Toxoplasma gondii is an obligate intracellular parasite and replicates inside a parasitophorous vacuole (PV) within the host cell. The membrane of the PV (PVM) contains pores that permits for equilibration of ions and small molecules between the host cytosol and the PV lumen. Ca²⁺ signaling is universal and both T. gondii and its mammalian host cell utilize Ca²⁺ signals to stimulate diverse cellular functions. Egress of T. gondii from host cells is an essential step for the infection cycle of T. gondii, and a cytosolic Ca²⁺ increase initiates a Ca²⁺ signaling cascade that culminates in the stimulation of motility and egress. In this work we demonstrate that intracellular T. gondii tachyzoites are able to take up Ca²⁺ from the host cytoplasm during host cell signaling events. Both intracellular and extracellular Ca²⁺ sources are important in reaching a threshold of parasite cytosolic Ca²⁺ needed for successful egress. Two peaks of Ca²⁺ were observed in egressing single parasites with the second peak resulting from Ca²⁺ entry. We patched infected host cells to allow the delivery of precise concentrations of Ca²⁺ for the stimulation of motility and egress. Using this approach of patching infected host cells, allowed us to determine that increasing the host cytosolic Ca²⁺ to a specific concentration can trigger egress, which is further accelerated by diminishing the concentration of potassium (K⁺).

刚地弓形虫是一种专性细胞内寄生虫，在宿主细胞内的寄生空泡 (PV) 内复制。PV (PVM) 的膜包含允许在宿主细胞质和 PV 腔之间平衡离子和小分子的孔。Ca ²⁺信号传导是普遍的，T. gondii及其哺乳动物宿主细胞都利用 Ca ²⁺信号来刺激不同的细胞功能。刚地弓形虫从宿主细胞中排出是刚地弓形虫感染周期的重要步骤，细胞溶质 Ca ²⁺的增加会引发 Ca ²⁺信号级联，最终刺激运动和出口。在这项工作中，我们证明了细胞内刚地弓形虫速殖子能够在宿主细胞信号传导事件期间从宿主细胞质中吸收 Ca ^{2+ 。}细胞内和细胞外 Ca ²⁺来源对于达到成功排出所需的寄生虫胞质 Ca ^{2+阈值都很重要。}在排出的单个寄生虫中观察到两个Ca ^{2+峰，第二个峰是由Ca 2+}进入引起的。我们修补了受感染的宿主细胞，以允许递送精确浓度的 Ca ²⁺用于刺激运动和出口。使用这种修补受感染宿主细胞的方法，使我们能够确定将宿主细胞溶质 Ca ²⁺增加到特定浓度可以触发排出，通过降低钾 (K ⁺ ) 的浓度进一步加速排出。