Dense granule trafficking in Toxoplasma gondii requires a unique class 27 myosin and actin filaments.
Dense granule trafficking in Toxoplasma gondii requires a unique class 27 myosin and actin filaments.
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DOI：
10.1091/mbc.e15-12-0824
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发表时间：
2016-07-01
影响因子：
3.3
通讯作者：
Warshaw DM
中科院分区：
文献类型：
--
作者：
Heaslip AT;Nelson SR;Warshaw DM
弓形虫在宿主细胞内的生存需要从囊泡中释放蛋白质，称为致密颗粒(DGs)。通过对活细胞内寄生虫DG运动的成像，表明DG的运输依赖于F-肌动蛋白和27类肌球蛋白TgMyoF，从而揭示了这些必需蛋白在寄生虫裂解周期中的新的关键作用。弓形虫在宿主细胞内的生存需要从被称为致密颗粒的分泌小泡中释放蛋白质，以维持寄生虫在细胞内的复制生态位。尽管DG很重要，但人们对其运输机制一无所知。在高等真核生物中，分泌囊泡通过其各自的细胞骨架轨迹(即微管和肌动蛋白)上的分子马达运输到质膜上。由于这些细胞骨架结构的组织在弓形虫中有很大的不同，DG运输对分子马达的依赖还远未确定。通过以高时空分辨率成像绿色荧光蛋白标记的DG在细胞内寄生虫中的运动，我们通过分子遗传学和化学扰动的组合表明，定向DG的运输不依赖于微管及其驱动蛋白/动力蛋白马达。然而，DG的定向运输依赖于丝状肌动蛋白和一种独特的27类肌球蛋白TgMyoF，它在结构上与典型的货物转运蛋白肌球蛋白V有相似之处。肌动球蛋白DG的转运是意想不到的，因为丝状寄生虫肌动蛋白还没有在体内被可视化，部分原因是寄生虫肌动蛋白形成短而不稳定的细丝的流行模型。因此，我们的数据揭示了这些关键蛋白在这种毁灭性病原体的裂解周期中的新的关键作用。
The survival of Toxoplasma gondii within its host cell requires protein release from vesicles, called dense granules (DGs). Through imaging of the motions of DGs in live intracellular parasites, it is shown that DG transport is dependent on F-actin and a class 27 myosin, TgMyoF, thus uncovering new critical roles for these essential proteins in the parasite’s lytic cycle. The survival of Toxoplasma gondii within its host cell requires protein release from secretory vesicles, called dense granules, to maintain the parasite’s intracellular replicative niche. Despite the importance of DGs, nothing is known about the mechanisms underlying their transport. In higher eukaryotes, secretory vesicles are transported to the plasma membrane by molecular motors moving on their respective cytoskeletal tracks (i.e., microtubules and actin). Because the organization of these cytoskeletal structures differs substantially in T. gondii, the molecular motor dependence of DG trafficking is far from certain. By imaging the motions of green fluorescent protein–tagged DGs in intracellular parasites with high temporal and spatial resolution, we show through a combination of molecular genetics and chemical perturbations that directed DG transport is independent of microtubules and presumably their kinesin/dynein motors. However, directed DG transport is dependent on filamentous actin and a unique class 27 myosin, TgMyoF, which has structural similarity to myosin V, the prototypical cargo transporter. Actomyosin DG transport was unexpected, since filamentous parasite actin has yet to be visualized in vivo due in part to the prevailing model that parasite actin forms short, unstable filaments. Thus our data uncover new critical roles for these essential proteins in the lytic cycle of this devastating pathogen.