Biology subjects

Marinach, C.

Publications and source records attributed to Marinach, C..

8 recordsLinked to original sources

bioRxiv2026

The CLAMP-Linked Invasion Protein (CLIP) plays an essential role in Plasmodium berghei zoites

Apicomplexan parasites such as Toxoplasma and Plasmodium spp. rely on the sequential secretion of parasite apical organelles, called micronemes and rhoptries, to invade host cells. The claudin-like apicomplexan microneme protein (CLAMP) is a conserved protein that plays an essential role during host cell invasion in Toxoplasma and Plasmodium zoites. Previous studies have shown that CLAMP is essential in Plasmodium merozoites for erythrocyte invasion and also in sporozoites for the invasion of the mosquito vector salivary glands and of mammalian host hepatocytes. In Toxoplasma gondii tachyzoites, CLAMP forms a complex with two other microneme proteins, the Secreted Protein with an Altered Thrombospondin Repeat (SPATR) and the CLAMP-Linked Invasion Protein (CLIP). Both SPATR and CLIP are also expressed in Plasmodium sporozoites, and downregulation of SPATR impacts sporozoite infectivity in P. berghei. In contrast, the role of CLIP in sporozoites remains unknown. To study the function of CLIP, we used a CRISPR-assisted conditional genome editing strategy based on the dimerisable Cre recombinase in the rodent malaria model parasite P. berghei. Deletion of clip in P. berghei blood stages impaired parasite growth and prevented erythrocyte invasion by merozoites. Upon deletion of clip gene in P. berghei transmission stages, sporozoite development in mosquitoes was not affected, but invasion of the mosquito salivary glands was dramatically reduced. In addition, CLIP-deficient sporozoites were impaired in cell traversal and productive invasion of mammalian hepatocytes, associated with a defect in gliding motility, recapitulating the phenotype of CLAMP-deficient parasites. Collectively, our data demonstrate that CLIP plays an essential role in host cell invasion by P. berghei merozoites and sporozoites, and support a conserved role of the CLAMP-CLIP-SPATR complex in invasive stages of apicomplexan parasites.

microbiology↗

bioRxiv2026

A structure-based epitope tagging approach identifies vulnerable sites on the malarial P36-P52 protein complex for antibody-mediated neutralization of Plasmodium sporozoites

Malaria is caused by apicomplexan parasites of the genus Plasmodium, which are transmitted through the bite of Anopheles mosquitoes that inject sporozoites (SPZs) into the skin. SPZs migrate to and infect the liver for an initial round of replication. SPZs and liver stages have long been considered as ideal targets for malaria vaccines. The main SPZ surface protein, the circumsporozoite protein (CSP), is the target of currently approved malaria vaccines and prophylactic antibody therapies. Studies in rodent malaria models have shown that anti-CSP antibodies exert their protective effect mainly in the skin, but some of the most potent anti-CSP monoclonal antibodies show additional protective effects in the vasculature and liver. Other SPZ proteins involved at different steps of the infection process may thus represent additional targets for antibody-mediated neutralization. Three 6-cysteine (6-Cys) domain proteins (P36, P52 and B9) play an essential role during SPZ invasion of hepatocytes, yet their molecular function and whether they can be targeted by neutralizing antibodies remains unknown. Here, to fill this gap, we combined an integrative structural biology approach with functional experiments in the P. berghei rodent malaria model. AlphaFold-based structural modeling followed by experimental validation via electron microscopy and small-angle X-ray scattering indicated that the P36-P52 heterodimer displays a head-to-tail architecture with an interaction interface that is largely conserved among Plasmodium species. The structural models supported the rational design of an epitope tagging approach, which, combined with neutralizing assays, revealed that antibodies against P36 and P52 can efficiently block invasion of hepatocytes by SPZs in culture conditions. The data show that the inhibitory activity of antibodies heavily depends on epitope position and revealed that antibody-exposed vulnerable sites lie on the membrane-distal side of the P36-P52 heterodimer. In contrast, antibodies targeting B9 had no inhibitory effect on SPZ invasion, irrespective of epitope positioning. These data show that the invasion step could be targeted by antibodies and indicate that the P36-P52 complex may be considered as a potential target for the development of next generation pre-erythrocytic malaria vaccines or therapeutic antibodies.

microbiology↗

bioRxiv2024

Constitutive expression of Cas9 and rapamycin-inducible Cre recombinase facilitates conditional genome editing in Plasmodium berghei

