Misra S, Zafarullah M, Price-Haughey J, Gedamu L
Department of Biological Sciences, University of Calgary, Victoria, Canada.
Biochim Biophys Acta. 1989 Apr 12;1007(3):325-33. doi: 10.1016/0167-4781(89)90155-3.
We have examined the effect of heavy metals on the expression of two major groups of stress-induced proteins in fish cell lines: the 70 kDa heat-shock proteins (hsp70) and metallothioneins (MTs). The rainbow trout hepatoma (RTH) cell line synthesized the hsp70 protein in response to zinc and heat shock, while chinook salmon embryonic (CHSE) cells synthesized this protein in response to these inducers, as well as cadmium. The synthesis of this 70 kDa protein was correlated with the accumulation of hsp70 mRNA as measured by hybridization to a trout hsp70 gene probe. Heavy metals also induced the synthesis of MT in RTH cells. However, heat shock did not result in induction of MT and its mRNA. Unlike RTH cells, CHSE cells did not synthesize MT following exposure to cadmium or zinc. When these cells were treated with 5-azacytidine prior to heavy metal treatment, accumulation of MT mRNA was observed. Northern blot analysis of total RNA from 5-azacytidine treated CHSE cells, using a trout MT (tMT-B) cDNA probe, indicated that the time-course of induction and the maximal level of MT mRNA accumulation in response to cadmium and zinc paralleled that observed in RTH cells. Copper and dexamethasone were ineffective in inducing MT mRNA in 5-azacytidine-treated CHSE cells. These results indicate that MT is specifically induced in response to heavy metal treatment, whereas the synthesis of hsp70 appears to be a general stress response. Furthermore, MT is differentially regulated by heavy metals and dexamethasone in these cell lines and the expression of MT is cell-type-specific.
70 kDa热休克蛋白（hsp70）和金属硫蛋白（MTs）。虹鳟肝癌（RTH）细胞系在锌和热休克刺激下合成hsp70蛋白，而奇努克鲑胚胎（CHSE）细胞在这些诱导剂以及镉的刺激下合成该蛋白。通过与鳟鱼hsp70基因探针杂交测量，这种70 kDa蛋白的合成与hsp70 mRNA的积累相关。重金属也诱导RTH细胞中MT的合成。然而，热休克并未导致MT及其mRNA的诱导。与RTH细胞不同，CHSE细胞在暴露于镉或锌后不合成MT。当这些细胞在重金属处理前用5-氮杂胞苷处理时，观察到MT mRNA的积累。使用鳟鱼MT（tMT-B）cDNA探针，对5-氮杂胞苷处理的CHSE细胞的总RNA进行Northern印迹分析，结果表明，镉和锌诱导MT mRNA的时间进程以及积累的最大水平与RTH细胞中观察到的情况相似。铜和地塞米松在5-氮杂胞苷处理的CHSE细胞中诱导MT mRNA无效。这些结果表明，MT是在重金属处理后特异性诱导的，而hsp70的合成似乎是一种普遍的应激反应。此外，在这些细胞系中，MT受重金属和地塞米松的差异调节，且MT的表达具有细胞类型特异性。
