Regulation of Cellular Zn Redistribution: A Role of ZnT2

描述(申请人提供)：本申请的长期目标旨在确定乳腺和前列腺等对锌有特殊需求的组织如何在分泌过程中重新分配细胞锌池。哺乳期乳腺锌分泌受损导致新生儿严重缺锌。这会损害神经和行为发育，损害免疫功能，并增加婴儿发病率和/或死亡率。锌转运异常也与乳腺癌有关。前列腺锌转运功能障碍会损害精子存活率，并与前列腺癌有关。这些观察结果强调了了解锌在这些高度专业化的组织中的运输机制的必要性。锌转运蛋白-2(ZnT2)的表达仅限于乳腺和前列腺等组织。人类乳汁中锌的分泌减少，而乳房上皮细胞中的锌的分泌在体外也受到抑制。在乳腺上皮细胞中，已发现与线粒体(MZnT2)和细胞内小泡(SZnT2)相关的离散的ZnT2亚型。线粒体锌摄取和锌浓度与mZnT2丰度成正比，而锌分泌与sZnT2丰度成正比。与在前列腺细胞中观察到的相似，催乳素激素改变了乳腺上皮细胞中锌的分布。催乳素收缩线粒体锌库，同时增加锌的运输。这种重新分布与mZnT2的减少和sZnT2丰度的增加有关。我们推测，催乳素调节不同的ZnT2亚型，将细胞锌库从线粒体重新分配到分泌小泡，以促进高度专门化的分泌组织中非凡的锌分泌。我们建议使用乳腺作为一个代表性系统，通过动物和细胞模型来探索细胞内锌重新分布的潜在机制。本应用的四个具体目标是：(1)利用基因组和蛋白质组方法确定线粒体锌是否促进线粒体锌库的扩大；(2)确定催乳素通过在分泌过程中改变sZnT2来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mZnT2和sZnT2是否在体内进行了细胞锌库的重新分配；(4)建立锌转运蛋白缺失的小鼠模型，以记录ZnT2的生物学意义，并确定其他锌转运体是否参与了乳腺和前列腺中的锌库重新分配。综上所述，这些研究将确定在高度专业化的组织中调节细胞锌重新分布的特定机制，对于我们理解细胞功能、锌代谢以及人类健康和疾病至关重要。乳腺和前列腺癌是高度专门化的分泌组织，负责异常的锌分泌。哺乳期乳腺锌分泌受损导致新生儿严重缺锌，损害神经和行为发育，损害免疫功能，增加婴儿发病率和/或死亡率。锌转运异常也与乳腺癌有关。前列腺癌、精子存活率和生殖功能受损与前列腺癌、精子存活率和生殖功能受损有关。这些观察结果强调了了解锌在这些独特组织中的转运机制的必要性。因此，这一应用对于改善公共卫生结果和促进我们对基本细胞机制的理解具有重要意义。与公共健康相关：乳腺和前列腺是高度专业化的分泌组织，负责异常的锌分泌。哺乳期乳腺锌分泌受损导致新生儿严重缺锌，损害神经和行为发育，损害免疫功能，增加婴儿发病率和/或死亡率。锌转运异常也与乳腺癌有关。前列腺癌、精子存活率和生殖功能受损与前列腺癌、精子存活率和生殖功能受损有关。这些观察结果强调了了解锌在这些独特组织中的转运机制的必要性。因此，这一应用对于改善公共卫生结果和促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.