Biology subjects

Frolich, S.

Publications and source records attributed to Frolich, S..

3 recordsLinked to original sources

bioRxiv2023

Effect of antiretroviral protease inhibitors on Plasmodium falciparum erythrocyte egress and invasion

BackgroundAnti-retroviral protease inhibitors directly inhibit the growth of asexual blood stage malaria parasites, however, this activity is not fully understood. While mode of action hypotheses have included parasite aspartic protease (plasmepsin) inhibition, current data suggest that digestive vacuole plasmepsins I-IV are not essential for asexual parasite survival, that plasmepsins VI-VIII are not expressed in these parasites and that antiretroviral protease inhibitors are poor inhibitors of plasmepsin V. The remaining plasmepsins, IX and X, have recently been shown to be essential for merozoite egress and invasion, playing important roles in the processing of key proteins including the rhoptry bulb protein PfRAP1, and subtilisin-like serine protease PfSUB1, respectively. To further understand the antiplasmodial activity of antiretroviral protease inhibitors, here we investigated the impact of tipranavir, lopinavir, ritonavir and saquinavir on the processing of PfRAP1, the PfSUB1-processed PfMSP1, and the egress and invasion of P. falciparum parasites from human erythrocytes. MethodsThe effect of tipranavir, lopinavir, ritonavir and saquinavir on P. falciparum parasite egress and invasion was assessed using synchronized asexual blood stage P. falciparum parasites. Schizont rupture and purified merozoite invasion were performed with and without drug and quantified by flow cytometry analysis. The impact of selected antitretroviral protease inhibitors on PfRAP1 and PfMSP1 processing was assessed by Wesstern blot. ResultsThe effect of tipranavir, lopinavir, ritonavir and saquinavir on the egress and invasion of P. falciparum parasites from human erythrocytes varied considerably, but was low at concentrations shown to inhibit P. falciparum asexual parasite growth in vitro and negligible at clinically relevant concentrations. While the treatment of parasites with the antiretrovial protease inhibitors appeared to reduce the overall expression of PfRAP1 and PfMSP1, the processing of these proteins was not inhibited by concentrations known to inhibit parasite growth in vitro. ConclusionsThe limited activity of tipranavir, lopinavir, ritonavir and saquinavir on the egress and invasion of P. falciparum parasites from human erythrocytes and the processing of PfRAP1 and PfMSP1 suggests that plasmepsin IX and X are unlikely to be the primary targets of these drugs in these parasites.

microbiology↗

bioRxiv2023

Atlas of Plasmodium falciparum intraerythrocytic development using expansion microscopy

Apicomplexan parasites exhibit tremendous diversity in much of their fundamental cell biology, but study of these organisms using light microscopy is often hindered by their small size. Ultrastructural expansion microscopy (U-ExM) is a microscopy preparation method that physically expands the sample [~]4.5x. Here, we apply U-ExM to the human malaria parasite Plasmodium falciparum during the asexual blood stage of its lifecycle to understand how this parasite is organized in three-dimensions. Using a combination of dye-conjugated reagents and immunostaining, we have catalogued 13 different P. falciparum structures or organelles across the intraerythrocytic development of this parasite and made multiple observations about fundamental parasite cell biology. We describe that the outer centriolar plaque and its associated proteins anchor the nucleus to the parasite plasma membrane during mitosis. Furthermore, the rhoptries, Golgi, basal complex, and inner membrane complex, which form around this anchoring site while nuclei are still dividing, are concurrently segregated and maintain an association to the outer centriolar plaque until the start of segmentation. We also show that the mitochondrion and apicoplast undergo sequential fission events while maintaining an association with the outer centriolar plaque during cytokinesis. Collectively, this study represents the most detailed ultrastructural analysis of P. falciparum during its intraerythrocytic development to date, and sheds light on multiple poorly understood aspects of its organelle biogenesis and fundamental cell biology. IMPACT STATEMENTUsing ultrastructure-expansion microscopy we explore the fundamental cell biology of malaria parasites, providing new insights into processes including establishment of cell polarity and organelle fission.

cell biology↗

bioRxiv2020

Pfcerli2, a duplicated gene in the malaria parasite Plasmodium falciparum essential for invasion of erythrocytes as revealed by phylogenetic and cell biological analysis.

Merozoite invasion of host red blood cells (RBCs) is essential for survival of the human malaria parasite Plasmodium falciparum. Proteins involved with RBC binding and invasion are secreted from dual-club shaped organelles at the apical tip of the merozoite called the rhoptries. Here we characterise P. falciparum Cytosolically Exposed Rhoptry Leaflet Interacting protein 2 (PfCERLI2), as a rhoptry bulb protein that is essential for merozoite invasion. Phylogenetic analyses show that cerli2 arose through an ancestral gene duplication of cerli1, a related cytosolically exposed rhoptry bulb protein. We show that PfCERLI2 is essential for blood-stage growth and localises to the cytosolic face of the rhoptry bulb. Inducible knockdown of PfCERLI2 led to an inhibition of merozoite invasion after tight junction formation. PfCERLI2 knockdown was associated with inhibition of rhoptry antigen processing and a significant elongation of the rhoptries, suggesting that the inability of merozoites to invade is caused by aberrant rhoptry function due to PfCERLI2 deficiency. These findings identify PfCERLI2 as a protein that has key roles in rhoptry biology during merozoite invasion.

microbiology↗