MavN is a Legionella pneumophila vacuole-associated protein required for efficient iron acquisition during intracellular growth
MavN is a Legionella pneumophila vacuole-associated protein required for efficient iron acquisition during intracellular growth
复制标题
DOI：
10.1073/pnas.1511389112
复制
发表时间：
2015-09-15
影响因子：
11.1
通讯作者：
Isberg, Ralph R.
中科院分区：
文献类型：
--
作者：
Isaac, Dervla T.;Laguna, Rita K.;Isberg, Ralph R.
铁对于大多数液泡内病原体的生长和毒力至关重要。微生物绕过宿主铁限制、穿过宿主液泡膜接触这种金属的机制尚不清楚。在这项工作中，我们确定了嗜肺军团菌使用的独特的细胞内铁获取策略。细菌 Icm/Dot（细胞内增殖/细胞器运输缺陷）IV 型分泌系统将细菌衍生的 MavN（允许液泡共定位的更多区域 N）蛋白靶向含军团菌的液泡表面，该跨膜蛋白促进液泡内铁的获取。 Delta mavN 突变体在巨噬细胞感染的早期阶段，其生长停止之前表现出转录铁饥饿特征。这种细胞内生长缺陷只能通过向培养基中添加过量的外源铁而不是各种其他金属来挽救。与 MavN 是一种在细胞内生长过程中发挥独特作用的易位底物一致，该突变体在肉汤培养物中没有表现出生长缺陷，即使在严重的铁限制条件下也是如此。鉴定了 MavN 蛋白内推定的铁结合残基，这些残基的点突变导致了细胞内生长特异的缺陷，与 Delta mavN 突变体无法区分。这种细菌蛋白插入宿主膜介导铁转运的模型为液泡内病原体如何利用毒力相关的分泌系统来操纵和获取宿主铁提供了范例。
Iron is essential for the growth and virulence of most intravacuolar pathogens. The mechanisms by which microbes bypass host iron restriction to gain access to this metal across the host vacuolar membrane are poorly characterized. In this work, we identify a unique intracellular iron acquisition strategy used by Legionella pneumophila. The bacterial Icm/Dot (intracellular multiplication/defect in organelle trafficking) type IV secretion system targets the bacterial-derived MavN (more regions allowing vacuolar colocalization N) protein to the surface of the Legionella-containing vacuole where this putative transmembrane protein facilitates intravacuolar iron acquisition. The Delta mavN mutant exhibits a transcriptional iron-starvation signature before its growth is arrested during the very early stages of macrophage infection. This intracellular growth defect is rescued only by the addition of excess exogenous iron to the culture medium and not a variety of other metals. Consistent with MavN being a translocated substrate that plays an exclusive role during intracellular growth, the mutant shows no defect for growth in broth culture, even under severe iron-limiting conditions. Putative iron-binding residues within the MavN protein were identified, and point mutations in these residues resulted in defects specific for intracellular growth that are indistinguishable from the Delta mavN mutant. This model of a bacterial protein inserting into host membranes to mediate iron transport provides a paradigm for how intravacuolar pathogens can use virulence-associated secretion systems to manipulate and acquire host iron.