Dataset Information

The Plasmodium berghei Ca(2+)/H(+) exchanger, PbCAX, is essential for tolerance to environmental Ca(2+) during sexual development.

ABSTRACT: Ca(2+) contributes to a myriad of important cellular processes in all organisms, including the apicomplexans, Plasmodium and Toxoplasma. Due to its varied and essential roles, free Ca(2+) is tightly regulated by complex mechanisms. These mechanisms are therefore of interest as putative drug targets. One pathway in Ca(2+) homeostatic control in apicomplexans uses a Ca(2+)/H(+) exchanger (a member of the cation exchanger family, CAX). The P. falciparum CAX (PfCAX) has recently been characterised in asexual blood stage parasites. To determine the physiological importance of apicomplexan CAXs, tagging and knock-out strategies were undertaken in the genetically tractable T. gondii and P. berghei parasites. In addition, a yeast heterologous expression system was used to study the function of apicomplexan CAXs. Tagging of T. gondii and P. berghei CAXs (TgCAX and PbCAX) under control of their endogenous promoters could not demonstrate measureable expression of either CAX in tachyzoites and asexual blood stages, respectively. These results were consistent with the ability of parasites to tolerate knock-outs of the genes for TgCAX and PbCAX at these developmental stages. In contrast, PbCAX expression was detectable during sexual stages of development in female gametocytes/gametes, zygotes and ookinetes, where it was dispersed in membranous networks within the cytosol (with minimal mitochondrial localisation). Furthermore, genetically disrupted parasites failed to develop further from "round" form zygotes, suggesting that PbCAX is essential for ookinete development and differentiation. This impeded phenotype could be rescued by removal of extracellular Ca(2+). Therefore, PbCAX provides a mechanism for free living parasites to multiply within the ionic microenvironment of the mosquito midgut. Ca(2+) homeostasis mediated by PbCAX is critical and suggests plasmodial CAXs may be targeted in approaches designed to block parasite transmission.

SUBMITTER: Guttery DS

PROVIDER: S-EPMC3585132 | biostudies-literature | 2013 Feb

REPOSITORIES: biostudies-literature

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The Plasmodium berghei Ca(2+)/H(+) exchanger, PbCAX, is essential for tolerance to environmental Ca(2+) during sexual development.

Guttery David S DS Pittman Jon K JK Frénal Karine K Poulin Benoit B McFarlane Leon R LR Slavic Ksenija K Wheatley Sally P SP Soldati-Favre Dominique D Krishna Sanjeev S Tewari Rita R Staines Henry M HM

PLoS pathogens 20130228 2

Ca(2+) contributes to a myriad of important cellular processes in all organisms, including the apicomplexans, Plasmodium and Toxoplasma. Due to its varied and essential roles, free Ca(2+) is tightly regulated by complex mechanisms. These mechanisms are therefore of interest as putative drug targets. One pathway in Ca(2+) homeostatic control in apicomplexans uses a Ca(2+)/H(+) exchanger (a member of the cation exchanger family, CAX). The P. falciparum CAX (PfCAX) has recently been characterised i ...[more]

PMID: 23468629

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Project description:BACKGROUND:The complex life cycle of malaria parasites requires well-orchestrated stage specific gene expression. In the vertebrate host the parasites grow and multiply by schizogony in two different environments: within erythrocytes and within hepatocytes. Whereas erythrocytic parasites are well-studied in this respect, relatively little is known about the exo-erythrocytic stages. METHODS:In an attempt to fill this gap, genome wide RNA-seq analyses of various exo-erythrocytic stages of Plasmodium berghei including sporozoites, samples from a time-course of liver stage development and detached cells were performed. These latter contain infectious merozoites and represent the final step in exo-erythrocytic development. RESULTS:The analysis represents the complete transcriptome of the entire life cycle of P. berghei parasites with temporal detailed analysis of the liver stage allowing comparison of gene expression across the progression of the life cycle. These RNA-seq data from different developmental stages were used to cluster genes with similar expression profiles, in order to infer their functions. A comparison with published data from other parasite stages confirmed stage-specific gene expression and revealed numerous genes that are expressed differentially in blood and exo-erythrocytic stages. One of the most exo-erythrocytic stage-specific genes was PBANKA_1003900, which has previously been annotated as a "gametocyte specific protein". The promoter of this gene drove high GFP expression in exo-erythrocytic stages, confirming its expression profile seen by RNA-seq. CONCLUSIONS:The comparative analysis of the genome wide mRNA expression profiles of erythrocytic and different exo-erythrocytic stages could be used to improve the understanding of gene regulation in Plasmodium parasites and can be used to model exo-erythrocytic stage metabolic networks toward the identification of differences in metabolic processes during schizogony in erythrocytes and hepatocytes.

Project description:The continued existence of Plasmodium parasites in physiologically distinct environments during their transmission in mosquitoes and vertebrate hosts requires effector proteins encoded by parasite genes to provide adaptability. Parasites utilize their robust stress response system involving heat shock proteins for their survival. Molecular chaperones are involved in maintaining protein homeostasis within a cell during stress, protein biogenesis and the formation of protein complexes. Due to their critical role in parasite virulence, they are considered targets for therapeutic interventions. Our results identified a putative P. berghei heat shock protein (HSP) belonging to the HSP40 family (HspJ62), which is abundantly induced upon heat stress and expressed during all parasite stages. To determine the role HspJ62, a gene-disrupted P. berghei transgenic line was developed (ΔHspJ62), which resulted in disruption of gametocyte formation. Such parasites were unable to form subsequent sexual stages because of disrupted gametogenesis, indicating the essential role of HspJ62 in gametocyte formation. Transcriptomic analysis of the transgenic line showed downregulation of a number of genes, most of which were specific to male or female gametocytes. The transcription factor ApiAP2 was also downregulated in ΔHspJ62 parasites. Our findings suggest that the downregulation of ApiAP2 likely disrupts the transcriptional regulation of sexual stage genes, leading to impaired gametogenesis. This finding also highlights the critical role that HspJ62 indirectly plays in the development of P. berghei sexual stages and in facilitating the conversion from the asexual blood stage to the sexual stage. This study characterizes the HspJ62 protein as a fertility factor because parasites lacking it are unable to transmit to mosquitoes. This study adds an important contribution to ongoing research aimed at understanding gametocyte differentiation and formation in parasites. The molecule adds to the list of potential drug targets that can be targeted to inhibit parasite sexual development and consequently parasite transmission.

Dataset Information

The Plasmodium berghei Ca(2+)/H(+) exchanger, PbCAX, is essential for tolerance to environmental Ca(2+) during sexual development.

Publications

The Plasmodium berghei Ca(2+)/H(+) exchanger, PbCAX, is essential for tolerance to environmental Ca(2+) during sexual development.

Similar Datasets

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