Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, Indiana, USA.
Department of Biology, University of Findlay, Findlay, Ohio, USA.
mBio. 2020 Feb 11;11(1):e02732-19. doi: 10.1128/mBio.02732-19.
's single mitochondrion is very dynamic and undergoes morphological changes throughout the parasite's life cycle. During parasite division, the mitochondrion elongates, enters the daughter cells just prior to cytokinesis, and undergoes fission. Extensive morphological changes also occur as the parasite transitions from the intracellular environment to the extracellular environment. We show that treatment with the ionophore monensin causes reversible constriction of the mitochondrial outer membrane and that this effect depends on the function of the fission-related protein Fis1. We also observed that mislocalization of the endogenous Fis1 causes a dominant-negative effect that affects the morphology of the mitochondrion. As this suggests that Fis1 interacts with proteins critical for maintenance of mitochondrial structure, we performed various protein interaction trap screens. In this manner, we identified a novel outer mitochondrial membrane protein, LMF1, which is essential for positioning of the mitochondrion in intracellular parasites. Normally, while inside a host cell, the parasite mitochondrion is maintained in a lasso shape that stretches around the parasite periphery where it has regions of coupling with the parasite pellicle, suggesting the presence of membrane contact sites. In intracellular parasites lacking LMF1, the mitochondrion is retracted away from the pellicle and instead is collapsed, as normally seen only in extracellular parasites. We show that this phenotype is associated with defects in parasite fitness and mitochondrial segregation. Thus, LMF1 is necessary for mitochondrial association with the parasite pellicle during intracellular growth, and proper mitochondrial morphology is a prerequisite for mitochondrial division. is an opportunistic pathogen that can cause devastating tissue damage in the immunocompromised and congenitally infected. Current therapies are not effective against all life stages of the parasite, and many cause toxic effects. The single mitochondrion of this parasite is a validated drug target, and it changes its shape throughout its life cycle. When the parasite is inside a cell, the mitochondrion adopts a lasso shape that lies in close proximity to the pellicle. The functional significance of this morphology is not understood and the proteins involved are currently not known. We have identified a protein that is required for proper mitochondrial positioning at the periphery and that likely plays a role in tethering this organelle. Loss of this protein results in dramatic changes to the mitochondrial morphology and significant parasite division and propagation defects. Our results give important insight into the molecular mechanisms regulating mitochondrial morphology.
疟原虫的单个线粒体非常活跃，在整个寄生虫生命周期中经历形态变化。在寄生虫分裂过程中，线粒体伸长，在胞质分裂前进入子细胞，并发生分裂。当寄生虫从细胞内环境过渡到细胞外环境时，也会发生广泛的形态变化。我们表明，使用离子载体莫能菌素处理会导致线粒体外膜的可逆收缩，并且这种效应依赖于分裂相关蛋白 Fis1 的功能。我们还观察到，内源性 Fis1 的定位错误会产生显性负效应，从而影响线粒体的形态。由于这表明 Fis1 与维持线粒体结构的关键蛋白相互作用，我们进行了各种蛋白质相互作用捕获筛选。通过这种方式，我们鉴定了一种新的线粒体外膜蛋白 LMF1，它对于寄生虫体内定位至关重要。通常，在宿主细胞内，寄生虫的线粒体保持在套索形状，围绕寄生虫周围延伸，在那里它与寄生虫皮层有耦合区域，表明存在膜接触位点。在缺乏 LMF1 的寄生虫内，线粒体从皮层缩回，而是塌陷，这通常只在寄生虫中观察到。我们表明，这种表型与寄生虫适应性和线粒体分离缺陷有关。因此，在寄生虫体内生长过程中，LMF1 对于线粒体与寄生虫皮层的关联是必需的，而适当的线粒体形态是线粒体分裂的前提。 is 是一种机会性病原体，可在免疫功能低下和先天性感染的人中引起毁灭性的组织损伤。目前的治疗方法对寄生虫的所有生命阶段都没有效果，而且许多都会产生毒性作用。该寄生虫的单个线粒体是一个经过验证的药物靶点，并且在其生命周期中会改变形状。当寄生虫在细胞内时，线粒体呈套索形状，靠近皮层。这种形态的功能意义尚不清楚，目前也不知道涉及的蛋白质。我们已经鉴定出一种蛋白，该蛋白对于线粒体在边缘的正确定位是必需的，并且可能在固定该细胞器中起作用。该蛋白的缺失会导致线粒体形态发生剧烈变化，并导致寄生虫分裂和繁殖缺陷显著。我们的研究结果为调节线粒体形态的分子机制提供了重要的见解。
