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Vital role for the Plasmodium actin capping protein (CP) beta-subunit in motility of malaria sporozoites.

ABSTRACT: Summary Successful malaria transmission from the mosquito vector to the mammalian host depends crucially on active sporozoite motility. Sporozoite locomotion and host cell invasion are driven by the parasite's own actin/myosin motor. A unique feature of this motor machinery is the presence of very short subpellicular actin filaments. Therefore, F-actin stabilizing proteins likely play a central role in parasite locomotion. Here, we investigated the role of the Plasmodium berghei actin capping protein (PbCP), an orthologue of the heterodimeric regulator of filament barbed end growth, by reverse genetics. Parasites containing a deletion of the CP beta-subunit developed normally during the pathogenic erythrocytic cycle. However, due to reduced ookinete motility, mutant parasites form fewer oocysts and sporozoites in the Anopheles vector. These sporozoites display a vital deficiency in forward gliding motility and fail to colonize the mosquito salivary glands, resulting in complete attenuation of life cycle progression. Together, our results show that the CP beta-subunit exerts an essential role in the insect vector before malaria transmission to the mammalian host. The vital role is restricted to fast locomotion, as displayed by Plasmodium sporozoites.

SUBMITTER: Ganter M

PROVIDER: S-EPMC2810434 | biostudies-literature | 2009 Dec

REPOSITORIES: biostudies-literature

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Vital role for the Plasmodium actin capping protein (CP) beta-subunit in motility of malaria sporozoites.

Ganter Markus M Schüler Herwig H Matuschewski Kai K

Molecular microbiology 20090804 6

Summary Successful malaria transmission from the mosquito vector to the mammalian host depends crucially on active sporozoite motility. Sporozoite locomotion and host cell invasion are driven by the parasite's own actin/myosin motor. A unique feature of this motor machinery is the presence of very short subpellicular actin filaments. Therefore, F-actin stabilizing proteins likely play a central role in parasite locomotion. Here, we investigated the role of the Plasmodium berghei actin capping pr ...[more]

PMID: 19682250

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Project description:UnlabelledMalaria is transmitted when motile sporozoites are injected into the dermis by an infected female Anopheles mosquito. Inside the mosquito vector, sporozoites egress from midgut-associated oocysts and eventually penetrate the acinar cells of salivary glands. Parasite-encoded factors with exclusive vital roles in the insect vector can be studied by classical reverse genetics. Here, we characterized the in vivo roles of Plasmodium berghei falstatin/ICP (inhibitor of cysteine proteases). This protein was previously suggested to act as a protease inhibitor during erythrocyte invasion. We show by targeted gene disruption that loss of ICP function does not affect growth inside the mammalian host but causes a complete defect in sporozoite transmission. Sporogony occurred normally in icp(-) parasites, but hemocoel sporozoites showed a defect in continuous gliding motility and infectivity for salivary glands, which are prerequisites for sporozoite transmission to the mammalian host. Absence of ICP correlates with enhanced cleavage of circumsporozoite protein, in agreement with a role as a protease regulator. We conclude that ICP is essential for only the final stages of sporozoite maturation inside the mosquito vector. This study is the first genetic evidence that an ICP is necessary for the productive motility of a eukaryotic parasitic cell.ImportanceCysteine proteases and their inhibitors are considered ideal drug targets for the treatment of a wide range of diseases, including cancer and parasitic infections. In protozoan parasites, including Leishmania, Trypanosoma, and Plasmodium, cysteine proteases play important roles in life cycle progression. A mouse malaria model provides an unprecedented opportunity to study the roles of a parasite-encoded inhibitor of cysteine proteases (ICP) over the entire parasite life cycle. By precise gene deletion, we found no evidence that ICP influences disease progression or parasite virulence. Instead, we discovered that this factor is necessary for parasite movement and malaria transmission from mosquitoes to mammals. This finding in a fast-moving unicellular protozoan has important implications for malaria intervention strategies and the roles of ICPs in the regulation of eukaryotic cell migration.

Project description:BackgroundGliding motility in Plasmodium parasites, the aetiological agents of malaria disease, is mediated by an actomyosin motor anchored in the outer pellicle of the motile cell. Effective motility is dependent on a parasite myosin motor and turnover of dynamic parasite actin filaments. To date, however, the basis for directional motility is not known. Whilst myosin is very likely orientated as a result of its anchorage within the parasite, how actin filaments are orientated to facilitate directional force generation remains unexplained. In addition, recent evidence has questioned the linkage between actin filaments and secreted surface antigens leaving the way by which motor force is transmitted to the extracellular milieu unknown. Malaria parasites possess a markedly reduced repertoire of actin regulators, among which few are predicted to interact with filamentous (F)-actin directly. One of these, PF3D7_1251200, shows strong homology to the coronin family of actin-filament binding proteins, herein referred to as PfCoronin.MethodsHere the N terminal beta propeller domain of PfCoronin (PfCor-N) was expressed to assess its ability to bind and bundle pre-formed actin filaments by sedimentation assay, total internal reflection fluorescence (TIRF) microscopy and confocal imaging as well as to explore its ability to bind phospholipids. In parallel a tagged PfCoronin line in Plasmodium falciparum was generated to determine the cellular localization of the protein during asexual parasite development and blood-stage merozoite invasion.ResultsA combination of biochemical approaches demonstrated that the N-terminal beta-propeller domain of PfCoronin is capable of binding F-actin and facilitating formation of parallel filament bundles. In parasites, PfCoronin is expressed late in the asexual lifecycle and localizes to the pellicle region of invasive merozoites before and during erythrocyte entry. PfCoronin also associates strongly with membranes within the cell, likely mediated by interactions with phosphatidylinositol-4,5-bisphosphate (PI(4,5)P2) at the plasma membrane.ConclusionsThese data suggest PfCoronin may fulfil a key role as the critical determinant of actin filament organization in the Plasmodium cell. This raises the possibility that macro-molecular organization of actin mediates directional motility in gliding parasites.

Dataset Information

Vital role for the Plasmodium actin capping protein (CP) beta-subunit in motility of malaria sporozoites.

Publications

Vital role for the Plasmodium actin capping protein (CP) beta-subunit in motility of malaria sporozoites.

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