Ca2+是一种普遍的细胞内信号,其调节许多细胞功能。在弓形虫中,细胞外和细胞内Ca2+控制流入胞质溶胶启动信号级联,促进组织破坏和传播等致病过程。在这项工作中,我们研究了质子转运在胞质Ca2+稳态和Ca2+信号启动中的作用。我们使用了V-H+-ATP酶的弓形虫突变体,先前显示的将质子传输到细胞外介质的泵,并控制细胞内的pH和膜电位,我们表明质子梯度对于将静止的胞浆Ca2维持在生理水平和Ca2流入很重要。质子运输对于酸性储存的Ca2+储存也很重要,出乎意料的是,内质网。质子迁移影响聚磷酸盐(polyP)的量,结合Ca2+并浓缩在酸钙中的磷酸盐聚合物。这得到了液泡转运蛋白伴侣4(VTC4)的共同定位的支持,合成polyP的VTC复合物的催化亚基,酸钙体中的V-ATPase。我们的工作表明,质子转运调节质膜Ca2转运并控制酸钙体polyP和Ca2含量,影响弓形虫的Ca2+信号和运动和外出的下游刺激。
Ca2+ is a universal intracellular signal that regulates many cellular functions. In Toxoplasma gondii, the controlled influx of extracellular and intracellular Ca2+ into the cytosol initiates a signaling cascade that promotes pathogenic processes like tissue destruction and dissemination. In this work, we studied the role of proton transport in cytosolic Ca2+ homeostasis and the initiation of Ca2+ signaling. We used a T. gondii mutant of the V-H+ -ATPase, a pump previously shown to transport protons to the extracellular medium, and to control intracellular pH and membrane potential and we show that proton gradients are important for maintaining resting cytosolic Ca2+ at physiological levels and for Ca2+ influx. Proton transport was also important for Ca2+ storage by acidic stores and, unexpectedly, the endoplasmic reticulum. Proton transport impacted the amount of polyphosphate (polyP), a phosphate polymer that binds Ca2+ and concentrates in acidocalcisomes. This was supported by the co-localization of the vacuolar transporter chaperone 4 (VTC4), the catalytic subunit of the VTC complex that synthesizes polyP, with the V-ATPase in acidocalcisomes. Our work shows that proton transport regulates plasma membrane Ca2+ transport and control acidocalcisome polyP and Ca2+ content, impacting Ca2+ signaling and downstream stimulation of motility and egress in T. gondii.