Regulation of Cellular Zn Redistribution: A Role of ZnT2

描述（由申请人提供）：本申请的长期目标旨在确定具有特殊锌（Zn）需求的组织（例如乳腺和前列腺）在分泌过程中如何重新分配细胞锌库。哺乳期间乳腺锌分泌受损会导致新生儿严重缺锌。这会损害神经元和行为发育，损害免疫功能，并增加婴儿发病率和/或死亡率。异常的锌转运也与乳腺癌有关。前列腺锌转运功能失调会损害精子活力，并与前列腺癌相关。这些观察结果强调需要了解这些高度特化组织中的锌转运机制。锌转运蛋白 2 (ZnT2) 的表达仅限于乳腺和前列腺等组织。 ZnT2 的突变会减少人类乳汁中锌的分泌，而乳腺上皮细胞中 ZnT2 的抑制会减少体外锌的分泌。已鉴定出与乳腺上皮细胞中的线粒体 (mZnT2) 和细胞内囊泡 (sZnT2) 相关的离散 ZnT2 亚型。线粒体 Zn 吸收和 Zn 浓度与 mZnT2 丰度平行，而 Zn 分泌与 sZnT2 丰度平行。与前列腺细胞中的观察结果类似，催乳素激素会改变乳腺上皮细胞中锌的分布。催乳素收缩线粒体锌库，同时增加锌转运。这种重新分布与 mZnT2 减少和 sZnT2 丰度增加有关。我们假设催乳素调节离散的 ZnT2 亚型，将细胞锌库从线粒体重新分配到分泌囊泡，以促进高度专业化的分泌组织中大量的锌分泌。我们建议使用乳腺作为代表性系统，利用动物和细胞模型探索负责细胞锌重新分配的潜在机制。本申请的四个具体目标是：(1) 使用基因组和蛋白质组学方法确定线粒体 ZnT2 是否有助于线粒体 Zn 库的扩展； (2) 确定催乳素通过分泌过程中 sZnT2 的变化重新分配细胞锌库的机制； (3) 建立转基因乳腺小鼠模型，以确定细胞锌库是否在体内通过 mZnT2 和 sZnT2 重新分配； (4)开发ZnT2缺失小鼠模型来记录ZnT2的生物学意义并确定其他Zn转运蛋白是否参与体内乳腺和前列腺中Zn库的重新分配。总而言之，这些研究将确定调节高度特化组织中细胞锌重新分布的具体机制，对于我们了解细胞功能、锌代谢以及人类健康和疾病至关重要。乳腺和前列腺是高度专业化的分泌组织，负责大量的锌分泌。哺乳期间乳腺锌分泌受损会导致新生儿严重缺锌，从而损害神经元和行为发育，损害免疫功能，并增加婴儿发病率和/或死亡率。异常的锌转运也与乳腺癌有关。前列腺中锌转运功能失调与前列腺癌、精子活力和生殖功能受损有关。这些观察结果强调了了解这些独特组织中锌转运机制的必要性。因此，该应用对于改善公共卫生结果和增进我们对基本细胞机制的理解具有重要意义。公众健康相关性：乳腺和前列腺是高度专业化的分泌组织，负责大量的锌分泌。哺乳期间乳腺锌分泌受损会导致新生儿严重缺锌，从而损害神经元和行为发育，损害免疫功能，并增加婴儿发病率和/或死亡率。异常的锌转运也与乳腺癌有关。前列腺中锌转运功能失调与前列腺癌、精子活力和生殖功能受损有关。这些观察结果强调了了解这些独特组织中锌转运机制的必要性。因此，该应用对于改善公共卫生结果和增进我们对基本细胞机制的理解具有重要意义。

DESCRIPTION (provided by applicant): The long-term goal of this application aims to determine how tissues with extraordinary zinc (Zn) requirements, such as mammary gland and prostate, redistribute cellular Zn pools during secretion. Impaired Zn secretion from the mammary gland during lactation results in severe neonatal Zn deficiency. This compromises neuronal and behavioral development, impairs immune function, and increases infant morbidity and/or mortality. Aberrant Zn transport is also implicated in breast cancer. Dysfunctional prostate Zn transport impairs sperm viability and is associated with prostate cancer. These observations underscore the need to understand Zn transport mechanisms in these highly specialized tissues. Zinc transporter-2 (ZnT2) expression is restricted to tissues such as mammary gland and prostate. A mutation in ZnT2 reduces Zn secretion into milk in humans and ZnT2-suppression in mammary epithelial cells reduces Zn secretion in vitro. Discrete ZnT2 isoforms have been identified which are associated with mitochondria (mZnT2) and intracellular vesicles (sZnT2) in mammary epithelial cells. Mitochondrial Zn uptake and Zn concentration parallels mZnT2 abundance, while Zn secretion parallels sZnT2 abundance. Similar to observations in prostate cells, the hormone prolactin shifts Zn distribution in mammary epithelial cells. Prolactin contracts mitochondrial Zn pools while concurrently increasing Zn transport. This redistribution is associated with decreased mZnT2 and increased sZnT2 abundance. We hypothesize that prolactin regulates discrete ZnT2 isoforms to redistribute cellular Zn pools from mitochondria to secretory vesicles to facilitate extraordinary Zn secretion in highly specialized secretory tissues. We propose to use the mammary gland as a representative system to explore potential mechanisms responsible for cellular Zn redistribution using animal and cell models. The four specific aims of this application are to, (1) determine if mitochondrial ZnT2 facilitates expansion of a mitochondrial Zn pool using genomic and proteomic approaches; (2) determine mechanisms by which prolactin redistributes cellular Zn pools through changes in sZnT2 during secretion; (3) develop a transgenic mammary gland mouse model to determine if cellular Zn pools are redistributed by mZnT2 and sZnT2 in vivo; (4) develop a ZnT2-null mouse model to document the biological significance ZnT2 and determine if other Zn transporters participate in Zn pool redistribution in mammary gland and prostate in vivo. Taken together, these studies will identify specific mechanisms which regulate cellular Zn redistribution in highly specialized tissues and are crucial to our understanding of cellular function, Zn metabolism and human health and disease. The mammary and prostate glands are highly specialized secretory tissues that are responsible for extraordinary Zn secretion. Impaired Zn secretion from the mammary gland during lactation results in severe neonatal Zn deficiency which compromises neuronal and behavioral development, impairs immune function, and increases infant morbidity and/or mortality. Aberrant Zn transport is also implicated in breast cancer. Dysfunctional Zn transport in prostate has been implicated in prostate cancer, sperm viability and impaired reproductive function. These observations underscore the need to understand Zn transport mechanisms in these unique tissues. Thus, this application has significance for improving public health outcomes and advancing our understanding of basic cellular mechanisms. PUBLIC HEALTH RELEVANCE: The mammary and prostate glands are highly specialized secretory tissues that are responsible for extraordinary Zn secretion. Impaired Zn secretion from the mammary gland during lactation results in severe neonatal Zn deficiency which compromises neuronal and behavioral development, impairs immune function, and increases infant morbidity and/or mortality. Aberrant Zn transport is also implicated in breast cancer. Dysfunctional Zn transport in prostate has been implicated in prostate cancer, sperm viability and impaired reproductive function. These observations underscore the need to understand Zn transport mechanisms in these unique tissues. Thus, this application has significance for improving public health outcomes and advancing our understanding of basic cellular mechanisms.