弓形虫是一种常见的人畜共患原生动物病原体,适用于多种生物的许多宿主细胞中的细胞内寄生。我们以前的工作已经确定了18个由寄生虫基因组编码的环核苷酸磷酸二酯酶(PDE)蛋白,其中11在人类细胞中急性感染速殖子阶段的裂解周期中表达。这里,我们发现这些酶中的十种是混杂的双特异性磷酸二酯酶,水解cAMP和cGMP。TgPDE1和TgPDE9,Km为18μM和31μM,分别,准备水解cGMP,而TgPDE2对cAMP具有高度特异性(Km,14μM)。免疫电子显微镜显示TgPDE1,2和9的各种亚细胞分布,包括在内膜复合物中,顶极,质膜,胞质溶胶,致密颗粒,和rhoptry,指示速殖子内信号的空间控制。值得注意的是,尽管共同的顶端位置和双重催化,TgPDE8和TgPDE9对于裂解周期是完全可有可无的,并且不显示功能冗余。相比之下,TgPDE1和TgPDE2是最佳生长所必需的,它们的集体损失对寄生虫来说是致命的。这些突变体的体外表型分析揭示了TgPDE1和TgPDE2在增殖中的作用,滑翔运动,速殖子的入侵和出口。此外,我们的酶抑制试验与化学遗传表型相结合,支持TgPDE1作为常用PDE抑制剂的靶标,BIPPO和zaprinast。最后,我们鉴定了TgPDE1和TgPDE2相互作用激酶和磷酸酶的随从,可能调节酶的活性。总之,我们关于催化功能的数据集,生理相关性,关键磷酸二酯酶的亚细胞定位和药物抑制突出了弓形虫环核苷酸信号的先前未预期的可塑性和治疗潜力。
Toxoplasma gondii is a common zoonotic protozoan pathogen adapted to intracellular parasitism in many host cells of diverse organisms. Our previous work has identified 18 cyclic nucleotide phosphodiesterase (PDE) proteins encoded by the parasite genome, of which 11 are expressed during the lytic cycle of its acutely-infectious tachyzoite stage in human cells. Here, we show that ten of these enzymes are promiscuous dual-specific phosphodiesterases, hydrolyzing cAMP and cGMP. TgPDE1 and TgPDE9, with a Km of 18 μM and 31 μM, respectively, are primed to hydrolyze cGMP, whereas TgPDE2 is highly specific to cAMP (Km, 14 μM). Immuno-electron microscopy revealed various subcellular distributions of TgPDE1, 2, and 9, including in the inner membrane complex, apical pole, plasma membrane, cytosol, dense granule, and rhoptry, indicating spatial control of signaling within tachyzoites. Notably, despite shared apical location and dual-catalysis, TgPDE8 and TgPDE9 are fully dispensable for the lytic cycle and show no functional redundancy. In contrast, TgPDE1 and TgPDE2 are individually required for optimal growth, and their collective loss is lethal to the parasite. In vitro phenotyping of these mutants revealed the roles of TgPDE1 and TgPDE2 in proliferation, gliding motility, invasion and egress of tachyzoites. Moreover, our enzyme inhibition assays in conjunction with chemogenetic phenotyping underpin TgPDE1 as a target of commonly-used PDE inhibitors, BIPPO and zaprinast. Finally, we identified a retinue of TgPDE1 and TgPDE2-interacting kinases and phosphatases, possibly regulating the enzymatic activity. In conclusion, our datasets on the catalytic function, physiological relevance, subcellular localization and drug inhibition of key phosphodiesterases highlight the previously-unanticipated plasticity and therapeutic potential of cyclic nucleotide signaling in T. gondii.