Regulation of Mammalian Copper Homeotasis

描述（由申请人提供）：铜是一种必需的营养素。然而，尽管它对人类营养的重要性，很少有人知道哺乳动物细胞中的铜稳态调节机制。铜是几种重要的酶所必需的，然而，当浓度过高时，它也是有毒的。因此，铜稳态机制必须提供足够的铜来满足细胞的需要，同时防止这种营养物质的过度积累。哺乳动物细胞中的铜摄取通过跨膜蛋白hCtr 1发生。目前，我们对hCtr 1介导的铜摄取是否受不同铜可用性的调节知之甚少。相比之下，我们对哺乳动物细胞中铜的输出是如何调节的有更广泛的了解。两个铜ATP酶，ATP 7A和ATP 7 B，这是通常位于trans-Golgi网络，被刺激重新定位到细胞质囊泡或质膜的铜含量升高，以促进铜流出细胞质。在我们的初步研究中，我们表明，hCtr 1蛋白的位置是由铜浓度调节。高铜刺激hCtr 1从质膜的快速内吞作用，这与转运蛋白的降解有关。我们推测，这一过程可能是高亲和力铜吸收在哺乳动物细胞中调节的主要手段。然而，相关的分子机制和信号尚未确定。我们的长期目标是了解调节hCtr 1依赖性铜摄取的分子基础。为了实现这一总体目标，我们提出了以下具体目标：1.确定铜刺激hCtr 1的内吞和降解的细胞内途径。2.鉴定hCtr 1中对铜吸收、铜诱导的内吞作用和降解重要的氨基酸。3.评估hCtr 1的定位、内吞和降解是否对细胞内铜水平有反应。4.确定hCtr 1蛋白是否在一系列细胞类型中经历铜刺激的内吞作用和降解。我们的研究将极大地有助于了解细胞如何感知和响应铜可用性的变化。铜在阿尔茨海默病、朊病毒疾病和几种遗传疾病中的作用表明，对hCtr 1的研究可能对改善人类健康具有深远的意义。

DESCRIPTION (provided by applicant): Copper is an essential nutrient. However, despite its importance to human nutrition, little is known about the mechanisms regulating copper homeostasis in mammalian cells. Copper is required by several important enzymes, however, it is also toxic when present in excess concentrations. Thus, copper homeostasis mechanisms must supply sufficient copper to meet cellular needs, while preventing the over-accumulation of this nutrient. Copper uptake in mammalian cells occurs via the membrane-spanning protein, hCtr1. Currently, we have limited knowledge of whether hCtr1-mediated copper uptake is regulated in response to varying copper availability. In contrast, we have a more extensive knowledge of how copper export is regulated in mammalian cells. Two copper ATPases, ATP7A and ATP7B, which are normally located in the trans-Golgi network, are stimulated to relocate to cytoplasmic vesicles or the plasma membrane by elevated copper to facilitate copper efflux from the cytoplasm. In our preliminary studies, we show that the location of the hCtr1 protein is regulated by copper concentrations. Elevated copper stimulates the rapid endocytosis of hCtr1 from the plasma membrane, and this is associated with degradation of the transporter. We hypothesize that this process is likely to be the principle means by which high affinity copper uptake is regulated in mammalian cells. However, the underlying molecular mechanisms and signals involved have not yet been defined. Our long-term goal is to understand the molecular basis for regulating hCtr1-dependent copper uptake. To achieve this overall goal, we propose the following specific aims: 1.To define the intracellular pathway for copper-stimulated endocytosis and degradation of hCtr1. 2. To identify amino acids within hCtr1 important for copper uptake, copper-induced endocytosis and degradation. 3. To assess whether the localization, endocytosis and degradation of hCtr1 is responsive to intracellular copper levels. 4. To determine whether the hCtr1 protein undergoes copper-stimulated endocytosis and degradation in a range of cell types. Our research will contribute greatly to understanding how cells sense and respond to changes in copper availability. The implication of copper in Alzheimer's disease, prion diseases, and several genetic disorders, suggests the study of hCtr1 may have far-reaching implications for the improvement of human health.