Chang M, Burgess J R, Scholz R W, Reddy C C
Department of Veterinary Science and Environmental Resources Research Institute, Pennsylvania State University, University Park 16802.
J Biol Chem. 1990 Apr 5;265(10):5418-23.
We have reported previously that a dietary deficiency in selenium results in an increase in glutathione S-transferase (GST) activity of various rat tissues. In order to verify that the increased GST activity observed in a selenium deficiency results from increased synthesis of GST protein, cytosolic fractions of livers obtained from rats fed selenium-deficient and selenium-supplemented diets were analyzed by Western (protein) blots. Antisera raised against purified individual GST subunits (Ya, Yb, and Yc) were used to detect the corresponding subunits on the blots. The Ya subunit was induced 2.5-fold in the selenium-deficient state. The amount of Yc subunit also increased significantly (p less than 0.05) in selenium deficiency but not to the extent of the Ya subunit. The Yb subunit was not significantly affected by altered selenium nutritional status. A corresponding increase in poly(A) RNAs coding for the Ya and Yc subunits was also observed by Northern blot analysis. Transcriptional activity of GST YaYc genes was elevated by approximately 2-fold in purified nuclei isolated from selenium-deficient rat livers, which is sufficient to account for the increase in YaYc mRNA levels. Therefore, it appears that transcriptional activation of rat liver YaYc genes is the primary cause for the elevation of the corresponding gene products in the selenium-deficient state. Since the GSTs, especially the isozymes containing Ya subunit, have been implicated in the formation of prostaglandin (PG) F2 alpha, we investigated the effect of selenium deficiency on the PGF2 alpha-forming activity using a specific inhibitor of GSTs, S-decyl-GSH. In rats fed a nutritionally adequate diet, the activity inhibited by S-decyl-GSH accounted for at least half of the conversion of PGH2 to PGF2 alpha. During selenium deficiency, this GST-catalyzed activity was approximately doubled with no change in PGF2 alpha formation by other pathways, resulting in a 2-fold increase in overall synthesis of PGF2 alpha. These data strongly support a role of GSTs, especially those composed of the Ya size subunit, in the synthesis of PGF2 alpha from PGH2.
我们之前报道过，膳食中硒缺乏会导致各种大鼠组织中谷胱甘肽S-转移酶（GST）活性增加。为了验证在硒缺乏状态下观察到的GST活性增加是否源于GST蛋白合成增加，我们通过蛋白质免疫印迹法分析了从喂食缺硒和补硒日粮的大鼠肝脏中获得的胞质部分。使用针对纯化的单个GST亚基（Ya、Yb和Yc）产生的抗血清来检测印迹上的相应亚基。在缺硒状态下，Ya亚基诱导增加了2.5倍。Yc亚基的量在硒缺乏时也显著增加（p小于0.05），但增加程度不如Ya亚基。Yb亚基不受硒营养状态改变的显著影响。通过Northern印迹分析也观察到编码Ya和Yc亚基的多聚腺苷酸RNA相应增加。从缺硒大鼠肝脏中分离出的纯化细胞核中，GST YaYc基因的转录活性提高了约2倍，这足以解释YaYc mRNA水平的增加。因此，似乎大鼠肝脏YaYc基因的转录激活是缺硒状态下相应基因产物升高的主要原因。由于GST，尤其是含有Ya亚基的同工酶，与前列腺素（PG）F2α的形成有关，我们使用GST的特异性抑制剂S-癸基谷胱甘肽研究了硒缺乏对PGF2α形成活性的影响。在喂食营养充足日粮的大鼠中，S-癸基谷胱甘肽抑制的活性至少占PGH2转化为PGF2α的一半。在硒缺乏期间，这种GST催化的活性增加了约一倍，而其他途径的PGF2α形成没有变化，导致PGF2α的总体合成增加了2倍。这些数据有力地支持了GST，尤其是由Ya大小亚基组成的GST，在PGH2合成PGF2α中的作用。
