Amouzadeh H R, Bourdi M, Martin J L, Martin B M, Pohl L R
Molecular and Cellular Toxicology Section, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892-1760, USA.
Chem Res Toxicol. 1997 Jan;10(1):59-63. doi: 10.1021/tx9601364.
Halothane causes an idiosyncratic hepatitis that is thought to result, in part, from immune reactions against one or more lumenal endoplasmic reticulum (ER) proteins that have been covalently modified by the trifluoroacetyl chloride metabolite of halothane. In this study, we have identified a 170 kDa protein target of halothane in the liver of rats. The 170 kDa protein was first detected when proteins in lysates of hepatocytes from halothane-treated rats were immunoprecipitated with antisera against several resident ER proteins. This 170 kDa protein was found to be associated with other protein targets of halothane, including protein disulfide isomerase, a protein disulfide isomerase isoform, a 59 kDa carboxylesterase, and 78 kDa glucose-regulated protein. Immunoblotting with antiserum directed against the trifluoroacetylated hapten indicated that the 170 kDa protein was trifluoroacetylated. Based upon its subcellular localization, molecular mass, N-terminal amino acid sequence, and antigenicity, the trifluoroacetylated 170 kDa protein was identified as UDP-glucose:glycoprotein glucosyltransferase (UGGT), a lumenal ER protein that is thought to have a role in the folding of N-linked glycoproteins. Moreover, treatment of rats with halothane caused a 44% decrease in the activity of liver microsomal UGGT, and at least 36% of the change in the activity of the enzyme could be due to a decrease in the level of the protein. The results suggest that the function of UGGT in folding of N-linked glycoproteins may be affected by other resident ER proteins or xenobiotics such as halothane.
氟烷可引发一种特异质性肝炎，人们认为这部分是由于针对一种或多种内质网（ER）腔蛋白的免疫反应所致，这些蛋白已被氟烷的三氟乙酰氯代谢产物共价修饰。在本研究中，我们在大鼠肝脏中鉴定出了氟烷的一个170 kDa蛋白靶点。在用针对几种内质网驻留蛋白的抗血清对氟烷处理大鼠的肝细胞裂解物中的蛋白进行免疫沉淀时，首次检测到了这种170 kDa蛋白。发现这种170 kDa蛋白与氟烷的其他蛋白靶点相关，包括蛋白二硫键异构酶、一种蛋白二硫键异构酶同工型、一种59 kDa羧酸酯酶和78 kDa葡萄糖调节蛋白。用针对三氟乙酰化半抗原的抗血清进行免疫印迹表明，这种170 kDa蛋白被三氟乙酰化了。基于其亚细胞定位、分子量、N端氨基酸序列和抗原性，三氟乙酰化的170 kDa蛋白被鉴定为UDP-葡萄糖：糖蛋白葡糖基转移酶（UGGT），一种内质网腔蛋白，被认为在N-连接糖蛋白的折叠中起作用。此外，用氟烷处理大鼠会使肝脏微粒体UGGT的活性降低44%，并且该酶活性变化中至少36%可能是由于蛋白水平的降低。结果表明，UGGT在N-连接糖蛋白折叠中的功能可能会受到其他内质网驻留蛋白或异生素（如氟烷）的影响。
