Cruz-Mirón Rosalba, Pandey Namita, Alexandros Katelas Dimitrios, Kuchipudi Arunakar, Sriram Dharmarajan, Gangopadhyay Aditi, Chakraborti Soumyananda, Srivastav Ratnesh Kumar, Gupta Nishith
Intracellular Parasite Education and Research Labs (iPEARL), Department of Biological Sciences, Birla Institute of Technology and Science, Pilani (BITS Pilani), Hyderabad, India.
Department of Molecular Parasitology, Faculty of Life Sciences, Humboldt University, Berlin, Germany.
Commun Biol. 2025 May 6;8(1):702. doi: 10.1038/s42003-025-08058-z.
Toxoplasma gondii is a common intracellular pathogenic protist causing acute and chronic infections in many warm-blooded organisms. Calcium homeostasis is pivotal for its asexual reproduction in mammalian host cells, and sarcoendoplasmic reticulum calcium-ATPase (SERCA) is considered vital for maintaining ion homeostasis within the parasite. This work studied the physiological relevance, structure-function relationship, mechanism, and therapeutic value of SERCA in the acutely-infectious tachyzoite stage of T. gondii. A conditional depletion of SERCA, located in the endoplasmic reticulum, by auxin-inducible degradation is lethal for the parasite due to severe defects in its replication, gliding motility, and invasion. The observed phenotypes are caused by dysregulated calcium ion homeostasis and microneme secretion in the absence of TgSERCA. Furthermore, ectopic expression of TgSERCA restored the lytic cycle of a phosphatidylthreonine-null and phosphatidylserine-enriched mutant with perturbed calcium homeostasis, motility and invasion. These lipids are expressed in the parasite ER, co-localizing with TgSERCA. Last but not least, the structure-function modeling and ligand docking of TgSERCA with a library comprising >5000 chemicals identified two compounds (RB-15, NR-301) that inhibited the lytic cycle by affecting the tachyzoite locomotion, invasion, microneme discharge, and calcium levels. In conclusion, we demonstrate TgSERCA as an indispensable lipid-assisted calcium pump in T. gondii and report small molecules with therapeutic potential against toxoplasmosis.
刚地弓形虫是一种常见的细胞内致病原生生物，可在许多温血动物体内引发急性和慢性感染。钙稳态对其在哺乳动物宿主细胞中的无性繁殖至关重要，而肌浆内质网钙ATP酶（SERCA）被认为对维持寄生虫体内的离子稳态至关重要。这项研究探讨了SERCA在刚地弓形虫急性感染速殖子阶段的生理相关性、结构-功能关系、作用机制及治疗价值。通过生长素诱导降解有条件地耗尽内质网中的SERCA，会导致寄生虫因复制、滑行运动和入侵严重缺陷而死亡。观察到的表型是由于缺乏TgSERCA时钙离子稳态失调和微线体分泌异常所致。此外，TgSERCA的异位表达恢复了钙稳态、运动和入侵受到干扰的磷脂酰苏氨酸缺失和磷脂酰丝氨酸富集突变体的裂解周期。这些脂质在寄生虫内质网中表达，与TgSERCA共定位。最后，对TgSERCA与一个包含5000多种化学物质的文库进行结构-功能建模和配体对接，确定了两种化合物（RB-15、NR-301），它们通过影响速殖子运动、入侵、微线体释放和钙水平来抑制裂解周期。总之，我们证明了TgSERCA是刚地弓形虫中不可或缺的脂质辅助钙泵，并报道了具有抗弓形虫病治疗潜力的小分子。
