Biology subjects

van Ooij, C.

Publications and source records attributed to van Ooij, C..

6 recordsLinked to original sources

bioRxiv2026

Essential function reflected in the phylodynamics of a multigene family: the pir genes of malaria parasites

The genomes of malaria parasites (Plasmodium spp.) encode many gene families, which are intimately associated with host interactions and disease in these important pathogens. The largest malaria gene family is the Plasmodium interspersed repeat (pir) genes, present in rodent, primate and most human malaria parasites, which are suggested to have originated from one highly conserved gene, which we call pirC1. The precise function(s) of pir is unknown but to determine their potentially multifarious roles we must understand the evolutionary dynamics of pir repertoire to discriminate among the many genes. Here we estimate the global phylogeny for pir genes in 14 Plasmodium species and one Hepatocystis species. We reveal that pirC1 is not the common ancestor but is one of several orthologous genes conserved in multiple species amidst the rapid turnover of species-specific paralogs. We show that the PIRC1 protein is nonetheless essential for blood stage growth of P. berghei, P. chabaudi and P. knowlesi, as parasites lacking the pirC1 gene could not be generated or had severely reduced growth rates. As this effect was observed both in vivo and in vitro, the role of pirC1 is not related to host immune interaction. Rather, P. berghei and P. knowlesi PIRC1 are secreted from the parasite, pointing to a role in parasite interaction with the host cell or nutrient uptake by blood stages. The phylodynamics of pir genes indicate that old orthologs, like pirC1, and younger within-species paralogs could have fundamentally different roles, and emphasize the need to distinguish between them in future. This study is the first to provide evidence for the existence of an essential pir gene and provides a robust rationale for further experimental approaches to pir gene functions. SIGNFICANCEThe genomes of malaria parasites (Plasmodium) contain many different gene families, of which the pir family is the largest, with more than 1000 members in some species. The PIR proteins are likely important for parasite fitness but their precise functions remain unknown - roles in adherence of infected red blood cells to blood vessels, virulence and immune evasion of have been suggested. How, and why, this highly diverse gene family evolved is a significant question both for understanding malaria physiology and pathogenesis. Here we present a comprehensive pir phylogeny, identifying the origins of gene diversity during Plasmodium evolution and a select group of highly conserved genes. We show that one conserved pir gene (pirC1) encodes a protein that is essential for optimal growth of multiple malaria parasites during the asexual blood stage, both in the host and in vitro. This indicates that pirC1 function relates to interaction with the host cell or nutrient acquisition, and not to immune evasion or sequestration, (although this might still be the function of other pir genes). This study provides a robust rationale for the hitherto baffling diversity of pir genes, and shows why it is important to distinguish old orthologs from young paralogs in future studies on pir gene function.

microbiology↗

bioRxiv2024

Malaria parasites undergo a rapid and extensive metamorphosis after invasion of the host erythrocyte

Within the human host, the symptoms of malaria are caused by the replication of malaria parasites within erythrocytes. Growth inside the erythrocyte exposes the parasites to the normal surveillance of erythrocytes by the host organism, in particular the clearance of erythrocytes in the spleen. Here we show that the malaria parasite Plasmodium falciparum undergoes a rapid, multi-step metamorphosis that transforms the invasive merozoite into an amoeboid-shaped cell within minutes after invading erythrocytes. This transformation involves an increase in the parasite surface area and is mediated by factors already present in the merozoite, including the parasite phospholipid transfer protein PV6. Parasites lacking PV6 do not assume an amoeboid form and instead are spherical and have a smaller surface area than amoeboid forms. Furthermore, erythrocytes infected with parasites lacking PV6 undergo a higher loss of surface area upon infection by P. falciparum, which affects the traversal of infected erythrocytes through the spleen. This is the first evidence that after invasion, the parasite undergoes a rapid, complex metamorphosis within the host erythrocyte that promotes survival in the host.

microbiology↗

bioRxiv2023

Timing of dense granule biogenesis in asexual malaria parasites

Malaria is an important infectious disease that continues to claim hundreds of thousands of lives annually. The disease is caused by infection of host erythrocytes by apicomplexan parasites of the genus Plasmodium. The parasite contains three different apical organelles - micronemes, rhoptries and dense granules - whose contents are secreted to mediate binding to and invasion of the host cell and the extensive remodelling of the host cell that occurs following invasion. Whereas the roles of micronemes and rhoptries in binding and invasion of the host erythrocyte have been studied in detail, the role of dense granules (DGs) in Plasmodium parasites are poorly understood. They have been proposed to control host cell remodelling through regulated protein secretion after invasion, but many basic aspects of the biology of DGs remain unknown. Here we describe DG biogenesis timing for the first time, using RESA localisation as a proxy for DG formation timing. We show that DG formation commences approximately 37 minutes prior to schizont egress, as measured by the recruitment of the DG marker RESA. Furthermore, using a bioinformatics approach, we aimed to predict additional cargo of the DGs and identified the J-dot protein HSP40 as a DG protein, further supporting the very early role of these organelles in the interaction of the parasite with the host cell.

