The genetically encoded calcium indicator GCaMP3 reveals spontaneous calcium oscillations at asexual stages of the Plasmodium falciparum parasite

Abstract text

Introduction - Calcium ions (Ca²⁺) are versatile intracellular messengers capable of regulating different cellular functions. Oscillations in cytosolic Ca²⁺ concentrations activate essential mechanisms for the survival of Plasmodium falciparum. Objectives - The protocols used to study the dynamics of Ca²⁺ in the malaria parasite are based on the dyes, which are invasive and do not allow discrimination between the signal from the host cell and the parasite. We have developed the PfGCaMP3 parasites, an innovative strain and tool for studying spontaneous intracellular Ca²⁺ oscillations without external markers. Materials & methods - Using the PfGCaMP3 strain, visualized on a Nikon Ti2-E real-time fluorescence microscope, we demonstrated the occurrence of spontaneous Ca²⁺ oscillations in the human malaria-causing parasite Plasmodium falciparum during intraerythrocytic phases: ring, trophozoite and schizont. Results - To verify the changes in the fluorescence of the GCaMP3 construct, indicative of cytosolic Ca²⁺ fluctuations, we used the Fourier transform, which was applied to the fluorescence intensity data extracted from different experiments. Thus, it was possible to verify that spontaneous cytosolic Ca²⁺ oscillations occur in the three intraerythrocytic stages of the parasite, with most oscillations occurring in the ring and trophozoite stages. Conclusion - This tool is promising for studying pharmacological compounds that may interfere with calcium dynamics in P. falciparum.