MECHANISM OF GLUTATHIONE CONJUGATE DEPENDENT TOXICITY

描述：(改编自《调查者摘要》)长期接触 三氯乙烯(TE)可致大鼠肾癌。二氯乙炔 (DA)是TE的分解产物，既有肾毒性，又有神经毒性。TE和 DA被代谢成谷胱甘肽(谷胱甘肽S结合物和半胱氨酸 S-结合物(=S-(1，2-二氯乙烯基)-L-半胱氨酸，DCVC)，有毒。 DCVC对S3肾单位节段造成选择性损伤；线粒体 很脆弱。半胱氨酸S偶联的β-裂解酶是吡哆醛 5‘-磷酸依赖酶将DCVC和类似化合物转化为 丙酮酸，氨和一种有毒的碎片。该碎片通过以下方式杀死肾脏细胞 与大分子反应，耗尽细胞硫醇，刺激 过氧化损伤。犬尿氨酸酶和胞浆谷氨酰胺转氨酶K (CytGTK)具有半胱氨酸S偶联β-裂解酶活性。然而， 犬尿氨酸酶被DCVC灭活，CytGTK裂解酶活力为 由α-酮酸支持，仅在体内以低水平存在。一次高潮 分子量(MR)多亚基裂解酶(最近由 研究人员)存在于S3节段和肾脏胞浆中 线粒体，并被生理水平的 α-酮戊二酸。因此，它可能是负责 用于选择性肾损伤。当前提案的目的是净化 大鼠肾细胞浆(和线粒体)高MR裂解酶的克隆和鉴定 对亚基进行排序。会产生抗体并用来确定 酶/亚基的细胞/亚细胞定位及其作用 该酶对肾脏的总β-裂解酶活性有影响。非洲爪哇的卵母细胞 将使用表达系统来确定每个元素的相对重要性 在全酶中，亚基到整体结构/催化功能。LLC-PK1 哺乳动物细胞中缺乏线粒体和异源表达的细胞 LINE应提供有用的工具来研究高MR酶在 谷胱甘肽/半胱氨酸S结合物的毒性。拟议的工作将提供 对高MR裂解酶与其他PLP酶的关系的洞察。 如果高MR裂解酶被证明是生物激活的主要因素 肾毒性结合物的结果将具有医学意义。TE是一种 常见污染物。严重暴露于TE(或类似物质)对人类的风险 化合物)可以通过抑制高MR裂解酶的方案来最小化。

DESCRIPTION: (Adapted from the Investigator's Abstract) Long-term exposure to trichloroethylene (TE) causes renal cancer in rats. Dichloroacetylene (DA), a breakdown product of TE, is both nephrotoxic and neurotoxic. TE and DA are metabolized to the glutathione (GSH S-conjugate and cysteine S-conjugate (= S-(1,2-dichlorovinyl)-L-cysteine, DCVC) which are toxic. DCVC causes selective damage to the S3 nephron segment; mitochondria are vulnerable. Cysteine S-conjugate beta-lyases are pyridoxal 5'-phosphate-dependent enzymes that convert DCVC and similar compounds to pyruvate, ammonia and a toxic fragment. The fragment kills renal cells by reacting with macromolecules, depleting cellular thiols and stimulating peroxidative damage. Kynureninase and cytosolic glutamine transaminase K (cytGTK) have cysteine S-conjugate beta-lyase activity. However, kynureninase is inactivated by DCVC and the lyase activity of cytGTK is supported by alpha-keto acids present in vivo only at low levels. A high molecular weight (Mr) multi-subunit lyase (recently discovered by the investigator) is present in the S3 segment and in kidney cytosol and mitochondria, and is inactivated by physiological levels of alpha-ketoglutarate. Therefore, it may be the principal enzyme responsible for selective renal damage. The aim of the current proposal is to purify the high Mr lyase from rat kidney cytosol (and mitochondria) and clone and sequence the subunits. Antibodies will be generated and used to determine the cellular/subcellular location of the enzyme/subunits and contribution of the enzyme to total beta-lyase activity of the kidney. The Xenopus oocyte expression system will be used to determine the relative importance of each subunit to overall structure/catalytic function in the holoenzyme. LLC-PK1 cells lacking mitochondria and heterologous expression in a mammalian cell line should provide useful tools to study the role of the high Mr enzyme in the toxicity of GSH-/cysteine S-conjugates. The proposed work will provide insights into the relationship of the high Mr lyase to other PLP enzymes. If the high Mr lyase is shown to be the principal agent for bioactivation of nephrotoxic conjugates the results will have medical importance. TE is a common pollutant. Risks to humans heavily exposed to TE (or similar compounds) may be minimized by regimens that inhibit the high Mr lyase.