diverse cellular responses including effects in malarial pathology and increased infected erythrocyte cytoadherence. As TNF levels are raised during Plasmodium falciparum infection we have investigated whether it has an effect on the parasite asexual stage.
METHODS
Flow cytometry, spectrofluorimetric determinations, confocal microscopy and PCR real time quantifications were employed for characterizing TNF induced effects and membrane integrity verified by wheat germ agglutinin staining.
RESULTS
TNF is able to decrease intracellular parasitemia, involving calcium as a second messenger of the pathway. Parasites incubated for 48 h with TNF showed reduced erythrocyte invasion. Thus, TNF induced rises in intracellular calcium concentration, which were blocked by prior addition of the purinergic receptor agonists KN62 and A438079, or interfering with intra- or extracellular calcium release by thapsigargin or EGTA (ethylene glycol tetraacetic acid). Importantly, expression of PfPCNA1 which encodes the Plasmodium falciparum Proliferating-Cell Nuclear Antigen 1, decreased after P. falciparum treatment of TNF (tumor necrosis factor) or 6-Bnz cAMP (N(6)-benzoyladenosine-3',5'-cyclic monophosphate sodium salt).
CONCLUSIONS
This is potentially interesting data showing the relevance of calcium in downregulating a gene involved in cellular proliferation, triggered by TNF.
GENERAL SIGNIFICANCE
The data show that Plasmodium may subvert the immunological system and use TNF for the control of its proliferation within the vertebrate host.
Topics: Antimalarials; Calcium Signaling; Cell Adhesion; Cells, Cultured; Dose-Response Relationship, Drug; Endothelial Cells; Erythrocytes; Host-Parasite Interactions; Humans; Plasmodium falciparum; Proliferating Cell Nuclear Antigen; Protozoan Proteins; Time Factors; Tumor Necrosis Factor-alpha
PubMed: 27080559
DOI: 10.1016/j.bbagen.2016.04.003 -
The FEBS Journal Aug 2017Understanding the dynamic behaviour of the Plasmodium falciparum metabolism during infection can help identify targets for drug development. In this Commentary, we...
Understanding the dynamic behaviour of the Plasmodium falciparum metabolism during infection can help identify targets for drug development. In this Commentary, we highlight recently published studies in The FEBS Journal that cover mathematical modelling of glycolysis in P. falciparum and the identification and in vivo validation of metabolic drug targets.
Topics: Antimalarials; Glycolysis; Humans; Malaria; Models, Theoretical; Plasmodium falciparum
PubMed: 28834340
DOI: 10.1111/febs.14161 -
Science Progress 2002Every year there are 270 million clinical attacks of malaria and 2 million deaths, caused by the protozoan Plasmodium falciparum. Most of these cases occur in Africa.... (Review)
Review
Every year there are 270 million clinical attacks of malaria and 2 million deaths, caused by the protozoan Plasmodium falciparum. Most of these cases occur in Africa. Chloroquine-resistance has led to reliance on anti-malarial antifolates, in particular the synergistic combination sulfadoxine/pyrimethamine (S/P) which targets enzymatic synthesis of folate co-factors through dihydropteroate synthase (DHPS) and dihydrofolate reductase (DHFR). Resistance to S/P is now increasing and replacement antimalarials are needed. Crystal structures are not yet available for these key enzymes in the folate pathway. This review focuses on the activity of drugs on DHFR in malaria parasites, attempts to interpret differences in activity of pyrimethamine and its related drugs, and to clarify how residue changes due to point mutations determine the development of resistance. In homology-modelled P. falciparum DHFR (PfDHFR), the typical structure of four alpha-helices, 8-stranded beta-sheet, four Loops and eight Turns is clearly seen. Long polar sequences specific for Plasmodium are inserted in Turns 1 and 2. Structures immediately concerned in drug binding are beta-A, L1, alpha-B, alpha-C, T-3, beta-E, alpha-F, and beta-F. The roles of several mutations associated with resistance are discussed. In view of sequence differences in turn 3 in PfDHFR and in the human enzyme, and the marked interaction with residues of T3 of the experimental flexible antifolate WR99210 effective in pyrimethamine and cycloguanil resistance, further drug development in this area is indicated.
Topics: Animals; Drug Resistance; Folic Acid Antagonists; Humans; Malaria, Falciparum; Mutation; Plasmodium falciparum
PubMed: 11969121
DOI: 10.3184/003685002783238906 -
Cell Host & Microbe Oct 2011Plasmodium falciparum and Toxoplasma gondii are obligate intracellular apicomplexan parasites that rapidly invade and extensively modify host cells. Protein...
