Mammalian Zinc Transporters and Zinc Homeostasis

描述(申请人提供)：随着我们对酵母等模型生物中锌稳态的了解变得越来越详细，我们仍然对人类细胞中锌稳态的许多基本方面知之甚少。为了解决其中一些问题，我们将研究重点放在SLC39A13基因的产物Zip13上。Zip13是ZIP金属离子转运蛋白家族的成员。令人惊讶的是，SLC39A13的突变最近被发现导致一种形式的埃勒斯-丹洛斯综合征(EDS)，这是一种结缔组织疾病，由胶原修饰和组装缺陷引起。鉴于Zip13和EDS之间的这种有趣的联系，我们感兴趣的是金属离子转运蛋白是如何导致这种疾病的。在初步实验中，我们发现Zip13是一种锌特异的转运蛋白，定位于多种类型的人类细胞中的囊泡细胞器。这些囊泡的身份尚不清楚。我们提出的假设是，这些小泡是锌的储存场所，在缺锌条件下，Zip13负责将这些储存的锌从这些隔室中运输出来。我们进一步假设，在带有SLC39A13突变的EDS患者中看到的胶原组装缺陷是由于内质网锌缺乏造成的，这是由于锌被捕获在其存储细胞器中。为了验证这些假设，我们将a)评估Zip13对细胞锌稳态的影响，b)确定Zip13中断对ER功能、胶原羟化和ER锌状态的影响，以及c)确定Zip13是否共定位于锌小体，锌小体是锌储存的水泡位置。对这些目标的追求为评估囊泡性锌储存在哺乳动物锌稳态中的作用提供了一个独特的机会。Zip13可能提供了第一个分子把手，用来识别锌储存的细胞器位置并表征它们在哺乳动物细胞中的功能。 与公共健康相关：细胞内锌的运输和稳态过程对于基本的细胞功能、生理和人类健康是必不可少的。然而，尽管这很重要，我们仍然对涉及的特定转运蛋白以及它们如何在维持人类细胞锌稳态方面发挥作用知之甚少。这项建议的重点是Zip13，一种锌转运蛋白，最近与一些Ehler-Danlos综合征病例有关，以及该蛋白在控制锌的囊泡储存中所起的作用。

DESCRIPTION (provided by applicant): As our understanding of zinc homeostasis in model organisms such as yeast becomes increasingly detailed, we still know very little about many basic aspects of zinc homeostasis in human cells. To address some of these questions, we have focused our studies on Zip13, the product of the SLC39A13 gene. Zip13 is a member of the ZIP family of metal ion transporters. Surprisingly, mutations in SLC39A13 were recently identified as causing a form of Ehlers-Danlos Syndrome (EDS), a connective tissue disease that results from defects in collagen modification and assembly. Given this intriguing link between Zip13 and EDS, it was of interest to us how a metal ion transporter contributes to this disease. In preliminary experiments, we have found that Zip13 is a zinc-specific transporter that localizes to a vesicular organelle in a wide variety of human cell types. The identity of these vesicles is not yet known. We propose the hypothesis that these vesicles are storage sites for zinc and that Zip13 is responsible for transporting this stored zinc out of those compartments under conditions of zinc deficiency. We further hypothesize that the defects in collagen assembly seen in EDS patients with SLC39A13 mutations result from ER zinc deficiency due to the trapping of zinc within its storage organelle. To test these hypotheses, we will a) assess the impact of Zip13 on cellular zinc homeostasis, b) determine the effect of Zip13 disruption on ER function, collagen hydroxylation, and ER zinc status, and c) determine whether Zip13 co-localizes to the zincosome, a vesicular site of zinc storage. Pursuit of these aims provides a unique opportunity to assess the function of vesicular zinc storage in mammalian zinc homeostasis. Zip13 may provide the first molecular handle with which to identify the organellar sites of zinc storage and characterize their function in mammalian cells. PUBLIC HEALTH RELEVANCE: The processes of intracellular zinc transport and homeostasis are essential for basic cellular function, physiology, and human health. Despite this importance, however, we still know little about the specific transporter proteins involved and how they function in maintaining zinc homeostasis in human cells. This proposal is focused on Zip13, a zinc transporter recently linked to some cases of Ehlers-Danlos Syndrome, and the role this protein plays in controlling the vesicular storage of zinc.