microbiology↗

bioRxiv2023

Identification of a non-exported Plasmepsin V substrate that functions in the parasitophorous vacuole of malaria parasites

Malaria parasites alter multiple properties of the host erythrocyte by exporting proteins into the host cell. Many exported proteins contain a five-amino acid motif called the Plasmodium Export Element (PEXEL) that is cleaved by the parasite protease Plasmepsin V (PM V). The presence of a PEXEL is considered a signature of protein export and has been used to identify a large number of exported proteins. The export of proteins becomes essential midway through the intraerythrocytic cycle - preventing protein export blocks parasite development 18-24 h after invasion. However, a genetic investigation revealed that the absence of the PEXEL protein PFA0210c causes parasite development to arrest immediately after invasion. We now show that this protein (renamed PV6) is cleaved by PM V but not exported into the host erythrocyte and instead functions in the parasitophorous vacuole. Furthermore, we show that the lysine residue that becomes the N terminus of PV6 after processing by PM V prevents export. This is the first example of a native Plasmodium falciparum PM V substrate that remains in the parasitophorous vacuole. We also provide evidence that the parasite produces at least one additional essential, non-exported PM V substrate. These results reveal that the presence of a PEXEL, and hence processing of a protein by PM V, does not always target a protein for export and that PM V has a broader function in parasite growth beyond processing exported proteins. Furthermore, we utilized this finding to investigate possible requirements for protein export further.

microbiology↗

bioRxiv2023

Distribution of malaria parasite-derived phosphatidylcholine in the infected erythrocyte

Malaria parasites modify their host erythrocyte in multiple ways, leading to changes in the deformability, adhesiveness and permeability of the host erythrocyte. Most of these changes are mediated by proteins exported from the parasite to the host erythrocyte, where these proteins interact with the host cell cytoskeleton or form complexes in the plasma membrane of the infected erythrocyte. In addition, malaria parasites induce the formation of membranous compartments - the parasitophorous vacuole, the tubovesicular network, the Maurers clefts and small vesicles - within the infected erythrocyte, a cell that is normally devoid of internal membranes. After infection, changes also occur in the composition and asymmetry of the erythrocyte plasma membrane. Although many aspects of the mechanism of export of parasite proteins have become clear, the mechanism by which these membranous compartments are formed and expanded is almost entirely unknown. To determine whether parasite-derived phospholipids play a part in these processes, we applied a metabolic labelling technique that allows phosphatidylcholine to be labelled with a fluorophore. As the host erythrocyte cannot synthesize phospholipids, within infected erythrocytes, only parasite-derived phosphatidylcholine will be labelled with this technique. The results revealed that phosphatidylcholine produced by the parasite is distributed throughout the infected erythrocyte, including the TVN and the erythrocyte plasma membrane, but not Maurers clefts. Interestingly, labelled phospholipids were also detected in the erythrocyte plasma membrane very soon after invasion of the parasites, indicating that the parasite may add phospholipids to the host erythrocyte during invasion.

microbiology↗

bioRxiv2020

Use of a highly specific kinase inhibitor for rapid, simple and precise synchronization of Plasmodium falciparum and Plasmodium knowlesi asexual stage parasites

During the course of the asexual erythrocytic stage of development, Plasmodium spp. parasites undergo a series of morphological changes and induce alterations in the host cell. At the end of this stage, the parasites exit the host cell, after which the progeny invade a new host cell. These processes are rapid and occur in a time-dependent manner. Of particular importance, egress and invasion of erythrocytes by the parasite are difficult to capture in an unsynchronized culture, or even a culture that has been synchronized to within hours. Therefore, precise synchronization of parasite cultures is of paramount importance for the investigation of these processes. Here we describe a method for synchronizing Plasmodium falciparum and Plasmodium knowlesi asexual blood stage parasites with ML10, a highly specific inhibitor of the cGMP-dependent protein kinase (PKG) that arrests parasite growth approximately 15 minutes prior to egress. This inhibitor allows parasite cultures to be synchronized to within minutes, with a simple wash step. Furthermore, we show that parasites remain viable for several hours after becoming arrested by the compound and that ML10 has advantages over the previously used PKG inhibitor Compound 2. Here, we demonstrate that ML10 is an invaluable tool for the study of Plasmodium spp. asexual blood stage biology and for the routine synchronization of P. falciparum and P. knowlesi cultures.

microbiology↗