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（如乳腺和前列腺）如何在分泌期间重新分配细胞Zn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。前列腺锌转运功能障碍损害精子活力并与前列腺癌相关。这些观察强调需要了解锌在这些高度专业化的组织中的转运机制。锌转运蛋白-2（ZnT 2）的表达仅限于乳腺和前列腺等组织。ZnT 2的突变减少了人类向乳汁中的锌分泌，并且在体外乳腺上皮细胞中的ZnT 2抑制减少了锌分泌。已经鉴定了与乳腺上皮细胞中的线粒体（mZnT 2）和细胞内囊泡（sZnT 2）相关的离散ZnT 2同种型。线粒体锌吸收和锌浓度平行mZnT 2丰度，而锌分泌平行sZnT 2丰度。与前列腺细胞中的观察结果相似，激素催乳素改变了乳腺上皮细胞中的Zn分布。催乳素收缩线粒体锌池，同时增加锌转运。这种再分布与mZnT 2减少和sZnT 2丰度增加有关。我们假设，催乳素调节离散ZnT 2亚型重新分配细胞锌池从线粒体到分泌囊泡，以促进非凡的锌分泌高度专业化的分泌组织。我们建议使用乳腺作为一个代表性的系统，探索潜在的机制，负责细胞锌再分配使用动物和细胞模型。本申请的四个具体目的是：（1）使用基因组和蛋白质组学方法确定线粒体ZnT 2是否促进线粒体Zn库的扩增;（2）确定泌乳素通过分泌期间sZnT 2的变化重新分配细胞Zn库的机制;（3）开发转基因乳腺小鼠模型以确定细胞Zn库是否在体内被mZnT 2和sZnT 2重新分配;（4）建立ZnT 2基因敲除小鼠模型，研究ZnT 2基因的生物学意义，并确定是否有其他锌转运蛋白参与体内乳腺和前列腺锌库的再分布。总之，这些研究将确定在高度专业化的组织中调节细胞锌再分布的特定机制，对我们理解细胞功能，锌代谢和人类健康和疾病至关重要。乳腺和前列腺是高度特化的分泌组织，负责非凡的锌分泌。哺乳期间乳腺锌分泌受损导致严重的新生儿锌缺乏症，其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障碍与前列腺癌、精子活力和生殖功能受损有关。这些观察强调需要了解锌在这些独特的组织中的转运机制。因此，这种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。公共卫生相关性：乳腺和前列腺是高度专业化的分泌组织，负责非凡的锌分泌。哺乳期间乳腺锌分泌受损导致严重的新生儿锌缺乏症，其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障碍与前列腺癌、精子活力和生殖功能受损有关。这些观察强调需要了解锌在这些独特的组织中的转运机制。因此，这种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.