Malaria is caused by protozoan parasites of the genus Plasmodium and remains a global health concern. The parasite has a highly adaptable life cycle comprising successive rounds of asexual replication in a vertebrate host and sexual maturation in the mosquito vector Anopheles. Genetic manipulation of the parasite has been instrumental for deciphering the function of Plasmodium genes. Conventional reverse genetic tools cannot be used to study essential genes of the asexual blood stages, thereby necessitating the development of conditional strategies. Among various such strategies, the rapamycin-inducible dimerisable Cre (DiCre) recombinase system emerged as a powerful approach for conditional editing of essential genes in human-infecting P. falciparum and in the rodent malaria model parasite P. berghei. We previously generated a DiCre-expressing P. berghei line and validated it by conditionally deleting several essential asexual stage genes, revealing their important role also in sporozoites. The advent of CRISPR enabled targeted genome editing with higher accuracy and specificity and greatly advanced genome engineering in Plasmodium spp. Here, we developed new P. berghei parasite lines by integrating the DiCre cassette and a fluorescent marker in parasites constitutively expressing Cas9. Owing to the dual integration of CRISPR-Cas9 and DiCre, these new lines allow unparalleled levels of gene modification and conditional regulation simultaneously. To illustrate the versatility of this new tool, we conditionally knocked-out the essential gene encoding the claudin-like apicomplexan micronemal protein (CLAMP) in P. berghei and confirm the role of CLAMP during invasion of erythrocytes.

microbiology↗

bioRxiv2022

The claudin-like apicomplexan microneme protein is required for gliding motility and infectivity of Plasmodium sporozoites

Invasion of host cells by apicomplexan parasites such as Toxoplasma and Plasmodium spp requires the sequential secretion of the parasite apical organelles, the micronemes and the rhoptries. The claudin-like apicomplexan microneme protein (CLAMP) is a conserved protein that plays an essential role during invasion in Toxoplasma gondii tachyzoites and Plasmodium falciparum merozoites. CLAMP is also expressed in Plasmodium sporozoites, the mosquito-transmitted forms of the malaria parasite, but its role in this stage is still unknown. CLAMP is essential for Plasmodium blood stage growth and is refractory to conventional gene deletion. To circumvent this obstacle and study the function of CLAMP in sporozoites, we used a conditional genome editing strategy based on the dimerisable Cre recombinase in the rodent malaria model parasite P. berghei. We successfully deleted clamp gene in P. berghei transmission stages and analyzed the functional consequences on sporozoite infectivity. In mosquitoes, sporozoite development and egress from oocysts was not affected in conditional mutants. However, invasion of the mosquito salivary glands was dramatically reduced upon deletion of clamp gene. In addition, CLAMP-deficient sporozoites were impaired in cell traversal and productive invasion of mammalian hepatocytes. This severe phenotype was associated with major defects in gliding motility and with reduced shedding of the sporozoite adhesin TRAP. These results demonstrate that CLAMP is essential across invasive stages of the malaria parasite, and strongly suggest that the protein acts upstream of host cell invasion, possibly by regulating the secretion or function of adhesins in Plasmodium sporozoites. Author summaryPlasmodium parasites, the causative agents of malaria, are transmitted during the bite of an infected mosquito. Infectious parasite stages known as sporozoites are released from the insect salivary glands and injected into the host skin. Sporozoites rapidly migrate to the host liver, invade hepatocytes and differentiate into the next invasive forms, the merozoites, which invade and replicate inside red blood cells. Sporozoite motility and host cell invasion rely on the secretion of apical organelles called micronemes and rhoptries. Here we characterize the function of a microneme protein expressed both in merozoites and sporozoites, the claudin-like protein CLAMP. We used a conditional genome editing strategy in a rodent malaria model to generate CLAMP-deficient sporozoites. In the absence of CLAMP, sporozoites failed to invade mosquito salivary glands and mammalian hepatocytes, and showed defects in gliding motility and microneme secretion. Our data establish that CLAMP plays an essential role across Plasmodium invasive stages, and might represent a potential target for transmission-blocking antimalarial strategies.

microbiology↗

bioRxiv2022

The AMA1-RON complex drives Plasmodium sporozoite invasion in the mosquito and mammalian hosts

Plasmodium sporozoites that are transmitted by blood-feeding female Anopheles mosquitoes invade hepatocytes for an initial round of intracellular replication, leading to the release of merozoites that invade and multiply within red blood cells. Sporozoites and merozoites share a number of proteins that are expressed by both stages, including the Apical Membrane Antigen 1 (AMA1) and the Rhoptry Neck Proteins (RONs). Although AMA1 and RONs are essential for merozoite invasion of erythrocytes during asexual blood stage replication of the parasite, their function in sporozoites is still unclear. Here we show that AMA1 interacts with RONs in mature sporozoites. By using DiCre-mediated conditional gene deletion in P. berghei, we demonstrate that loss of AMA1, RON2 or RON4 in sporozoites impairs colonization of the mosquito salivary glands and invasion of mammalian hepatocytes, without affecting transcellular parasite migration. Our data establish that AMA1 and RONs facilitate host cell invasion across Plasmodium invasive stages, and suggest that sporozoites use the AMA1-RON complex to safely enter the mosquito salivary glands without causing cell damage, to ensure successful parasite transmission. These results open up the possibility of targeting the AMA1-RON complex for transmission-blocking antimalarial strategies.

