ZIP8: A Metal Transporter with Pathophysiologic Roles in the Lung, Spleen, and Placenta

ZIP8是二价金属通过细胞膜和从亚细胞区室进入胞质空间的跨膜输入物。虽然GWAS数据暗示功能减退的ZIP8突变在无数的严重的病理，有一个机制的研究，调查其功能在稳态或病理条件的缺乏。我们已经创建了两种新的ZIP8敲除（KO）小鼠模型，以研究这种转运蛋白，诱导型全身KO和肺上皮特异性KO，我们的初步数据表明，ZIP8在肺宿主免疫，脾铁再循环和胎盘营养转运中的重要作用。具体目标1。定义ZIP8作为金属转运蛋白在肺部感染免疫反应中的功能。ZIP8在肺中的表达高于任何其他器官系统，但其生物学功能尚不清楚。我们的初步数据表明，肺ZIP8主要位于肺泡上皮细胞，在那里它进口铁从肺泡腔，上调与炎症刺激和革兰氏阴性细菌感染，是重要的诱导的抗氧化酶锰超氧化物歧化酶的脂多糖（LPS）。我们将使用放射性金属示踪剂表征ZIP8介导的Fe，Zn和Mn在稳态和LPS肺损伤期间的转运，并研究ZIP8对革兰氏阴性细菌和真菌肺部感染结果的影响。具体目标2。定义ZIP8在脾巨噬细胞吞噬红细胞和铁再循环中的作用。我们的初步数据表明，脾脏ZIP8主要在巨噬细胞中表达，ZIP8缺失诱导红髓巨噬细胞内的脾脏铁螯合和血清铁限制，脾脏ZIP8表达受脾脏铁水平调节。我们将确定脾脏巨噬细胞内ZIP8的位置、活性和调节。使用改变铁处理与铁过载，铁缺乏和溶血的小鼠模型，我们还将表征ZIP8在基线稳态和应激期间的铁再循环中的功能。具体目标3。定义ZIP8对胎盘中母胎营养转运的贡献。胎盘是人类中第二高的ZIP8表达组织类型，并且小鼠中的整体ZIP8消融是胚胎致死的。我们的初步数据显示，胎盘ZIP8在合体滋养层细胞中表达，表明ZIP8在营养金属从母体循环到胚胎的运输中起关键作用。我们将使用一种新的滋养层特异性ZIP8基因敲除小鼠来确定ZIP8在胎盘转运铁、锌和锰中的作用，使用原代人滋养层细胞进行验证性研究，并研究母体铁状态对ZIP8的调节。我们的建议将回答这个关键的金属转运蛋白在金属介导的肺宿主免疫，脾铁再循环和胎盘运输营养金属的病理生理功能的基本问题。这些发现将为我们诊断和管理与金属稳态破坏相关的许多病理学的临床方法提供信息。

ZIP8 is a transmembrane importer of divalent metals into the cytosolic space through the cell membrane and from subcellular compartments. Although GWAS data implicate hypofunctional ZIP8 mutations in a myriad of serious pathologies, there is a paucity of mechanistic studies investigating its functions during homeostasis or pathologic conditions. We have created two novel ZIP8 knockout (KO) mouse models in order to study this transporter, an inducible whole-body KO and a lung epithelium-specific KO, and our preliminary data indicate significant roles of ZIP8 in lung host immunity, splenic iron recycling, and placental nutrient transport. Specific Aim 1. Define the functions of ZIP8 as a metal transporter in the immune response to lung infections. ZIP8 expression is higher in the lung than in any other organ system, but its biological function is unknown. Our preliminary data show that lung ZIP8 is located primarily in the alveolar epithelium, where it imports iron from the alveolar space, is upregulated with both inflammatory stimuli and gram-negative bacterial infection, and is important for induction of the antioxidant enzyme manganese superoxide dismutase by lipopolysaccharide (LPS). We will characterize ZIP8-mediated transport of Fe, Zn, and Mn during both homeostasis and LPS lung injury using radioactive metal tracers, and study the effects of ZIP8 on the outcomes of gram-negative bacterial and fungal lung infections. Specific Aim 2. Define the role of ZIP8 in splenic macrophage erythrophagocytosis and iron recycling. Our preliminary data show that spleen ZIP8 is primarily expressed in macrophages, ZIP8 deletion induces splenic iron sequestration within red pulp macrophages and serum iron restriction, and spleen ZIP8 expression is regulated by splenic iron levels. We will identify the location, activity, and regulation of ZIP8 within splenic macrophages. Using mouse models of altered iron handling with iron overload, iron deficiency, and hemolysis, we will also characterize the function of ZIP8 in iron recycling during both baseline homeostasis and stress. Specific Aim 3. Define the contribution of ZIP8 to maternal-fetal nutrient transport in the placenta. The placenta is the second highest ZIP8-expressing tissue type in humans, and global ZIP8 ablation in mice is embryonic lethal. Our preliminary data show that placental ZIP8 is expressed in syncytiotrophoblasts, indicating a key role of ZIP8 in the transport of nutrient metals from maternal circulation to the embryo. We will use a novel trophoblast specific ZIP8 KO mouse to define the role of ZIP8 in placental transport of Fe, Zn, and Mn, perform confirmatory studies using primary human trophoblasts, and investigate ZIP8 regulation by maternal iron status. Our proposal will answer fundamental questions about the pathophysiologic functions of this critical metal transporter in metal-mediated lung host immunity, splenic iron recycling, and placental transport of nutrient metals. The findings will inform our clinical approaches in diagnosing and managing the many pathologies associated with disrupted metal homeostasis.