Molecular Genetics of Cadmium Toxicity

描述（由申请人提供）：该项目的长期目标是确定和表征导致个体对镉（Cd）反应差异的基因。环境中的镉被小肠和肺吸收，与肝细胞中的金属硫蛋白和谷胱甘肽结合，并在肾脏中沉积。肾脏是人类和实验动物Cd暴露的主要靶器官。在目前的资助期内，我们确定Slc39a8基因是cd诱导睾丸坏死的Cdm位点。Slc39a8编码zip转运蛋白，我们发现这是一个高亲和力的顶端定向的流氓Cd/HCO3-共转运蛋白。ZIPS在培养物中的表达增加Cd内流，并使细胞对Cd敏感（30倍）。ZIPS以细胞类型特异性的方式表达，在肺和肾的肺泡上皮细胞和小管上皮细胞中分别表达最多。含有2 + 1个Slc39a8基因拷贝的bac转基因（BTZIP8）小鼠系在所有测试组织中显示出基因剂量依赖性的ZIPS mRNA增加，并且对cd诱导的肾功能异常敏感。Slc39a8是溶质载流子（SLC）金属转运体家族的14个成员之一；Slc39a14与Slc39a8具有最近的祖先；ZIP14作为两个多肽ZIP14A和ZIP14B存在，这是交替外显子剪接的结果。ZIP14s在小肠和肝脏中表达最高，具有与ZIPS相似的转运和毒理学特性。我们的假设是，zipps和ZIP14转运体是cd诱导肾功能障碍的主要介质。在下一个资助期，我们计划：b[1]在体外表征zipps、ZIP14A和ZIP14B的转运和生理特性；[2]利用我们的BTZIP8过表达者和Slc39a8（-/-）敲除小鼠模型研究ZIPS在cd诱导的肾功能障碍中的生理作用；这些研究将提高我们对重金属毒性的理解，并可能导致发现新的靶点，这些靶点可能对重金属疾病的预防策略和治疗干预有用。

DESCRIPTION (provided by applicant): The long-term goal of this project is to identify and characterize the gene(s) responsible for interindividual differences in response to cadmium (Cd). Environmental Cd is absorbed by the small intestine and lung, is bound to metallothionein and glutathione in hepatocytes, and is deposited in the kidney. The kidney is the major target organ for human and lab animal Cd exposure. During the current funding period, we identified the Slc39a8 gene as the Cdm locus responsible for Cd-induced testicular necrosis. Slc39a8 encodes the ZIPS transporter protein, which we show is a high-affinity apically-oriented rogue Cd/HCO3- cotransporter. ZIPS expression in culture increases Cd influx and sensitizes (>30-fold) the cells to Cd. ZIPS is expressed in a cell-type-specific manner and is highest in alveolar and tubular epithelial cells in the lung and kidney, respect- tively. A BAC-transgenic (BTZIP8) mouse line containing 2 + 1 additional copies of the Slc39a8 gene shows a gene-dose-dependent increase in ZIPS mRNA in all tissues tested, and is acutely sensitive to Cd-induced kidney dysfunction. Slc39a8 is one of 14 members of a solute-carrier (SLC) family of metal transporters; Slc39a14 shares the most recent ancestry with Slc39a8; ZIP14 exists as two peptides, ZIP14A and ZIP14B, as a consequence of alternate exon splicing. The ZIP14s are expressed highest in small intestine and liver and have transport and toxicologic properties similar to ZIPS. Our hypothesis is that the ZIPS and ZIP14 transporters are the principal mediators of Cd-induced renal dysfunction. For the next funding period, we propose to: [1] characterize the transport and physiological properties of ZIPS, ZIP14A and ZIP14B in vitro; [2] study the physiological role of ZIPS in Cd-induced renal dysfunction using our BTZIP8 overexpresser and Slc39a8(-/-) knockout mouse models; and [3] develop and characterize similar mouse models for Slc39a14 These studies will improve our understanding of heavy-metal toxicity and may lead to uncovering new targets that might be useful for preventive strategies as well as therapeutic intervention in heavy-metal diseases.