The Plasmodium berghei Ca2+/H+ Exchanger, PbCAX, Is Essential for Tolerance to Environmental Ca2+ during Sexual Development

PLoS Pathogens

David S. Guttery¹  Rita Tewari¹  Benoit Poulin¹  Sanjeev Krishna²  Leon R. McFarlane²  Henry M. Staines²  Dominique Soldati-Favre³  Karine Frénal³  Jon K. Pittman⁴  Ksenija Slavic⁵  Sally P. Wheatley⁶ 

[1] Centre for Genetics and Genomics, School of Biology, Queen's Medical Centre, University of Nottingham, Nottingham, United Kingdom;Centre for Infection and Immunity, Division of Clinical Sciences, St. George's, University of London, London, United Kingdom;Department of Microbiology and Molecular Medicine, Centre Medical Universitaire, University of Geneva, Geneva, Switzerland;Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom;Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Av. Prof. Egas Moniz, Lisbon, Portugal;School of Biomedical Sciences, Queen's Medical Centre, University of Nottingham, Nottingham, United Kingdom

关键词: Plasmodium;    Apicomplexa;    Saccharomyces cerevisiae;    Parasitic life cycles;    Parasitic diseases;    Yeast;    Toxoplasma gondii;    Tachyzoites;   

DOI  :  10.1371/journal.ppat.1003191

学科分类：生物科学（综合）

来源: Public Library of Science

【 摘 要 】

Ca2+ 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 Ca2+ is tightly regulated by complex mechanisms. These mechanisms are therefore of interest as putative drug targets. One pathway in Ca2+ homeostatic control in apicomplexans uses a Ca2+/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 Ca2+. Therefore, PbCAX provides a mechanism for free living parasites to multiply within the ionic microenvironment of the mosquito midgut. Ca2+ homeostasis mediated by PbCAX is critical and suggests plasmodial CAXs may be targeted in approaches designed to block parasite transmission.

【 授权许可】

CC BY