Plasmodium falciparum and Toxoplasma gondii are obligate intracellular apicomplexan parasites that rapidly invade and extensively modify host cells. Protein phosphorylation is one mechanism by which these parasites can control such processes. Here we present a phosphoproteome analysis of peptides enriched from schizont stage P. falciparum and T. gondii tachyzoites that are either "intracellular" or purified away from host material. Using liquid chromatography-tandem mass spectrometry, we identified over 5,000 and 10,000 previously unknown phosphorylation sites in P. falciparum and T. gondii, respectively, revealing that protein phosphorylation is an extensively used regulation mechanism both within and beyond parasite boundaries. Unexpectedly, both parasites have phosphorylated tyrosines, and P. falciparum has unusual phosphorylation motifs that are apparently shaped by its A:T-rich genome. This data set provides important information on the role of phosphorylation in the host-pathogen interaction and clues to the evolutionary forces operating on protein phosphorylation motifs in both parasites.
Topics: Adaptation, Biological; Chromatography, Liquid; Gene Expression Regulation; Mass Spectrometry; Phosphoproteins; Phosphorylation; Plasmodium falciparum; Protein Processing, Post-Translational; Proteome; Signal Transduction; Toxoplasma
PubMed: 22018241
DOI: 10.1016/j.chom.2011.09.004 -
The Journal of Antimicrobial... Mar 2010The in vitro selection of antimicrobial resistance in important pathogens can provide critical information on the genetic basis of drug resistance, and such information... (Review)
Review
The in vitro selection of antimicrobial resistance in important pathogens can provide critical information on the genetic basis of drug resistance, and such information can be used to predict, anticipate and even contain the spread of resistance in clinical practice. For instance, the discovery of the role of pfmdr1 in mefloquine resistance in malaria parasites resulted from in vitro studies. However, the in vitro selection of resistance is difficult, challenging and time consuming. In this review, we discuss the key parameters that impact on the efficiency of the in vitro selection of resistance, and propose strategies to improve and streamline this process.
Topics: Animals; Antimalarials; Drug Resistance; Parasitology; Plasmodium falciparum; Selection, Genetic
PubMed: 20022938
DOI: 10.1093/jac/dkp449 -
Clinical Microbiology and Infection :... Oct 2013Following a decade-long scale up of malaria control through vector control interventions, the introduction of rapid diagnostic tests and highly efficacious... (Review)
Review
Following a decade-long scale up of malaria control through vector control interventions, the introduction of rapid diagnostic tests and highly efficacious Artemisinin-based Combination Therapy (ACT) along with other measures, global malaria incidence declined significantly. The recent development of artemisinin resistance on the Cambodia-Thailand border, however, is of great concern. This review encompasses the background of artemisinin resistance in Plasmodium falciparum, its situation, especially in the Greater Mekong Sub-region (GMS), and the responses taken to overcome this resistance. The difficulties in defining resistance are presented, particularly the necessity of measuring the clinical response to artemisinins using the slow parasite-clearance phenotype. Efforts to understand the molecular basis of artemisinin resistance and the search for molecular markers are reviewed. The markers, once identified, can be applied as an efficient tool for resistance surveillance. Despite the limitation of current surveillance methods, it is important to continue vigilance for artemisinin resistance. The therapeutic efficacy "in vivo study" network for monitoring antimalarial resistance in the GMS has been strengthened. GMS countries are working together in response to artemisinin resistance and aim to eliminate all P. falciparum parasites. These efforts are crucial since a resurgence of malaria due to drug and/or insecticide resistance, program cuts, lack of political support and donor fatigue could set back malaria control success in the sub-region and threaten malaria control and elimination if resistance spreads to other regions.
Topics: Antimalarials; Artemisinins; Asia, Southeastern; Drug Resistance; Drug Therapy, Combination; Humans; Malaria, Falciparum; Parasitemia; Plasmodium falciparum
PubMed: 24033691
DOI: 10.1111/1469-0691.12316 -
Scientific Reports Jul 2020Human malaria parasites have complex but poorly understood population dynamics inside their human host. In some but not all infections, parasites progress synchronously...
Human malaria parasites have complex but poorly understood population dynamics inside their human host. In some but not all infections, parasites progress synchronously through the 48 h lifecycle following erythrocyte invasion, such that at any one time there is a limited spread of parasites at a particular time (hours) post-invasion. Patients presenting with older parasites, and with asynchronous infections, have been reported to have higher risks of fatal outcomes, associated with higher parasite biomass and multiplication rates respectively. However, practical tools to assess synchrony and estimate parasite age post-invasion in patient samples are lacking. We have developed a novel method based on three genes differentially expressed over the parasite intra-erythrocytic lifecycle, and applied it to samples from patients with uncomplicated malaria attending two health clinics in Ghana. We found that most patients presented with synchronous infections, and with parasites within 12 h of erythrocyte invasion. Finally we investigated if clinical features such as fever and parasite density could act as predictors of parasite age and synchrony. The new method is a simple and practicable approach to study parasite dynamics in naturally-infected patients, and is a significant improvement on the subjective microscopical methods for parasite staging in vivo, aiding patient management.
Topics: Aging; Animals; Ethnicity; Gene Expression Regulation, Developmental; Ghana; Humans; Life Cycle Stages; Malaria, Falciparum; Models, Biological; Parasitemia; Plasmodium falciparum
PubMed: 32616767
DOI: 10.1038/s41598-020-67817-6