Department of Molecular Microbiology, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO 63110, USA.
Department of Molecular Microbiology, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO 63110, USA.
Cell Host Microbe. 2018 Dec 12;24(6):804-816.e6. doi: 10.1016/j.chom.2018.10.015. Epub 2018 Nov 15.
Apicomplexan parasites rely on cyclic nucleotide-dependent kinases for host cell infection, yet the mechanisms that control their activation remain unknown. Here we show that an apically localized guanylate cyclase (GC) controls microneme secretion and lytic growth in the model apicomplexan Toxoplasma gondii. Cell-permeable cGMP reversed the block in microneme secretion seen in a knockdown of TgGC, linking its function to production of cGMP. TgGC possesses an N-terminal P-type ATPase domain fused to a C-terminal heterodimeric guanylate cyclase domain, an architecture found only in Apicomplexa and related protists. Complementation with a panel of mutants revealed a critical requirement for the P-type ATPase domain for maximum GC function. We further demonstrate that knockdown of TgGC in vivo protects mice from lethal infection by blocking parasite expansion and dissemination. Collectively, this work demonstrates that cGMP-mediated signaling in Toxoplasma relies on a multi-domain architecture, which may serve a conserved role in related parasites.
顶复门寄生虫依赖环核苷酸依赖的激酶来感染宿主细胞，但控制其激活的机制尚不清楚。在这里，我们表明，一种位于顶端的鸟苷酸环化酶（GC）控制着模型顶复门生物弓形虫中的微线体分泌和裂解生长。可渗透细胞的 cGMP 逆转了 TgGC 敲低时观察到的微线体分泌受阻，将其功能与 cGMP 的产生联系起来。TgGC 具有一个 N 端 P 型 ATP 酶结构域融合到 C 端异二聚体鸟苷酸环化酶结构域，这种结构仅存在于顶复门生物和相关原生动物中。用一组突变体进行互补实验表明，P 型 ATP 酶结构域对于最大 GC 功能至关重要。我们进一步证明，体内敲低 TgGC 可通过阻止寄生虫的扩张和传播来保护小鼠免受致命感染。总的来说，这项工作表明，弓形虫中的 cGMP 介导的信号转导依赖于一种多结构域架构，这可能在相关寄生虫中发挥保守作用。
