scholarly journals Structural basis for inhibition of erythrocyte invasion by antibodies to Plasmodium falciparum protein CyRPA

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Lin Chen ◽  
Yibin Xu ◽  
Wilson Wong ◽  
Jennifer K Thompson ◽  
Julie Healer ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
Plasmodium Falciparum ◽  
Complex Formation ◽  
Parasite Growth ◽  
Structural Basis ◽  
Fab Fragment ◽  
Asexual Blood Stage ◽  
Erythrocyte Invasion ◽  
Falciparum Protein ◽  
Conserved Epitope

Plasmodium falciparum causes malaria in humans with over 450,000 deaths annually. The asexual blood stage involves invasion of erythrocytes by merozoites, in which they grow and divide to release daughter merozoites, which in turn invade new erythrocytes perpetuating the cycle responsible for malaria. A key step in merozoite invasion is the essential binding of PfRh5/CyRPA/PfRipr complex to basigin, a step linked to the formation of a pore between merozoites and erythrocytes. We show CyRPA interacts directly with PfRh5. An invasion inhibitory monoclonal antibody to CyRPA blocks binding of CyRPA to PfRh5 and complex formation thus illuminating the molecular mechanism for inhibition of parasite growth. We determined the crystal structures of CyRPA alone and in complex with an antibody Fab fragment. CyRPA has a six-bladed β-propeller fold, and we identify the region that interacts with PfRh5. This functionally conserved epitope is a potential target for vaccines against P. falciparum.

scholarly journals Structural basis of LaDR5, a novel agonistic anti-death receptor 5 (DR5) monoclonal antibody, to inhibit DR5/TRAIL complex formation

2012 ◽  
Vol 13 (1) ◽  
pp. 40
Author(s):  
Chunxia Qiao ◽  
Meiyun Hu ◽  
Leiming Guo ◽  
Ming Lv ◽  
Zhou Lin ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
Complex Formation ◽  
Death Receptor ◽  
Structural Basis ◽  
Death Receptor 5

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 Cryo-EM structures reveal distinct mechanisms of inhibition of the human multidrug transporter ABCB1

2020 ◽  
Vol 117 (42) ◽  
pp. 26245-26253 ◽  
Author(s):  
Kamil Nosol ◽  
Ksenija Romane ◽  
Rossitza N. Irobalieva ◽  
Amer Alam ◽  
Julia Kowal ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
Drug Disposition ◽  
Structural Data ◽  
Binding Pocket ◽  
Drug Binding ◽  
Structural Basis ◽  
Multidrug Transporter ◽  
Fab Fragment ◽  
Extrusion Mechanism ◽  
Inhibitory Antibodies

ABCB1 detoxifies cells by exporting diverse xenobiotic compounds, thereby limiting drug disposition and contributing to multidrug resistance in cancer cells. Multiple small-molecule inhibitors and inhibitory antibodies have been developed for therapeutic applications, but the structural basis of their activity is insufficiently understood. We determined cryo-EM structures of nanodisc-reconstituted, human ABCB1 in complex with the Fab fragment of the inhibitory, monoclonal antibody MRK16 and bound to a substrate (the antitumor drug vincristine) or to the potent inhibitors elacridar, tariquidar, or zosuquidar. We found that inhibitors bound in pairs, with one molecule lodged in the central drug-binding pocket and a second extending into a phenylalanine-rich cavity that we termed the “access tunnel.” This finding explains how inhibitors can act as substrates at low concentration, but interfere with the early steps of the peristaltic extrusion mechanism at higher concentration. Our structural data will also help the development of more potent and selective ABCB1 inhibitors.

scholarly journals Variation in the Expression of a Plasmodium falciparum Protein Family Implicated in Erythrocyte Invasion

2002 ◽  
Vol 70 (10) ◽  
pp. 5779-5789 ◽  
Author(s):  
Helen M. Taylor ◽  
Munira Grainger ◽  
Anthony A. Holder
Keyword(s):  
Plasmodium Falciparum ◽  
Protein Expression ◽  
Protein Family ◽  
Apical Surface ◽  
Invasion Pathways ◽  
Gene Number ◽  
Erythrocyte Invasion ◽  
The Family ◽  
Sequence Polymorphisms ◽  
Falciparum Protein

ABSTRACT The PfRH protein family of Plasmodium falciparum is implicated in erythrocyte invasion. Here we report variations in the sequence, transcription, and protein expression of four different members of this family in three parasite lines, 3D7, T996, and FCB1. There are sequence polymorphisms in PfRH1, PfRH2a, PfRH2b, and PfRH3, ranging from variations across repeat regions to a 585-bp deletion in the 3′ end of PfRH2b in T996. Not all the genes are transcribed: although all members of the family are transcribed in 3D7 and T996, PfRH2a and PfRH2b are not transcribed in FCB1. The PfRH1, PfRH2a, and PfRH2b proteins are expressed in late schizonts and merozoites and are located in apical organelles and on the apical surface. However, the PfRH1 protein does not appear to be correctly targeted to the apex in 3D7 and T996. In contrast, the PfRH1 protein is present at the apical end of FCB1 merozoites, but the PfRH2a and PfRH2b proteins are undetectable. The apparent redundancy in the PfRH family of proteins at the level of gene number and sequence and the variations in transcription and protein expression may allow the parasite to use alternative invasion pathways.

scholarly journals Deletion of Plasmodium falciparum ubc13 increases parasite sensitivity to the mutagen, methyl methanesulfonate and dihydroartemisinin

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Supawadee Maneekesorn ◽  
Ellen Knuepfer ◽  
Judith L. Green ◽  
Parichat Prommana ◽  
Chairat Uthaipibull ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Antimalarial Drug ◽  
Parasite Growth ◽  
Methyl Methanesulfonate ◽  
Asexual Blood Stage ◽  
Protein Substrates ◽  
Ubiquitin Conjugating Enzyme ◽  
Increased Sensitivity ◽  
Conjugating Enzyme

AbstractThe inducible Di-Cre system was used to delete the putative ubiquitin-conjugating enzyme 13 gene (ubc13) of Plasmodium falciparum to study its role in ubiquitylation and the functional consequence during the parasite asexual blood stage. Deletion resulted in a significant reduction of parasite growth in vitro, reduced ubiquitylation of the Lys63 residue of ubiquitin attached to protein substrates, and an increased sensitivity of the parasite to both the mutagen, methyl methanesulfonate and the antimalarial drug dihydroartemisinin (DHA), but not chloroquine. The parasite was also sensitive to the UBC13 inhibitor NSC697923. The data suggest that this gene does code for an ubiquitin conjugating enzyme responsible for K63 ubiquitylation, which is important in DNA repair pathways as was previously demonstrated in other organisms. The increased parasite sensitivity to DHA in the absence of ubc13 function indicates that DHA may act primarily through this pathway and that inhibitors of UBC13 may both enhance the efficacy of this antimalarial drug and directly inhibit parasite growth.

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