microbiology↗

bioRxiv2021

Plasmodium sporozoites require the protein B9 to invade hepatocytes

Plasmodium sporozoites are transmitted to a mammalian host during blood feeding by an infected mosquito and invade hepatocytes for initial replication of the parasite in the liver. This leads to the release of thousands of merozoites into the blood circulation and initiation of the pathogenic blood stages of malaria. Merozoite invasion of erythrocytes has been well characterized at the molecular and structural levels. In sharp contrast, the molecular mechanisms of sporozoite invasion of hepatocytes are poorly characterized. Here we report a new role during sporozoite entry for the B9 protein, a member of the 6-cysteine domain protein family. Using genetic tagging and gene deletion approaches in rodent malaria parasites, we show that B9 is secreted from sporozoite micronemes and is required for productive invasion of hepatocytes. Structural modelling indicates that the N-terminus of B9 forms a beta-propeller domain structurally related to CyRPA, a cysteine-rich protein forming an invasion complex with Rh5 and RIPR in P. falciparum merozoites. We provide evidence that the beta-propeller domain of B9 is essential for protein function during sporozoite entry and interacts with P36 and P52, both also essential for productive invasion of hepatocytes. Our results suggest that, despite using distinct sets of parasite and host entry factors, Plasmodium sporozoites and merozoites may share common structural modules to assemble protein complexes for invasion of host cells.

microbiology↗

bioRxiv2020

In-depth proteomic analysis of Plasmodium berghei sporozoites using trapped ion mobility spectrometry with parallel accumulation-serial fragmentation

Malaria is caused by Plasmodium spp. protozoan parasites, which are transmitted by female anopheline mosquitoes in the form of sporozoites. Once deposited in the dermis during the blood meal of the mosquito, sporozoites rapidly migrate to the liver for an initial and obligatory round of replication inside hepatocytes, before exponential multiplication of the parasite in the blood and onset of the malaria disease. Sporozoites and liver stages provide attractive targets for the development of a malaria vaccine. Until now, a single antigen from Plasmodium falciparum, the deadliest species infecting humans, has been considered for subunit vaccine clinical development, with limited success so far. This emphazises the need to identify novel targets. In this context, defining the parasite proteome is important not only to guide the down-selection of potential candidate antigens, but also to allow a better understanding of the parasite biology. Previous studies have determined the total proteome of sporozoite stages from the two main human malaria parasites, P. falciparum and P. vivax, as well as P. yoelii, a parasite that infects rodents. Another murine malaria parasite, P. berghei, has been widely used to investigate the biology of Plasmodium pre-erythrocytic stages. However, a deep view of the proteome of P. berghei sporozoites is still missing. To fill this gap, we took advantage of a novel highly sensitive timsTOF PRO mass spectrometer, based on trapped ion mobility spectrometry with parallel accumulation-serial fragmentation. Combined with three alternative methods for sporozoite purification, this approach allowed us to identify the deep proteome of P. berghei sporozoites using low numbers of parasites. This study provides a reference proteome for P. berghei sporozoites, identifying a core set of proteins expressed accross species, and illustrates how the unprecedented sensitivity of the timsTOF PRO system enables deep proteomic analysis from limited sample amounts.

microbiology↗

bioRxiv2020

Molecular determinants of SR-B1-dependent Plasmodium sporozoite entry into hepatocytic cells.

Sporozoite forms of the malaria parasite Plasmodium are transmitted by mosquitoes and first infect the liver for an initial round of replication before parasite proliferation in the blood. The molecular mechanisms involved during sporozoite invasion of hepatocytes remain poorly understood. Two receptors of the Hepatitis C virus (HCV), the tetraspanin CD81 and the scavenger receptor class B type 1 (SR-B1), play an important role during the entry of Plasmodium sporozoites into hepatocytic cells. In contrast to HCV entry, which requires both CD81 and SR-B1 together with additional host factors, CD81 and SR-B1 operate independently during malaria liver infection. Sporozoites from human-infecting P. falciparum and P. vivax rely respectively on CD81 or SR-B1. Rodent-infecting P. berghei can use SR-B1 to infect host cells as an alternative pathway to CD81, providing a tractable model to investigate the role of SR-B1 during Plasmodium liver infection. Here we show that mouse SR-B1 is less functional as compared to human SR-B1 during P. berghei infection. We took advantage of this functional difference to investigate the structural determinants of SR-B1 required for infection. Using a structure-guided strategy and chimeric mouse/human SR-B1 constructs, we could map the functional region of human SR-B1 within apical loops, suggesting that this region of the protein may play a crucial role for interaction of sporozoite ligands with host cells and thus the very first step of Plasmodium infection. IMPORTANCEMalaria is caused by Plasmodium parasites and remains one of the deadliest parasitic diseases worldwide. The parasite is transmitted by a blood feeding mosquito and first invades the liver for an initial, obligatory and silent round of replication. The liver infection is an attractive target for antimalarial vaccine strategies, however the molecular mechanisms of parasite invasion of hepatocytes remain to be fully elucidated. Two hepatocyte surface proteins are known to be important for parasite entry into hepatocytes, the tetraspanin CD81 and the scavenger receptor class B type 1 (SR-B1). These receptors constitute independent gateways depending on the Plasmodium species. Here, we identified the structural determinants of SR-B1, an important hepatocyte entry factor for human-infecting P. vivax. This study paves the way toward a better characterization of the molecular interactions underlying the crucial early stages of infection, a pre-requisite for the development of novel malaria vaccine strategies.

microbiology↗