Copper Homeostasis in Mammals

铜是从饮食中获得的一种必不可少的痕量金属，它是一种催化剂 在生命中起关键作用的各种酶反应的辅因子。铜缺乏 导致病理生理表现包括铁吸收受损，中性粒细胞减少， 认知缺陷、周围神经病和肥厚型心肌病。了解 铜在细胞和组织中积累的机制，铜的调节 蓄积，以及铜摄取失调造成的后果对 人类健康。 CTR1是哺乳动物中唯一已知的铜离子进口体，而CTR1在 饮食和外周铜的获取、胚胎发育、心脏功能和正常 在生长过程中，对调节CTR1活性的机制知之甚少。CTR1既以 全长蛋白并且作为缺少胞外铜结合结构域的截短形式(TCtr1)， 这降低了铜的吸收活性。我们鉴定了组织蛋白酶是一种执行 在CTR1胞外结构域切割中的限速步骤，并证明了这种切割是 受Ctr2整合膜蛋白刺激。在大心脏的患者中 在导尿术临床队列中，我们在人类中发现了单核苷酸多态(SNP) CTR1基因主要发生在非裔美国人中，导致该基因的超切割 CTR1铜结合胞外结构域，细胞铜摄取减少。 在这里，我们详细地进行实验，以验证CTR1胞外结构域切割， 通过组织蛋白酶L/B蛋白和铜反应的CTR2水平，是一个关键 哺乳动物铜摄取的调控机制。我们的实验将发现新的 哺乳动物体内铜组分的动态平衡，破译了一种新的铜- 依赖蛋白分解，生成新的动物模型，并验证缺陷之间的联系 非洲人CTR1胞外结构域裂解、铜缺乏与肥厚型心肌病 美国人。

Copper (Cu) is an essential trace metal that is acquired from the diet and serves as a catalytic co-factor for a wide variety of enzymatic reactions that play critical roles in life. Cu deficiency leads to pathophysiological manifestations including impaired iron absorption, neutropenia, cognitive defects, peripheral neuropathy and hypertrophic cardiomyopathy. Understanding the mechanisms responsible for the accumulation of Cu in cells and tissues, the regulation of Cu accumulation, and the consequences due to dysregulated Cu acquisition are important to human health. Ctr1 is the only known Cu+ importer in mammals and while Ctr1 plays an essential role in dietary and peripheral Cu acquisition, embryonic development, cardiac function and normal growth, little is known about the mechanisms that regulate Ctr1 activity. Ctr1 exists both as a full-length protein and as a truncated form (tCtr1) lacking the extracellular Cu binding domain, which has reduced Cu uptake activity. We identified cathepsin as a protease that carries out the rate-limiting step in Ctr1 ecto-domain cleavage and demonstrated that this cleavage is stimulated by the Ctr2 integral membrane protein. Among patients in a large cardiac catheterization clinic cohort, we identified a single nucleotide polymorphism (SNP) in the human Ctr1 gene that occurs predominantly in African Americans, resulting in hyper-cleavage of the Ctr1 Cu-binding ecto-domain and decreased cellular Cu acquisition. Here we detail experiments to test the hypothesis that Ctr1 ecto-domain cleavage, through the cathepsin L/B proteases and Cu-responsive Ctr2 levels, is a critical regulatory mechanism for mammalian Cu acquisition. Our experiments will identify new components in mammalian Cu homeostasis, decipher a new mechanism for Cu- dependent proteolysis, generate a new animal model and validate a link between a defect in Ctr1 ecto-domain cleavage, Cu deficiency and hypertrophic cardiomyopathy in African Americans.