Molecular Genetics of Cadmium Toxicity

描述（由申请人提供）：本项目的长期目标是鉴定和表征负责镉（Cd）反应的个体间差异的基因。环境镉被小肠和肺吸收，与肝细胞中的金属硫蛋白和谷胱甘肽结合，并沉积在肾脏中。肾脏是人类和实验动物镉暴露的主要靶器官。在目前的资助期间，我们确定了Slc 39 a8基因作为Cdm基因座负责镉诱导的睾丸坏死。Slc 39 a8编码的ZIPS转运蛋白，我们发现这是一个高亲和力的顶端导向流氓镉/HCO 3-协同转运蛋白。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以细胞类型特异性方式表达，并且分别在肺和肾的肺泡和肾小管上皮细胞中表达最高。BAC转基因（BTZIP 8）小鼠系含有2 + 1额外的拷贝的Slc 39 a8基因显示基因剂量依赖性增加ZIPS mRNA在所有组织中测试，是急性敏感镉诱导的肾功能障碍。Slc 39 a8是金属转运蛋白的溶质载体（SLC）家族的14个成员之一; Slc 39 a14与Slc 39 a8共享最近的祖先; ZIP 14作为交替外显子剪接的结果以两种肽ZIP 14 A和ZIP 14 B存在。ZIP 14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，ZIPS和ZIP 14转运蛋白是镉诱导的肾功能不全的主要介质。对于下一个资助期，我们建议：[1]在体外表征ZIPS，ZIP 14 A和ZIP 14 B的转运和生理特性; [2]使用我们的BTZIP 8过表达和Slc 39 a8（-/-）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;和[3]开发和表征Slc 39 a14的类似小鼠模型。这些研究将提高我们对重-金属毒性，并可能导致发现新的目标，可能是有用的预防战略，以及重金属疾病的治疗干预。

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.