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Sec1/Munc18(SM)蛋白 Vps45 参与致病性真菌新生隐球菌中铁的摄取、线粒体功能和毒力。

The Sec1/Munc18 (SM) protein Vps45 is involved in iron uptake, mitochondrial function and virulence in the pathogenic fungus Cryptococcus neoformans.

机构信息

Michael Smith Laboratories, Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada.

Department of Systems Biotechnology, Chung-Ang University, Anseong, Korea.

出版信息

PLoS Pathog. 2018 Aug 2;14(8):e1007220. doi: 10.1371/journal.ppat.1007220. eCollection 2018 Aug.

Abstract

The battle for iron between invading microorganisms and mammalian hosts is a pivotal determinant of the outcome of infection. The pathogenic fungus, Cryptococcus neoformans, employs multiple mechanisms to compete for iron during cryptococcosis, a disease primarily of immunocompromised hosts. In this study, we examined the role of endocytic trafficking in iron uptake by characterizing a mutant defective in the Sec1/Munc18 (SM) protein Vps45. This protein is known to regulate the machinery for vesicle trafficking and fusion via interactions with SNARE proteins. As expected, a vps45 deletion mutant was impaired in endocytosis and showed sensitivity to trafficking inhibitors. The mutant also showed poor growth on iron-limited media and a defect in transporting the Cfo1 ferroxidase of the high-affinity iron uptake system from the plasma membrane to the vacuole. Remarkably, we made the novel observation that Vps45 also contributes to mitochondrial function in that a Vps45-Gfp fusion protein associated with mitotracker, and a vps45 mutant showed enhanced sensitivity to inhibitors of electron transport complexes as well as changes in mitochondrial membrane potential. Consistent with mitochondrial function, the vps45 mutant was impaired in calcium homeostasis. To assess the relevance of these defects for virulence, we examined cell surface properties of the vps45 mutant and found increased sensitivity to agents that challenge cell wall integrity and to antifungal drugs. A change in cell wall properties was consistent with our observation of altered capsule polysaccharide attachment, and with attenuated virulence in a mouse model of cryptococcosis. Overall, our studies reveal a novel role for Vps45-mediated trafficking for iron uptake, mitochondrial function and virulence.

摘要

入侵微生物和哺乳动物宿主之间争夺铁的斗争是感染结局的关键决定因素。致病性真菌新生隐球菌在 cryptococcosis 期间会采用多种机制来争夺铁,cryptococcosis 主要发生在免疫功能低下的宿主中。在这项研究中,我们通过研究一种在 Sec1/Munc18 (SM) 蛋白 Vps45 缺陷的突变体来研究内吞作用在铁摄取中的作用。这种蛋白质已知通过与 SNARE 蛋白相互作用来调节囊泡运输和融合的机制。正如预期的那样,vps45 缺失突变体在胞吞作用中受损,并对运输抑制剂敏感。该突变体在缺铁培养基上的生长也较差,并且将高亲和力铁摄取系统的 Cfo1 亚铁氧化酶从质膜转运到液泡的能力也存在缺陷。值得注意的是,我们做出了一个新颖的观察,即 Vps45 也有助于线粒体功能,因为 Vps45-Gfp 融合蛋白与 mitotracker 相关联,并且 vps45 突变体对电子传递复合物抑制剂以及线粒体膜电位变化的敏感性增加。与线粒体功能一致,vps45 突变体在钙稳态中受损。为了评估这些缺陷对毒力的相关性,我们检查了 vps45 突变体的细胞表面特性,发现对挑战细胞壁完整性的试剂以及抗真菌药物的敏感性增加。细胞壁特性的改变与我们观察到的荚膜多糖附着改变一致,并且在 cryptococcosis 的小鼠模型中,毒力减弱。总的来说,我们的研究揭示了 Vps45 介导的运输在铁摄取、线粒体功能和毒力方面的新作用。

https://cdn.ncbi.nlm.nih.gov/pmc/blobs/993a/6091972/da50e3dfd49e/ppat.1007220.g001.jpg

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